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Objective To evaluate the influence of stress distributions on bone-anchored maxillary protraction at different protraction sites, so as to guide patients to choose an optimal protraction site in clinic. Methods A three-dimensional (3D) finite element model of child head with implant anchorages was establised. Four protraction sites were set according to the position of implant installation. Working condition 1: the alveolar bone at the intersection of distal 2 mm of primary lateral incisor crown distal surface and gingival cervical margin to 5 mm. Working condition 2: the alveolar bone at the intersection of mesial 2 mm of maxillary first primary molar crown mesial surface and gingival cervical margin to 5 mm. Working condition 3: the alveolar bone at the intersection of mesial 2 mm of maxillary first molar crown mesial surface and gingival cervical margin to 5 mm. Working condition 4: the alveolar bone at the intersection of distal 2 mm of maxillary first molar crown distal surface and gingival cervical margin to 5 mm. The finite element models were loaded with 500 g protraction force at each side with 30° forward direction to the occlusal plane. Stress distributions on each suture were analysed. Results The maximum stress of frontomaxillary suture was in working condition 2 (1 477-28 190 Pa). The maximum stress of nasomaxillary suture was in working condition 1 (5.296-924 Pa). The maximum stress of zygomaticomaxillary suture was in working condition 4(394.7-13 130 Pa). The maximum stress of zygomaticofrontalis suture was in working condition 4 (495.2-31 690 Pa). The maximum stress of zygomaticotemporal suture was in working condition 3 (1 148-15 870 Pa). The maximum stress of medianpalatine suture was in working condition I (6.479-730 Pa). Conclusions When the protraction sites are set in distal maxillary primary lateral incisor and mesial maxillary first primary molar, it is of positive significance to improve the concave profile, especially in nose root. When the protraction sites are set in mesial or distal maxillary first molar, it is of positive significance to improve the concave profile, especially in maxillary basal bone of the midface.
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Objective:To observe the effects of the vertical holding appliance (VHA) in the extraction treatment of patients with hyperdivergence.Methods:40 hyperdivergent patients orthodonticly treated by 4 first premolar extraction with(VHA group) and without VHA(control group) (n =20) respectively.Cephalometric radiographs were taken before and after orthodontic treatment and measured digitally by Winceph 8.06 software.Results:After treatment,the L6-MP,S-Go,N-Me,ANS-Me increased in the VHA group(P ＜ 0.05).The MP-SN,Y-axis,U1-PP,U6-PP,L6-MP,S-Go,N-ANS,N-Me,ANS-Me,ANS-Me/N-Me increased and the S-Go/N-Me decreased in the control group(P ＜0.05).The changes of the MP-SN,Y-axis,U6-PP,L6-MP,N-Me,ANS-Me,ANS-Me/N-Me,S-Go/N-Me were smaller in the VHA group than those in the control group (P ＜ 0.05).Conclusion:VHA is effective in the control of the height of molars in the extraction treatment of patients with hyperdivergence.
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Objective:To explore the influence of buccal corridor of Han people on smile esthetics.Methods:An attractive adult male and a adult female were selected as the models.Buccal corridor was altered digitally with slider technology of Adobe Flash CS4 to obtain a continuous range of buccal corridors(0% -25%).96 orthodontists aged 35.1 ±7.2 years and 96 laypersons aged 37.3 ± 5.1 years were chosen as the raters.The minimum tolerable value(A%),the ideal value(B%)and the maximum tolerable value (C%)of buccal corridor of the models were statistically analyzed.Results:In the orthodontist groupA,B and C of the male model were 5.00 ±0.1 7,9.75 ±2.77 and 1 5.00 ±2.84,in layperson group were 4.79 ±1 .00,9.20 ±3.08 and 1 5.05 ±2.91 ,respec-tively;in orthodontist group,A,B and C of the female model were 3.92 ±0.1 7,1 1 .87 ±2.77 and 1 5.82 ±2.84,in layperson group were 4.00 ±1 .00,1 2.05 ±3.08 and 1 5.1 1 ±2.91 ,respectively(all data between groups,P >0.05).The ideal buccal corri-dor value(%)of the male and female models were 9.48 ±2.73 and 1 1 .96 ±1 .99 respectively(P <0.05).Conclusion:There is no difference between orthodontists and laypersons for buccal corridor esthetic judgment.The ideal esthetic buccal corridor size of male and female is different.
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Objective:To compare the smile characteristics of the subjects with different types of malocclusion.Methods:1 80 sub-jects with classⅠ(n =60),classⅡ(n =60)and class Ⅲ(n =60)malocclusion at the age of 1 8 to 25 years were included.The smile vidioes and posed smile images of the subjects were acquired.Smile quantitative evaluation indexes were measured and analysed.Re-sults:There were statistical differences in smile indexes and the amount of the gingival exposure in classⅡ subjects between the male and female(P classⅠ >classⅢ,smile index of class Ⅲ was greater than that of class Ⅰ and class Ⅱ,the teeth exposure of class Ⅱ was less than that of class Ⅰand class Ⅲ.Conclusion:Malocclusion types may affect smile characteristics.
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Objective:To analyze the dental and mandibular asymmetry of adults with Class Ⅱ subdivision malocclusion.Methods:The jaw bones of 30 adults with Class Ⅱ subdivision malocclusion(case group)and 30 with normal-occlusion(control group)were scanned by CBCT.Linear and angular comparison was conducted between the two groups.Results:Dental midline deviation was ob-served in case group,mostly in mandibular arch (60%).The development of Class Ⅱ molar relationship correlated mainly to distally positioned mandibular molar on Class Ⅱ side.Conclusion:In the adults with Class Ⅱ subdvision malocclusion odontogenic asymme-try is the major factor,bony asymmetry is the miner.
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The treatment of low mesioangular impaction of second molar is difficult because of the little crown exposure and the influence of the third molar.We used modified lingual arch as a stronger anchorage to upright the lower second molars combined with manufactured spring,the treatment procedure is simple and effective.
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Objective:To compare the efficacy of casting frame and traditional fixed maxillary protraction appliances in the correc-tion of skeletal Ⅲ malocclusion in mixed dentition.Methods:30 cases with Class Ⅲ malocclusion in mixed dentition were random-ly divided into 2 groups.Casting frame maxillary protraction appliance was applied in group 1 (1 5 cases)and traditional fixed maxil-lary protraction appliance in group 2(15 cases).X-ray cephalometric examination results before and after treatment,treatment time, and the number of visit in 2 groups were analyzed with SPSS 1 3.0.Results:The treatment time in group 1 and 2 was (7.03 ±1 .32) and (9.07 ±1 .31 )months(P <0.05),the number of visiting was (8.00 ±1 .46)and (10.47 ±1 .85)(P <0.05),the cephalomet-ric measurement change of △U1 -SN was (3.85 ±0.95)°and (5.25 ±0.95)°(P <0.05),respectively.Conclusion:Casting frame protraction appliance is an efficient and practical intraoral device,which can prevent anterior upper teeth inclined to labial.
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<p><b>OBJECTIVE</b>To evaluate the morphology and position of condylar processes in skeletal Class III adult patients with mandibular deviation.</p><p><b>METHODS</b>Twenty skeletal Class III adult patients with mandibular deviation were selected as the deviated group and twenty adults with normal occlusion were selected as the control group. Cone- beam CT (CBCT) scans of their temporomandibular joints were taken. The original data were reconstructed and rebuilt. A series of measurements of the condylar morphology and location were performed. The collected data were analyzed using paired t- test.</p><p><b>RESULTS</b>In the deviated group, the deviated sides were smaller than the contralateral sides in the perpendicular height, volume, maximum area of axial plane and the height of condylar head. The contralateral condyle was positioned more posteriorly and laterally [(0.35 ± 0.10) and (0.58 ± 0.18) mm] than the deviated condyle (P < 0.05).</p><p><b>CONCLUSIONS</b>Adult skeletal Class III patients with mandibular deviation had some extent of condyle asymmetry in both morphology and location.</p>