Evaluation of correlation between Insertion Torque and Primary Stability of Dental Implants by Block Bone Test

Abstract

1. 연구목적 성공적인 임플란트의 식립과 장기적인 유지를 위해서는 여러 가지 요소가 충족되어야 하는데 그 중 임플란트의 일차 안정성은 매우 중요한 요소라고 할 수 있다. 임플란트의 일차 안정성에 대한 측정은 식립 토크 (insertion torque)로 측정할 수 있으며, 일반적으로 일차 안정성과 식립토크는 비례적인 관계를 가지고 있다고 여러 문헌에서 보고하고 있고 임상에서도 별 저항 없이 받아들여지고 있다. 하지만, 임상적인 관점에서 볼 때, 식립하고자 하는 골의 상태에 따라 이러한 비례적인 관계는 영향을 받을 수 있으며, 사람마다 골의 상태는 현저하게 다를 수 있으므로 결과가 일정하지 않게 나올 수 있게 된다. 그러므로 본 실험에서는 이렇게 영향을 미칠 수 있는 요소들을 제거하기 위해 cortical bone과 cancellous bone의 두께가 조절된 여러 상황의 bone block을 사용하여 임플란트 일차 안정성과 식립토크와의 관계를 재조명하고 일정하지 않은 조건에서도 이러한 관계가 성립하는지 알아보았다. 2. 연구방법 먼저, polyurethane foam으로 형성된 여러 조건들의 block bone위에 osteotomy를 형성하고 4.1mm의 직경과 11.5mm의 길이를 가진 임플란트 매식체를 식립하면서 식립토크를 측정하고, 일차 안정성은 resonance frequency analysis를 이용한 자기공명 임플란트 안정도 측정 장비 (Osstell Mentor)를 사용하여 ISQ (Implant Stability Quotient)를 측정하였다. 실험군은 다음과 같이 다섯 개의 실험으로 나누었고, 각 실험군마다 실험을 20회 반복하여 실시하여 상관관계를 분석하였다.

실험 1. 골밀도만 다른 homogeneous한 bone으로 구성된 군 실험 2. 골밀도가 같고 homogeneous한 bone으로 구성되었으나 마지막 드릴의 크기를 다르게 한 경우 실험 3. Cortical bone과 cancellous bone의 밀도를 일정하게 하고, cortical bone의 두께를 다르게 설정한 군 실험 4. Cortical bone의 두께를 1.5mm로, 또한 밀도르 일정하게 설정하고 cancellous bone의 두게를 다르게 설정한 군 실험 5. Cortical bone의 두께, 밀도 및 cancellous bone의 밀도를 일정하게 설정하고 마지막 드릴의 크기를 다르게 한 경우

3. 결론 임플란트의 일차 안정성은 식립 토크와 상관관계가 강하지만 골질의 영향도 많이 받는다고 할 수 있다. 그러므로 임플란트 식립 전 드릴의 사이즈, 골질의 평가 및 cortical bone의 두께를 미리 확인하는 것이 일차 안정성을 증가시키고 장기적인 성공률을 증가시키는 방법이라 할 수 있다. 주요어: 식립 토크, 임플란트 일차 안정성, block bone, 상관관계

Objective Primary implant stability which is implant stability obtained during dental implant placement is crucial for achieving osseointegration and long-term success of dental implants. Primary implant stability can be attained with elements including local bone quality and quantity, geometry of an implant, placement and surgical technique used and precise fit in the bone. Shorter healing periods are usually needed for implants with good primary stability. On the other hand, implants with poor stability need longer healing periods to achieve sufficient gains in secondary stability. This suggests the possibility of determining the length of the healing period on an individual basis, making implant treatment safer, more effective, and less-consuming in some cases. The purpose of the present study was to investigate the correlation between insertion torque and primary stability of dental implants using artificial bone blocks with different bone density and make-up to mimic different circumstances that are encountered in routine daily clinical settings.

Materials and Methods In order to prove upper points, the various size holes were made on the block bone of solid rigid polyurethane foam (Sawbones, USA) with bone density (#10 ~ #50) by surgical drill and measured the torque as inserting implant fixtures (Osstem SS II Implant System, Korea) and ISQ (Implant Stability Quotient) using Osstell Mentor (Osstell, Sweden). The experimental group under evaluation was subdivided into 5 subgroups according to the objectives. That result showed torque depends on the bone quality and the diameter of the last drill but the primary stability is constant regardless of the size of the last drill in hard bone and has the higher ISQ value as increasing bone density and contact area between implant and bone in soft bone. The insertion torque depends on the thickness of cortical bone layer and primary stability differs as the thickness of that. A one-way ANOVA was used to compare the mean insertion torque and ISQ values, respectively. Pearsons correlation coefficient was calculated to evaluate the correlation between insertion torque and ISQ at implant placement. A value of P < 0.05 was considered statistically significant. Experimental Design Exp. 1. Correlation between insertion torque and implant stability according to bone density. - Block bone density (homogeneous bone): #10, #20, #30, #40 - Final drill diameter: Ø3.6 - Measurement insertion torque and ISQ value (each sample: 20ea) Exp. 2. Correlation between insertion torque and implant stability according to final drill diameter (homogeneous bone). - Block bone density (homogeneous bone): #20 - Final drill diameter: Ø2.7, Ø3.0, Ø3.3, Ø3.6 - Measurement insertion torque and ISQ value (each sample: 20ea) Exp. 3. Correlation between insertion torque and implant stability according to thickness of cortical bone. - Cortical bone thickness: 0.5mm, 1.0mm, 1.5mm, 2.0mm - Block bone density: cortical bone (#50), cancellous bone (#20) - Final drill diameter: Ø3.6 - Measurement insertion torque and ISQ value (each sample: 20ea) Exp. 4. Correlation between insertion torque and implant stability according to cancellous bone density with cortical bone. - Cortical bone thickness: 1.5mm - Block bone density: cortical bone (#50), cancellous bone (#10, #20, #30) - Final drill diameter: Ø3.6 - Measurement insertion torque and ISQ value (each sample: 20ea) Exp. 5. Correlation between insertion torque and implant stability according to final drill diameter with cortical bone. - Cortical bone thickness: 1.5mm - Block bone density: cortical bone (#50), cancellous bone (#20) - Final drill diameter: Ø3.0, Ø3.3, Ø3.6, Ø3.8 - Measurement insertion torque and ISQ value (each sample: 20ea) Results In exp. 1 the mean insertion torque and ISQ value increased as the density of bone blocks increased, respectively. For exp. 2 the mean insertion torque values decreased as the final drill size increased, but this was not the case for the ISQ values. The mean insertion torque values in exp. 3 increased accordingly to the thickness of the cortical bone and the same was true for the ISQ values as well. For exp. 4 the mean insertion torque values increased as the cancellous bone density increased, but the correlation with ISQ values was weak. Finally, in exp. 5 the mean insertion torque decreased accordingly to final drill size, but the correlation with ISQ value was weak. Key words: insertion torque, implant primary stability, block bone, correlation