| Background: Immediate loading after implant insertion has been a hot subject in the field of dental implantology, and this requires high quality of implant primary stability. And advanced inserting techniques, including inserting methods and inserted bone densities, can make good primary stability.Recent studies show that the researches about implant primary stability and immediate loading were mostly on how primary stability influence immediate loading and the evaluation of immediate loading achievement ratio by animal experiments, clinical research and three-dimensional finite analysis. However, there lack primary researches on how inserting force influence primary stability, as well as how bone densities influence implant stability under changed magnitude and frequency of the loading forces.Objectives:①To create vitro models for implant primary stability research, including inserting torque models and immediate loading models.②To compare implants stability quotient (ISQ) in vitro by resonance frequency analysis (RFA) when using different inserting torque values (ITVs).③To study the influences of bone density on implant primary stability when applying different magnitude and frequency of the loading forces. And then discuss the influential factors on implant primary stability and provide some theoretical basis for clinical practice.Methods:①Create bone models for different ITVs by preparing implant holes on fresh costal bones of cattle with drills of different diameter, hardness, and whether plus screws or not.②Compare ISQs of the different ITV models. Compare the ISQ changes of the different ITV implants after 4 and 24 hours of insertion.③Compare the ISQ changes after being loaded simulative masticatory forces of 25N and 50N on the implants separately, and the forces were applied 1800 times at first and then increased to 3600 times.④Compare the ISQ changes after being loaded simulative masticatory forces of 25N and 50N on the implants when inserted into bi-cortical bone condition (both the cervical and partial body parts of the implants are cortical bone) when applied on the force first of 1800 times and then 3600 times.Results:(1)ITV models and vitro loading models could be founded, and different ITVs were acquired by the different diameters between implant holes and implants. For the hole diameters were changeable according to different drill diameters, but the implant diameter was unchangeable.①We acquired ITV higher than 35N?CM with the drill which could made 3.3mm diameter holes that bear most press when inserting the 4.3mm diameter implant.②We acquired ITV between 25 to 35N?CM with standard drill with which the diameter equals to the diameter of implant that minus its screws, and this kind of implant holes only bear the press created by the implant screw.③We acquired ITV lower than 25N?CM with standard and screw drills with which the diameter equals to the implant diameter. (2)When inserted with different ITVs of the three above, the according ISQs were 76.33±3.59,79.75±3.81 and 82.16±2.46,and the first one was statistically lower than the other two(P<0.05), and the other two group were no statistical difference(P>0.05). (3)①When the ITV was lower than 25N?CM, the 4h and 24h's later ISQs were respectively 77.75±2.49 and 78.29±3.20,and they weren't statistically different with the inserting ISQ(76.33±3.59)(P>0.05).②When the ITV was 25-35N?CM, the 4h and 24h's later ISQs were respectively 82.37±2.53 and 82.45±2.73,and they were statistically higher with the inserting ISQ(P<0.05),but they themselves didn't have statistical difference(P>0.05)③When the ITV was higher than 35N?CM, the 4h's later ISQ was 82.37±2.05, and no statistic difference with the inserting ISQ(82.16±2.46)(P>0.05); and the 24h's later ISQ was 80.16±2.69, and statistically lower than the inserting ISQ(P<0.05). (4)When the loading force was 25N, the ISQs of pre-loading, 1800-loading and 3600-loading were respectively 80.42±2.82,70.21±6.40 and 66.63±5.93, and only the 3600 time's was statistically lower(P<0.05); while when the force was 50N, the according ISQs were respectively 80.42±2.82,70.21±6.40 and 66.63±5.93, and both were statistically lower(P<0.05),but there was no statistical difference between the 1800 and 3600 time loading(P>0.05). (5)Vitro loading on the implants which were inserted into bi-cortical position: when the force was 25N, the ISQs of pre-loading, 1800-loading and 3600-loading were respectively 81.17±3.0,78.46±2.28 and 70.00±5.08; when the force was 50N, the according ISQs were respectively 81.33±2.20,78.20±2.25 and 67.79±6.30. And at both the 25N and 50N force, only the ISQs of 3600-loading were statistically lower than pre-loading(P<0.05).Conclusion:①Different preparation of implant holes could reflect that different inserting torques were contributed to the compression extent when inserting implants, and further more, influence implant primary stability.②The ISQ seemed no change in short period when using lower ITV, seemed went up when using mediate ITV, and would at last go down when higher ITV were applied. This in another aspect demonstrated that the proper ITV was 25-35N?CM.③Immediate loading absolutely damaged implant primary stability due to its magnitude and frequency, and Implant inserted into lateral-cortical bone position could resist the impact by immediate loading. |
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