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[Influence of periodontal ligament injury on initial stability for immediately loaded mini-implant]
Hong-Ning Wang1, Dong-Xu Liu, Chun-Ling Wang
1Dept. of Orthodontics, Stomatological College of Shandong University, Jinan 250012, China.
Objective:
To evaluate the influence of periodontal ligament (PDL) injury on initial stability for immediately loaded mini-implant anchorage.
Methods:
The sample consisted of 153 adult patients with maxillary protrusion deformity. Guiding by the positioning device designed by Choi, 306 mini-implants were inserted by self-tapping in the upper right and left buccal areas between the first molars and second premolars. The mini-implants were divided into two groups according to CT scanning. The mini-implant was absolutely separated from PDL (group I), the mini-implant appeared to touch or overlay on PDL, but not contact to the adjacent roots (group II). If orthodontic force could be applied to the mini-implants for four months, the mini-implant was recorded as successful anchorage. After immediate loading for four months, the analyses were completed by SPSS 9.0 software.
Results:
Of the 306 inserted mini-implants, 162 were absolutely separated from PDL, 136 appeared to touch or overlay on PDL, but not contact to the adjacent roots, and 8 were excluded from this study because of injury to the adjacent root. The success rates of group I and II were 87.0% and 65.4% respectively. There were significant differences in the success rates between the two groups (P<0.001). The differences between the two groups in distribution of the upper right and left area had statistical significance (P<0.05).
Conclusion:
PDL injury is one of the main reasons leading to early loosening of the mini-implant.
