Signs of Combination Syndrome and removable partial denture wearing

Introduction: Combination Syndrome (CS) is a pathological condition observed in maxillary complete denture (CD) and mandibular removable partial denture (RPD) wearers. Purpose: The aim of this study was to observe and measure the prevalence of CS signs in treatment-seeking wearers of maxillary CD associated or not with RPD (mandibular Kennedy Class I). The association between RPD wearing and the number of CS clinical signs was also evaluated. Material and method: The sample included 62 patients seen at the Department of Dentistry, Federal University of Rio Grande do Norte (UFRN). A clinical oral examination was conducted to assess the presence of specific clinical signs of CS as described by Kelly (1972): bone resorption in the maxillary anterior region, tuberosity overgrowth, palatal papillary hyperplasia, extrusion of mandibular anterior teeth and bone resorption in the mandibular posterior region. The chi-square test at the 95% level of significance was used to test the association between dependent and independent variables. Result: Mandibular resorption was the most frequent complication (93.5%). There was a statistically significant difference between RPD wearers and non-wearers with regard to extrusion of mandibular anterior teeth (p = 0.045). Conclusion: Within the limitations of the present study, a high prevalence of CS clinical signs was observed, but no association between RPD wearing and syndrome characteristics was found. Descriptors: Denture, partial, removable; denture, complete; bone resorption. Rev Odontol UNESP. 2014 Nov.-Dec.; 43(6): 390-395 Signs of Combination Syndrome... 391


INTRODUCTION
Th e Glossary of Prosthodontic Terms 1 defi nes Combination Syndrome as a set of characteristics that occur when an edentulous maxilla is opposed by mandibular anterior teeth.Kelly, 2 in 1972, introduced the term Combination Syndrome when analyzing six patients wearing a maxillary complete denture occluding with a distal-extension removable partial denture (Kennedy Class I RPD).Th e characteristic features of this syndrome include: loss of bone from the anterior portion of the maxillary ridge, overgrowth of the tuberosities, papillary hyperplasia of the mucosa of the hard palate, extrusion of mandibular anterior teeth, and loss of alveolar bone and ridge height beneath the removable partial denture bases.Some years later, new features were attributed to Combination Syndrome: loss of vertical dimension of occlusion, occlusal plane discrepancies, spatial repositioning of the mandible in the anterior region, poor denture fi t and periodontal alterations 3 .
Prevention of degenerative changes caused by complete dentures occluding with bilateral distal-extension removable partial dentures is possible through an appropriate treatment plan and with periodic review of the RPDs and remaining teeth.Treatment alternatives such as preservation of posterior teeth to support mandibular RPDs and use of overlay-type complete dentures provide more adequate occlusal stability and should be considered as treatment options 2 .
Although Kelly 2 mentioned the use of an adequate RPD as a way to prevent development of signs of the syndrome, the scientifi c evidence on this eff ect is still limited.Salvador et al. 4 studied the presence of Combination Syndrome signs in patients rehabilitated with mandibular RPDs.Th e authors concluded that patients with Kennedy Class II mandibular RPDs did not show Combination Syndrome, whose prevalence was 25% among the patients attended.Th e most prevalent CS characteristic was maxillary anterior bone resorption, which was present in 81% of the Kennedy Class I patients and in 75% of the Kennedy Class II patients.Kelsey 5 stated that intolerable forces produced by poorly fi tted dentures can cause pressure and infl ammation of the supporting tissues, which can make bone loss on the alveolar ridge inevitable.Tolstunov 6 stated that use of poorly fi tted dentures for a prolonged period may contribute to mandibular posterior bone resorption.It is essential to identify the initial symptoms of CS and take steps for its immediate correction 6 .Shen, Gongloff 7 found changes in 24% of their patients with natural mandibular anterior teeth and maxillary complete dentures, and found that this rate was not signifi cantly diff erent for patients that did or did not use mandibular removable partial dentures.Faced with these confl icting results, studies are needed that relate the Combination Syndrome signs to RPD wearing, in order to evaluate whether wearing a mandibular denture could minimize the development of syndrome signs.Th us, diagnosis of this condition can facilitate implementation of appropriate clinical conduct and check the destructive process.
Th e present study's objective was to observe and measure the prevalence of Combination Syndrome or Kelly signs found in patients wearing maxillary complete dentures (CD) with or without mandibular Kennedy Class I removable partial dentures (RPDs) and fi nd out whether there is an association between RPD wearing and the prevalence of clinical signs of the syndrome.

MATERIAL AND METHOD
A cross-sectional study was conducted in the Department of Dentistry, Federal University of Rio Grande do Norte (UFRN), with the approval of the Research Ethics Committee of the institution, under Protocol 409896.Th e sample was selected from patients with a completely edentulous maxilla wearing maxillary complete dentures (CD) and with a bilateral partially edentulous mandible (Kennedy Class I), wearing or not wearing a mandibular removable partial denture (RPD), who were seeking treatment at the UFRN Prosthodontics Clinic between April and June 2011.Patients wearing mandibular RPDs that were not made with a metal structure and/or patients who showed signs of poor general health were excluded.
Based on the sample selected to evaluate the association between Combination Syndrome signs and mandibular RPD wearing, considering a 95% confi dence interval, a power of 80% and an estimated 50% rate of individuals who did not wear dentures (control), the size of the sample is suffi cient to indicate a signifi cant diff erence when the diff erence is greater or equal to 30%, hence adequate to generate hypotheses.
Aft er signing a free and informed consent form, the individuals participated in an interview on their denture history and time of edentulism.Th en they were submitted to a clinical oral examination conducted by two trained researchers who made a joint analysis to determine the presence or absence of the clinical signs specifi c for Combination Syndrome (CS), as described by Kelly 2 : bone resorption in the maxillary anterior region, tuberosity overgrowth, palatal papillary hyperplasia, extrusion of natural mandibular anterior teeth and mandibular posterior bone resorption (Chart 1).If there was any inconformity with regard to the presence of any of the established criteria, a third examiner, expert in the matter, would resolve it.
Th e variables were presented in a descriptive manner by means of absolute numbers and proportions.To determine the association between the dependent (clinical signs of CS) and independent (mandibular RPD wearing and time of maxillary edentulism) variables, the chi-square test was used with a signifi cance level of 5%.
RESULT Th e sample was composed of 62 patients with a mean age of 58.9 years, a minimum of 39 and a maximum of 78 years, where 21% (n = 13) were men and 79% (n = 49), women.Th ese individuals had maxillary edentulism for a mean period of 28.4 years, with a minimum of 2 years, a maximum of 53 years and a standard deviation of 10.1.
In the sample studied, 53.2% (n = 33) of the patients wore mandibular RPDs.CS clinical features were quite prevalent in the sample, except for palatal papillary hyperplasia, which was present in only 16.1% (n = 10; Table 1).
The patients were not evaluated with regard to diagnosing CS by counting specific signs to determine whether they had the syndrome or not, but rather with regard to the presence or absence of each sign and the number of signs per individual.
Of the characteristics, the most frequent was the presence of mandibular resorption (93.5%;Table 1) and the most frequent occurrences were the presence of 3 signs (45%) and 4 signs (32%) per individual, representing a total of 77% of the sample, a value that demonstrates the high prevalence of CS clinical features in patients presenting the profile studied (Table 2).
With regard to the association between mandibular RPD wearing and CS features, a statistically significant difference between RPD wearers and non-wearers was observed only with regard to extrusion of mandibular anterior teeth (p = 0.045; Table 3).The mandibular resorption data could not be analyzed by the statistical test (Table 3), since 100% of the patients wearing RPDs showed this characteristic, making it invariable, thus having a cell with zero value, and making it impossible to use the test.

DISCUSSION
The term syndrome signifies a set of signs and symptoms that are found associated to a known or unknown entity.By this definition, CS would only be diagnosed when all its signs are present.Nevertheless, there is still no clear indication in the dental literature that all its signs must be present for CS to be diagnosed 4 .Consequently, in the present study, the prevalence of CS signs was assessed rather than the diagnosis of CS.
In the present study, 93.5% of the sample showed mandibular posterior bone resorption, the CS clinical sign most prevalent among the dependent variables studied (Table 1).This clinical feature is common among these patients owing to the natural mandibular bone resorption process that occurs primarily in height.Another factor that influences the presence of this clinical feature is the quality of denture fit 5 .The greater the denture misfit, the greater will be the induction of forces on the residual ridge and its resorption.In the sample, 100% of the individuals wearing RPDs showed this characteristic.Tolstunov 6 stated that bone is deposited and resorbed according to the tensions placed upon it.The use of poorly fitted dentures for a prolonged period may contribute to this type of resorption.In the sample studied, the technical quality of the patients' dentures was not assessed, and the fact that the sample was drawn among patients seeking new dentures may have contributed to the high resorption value found for the patients wearing dentures.This result was not very different from that found for the patients who did not wear dentures (86.2%), showing that lack of a denture is also detrimental.The statistical significance with regard to denture wearing and this clinical feature was not evaluated owing to a zero cell in the data distribution (Table 3).Shen, Gongloff 7 observed no difference with regard to manifestation of this characteristic between wearers (56%) and non-wearers (46%) of a bilateral distal-extension mandibular RPD.Reduction of mandibular posterior support results in a gradual reduction of occlusal load in this region and a consequent increase in load in the anterior region, which can result in excessive pressure on the anterior portion of the maxilla, accelerating the process of maxillary anterior bone resorption and promoting the appearance of loose hyperplastic tissue 3 .This provides an explanation for the research findings that show a high prevalence of 74.2% (n = 46) of maxillary anterior resorption (Table 1).This high prevalence is in accordance with the findings of Kelly, 2 but disagrees with this author when he identifies this characteristic as being the most prevalent 3 .No statistically significant difference between wearers and non-wearers was observed with regard to this syndrome manifestation.This may occur owing to the absence of posterior support among the patients who had no mandibular arch rehabilitation or had unsatisfactory rehabilitation, generating similar problems in the anterior region.
An overgrowth of tuberosities was present in 61.3% of the sample, representing 60.6% of the patients wearing an RPD and 60.6% of those who did not (Table 1 and 3).There was no association between the presence of this characteristic and mandibular RPD wearing, as can be seen from the quite similar values.This similarity may have occurred because poorly fitted mandibular dentures may have a biomechanical behavior compatible with denture absence.Shen, Gongloff 7 found a similar prevalence (56%) when they evaluated patients with bilateral distally edentulous mandibular arches wearing a maxillary CD and a mandibular RPD, but found a lower value (22%) for patients who did not use an RPD.The difference between the results of the present study and those found by Shen, Gongloff 7 may be justified by the relatively small sample of mandibular RPD wearers and non-wearers of the latter study (n = 25).
The sign least frequently found in the present study was palatal papillary hyperplasia (16.1%), an inflammatory change caused by wearing poorly fitted dentures, often combined with poor hygiene and some other predisposing factors.In epidemiological studies conducted on mucosa changes, primarily among denture users, the prevalence of hard palate papillary hyperplasia is low 8,9 .Xie et al. 9 found values that ranged from 5% to 10%.MacEntee et al. 8 found hyperplasia in 8% of 155 denture wearers.Coelho et al. 10 observed inflammatory fibrous hyperplasia in 16.7% of the sample in a prevalence study with 334 individuals.Another study, conducted in Turkey in 2009, consisting of 170 complete denture wearers, showed that the incidence of papillary hyperplasia increased with time of denture wearing: 13.3 % from 0 to 10 years of denture wearing and 86.7% for more than 10 years 11 .
The literature points to specific clinical data that define CS, but there is no evidence that an individual must show the five clinical signs simultaneously to be considered as having the Combination Syndrome.In this study, it was found that 77% (n = 48) of the patients showed 3 to 4 clinical signs characteristic of CS.Shen, Gongloff 7 evaluated the presence of some clinical CS signs defined by Kelly 2 in 1972 and others added by Saunders. 3onsidering only Kelly's CS signs, a greater prevalence of 3 signs was found in patients with a maxillary CD and the presence or absence of a bilateral distal-extension RPD.The high number of signs per individual in our study also may be justified by the long period of edentulism of the sample and the consequent greater establishment of degenerative processes resulting from complete maxillary and partial mandibular edentulism without adequate treatment.
In relation to the use of a mandibular removable partial denture, the literature indicates that it prevents the appearance of some signs 3 .The present study found no evidence that RPD wearing provided benefits in preventing CS.The only clinical sign that showed an association with RPD wearing was tooth extrusion.However, the association was related to RPD wearing; in other words, RPD wearers had more extrusion than nonwearers.This result indicates that the dentures probably were unsatisfactory or that the dental arches were not simultaneously rehabilitated, or even that the individuals already showed CS characteristics when first rehabilitated.In a comparative study, Jozefowicz 12 investigated the influence of denture wearing on residual ridge resorption and found that individuals who did not wear dentures had significantly higher residual ridges than those who wore dentures, except for the female group from 60 to 79 years of age.Previously, Cambell 13 found a similar result, but the difference between the wearer and non-wearer groups was not statistically significant, perhaps owing to the small sample used.Alveolar bone resorption is an inevitable process after tooth loss, but it can be minimized with the construction of well-fitted dentures, scheduled follow-up sessions and guidance on denture wearing and care 5 .In 1972, Kelly 2 observed extrusion in 100% (n = 6) of individuals evaluated radiographically after a period of 3 years, which is in accordance with our findings.As Tolstunov 14 stated, prevention of posterior occlusion loss and anterior hyperfunction are considered the main treatment approaches for CS.The RPD is one of the treatment modalities to correct and treat CS among those available, as long as it is planned to preserve stability, including a maxillary complete denture as antagonist, with a balanced distribution of occlusal tensions and careful maintenance in order to preserve posterior occlusion 6 .For patients who already show CS features, these can be minimized with surgical procedures, special anatomical impression-taking techniques for flaccid tissue, and correct surveying and planning of the rests and clamps of the mandibular RPD infrastructure.Periodic return visits to the dental office to check the need for relining, the integrity of the occlusal contacts, and denture hygiene and fit are also important for these patients.
There is also the possibility of treating these patients by placing implants in the mandibular posterior region, eliminating the need for a distal extension, and impeding the vertical and lateral movements responsible for accelerated bone resorption below the RPD resin base 15 .This alternative changes the Kennedy Class I configuration to a Class III one, with a biomechanical advantage, improving masticatory efficiency as well as denture stability and esthetics, depending on the positioning of the implant 16 .
Palmqvist et al. 17 observed that, in patients who received mandibular implant-supported fixed dentures, bone resorption in the posterior part of the mandible practically ceased.Consequently, treatment with implants on both arches is a factor to be considered to control bone resorption associated with Combination Syndrome 18 .
One of the limitations of this study is the fact that the sample was not probabilistic and representative of the general population.In addition, the fact that the patients were seeking treatment may have made it more likely that they would have CS signs and have been using inadequate dentures.Also, because it was a cross-sectional study, all the measurements were made at the same time, and, therefore, there was no follow-up period for the individuals.
In spite of the limitations, the large number of signs characteristic of the syndrome present in this research is a fact that calls attention to the range of damage already caused, resulting from the lack of follow-up of the dentures installed, insufficient or inadequate treatment, or even the lack of an early diagnosis.This situation will change when the clinician dealing with a susceptible patient is aware of the importance of preventing, diagnosing and intervening early so that damage does not occur, or is minimized.
To evaluate the benefit of RPD wearing in preventing CS signs, controlled and randomized clinical trials evaluating the presence of clinical signs immediately after installation and after prolonged denture-wearing periods are warranted, together with monitoring of the quality of these dentures.Thus, further research should be conducted to assess the association of syndrome features and RPD wearing in longitudinal studies monitoring patients right after they lose their teeth, where the technical quality of the dentures constructed should also be evaluated.

CONCLUSION
It was found that the clinical signs of CS were quite prevalent, except for palatal papillary hyperplasia.The majority of patients showed 3 to 4 signs.The presence of a mandibular RPD with inadequate technical quality or RPD absence were shown to be indifferent with regard to manifestation of clinical CS characteristics, i.e. no association between RPD wearing and CS characteristics was observed.

Chart 1 .
Description of the Clinical Examination Syndrome Characteristics Clinical Evaluation Bone resorption in the maxillary anterior region Observation of flaccid tissue in the anterior region of the residual ridge susceptible to displacement Tuberosity overgrowth Vertical and/or horizontal growth of fibrous or bone tissue in the right and/or left tuberosity region Palatal papillary hyperplasia Observation of erythematous mucosa with a papillary surface in the hard palate Extrusion of the remaining natural mandibular teeth Observation of dental wear at the enamel or dentin level Mandibular posterior bone resorption Observation of accentuated bone resorption in the posterior edentulous region

Table 1 .
Prevalence of signs of Combination Syndrome.Absolute and relative values

Table 2 .
Frequency of clinical signs of Combination Syndrome per individual.Absolute and relative values

Table 3 .
Prevalence of CS signs and their association with mandibular RPD wearing.Absolute and relative values and statistical significance.