Assessment of Mandibular and Dental Arch Profiles in Subjects with Mandibular Third Molar Impaction

Objectives: To determine the normal size of the mandible and the difference of the dental arch length and the total teeth size space that is important for prevention of mandibular third molar impaction.Methods: 102 subjects were divided into two groups, based on the eruption of mandibular third molars.Impacted mandibular third molar (Group1) comprised of 50 subjects and the erupted (Group 2) comprised of 52 subjects.Mandibular length, width, index, total teeth size, dental arch length, dissimilarity in dental arch length and the total teeth size were assessed.Results: There was a significant difference in the dental arch length, difference of dental arch length and total teeth size among the 2 groups in both genders.A noteworthy contrast was seen in the mandibular length (P < 0.001), mandibular width (P < 0.001), dental arch length (P < 0.001), total teeth size (P -0.002), difference in dental arch and total tooth size (P-0.001) between males and females.The normal sized mandible should have a length within the range of 13.5cm to 17.5cm for males and 13.0cm to 17.0 cm for females while normal dental arch-total teeth size difference range should be in the range of 0.40cm -1.40 cm in males and 0.20cm -1.20cm in females for proper third molar positioning.Conclusion: Based on the above findings, it may be justified to perform a preventive or therapeutic surgical removal of the lower third molars of the post pubertal patients whose parameters fall below these set values.Impaction occurs where there is prevention of tooth eruption to the functional site, owing to reduced space or abnormal developmental locus/site [1,2].The most commonly impacted tooth is still the maxillary third molar accounting for 98 percent of impactions [3,4].The prevalence of impacted third molar(mandibular) is 72.7% in the age range of 20-30 years cohort [5].Third molars usually erupt around 17-21 years with variations being 14 in Nigerians [6] and 26 in Europeans [7].The growth of mandible after puberty indicates more of a mandibular impaction, which is higher in females [8-13].Impacted third molars may or may not cause any pathological changes and their removal is inevitable owing to its risks like acute or chronic pericoronitis, periodontal problems and presence of a