Malocclusion is a common health problem and can affect the psychosocial well-being in the long term. ¹ Prevention and treatment of this developmental disorder need a rational planning of oral health aiming at orthodontic cares, ² , ³ and comprehensive data about malocclusion such as prevalence are necessary in this regard. Assessment of malocclusion in a community can show only the prevalence of different degrees of deviation from normal occlusion, ⁴ some of which have no need for any treatment. However, when changes in normal occlusion affect the function and aesthetics, the need for orthodontic treatment becomes more evident. ⁵ Therefore, evaluation of orthodontic treatment need by indices seems to be necessary. Among several indices developed for this purpose, ² , ⁶ the index of orthodontic treatment need (IOTN) ⁷ and dental aesthetic index (DAI) ² are universally acceptable and have been more frequently used in epidemiological studies. The IOTN ranks malocclusion in terms of the significance of various occlusal traits for an individual's dental health and perceived aesthetic impairment, aiming at identifying those individuals who will most likely benefit from an orthodontic treatment. The index has two components: aesthetic and dental health. The aesthetic component of IOTN is a self-perceived index of dental attractiveness which can help us to evaluate changes of attractiveness by malocclusions. ⁸ The DAI links the clinical and aesthetic components mathematically to produce a single score that combines the physical and aesthetic aspects of occlusion, which reflects malocclusion severity and orthodontic treatment need. ²

In Iran, in particular, many epidemiological studies have been carried out on this subject. A literature review of national documents showed orthodontic treatment need varied from 1.58% to 48.2% in different cities of Iran. In Tehran, Safavi et al. reported 20% definite orthodontic treatment need by IOTN in 5200 adolescents aged 14–16 years. ⁹ Borzabadi-Farahani et al. showed 36% of adolescents in Isfahan needed orthodontic treatment. ¹⁰ Another study conducted by Oshagh et al. in Shiraz using DAI showed that 20.4% of 1818 adolescents had high orthodontic treatment need. ¹¹ Furthermore, Eslamipour et al. reported 20% orthodontic treatment need among 728 adolescents in Isfahan using DAI. ¹²

Yet, there is no comprehensive report about this subject. A meta-analysis can provide valuable data on the prevalence of orthodontic treatment need as a component of oral health status of Iranian population, which seems to be useful for policy making and program planning in oral public health system. Thus, the present study was aimed to undertake a meta-analysis to systematically review existing evidence on the prevalence of orthodontic treatment need in Iran.

Search strategy

Literature search methods included scouring original articles in the following electronic databases: PubMed, Scopus, Google scholar, and national database including Iranian Scientific Information Database, indexing article published in Iranian biomedical journals (Iran Medex), Magiran which index thesis abstracts and articles up to November 2015. Searching for articles was performed by two independent researchers according to search strategy shown in Table 1. Search terms included “orthodontic treatment need, index of orthodontic treatment need, prevalence, permanent dentition, Iran, and cross-sectional studies.”{Table 1}

In addition, the references of the included studies were searched for further relevant studies. Handsearching was also performed using Iran doc and National Library and Archives of Islamic Republic of Iran, for available theses, dissertations, and unpublished articles.

Selection of studies

The selection process was performed by two investigators (F.E and Z.A) in a two-step approach independently. After excluding duplicated articles, at first step, abstracts of all matched articles were reviewed for exclusion of those clearly not related to our purpose. The second phase consisted of detailed full-text analysis of the screened eligible studies. Descriptive studies which assessed treatment need using IOTN or DAI in Iranian population aged 11–35 years old are included in full-text analysis and exclusion criteria's are epidemiological studies on orthodontic treatment needs in primary or mixed dentition, studies which samples were chosen among syndromic or specific patients, studies conducted on population referred for orthodontic treatment to oral health centers, and studies which conducted on other nationality who lives in Iran.

Quality assessment

After selecting the articles, assessing the risk of bias of studies was conducted using Modified STROBE checklist. This checklist contains 12 questions which are listed in Table 2which covered various aspects of the methodology such as sample size, study design, sampling method, population, data collection methods and tools, examining samples method, statistical analysis, aim of the study, way of reporting findings, and reporting findings based on objectives. Each study was awarded a score of 0 to 12. If a study achieved less than 8 point, it is omitted from meta-analysis. ¹³ All retrieved full-length articles were evaluated for inclusion in the evidence base against a list of inclusion criteria independently by two trained reviewers. A third reviewer facilitated article reassessment and discussion to resolve conflicts.{Table 2}

Data extraction

Data extraction from the included articles was performed by one of the reviewers. The following information was extracted from every included original article: the first author, year of publication, the city where the study conducted, the total number of samples, the number of samples by sex if reported, and the prevalence of each component of indices of IOTN or DAI. Both components of IOTN categorized orthodontic treatment need in 3 groups: no need, borderline need, and severe need. DAI divided treatment need into 4 groups: no need, borderline need, definite need, and severe need.

Analysis

A comprehensive meta-analysis (V2.2, Biostat) was used to conduct the meta-analysis. A stratified analysis was conducted in accordance with 3 groups of DHC and AC components of IOTN and 4 groups of DAI. Fixed effects or random effects models were selected based on the heterogeneity shown by the Chi-square based Q test and I ²statistic. Since the distribution of values in all of the meta-analyses exhibited significant heterogeneity, we used a random effects model for all meta-analyses. Publication bias was assessed by funnel plot, Egger's weighted regression, and Begg's rank correlation methods. ¹⁴ After exclusion, a sensitivity analysis was performed to evaluate the effect of sample size on the pooled prevalence. If the outcome was significantly changed after one study was removed, then the study was excluded from the included studies due to selection bias, and a new analysis was conducted. ¹⁵ P < 0.05 was considered statistically significant for all analyses.

Study characteristics

The result of search in national and international databases was 443 articles which completed by 2 articles of handsearching. After excluding irrelevant and duplicated articles, evaluating the relevancy of titles and abstracts was done and finally 27 articles selected. After applying inclusion and exclusion criteria, 24 articles remained Figure 1. Five articles measured only DAI, 17 articles used IOTN, and 2 of them used both DAI and aesthetic component of IOTN for measuring orthodontic treatment need Table 3and Table 4. Figure 1

Flowchart of study selection.

Management of malocclusion is carried out by a number of disciplines in dentistry, particularly orthodontics, and its priority can be measured by IOTN and DAI, which is related to treatment need rather than its complexity.

In epidemiological surveys of malocclusion, it is important to gather accurate and reliable data about orthodontic treatment need. These data can then be used for policy making of health-care systems and resource planning purposes or for evaluating the effectiveness of orthodontic care services. Indices of orthodontic treatment need have the potential for both acquiring descriptive data on the distribution of treatment need in populations (epidemiological use) and establishing priorities for treatment (administrative use). This systematic review and meta-analysis was undertaken to assess existing evidence on the prevalence of orthodontic treatment need in Iran.

Based on the results of this study, orthodontic treatment need was found to have a prevalence of 16.1% according to DAI. Studies conducted in Asia reported 12.8% and 24.1% orthodontic treatment need in India ³⁷ and Malaysia ³⁸ according to DAI, respectively, which was relatively close to the results obtained in Iran. But in African countries, the prevalence was up to 44.7%. ³⁹ In American countries, studies reported a prevalence of 53.2% ⁴⁰ and 32.8% in Brazil, ⁴⁰ , ⁴¹ which is higher than the prevalence rate in Iran. According to the results of DHC-IOTN, the prevalence of Iranian orthodontic treatment need was similar to that of European countries such as Italy (27.3%), ⁴² Serbia (27.4%), ⁴³ and Spain (21.8%). ⁴⁴ Studies conducted on the prevalence of orthodontic treatment need according to AC-IOTN showed self-perceived need of 2% in London, ⁴⁵ 7.1% in Brazil ⁴⁰ and 4.4% in Spain, ⁴⁴ which were similar to the prevalence rate in Iran (4.8%). However, the prevalence rates of Eastern Asian countries such as Malaysia (22.8%) ³⁸ and Africa (more than 10%) ⁴⁶ , ⁴⁷ were higher than that of Iran Table 7.{Table 7}

According to the obtained results, people's self-assessment of their dental appearance is different from a professional assessment. It is because professional measures (DHC-IOTN and DAI) evaluate all dental aspects, including missing, diastema, crowding, crossbite, overjet, and open bite. Meanwhile, the self-assessment measure (AC-IOTN) only focuses on the attractiveness of anterior dental appearance at smile. Hence, these indices show different aspects of orthodontic treatment need, all of which can be used to complement each other in epidemiologic surveys and diagnostic procedures.

Previous studies have shown a high correlation and diagnostic agreement between AC (IOTN) and DAI. ⁵⁰ , ⁵¹ In their study in Iran, Borzabadi-Farahani et al. ³⁰ reported a statistically significant association between DAI and AC scores (rho = 0.795). This result was expected since both indices are heavily based on the aesthetic aspects of occlusion.

One of the limitations of this meta-analysis was lack of studies in different geographic regions of Iran; hence, more epidemiologic studies about orthodontic treatment need are suggested to be carried out in different regions of Iran.

Another limitation was a few studies on orthodontic treatment need according to DAI in Iran.

The majority of Iranian population were categorized in no-need group with regard to orthodontic treatment need. According to DHC, nearly one-fourth of the population would have a mandatory need for orthodontic treatment. Using DAI, less than one-fourth (16%) of samples had an increasing need for orthodontic treatment. If the AC scores were used as a self-perceived index, the treatment need would decrease to 5% among the samples. To sum up, Iranian population had more orthodontic treatment need than they perceived, and the majority of them were satisfied with their dental appearance. On the other hand, the majority of them perceived themselves as attractive with regard to their dental appearance.

Acknowledgments

We would like to thank all of participants who help us to conducting this study. Based on a thesis submitted to the school of Dentistry, Isfahan University of Medical Sciences, in partial fulfillment of the requirement for the DDS/MSC degree, this study was supported by Isfahan University of Medical Sciences Research (Grant No. 3941024).

Financial support and sponsorship

This study was supported by Isfahan University of Medical Sciences Research (Grant No. 3941024).

Conflicts of interest

The authors of this manuscript declared that they have no conflicts of interest, real or perceived, financial or nonfinancial in this article.