Normative Data of Variables Determining Eruption of Third Molars in Orthodontic Patients – A Retrospective Study

Abstract

Objectives: 1) To Formulate a normative data of variables affecting the eruption of third molar. 2) To help format a research data to compare variable changes occurring during formative and eruption stage (11-16 years)of third molar. Materials and Methods: The sample comprised of Orthodontic patients at CMCH from 2012-2019, within an age group of 11years -16 years, which was approved by the ethical committee. 40 Male and 40 Female Patient's Orthopentogram with complete set of teeth were considered in the study. The measurements analysed were: 1) Retromolar space:is distal contact of PMM2(Permanent mandibular second molar) and junction of occlusal plane to the anterior border of the mandible. 2) Gonial Angle: angle between the tangent from inferior border of the mandible and posterior border of the mandible. 3) Mesiodistal width of second molar : greatest distance between mesial and distal portion of the crown. 4) Mesiodistal width of third molar: greatest distance between mesial and distal extension of the crown. 5) Angulation of first and second Molar : the angle formed between the long axis of PMM1 (Permanent mandibular first molar) and PMM2 (Angulation m1m2). 6) Angulation of second molar to base of Mandible: the angle formed between the long long axis of PMM2 and the tangent drawn to the inferior border of the mandible (Angulation m2bm). 7) Nolla's classification of third Molar. Trophy Dicom; carestream LS 8000c machine programmed with Kodak software was used to record the digital OPG with standard protocol and head position. The 7 Variables were analysed with the Kodak software and the measurements were recorded on excel worksheet. Results: The Data was used for comparison of all variables to explore gender specific differences, only the mesiodistal width was significantly different between the gender. A descriptive table was formulated with a range of measurements for all variables. A correlation between Retromolar space and all other variables was analysed ,there is a positive correlation with formation of third molar(Nolla's grading) and retromolar space in females and it is statistically significant. Though a weak ,correlation exists between other variable and retromolar space ,it was not statistically significant. Conclusion: 1) A normative data and Data for future research, of variables affecting the eruption of third molar in their formative and eruptive stage was Formulated. 2) Though a weak correlation exists between other variable and retromolar space during the formative and eruption stage of third molars.