Effect Of Laser Pre-drilling On Insertion Torque Of Orthodontic Miniscrews

  • Mr Chung Ju Hwang, Department of Orthodontics, Yonsei University, College of Dentistry, Korea
  • Mr Jung Yul Cha, Department of Orthodontics, Yonsei University, College of Dentistry, Korea
  • Mr Geun Hwa Kim, Department of Orthodontics, Yonsei University, College of Dentistry, Korea
  • Mrs Jeong Won Yoon, Department of Orthodontics, Yonsei University, College of Dentistry, Korea
  • Mr Sung Hwan Choi, Department of Orthodontics, Yonsei University, College of Dentistry, Korea

The aim of this study is to evaluate the clinical usefulness of laser pre-drilling by using Er,Cr:YSGG laser. Laser pre-drilling holes were made on the mandibular bone of a beagle dog with different laser irradiation time and tip diameter. Micro CT was taken to measure the maximum diameter and the depth of the pre-drilling holes. After pre-drilling, 3 miniscrews were placed without pre-drilling as a control group. Among the holes drilled with 0.4 mm,0.6 mm diameter tip,total 18 miniscrews were placed as experimental groups which were randomly selected from each group. Maximum insertion torque was measured during installation and following results were obtained.
1.Laser pre-drilling holes showed conical shape.
2.To perforate 1 mm thickness cortical bone, it takes at least 9 seconds with 0.6 mm diameter tip and the diameter of the hole was 0.8 mm at that time.
3.The maximum diameter of pre-drilling hole increased with longer laser irradiation time but there were no significant differences. With 0.6 mm diameter tip, it showed larger maximum pre-drilling hole diameter than with 0.4 mm diameter tip(P<0.05).
4.The depth of pre-drilling hole increased with longer laser irradiation time and larger tip diameter(P<0.05).
5.When laser pre-drilling with 0.4 mm diameter tip, insertion torque decreased with longer laser irradiation time(P<0.05), but when using 0.6 mm diameter tip, there was no significant difference by irradiation time.
When miniscrews are inserted by laser pre-drilling with Er,Cr:YSGG laser, it is important to select proper tip diameter and laser irradiation time according to the thickness of cortical bone.