Keun-Chul Cho1, Seung-Hak Baek. 1. Department of Orthodontics, School of Dentistry, Seoul National University, Chongro-Ku, Seoul, Korea.
Abstract
OBJECTIVE: To investigate the effects of orthodontic mini-implant (OMI) shape and predrilling depth on the mechanical properties of OMIs during the insertion procedure. MATERIALS AND METHODS: A total of 30 OMIs (self-drilling type, 7 mm in length; Biomaterials Korea Inc) were allocated into six groups according to OMI shape (cylindrical and tapered type) and pre-drilling depth (control, 1.5-mm and 3.0-mm predrilling; predrilled with a drill-bit [1 mm in diameter]): C-con, C-1.5, C-3.0, T-con, T-1.5, and T-3.0 groups (N = 5 per group). The OMIs were installed in artificial bone blocks with two layers that simulated the cortical and cancellous bone (Sawbone®, Pacific Research Laboratories Inc). Total insertion time (TIT), maximum insertion torque (MIT), total insertion energy (TIE), and inclination of the time-torque graph (INC) were measured. RESULTS: Within the same shape group, although predrilling groups exhibited shorter TIT than control groups (control vs 1.5; control vs 3.0; all P < .05), there was no difference in TIT between 1.5-mm and 3.0-mm predrilling groups. MIT and TIE decreased in the order of control, 1.5-mm predrilling, and 3.0-mm predrilling (control vs 1.5; 1.5 vs 3.0; all P < .05), but INC revealed a pattern of increase from control to 1.5-mm predrilling and of decrease from 1.5-mm predrilling to 3.0-mm predrilling within the same shape group (control vs 1.5, 1.5 vs 3.0, all P < .05). The MIT and INC of C-con were smaller and less steep than those of T-con (P < .01 and P < .05, respectively). In the same predrilling depth, no differences were observed in MIT, INC, and TIE between cylindrical and tapered groups. CONCLUSION: In cases of thick cortical bone, predrilling might be an effective tool for reducing microdamage without compromising OMI stability.
OBJECTIVE: To investigate the effects of orthodontic mini-implant (OMI) shape and predrilling depth on the mechanical properties of OMIs during the insertion procedure. MATERIALS AND METHODS: A total of 30 OMIs (self-drilling type, 7 mm in length; Biomaterials Korea Inc) were allocated into six groups according to OMI shape (cylindrical and tapered type) and pre-drilling depth (control, 1.5-mm and 3.0-mm predrilling; predrilled with a drill-bit [1 mm in diameter]): C-con, C-1.5, C-3.0, T-con, T-1.5, and T-3.0 groups (N = 5 per group). The OMIs were installed in artificial bone blocks with two layers that simulated the cortical and cancellous bone (Sawbone®, Pacific Research Laboratories Inc). Total insertion time (TIT), maximum insertion torque (MIT), total insertion energy (TIE), and inclination of the time-torque graph (INC) were measured. RESULTS: Within the same shape group, although predrilling groups exhibited shorter TIT than control groups (control vs 1.5; control vs 3.0; all P < .05), there was no difference in TIT between 1.5-mm and 3.0-mm predrilling groups. MIT and TIE decreased in the order of control, 1.5-mm predrilling, and 3.0-mm predrilling (control vs 1.5; 1.5 vs 3.0; all P < .05), but INC revealed a pattern of increase from control to 1.5-mm predrilling and of decrease from 1.5-mm predrilling to 3.0-mm predrilling within the same shape group (control vs 1.5, 1.5 vs 3.0, all P < .05). The MIT and INC of C-con were smaller and less steep than those of T-con (P < .01 and P < .05, respectively). In the same predrilling depth, no differences were observed in MIT, INC, and TIE between cylindrical and tapered groups. CONCLUSION: In cases of thick cortical bone, predrilling might be an effective tool for reducing microdamage without compromising OMI stability.
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