Epidemiology of orthodontic treatment need in southwestern Ethiopian children: a cross sectional study using the index of orthodontic treatment need

Malocclusion is an appreciable deviation from an ideal occlusion [1]. Many of these deviations are within the range of what is to be considered as normal biologic variation. However, some deviations may have negative influence on dento-facial development, contributing to impaired oral functions, susceptibility to facial traumatic injuries and development of caries and periodontal problems [2, 3]. In addition, malocclusion could cause psychosocial problems related to impaired/altered dento-facial esthetics [2, 4, 5]. Orthodontic treatments comprise a large proportion of dental treatment and in most cases they are carried out during adolescence and early adulthood to solve malocclusion problems [2].

The planning of orthodontic treatment within a public health system requires information on the orthodontic treatment needs of the population [6, 7]. With the growing demand for orthodontic treatment, a variety of clinician based indices have been developed to classify various types of malocclusion, and determine their orthodontic treatment need [3, 8]. These indices can be used in estimating orthodontic treatment need, prioritizing treatment need in patients referred for orthodontics particularly where there are limited resources for orthodontics among pubic health care services, and safeguarding for the patients [8, 9]. One of the most commonly used indices that assess the orthodontic treatment needs among children and adults is the Index of Orthodontic Treatment Need (IOTN), which was developed by Brook and Shaw. The IOTN has two separate components, the aesthetic (AC) and dental health components (DHC), which rank malocclusion in increasing priority according to aesthetic considerations and dental health implication [10].

Various studies have used the index of orthodontic treatment need (IOTN) for measuring the degree of malocclusion and the need for orthodontic treatment in different population sectors. For instance, the prevalence of orthodontic treatment need using IOTN-DHC was 21.3% in France [11], 22% in Tanzania [12], 28% in Kuwait [13], 34.2% in Brazil [14], 34% in Jordan [15], 36.1% in Iran [16], 38.8% in Turkey [17], and 71.6% in Saudi Arabia [18].

With the improvement of the socio-economic situation in Ethiopia, the demand for orthodontic treatment is increasing quite rapidly. Many patients with malocclusion problems visit dental clinics in both government and private health facilities. However, orthodontic concern like other oral health care procedures is given low priority in the health care system because of the high cost of treatment and the shortage of orthodontists. In the light of the above reasons, and since no previous study on Ethiopian children has been conducted, it is important to have epidemiological data to estimate the total need for orthodontic care in this region. The objective of this study was therefore to determine the need for orthodontic treatment using the Index of Orthodontic treatment need and its gender distribution in 12-year-old schoolchildren belonging to Jimma Town, located in southwestern Ethiopia.

A total of 347 aged 12 years old school children participated in the study, giving a response rate of 91.08%. In this study, more than half of the children under study were girls and none of them had a history of orthodontic treatment. About two-thirds (63.4%) of these children were Oromo by their ethnicity and more than half (54.5%) of them were Muslims by their religion. The majority of them (48.4%) were from grade 5 (Table 1).

The results of objective need for orthodontic treatment in this study provide baseline data for planning orthodontic services in Ethiopia. The need for orthodontic treatment based on the DHC scores showed that almost half of the children (48.2%) were in need for orthodontic treatment when the subjects with the moderate or great need for treatment were summed up. A definite need for orthodontic treatment need according to DHC was observed in 30% of the study subjects. This finding is similar to the findings from UK, 32.7% [10], Kuwait, 28% [13], New Zealand, 31.3% [20], Italy, 27.3% [21] and Peru 29.9% [22]. However, the percentage for definite treatment need in this study is higher than the study from Tanzanian schoolchildren [12]. It is also higher than the 18.1% reported for 12-year-old Sahrawi children [23],21% of Saudi Arabian adolescents [24], 21.3% of the 9–12-year-old French schoolchildren [11], 24.7% of 11–15-year-old Bangladesh school children [25] and 15.3% for 12 years old Romanian schoolchildren [26]. On the other hand, a study conducted on 250 school children aged 11–14 years, and 250 patients aged 11–14 years in Turkey showed that 38.8% of the school population and 83.2% of the referred population needed definite orthodontic treatment need [17]. Other studies have also reported a higher finding than the present study [15, 16, 18, 27]. The reported differences in normative orthodontic treatment need may be due to the different methods used and differences among the age groups studied. In addition, some studies included samples with a history of orthodontic treatment and referred for orthodontic treatment.

In the IOTN-DHC index, only the most severe occlusal trait is considered for categorization, despite the fact that other severe symptoms may be present. In this study, the two most common occlusal traits responsible for the final DHC categorization were increased overjet and contact point displacement. Similarly, some previous studies reported increased overjet as the most common trait, followed by crowding [28, 29]. Other studies have found contact point displacement as the most common occlusal trait followed by increased overjet [11, 22, 30]. These observations have public dental health implications because increased overjet and crowding are the occlusal traits commonly associated with traumatic injuries and poor periodontal conditions [31]. Studies also show that increased overjet and inadequate lip coverage are important contributing factors for traumatic dental injuries and that reducing a large overjet is not only beneficial from an aesthetic standpoint but also minimizes the risk of trauma and long-term complications to the dentition [30, 32].

Professional assessment of orthodontic treatment need according to AC of the IOTN, classified 15.3% of the children as being in definite need for orthodontic treatment. This figure is comparable to 13.7% of the 12 years old Western Saharan children [23] and 11.4% of the 12 years old Romanian schoolchildren [26]. In contrast, a study from Brazil found that 8.1% of the 12 years old school children had definite treatment need according to AC of IOTN, which was lower than the current study. In their study, the authors didn’t found a significant gender difference in dental appearance perception corroborating the present findings [28]. Aesthetic Component of IOTN, whether it is examiner or patient-based, assesses malocclusion on the grounds of aesthetic impairment, and by inference reflects the psycho-social need for orthodontic treatment. However, it has shortcomings like the other esthetic orthodontic treatment need indices; the subjective nature of the aesthetic indices and the variable perception of attractiveness between clinicians and patients, and among various cultures or countries [33].

The present study has also found high discrepancy in treatment needs between the DHC and AC of IOTN. The discrepancy may be attributed to the fact that malocclusion traits like missing teeth, crossbites, deep traumatic overbites, non-erupted or impacted teeth has definite need for orthodontic treatment) have dental health implications, but do not attract a high Aesthetic Component score. In addition, as AC is subjective in its nature and assesses the aesthetic aspects of the malocclusion only in frontal view, it brings difficulties in assessing some parameters, such as degrees of Overjet and Overbite [8]. Hence, these indices show different aspects of orthodontic treatment need, both of which can be used to complement each other in epidemiologic surveys and diagnostic procedures.

Dental Health Component of IOTN is a valuable tool in determining the treatment need priority for effective resource use in orthodontic care. It is based on the view that the more a deviation differs from a given norm (the ideal occlusion), the greater are the risks of future objective functional deficits or oral health problems. However, scientific evidence to assess its validity is lacking [34, 35]. Due to this limitation of DHC of IOTN, a recently conducted path model study suggested that orthodontic treatment need assessments should be based on the consequences of malocclusion for the individual [36]. The results of the present study are useful for public health planning and serve as a baseline data for future studies.

The limitations of this study were, since it is institution-based study its generalization will be limited to similar institutions only. Further, this study was performed in a specific age group, which could affect the generalizability of the findings. On the other hand, the possibility of interviewer bias during interviews. Besides, inter-examiner reliability was not tested because we had only one examiner who carried out the clinical examination.

The present study has found that a high percentage of the 12 years old school children were in need of orthodontic treatment need. Increased overjet and Crowding were the most common occlusal features defining the DHC categorization. There was no statistical difference with regard to DHC grades and AC scores between genders. Therefore, publicly subsidized orthodontic treatment should be provided to those who are in great need for orthodontic treatment. Moreover, cost-benefit and cost-effectiveness analyses should be carried out to assess the acceptability of the level of service. The study may also serve as a baseline study for future studies.