Comparison Of Measured And Predicted Mesiodistal Tooth-widths Of 13-17 Year Old Kenyans
Background: Odontometric measurements are important in the determination of the space discrepancies in the dental arches. In clinical orthodontics, odontometric measurements are done to determine the arch perimeter and total tooth mass. In permanent dentition the odontometric measurements are straightforward. However, in the mixed dentition analysis, it is a great challenge to accurately determine the mesiodistal tooth-widths of unerupted permanent canines and premolars. Various methods have been proposed and used in different ethnic groups. They fall into three main categories; radiographic method, use of regression/prediction equations and a combination of radiographic method and regression equations. The most widely used prediction equations are the Tanaka and Johnston equation and the Moyers prediction tables. However, they have their shortcomings. This has necessitated the proposal of different prediction equations for use in various ethnic groups. Objectives: To measure mesiodistal tooth-widths of permanent teeth in both the upper and lower dental arches from first molar to first molar, to estimate the mesiodistal tooth-widths of permanent canines and premolars using two prediction equations and to compare the measured values with values obtained using the two prediction equations. Materials and methods: A descriptive cross-sectional study was carried out on 13- 17 year old Kenyans in two secondary schools. Maxillary and mandibular arch impressions were made using irreversible hydrocolloid impression material and the impressions were then poured with type III dental stone. An electronic digital vernier calliper was used to measure the mesiodistal tooth-widths from the first molar to the antimeric first molar for both arches. Measurements were entered on a data collection form and later transferred to Microsoft Excel software. Statistical Package xii for Social Sciences (SPSS) version 14.0 for Windows was used for data analysis. Paired t-tests, independent t-tests and Pearson product moment correlation tests were used to analyse the data. Data were presented in the form of tables (Table 3.1 to 3.18) and graphs (Figures 3.1 to 3.5). The Tanaka and Johnston and Melgaço et al prediction equations were used to estimate the mesiodistal tooth-widths of the permanent canines and premolars and these values were compared with the measured values. Results: Sixty eight subjects (28 males and 40 females) of mean age 14.89 ± 1.23 years (males) and 14.65 ± 1.21 years (females) were included in this study. Intraclass coefficient was 0.99 and it was used to assess the accuracy of measurements. The male subjects had larger mean mesiodistal tooth-widths than female subjects. Statistically significant differences in mean mesiodistal tooth-widths were found in the mandibular and maxillary canines, first permanent molars and the maxillary lateral incisors. Except for the mandibular second premolar and the maxillary first permanent molar, the male sample showed no statistically significant differences between antimeric teeth. There were statistically significant differences between antimeric mandibular first and second premolars and the maxillary first permanent molar for the female sample. There were no statistically significant differences in the antimeric sum of mesiodistal tooth-widths of the permanent canine and premolars for both the mandibular and maxillary arches in males. However, in females both the mandibular and maxillary arches had statistically significant differences. Inclusion of the two first permanent mandibular molars to the four permanent mandibular incisors as predictor teeth gave higher correlation coefficients than the use of only four permanent mandibular incisors. The Tanaka and Johnston equation was useful as a prediction equation for the female maxillary arch and in the combined sample. The xiii Melgaço et al equation could be used as a prediction equation in the mandibular arch for males, females and the combined sample. There were no statistically significant differences in the sum of mesiodistal tooth-widths of the mandibular permanent canine and premolars between the actual and predicted values obtained using both the Tanaka and Johnston and Melgaço et al equations. There were no statistically significant differences in the calculated/predicted value of the sum of mesiodistal tooth-widths of the mandibular permanent canine and premolars obtained using the Tanaka and Johnston and Melgaço et al equations. However, the Melgaço et al equation had a correlation coefficient of 0.693 and the Tanaka and Johnston equation correlation coefficient was 0.465 for the sum of mesiodistal toothwidths of the mandibular permanent canine and premolars and the predictor teeth. Conclusion: Males had larger mean mesiodistal tooth-widths than females. The Melgaço et al equation predicted better the sum of mesiodistal tooth-widths of the mandibular permanent canines and premolars than the Tanaka and Johnston equation but had lower correlation coefficients compared to the original sample from which it was derived. However, the Melgaço et al equation overestimated the mesiodistal tooth-widths for the female and combined samples and under-estimated for the male sample but the differences were not clinically significant. Recommendation: Male and female mesiodistal tooth-widths should be calculated/estimated separately. The prediction equations formulated from this study should be used in predicting the sum of mesiodistal tooth-widths of mandibular permanent canines and premolars in Kenyan populations.