Establishment of the craniofacial three-dimensional finite element models with the sutures defined alone / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To develop a child craniofacial three-dimensional (3D) finite element model (FEM) with sutures defined alone.</p><p><b>METHODS</b>The CT data for this study was developed from sequential computed tomography scan images taken at 0.625 mm intervals of an 8 years children skull. Data set was imported into Mimics 10.0 and processed with Geomagic 9.0, and exported as initial graphics exchange specification(IGES) files. The IGES files were then imported into Ansys 13.0 to set up two FEM with or without the median palatine suture being opened. The FEM contained nine craniofacial sutures and eight teeth which were defined alone.For simulating orthopedic maxillary protraction, three forces (F1-F2) were loaded on FEM.F1(1 N) was loaded at 1 cm above the geison. F2(1 N) was loaded at articular fossa of temporal bone. F3(2 N) was directed anteriorly and paralleled with occlusal plane near the canine. The stress distribution and the values distributed in each point gained in the two models were compared.</p><p><b>RESULTS</b>Two craniofacial 3D FEM of the child were developed with the median palatine suture opened or not .With median palatine suture being opened or not, the two models showed the similar von Mises stresses (VMS). The distribution of the VMS was in the bridge of the nose and dextro-ala nasi.When the median palatine suture was opened, the max VMS value was 18916.00×10(-4) MPa which appeared in the nose point and the min VMS value was 1.61×10(-4) MPa which appeared in the maxillary central incisor point. At the same time, the max stress value at the direction Y was -3985.30×10(-4) MPa and appeared in the frontomaxillary suture point, and the min Y value was 0.08×10(-4) MPa which appeared in the maxillary central incisor point. When the median palatine suture was not opened, the max VMS value was 19 244.00×10(-4) MPa and appeared in the nose point. The min VMS value was 1.62×10(-4) MPa and appeared in the maxillary central incisor point. At the same time, the max stress value at the direction Y was -4258.20×10(-4) MPa and appeared in the frontomaxillary suture point, and the min Y value was 0.08×10(-4) MPa which appeared in the maxillary central incisor point.</p><p><b>CONCLUSIONS</b>To define the sutures as entities alone contributed to develop child craniofacial 3D FEM which consist nine sutures. There was tiny difference in stress distribution in both the VMS and in Y direction with the median palatine suture being opened or not.</p>

Effect of maxillary protraction with or without rapid palatal expansion in treating early skeletal Class III malocclusion / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the effectiveness of treatment with maxillary protraction with or without rapid palatal expansion (RPE) for skeletal Class III malocclusion in mixed dentition.</p><p><b>METHODS</b>A total of 31 children with Class III malocclusion in mixed dentition were selected, and 15 (group A) received maxillary protraction treatment with RPE, the other 16 (group B) received maxillary protraction without RPE. Cephalometric films were taken before and after treatment, and traditional and Pancherz analysis were used.</p><p><b>RESULTS</b>The average duration of treatment was 10.14 months in group A and 9.77 months in group B respectively (P>0.05). According to Pancherz analysis, maxillary basal bone moved forwards by 2.99 mm in group A and 3.33 mm in group B respectively (P>0.05), mandibular basal bone moved backwards by 0.07 mm in group A, while forwards by 0.80 mm in group B (P>0.05), the overjet increased by 4.51 mm in group A and 6.37 mm in group B respectively (P<0.05), and the molar relationship improved by 4.97 mm in group A and 4.73 mm in group B respectively (P>0.05). The effects were clinically satisfactory in the both groups. Lower molar moved forwards by 1.18 mm in basal bone in group A, while backwards by 1.20 mm in group B (P<0.05). Traditional cephalometric analysis showed no statistic differences between the two groups except that upper incisior showed greater procline in group B than in group A (P<0.05).</p><p><b>CONCLUSION</b>The study shows that maxillary protraction treatment, with or without RPE, is clinically satisfactory to correct early skeletal Class III malocclusion.</p>

Rapid canine distalization through distraction of the periodontal ligament after reducing interseptal bone resistance / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effect of rapid canine distalization through distraction of the periodontal ligament after reducing interseptal bone resistance.</p><p><b>METHODS</b>Twenty canines in 11 patients who needed first premolar extractions were involved. A tooth-borne, custom-made distractor was bonded right after the first premolar extraction and the interseptal bone resistance reduction. Three days post-operatively, the distractor was activated 0.1 mm three times a day. Orthodontic models, panoramic radiographs, periapical radiographs, electrical vitality test were assessed pre- and post distraction procedure and 3 months after the completion of the procedure.</p><p><b>RESULTS</b>The distraction procedure was completed in 18 to 35 days [mean (25.6 +/- 4.7) days], with the distal displacement of the canines ranging from 3.53 to 8.29 mm [mean (5.56 +/- 1.32) mm]. The canines showed a mean of 12.20 degrees distal tipping and 18.53 degrees rotation. The anchorage teeth showed an average of (0.76 +/- 0.75) mm mesial movement. The mesial contact point of incisors showed a mean of (0.67 +/- 0.55) mm lingual movement. There was no significant root resorption or long-time change on pulp vitality after distraction.</p><p><b>CONCLUSIONS</b>The canine distalization through distraction of the periodontal ligament after reducing interseptal bone resistance was an effective approach to move canines rapidly.</p>

Study on effect of snore guard to upper airway structure of normal occlusion people by magnetic resonance imaging / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the imagery changes of the upper airway and the surrounding soft tissues of local adults with non-apnea who used snore guard and to provide experimental data for the clinical diagnosis and treatment of obstructive sleep apnea syndrome (OSAS).</p><p><b>METHODS</b>Thirty students with non-apnea from Hebei medical university were chosen, and magnetic resonance imaging (MRI) was used to measure the changes of the upper airway and the surrounding soft tissues after snore guards were used. SPSS 105 software was used to analyze statistically.</p><p><b>RESULTS</b>After the snore guard was put into oral cavity, the change of the average section and volume of the nasopharynx, the palatopharynx, the hypopharynx and the glossopharynx were statistically significant. The average sagittal size, the average horizontal size of the nasopharynx, the palatopharynx, the hypopharynx and the glossopharynx were increased statistically. The ratio of sagittal size, the horizontal sizand the in the hypopharynx and the glossopharynx changed statistically important. There was a decrease of the soft palate, the shape, the height, and the length of the tongue, the difference was statistically significant. The results demonstrated that snore guard affected the upper airway mainly by changing the volume and the shape of the upper airway, there was an obvious increase of the pharynx. The results also showed that snore guard could increase the width (both sagittal and horizontal) of the upper airway and could change the shape of the surrounding soft tissues, which caused air way more smooth. Snore guard could make the indexes of soft palate and tongue change decreasingly, resulted in the straight stand up of the tongue and the forwardness of the soft palate.</p><p><b>CONCLUSION</b>Snore guard is an effective and convenient instrument for treating the patients with OSAS.</p>

Effect of early treatment with the Twin-block appliance / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the effectiveness of early treatment with the Twin-block appliance for the developing Class II division 1 malocclusion.</p><p><b>METHODS</b>A Total of 30 children with Class II division 1 malocclusion, 18 (8 male, 10 female) out of which received treatment with the Twin-block appliance, the other 12 cases (6 male, 6 female) without treatment served as control group. Cephalometric data were collected at the start and the end of the study and statistical analysis were applied.</p><p><b>RESULTS</b>Except the factor of growth, treatment with the Twin-block appliance resulted in reduction of ANB (1.55 degrees), overjet (5.46 mm) and correction of molar relationship (4.07 mm). These changes were due to the change of Pg/OLp, Co/OLp and mandibular length. The change of A/OLp was not significant. The skeletal effect contributing to the change on overjet and molar relation were 58% and 78% respectively.</p><p><b>CONCLUSION</b>Early treatment with the Twin-block appliance was effective in reducing ANB angle, overjet and correction of molar relationship. The changes were mainly profit from the favorable skeletal change of mandible, especially from its length, while the effect on maxillary was not significant.</p>