Validity of soft tissue landmarks in determining the occlusal plane

The orientation of the occlusal plane is an important clinical procedure in prosthodontic treatment for edentulous patients. Various intraoral and extraoral landmarks have been used for the orientation of the occlusal plane, but none of them give sufficient guidelines for that purpose. Therefore, a study was carried out to ascertain the role of intraoral and extraoral soft tissue landmarks in determining the occlusal plane. 30 Indian subjects ranging in age from 19-23 years were selected from a group of approximately 200 dental students. The soft tissue landmarks considered in the study were retromolar pad, parotid papilla, commissure of the lips, buccinator groove, and ala-tragus line. An indigeneously fabricated Occlusal plane relator was used to find out the relative parallelism of the ala-tragus line and the occlusal plane. This device had a base with a vertical arm over which a sliding ball and socket joint was placed. This joint had a direct connection with the anterior occlusal plane indicator and ala-tragus line indicator. Absolute mean was taken of the two readings on ala-tragus line indicator on either side of the face. The line in which the difference between the two readings was least was parallel to the occlusal plane. The lower 1/3rd of the retromolar pad was observed to be consistent with the mandibular occlusal plane. The mean distance of the parotid papilla was 2.56 mm above the maxillary occlusal plane. The mean values of all readings of buccinator groove was 0.94 mm below the mandibular occlusal plane. In this study close correlation was observed between the mandibular occlusal plane and the commissure of the lips; the mandibular occlusal plane and the buccinator groove. The line drawn from the ala of the nose to the middle of the tragus was found to be parallel to the maxillary occlusal plane.