The main occluding area in normal occlusion and mandibular prognathism.

OBJECTIVE: To clarify whether the concept of main occluding area, where hard food is initially crushed, exists in patients who have a jaw deformity. MATERIALS AND METHODS: Nineteen subjects with normal occlusion, 18 patients with mandibular prognathism, and 11 patients with mandibular prognathism who had undergone orthognathic surgery participated in this study. The main occluding area was identified by clenching Temporary Stopping. The coincidence, location of the main occluding area, and distance from the first molars to main occluding area were examined. RESULTS: High coincidence of the main occluding area was obtained in all groups, signifying that the main occluding area exists even in these patients. Mandibular main occluding area was located on the first molar in all groups. Maxillary main occluding area in subjects with normal occlusion was located on the first molar. However, it was located on the second premolar and first molar in patients with mandibular prognathism, and on the first and second molars in patients with mandibular prognathism who had undergone orthognathic surgery. There was a statistically significant difference in distance from the maxillary first molar to the main occluding area among groups, but there was no difference in the distance from the mandibular first molar among groups. CONCLUSION: The main occluding area is more stable on the mandibular first molar than the maxilla in all groups.

Reconstruction of a collapsed dental arch in a patient with severe periodontitis.

This case report describes the significance of orthodontic treatment in reconstruction of a collapsed dental arch and a malocclusion associated with severe periodontitis. A Japanese man (age, 40 years 7 months) had an anterior crossbite, a collapsed occlusion, and severe periodontitis. Orthodontic treatment included the following steps: (1) correction of the anterior crossbite, labial movement of the maxillary incisors, and intrusion and retraction of the mandibular incisors; (2) correction of the posterior crossbite on the left side, buccal movement of the maxillary left canine and first premolars, and intrusion and retraction of the mandibular first premolar into the space of the mandibular left canine; (3) correction of the crowding of the mandibular right buccal segment and alignment of the teeth after extraction of the mandibular right first molar with a periapical lesion; and (4) improvement of the occlusion, with reconstruction of an acceptable occlusion. When combined with restorative and prosthodontic treatment, a fairly good occlusion was obtained. Reevaluation of the treatment after 11 years showed that the occlusion and periodontal condition were maintained well without deepening of the pockets and further bone loss. Orthodontic treatment with a systematic approach helped to recover the occlusion and prevented the recurrence of periodontitis by acquiring a good oral environment and motivating the patient to maintain oral health.

Application of thermography in dentistry--visualization of temperature distribution on oral tissues.

The purpose of this study was to devise and propose appropriate conditions for the photographing of thermal images in the oral cavity and to evaluate which thermography techniques can be applied to dentistry by evaluating the differences in temperature among oral tissues. Thermal images of oral cavities of 20 volunteers in normal oral condition were taken according to the guidelines of the Japanese Society of Thermography, with five added items for oral observation. The use of a mirror made it possible to take thermal images of the posterior portion or palate. Teeth, free gingiva, attached gingiva and alveolar mucosa were identified on thermal images. There were differences in temperature between teeth, free gingiva, attached gingiva and alveolar mucosa. These were nearly in agreement with the anatomical view. Thermography need no longer be restricted to the anterior portion using a mirror, and can now be applied to the dental region.