| Summary: | 碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 101 === Abstract
Research goal
The purpose of this study was to investigate the insertion torque of 2.1 mm diameter MDI implants placed with different drilling protocols in artificial bone blocks of different qualities,and in ilium bone of pig.
Material and method
＜Artificial test block＞
Low to high density cancellous bone without cortical coverage were simulated using 10 pounds per cubic foot (pcf) (density: 0.16 g/cc), 20 pcf (0.32 g/cc), and 30 pcf (0.48 g/cc) polyurethane foam test blocks. Cancellous bone with a thin layer of cortical bone were simulated with laminated test blocks using a combination of 1 or 2 mm 50 pcf (density: 0.80 g/cc) polyurethane layer on 10, 20, and 30 pcf blocks. After a site preparation, mini implants (MDI,mini dental implant，IOB-13，Sendax 3M USA) were inserted into the testing blocks and insertion torque was recorded with every 0.5 mm implant advancement. In each type of test blocks, we explored the optimal drilling protocol by drilling with 1.1 mm drill in 4 mm depth first and testing the MDI insertion torque, and sequenced drilling protocols of a deeper drilling depth or a larger diameter (1.5 mm) drilling were only tested if the insertion torque was greater than 45 Ncm. Each drilling protocol was repeated for 5 times. Sequenced drilling protocols tested were listed below. The “1.1(number 1)-1.5(munber 2)” mean using the 1.1 diameter drill to the depth of (munber 1) mm, then using the 1.5 mm diameter drill to the depth of (munber 2) mm ：
★ 1.1(4)； ★ 1.1(7)； ★ 1.1(10)； ★ 1.1(13)；
★ 1.1(4)-1.5(4)；★ 1.1(7)-1.5(7)；★ 1.1(10)-1.5(10)；
★ 1.1(13)-1.5(4)；★ 1.1(13)-1.5(7)；★ 1.1(13)-1.5(10)；
★1.1(13)-1.5(13)。
＜ilium bone＞
In the ilium bone block test,the bone was sorted by cortical bone thickness roughly, and devided into 0~1, 1~2, 2~3 mm groups. Drilling protocol tested were listed below:
★ 1.1(4)；★ 1.1(13)-1.5(4)；★ 1.1(13)-1.5(7)；★ 1.1(13)-1.5(10)；
★1.1(13)-1.5(13)。
Each drilling protocol was repeated for 5 times, and insertion torque was recorded with every 0.5 mm implant advancement .And the bone block would use the CT scan to check the accurate cortical bone thickness and HU value for bone quality.
Result:
In the test block with density of 10 pcf and 0~2mm lamination, the final insertion torquefo rough surface（ITRF）would not exceed 35 Ncm, even with the most conservative site preparation of 1.1 mm drilling in 4 mm depth. In the block with density of 30 pcf and 0~2mm, the insertion torque was beyond 50 Ncm before the implant fully seated and a deeper or wider site preparation was needed. In these tested blocks, it was observed that deeper drilling usually could not reduce the insertion torque efficiently and a larger diameter preparation to reduce to insertion torque was needed.
In the test group of pig ilium bone, the ITRF of 0~1 mm group did not reach 35 Ncm, even using the most conservative protocol. In the 1~2 and 2~3 mm group, the ITRF could control in the range of 35~45 Ncm when using different protocol, but during the procedure of placement, the the maximum ITR(insertion torque of rough surface) may beyoud 45 Ncm, it should be noted.
Conclusion:
The data suggest that drilling protocols can be and should be developed according to different bone quality for MDI implants to avoid implant fracture and achieve ideal insertion torque.
Key word：Mini dental implant、insertion torque、drilling protocol.
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