INTRODUCTION

For many years, studies have been conducted to determine the prevalence of malocclusion in different populations.1–33 A comparison of these results is almost impossible, and the results of studies, even those studies conducted in a population of the same origin, may show great variability. Variables such as the differences in classification of occlusal relationships, the developmental period of the study sample, examiner differences in determining the bounds of normal, and differences in sample sizes can affect the results. Instead of differentiating normal and abnormal in a population, determining frequencies of different types of malocclusions in a referred population may also give valuable information.

Although, many studies of the prevalence of malocclusion in different populations have been reported, a review of the literature indicates that only a few studies evaluated malocclusion in a referred population.3435 Jones34 investigated malocclusion and facial types in a group of Saudi Arabian patients referred for orthodontic treatment and reported that there were indications amongst Saudi Arabian patients of a tendency for bimaxillary proclination and a greater proportion of Class III malocclusion than in Western communities. Yang35 evaluated patients who visited the Department of Orthodontics at Seoul National University Hospital from 1985 to 1989 and reported that the percentage of Class III malocclusion has been increasing but that of Class I has been decreasing.

The aims of this study were: (1) to determine frequencies of different types of malocclusions, (2) to compare mean ages of the patients in different malocclusion groups, and (3) to evaluate maxillary and mandibular crowding related to malocclusion groups in a sample of Turkish orthodontic referred population.

MATERIALS AND METHODS

A total of 1356 patients (793 girls, 563 boys) referred to the Department of Orthodontics, Suleyman Demirel University, were evaluated in this study. The mean age of the patients was 13.57 ± 3.16 years. These patients were from the southern regions of Turkey, and none of the subjects had undergone previous orthodontic treatment. Orthodontic examinations of the patients were carried out by the authors. Patients with systemic diseases were excluded from the study. Four malocclusion groups were formed according to the following criteria:

• Class I group: Class I soft tissue profile; positive overjet up to three mm; Angle Class I molar relationship in centric occlusion.

• Class II, division 1 group: Convex soft tissue profile; excessive overjet (more than three mm); protrusive maxillary incisors; Angle Class II molar relationship in centric occlusion.

• Class II, division 2 group: Decreased anterior facial height; excessive overbite (more than three mm); retroclination of two or more maxillary incisors; Angle Class II molar relationship in centric occlusion.

• Class III group: Concave soft tissue profile; negative overjet in all anterior teeth; Angle Class III molar relationship in centric occlusion.

The number of patients in each group and mean and standard deviations of the chronological ages of the groups are shown in Table 1. Analysis of variance was used to compare mean ages of the malocclusion groups.

TABLE 1.  Statistical Comparison of Mean Ages Related to Malocclusion Groups

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Crowding was measured only in 1015 patients who were in the permanent dentition stage. Crowding was classified according to the following criteria: (1) mild: crowding up to three mm (spacing was also included), (2) moderate: crowding between four and six mm, and (3) severe: crowding more than six mm.

RESULTS

Dental arch crowding

Maxillary crowding

Distribution of maxillary crowding according to malocclusion groups is shown in Figure 1. Moderate maxillary crowding was the most common finding in all malocclusion groups. Mild maxillary crowding had the lowest frequency in Class I (21.7%) and Class II, division 2 (10.4%) malocclusion groups. Severe maxillary crowding had the lowest frequency in Class II, division 1 (15.0%) and in Class III (21.8%) malocclusions.

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Mandibular crowding

The distribution of mandibular crowding according to malocclusion groups is shown in Figure 2. Mild mandibular crowding was the most common finding in all malocclusion groups. Severe mandibular crowding had the lowest frequency in all malocclusion groups.

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Cross tabulation of maxillary and mandibular crowding

Cross tabulation of maxillary and mandibular crowding (Tables 2 and 3) regardless of malocclusion groups (Table 3) indicated that mild maxillary and severe mandibular crowding in the same patient was rarely seen (0.30%). Moderate maxillary and severe mandibular crowding in the same patient was another rare finding for all malocclusion groups (0.89%).

TABLE 2.  Cross Tabulation of Maxillary and Mandibular Crowding Related to Malocclusion Groups

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TABLE 3.  Cross Tabulation of Maxillary and Mandibular Crowding Regardless of Malocclusion Groups

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DISCUSSION

The reported prevalence of malocclusion varies from 39% to 93%.29 The prevalence of different types of malocclusions may show great variability even in a population of the same origin. Determining the criteria for normal changes from one examiner to the other and definitely affects the results of studies. Clearly, the evaluation of referred patients and the distribution of malocclusion types may give valuable information for planning an orthodontic service.

According to our results, Class I malocclusion was found in 875 (64%) of the 1356 patients examined. The frequencies of Class II, division 1 and Class II, division 2 malocclusions were 19% and 5%, respectively. Class III malocclusion was observed in 12% of the patients. The prevalence of malocclusion in a Turkish population is not well documented in the literature. Sari et al36 evaluated 1602 patients treated in the Department of Orthodontics, Selcuk University, Turkey. They reported that 61.7% of patients had Class I, 25.1% had Class II, division 1, 3.0% had Class II, division 2, and 10.2% had Class III malocclusion. Although their reported frequency of Class II, division 1 malocclusion was higher than in our study, the frequency of other malocclusion types was similar. The differences between the frequencies of Class II, division 1 can be related to the material differences. Their material consisted of patients accepted for treatment, but our material consisted a total referred population.

Jones34 investigated malocclusion and facial types in 132 Saudi Arabian patients referred for orthodontic treatment and reported that 53.8% had Class I, 28.8% had Class II, division 1, 4.5% had Class II, division 2, and 12.9% had Class III malocclusions. However, these results do not represent the prevalence of malocclusion in a referred Saudi Arabian population because of the insufficient sample size. Yang35 evaluated 3305 patients who had visited Department of Orthodontics, Seoul National University Hospital from 1985 to 1989. He reported that percentages of Class I, Class II, division 1, Class II, division 2, and Class III were 35.9%, 13.4%, 1.5%, and 49.1%, respectively. The higher reported frequency of Class III malocclusion is noticeable and may be because of the ethnic differences.

Numerous studies have been conducted to determine the prevalence of malocclusion in different populations.1–33 Proffit et al24 studied the data from the NHANES III survey and calculated the percentage of American children and youths present in Angle's four occlusion groups. They reported that 30% had Angle's normal occlusion, 50% to 55% had Class I malocclusion, approximately 15% had Class II malocclusions, and less than 1% had Class III malocclusions. A study of 1700 Danish children showed that about 14% had normal occlusion, 58% had Class I malocclusion, 24% had Class II malocclusion, and about 4% had Class III malocclusion.2 Lew et al12 evaluated 1050 ethnically Chinese children and reported that 7.1% had normal occlusion, 58.8% had Class I malocclusion, 18.8% had Class II, division 1 malocclusion, 2.7% had Class II, division 2 malocclusion, and 12.6% had Class III malocclusion. Because our study evaluated only subjects seeking orthodontic treatment, it is not surprising that Class II malocclusion was as frequent as in the Danish population and Class III malocclusion was as frequent as among the Chinese.

The type of malocclusion is an important factor that affects a patient's motivation to seek treatment. Wilmont et al37 reported that patients with a severe sagittal Class II deformity had a higher motivation for orthodontic therapy than Class III patients. In our study, comparisons of the mean ages of the malocclusion groups indicated a statistically significant difference between Class I and Class II, division 1 groups (P < .05). The lowest mean age was in the Class II, division 1 group. In accordance with Wilmont et al,37 this finding may indicate that patients with Class II, division 1 were aware of their problems earlier than those in any other malocclusion group.

Adolescence is often associated with increased self-consciousness, confusion about identity and acceptance by others, and concerns about recognition from adults and peers.38 Therefore, it is obvious that motivation for and seeking of orthodontic treatment increases in adolescence. According to our results, the mean age of the referred population was 13.57 ± 3.16 years. Therefore, we can conclude that motivation for and seeking of orthodontic treatment occurs during adolescence in a Turkish population sample.

The frequency of maxillary and mandibular crowding in different malocclusion groups may give valuable information about the characteristics of malocclusions and treatment strategies. In our study, crowding was measured only in patients with permanent dentitions to avoid the systematic errors of several mixed dentition analyses.

In the present study, moderate maxillary crowding was the most common finding in all malocclusion groups. Mild maxillary crowding had the lowest frequency in Class I (21.7%) and in Class II, division 2 (10.4%) malocclusion groups, but severe maxillary crowding had the lowest frequency in Class II, division 1 (15.0%) and in Class III (21.8%) malocclusions. Mild mandibular crowding was the most common finding whereas severe mandibular crowding was the least in all malocclusion groups. Therefore, one may think that severe crowding is not a common finding in the mandible for all malocclusion groups. This may reflect the frequency of extraction cases in a treated group. This is consistent with the findings of Sari et al36 who reported that of 1602 patients, 34.5% were treated with extraction and 65.5% were treated without extractions. Although the frequency of extraction cases has changed through the years,39 severe mandibular crowding is an important factor in the decision for orthodontic extractions.

In all types of malocclusions, cross tabulation of maxillary and mandibular crowding indicated that mild maxillary and severe mandibular crowding was rarely seen in the same patient (Table 3). Only three of 1015 patients (0.3%) showed this type of crowding, and all three had Class I malocclusions. Moderate maxillary and severe mandibular crowding in the same patient is another rare finding for all malocclusion groups. Only nine of 1015 patients (0.9%) showed this type of crowding. Therefore, our findings may be used to help predict crowding in the mixed dentition. For instance, if we know that a patient has mild crowding in the maxilla, we might not expect severe crowding in the mandible or vice versa. Similarly, if we know that a patient has moderate crowding in the maxilla, we might not expect severe crowding in the mandible or vice versa.

CONCLUSIONS

• In a sample of orthodontically referred Turkish population, Class I was the most frequently seen malocclusion, whereas Class II, division 2 was the least common.

• Comparison of the mean ages of a referred malocclusion group indicated statistically significant difference between Class I and Class II, division 1 groups. The lowest mean age was in the Class II, division 1 group.

• Mild mandibular crowding was the most common finding, whereas severe mandibular crowding was the least one in all malocclusion groups.

• Cross tabulation of maxillary and mandibular crowding indicated that in all types of malocclusions, mild maxillary and severe mandibular crowding was rarely seen in the same patient. Moderate maxillary and severe mandibular crowding in the same patient was another rare finding for all malocclusion groups.