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Effect of chewing gum on thirst: an integrative review

Efecto de la goma de mascar sobre la sed: revisión integrativa

ABSTRACT

Objective:

To identify and analyze the evidence on the effect of chewing gum on thirst in adults.

Method:

Integrative review, guided by the question: “What is the scientific evidence about the effects of chewing gum on adult’s thirst?” LILACS, PubMed, Scopus and Web of Science were the databases consulted.

Results:

Of a total of 2,414 articles found, 12 papers were selected whose publications varied between 1991 and 2016. The use of chewing gum resulted in increased salivary volume (five studies), xerostomia relief (seven studies), and thirst reduction (four studies). It was not possible to establish the number of chewing gums per day, being frequent the recommendation to use as desired. There was a predominance of studies with patients under dialysis and with cancer.

Conclusion:

Chewing gum is an effective strategy to reduce thirst discomfort in adults.

Descriptors:
Thirst; Salivation; Mastication; Chewing Gum; Xerostomia

RESUMEN

Objetivo:

Identificar y analizar las evidencias en cuanto al efecto de la goma de mascar sobre la sed en adultos.

Método:

Revisión integrativa, orientada por la cuestión: “¿Cuáles son las evidencias científicas acerca de los efectos de la goma de mascar sobre la sed en adultos?” Las bases de datos consultadas fueron: LILACS, PubMed, Scopus y Web of Science.

Resultados:

De un total de 2.414 artículos encontrados, se seleccionaron 12 trabajos cuyas publicaciones variaron entre los años 1991 y 2016. El uso de la goma de mascar resultó en el aumento del volumen salivar (cinco estudios), en el alivio de la xerostomía (siete estudios) y en la reducción de la sed (cuatro estudios). No fue posible establecer el número de gomas al día, siendo frecuente la recomendación de utilizarse según lo deseado. Hubo predominio de estudios con pacientes dialíticos y con pacientes con cáncer.

Conclusión:

La goma de mascar es una estrategia efectiva para reducir la molestia de la sed en adultos.

Descriptores:
Sed; Saliva; Masticación; Goma de Mascar; Xerostomia

RESUMO

Objetivo:

Identificar e analisar as evidências quanto ao efeito da goma de mascar sobre a sede em adultos.

Método:

Revisão integrativa, norteada pela questão: “Quais são as evidências científicas acerca dos efeitos da goma de mascar sobre a sede em adultos?” As bases de dados consultadas foram: LILACS, PubMed, Scopus e Web of Science.

Resultados:

De um total de 2.414 artigos encontrados, selecionaram-se 12 trabalhos cujas publicações variaram entre os anos de 1991 e 2016. O uso da goma de mascar resultou no aumento do volume salivar (cinco estudos), no alívio da xerostomia (sete estudos) e na redução da sede (quatro estudos). Não foi possível estabelecer o número de gomas por dia, sendo frequente a recomendação de utilizar-se conforme desejado. Houve predomínio de estudos com pacientes dialíticos e com pacientes oncológicos.

Conclusão:

A goma de mascar é uma estratégia efetiva para reduzir o desconforto da sede em adultos.

Descritores:
Sede; Saliva; Mastigação; Goma de Mascar; Xerostomia

INTRODUCTION

Thirst is a subjective sensation that can be defined as the desire to drink water and has identifiable signs that alter the physical, mental and social functioning of the patient(11 Silva LCJR, Aroni P, Fonseca LF. I am thirsty! Experience of the surgical patient in the perioperative period. Rev SOBECC. São Paulo; 2016;21(2):75-81. doi: http://dx.doi.org/10.5327/Z1414-4425201600020003
http://dx.doi.org/10.5327/Z1414-44252016...

2 Conchon MF, Nascimento LA, Fonseca LF, Aroni P. Perioperative thirst: an analysis from the perspective of the Symptom Management Theory. Rev Escola Enferm USP [Internet]. 2015[cited 2016 May 11];49(1):120-8. Available from: http://www.scielo.br/pdf/reeusp/v49n1/0080-6 234-reeusp-49-01-0122.pdf
http://www.scielo.br/pdf/reeusp/v49n1/00...
-33 Stevenson RJ, Mahmut M, Rooney K. Individual differences in the interoceptive states of hunger, fullness and thirst. Appetite. 2015;95:44-57. doi: http://dx.doi.org/10.1016/j.appet.2015.06.008
http://dx.doi.org/10.1016/j.appet.2015.0...
). A complex mechanism composed of osmo, baro, mecano and thermoreceptors signals the need for water intake to specific areas of the brain, triggering a subjective and uncomfortable sensation - thirst. The individual also presents peripheral signals that act as indicators of the need for fluid consumption, simultaneously with this central control process. Dry mouth, lips and throat, thick tongue and saliva, poor or bitter taste in the mouth and willingness to drink water, which exponentially increases the perception of discomfort generated by water deprivation, are among the peripheral signs or attributes of thirst(22 Conchon MF, Nascimento LA, Fonseca LF, Aroni P. Perioperative thirst: an analysis from the perspective of the Symptom Management Theory. Rev Escola Enferm USP [Internet]. 2015[cited 2016 May 11];49(1):120-8. Available from: http://www.scielo.br/pdf/reeusp/v49n1/0080-6 234-reeusp-49-01-0122.pdf
http://www.scielo.br/pdf/reeusp/v49n1/00...

3 Stevenson RJ, Mahmut M, Rooney K. Individual differences in the interoceptive states of hunger, fullness and thirst. Appetite. 2015;95:44-57. doi: http://dx.doi.org/10.1016/j.appet.2015.06.008
http://dx.doi.org/10.1016/j.appet.2015.0...

4 Gebremedhn EG, Nagaratnam VB. Audit on perioperative fasting of elective surgical patients in an African academic medical center. World J Surg. 2014;38(9):2200-4. Available from: https://www.ncbi.nlm.nih.gov/pubmed/24748347
https://www.ncbi.nlm.nih.gov/pubmed/2474...
-55 Martins PR, Fonseca LF, Rossetto EG, Mai LD. Developing and validating the Perioperative Thirst Discomfort Scale. Rev Esc Enferm USP. 2017;51,e03240. doi: http://dx.doi.org/10.1590/S1980-220X2016029003240
http://dx.doi.org/10.1590/S1980-220X2016...
).

Different factors may influence the presence of peripheral signs and thirst, including age, sex, food, habits, climate, drugs, anxiety, comorbidities and salivary dysfunctions(22 Conchon MF, Nascimento LA, Fonseca LF, Aroni P. Perioperative thirst: an analysis from the perspective of the Symptom Management Theory. Rev Escola Enferm USP [Internet]. 2015[cited 2016 May 11];49(1):120-8. Available from: http://www.scielo.br/pdf/reeusp/v49n1/0080-6 234-reeusp-49-01-0122.pdf
http://www.scielo.br/pdf/reeusp/v49n1/00...
-33 Stevenson RJ, Mahmut M, Rooney K. Individual differences in the interoceptive states of hunger, fullness and thirst. Appetite. 2015;95:44-57. doi: http://dx.doi.org/10.1016/j.appet.2015.06.008
http://dx.doi.org/10.1016/j.appet.2015.0...
,66 López-Pintor RM, López-Pintor L, Casañas E, de Arriba L, Hernández G. Risk factors associated with xerostomia in haemodialysis patients. Med Oral Patol Oral Cir Bucal [Internet]. 2017[cited 2018 Jan 25];22(2):185-92. Available from: https://www.ncbi.nlm.nih.gov/pubmed/28160594
https://www.ncbi.nlm.nih.gov/pubmed/2816...
-77 Saleh J, Figueiredo MA, Cherubini K, Salum FG. Salivary hypofunction: an update on a etiology, diagnosis and therapeutics. Arch Oral Biol [Internet]. 2015[cited 2018 Jan 25];60(2):242-55. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25463902
https://www.ncbi.nlm.nih.gov/pubmed/2546...
). Salivary dysfunctions can be divided into three aspects: hyposalivation (objective reduction of salivary flow); changes in salivary composition; and xerostomia (dry mouth discomfort, a subjective change)(77 Saleh J, Figueiredo MA, Cherubini K, Salum FG. Salivary hypofunction: an update on a etiology, diagnosis and therapeutics. Arch Oral Biol [Internet]. 2015[cited 2018 Jan 25];60(2):242-55. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25463902
https://www.ncbi.nlm.nih.gov/pubmed/2546...
-88 Oyakawa EHR, Contreras SJS. Salivary flow and level of comfort when using artificial saliva and candies of mint without sugar in elderly people with xerostomy. Rev Estomatol Herediana [Internet]. 2006[cited 2018 Jan 25];16(2):103-9. Available from: http://www.upch.edu.pe/vrinve/dugic/revistas/index.php/REH/article/view/1912
http://www.upch.edu.pe/vrinve/dugic/revi...
).

Saliva is a natural lubricant and is part of a state of comfort, gaining importance in its absence. Saliva is composed of more than 99% water along with electrolytes. Its protein components include immunoglobulins, digestive enzymes such as amylase and lipase, antibacterial and antifungal enzymes, as well as mucins(77 Saleh J, Figueiredo MA, Cherubini K, Salum FG. Salivary hypofunction: an update on a etiology, diagnosis and therapeutics. Arch Oral Biol [Internet]. 2015[cited 2018 Jan 25];60(2):242-55. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25463902
https://www.ncbi.nlm.nih.gov/pubmed/2546...
,99 Dawes C, Pedersen AML, Villa A, Ekstrom J, Proctor GB, Vissink A, et al. The functions of human saliva: a review sponsored by the World Workshop on Oral Medicine VI. Arch Oral Biol [Internet]. 2015[cited 2018 Jan 25];60:863-74. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25841068
https://www.ncbi.nlm.nih.gov/pubmed/2584...
-1010 Moura SAB, Medeiros AMC, Oliveira Filho AS, Costa FRH, Moraes PH. Diagnostic value of saliva in oral and systemic diseases: a literature review. Pesqui Bras Odonto Pediatr Clín Integr [Internet]. 2007[cited 2018 Jan 25];7(2):187-194. Available from: http://revista.uepb.edu.br/index.php/pboci/article/view/200
http://revista.uepb.edu.br/index.php/pbo...
).

Thus, hyposalivation interferes in the maintenance of general homeostasis, digestive function, taste perception, word articulation, cleaning, mouth and mucosa hydration, and the individual’s well-being(66 López-Pintor RM, López-Pintor L, Casañas E, de Arriba L, Hernández G. Risk factors associated with xerostomia in haemodialysis patients. Med Oral Patol Oral Cir Bucal [Internet]. 2017[cited 2018 Jan 25];22(2):185-92. Available from: https://www.ncbi.nlm.nih.gov/pubmed/28160594
https://www.ncbi.nlm.nih.gov/pubmed/2816...
-77 Saleh J, Figueiredo MA, Cherubini K, Salum FG. Salivary hypofunction: an update on a etiology, diagnosis and therapeutics. Arch Oral Biol [Internet]. 2015[cited 2018 Jan 25];60(2):242-55. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25463902
https://www.ncbi.nlm.nih.gov/pubmed/2546...
). Mastication is among the factors that influence salivary production. The unstimulated salivary mean flow is about 0.3 ml/min, while the stimulated one increases to 7 ml/min. 65% of the saliva is produced by the submandibular glands when at rest, having characteristic saliva rich in mucin, which provides lubrication to the mucosa. Under stimulation, the parotids represent 50% of the salivary volume, having as characteristic serous saliva(77 Saleh J, Figueiredo MA, Cherubini K, Salum FG. Salivary hypofunction: an update on a etiology, diagnosis and therapeutics. Arch Oral Biol [Internet]. 2015[cited 2018 Jan 25];60(2):242-55. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25463902
https://www.ncbi.nlm.nih.gov/pubmed/2546...
,1111 Dijkema T, Raaijmakers CPJ, Braam PM, Roesink JM, Monninkhof EM, Terhaard CHJ. Xerostomia: a day and night difference. Radiother Oncol [Internet]. 2012[cited 2018 Jan 25];104(2):219-23. Available from: http://www.thegreenjournal.com/article/S0167-8140(12)00265-4/abstract
http://www.thegreenjournal.com/article/S...
).

Because saliva is extremely important, strategies have been developed to reduce the discomfort of dry mouth - the main and most uncomfortable attribute linked to thirst. These strategies can be divided into stimulants and salivary substitutes.

Chewing gum is among the major salivary stimulants. Historians say that chewing gum consumption arose among the Indians of Guatemala, with the purpose of stimulating salivation, avoiding dry mouth during long walks(1212 Antunez MEM, Reis YB. Chewing gum in dentistry. Adolesc Saude [Internet]. 2012[cited 2018 Jan 25];9(4):58-62. Available from: http://adolescenciaesaude.com/detalhe_artigo.asp?id=346
http://adolescenciaesaude.com/detalhe_ar...
). The benefits of chewing gum are known mainly because they promote the increase of salivary pH and salivary flow through a combination of gustatory and mechanical stimulation(1313 Anderson LA, Orchardson R. The effect of chewing bicarbonate-containing gum on salivary flow rate and pH in humans. Arch Oral Biol [Internet]. 2003[cited 2018 Jan 25];48(3):201-4. Available from: https://www.ncbi.nlm.nih.gov/pubmed/12648557
https://www.ncbi.nlm.nih.gov/pubmed/1264...
), thus reducing the dryness of the mouth and the maladies that this symptom brings.

The benefits of chewing gum meet the needs of many thirsty individuals, including patients undergoing radiotherapy sessions for neck and head cancer treatment. Morphophysiological changes occur in the salivary glands during treatment, with xerostomia and hyposalivation being frequent complications resulting from radiotherapy(1414 Riley P, Glenny AM, Hua F, Worthington HV. Pharmacological interventions for preventing dry mouth and salivary gland dysfunction following radiotherapy. Cochrane Database Syst Rev. 2017;7:CD012744. doi: http://dx.doi.org/10.1002/14651858.CD012744
http://dx.doi.org/10.1002/14651858.CD012...
).

Thirst also influences poor compliance with the treatment of patients with chronic heart failure, as they are submitted to water restriction because of their clinical conditions, in addition to pharmacological interventions and emotional aspects(1515 Allida SM, Inglis SC, Davidson PM, Lal S, Hayward CS, Newton PJ. Thirst in chronic heart failure: a review. J Clin Nurs [Internet]. 2015[cited 2018 Jan 25];24(7-8):916-26. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25441537
https://www.ncbi.nlm.nih.gov/pubmed/2544...
).

Patients with chronic kidney disease, under dialysis therapy, present more intense thirst and xerostomia. Still, they need to maintain a water-restricted diet to avoid interdialytic weight gain and prevent comorbidities, such as hypertension, acute lung edema, and congestive heart failure(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
).

The reality of surgical patients in the preoperative period is no different. These patients are guided by professionals to remain in absolute fast, exceeding the time necessary for their safety(1818 Pavani MM, Fonseca LF, Conchon MF. Thirst in surgical patients: perceptions of the nursing team in inpatient units. Rev Enferm UFPE. 2016;10(9):3352-60. doi: http://dx.doi.org/10.5205/reuol.9571-83638-1-SM1009201621
http://dx.doi.org/10.5205/reuol.9571-836...
). Prolonged fasting is related to discomfort for the patient, including thirst.

Thus, the motivation for conducting this integrative review was the need to compile the available literature knowledge about the effects of chewing gum on the thirst, generating evidence for its implementation in clinical practice.

OBJECTIVE

This study aimed at identifying and analysing the evidence on the effect of chewing gum on thirst in adults.

METHOD

The method chosen to achieve the study objective was the integrative review. The steps covered were: elaboration of the research question, search in the literature of primary studies, extraction of data, evaluation of included primary studies, interpretation and systematization of results(1919 Mendes KDS, Silveira, RCCP, Galvão CM. Integrative literature review: a research method to incorporate evidence in health care and nursing. Texto Contexto Enferm [Internet]. 2008[cited 2018 Jan 25];17(4):758-64. Available from: http://www.redalyc.org/html/714/71411240017/
http://www.redalyc.org/html/714/71411240...
).

For the elaboration of the research question, we used the PICO strategy (acronym for patient, intervention, comparison, outcomes). The use of this strategy to formulate the research’s question in the conduction of revision methods allows the identification of keywords, which help in locating relevant primary studies in databases(2020 Fineout-Overholt E, Stillwell SB. Asking compelling, clinical questions. In: Melnyk BM, Fineout-Overholt E. Evidence-based practice in nursing & healthcare: a guide to best practice. Philadelphia: Wolters Kluwer, Lippincot Williams & Wilkins; 2011. p. 25-39.).

The guiding question of the integrative review was: “What is the scientific evidence about the effects of chewing gum on adult’s thirst?” The first element of the strategy (P) consists of adults; the second (I) consists of chewing gum; and the fourth element (O) consists of thirst. In this study, we did not use the third element (C) - the comparison.

The search for primary studies occurred from January to February 2017, in the following databases: National Library of Medicine (PubMed), Latin American and Caribbean Literature in Health Sciences (LILACS), Scopus and Web of Science (WOS).

We used the criteria and instructions of each database were used for the search. We used controlled descriptors (Medical Subject Headings - MeSH and Health Sciences Descriptors - DeCS) and the following uncontrolled descriptors (keywords): gum of chew, bubble gum, salivary flow, chewing gum, intervention, combined with Boolean operators (AND and OR). Cross references were performed according to Chart 1.

Chart 1
Cross references of descriptors in the databases, Brazil, 2017

The inclusion criteria established for the primary studies were articles that addressed the use of chewing gum on thirst. We excluded from the sample traditional literature reviews, secondary studies (systematic and integrative review), theses, dissertations, letter-response and editorials. There was no limitation of date or language due to the scarce scientific production on the subject.

Primary studies selection was independently performed by two reviewers, who read the titles and abstracts of the studies and selected them according to the eligibility criteria. In the event of disagreement, a third review was requested. We excluded articles that did not meet the inclusion criteria (n = 2,395) in the first selection, after reading the title and abstract of primary studies (n = 2,414). We found secondary articles, studies that addressed the effect of xylitol and sorbitol on oral health, caries, dental plaque, prevention of oral diseases, salivary tamponade, among other subjects that did not answer the research question. In the second selection, the duplicate studies in the databases (n = 4) were excluded by reading the articles selected in their entirety (n = 16). Thus, the final sample had 12 articles.

We used a tool prepared by nursing researchers for data extraction that consisted of items related to article identification, methodological characteristics, results, conclusion and evaluation of methodological rigor(2121 Ursi ES, Galvão CM. Perioperative prevention of skin injury: an integrative literature review. Rev Latino-Am Enfermagem [Internet]. 2006[cited 2018 Jan 25];14(1):124-31. Available from: http://www.scielo.br/pdf/rlae/v14n1/v14n1a17
http://www.scielo.br/pdf/rlae/v14n1/v14n...
).

Figure 1
Flow of the selection of the primary studies included in the integrative review according to the databases, Brazil, 2017

For the level of evidence, the definition of the type of study was maintained according to the authors of the surveys included in the sample. Levels of evidence ranged from 1 to 7, being: level 1 - meta-analysis or systematic reviews; level 2 - randomized controlled clinical trial; level 3 - clinical trial without randomization; level 4 - cohort and case-control studies; level 5 - systematic reviews of descriptive and qualitative studies; level 6 - descriptive or qualitative studies; and level 7 - expert opinion (1919 Mendes KDS, Silveira, RCCP, Galvão CM. Integrative literature review: a research method to incorporate evidence in health care and nursing. Texto Contexto Enferm [Internet]. 2008[cited 2018 Jan 25];17(4):758-64. Available from: http://www.redalyc.org/html/714/71411240017/
http://www.redalyc.org/html/714/71411240...
-2020 Fineout-Overholt E, Stillwell SB. Asking compelling, clinical questions. In: Melnyk BM, Fineout-Overholt E. Evidence-based practice in nursing & healthcare: a guide to best practice. Philadelphia: Wolters Kluwer, Lippincot Williams & Wilkins; 2011. p. 25-39.). The presentation of the results was done in a descriptive way.

RESULTS

Of the 12 selected primary studies, the years 1991, 1992, 1993, 1998, 2000, 2004, 2011 and 2016 presented only one publication per year; already in the years 2005 and 2013, two surveys were published per year. All studies were published in English and in international journals. It was identified that the authors of the studies belong to the field of dentistry (58.3%)(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2222 Bots CP, Brand HS, Veerman ECI, Van Amerongen BM, Nieuw Amerongen AV. Preferences and saliva stimulation of eight different chewing gums. Int Dental J [Internet]. 2004[cited 2018 Jan 25];54:143-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15218894
https://www.ncbi.nlm.nih.gov/pubmed/1521...

23 Stewart CM, Jones AC, Bates RE, Sandow P, Pink F, Stillwell J. Comparison between saliva stimulants and a saliva substitute in patients with xerostomia and hyposalivation. Spec Care Dentistry [Internet]. 1998[cited 2018 Jan 25];18(4):142-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10218061
https://www.ncbi.nlm.nih.gov/pubmed/1021...

24 Risheim H, Arneberg P. Salivary stimulation by chewing gum and lozenges in rheumatic patients with xerostomia. Scand J Dent Res [Internet]. 1993[cited 2018 Jan 25];101:40-3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8441894
https://www.ncbi.nlm.nih.gov/pubmed/8441...

25 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...
-2626 Olsson H, Spak CJ, Axéll T. The effect of a chewing gum on salivary secretion, oral mucosal friction, and the feeling of dry mouth in xerostomic patients. Acta Odontol Scandin [Internet]. 1991[cited 2018 Jan 25];49(5):273-9. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1803848
https://www.ncbi.nlm.nih.gov/pubmed/1803...
), medicine (33.3%)(2727 Kaae JK, Stenfeldt L, Eriksen JG. Xerostomia after radiotherapy for oral and oropharyngeal cancer: increasing salivary flow with tasteless sugar-free chewing gum. Frontiers In Oncology [Internet]. 2016[cited 2018 Jan 25];6:111. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4853382/
https://www.ncbi.nlm.nih.gov/pmc/article...

28 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...

29 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...
-3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
) and nursing (8,3%)(3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
).

Regarding the place of studies, 3 (25%) were conducted in the Netherlands by the same group of researchers. Two articles selected for the sample presented results from two different surveys each. The methods covered in the studies were randomized clinical trials (71.4%); cohort study (7.1%); observational study (7.1%); quasi-experimental study (7.1%); pre/post-test study (7.1%). Therefore, level 2 is the scientific evidence for most studies (71.4%)(1919 Mendes KDS, Silveira, RCCP, Galvão CM. Integrative literature review: a research method to incorporate evidence in health care and nursing. Texto Contexto Enferm [Internet]. 2008[cited 2018 Jan 25];17(4):758-64. Available from: http://www.redalyc.org/html/714/71411240017/
http://www.redalyc.org/html/714/71411240...
-2020 Fineout-Overholt E, Stillwell SB. Asking compelling, clinical questions. In: Melnyk BM, Fineout-Overholt E. Evidence-based practice in nursing & healthcare: a guide to best practice. Philadelphia: Wolters Kluwer, Lippincot Williams & Wilkins; 2011. p. 25-39.).

Five studies were performed with patients under dialysis(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
-2929 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
), two with patients(2727 Kaae JK, Stenfeldt L, Eriksen JG. Xerostomia after radiotherapy for oral and oropharyngeal cancer: increasing salivary flow with tasteless sugar-free chewing gum. Frontiers In Oncology [Internet]. 2016[cited 2018 Jan 25];6:111. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4853382/
https://www.ncbi.nlm.nih.gov/pmc/article...
,3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
), and one study for each of the following: low salivary flow(2323 Stewart CM, Jones AC, Bates RE, Sandow P, Pink F, Stillwell J. Comparison between saliva stimulants and a saliva substitute in patients with xerostomia and hyposalivation. Spec Care Dentistry [Internet]. 1998[cited 2018 Jan 25];18(4):142-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10218061
https://www.ncbi.nlm.nih.gov/pubmed/1021...
), chronic xerostomia(2525 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...
-2626 Olsson H, Spak CJ, Axéll T. The effect of a chewing gum on salivary secretion, oral mucosal friction, and the feeling of dry mouth in xerostomic patients. Acta Odontol Scandin [Internet]. 1991[cited 2018 Jan 25];49(5):273-9. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1803848
https://www.ncbi.nlm.nih.gov/pubmed/1803...
, rheumatic(2424 Risheim H, Arneberg P. Salivary stimulation by chewing gum and lozenges in rheumatic patients with xerostomia. Scand J Dent Res [Internet]. 1993[cited 2018 Jan 25];101:40-3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8441894
https://www.ncbi.nlm.nih.gov/pubmed/8441...
), healthy and sick individuals(2222 Bots CP, Brand HS, Veerman ECI, Van Amerongen BM, Nieuw Amerongen AV. Preferences and saliva stimulation of eight different chewing gums. Int Dental J [Internet]. 2004[cited 2018 Jan 25];54:143-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15218894
https://www.ncbi.nlm.nih.gov/pubmed/1521...
).

Sugar-free chewing gums(2727 Kaae JK, Stenfeldt L, Eriksen JG. Xerostomia after radiotherapy for oral and oropharyngeal cancer: increasing salivary flow with tasteless sugar-free chewing gum. Frontiers In Oncology [Internet]. 2016[cited 2018 Jan 25];6:111. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4853382/
https://www.ncbi.nlm.nih.gov/pmc/article...
,3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
-3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
), with sorbitol and/or xylitol(2323 Stewart CM, Jones AC, Bates RE, Sandow P, Pink F, Stillwell J. Comparison between saliva stimulants and a saliva substitute in patients with xerostomia and hyposalivation. Spec Care Dentistry [Internet]. 1998[cited 2018 Jan 25];18(4):142-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10218061
https://www.ncbi.nlm.nih.gov/pubmed/1021...
-2424 Risheim H, Arneberg P. Salivary stimulation by chewing gum and lozenges in rheumatic patients with xerostomia. Scand J Dent Res [Internet]. 1993[cited 2018 Jan 25];101:40-3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8441894
https://www.ncbi.nlm.nih.gov/pubmed/8441...
,2626 Olsson H, Spak CJ, Axéll T. The effect of a chewing gum on salivary secretion, oral mucosal friction, and the feeling of dry mouth in xerostomic patients. Acta Odontol Scandin [Internet]. 1991[cited 2018 Jan 25];49(5):273-9. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1803848
https://www.ncbi.nlm.nih.gov/pubmed/1803...
), sweetened(2929 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...
). In three studies the type of chewing gum was not specified(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
) and in two, chewing gum of different types(2222 Bots CP, Brand HS, Veerman ECI, Van Amerongen BM, Nieuw Amerongen AV. Preferences and saliva stimulation of eight different chewing gums. Int Dental J [Internet]. 2004[cited 2018 Jan 25];54:143-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15218894
https://www.ncbi.nlm.nih.gov/pubmed/1521...
,2525 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...
).

In eight studies(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2323 Stewart CM, Jones AC, Bates RE, Sandow P, Pink F, Stillwell J. Comparison between saliva stimulants and a saliva substitute in patients with xerostomia and hyposalivation. Spec Care Dentistry [Internet]. 1998[cited 2018 Jan 25];18(4):142-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10218061
https://www.ncbi.nlm.nih.gov/pubmed/1021...

24 Risheim H, Arneberg P. Salivary stimulation by chewing gum and lozenges in rheumatic patients with xerostomia. Scand J Dent Res [Internet]. 1993[cited 2018 Jan 25];101:40-3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8441894
https://www.ncbi.nlm.nih.gov/pubmed/8441...
-2525 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...
,2727 Kaae JK, Stenfeldt L, Eriksen JG. Xerostomia after radiotherapy for oral and oropharyngeal cancer: increasing salivary flow with tasteless sugar-free chewing gum. Frontiers In Oncology [Internet]. 2016[cited 2018 Jan 25];6:111. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4853382/
https://www.ncbi.nlm.nih.gov/pmc/article...
-2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
), chewing gum was used by patients for two weeks. The use of gum was for five days in one study(3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
) and three months in another(2929 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...
). In 2 studies, outcomes were assessed on the same day, during the use of chewing gum for 10 minutes(2222 Bots CP, Brand HS, Veerman ECI, Van Amerongen BM, Nieuw Amerongen AV. Preferences and saliva stimulation of eight different chewing gums. Int Dental J [Internet]. 2004[cited 2018 Jan 25];54:143-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15218894
https://www.ncbi.nlm.nih.gov/pubmed/1521...
) or for 35 minutes(2626 Olsson H, Spak CJ, Axéll T. The effect of a chewing gum on salivary secretion, oral mucosal friction, and the feeling of dry mouth in xerostomic patients. Acta Odontol Scandin [Internet]. 1991[cited 2018 Jan 25];49(5):273-9. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1803848
https://www.ncbi.nlm.nih.gov/pubmed/1803...
). The recommendation of the number of gums per day ranged from at least(2525 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...
), once a day to six times a day(1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
), with the recommendation to use the chewing gum frequently as desired(1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...

29 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...

30 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
-3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
).

Regarding the effect of the use of chewing gum, in seven studies(2222 Bots CP, Brand HS, Veerman ECI, Van Amerongen BM, Nieuw Amerongen AV. Preferences and saliva stimulation of eight different chewing gums. Int Dental J [Internet]. 2004[cited 2018 Jan 25];54:143-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15218894
https://www.ncbi.nlm.nih.gov/pubmed/1521...

23 Stewart CM, Jones AC, Bates RE, Sandow P, Pink F, Stillwell J. Comparison between saliva stimulants and a saliva substitute in patients with xerostomia and hyposalivation. Spec Care Dentistry [Internet]. 1998[cited 2018 Jan 25];18(4):142-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10218061
https://www.ncbi.nlm.nih.gov/pubmed/1021...

24 Risheim H, Arneberg P. Salivary stimulation by chewing gum and lozenges in rheumatic patients with xerostomia. Scand J Dent Res [Internet]. 1993[cited 2018 Jan 25];101:40-3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8441894
https://www.ncbi.nlm.nih.gov/pubmed/8441...

25 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...

26 Olsson H, Spak CJ, Axéll T. The effect of a chewing gum on salivary secretion, oral mucosal friction, and the feeling of dry mouth in xerostomic patients. Acta Odontol Scandin [Internet]. 1991[cited 2018 Jan 25];49(5):273-9. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1803848
https://www.ncbi.nlm.nih.gov/pubmed/1803...
-2727 Kaae JK, Stenfeldt L, Eriksen JG. Xerostomia after radiotherapy for oral and oropharyngeal cancer: increasing salivary flow with tasteless sugar-free chewing gum. Frontiers In Oncology [Internet]. 2016[cited 2018 Jan 25];6:111. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4853382/
https://www.ncbi.nlm.nih.gov/pmc/article...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
) the outcome was salivary flow. In six of these studies, there was an increase in salivary flow after the use of chewing gum(2222 Bots CP, Brand HS, Veerman ECI, Van Amerongen BM, Nieuw Amerongen AV. Preferences and saliva stimulation of eight different chewing gums. Int Dental J [Internet]. 2004[cited 2018 Jan 25];54:143-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15218894
https://www.ncbi.nlm.nih.gov/pubmed/1521...
,2424 Risheim H, Arneberg P. Salivary stimulation by chewing gum and lozenges in rheumatic patients with xerostomia. Scand J Dent Res [Internet]. 1993[cited 2018 Jan 25];101:40-3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8441894
https://www.ncbi.nlm.nih.gov/pubmed/8441...

25 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...

26 Olsson H, Spak CJ, Axéll T. The effect of a chewing gum on salivary secretion, oral mucosal friction, and the feeling of dry mouth in xerostomic patients. Acta Odontol Scandin [Internet]. 1991[cited 2018 Jan 25];49(5):273-9. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1803848
https://www.ncbi.nlm.nih.gov/pubmed/1803...
-2727 Kaae JK, Stenfeldt L, Eriksen JG. Xerostomia after radiotherapy for oral and oropharyngeal cancer: increasing salivary flow with tasteless sugar-free chewing gum. Frontiers In Oncology [Internet]. 2016[cited 2018 Jan 25];6:111. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4853382/
https://www.ncbi.nlm.nih.gov/pmc/article...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
).

Xerostomia was the outcome evaluated in nine studies(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2323 Stewart CM, Jones AC, Bates RE, Sandow P, Pink F, Stillwell J. Comparison between saliva stimulants and a saliva substitute in patients with xerostomia and hyposalivation. Spec Care Dentistry [Internet]. 1998[cited 2018 Jan 25];18(4):142-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10218061
https://www.ncbi.nlm.nih.gov/pubmed/1021...

24 Risheim H, Arneberg P. Salivary stimulation by chewing gum and lozenges in rheumatic patients with xerostomia. Scand J Dent Res [Internet]. 1993[cited 2018 Jan 25];101:40-3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8441894
https://www.ncbi.nlm.nih.gov/pubmed/8441...
-2525 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...

29 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...

30 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
-3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
), with the Xerostomia Inventory(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...

29 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...

30 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
-3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
) and the Visual Analogue Scale(1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2424 Risheim H, Arneberg P. Salivary stimulation by chewing gum and lozenges in rheumatic patients with xerostomia. Scand J Dent Res [Internet]. 1993[cited 2018 Jan 25];101:40-3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8441894
https://www.ncbi.nlm.nih.gov/pubmed/8441...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
,3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
) the tools often used. In seven studies, chewing gum resulted in xerostomia relief(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2323 Stewart CM, Jones AC, Bates RE, Sandow P, Pink F, Stillwell J. Comparison between saliva stimulants and a saliva substitute in patients with xerostomia and hyposalivation. Spec Care Dentistry [Internet]. 1998[cited 2018 Jan 25];18(4):142-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10218061
https://www.ncbi.nlm.nih.gov/pubmed/1021...
,2525 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
,3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
-3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
).

Thirst was the outcome evaluated in five studies((1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
-2929 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
) through the Dialytic Thirst Inventory (DTI)(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
), Visual Analogue Scale(1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
) and Xerostomia and Thirst Questionnaire(2929 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...
). Thirst relief after the use of chewing gum was reported in four studies(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
).

The weight gain between hemodialysis sessions was the outcome evaluated in four studies(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
-2929 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
); and in two of these studies the use of chewing gum resulted in decreased weight gain(2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
).

In Chart 2, the main information extracted from the primary studies included in the review.

Chart 2
Synthesis of the primary studies included in the integrative review (n = 12); Brazil, 2017

DISCUSSION

The relevance of this study is in the compilation of knowledge about the theme “thirst and its discomforts” in different populations, helping clinical practice, based on evidence, so that health professionals can implement thirst relief strategies and their discomforts to their customers. The discussion was organized into four categories: Effects of chewing gum; Tools used to assess outcomes; Types and amount of chewing gum; Populations studied.

Category 1 - Effects of chewing gum

We found 12 studies on the effect of chewing gum on thirst in adults. The effects of chewing gum were: increased salivary flow (five studies)(2222 Bots CP, Brand HS, Veerman ECI, Van Amerongen BM, Nieuw Amerongen AV. Preferences and saliva stimulation of eight different chewing gums. Int Dental J [Internet]. 2004[cited 2018 Jan 25];54:143-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15218894
https://www.ncbi.nlm.nih.gov/pubmed/1521...
,2525 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...

26 Olsson H, Spak CJ, Axéll T. The effect of a chewing gum on salivary secretion, oral mucosal friction, and the feeling of dry mouth in xerostomic patients. Acta Odontol Scandin [Internet]. 1991[cited 2018 Jan 25];49(5):273-9. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1803848
https://www.ncbi.nlm.nih.gov/pubmed/1803...
-2727 Kaae JK, Stenfeldt L, Eriksen JG. Xerostomia after radiotherapy for oral and oropharyngeal cancer: increasing salivary flow with tasteless sugar-free chewing gum. Frontiers In Oncology [Internet]. 2016[cited 2018 Jan 25];6:111. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4853382/
https://www.ncbi.nlm.nih.gov/pmc/article...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
), xerostomia relief (seven studies)(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2323 Stewart CM, Jones AC, Bates RE, Sandow P, Pink F, Stillwell J. Comparison between saliva stimulants and a saliva substitute in patients with xerostomia and hyposalivation. Spec Care Dentistry [Internet]. 1998[cited 2018 Jan 25];18(4):142-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10218061
https://www.ncbi.nlm.nih.gov/pubmed/1021...
,2525 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
,3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
-3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
) and thirst reduction (four studies)(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
).

The effect of chewing gum on increasing salivary flow is an important result for patients with water restriction. In these patients, there is an exponential increase in the discomfort caused by thirst caused by generalized dehydration of the oropharyngeal mucosa(33 Stevenson RJ, Mahmut M, Rooney K. Individual differences in the interoceptive states of hunger, fullness and thirst. Appetite. 2015;95:44-57. doi: http://dx.doi.org/10.1016/j.appet.2015.06.008
http://dx.doi.org/10.1016/j.appet.2015.0...
,3232 Zimmerman CA, Leib DE, Knight ZA. Neural circuits underlying thirst and fluid homeostasis. Macmillan Publishers Limited, part of Springer Nature. All rights reserved. 2017. doi: http://dx.doi.org/10.1038/nrn.2017.71.
http://dx.doi.org/10.1038/nrn.2017.71...
-3333 Zimmerman, CA, Lin YC, Leib DE, Guo L, Huey EL, Daly GE, et al. Thirst neurons anticipate the homeostatic consequences of eating and drinking. Macmillan Publishers Limited, part of Springer Nature. All rights reserved. 2016. doi: http://dx.doi.org/10.1038/nature18950.
http://dx.doi.org/10.1038/nature18950...
).

Thus, xerostomia relief is a relevant effect to reduce discomfort, since it is identified as the most prevalent signal in the presence of thirst(33 Stevenson RJ, Mahmut M, Rooney K. Individual differences in the interoceptive states of hunger, fullness and thirst. Appetite. 2015;95:44-57. doi: http://dx.doi.org/10.1016/j.appet.2015.06.008
http://dx.doi.org/10.1016/j.appet.2015.0...
,3434 Leiper J. Thirst. In: Caballero B, Allen L, Prentice A. Encyclopedia of human nutrition. 2nd ed. University of Aberdeen, UK: Elsevier Academic Press, 2005. p. 278-86.). It can be caused by decreased salivary flow, atrophy and fibrosis of the salivary glands, use of drugs and restriction of fluid intake(3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
).

A study carried out with surgical patients, which aimed to explore their perception regarding thirst in the perioperative period, pointed out that dry mouth was the first and most prevalent attribute remembered by patients. In the preoperative period, patients used subterfuge to relieve it, such as ingesting more water than allowed to take tablets, resorting to sleep, avoiding fasting, performing oral hygiene and gargling in an attempt to moisten the oral cavity, thus relieving the discomfort(11 Silva LCJR, Aroni P, Fonseca LF. I am thirsty! Experience of the surgical patient in the perioperative period. Rev SOBECC. São Paulo; 2016;21(2):75-81. doi: http://dx.doi.org/10.5327/Z1414-4425201600020003
http://dx.doi.org/10.5327/Z1414-44252016...
).

The effect of chewing gum on thirst reduction occurred in four of the five studies that evaluated this outcome. Dehydration of the oral cavity is closely related to thirst, since there are receptors in the oropharyngeal region that are capable of modulating it. These receptors act by emitting excitatory and inhibitory signals for the water intake behavior, depending on the hydration of the oral cavity(3232 Zimmerman CA, Leib DE, Knight ZA. Neural circuits underlying thirst and fluid homeostasis. Macmillan Publishers Limited, part of Springer Nature. All rights reserved. 2017. doi: http://dx.doi.org/10.1038/nrn.2017.71.
http://dx.doi.org/10.1038/nrn.2017.71...
).

Category 2 - Tools used to assess outcomes

In the evaluation of outcomes, the Xerostomia Inventory was used in six studies(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...

29 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...

30 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
-3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
). The Xerostomia Inventory is a scale of 11 items, each item having a scale ranging from “never” (1) to “very frequently” (5). Scale scores ranged from 11 to 55, in which higher scores indicated greater severity of xerostomia. The Xerostomia Inventory was developed in Australia(3535 Thomson WM, Chalmers JM, Spencer AJ, Williams SM. The Xerostomia Inventory: a multi-item approach to measuring dry mouth. Community Dent Health [Internet]. 1999 [cited 2018 Jan 25];16(1):12-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10697349
https://www.ncbi.nlm.nih.gov/pubmed/1069...
) and translated and validated into Portuguese(3636 Mata AD, Marques DNS, Freitas FM, Amaral JPLR, Trindade RT, Barcelos FA, et al. Translation, validation, and construct reliability of a Portuguese version of the Xerostomia Inventory. Oral Dis. 2012 Apr;18(3):293-8. doi: http://dx.doi.org/10.1111/j.1601-0825.2011.01879.x
http://dx.doi.org/10.1111/j.1601-0825.20...
) and Spanish(3737 Serrano C, Fariña MP, Pérez C, Fernández M, Forman K, Carrasco M. Translation and validation of a Spanish version of the xerostomia inventory. Gerodontology. 2016 Dec;33(4):506-512. doi: http://dx.doi.org/10.1111/ger.12196
http://dx.doi.org/10.1111/ger.12196...
). A reduced version of the tool, containing five items and three response options, proved to be valid and reliable(3838 Thomson WM, van der Putten GJ, Baat C, Ikebe K, Matsuda K, Enoki K, et al. Shortening the xerostomia inventory. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2011 Sep;112(3):322-7. doi: http://dx.doi.org/10.1016/j.tripleo.2011.03.024
http://dx.doi.org/10.1016/j.tripleo.2011...
).

In the thirst evaluation, the Dialytic Thirst Inventory (DTI) was used in three studies(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
). DTI is a specific tool for use in patients under dialysis. No studies on the construction, validation and translation of the tool were found. Chronbach’s alpha value of the DTI was 0.87(3939 Bots CP, Brand HS, Veerman ECI, Valentiyn-Benz M, van Amerongen BM, Valentiyn RM, et al. Interdialytic weight gain in patients on hemodialysis is associated with dry mouth and thirst. Kidney Int [Internet]. 2004[cited 2016 May 02];66(4):1662-8. Available from: http://www.sciencedirect.com/science/article/pii/S008525381550238X
http://www.sciencedirect.com/science/art...
), and there was a significant correlation between the site evaluated by the DTI and the site evaluated by Visual Analogue Scale, as well as xerostomia(2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
).

We highlight the use of Visual Analogue Scale to evaluate xerostomia(1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2424 Risheim H, Arneberg P. Salivary stimulation by chewing gum and lozenges in rheumatic patients with xerostomia. Scand J Dent Res [Internet]. 1993[cited 2018 Jan 25];101:40-3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8441894
https://www.ncbi.nlm.nih.gov/pubmed/8441...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
,3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
) and thirst(1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
), which may indicate the scarcity of tools to evaluate these outcomes.

Although widely used, the Visual Analogue Scale has limitations. To assess pain, it was verified that the Visual Analogue Scale does not have a linear behavior and that the average of the standardized response varies over time. Thus, the evaluation of change over time is not valid, and may underestimate or overestimate the true change(4040 Kersten P, White PJ, Tennant A. Is the pain visual analogue scale linear and responsive to change? an exploration using Rasch analysis. PLoS One. 2014;9(6):e99485. doi: http://dx.doi.org/ 10.1371/journal.pone.0099485
http://dx.doi.org/ 10.1371/journal.pone....
). However, this scale has been used extensively in the subjective evaluation of the home, and studies with a high level of evidence indicate a strong and positive correlation between the Visual Analogue Scale and the increase in serum osmolarity(4141 Arai SR, Butzlaff A, Stotts NA, Puntillo KA. Quench the thirst: lessons from clinical thirst trials. Biol Res Nurs. 2013; 00(0):1-11. doi: http://dx.doi.org/10.1177/1099800413505900
http://dx.doi.org/10.1177/10998004135059...
-4242 Conchon MF, Fonseca LF. Efficacy of an ice Popsicle on thirst management in the immediate postoperative period: a randomized clinical trial. J Peri Anesthesia Nurs. 2016:1-9. doi: http://dx.doi.org/10.1016/j.jopan.2016.03.009
http://dx.doi.org/10.1016/j.jopan.2016.0...
).

Category 3 - Types and amount of chewing gum

Regarding the type of chewing gum, in one study it was verified that chewing gums of different types also stimulated the salivary flow(2222 Bots CP, Brand HS, Veerman ECI, Van Amerongen BM, Nieuw Amerongen AV. Preferences and saliva stimulation of eight different chewing gums. Int Dental J [Internet]. 2004[cited 2018 Jan 25];54:143-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15218894
https://www.ncbi.nlm.nih.gov/pubmed/1521...
). In another study, however, it was found that chewing gum with long duration of flavor provided an increase in salivary flow(2626 Olsson H, Spak CJ, Axéll T. The effect of a chewing gum on salivary secretion, oral mucosal friction, and the feeling of dry mouth in xerostomic patients. Acta Odontol Scandin [Internet]. 1991[cited 2018 Jan 25];49(5):273-9. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1803848
https://www.ncbi.nlm.nih.gov/pubmed/1803...
).

Considering the taste, there is evidence that flavored chewing gums have a higher salivary production than taste-free chewing gums. This is because 85% of salivary flow is related to gustatory stimulation (activation of chemoreceptors) and only 15%, with mechanical stimulation (activation of mechanoreceptors)(88 Oyakawa EHR, Contreras SJS. Salivary flow and level of comfort when using artificial saliva and candies of mint without sugar in elderly people with xerostomy. Rev Estomatol Herediana [Internet]. 2006[cited 2018 Jan 25];16(2):103-9. Available from: http://www.upch.edu.pe/vrinve/dugic/revistas/index.php/REH/article/view/1912
http://www.upch.edu.pe/vrinve/dugic/revi...
).

Studies have shown that chewing gum is more effective in alleviating xerostomia because it activates the parasympathetic system and induces more fluid salivary secretion(3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
). This may be one of the reasons for the preference for flavored strategies when compared to paraffin or flavorless chewing gum, or even flavoring gums for a shorter period(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2222 Bots CP, Brand HS, Veerman ECI, Van Amerongen BM, Nieuw Amerongen AV. Preferences and saliva stimulation of eight different chewing gums. Int Dental J [Internet]. 2004[cited 2018 Jan 25];54:143-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15218894
https://www.ncbi.nlm.nih.gov/pubmed/1521...
,2525 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...
-2626 Olsson H, Spak CJ, Axéll T. The effect of a chewing gum on salivary secretion, oral mucosal friction, and the feeling of dry mouth in xerostomic patients. Acta Odontol Scandin [Internet]. 1991[cited 2018 Jan 25];49(5):273-9. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1803848
https://www.ncbi.nlm.nih.gov/pubmed/1803...
,3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
).

As for frequency of use, chewing gum was effective in the momentary use(2222 Bots CP, Brand HS, Veerman ECI, Van Amerongen BM, Nieuw Amerongen AV. Preferences and saliva stimulation of eight different chewing gums. Int Dental J [Internet]. 2004[cited 2018 Jan 25];54:143-8. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15218894
https://www.ncbi.nlm.nih.gov/pubmed/1521...

23 Stewart CM, Jones AC, Bates RE, Sandow P, Pink F, Stillwell J. Comparison between saliva stimulants and a saliva substitute in patients with xerostomia and hyposalivation. Spec Care Dentistry [Internet]. 1998[cited 2018 Jan 25];18(4):142-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10218061
https://www.ncbi.nlm.nih.gov/pubmed/1021...

24 Risheim H, Arneberg P. Salivary stimulation by chewing gum and lozenges in rheumatic patients with xerostomia. Scand J Dent Res [Internet]. 1993[cited 2018 Jan 25];101:40-3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8441894
https://www.ncbi.nlm.nih.gov/pubmed/8441...

25 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...
-2626 Olsson H, Spak CJ, Axéll T. The effect of a chewing gum on salivary secretion, oral mucosal friction, and the feeling of dry mouth in xerostomic patients. Acta Odontol Scandin [Internet]. 1991[cited 2018 Jan 25];49(5):273-9. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1803848
https://www.ncbi.nlm.nih.gov/pubmed/1803...
), for five days(3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
) and for two weeks(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2323 Stewart CM, Jones AC, Bates RE, Sandow P, Pink F, Stillwell J. Comparison between saliva stimulants and a saliva substitute in patients with xerostomia and hyposalivation. Spec Care Dentistry [Internet]. 1998[cited 2018 Jan 25];18(4):142-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10218061
https://www.ncbi.nlm.nih.gov/pubmed/1021...

24 Risheim H, Arneberg P. Salivary stimulation by chewing gum and lozenges in rheumatic patients with xerostomia. Scand J Dent Res [Internet]. 1993[cited 2018 Jan 25];101:40-3. Available from: https://www.ncbi.nlm.nih.gov/pubmed/8441894
https://www.ncbi.nlm.nih.gov/pubmed/8441...
-2525 Aagaard A, Godiksenn S, Teglers PT, Schiodt M, Glenert U. Comparison between new saliva stimulants in patients with dry mouth: a placebo-controlled double-blind crossover study. J Oral Pathol Med [Internet]. 1992[cited 2018 Jan 25];21:376-80. Available from: https://www.ncbi.nlm.nih.gov/pubmed/1403845
https://www.ncbi.nlm.nih.gov/pubmed/1403...
,2727 Kaae JK, Stenfeldt L, Eriksen JG. Xerostomia after radiotherapy for oral and oropharyngeal cancer: increasing salivary flow with tasteless sugar-free chewing gum. Frontiers In Oncology [Internet]. 2016[cited 2018 Jan 25];6:111. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4853382/
https://www.ncbi.nlm.nih.gov/pmc/article...
-2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
); however, in use for three months, there were no changes in outcomes(2929 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...
). Thus, more studies are needed to evaluate the long-term benefits of chewing gum use.

It was not possible to establish the number of gums per day due to the heterogeneity of the studies. The recommendation is to use the gum as desired by the patient. Thus, in the presence of xerostomia or thirst, its frequency must be determined by the patient himself.

Category 4 - Populations studied

Patients of various specialties are exposed to risk factors for developing. The present study evidenced that research for the management of thirst in some areas has intensified, as is the case of patients undergoing dialysis(1616 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
,2828 Fan WF, Zhang Q, Luo LH, Niu JY, Gu Y. Study on the clinical significance and related factors on thirst and xerostomia in maintenance hemodialysis patients. Kidney Blood Press Res [Internet]. 2013[cited 2016 Apr 12];37(4-5):464-74. Available from: http://www.karger.com/Article/Pdf/355717
http://www.karger.com/Article/Pdf/355717...
-2929 Jagodzińska M, Zimmer-Nowicka J, Nowicki M. Three months of regular gum chewing neither alleviates xerostomia nor reduces over hydration in chronic hemodialysis patients. journal of renal nutrition [Internet]. 2011[cited 2018 Jan 25];21(5):410-7. Available from: https://www.ncbi.nlm.nih.gov/pubmed/21185739
https://www.ncbi.nlm.nih.gov/pubmed/2118...
,3131 Said H, Mohammed H. Effect of chewing gum on xerostomia, thirst and interdialytic weight gain in patients on hemodialysis. Life Sci J [Internet]. 2013[cited 2018 Jan 25];10(2):1767-77. Available from: http://www.lifesciencesite.com
http://www.lifesciencesite.com...
) or who suffer from xerostomia due to radiotherapy sessions due to advanced-stage head and neck cancer(2727 Kaae JK, Stenfeldt L, Eriksen JG. Xerostomia after radiotherapy for oral and oropharyngeal cancer: increasing salivary flow with tasteless sugar-free chewing gum. Frontiers In Oncology [Internet]. 2016[cited 2018 Jan 25];6:111. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4853382/
https://www.ncbi.nlm.nih.gov/pmc/article...
,3030 Davies AN. A comparison of artificial saliva and chewing gum in the management of xerostomia in patients with advanced cancer. Palliat Medicine [Internet]. 2000[cited 2018 Jan 25];14(3):197-203. Available from: https://www.ncbi.nlm.nih.gov/pubmed/10858827
https://www.ncbi.nlm.nih.gov/pubmed/1085...
). However, little is known and studied about the thirst of patients in other hospital settings, such as surgical patients, who live daily with high intensity thirst.

The myth that the use of chewing gum is contraindicated throughout the preoperative fasting period has been widely practiced in clinical practice, including the suspension of surgical procedures. However, there is evidence of level 1, obtained by meta-analysis, which argue that chewing gum does not change volume and gastric acidity clinically significant for bronchoaspiration(4343 Quanes JP, Bicket MC, Togioka B, Tomas VG, Wu CL, Murphy JM. The role of perioperative chewing gum on gastric fluid volume and gastric ph: a meta-analysis. J Clin Anesthesia. 2015;27(2):146-52. doi: http://dx.doi.org/10.1016/j.jclinane.2014.07.005
http://dx.doi.org/10.1016/j.jclinane.201...
). Thus, it is necessary to intensify efforts for the development of researches with methodologies capable of producing strong evidences regarding the benefits and safety of the use of chewing gum for this population.

The use of chewing gum increases salivary flow, triggers oral lubrication, which acts against dehydration of the oral mucosa and can therefore effectively relieve thirst and its discomforts(1515 Allida SM, Inglis SC, Davidson PM, Lal S, Hayward CS, Newton PJ. Thirst in chronic heart failure: a review. J Clin Nurs [Internet]. 2015[cited 2018 Jan 25];24(7-8):916-26. Available from: https://www.ncbi.nlm.nih.gov/pubmed/25441537
https://www.ncbi.nlm.nih.gov/pubmed/2544...

16 Bots CP, Brand HS, Veerman EC, Korevaar JC, Valentijn Benz M, Bezemer PD, et al. Chewing gum and a saliva substitute alleviate thirst and xerostomia in patients on haemodialysis. Nephrol Dial Transplant [Internet]. 2005[cited 2016 May 10];20(3):578-84. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15665029
https://www.ncbi.nlm.nih.gov/pubmed/1566...
-1717 Bots CP, Brand HS, Veerman EC, Valentijn-Benz M, Van Amerongen BM, Nieuw Amerongen AVN, et al. The management of xerostomia in patients on haemodialysis: comparison of artificial saliva and chewing gum. Palliative Medicine [Internet]. 2005[cited 2018 Jan 25];19:202-207 b. Available from: https://www.ncbi.nlm.nih.gov/pubmed/15920934
https://www.ncbi.nlm.nih.gov/pubmed/1592...
). Thus, individuals with restricted fluid intake can benefit from its use, leading to better adherence to their treatments, reducing discomfort and suffering.

Study limitations

Most of the studies presented level of evidence 2; however, there was a lack of standardization of chewing gum sizes, flavors and time of use of these strategies among the selected researches. In addition, there was a lack of explicit calculation of sample size and reduced sample size, which hinders the generalization power (external validity).

Contributions for the Nursing field

The relevance of this review is the synthesis of the primary studies that point out the use of chewing gum as a viable and effective strategy to reduce the thirst of adults in different scenarios, generating evidence to point out feasible paths in clinical practice.

CONCLUSION

Twelve studies evaluated the effect of chewing gum on adult thirst. The use of the strategy resulted in increased salivary flow, xerostomia relief, and thirst reduction. Thus, chewing gum is effective in reducing discomforts, being feasible and feasible to be used in clinical practice in individuals with restriction of fluid intake, leading to better adherence to their treatments, with relief of discomfort and suffering.

The use of the Visual Analogue Scale to evaluate xerostomia and thirst indicate the scarcity of tools to evaluate these outcomes. As for the indication of the number of chewing gums, it was not possible to establish a pattern, and it is frequent to recommend the use of the gum as desired. In relation to the studied population, there was predominance of studies with patients under dialysis and with cancer.

  • FUNDING
    This study was funded by the Fundação Araucária/Coordination for the Improvement of Higher Education Personnel (in Portuguese, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior).

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Publication Dates

  • Publication in this collection
    18 Apr 2019
  • Date of issue
    Mar-Apr 2019

History

  • Received
    07 Mar 2018
  • Accepted
    06 Aug 2018
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