ABSTRACT
Objective@#To investigate changes in the three⁃dimensional position of the maxillary canine during the distal movement of the maxillary first molar by a mini⁃implant combined with a CD appliance.@*Methods@#Ten typodont models of class II malocclusion were selected, and one side was randomly chosen as the experimental group. The CD ap⁃ pliance was bonded to the maxillary canine and first molar of the experimental group, and 1.2 mm stainless steel wire was bent as the anchorage, which was fixed on the model to simulate mini⁃implants implanted in the zygomatic alveolar ridge. Then, 180 g orthodontic force was applied to the canine of the experimental group; the other side was recognized as the control group and was not used for strengthening. Six mini⁃implants were implanted in different parts of the mod⁃ el and used as a reference before and after the experiment. The models were placed in an incubator and heated at 56 ℃ in a water bath for 2 min. The models were scanned before and after thermostatic water bath treatment with a 3⁃shape scanner. Then, the digital models were overlapped through the reference points, and the positions of the canines and first molars were measured before and after the experiment.@*Results@#The sagittal movement distance of the first molar in the experimental group was ( 0.25 ± 0.33) mm, and the vertical movement distance was (0.25 ± 0.28 )mm, which was significantly different from the control group (P < 0.05), while the transverse change was not significantly different (P > 0.05). There was no significant difference in the root position of the first molar in the experimental group (P > 0.05). The lateral and vertical displacement distances of the maxillary canine crown in the experimental group were (4.03 ± 2.11) mm and (1.86 ± 1.01) mm, respectively, which were significantly different from those in the control group (P < 0.001), while the sagittal changes showed no significant differences (P > 0.05). In the experimental group, there was no significant difference in the position of the apex of the maxillary cusp (P > 0.05).@*Conclusion@#Our in vitro study showed that the maxillary canines inclined buccally accompanied by a small amount of intrusion during molar distaliza⁃ tion by a mini⁃implant combined with a CD appliance.
ABSTRACT
1 5 cases,5 males and 1 0 females,aged 1 6-26 years,with ClassⅡdivision maxillary mild to moderate protrusion were includ-ed.Damon III appliance was used to arrange the upper and lower dentition.Stainless steel micro-screw implants were implanted in zygomatic crest to provide the best bone anchorage,stainless steel rectangular wire was used for maxillary complete dentition continuous ligation and maxillary teeth distal movement.X-ray cephalometry study showed that U1-NA(°)reduced by 2.51 ±1 .52(P0.05),centric jaw relation of bilateral molar was obtained.
ABSTRACT
Objective:To simulate the instantaneous distal moving trend of the maxillary first molar based on the three-dimensional finite element mode(l3-FEM)of Forsus distalizing the maxillary first molar with some visco-elastic-plastic characters and explore the favorable loading mode of molar distal movement in Forsus in order to provide biomechanical basis for clinical practice.Methods:A male patient with ClassⅡmalocclusion was selected.The 3-FEM of Forsus distalizing the maxillary first molar was built through spiral CT scanning,Mimics8.0,and Abaqus6.5 software.This study simulated instantaneous distal moving process of the maxillary first molar under three dif-ferent loading modes(loading force was 300 g,point of force was on the center of the crown's buccal surface,loading time was 1s),which included a distalizing force,a distalizing force+counterrotation moment,a distalizing force+countertipping moment+counterrotation moment.Results:When Forsus distalized the maxillary first molar,different loading modes lead to different PDL stress distributions.When the model was added by a distalizing force,the maxillary first molar would be relatively seriously inclined;when added by a distalizing force +counterrotation moment(Mt/F=9),the maxillary first molar would be relatively seriously rotated and when added by a distalizing force+ countertipping momen(tMt/F=9)+counterrotation momen(tMr/F=5),the distal surface of the PDL would bear the lightest stress,and the first molar would achieve approximate translation movement.Conclusion:When mandible is guided forward by Forsus,the maxillary first molar would achieve better molar translation effect if added certain countertipping and counterrotation moment