Objective This study was performed to investigate the effects of mandibular incisor (MnI) agenesis and divergent malocclusion type on mandibular symphysis inclination and morphology. Methods A total of 162 selected patients were divided into two groups: one group consisted of patients with one or two congenitally missing MnIs, and another group comprised patients without tooth agenesis. Patients in each group were categorized into three divergent malocclusion groups (hypodivergent, normodivergent and hyperdivergent) according to the Frankfort mandibular plane angle, with 27 patients per group. Lateral cephalograms were used to evaluate mandibular symphysis inclination and morphology. Two‐way analysis of variance, simple main effect analysis and Tukey's test were used for statistical comparisons. Results The agenesis group demonstrated a significantly greater retroclination of the mandibular symphysis than the non‐agenesis group in the normodivergent group. In the hypodivergent and normodivergent groups, the agenesis group showed a significantly smaller area of the alveolar bone with thinner width and shorter height than the non‐agenesis group. Conclusion For the Japanese orthodontic patients, MnI agenesis caused a significantly great retroclination of the mandibular symphysis in patients with normodivergent malocclusion and significantly small area of the alveolar bone with thin width and short height in patients with hypo‐ and normodivergent malocclusions.

The purpose of the present study was to assess, in detail, the association between tooth agenesis (TA) and various sagittal skeletal malocclusion groups in a Japanese orthodontic population. One thousand and twenty patients were divided into skeletal Class I, II, or III malocclusion groups using the A point, nasion, and B point angle. TA was identified in each group using panoramic radiographs. Patients with class III malocclusion exhibited a significantly higher prevalence of third molar (M3) agenesis, bilateral and overall agenesis of the maxillary M3s than those patients with a class II malocclusion. Those with a Class II malocclusion demonstrated a significantly lower prevalence of overall agenesis of the mandibular M3s than those with class I or III malocclusions. There were no significant differences in the prevalence of agenesis of teeth other than the M3s between the skeletal malocclusion groups. In each group, there was significantly more M3 agenesis present in the maxilla than in the mandible, and agenesis of the incisors and second premolars was found more often in the mandible than in the maxilla. Sagittal jaw relationships were significantly associated with M3 agenesis but were not associated with agenesis of the maxillary and mandibular incisors and second premolars.

The purpose of this study was to determine whether a system using a resin coating material (PRG Barrier Coat) with anticariogenic ability can effectively bond orthodontic brackets to human teeth. Resin-modified glass-ionomer cement system (Fuji Ortho LC, group 1) and resin composite cement systems (BeautyOrtho Bond) combined with a self-etching primer (group 2), with the resin coating material (group 3), and with the resin coating material after an organic acid etching agent (group 4) were used for bracket bonding. The mean shear bond strength (SBS) was significantly higher in group 1 than in groups 2, 3 and 4. Groups 2 and 4 exhibited a significantly higher mean SBS than group 3. The resin composite cement system combined with the resin coating material after the organic acid etching agent can serve as an alternative for orthodontic bracket bonding.

A BSTRACT Background: Producing dentures for edentulous patients is important to improve quality of life of elderly. The determination of the occlusal vertical dimension on producing dentures is one of the key factors for using the dentures comfortably. The purpose of this study is to consider the usefulness of the determination of the occlusal vertical dimension of a facial measurement method applied on scanned facial image using a noncontact three-dimensional measurement device. Materials and Methods: Twenty-four dentulous individuals (mean age 26.6 ± 2.4 years old) were examined in this study. A noncontact three-dimensional measurement device was used for the scanning of the face both in the holding by hand and the fixing to the camera stands situations. The distances between subnasal and gnathion, pupil and oral slit, middle of glabella and subnasal, and right and left corners of the mouth were measured on the scanned face image and compared with the actual values. Results: The significant differences were not recognized on the four measurement items between the distance of actual values and obtained on scanned data (fixing conditions). The coefficients of variation of the distances between subnasal and gnathion, and pupil and oral slit on scanned data (fixing condition) were significantly lower than those at actual conditions ( P < 0.05). Conclusion: The results of this study suggested that a stable facial measurement can be successfully implemented by using a noncontact three-dimensional measurement device. This method yields outcomes which match the actual values.