Effects of occlusal contact and its area on gravity fluctuation.

OBJECTIVE: To examine changes in gravity fluctuation caused by experimentally altering the area of occlusal contact. MATERIALS AND METHODS: Subjects consisted of 15 adult Japanese males with normal stomatognathic function, no missing teeth except for the third molars, and equivalent occlusal contact in the anterior and bilateral posterior regions. Silicon biteplates fabricated for each subject to evaluate gravity fluctuation in relation to changes in occlusal contact area were as follows: RP(-)-OC(+) (entire occlusal surface covered in centric occlusion); RP(+)-OC(+) (entire occlusal surface covered with bite slightly raised); Ant or Pos/RP(+)-OC(+) (anterior or posterior region selectively covered); and RP(+)-OC(-) (only retromolar pads covered, no occlusal coverage). RESULTS: No significant differences in gravity fluctuation were noted between subjects wearing biteplates covering the entire occlusal surface. Subjects wearing biteplates with no occlusal contact showed greater gravity fluctuation than those with occlusal contact. In addition, gravity fluctuation for the Ant/RP(+)-OC(+) group (no occlusal contact in the posterior region) was greater than for RP(+)-OC(+) and Pos/RP(+)-OC(+). However, groups with unilateral occlusal contact in the posterior region exhibited large right and left sway amplitude. CONCLUSIONS: These results suggest that occlusal contact, especially posterior occlusal contact, affects gravity fluctuation, and that appropriate occlusion attained by maintaining even occlusal contact in the posterior region is crucial for gravity fluctuation.

Changes in the distribution of nerve fibers immunoreactive to calcitonin gene-related peptide according to growth and aging in rat molar periodontal ligament.

OBJECTIVE: To analyze the age-dependent changes in nerve fibers immunoreactive to calcitonin gene-related peptide (CGRP-ir) in the periodontal ligaments of rats. MATERIALS AND METHODS: Thirty male Wistar-ST rats were divided into growing groups (5, 9, and 15 weeks of age) and aging groups (6, 12, and 24 months of age) (n = 5 in each group). Eight serial sagittal sections, 5 microm thick, were cut parallel to the distobuccal root of the maxillary right first molar. These tissues were stained with a rabbit monoclonal antibody against CGRP. The observation area was divided into three parts (mesial, apical, and distal) and observed using a light microscope. RESULTS: CGRP-ir nerve fibers were primarily distributed in the apical periodontal ligament in the growing group, with significantly more fibers than in the aging group. CONCLUSIONS: CGRP-ir nerve fibers in the periodontal ligament are dense during the growth period and decrease gradually with aging, indicating that CGRP may affect periodontal tissue with growth and aging.

Relationship between occlusal force and mandibular condyle morphology. Evaluated by limited cone-beam computed tomography.

OBJECTIVE: To clarify the relationship between occlusal force and mandibular condyle morphology using clinical data. MATERIALS AND METHODS: The subjects were 40 female patients with malocclusion. The mandibular condyle morphology was assessed by using limited cone-beam CT imaging. The maximum occlusal force was calculated by using pressure-sensitive films. Maxillofacial morphologies were analyzed by using data from lateral cephalograms. RESULTS: Correlation analysis showed that the occlusal force was correlated with the lateral and posterior radii of the condyles, and with the mandibular plane angle to the Frankfort horizontal plane (FH). Moreover, condylar length was significantly correlated with the occlusal plane angle to the FH, the mandibular plane angle to the FH, the ramus inclination, and the posterior facial height (S-Go). Low-occlusal-force patients tended to have smaller mandibular condyles. This size-related difference was more remarkable on the lateral and posterior side. CONCLUSIONS: Occlusal force influences not only maxillofacial morphology but also mandibular condyle morphology.

Treatment of severe Class II Division 1 deep overbite malocclusion without extractions in an adult.

This case report describes the orthodontic treatment and retention of an adult with severe Class II Division 1 deep overbite malocclusion; treatment was completed without premolar extractions. We used improved superelastic nickel-titanium alloy wire (L&H Titan, Tomy, Tokyo, Japan) with J-hook headgear for the combined intrusion of the anterior segment and the distalization of the maxillary posterior segments. The overbite was corrected from 6.0 to 2.0 mm by intrusion of the maxillary and mandibular incisors; the overjet was corrected from 13.0 to 2.0 mm. Although no premolars were extracted, good occlusion and facial esthetics were achieved. Follow-up records 2 years after active treatment show that the results were maintained.

Effect of surface modification on the photocatalysis of Ti-Ni alloy in orthodontics.

Photocatalytic activity from the reaction of titanium oxide with ultraviolet light has recently gained much attention. In particular, there is scientific interest in inducing photocatalytic reactions on Ti-Ni alloy, a material widely used in orthodontic applications. However, it is believed that inducing a photocatalytic reaction with an amorphous oxide film on the alloy is a difficult challenge. In this study, therefore, we sought to induce a photocatalytic reaction on Ti-Ni alloy by subjecting the latter to electrolytic and heat treatments. Then, an antibacterial test was used to examine whether a photocatalytic reaction had indeed been induced. By thickening the titanium oxide film with electrolytic treatment and then applying heat treatment, the surface oxide film of Ti-Ni alloy was thus modified from amorphous structure to rutile crystal. Furthermore, it was revealed that Ti-Ni alloy had an antibacterial effect by virtue of the photocatalytic reaction.