Predictive factors of third molar eruption

• Published in: Revue de stomatologie et de chirurgie maxillo-faciale Vol. 112; no. 5; pp. 263 - 268
• Main Authors: Sebbar, M, Bourzgui, F
• Format: Journal Article
• Language: French
• Published: France 01-11-2011
• Subjects: Adolescent; Adult; Bicuspid - anatomy & histology; Bicuspid - diagnostic imaging; Bicuspid - surgery; Child; Dentistry; Female; Follow-Up Studies; Forecasting - methods; Humans; Male; Molar, Third - anatomy & histology; Molar, Third - diagnostic imaging; Molar, Third - physiology; Prognosis; Radiography, Panoramic; Retrospective Studies; Risk Factors; Tooth Eruption - physiology; Tooth Extraction; Tooth, Impacted - diagnosis; Tooth, Impacted - diagnostic imaging; Tooth, Impacted - etiology; Young Adult
• ISSN: 1776-257X
• DOI: 10.1016/j.stomax.2011.05.003

We studied the prognosis of upper and lower third molar evolution.
Seventy-eight patients were included after a clinical examination, dental casts, panoramic and lateral cephalometric radiographs on inclusion (T1) and two years after (T2). Five parameters were studied: retromolar space (RMS) between the third molar (M3) and the anterior ridge of the ramus; RMS/M3 crown diameter ratio, distances (PTV-M(1)) and (X(i)-Mi(2)); and third molar angle with occlusal plane.
They were noted at T1 and T2. The gain of retromolar space from T1 to T2 reached 1.2 to 2.2mm without extraction, 2 to 2.7mm with PM extraction, and 4.5 to 6.8mm with M1 extraction. The "RMS/M3 diameter" ratio increased in the maxilla from 0.6 to 0.8 and from 0.5 to 0.8 in the mandible (P=0.01) between T1 and T2. PTV-M1 increased significantly from 17.1 to 19.9mm (P<0.001), and Xi-M2i increased significantly from 18.5 to 22.4mm (P<0.001) between T1 and T2.
The extraction of premolars has little influence on the variation of the retromolar space; conversely first molar extraction increases that space. Prognosis techniques for the evolution of third molars are helpful when considering avulsion.