|Year : 2014 | Volume
| Issue : 2 | Page : 62-65
Estimating the size of unerupted canine and premolars in a mixed Indian population
Abhijeet Kadu1, S. M. Londhe1, Prasanna Kumar1, Sanjeev Datana1, Madhu Singh1, Neetu Gupta2
1 Department of Orthodontics, Army Dental Centre (Research and Referral), Delhi, India
2 Department of Public Health Dentistry, Sudha Rustagi Dental College, Faridabad, Haryana, India
|Date of Web Publication||5-Jun-2014|
Department of Orthodontics, Army Dental Centre (Research and Referral), Delhi
Source of Support: None, Conflict of Interest: None
Introduction: This study was carried out to determine the correlation between the sum of the mandibular permanent incisors and the combined mesiodistal crown diameters of the maxillary and mandibular canine and premolars in a sample of mixed Indian subjects, examine the applicability of the Tanaka and Johnston method of prediction in a mixed Indian population and develop a new prediction method for this specific population. Materials and Methods: The dental models of the dentition of 251 mixed Indian patients below the age of 21 years, who had upper and lower permanent canines and premolars erupted were selected for this study. All the measurements were made by an observer with modified Boley gauge with Vernier caliper. Results: The differences between the predicted widths of the canine and premolars with the Tanaka and Johnston equations and the actual widths were highly statistically significant, as indicated by t-tests. The actual widths of the maxillary canine and premolars showed a significant difference in size (P = 0.0001) from the widths predicted by the Tanaka and Johnston equation, as did the canine and premolars in the mandible (P = 0.0003). Conclusion: The current findings suggest that the accuracy of originally derived Tanaka and Johnston mixed dentition analysis method can be increased using a newly derived regression equations based on a local mixed Indian population.
Keywords: Mixed dentition, mixed Indian population, Tanaka-Johnston
|How to cite this article:|
Kadu A, Londhe SM, Kumar P, Datana S, Singh M, Gupta N. Estimating the size of unerupted canine and premolars in a mixed Indian population. J Dent Res Rev 2014;1:62-5
|How to cite this URL:|
Kadu A, Londhe SM, Kumar P, Datana S, Singh M, Gupta N. Estimating the size of unerupted canine and premolars in a mixed Indian population. J Dent Res Rev [serial online] 2014 [cited 2021 Mar 3];1:62-5. Available from: https://www.jdrr.org/text.asp?2014/1/2/62/133933
| Introduction|| |
Early treatment is becoming increasingly popular in contemporary practice of orthodontics due to increased oral health awareness and increased availability of specialized care. It is imperative that a mixed dentition analysis should be carried before orthodontic treatment is offered.  One of the prominent conditions requiring early orthodontic treatment includes crowding. This results from a disparity between the available dental arch space and amount of total tooth material.  To plan effective future management it is necessary that any discrepancy between tooth size and arch length be predicted in advance; this can be achieved with a mixed dentition analysis. Mixed dentition analysis helps to determine whether the treatment plan should involve space maintenance, space regaining, guidance of eruption, serial extraction or periodic observation of the patient. 
Tooth size prediction of the unerupted permanent canines, first and second premolars forms part of the critical aspects of the mixed dentition space analysis. Three main approaches have been used to estimate the mesiodistal crown widths of the permanent canines and premolars in the mixed dentition patients:
- Measurement of the unerupted teeth on the radiographs ,,
- Use of a regression equations that relates to mesiodistal width of erupted teeth to the mesiodistal width of unerupted teeth ,
- A combination of measurements from erupted teeth and radiographs of unerupted teeth. ,
The most accurate predictions of the mesiodistal widths of unerupted canines and premolars can be obtained by measurements of mesiodistal widths of these teeth on radiographs combined with measurement of mesiodistal widths of the erupted mandibular permanent incisor teeth. ,
Most commonly used nonradiographic methods are derived from particular ethnic population as a Caucasian population and population of Northern European descent.  There are certain nonradiographic methods based on the Indian population, but they address population of certain regions and ethnic predisposition. ,
The purpose of this investigation is to: (1) Determine the best correlation between the sum of the mandibular permanent incisors and the combined mesiodistal crown diameters of the maxillary and mandibular canine and premolars in a sample of mixed Indian subjects; (2) examine the applicability of the Tanaka and Johnston method of prediction in a mixed Indian population; and (3) develop a new prediction method for this specific population, if any of the correlations obtained in this study prove to have an advantage over presently used methods.
| Materials and Methods|| |
The dental models of the dentition of 251 mixed Indian patients, who presented with complete eruption of permanent mandibular incisors, canines, and premolars, as well as maxillary canines and premolars, were obtained from the population of patients seen at the tertiary care dental center for Central Government employees. The criteria for selection were based on complete fulfillment of the following: (1) The patient had to be of Indian background for at least one prior generation, that is, both parents to be of Indian origin, (2) the dental casts should to be of high quality and free of distortions, (3) the teeth measured should be free of restorations, fractures, or proximal caries, (4) there should be no evidence of hypoplasia or anomalous form of the teeth being measured, and (5) a maximum of 21 years of age was used to preclude any discrepancies based on significant proximal wear.
The measuring device
The mesiodistal width of a tooth was obtained by measuring the greatest distance between contact points on the proximal surfaces. A modified Boley gauge with a Vernier scale to read to the nearest 0.1 mm was held parallel to the occlusal surface if the tooth appeared to be in normal alignment. Otherwise, the mesiodistal crown diameter was obtained by measuring between the points where contact with the adjacent tooth would normally occur.
The teeth measured were the mandibular permanent central and lateral incisors, the maxillary and mandibular permanent canines, and the maxillary and mandibular first and second premolars. All teeth involved in this study were measured by the same investigator. Values obtained for the right and left posterior segments were averaged, so that there would be one value for the maxillary canine and premolars and one value for the mandibular canine and premolars for each value of the mandibular incisors.
Intra-observer measurement reliability
The investigator took repeated measurements of the mandibular incisors of 30 random casts from the sample. The second measurements were taken 2 weeks after taking the initial measurements to reduce memory bias. Correlation of the first and second measurements was calculated to determine the measurement reliability. The correlations were all very high, ranging upward from r = 0.95. All subsequent measurements on the orthodontic patient sample were taken only once, to simulate the conditions in an orthodontic practice. The magnitude of method of error was found to be 0.5 mm.
The current study tested the Tanaka and Johnston prediction method currently being used on the white population for the mixed Indian orthodontic patient samples. In this method, the sum of the mesiodistal widths of the four mandibular incisors were correlated with the sum of the mesiodistal diameters of the mandibular and maxillary canines and premolars for both the right and left sides in study sample. The Tanaka and Johnston regression equations are as follows:
for the mandibular canine-premolar segment, and
for the maxillary canine-premolar segment,
where Y = the estimate of the sum of the mesiodistal widths of the unerupted canines and premolars on either the right or left side and X = the sum of the mesiodistal widths of the four mandibular incisors. The difference between the predicted widths of the canine and premolars and the observed widths of the canine and premolars was tested for significance with the paired t-test with an alpha level equal to 0.05 as the data was normally distributed. By using the data obtained, the range, the mean, and the standard deviation of the tooth groups were computed and regression equations of the form were formulated to be used clinically for the prediction of tooth size in a similar Indian population. The standard error of the predicted maxillary and mandibular values for each value of the sum of the mandibular incisors was also calculated.
| Results|| |
The range, mean, and standard deviations for the three groups of teeth measured are presented in [Table 1]. In the sample, the mandibular incisor widths range from 19.64 mm to 25.88 mm.
|Table 1: Descriptive statistics for combined MDWs and comparison of estimated and measured width (in mm) |
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The differences between the predicted widths of the canine and premolars with the Tanaka and Johnston equations and the actual widths were highly statistically significant, as indicated by t-tests. The actual widths of the maxillary canine and premolars showed a significant difference in size (P = 0.0001) from the widths predicted by the Tanaka and Johnston equation, as did the canine and premolars in the mandible (P = 0.0003) [Table 1]. The values of mesiodistal widths of unerupted canine and premolars in both arches were overestimated in Indian population.
The regression equation was used to establish correlation between sum of mandibular incisors and the measured mesiodistal width of maxillary and mandibular canine, first premolar and second premolar. The coefficient of correlation was found to be r = 0.658 and r = 0.663 for maxillary and mandibular teeth, respectively. Coefficients of correlation for the canine-premolar segments of each dental arch, the values of A, B for the two regression equations and the standard error of estimate are summarized in [Table 2].
| Discussion|| |
The current study states that the t-tests between the predicted widths derived from the Tanaka and Johnston equations and the actual measured widths from the study casts of the Indian patients showed significant differences in both the maxillary and mandibular arches (P = 0.0001 and 0.0003, respectively). The Tanaka-Johnson equation tends to overestimate the size of unerupted canine, first premolar and second premolar for both the arches in Indian population. The correlation coefficients for these equations are: Maxillary r = 0.658 and mandibular r = 0.663, with standard errors of 0.454 mm and 0.563 mm, respectively. These values are almost identical to those of Tanaka and Johnston's study (r = 0.625, 0.648, with standard error of 0.850 mm).  The moderately high degree of linear correlation that exists between the sum of the mandibular incisors and the maxillary/mandibular canine-premolar segments makes it possible to measure the total width of the permanent mandibular incisors and to predict the size of teeth that are unerupted. The current data were used to generate regression equations that can be used clinically in tooth size predictions in much the same way as the Tanaka and Johnston equations. Specifically, significantly different regression equations were derived and simplified for the size prediction of maxillary and mandibular canines and premolars in an Indian population:
X = Mesiodistal width of the four mandibular incisors in millimeters.
Y = Mesiodistal width of the canine and premolars in one quadrant in millimeters.
The different results obtained could be due to the differences in the ethnic origins of the samples, as al-Khadra  also found different results when applying the Tanaka and Johnston method to the Saudi Arab population. Similar findings were shown in studies carried out in India on South Indian and North Indian population by Sholapurmath et al.  and Srivastava et al.  respectively. The research to date, as well as this study, supports the view that racial differences are likely to be important variables in tooth size prediction equations. The results of this study indicate that the currently popular prediction method, the Tanaka and Johnston equations, would not be as accurate when used in a mixed Indian population. Further study with a larger sample size is indicated to confirm these findings and the newly derived equations.
| Conclusion|| |
The current findings suggest that the Tanaka and Johnston prediction method used in its original form is not accurate when applied to a population of mixed Indians. The newly derived regression equations may be more clinically relevant in a mixed Indian population for tooth size predictions.
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[Table 1], [Table 2]