PURPOSE:To investigate the efficacy of a modified maxillary protraction appliance in patients of skeletal Class Ⅲ with crowding.METHODS:Forty patients with skeletal Class Ⅲ malocclusion were divided into two groups,with 20 patients in each group.The experimental group had molar in a neutral or distal relationship and applied a modi-fied maxillary protraction appliance,while the control group had molar mesial relationship and applied a conventional maxillary protraction appliance.Lateral cephalometric radiographs were taken before and after treatment in both groups for comparison.SPSS 22.0 software package was used for data analysis.RESULTS:The angle measurements taken before and after treatment showed a significant increase in SNA,ANB,SN-MP and U4-SN(P＜0.01),while SNB decreased(P＜0.01)in both groups.SN-OL changes were statistically different before and after treatment in the experimental group(P＜0.05).The sagittal measurements before and after treatment in both groups showed significant alterations in all(P＜0.05)but the length of the maxillary arch in both groups.For vertical measurements,Ul-PP,L1-MP,U4-SN,U6-SN,and ANS-ME all increased(P＜0.05),while the changes of U4-PP and U6-PP in the two groups before and after treatment were sta-tistically different(P＜0.05).Compared with the control group,the experimental group had a significantly increased maxil-lary arch length,a more remote location at U6,and a less variable molar relationship after treatment(P＜0.01).The two groups showed a variable amount of cephalometric measurements before and after treatment:the experimental group had a significant increase in maxillary arch length,a more remote position at U6,and a smaller change in molar relationship compared to the control group(P＜0.01).CONCLUSIONS:The modified maxillary protraction appliance showed good re-sults for maxillary protraction and pushing the molar distally in patients with skeletal Class Ⅲ with crowding at neutral or distal molar relationship.
Skeletal Class Ⅲ malocclusionModified maxillary protractionCrowdingMolar distalization
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