A study of permanent second and third molars in determining the optimal time for orthodontic intervention among Malay population using radiographs

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Date
2013-04
Authors
Q. A. Alawaj, Khaled
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Publisher
Universiti Sains Malaysia
Abstract
Background: Early intervention such as extraction of poor prognosis first permanent molars (FPMs) during the optimal time and treatment with functional appliances are essential in orthodontic management. Aim: To determine the ideal age range for extraction of poor prognosis FPMs and peak mandibular growth using orthopantomogram radiographs (OPG) in Malay population. This study also compared the chronological age of crypt stage developmental of each third molar between genders, upper and lower jaw, right and left in each jaw. Methods: This retrospective cross-sectional study was done on 641 Malay subjects, 289 males and 352 females, ranging from 7 to 16 years of age. Dental maturity of the permanent mandibular second molar and third molars were assessed from OPG radiographs by using calcification stages of Demirjian et al., (1973) method, whereas skeletal maturity was evaluated from lateral cephalogram by cervical vertebral maturation (CVM) stages of Baccetti et al., (2005) method. Descriptive statistic was obtained by calculating the mean and standard deviations of the chronological age for the crypt stages of third molars (stage 0), right permanent mandibular second molar (stage E) development and stages of CVM. Spearman rank order correlation coefficient was used to assess the relationship between CVM and permanent mandibular second molar stages. Results: The mean age of calcification at stage 0 for upper third molar was 10.48 and 11.88 years while, lower third molar was 9.78 and 10.85 years for male and female respectively. The mean age of calcification at stage E for permanent mandibular second molar was 10.50 years and 10.67 years in males and females respectively. The mean and standard deviation of the chronological age in years for cervical vertebral maturation stages from CS1 to CS6 were, 9.70 (SD 1.87), 10.61 (SD 1.92), 11.09 (SD 1.51), 12.78 (SD 1.53), 13.29 (SD 1.46) and 14.73 (SD 0.77) respectively for males, and 9.83 (SD 1.66), 9.38 (SD 1.31), 10.94 (SD 1.36), 12.69 (SD 1.41), 13.38 (SD 1.25) and 13.87 (SD 1.25) respectively for females. The correlation coefficients between second molar and CVM stages were 0.625 and 0.661 for males and females respectively. Conclusion: The ideal age range for extraction of poor prognosis lower FPM was between 9.78 - 10.50 years and 10.67 - 10.85 years for Malay males and females respectively. In upper arch, the ideal age for extraction was between 10.5 - 12 years for both genders. There is a strong association between second molar and cervical vertebral maturation stages. The clinician may estimate timing of the peak in mandibular growth is during the first appearance of permanent mandibular second molar root bifurcation and when the crown formation are equal to the root formation. Age difference of crypt stage developmental between genders was significant in all third molar studied teeth except for the lower left third molar. Age difference of crypt stage developmental between upper and lower jaw was significant, on other hand age difference for right and left was not significant.
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Keywords
Poor prognosis lower FPM, orthopantomogram radiographs (OPG)
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