Occlusal status among Yemeni children

Subjects

The sample consisted of 3003, 12-year-old children attending schools in six governorates (cities and environs) in Yemen. In each governorate the same multi-stage stratified sampling technique was implemented. From each sector, 500 children were included in the survey, half of whom (250 children) were urban and the other half were rural.

Urban children were considered as those living in the center of each governorate taken as clusters of 25 students from 10 randomly selected schools. Rural children were selected from five small villages from each sector, two clusters of 25 students from each village.

This gives a total of 3000 examined children taken from 120 schools; half of whom were males (1500 students from 60 schools) and the other half were females 1500 students from 60 schools).

From each school, the first accessible 25 children were examined. Thirteen schools did not have 25 children 12-year of age so neighboring schools were visited to complete the required number making the total number of visited schools 133.

Permission was obtained from the general directorate of education in Yemen and the regional directorate of education in the governorates. All school authorities were contacted and the purpose of this study was explained to them to ensure full cooperation.

Methods

Statistical analysis

All statistical analyses were performed using SPSS 13.0, IBM Corporation, New York, NY. Pearson’s Chi-square test was used to test the differences between gender urbanization and dentition stage. Statistical significance was set at (P < 0.05).

The prevalence of dentition stage

Division of the sample in the late mixed dentition stage and early dentition stage indicated that 26.1% of the study population are still in the late mixed dentition stage and 73.9% presented with a dentition in the early permanent stage [Figure 1]. The results indicated that there are more 12-year-old girls presenting with a dentition in the early permanent stage than boys, 77.61% and 70.11%, respectively. The distribution of the number of males and females in the two stages of dental development was statistically significant different (P < 0.05).

Close

Figure 1

Distribution of the sample according to gender and dentition stage

Export to PPT

Intra-arch irregularities and malalignment

Table 1 depicts the distribution of intra-arch irregularities according to gender, residency and dentition stage. Of the whole sample, 31.4% presented with crowding either in one dental arch or both (maxillary and mandibular), whereas 24.3% presented with spacing either in one dental arch or both (maxillary and mandibular).

Crowding was more prevalent in urban children than rural children, and the difference was considered as statistically significant (χ² = 10.969, df = 1, P = 0.0004).

Maxillary midline diastema

Of the 3003 children examined, 426 or 14.2% presented with maxillary midline diastema of 1 mm or more. If spaces >2 mm are taken into account, 1.8% of the children presented with diastema. Considering gender differences, diastema was found to be almost equally distributed between males and females. If diastema larger than 2 mm is taken into account, about twice as many females (2.6%) than males (1.3%) presented with diastema, the difference between gender was statistically significant (P < 0.05), there are more girls than boys with a midline diastema larger than 2 mm. The results for the interaction of dentition stage and midline diastema larger than 2 mm indicated that midline diastema is more prevalent in the late mixed dentition than in the early permanent dentition (P < 0.05).

Discrepancies in occlusal contact relationship

Intra-arch irregularities and malalignment

The majority of the sample 73.9% presented with a dentition in the early permanent stage. Most 12-year-old children will present with a dentition in the early permanent dentition stage, and the remainder will still be in the late mixed dentition stage.^[26,27] A considerable number of 12-year-old girls presented with a dentition in the early permanent stage than boys. This is in accordance with the finding of Johnson and Harkness^[28] and Drummond.^[29]

The prevalence of crowding in this study was much higher than that of Al-Huwaizi^[23] in his 13 year old Iraqi sample. The reason for this may be the difference in the criteria used as he recorded space discrepancies ≥2 mm. However, it was lower than that of Abdulla^[17] and Batayine^[18] in their Iraqi and Jordanian samples respectively and of Drummond^[29] in his 12 year old South African sample.

This study revealed nonsignificant differences between the two genders concerning the distribution of crowding. This coincides with the findings of Al-Huwaizi,^[23] while it contradicts that of Salonen et al.^[30] who found that females had more crowding than males, which may be attributed to sample size, age group and racial variation. However this study reveals an insignificant difference in the prevalence of crowding between the late mixed dentition stage and the early permanent dentition stage.

The slight increase in the anterior arch dimension during normal development is not sufficient to overcome moderate to severe discrepancies. Crowding is therefore likely to persist into the permanent dentition, particularly if it was severe initially.^[27]

One of the characteristic features of normal occlusion is arch continuity as expressed by proximal contact between all teeth in each dental arch. Factors such as mesial drift, transeptal fibers, the slope of the occluding cusp and the direction of occlusal forces contribute to the maintenance of this continuity.^[31-33]

A comparison with other studies on spacing is difficult because of the differences in the age of the samples, criteria and method used to assess the space discrepancy. The Yemeni figure for maxillary central diastema is close to that of other Arab population sample results^[17,18] and African population results,^[29] but higher than that of Swedish population results^[34,35] and this may be attributed to racial differences. There are more girls than boys with a midline diastema larger than 2 mm. These coincide with the findings of Drummond.^[29]

On the other hand, Brunelle et al.^[36] found that males had significantly more diastemas than females. Midline diastema is more prevalent in the late mixed dentition than in the early permanent dentition. This was also true for a midline diastema larger than 2 mm. The result of this study supports the findings by Richardson et al.^[37] and Lindsey^[38] who indicated that midline diastema reduces with the transition from the mixed dentition to the permanent dentition.

Discrepancies in occlusal contact relationship

The mean maxillary overjet of the sample was 2.9 mm, which was smaller than those found by many previous studies,^[17,18,22] but was near to the finding of Al-Huwaizi^[23] and Corruccini and Lee.^[39]

Concerning gender differences, there are more boys than girls had an increased overjet that is, overjet >3 mm and significantly more girls than boys had an edge-to-edge overjet (0 mm overjet). This implies that 12-year-old boys have larger overjets and a higher prevalence of Class II malocclusions.

Furthermore, 12-year-old Yemeni girls tend to have fewer overjets larger than 3 mm and a higher prevalence of edge-to-edge overjet indicating a tendency toward Class III malocclusion. Furthermore, there are more 12-year-old children presented with a normal overjet in the early permanent dentition stage than 12-year-old children in the late mixed dentition stage. In other words, there is a higher prevalence of normal (1-3 mm) overjet in 12-year-old children in the permanent dentition stage than in the mixed dentition stage. Certain occlusal indicators including overjet, naturally improves with age.^[36]

The differences between the prevalence of mandibular overjet of the present study and those reported by other investigators is difficult because of the differences in the age of the sample, criteria and method used to assess mandibular overjet in addition to possible racial variation. Anterior mandibular overjet that is, Class III malocclusion or anterior crossbite, is more prevalent in the late mixed dentition stage than in the early permanent dentition stage. Of the children, 8.3% presented with anterior openbite, in a malocclusion study in Nigeria, on 12- to 13-year-old children, Otuyemi et al.^[40] have reported that anterior openbite is a common malocclusion trait, and that it occurs in 10.2% of the rural and urban Nigerian communities.^[40]

Anterior openbite is more prevalent in the late mixed dentition stage than in the early permanent dentition stage especially among females compared with males. These improvements may be due to normal developmental changes and growth that occur during the transition from the mixed dentition stage to the permanent dentition stage.

The majority of the sample (69.4%) presented with a normal molar relationship, and this figure fell within the range of previously given prevalences (40-86.8%). It was also comparable to the figures given by several authors.^{[6,12,18,23,30,39]}

Girls presented with more normal molar relationship than boys. This finding is in agreement with that of Drummond,^[29] but it contradicts with that of Al-Huwaizi;^[23] who found statistically insignificant difference between the two genders. The distribution of antero-posterior molar relation showed no statistically significant relation with residence. This finding is in agreement with that of Al-Huwaizi^[23] and Ast et al.^[41] While Salonen et al.^[30] found that abnormal molar relation was more in urbans than rurals, and the result was statistically significant.