Comparison of the three different methods of pilot hole application to the stability of miniscrew

The aim of this study is the in-vitro evaluation and comparison of the effects of pilot hole application using Er:YAG and burs (pre-drilling) and self-drilling miniscrew applications on the stability of miniscrews.Miniscrews are applied to bone samples of bovine in our study. CT (Computerized Tomography) images of bone samples are taken for the evaluation of cortical bone thickness. After the identification of cortical bone thicknesses, bone samples were homogenously divided into 3 groups, 24 miniscrews were placed to each bone sample. 72 pieces of conical self-drilling minscrews (Trimed, Ankara, Turkey) 1.6 mm in diameter and 8 mm in length were used. The first study group pre-drilling was applied (pilot hole) perpendicular to the bone surface with a physiodispenser at 30 rpm, drill diameter was 1.3 mm and the pilot hole was 3 mm in depth. The second group was the Er:YAG laser group. Pilot hole was applied with Syneron LITETOUCHTM Er:YAG laser (Syneron Dental Lasers Industrial Zone, Elite, Israel) under 40 - 50 ml/second air water sprey, perpendicular to the bone surface, spot size was 1.3 mm, distance from the bone surface was 2 mm, pulse energy 300 mJ, power 3.6 Watt, application period 20 seconds and frequency was 12 Hz. In the control group miniscrews were applied with self-drilling method perpendicular to the bone surface. In order to evaluate the maximum insertion torque values the last 2 mm of the screws was not turned. 1 mm of the left distance was used for determining the insertion torque. Removal torque values are measured with the counter-clockwise rotation of the torque screwdriver.According to the findings of this study, self-drilling (17,76±1,5) miniscrews had higher maximum insertion torque values than pre-drilling (10,49±1,36) and laser (9,29±1,3) groups. Also pre-drilling (10,49±1,36) group maximum insertion torque values were significantly higher than laser (9,29±1,3) group. When removal torque values of three groups were evaluated, the values of removal torque of self-drilling (16,95±1,52) group were higher than pre-drilling (10,2±1,19) and laser (9,8±1,09) groups; however, there was no statistically significant difference between pre-drilling and laser groups.The main result of our study was the maximum insertion torque values of laser group were significantly lower than the self-drilling and pre-drilling groups. The removal torque values of laser group were lower than the self-drilling group and similar to the values of pre-drilling group.