
Year : 2013  Volume
: 31  Issue : 1  Page : 3642 Validation of Tanaka and Johnston's analysis in western UP Indian population B Srivastava, HP Bhatia, R Singh, AK Singh, A Aggarwal, N Gupta Department of Pedodontics and Preventive Dentistry, Santosh Dental College and Hospital, NCR, Delhi, India Correspondence Address: Objective: To examine the applicability of the Tanaka and Johnston«SQ»s method of prediction in a western UP population and to develop a new prediction method for this specific population if necessary. Materials and Methods: 150 western UP school children (87 males and 63 females) with a mean age of 15.5 years were randomly selected. The mesiodistal crown diameters of the permanent canine and premolars were measured and comparisons were done between the actual tooth sizes and the values predicted by the Tanaka and Johnston method. Results: Significant sexual dimorphism was found in the tooth sizes. There were significant differences between the actual measurements and the predicted measurements derived by the Tanaka and Johnston prediction method. New linear regression equations were derived for both the genders for tooth size prediction in western UP population. Conclusion: There are limitations in the application of the Tanaka and Johnston«SQ»s prediction method to a western UP population. A gender discrepancy is seen between the males and the females. New regression equations were formulated for both the males and the females separately.
Introduction It is believed in orthodontic circles that a large number of cases of malocclusion start during the mixed dentition stage, which spans an interval from 6 th to 12 th year of life. Many of these developing malocclusions may be reduced in severity or eliminated entirely by timely management. [1] The period of late primary dentition or early mixed dentition is a critical period for the prevention or interception of any developing malocclusion. Moreover, treatment of malocclusion in the period of active growth is more advantageous because of the opportunities for occlusal guidance, interception of malocclusion, or removal of etiological factors . [2] Mixed dentition space analyses form an essential part of early orthodontic evaluation. They help to determine the amount of space available, whether in the maxillary or in the mandibular arch, for the accommodation of unerupted permanent teeth, usually canine and premolars. An accurate mixed dentition analysis is an important criterion in determining whether the treatment plan may involve serial extraction, guidance of eruption, space maintenance, space regaining, or just periodic observation of the patient. [1] Three basic approaches for the prediction of the size of the unerupted permanent teeth during mixed dentition have been used: 1) measurement of the size of the unerupted teeth on radiographs, as recommended by Staley et al., 2) estimation from proportionality tables, as reported by Moyers and Tanaka and Johnston, and 3) a combination of the radiographic and prediction table method, as recommended by Hixon and Oldfather. [3] Tanaka and Johnston method has several advantages such as no radiographs are required, it is a simple and easy method, [4] it can be used for both maxillary and mandibular arch estimations, [3] and for both genders, [4] and there is a fairly good accuracy. [3] However, the development of this method is based on data derived from a population of Northern European descent; therefore, the accuracy of this prediction method may be in question when applied to a population of different ethnic origin. Also, there have been questions about applying these methods which are based on pooled male and female data rather than considering the sexes separately. In addition, there has been some evidence of secular trends of changing dimensions of teeth, which may require progressive modification of mixed dentition analysis for different populations. [3] Considering the above facts, the present study was designed to 1) examine the accuracy of Tanaka and Johnston method of prediction in a western UP Indian population and 2) to provide a more accurate formula for predicting the widths of canines and premolars for the specific population if necessary. Materials and Methods Sample selection The sample comprised 150 UP adolescents (87 males and 63 females) randomly selected from the students of 9 th to 12 th grade of western UP schools, with a mean age of 15.5 years (1417 years), who fulfilled the following inclusion criteria: UP ancestors at least from one previous generation,All permanent teeth erupted (except third molars),No interproximal caries or restorations,No missing or supernumerary teeth,No abnormally sized or shaped teeth,Minimal or no tooth wear, andNo history of previous orthodontic treatment.Alginate impressions were made using standard procedures for material mixing as recommended by the manufacturer. The impressions were rinsed in running water and were disinfected with 2% glutaraldehyde. The impressions were poured on the same day with hard dental stone using standard procedure for mixing. The dental casts were not soaped or waxed. Method Measurements were made with vernier caliper with a digital micrometer (Aerospace, China) [Figure 1] with an accuracy of + 0.01 mm directly on the unsoaped dental casts using a digital vernier caliper. The maximum mesiodistal widths of the canine and the first and second premolars were measured from anatomical mesial contact point to anatomical distal contact point for each tooth. The caliper was held at the tooth's greatest mesiodistal diameter (contact points), parallel to the occlusal surface, and perpendicular to the long axis of the tooth. All the readings were taken thrice and their mean was calculated and used for precision of further statistical analysis. All the measurements were made by a single operator to avoid interoperator errors [Figure 2].{Figure 1}{Figure 2} Statistical analyses Statistical analysis was carried out using statistical package for social sciences (SPSS) software (version 16.0). Paired ttest was used to calculate difference between the mean values. The correlation between the two variables was calculated using the Pearson's correlation coefficient and the regression analysis was used for computing the value of the constants. The level of significance was taken at 5% (P<0.05). Results Coefficient of variation (CV)=(SD÷mean)×100% d (difference)=male m.d.female m.d. Percentage sexual dimorphism=(male m.d.÷female m.d.)1×100% Rank is the ranking of percentage sexual dimorphism from highest (1) to lowest (10) [Table 1] presents the descriptive statistics for the sample. The mean value of the mesiodistal width of teeth for males was found to be greater than the mean value of the mesiodistal width of the females.{Table 1} Sexual dimorphism was evident in the mesiodistal tooth dimensions of the western UP males and females for permanent central incisors, canines, and premolars. The largest percentage of sexual dimorphism of the mesiodistal tooth dimension of western UP sample was the mandibular canine (4.59%) followed by the maxillary central incisors (4.20%), and the least percentage of sexual dimorphism was in the maxillary 1 st premolars (1.84%) [Graph 1]. [INLINE:1] [Table 2] and [Table 3] show statistically significant differences observed between the measured values from this western UP sample and the Tanaka Johnston prediction values for the mandibular and maxillary arches for males and females, respectively [Graph 2].{Table 2}{Table 3} [INLINE:2] Computation of the prediction formulas The foundation of this mixed dentition analysis was based on the moderate correlations between the sums of the mandibular incisors and the sums of canine and premolars in both arches. Linear regression equations such as least squares regression equation of the form y=a+b (x) were calculated. The term "y" equals the predicted size of the unerupted canines and premolars, "x" equals the measured combined mesiodistal dimensions of the four lower incisors, and "a" and "b" are constants. The term "b" was suggested to be half. To analyze the mixed dentition analysis, the following mesiodistal dimensions were summed and computed: Sum 1=m.d. 12+m.d. 11+m.d. 21+m.d. 22 Sum 2=m.d. 31+m.d. 41+m.d. 32+m.d. 42 Sum 3=m.d. 43+m.d. 44+m.d. 45 Sum 4=m.d. 33+m.d. 34+m.d. 35 Sum 5=m.d. 13+m.d. 14+m.d. 15 Sum 6=m.d. 23+m.d. 24+m.d. 25 Sum 7=0.5×(Sum 3+Sum 4) Sum 8=0.5×(Sum 5+Sum 6) x=Sum 7  0.5 (Sum 2) y=Sum 8  0.5 (Sum 2) The results of the means, standard deviation, standard error of means, and correlation coefficients of the abovementioned equations are shown in [Table 4] and [Table 5].{Table 4}{Table 5} The calculated constants for the western UP population were as follows: Male upper constant, A mu =9.6 mm Male lower constant, A ml =9.3 mm Female upper constant, A fu =9.4 mm Female lower constant, A fl =8.9 mm The accuracy of the prediction is often expressed as the standard error of determination (mean) for the prediction equations. In this study, the standard error of estimates (mean) ranged between 0.72 and 0.90 mm for male, female, and combined groups. The Pearson product moment correlation coefficients (r) can be put into clinical orthodontic use by constructing regression equations for the western UP sample. The regression equations of the obtained prediction equations for the western UP sample are: For the combined population: For maxilla: y=9.52+0.42x For mandible: y=9.12+0.49x For the males: For maxilla: y=9.6+0.40x For mandible: y=9.3+0.42x For the females: For maxilla: y=9.4+0.37x For mandible: y=8.9+0.46x Discussion Prediction of the mesiodistal dimensions of unerupted permanent canines and premolars during mixed dentition is of clinical importance in diagnosis and treatment planning. Accurate estimation of the size of canines and premolars allows the dentist to better manage tooth size / arch length discrepancies. There have been a few studies investigating a mixed dentition analysis in schoolaged children. [4],[5],[6] The age of the sample was relatively younger in order to eliminate and minimize the influence of tooth wear and loss. Considering the above facts, this study has been planned and executed in our department with the study sample of 150 western UP 10 th to 12 th grade school children. Studies have demonstrated that the mesiodistal tooth dimensions are, to a large extent, gene determined. Environmental variables, such as nutrition, disease, and climate, affect the dentition during the prenatal period but seem to have little influence on normal dental variation. [7] In the present study, the ancestry of the study sample was established to one previous generation. Sexual dimorphism [Table 3] was evident in the mesiodistal tooth dimensions of the western UP males and females for central incisors, canines, and premolars. The largest percentage of sexual dimorphism of the mesiodistal tooth dimension of western UP sample was the mandibular canine (4.59%) followed by the maxillary central incisors (4.20%), and the least percentage of sexual dimorphism was in the maxillary 1 st premolars (1.84%). This sexual dimorphism has been seen in other studies; [4],[5],[8],[9] however, other investigators did not consider gender differences. [10],[11] In this study, sexual dimorphism was indeed found. Division of subjects according to sex when performing mixed dentition analysis was therefore necessary. Different racial and ethnic groups can have variations in the tooth and facial characteristics. This has been demonstrated in the present study [Table 5] by significant amount of differences between the mean values of actual mesiodistal widths of permanent canines and premolars and those derived from Tanaka and Johnston's prediction equations for children from northwestern European ancestry. [5] Therefore, the Tanaka and Johnston method (1974) cannot be used accurately to estimate the combined mesiodistal widths of unerupted permanent canines and premolars in every population group. Tanaka and Johnston's (1974) method of prediction showed an overestimation of the mesiodistal tooth widths in the western UP Indian population. Based on this information, new regression constants were determined for the western UP Indian population. New regression equations were formulated and the values of "a" and "b" constants were also determined. Conclusion Based on the outcome, the following conclusions were made: There are limitations in the application of Tanaka and Johnston's prediction method to a western UP Indian population.A gender discrepancy was seen in the present study with male subjects having significantly larger mesiodistal tooth widths as compared to the female subjects.To predict the space (in mm) required for alignment of unerupted canines and premolars in western UP children, new regression equations have been formulated. References


