THE JOURNAL OF HOKKAIDO ORTHODONTIC SOCIETY

A migrating tooth is a rarely encountered phenomenon, the cause of which is not clear. We examined the possible factors causing migrating teeth using etiological study models and cephalograms of patients who had a familial migrating tooth or teeth. The subjects were two sisters and a brother. The elder sister had bilateral migrating teeth, and the younger sister had one migrating tooth in the maxilla. The brother had no migrating teeth. Our results showed that factors causing migrating teeth are upper basal arch width, size of the maxilla, arch length discrepancy, and congenitalness.

View full abstract

Orthodontists sometimes experience cases of breakage of a retainer in the marginal area. The aim of this study was to determine whether the use of glass cloths improves the mechanical properties of polymer for retainers. The glass cloths were silanated before fabrication. All test specimens were 2 x 15 x 40 mm in size. The specimens were divided into three types according to the manner of containment of the glass cloth : without reinforcement (type 1), the cloth in the neutral zone (type 2) and the cloth on the surface (type 3). The results were as follows. 1. The elastic moduli of type 2 and 3 specimens were about 1.3- and 1.4-times larger than that of type 1 specimens, respectively. 2. The flexural strengths of type 2 and 3 specimens were about 1.4- and 1.7-times larger than that of type 1 specimens, respectively. Adequate improvement in transverse strength of the retainer polymer was accomplished simply by placing the glass cloth. This method using biocompatible glass cloth is a simple method for reinforcing resin and is thought to be effective for preventing breakage of retainers.

View full abstract

The purpose of this study is to predict the mandibular position following correction of functional anterior crossbite. Multiple regression analyses were carried out using data obtained from lateral cephalograms in the intercuspal and rest positions at the first examination and at an examination after correction of anterior crossbite in 19 patients. The following results were obtained. 1. For Δ SNB", a multiple regression equation (a multiple correlation coefficient : 0.76) was obtained when S・Pog-OP (Upper) , NF-MP, ANB and overbite were used as the explanatory variables. 2. For Δ B", a multiple regression equation (a multiple correlation coefficient : 0.87) was obtained when S・Pog-OP (Upper), ANB, NF-OP (Upper), Δ B (X)' and SNB were used as the explanatory variables. 3. For Δ B (X)", a multiple regression equation (a multiple correlation coefficient : 0.82) was obtained when S*Pog-OP (Upper) , ANB, NF-MP and Δ SNB' were used as the explanatory variables. 4. For Δ B (Y)", a multiple regression equation (a multiple correlation coefficient : 0.39) was obtained when overjet was used as the explanatory variable. The results suggested that it was possible to predict the degree of horizontal change in mandibular position following correction of functional anterior crossbite by the multiple regression equations obtained in this study.

View full abstract

Show abstractHide abstract

The purpose of this study was to determine the occlusal status and maxillofacial morphology in elderly Japanese with many remaining teeth. The subjects were 23 elderly Japanese over 70 years of age (16 males and 7 females; mean age, 76.0 years) who had more than 20 teeth (mean number, 24.3) other than third molars, including all six incisors, and who still had adequate vertical dimension. All of the subjects underwent intraoral examinations, during which radiographs and impressions were taken. The mean overbite and mean overjet of the subjects were 2.4 mm and 3.4 mm, respectively. Maxillary protrusion was seen in two males(8.7% of the subjects), and mandibular protrusion was seen in one female (4.3% of the subjects). Anterior crowding was seen in 9 (39.1%) of the subjects (only lower crowding in 5 subjects and both upper and lower crowding in 4 subjects). Spaced arches were seen in 3 (13.0%) of the subjects (only upper in 2 subjects and only lower in 1 subject). Most of the subjects had either Angle class I or class n canine and molar relationships. Maxillofacial morphology was within the normal range with a slight tendency toward maxillary protrusion associated with a posterioinferiorly positioned mandible. The upper incisors in the male subjects were mildly retroclined, while the lower incisors in the female subjects were proclined. The results of this study suggest that maintenance of acceptable degrees of overbite and overjet in Angle class n people in this study by dental compensations is possible and that elderly Japanese with more than 20 teeth have relatively good occlusal and maxillofacial forms.

View full abstract

Download PDF (1063K)

Register with J-STAGE for free!