Unusual role in occlusion and mastication of a horizontal positioned erupted mandibular third molar: a rare case

Lower third molars are frequently extracted due to pathologies of the dental follicle, pericoronitis, advanced carious lesions, orthodontic reasons (risk of anterior tooth crowding) or causing periodontal or carious lesions in the distal area of the second molar. The case presented here is of a male patient that came to our Clinic experiencing pain in the distal area of one of his old bridges. The clinical examination revealed a malpositioned, but unusually functional third molar; it is a very rare situation for an initially impacted third molar to erupt in an almost horizontal position and not only to remain on the arch for a very long period of time, but also to contribute to mastication efficiency and occlusion, despite the fact that masticatory forces are distributed at a right angle on its long axis and that mastication takes place on the distal surface of the crown and root, and not on the usually occlusal cusped surface. The horizontal mandibular right third molar contributed to maintaining the vertical dimension of occlusion and the masticatory efficiency for a very long period of time; it also ensured a proper distribution of forces trough the long axis of the second premolar, since the distal contact of the third's molar crown with the second premolar helped it to resist masticatory forces and to remain on the arch, despite the prolonged absence of any mesial contact.