THE JOURNAL OF HOKKAIDO ORTHODONTIC SOCIETY

Orthopedic appliances such as a chincap and maxillary protraction appliance (MPA) are well employed for skeletal class in patients to correct their anterior crossbite and intermaxilary discrepancy. The purpose of the present study was to evaluate morphological changes of skeletal and dental structures using forty-six growing girls (average age, 10 years 3 months), who had received MPA as the first-stage treatment. The results were as followings ; 1. During MPA treatment, forward displacement of the maxilla with counter-clockwise rotation and backward and downward displacement of the mandible, which resulted in 3.5 ° increase in ANB angle, were observed. 2. As indicated by 3.6° and 2.9° decrease in functional occlusal plane (FOP) and conventional occlusal plane (COP), respectively, flattening of the occlusal plane was observed. 3. Wits appraisal base on FOP changed from -10.1 mm to -4.3mm (5.8mm increase). Wits appraisal (COP) changed from -8.1 mm to -2.4 mm (5.7 mm increase). 4. Increase in Wits value was largely associated with flattening of the occlusal plane. These results indicate that MPA treatment is effective not only for correction of class IE skeletal profile, but also for flattening of the occlusal plane, which would be benefit for the final construction of occlusion.

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It has been recognized that the third molars effect the posterior discrepancy and the stability of the dental arch after orthodontic treatment. We investigated the chronological changes of the occurrence of the third molar germs and the relationship between those occurrence and the malocclusions. The selected subjects were 283 patients less than fifteen years old at the orthodontic clinic of Hokkaido University Dental Hospital. The congenital deformities such as cleft palate were excluded from the subjects. The subjects were divided into two groups. The one group was 147 patients who were initially examined between April 1981 and September 1982 (80s group), and the other group was 136 patients examined between February 1993 and November 1994 (90s group). Panoramic radiographs were used as materials. The following results were obtained : 1 .The frequency of the patients having all four third molars in the 90s group was slightly higher than that in the 80s group. The frequency of the existence of the mandibular third molars was significantly higher than that of the maxillary ones in both groups. 2. The frequency of the Class II patients having all third molars was significantly higher than that of the Class III. These results suggest that the orthodontic patients having all third molars slightly increase and this is related with the increment of Class II patients.

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The purposes of this study were to survey the subjective estimates of 95 undergraduates on nine different profile silhouettes using 11 items of the questionnaire and to investigate the relationship between the profile measurements with reference to Ricketts's E-line and the subjective estimates. The results were as follow : 1. The facial silhouette chosen as the most preferable profile was the same one chosen as the most familiar, smart, intelligent, beautiful, attractive, sensitive, and mature one. The silhouette chosen as the least preferable profile was the same one as the funniest and the least intelligent one. 2. The upper and lower lips of the most preferable facial silhouette were positioned posterior to the E-line. 3. The upper and lower lips of the preferable facial silhouette were positioned much anterior to the E-line. 4. The distance between the upper lip and the lower one was substantially related to the estimated value with regard to the preference.

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The electrolyzed neutral water has very strong sterilizing power. The power is the same as the electrolyzed hyper acid water has. On the other hand, the electrolyzed neutral water effects safely on a living body and/or one's environment, because the generated chloride gas from the electolyzed neutral water is little in pH neutral area. When we use these sterilizing water in clinical orthodontics, we have to take care about corrosion of metal. But, it was not investigated the corrosion for orthodontic wires exposed to the electolyzed neutral water. In the present study, we analyzed the quantity of soluble metals (Fe, Ni, Cr, Ti, Cu, Mo) from four kinds of orthodontic wire , when these wires are exposed to the electrolyzed neutral water during 5 minutes and 24 hours. The result was that the solubility of any metals was not detected either after 5 minutes or 24 hours exposed to the electrolyzed neutral water. This result shows that we don't have to fear about the corrosion of orthodontic wires by using the electrolyzed neutral water in clinical orthodontics.

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