An experimental study on the morphologic changes of rat mandible following occlusal interference / 대한치과교정학회지

The occlusal interference during adolescent period makes some effects on growth and development and morphological changes. And so, if we could predict the timing and results of orthodontic treatment who have occlusal interference during adolescent period, it may be helpful for diagnosis and treatment planning of orthodontic treatment. For about those, the purpose of this study was to evaluate the effects of the posterolateral displacement by the metal casting crown with inclined pathway on the mandibular condyle and morphologic changes of mandible in the rat. The experimental animals were thirty six Sprague-Dawley male rats of 8 weeks old. Eight of them was used as control group, and experimental group I (continuous appliance wearing group) was composed of sixteen and experimental group 2 (appliance removal group after worn the appliances during 3 months ) was composed of remaining twelve. The animals of experimental group 1 were sacrificed after 1, 2, 3, 6 months from beginning of the experiment and experimental group 2 were sacrificed 1, 2, 3 months after removal of the appliance from worn the appliance during 3 months. Both of mandible and temporomandibular joint were observed histologically and radiologically. The results were as follows: 1. In experimental group 1, the mandibular length and lower posterior height were decreased with experimental period, while the lower anterior height was increased, and the curvature of lower incisors and lingual inclination of anterior alveolar bone were profound as compared with control group. 2. In experimental group 1, both of the thickness of the condylar cartilage were thinned in the posterosuperior region, and this phenomenon was more prominent on right than left in 3-Mo experimental period and both sides were marked thinned in 6-Mo experimental period. 3. In experimental group 2, the lower anterior height was low and lower posterior height was high as compared with experimental group 1, and the curvature of lower incisors and lingual inclination of anterior alveolar bone were recovered to control group. 4. In experimental group 2, both of the thickness of the condylar cartilage were thickened in the posterosuperior region, and this phenomenon was more prominent with experimental period. 5. In experimental group 2, the mandibular length was short, lower anterior height was hight, the curvature of lower incisors were profound, and in histologically, both of the thickness of the condylar cartilage were thickened in the posterosuperior region as compared with control group. As shown above, the occlusal interfernce affected the condylar cartilage, curvature of lower incisor, inclination of anterior alveolar bone, mandibular length, and anterior and posterior height. When the interference was removed, significant recover was found in condylar cartilage, mandibular length, and posterior height. Although no significance was found, other items of measurement showed trends for recovery.

The variation of mandibular pattern and cranial base angle in craniofacial malocclusion / 대한치과교정학회지

This study was designed to investigate the variation of mandibular pattern and cranial base and their association in the craniofacial malocclusion. The material was the 165 cephalometric radiographs taken from craniofacial malocclusion. The sample was devided into two groups by age child group aged from 10 to 13 years and adult group aged over 18 years, and each group was devided into 3 types of malocclusion, class I, Class II div. 1 and Class III malocclusion. Child group consist of 35 samples and adult group consist of 20 samples in each malocclusion type. Various angular and linear measurements on the cephalometric radiographs were recorded and statistically analyzed. The results of the study were as follows, 1. The cranial base angle was largest in Class II div, 1 malocclusion and smallest in Class III malocclusion 2. The anterior cranial base length was largest in Class II div 1 malocclusion but posterior cranial base length did not show statistical difference 3. The mandibular body length of Class III malocclusion was larger than those of Class I and Class II div 1 malocclusion in the adult group but did not shown difference in the child group. The ramus height of Class III malocclusion was larger than those of Class I and Class II div 1 malocclusion in the child and adult group, but there were no difference between Class I and Class II div, 1 malocclusion. 4. The mandibular position was showed low correlation with the cranial base angele.

Occlusal variations in the posterior and anterior segments of the teeth / 대한치과교정학회지

The purpose of this study was(1) to determine the prevalence of some causes by which dental occlusion might be affected, (2) to determine the prevalence of malocclusion, and types of molar, vertical incisor and horisontal incisor frlationships, and (3) to examine the sex difference in the prevalence ratios, and (4) to determint the between-examiner differences in asseassing types of dental occlusion. The material consisted of 1281 males and 811 females, total 2091 persons, aged 17 to 21 years. Tow examiners who were graduate students in the orthodontic course, examined independently dental occlusion of the material. Before calculating the statistics, the subjects consisted of 156 males and 164 females, total 320 persons, having any one or more causes suspected to affect dental occlusion, was eliminated. Than the remained subjects, 1124 males and 647 females, total 1771 persons, were assessed. The results were as follows 1. The prevalence of some causes by which dental occlusion might be affected was 15.32 per cent. The missing rate of any one or more first molars was 8.85 percent, that of any one or more teeth positioned anterior to the first molar was 3.83 per cent. The prevalence of crossbite of the first molat 0.48 per cent, that of retained primary teeth was 0.77 percent, and that of orthodontic treatment was 0.43 per cent. 2. The rate of between-examiner difference was 12.35 per cent in assessing the types of molar relationship, 18.86 percent in assessing the types of horziontal incisor relationship, and 26.37 percent in assessing the types of horizontal incisor relationship. 3. There was no sex difference in the prevalence ratios of the types of molar relationship . The pervalence of Class I molar relationship was 80.91 percert, that of Class II was 5.03, that of Class II subdivision was 4.01, percent, that of Class III was 5.99 percent and that of Class III subdivision was 4.07 percent. 4. In the prevalence of the types of horizontal incisor felationship, there were no sex differences except that of Class II division 2. The prevalence of Class I horizontal incisor relationship was 73.12 percent, that of Class II division 1 was 12.03 percent, that of Class II division 2 was 6.58 percent in male and 4.33 percent in female, and that of Class III was 9.09 percent. 5. In the pervalence of the types of vertical incisor relationship, there were no sex difference except that of deep bite. the prevalence of open bite was 2.20 per cent, that of edge-to-edge bite was 9.15 percent, that of normal bite was 76.34 percent, and that of deep bite was 14.15 percent in male and 9.12 percent in female. 6. There was no sex difference in the prevalence of malocclusion the prevalence of maloccusion was 82.67 percent and that of normal occlusion was 17.33 percent. 7. There was a tendedcy that when Class I molar relationship vhanged to Class II, incisor-ships were to be larger overjet or upright upper incisors and deep bite, but when that changed to Class III molar relationship, these were to be cross bite and openbite.