1.Changes in canine position during maxillary molar distalization with mini-implant and CD appliance: an in vitro study
CHEN Jianming ; TAN Yuanhuan ; HU Yaozheng ; PENG Jing
Journal of Prevention and Treatment for Stomatological Diseases 2020;28(11):705-709
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.