The mathematical model of the dental and basal bone arch form of skeletal classⅢmalocclusions in three-dimensional space / 天津医药

Objective To establish a mathematical model to describe the skeletal class Ⅲ malocclusion of patient dental and basal bone arch form, for providing a data reference and basis for further study. Methods Thirty-five patients with skeletal classⅢmalocclusion were selected in this study for computed tomography CBCT. The data of 3-D image were analyzed, and dental arch marker (Fa) and base bone arch marker (Ba) were determined. The reference plane was determined by least square method. Software Matlab 7.0 was used to calculate two-dimensional coordinate system. Based on this, a mathematical model was established to describe the dental and basal bone arch form and then to validate the mathematical model. Results (1) The mathematical model can be used to describe the dental arch form of skeletal classⅢmalocclusion, maxillary:Y=46.12 [1-(2X/70.99)2]1.052;mandibular:Y=39.16 [1-(2X/64.51)2]1.038. (2) The mathematical model can be used to describe the basal bone arch form of skeletal classⅢmalocclusion, maxillary:Y=43.14 [1-(2X/75.09)2]1.061;mandibular:Y=39.03 [1-(2X/60.63)2]1.021. (3) Fa was located at Ba labial side in the maxilla, the distance was positive. Fa was located at Ba lingual side in the mandibular, and the distance was negative. (4) The fitting correlation coefficient of beta-function curve and each tooth on the dental and basal bone arch of skeletal class Ⅲ malocclusion were greater than 0.7 (P<0.05). Conclusion In this study, the mathematical model can be used to describe the dental and basal bone arch form of the skeletal classⅢmalocclusion, which can guide further research.

Occlusal planes of Angle's class III malocclusion impact by anterior overbite / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the correlation between Angle's class III patients' occlusion plane and anterior overbite by controlling the changes in occlusion plane during orthodontic treatment.</p><p><b>METHODS</b>In total, 90 Angle's class III adult orthodontic patients were selected as the experimental group, and 30 normal adults were selected as the control group. According to the overbite, the class III patients were divided into three groups, and 14 indicators were measured. ANOVA and multiple comparison analysis were used to analyze the difference between class III patients, and linear analysis was used to analyze the correlation between anterior overbite and anterior-posterior occlusion plane.</p><p><b>RESULTS</b>In class Ill patients, posterior occlusion plane and anterior overbite size were negatively correlated (r = -0.24, P < 0.05), whereas anterior occlusal plane and anterior overbite size were positive correlated (r = 0.23, P < 0.05).</p><p><b>CONCLUSION</b>The shape of the occlusion plane varies in different anterior overbite patients. During orthodontic treatment in different overbite class III patients, the vertical height of the posterior teeth and the rotation of the occlusion plane should be controlled.</p>

Changes in Dental Arch and Hard and Soft Tissue Caused by the Self-Ligating Bracket and Conventional Bracket with Non-Extraction Treatment in Maxillary Mild-to-Moderate Crowding Cases / 天津医药

Objective To compare changes in dental arch and soft and hard tissue produced by the Damon Q self-ligating bracket and 3M metal bracket with non-extraction treatment in maxillary mild-to-moderate crowding cases. Meth-ods Eighty seven patients were selected in our study, who were assigned to 4 groups by the crowding degree of maxillary and appliance type:ⅠandⅡcrowding degree using Damon Q self-ligating bracket groups (41 cases);ⅠandⅡcrowding de-gree 3M metal bracket groups (46 cases). We measured lateral cephalometric radiographs and dental casts at both beginning and end of treatment. Paired t-tests and group t-tests were used in statistical analysis to compare the alteration in dental arch and soft and hard tissue. Results There was significant increase in width and length of maxillary dental arch by non-extraction treatment withⅠandⅡcrowding degree maxillary, but the results of both groups were not of statistical difference. To compare hard and soft tissue in two groups withⅡcrowding degree maxillary, the reduction of nasolabial angle, angle of inclination of upper lip, angle of upper lip and lower lip had obvious statistical significance and it is more prominent in self-ligating bracket group than in conventional bracket group. Conclusion Using non-extraction treatment, when maxillary crowding is moderate, ,Damon Q self-ligation bracket group result in more prominent changes of upper lip protrusion than 3M bracket with more marked crowding . Therefore, clinical doctors should pay more attention to choose bracket and treat-ment system for patients with marked crowding of maxillary dentition.

The characteristics of the arch form of skeletal Class II malocclusion / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the characteristics of the arch form of skeletal Class III malocclusion and provide references for diagnosis and treatment plan.</p><p><b>METHODS</b>7 indexes in dental casts of 47 patients with skeletal Class III malocclusion and 50 individuals with normal occlusion were measured respectively. And differences between corresponding upper and lower measurements were calculated. Independent samples t-test was employed for comparing between the two groups by SPSS 17.0.</p><p><b>RESULTS</b>Compared with normal occlusion sample, Class III malocclusion group had smaller anterior segment lengths and larger canine angles (P<0.05). Differences between upper and lower first premolar widths were larger in males with skeletal Class III malocclusion. And differences between upper and lower anterior segment lengths were smaller in males with skeletal Class III malocclusion (P<0.05).</p><p><b>CONCLUSION</b>Arch widths of patients with skeletal Class III malocclusion are basically normal. The lengths of anterior segment are smaller and the anterior arch forms are straighter.</p>

Effects of Fränkel II appliance on sagittal dimensions of upper airway in children / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The purpose of this study was to investigate the effects of Fränkel II appliance on the upper airway of children.</p><p><b>METHODS</b>The subjects consisted of 20 patients with Angle Class II, division I malocclusion (10 males and 10 females). The ages of all cases were ranged in 9-10 years. Each experimental subject was also served as self-control and cephalometric analysis was conducted.</p><p><b>RESULTS</b>Compared with the results of pretreatment, the distance of PNS-Ba, SPP-SPPW, P-T, V-LPW and the Mcnamara line increased remarkably.</p><p><b>CONCLUSION</b>The Fränkel II appliance can improve the sagittal dimensions of the upper airway in children.</p>

Comparison of craniofacial skeletal structures in adult high-angle and low-angle facial skeletal types / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The purpose of this study was to compare the differences of craniofacial characteristics of adult high-angle and low-angle facial skeletal types.</p><p><b>METHODS</b>The subjects consisted of 37 yellow race adults (17 high-angle, 20 low-angle). Fifty-three items of cephlometic radiographs were analyzed.</p><p><b>RESULTS</b>The angle of N-S-Ar and N-S-Ba, the distance of Ptm-A, Co-Go, Po-NB, and S-Go, and the thickness of the mandibular symphysis in high-angle group were smaller than these in low-angle group. The angles of SN-OP, FH-OP, PP-OP, SN-MP, FH-MP, PP-MP, S-Ar-Go, mandibular angle(Ar-Go-Me), Y-angel and SUM, the distance of S-Co, N-Me, and ANS-Me in high-angle group were greater than these in low-angle group. The index of FHI, N-ANS/N-Me, and N-ANS/ANS-Me were smaller, and ANS-Me/N-Me larger in high-angle group. Although the means of Go-Po and FH-RP were smaller in high angle group, but no statistical difference were found.</p><p><b>CONCLUSION</b>The craniofacial morphology of adult high-angle and low-angle facial skeletal types demonstrated significant differences, especially in lower facial form.</p>