

ORIGINAL ARTICLE 



Year : 2016  Volume
: 34
 Issue : 3  Page : 204209 

Predicting the mesiodistal width of unerupted canine and premolars by using width of the permanent mandibular incisors and first molar in the Himachal population
Sudhir Mittal^{1}, Anirudh Pathak^{1}, Kavita Mittal^{2}, Vasundhara Pathania^{1}
^{1} Department of Pedodontics, Himachal Dental College, Sunder Nagar, Himachal Pradesh, India ^{2} Department of Pedodontics, Guru Nanak Dev Dental College and Research Institute, Sunam, Punjab, India
Date of Web Publication  25Jul2016 
Correspondence Address: Sudhir Mittal Department of Pedodontics, Himachal Dental College, Sunder Nagar  175 002, Himachal Pradesh India
Source of Support: None, Conflict of Interest: None  Check 
DOI: 10.4103/09704388.186739
Abstract   
Introduction: The determination of tooth size to arch length discrepancy in mixed dentition requires an accurate prediction of mesiodistal width of unerupted permanent teeth. Presently available methods use only the mesiodistal width of mandibular incisors. Melgaco (2007) introduced a new method of estimating width of unerupted canine and premolars by using mesiodistal width of incisors and first permanent molar. Aim: The aim of this study is to determine linear regression equation for estimating the widths of mandibular permanent canines and premolars using mesiodistal width of mandibular incisors and first molars in the Himachal population. Materials and Methods: Dental casts of 250 subjects were selected from the Himachal population who had fully erupted mandibular permanent incisors, canine, premolar, and first molar. Actual mesiodistal width of all fully erupted teeth were measured with digital vernier caliper and the values obtained were subjected to statistical and regression analysis. Results: High values of correlation (0.957) were found while considering Melgaco's method. Conclusion: From this study, it can be evaluated that Melgaco's method gives better prediction of unerupted permanent canines and premolars, and the equation Y = 13.48 + 0.614X can be suggested for the present population.
Keywords: Contemporary Indian population, linear regression equation, mixed dentition analysis
How to cite this article: Mittal S, Pathak A, Mittal K, Pathania V. Predicting the mesiodistal width of unerupted canine and premolars by using width of the permanent mandibular incisors and first molar in the Himachal population. J Indian Soc Pedod Prev Dent 2016;34:2049 
How to cite this URL: Mittal S, Pathak A, Mittal K, Pathania V. Predicting the mesiodistal width of unerupted canine and premolars by using width of the permanent mandibular incisors and first molar in the Himachal population. J Indian Soc Pedod Prev Dent [serial online] 2016 [cited 2021 Jan 24];34:2049. Available from: https://www.jisppd.com/text.asp?2016/34/3/204/186739 
Introduction   
Space analysis during mixed dentition is an important aspect to supervise the development of esthetics, functionally stable occlusion, and treatment planning. It implies preventive measures that are necessary to prevent a potential irregularity from progressing into severe malocclusion. The discrepancy between the space required and space available are common condition requiring early attention. While planning a treatment for such cases, it is of utmost importance to predict the deficiency in the arch space so that the indicated procedures could be performed as early as possible.^{[1],[2]}
The first reference in the literature to attempt in the forecasting of unerupted teeth sizes are made to Black's average mesiodistal tooth size.^{[3]} Clinically, these approximations were not reliable because of great variability in tooth size among different individuals. In an attempt to obtain greater accuracy, several methods were subsequently developed by investigators to estimate mesiodistal width of unerupted permanent teeth and three methods of tooth size prediction have been proposed:^{[32]}
 Direct measurement of unerupted tooth size on radiographs.
 Calculations from prediction equations and tables.
 Combination of radiographic methods and prediction tables.
Moyer's probability tables ^{[11]} were developed at the University of Michigan based on the odontometric data of American White subjects of Northwestern European descent. Moyer's published prediction tables are based on a correlation between the sum of the width of mandibular incisors and the combined width of the mandibular canine and premolars.
All these methods are based on some of mesiodistal width of mandibular incisors only; Melgaco ^{[20]} (2007) for the first time introduced a new method by including MD width of first molar into the sum of MD width of incisors.
However, the accuracy of these prediction methods could possibly be in question when applied to other population groups because it has been well established in literature that tooth size varies considerably between the racial groups.^{[33]} Therefore, the present study aims to determine linear regression equations to predict the sum of mesiodistal width of permanent canines and premolars in the Himachal population by using permanent mandibular incisors and first permanent molar as predictor.
Materials and Methods   
An in vitro study was conducted on 250 patients between 12 years and 15 years of age attending the outpatient Department of Paediatric and Preventive Dentistry, Himachal dental college, Sundernagar.
A letter was sent to the principals of schools explaining the aim, characteristics, and importance of the study who in turn took permission from the parents of the children. Ethical clearance was obtained from the ethical board committee of the institute. All children were subjected to clinical examination at the start of the study with medical and dental histories taken.
Exclusion criteria
Children
 Belonging to different ethnic background.
 In whom all permanent teeth are not fully erupted.
 With any systemic disease or serious health problems.
 Having any restorations, proximal wear, fractures, or proximal caries.
 With hypoplasia or other dental anomalies as in number, size, and shape of the tooth.
 Undergone any orthodontic treatment.
Accurate study models were prepared by taking dental impressions of selected children with irreversible hydrocolloid alginate impression material and immediately poured with dental stone to avoid any dimensional changes.
The mandibular study cast from each patient was serialized [Figure 1]. A vernier gauge calibrated with digital micrometer with accuracy of ±0.02 mm whose measuring beaks are sharpened was used to measure the MD widths of the individual teeth (left molarright molar) from unsoaped study casts [Figure 2]. The sliding caliper was adjusted to the greatest mesiodistal diameter of the teeth, parallel to the occlusal surface, and perpendicular to the long axis [Figure 3]. All measurements were taken independently by three different observers and mean of three values was taken into consideration to rule out the individual measurement error. After taking the individual values from the study cast, the following values were calculated:
 Sum of mesiodistal width of permanent incisors only.
 Sum of mesiodistal width of permanent incisors and first molar.
 Actual sum of mesiodistal width of canine and premolars.
Values thus obtained were subjected to statistical analysis by applying Student's unpaired ttest.
Results   
Descriptive study including means, standard deviation, and minimum and maximum values were calculated; Student's unpaired ttest gave statistically significant difference (P< 0.001) between actual values of sum of mesiodistal widths of permanent canine and premolars (SCP) obtained from the study cast to the values obtained by
 Moyer's mixed dentition table.
 Using regression equation developed from sum of incisors only in the Himachal population.
High level of correlation (0.0957) was found using Melgaco's method in the Himachal population [Table 1] and [Table 2],[Table 3],[Table 4].  Table 1: Comparison of correlation and determination of coefficients in various studies
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 Table 3: Mean and Standard deviation of actual tooth width and those calculated by regression equation using sum of permanent incisors and first molar
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 Table 4: Coefficient of determination (r2) between actual sum of canine and premolar and those calculated by Melgaco method
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Discussion   
The prediction of mesiodistal dimensions of canines and premolars is of utmost significance for the prevention and interception of malocclusion. Accurate estimation of size of unerupted canine and premolars allow pedodontist to manage tooth size arch length discrepancy at a very primordial stage. Of all the methods of mixed dentition analysis reported in literature (radiographic method, regression equation, and combination of both), regression equation based on measurement from already erupted permanent teeth in early mixed dentition are most widely used.^{[30]}
Differences in tooth size is very much evident among the population of different races and ethnicity.^{[12],[13],[14]} The exact reason of tooth size variation is not clearly elucidated, but genetics followed by nutrition and environment seems to be one of the contributory factors.^{[16]} Secular trends have been seen in tooth sizes by several authors. Because of changing trends in tooth size and malocclusion, racial specific mixed dentition space analysis requires revision.^{[8],[18],[19]} The proposed new prediction aids of this study might be more accurate for tooth size prediction in the Himachal population because they were derived from contemporary odontometric data. Sexual dimorphism has also been reported to influence tooth size ^{[6],[17]} but in this study no statistical difference was found in the tooth size of males and females as reported by some authors. No differences were found between the right and left sides of lower arch.
The odontometric data chosen for the study are acceptable due to good sample size and uniform ethnicity of selected sample. Moyer has claimed that clinically acceptable width of canine and premolars is within 1 mm of the width predicted using mandibular incisors only. For the present sample, Moyer's mixed dentition analysis overestimated the tooth dimension for the Himachal population [Graph 1 [Additional file 1]], ]Graph 2 [Additional file 2]], and [Graph 4 [Additional file 3]]. From [Table 2], it could be evaluated that there is statistically significant difference between the actual sum of canine and premolars and the predicted values obtained by Moyer's analysis. Similar results were found by study conducted by Dasgupta et al. and Durgekar et al. in the Bengali and Belgaum population, respectively, while Philip et al. showed that Moyer's mixed dentition analysis underestimated the tooth size in the Punjabi population.^{[20]} This overestimation and underestimation by Moyer's mixed dentition analysis when applied to different population prompted various authors to make new probability tables for their respective population. Jaroontham and Godfrey, Schirmer and Wiltshire, and Yuen et al. have already developed probabilities for Chinese, South African, and Thai populations, respectively.^{[14],[21]}
Most of the studies have found the sum of four mandibular incisors as the best predictor for estimating the mesiodistal width of unerupted permanent canine and premolars,^{[1],[11],[31]} whereas other studies indicated that the combined width of only mandibular incisors is not a good prediction approach for mesiodistal width of unerupted permanent canine and premolars.^{[23],[24]}[INLINE:1][INLINE:2][INLINE:3][INLINE:4]
For the present study, a new regression equation for the Himachal population was used to predict the sum of canines and premolars using the width of permanent mandibular incisors and first molars. The following regression equation was used:
Y = a + bx
where Y (dependent variable) equals the predicted sum of permanent canines and premolars on both sides and x (independent variable) equals the sum of mesiodistal widths of permanent mandibular incisors and first molars on both sides. The values of constant a and b are indicated below:
Y = 13.48 + 0.614x
As mentioned earlier, no statistical difference was found due to sexual dimorphism; hence, a combined equation was proposed.
The ideal prediction method should determine no difference between predicted and actual widths of permanent canine and premolars and the standard deviation should be as small as possible. In our study [Table 2] and [Table 3], the value of mean difference between predicted values from regression equation using the sum of mandibular incisors and first molar and actual values was 0.0077. The standard deviation of difference between actual width of canine and premolars and those predicted by our regression equation is found to be 1.4332. The value of differences between predicted and actual tooth widths and standard deviations found in this study are among the smallest found in radiographic and nonradiographic methods [Graph 3 [Additional file 4]].^{[4],[10],[21],[22],[23],[25],[26]}
A high correlation was found in the present study between the predicted sum of canines and premolars and those obtained by regression equation using the sum of mandibular incisors and first molars (r = 0.95), which is comparable with the findings of Bernabe and Floris Mir,^{[23]} Melgaco et al.,^{[15]} and Shah et al.^{[29]} The coefficient of correlation obtained in this study was higher than that reported in other studies where only mandibular incisors were used for prediction.^{[14]} Staley and Keber ^{[27]} and Hixon and Oldfather ^{[9]} used the combination of both radiographs and study models for predicting the size of unerupted canine and premolars and found a very high correlation between them. Lima Martinelli et al.^{[28]} who used 45° oblique teleradiographs of left side of face in mixed dentition period and dental casts of permanent dentition for predicting the mesiodistal widths of canines and premolars, found a very strong correlation (r = 0.84). The results of the present study are in reasonable agreement with their findings.
The relatively consistent correlation of 0.70.8 suggests that the sum of mandibular incisors and first molar is the better predictor of the sum of permanent canine and premolars in present population. It means 7080% of polygenes that determine the tooth size are shared between the mandibular incisors and molars and canines and the premolars.^{[7]} The common genetic code determining tooth sizes of different morphologic classes gives the theoretical justification for the estimation of width of unerupted permanent teeth according to the width of already erupted teeth from another morphologic class, as suggested by Moyers.^{[5]}
Coefficient of determination (r^{2}) that indicates the predictive accuracy of regression equations were between 0.50 and 0.95 for canine and premolar regions [Table 4]. This means that 5095% of total variance in caninepremolar widths are accounted for by knowing the sum of mandibular incisors and first molar. This value is higher than those obtained by other studies.^{[17],[20]} These higher values indicate the applicability of this proposed simple regression equation to present representative sample of contemporary Indian children.
As Moyers prediction table overestimated the tooth size for the Himachal population, a regression equation using the width of mandibular incisors was developed that is as follows:
Y = 26.63 + 0.619 X
The correlation coefficient with this equation was found to be 0.566 that is contrast to the values obtained by Moyers prediction table (r = 0.33). The accuracy of these equations should be tested in larger sample size from various ethnic groups in India to further generalize its applicability.
Conclusion   
Based on the results of this study we can conclude that
 The simplified equations proposed are easy to use and seem to be a practical and precise method for predicting the mesiodistal width of unerupted canine and premolars.s
 Including MD width of first molar into the sum of MD of incisors gives more accurate value of unerupted canine and premolar as compared to other methods available.
 The regression equations proposed in this study are good prediction method to determine width of unerupted permanent canine and premolars.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]
