Factors related to orthodontic treatment time in adult patients

Contact address: Ana Camila Esteves de Oliveira Melo Rua Jerônimo Pimentel, 117 – B. Umarizal – Belém/PA, Brazil CEP 66055-000 – E-mail: millamelo18@hotmail.com 1 Specialist in Orthodontics, ABO/PA. 2 Postgraduate student in Orthodontics, Federal University of Pará (UFPA). 3 Specialist in Orthodontics, ABO/PA. MSc in Oral Pathology, UFPA. 4 Professor, Department of Orthodontics, ABO/PA. MSc in Dentistry, UFPA. 5 Associate Professor, Department of Orthodontics, UFPA.


INTRODUCTION
In today's society, the quest for esthetic perfection is no longer just an aspiration of the youth.As a result, there is an increasing number of adult patients who seek orthodontic treatment to improve not only function but appearance as well. 1,2mong the key factors that afect patients and serve to characterize adult vs. young patients are the absence of active growth, higher occurrence of dental mutilation and periodontal involvement. 2,3However, the time required for treatment is a major concern of adult patients.Thus, orthodontists must be prepared to provide treatment that meets the speciic needs of such patients.
Despite the disagreement regarding which variables exert a signiicant inluence on orthodontic treatment time, no study has hitherto been published in the literature focusing on adult patients.The aim of this work was to investigate the inluence exerted by diferent variables on the duration of treatment in adult patients.

MATERIAL AND METHODS
The records of 4,723 patients treated by three orthodontists with a professional experience of over 20 years were examined.Exclusion criteria included patients under 18 years with incomplete records, patients with more than one tooth missing per quadrant, patients previously treated by orthognathic surgery, syndromic and clet patients, Class III malocclusion, retreatment cases, and patients who missed appointments for more than six months in a row or alternately.Thus, 123 adult patients were selected.Ater analyzing the quality of treatment ater it was completed, 53 cases were excluded.The inal sample consisted of 70 adult patients whose inclusion criteria were: patients aged 18 to 66 years, 48 females and 22 males, Angle Class I or II malocclusions as assessed based on canine relationship.
Treatment time in months was the main variable analyzed.The following predictor variables were observed at baseline (T 0 ) and analyzed: Sagittal canine relationship, planned extractions, sex, age, facial pattern, severity of malocclusion, type of brackets (ceramic or metal), missed appointments and appliance issues.
Table 1 shows a summary of nominal variables analyzed in the study.
Severity at the start of treatment was examined by the PAR index, and measured with a universal caliper (Mitutoyo, Brazil, model/code 530-102).
Intraexaminer error was evaluated by performing new measurements and calculating a new PAR index for the models of all selected patients.The irst and second measurements were performed with a time interval of 14 days.Dahlberg's formula was applied to estimate random error while systematic error was examined by intraclass correlation.
Initially a correlation matrix was applied in order to examine which predictor variable could be asso-

RESULTS
Total mean treatment time was 32.2 months, and mean age at start of treatment was 27.7 years.The average number of appliance issues and months of missed appointments was about 3, and the mean number of extractions was 0.75.Systematic error analysis revealed excellent repeatability (R 2 =0.9662) of the PAR index at T 0 (mean=14.06),associated with a small magnitude random error (Table 2).
Correlation analysis revealed that the variables "number of appliance issues", "missed appointments (number of months)", "PAR index at T 0 " and "type of brackets (metal or ceramic)" were somewhat correlated (p < 0.05) with the main variable, i.e., "length of treatment."The variable "number of extractions" was also included due to its p-value (0.0543), which was very close to the value established for the level of signiicance (Table 3).
Multiple linear regression revealed that among the ive dependent variables included in the analysis, only "number of issues/breakages" and "months of missed appointments (no-shows)" proved signiicant (p<0.001).Stepwise regression showed that together the ive variables exerted an inluence of 54.33% on treatment time variability, with "number of appliance issues/breakages" showing an inluence of 29.71% (p<0.001), and "missed appointments" an inluence of 14.04% (p<0.001),followed by the PAR index at T 0 , with an inluence of 6.51%, "number of extractions" (2.42%) and inally "type of brackets" exhibited an inluence of 1.65% on the total treatment time.more et al. 9 may have been inluenced by the decision to extract teeth when the treatment was already in an advanced stage as the patient failed to wear intraoral elastics.In turn, in the work of Vu et al. 11 length of treatment may have been afected by the authors' decision to carry out treatment in two phases.In this study, the canine relationship was initially a variable that did not increase the duration of treatment signiicantly.It should be noted that in the present investigation 13.51% of patients started treatment with a Class II, and eventually had this relationship corrected only at the level of the canines by extracting two maxillary premolars.Given that these patients continued to present with molar Class II malocclusion, one might feel compelled to question the fact that if the molar sagittal relationship had also been corrected, treatment time may have been prolonged.
The variable "type of bracket", whether metal or ceramic, had no bearing on the duration of treatment.This factor has seldom been explored in the literature.It can only be found in a study by Beckwith et al, 4 which concludes that it has no influence on the length of treatment.
The decision to extract or not to extract and the amount of extractions planned for orthodontic treatment has been a widely researched variable that helps to determine to what extent the total treatment time is affected by these extractions.This has been an ongoing concern of orthodontists.Although significant relationships between duration of treatment and the decision to extract, or not, have been widely observed in the literature, 5,6,8,9,15,16,18,19,20,21,23,24 this study could not find a significant relationship between these variables, concluding that the decision to extract or not does not affect treatment time.This outcome resembles the findings of Beckwith et al, 4 Poppwich et al, 10 and Bhattarai et al. 17 As documented in the literature, patient sex had no impact on the duration of treatment. 4,5,8One exception is the work of Skidmore et al, 9 which found that male patients are a predictor of longer treatment time.The variable "facial pattern" had not been examined in previous studies in terms of orthodontic treatment time.It was assessed in this study and showed no such influence.
In assessing the severity of the initial malocclusion, as measured in this study through the PAR index,

DISCUSSION
Today, establishing distinct goals as the desired outcomes of orthodontic treatment in adult patients is under debate.Thus, assessing the influence of some variables on treatment time is of paramount importance in defining the guidelines of orthodontic treatment in these patients.Some studies have examined factors related to treatment time.However, the mixed results achieved by these different studies -whose samples comprise adults, youth and children -have raised doubts as to the factors that may unequivocally have a bearing on the duration of orthodontic treatment in adults.
This study was therefore geared exclusively towards the study of adult patients treated by three seasoned professionals, each with over 20 years experience, thereby reinforcing and enhancing the reliability of the results.Furthermore, as a result, "lack of experience" is ruled out as a factor that could lengthen the duration of treatment.
The mean duration of treatment in this study was 32.2 months, similar to the findings of Dyer et al. 3 (30.7 months) and Robb et al. 7 (30.6 months).
The variables that showed statistically significant influence on treatment time were "number of months the case was left with no monitoring due to missed or canceled appointments" (p< 0.0001), which accounted for 4.14% of the influence on the overall treatment time, and "number of appliance issues/breakages" (p=0.0037), with an influence of 29.71%.These results corroborate previous findings. 4,5,7,9,18,21And although all these studies included adult patients in their samples, they also had children and/or adolescents, which shows that regardless of age, behavioral factors pertaining to the patients themselves can exert substantial influence on the duration of treatment.
Insofar as Class I or Class II relationship is concerned, this study was based on the canine relationship given that patients with missing teeth were also included.This contrasts with the studies found in the literature, which focus solely on molar relationship.Some studies found no inluence of the molar relationship on treatment time. 10However, other studies 9,11 reported that the treatment of patients who present with a Class II at the beginning of treatment seem to take longer than Class I patients.The study by Skid- the authors believed that the patient's initial occlusal problems would likely lengthen treatment time, which might be necessary to tackle those issues satisfactorily.This variable, however, did not play a statistically significant role in the duration of treatment, corroborating previous findings. 6,7,13Nevertheless, other studies have revealed that the severity of the initial malocclusion influences to a significant extent the duration of treatment. 5,8,11,12,14,15t should be noted that all studies referenced in this research involved the investigation of variables likely to influence treatment time.None of them, however, focused exclusively on adult patients, but rather included children and/or adolescent patients in their sample.This realization underscores the importance of conducting further studies geared specifically to adult patients.

CONCLUSIONS
Based on the indings of the study, the following conclusions can be drawn: 1. Patients' behavioral factors (missed appointments and appliance issues/breakages) played a signiicant part in lengthening treatment time.
2. Other factors such as initial canine relationship, the choice of metal or ceramic brackets, extractions included in the orthodontic plan, initial age, PAR index at the start of treatment, sex and facial pattern had no signiicant inluence on the treatment time of adult patients.
3. Within the scope of this study it was found that these variables accounted for only 54.3% of the overall inluence exerted on the duration of treatment, suggesting that other factors should be investigated to determine the actual time length required to perform orthodontic treatment in adults.

Table 1 -
Summary of nominal variables included in the study.original article Melo ACEO, Carneiro LOT, Pontes LF, Cecim RL, Mattos JNR, Normando D Dental Press J Orthod.2013 Sept-Oct;18(5):59-63 ciated with treatment time.Variables with signiicant correlations were included in the multiple linear regression analysis, which was complemented by linear stepwise regression.Statistical analysis were performed by BioEstat 5.3 sotware (Mamirauá Institute, Belém, Pará state, Brazil).All tests were applied adopting a signiicance level of 5%.

Table 3 -
Correlation Matrix and linear regression analysis.

Table 2 -
Descriptive analysis of numerical variables.
Factors related to orthodontic treatment time in adult patients original article Dental Press J Orthod.2013 Sept-Oct;18(5):59-63