Yasushige Isshiki

A comparative study of Caucasian and Japanese mandibular clinical arch forms.

The purpose of this study was to clarify morphological differences between Caucasian and Japanese mandibular clinical arch forms in Class I, II, and III malocclusions. The study included 60 Class I, 50 Class II, and 50 Class III cases from each ethnic group. The most facial portion of 13 proximal contact areas was digitized from photocopied images of the mandibular dental arches. Clinical bracket points were calculated for each tooth based on mandibular tooth thickness data. Four linear and 2 proportional measurements were taken. The dental arches were classified into square, ovoid, and tapered forms to determine and compare the frequency distributions between the 2 ethnic groups. The Caucasian population had a statistically significant decreased arch width and increased arch depth compared with the Japanese population. When the subjects were regrouped by arch form, no statistically significant difference in arch dimension was observed between the 2 ethnic groups in any of the arch form samples. Our results suggest that there is no single arch form specific to any of the Angle classifications or ethnic groups. It appears to be the frequency of a particular arch form that varies among Angle classifications or ethnic groups.

Occlusal stability after extraction orthodontic therapy in adult and adolescent patients

In this study we compared the posttreatment stability of occlusion in adults and adolescents treated for crowding or maxillary protrusion with four-premolar extractions and edgewise mechanics at an average of more than 4 years out of treatment. The adolescent sample showed a significantly greater posttreatment increase in mandibular anterior crowding than the adult sample. Posttreatment overjet and overbite remained more stable in the adolescents. We noted a correlation between in-treatment expansion and posttreatment narrowing of mandibular intercanine width in the adults. Differences in postorthodontic occlusal changes were noted between the adult and adolescent samples.

Alveolar Bone Grafting for Patients With Unilateral Complete Alveolar and Palatal Clefts Improves the Bony Structure of the Nose

Objective: This is a retrospective study regarding the effect of alveolar bone grafting (ABG) on morphological changes in the bony structure of the nose in alveolar and palatal cleft patients. Methods: Sixty-five randomly selected adults were included in the present study. Of the 65 subjects, 21 had no congenital anomaly and were designated as the control group (n  =  21; mean age 22.4 ± 4.3 years). Forty-four had unilateral complete clefts of the alveolus and palate on the left side. The patients with clefts were further divided into two subgroups based on presence or absence of ABG in their histories. These groups were termed the ABG(+) group (n  =  24; mean age 20.3 ± 2.5 years) and the ABG(−) group (n  =  20; mean age 32 ± 4.5 years), respectively. An anatomical structure that constitutes the bony component of the nose was defined. This structure, composed of the nasal bones and part of the frontal process of the maxilla, was termed the BSEN (bony structure of the external nose). The symmetry of the BSEN was assessed quantitatively by performing morphological measurements on computerized tomographic images of each patients skull, and these measurements were compared among the control, ABG(+), and ABG(−) groups. Results: The BSEN presented more symmetric features in the ABG(+) group patients than in the ABG(−) group patients. Conclusion: ABG improves symmetry of the BSEN. This finding justifies ABG in terms of cosmetic improvement of the external nose in patients with unilateral complete alveolar and palatal clefts.