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Objectives: To measure in vivo impact of dense bone overheating on implant osseointegration and peri-implant bone resorption comparing different bur irrigation methods vs. no irrigation., Materials and Methods: Twenty TI-bone implants were inserted in the inferior edge of mandibles of sheep. Different cooling procedures were used in each group: no irrigation (group A), only internal bur irrigation (group B), both internal and external irrigation (group C), and external irrigation (group D). The histomorphometric parameters calculated for each implant were as follows: %cortical bone-implant contact (%CBIC) and %cortical bone volume (%CBV). Friedman's test was applied to test the statistical differences., Results: In group A, we found a huge resorption of cortical bone with %CBIC and %CBV values extremely low. Groups B and C showed mean %CBIC and %BV values higher than other groups The mean %CBV value was significantly different when comparing group B and group C vs. group A (P < 0.05). Significant differences in %CBIC were found also between group C and group A (P < 0.05)., Conclusions: Thermal injury, due to insufficient irrigation, of hard bone caused massive resorption of the cortical bone and implant failure. Drilling procedures on hard bone need an adequate cooling supply because the bone matrix overheating may induce complete resorption of dense bone around implants. Internal-external irrigation and only internal irrigation showed to be more efficient than other types of cooling methods in preventing bone resorption around implants., (© 2013 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.)

Objectives: Protocols of immediate loading have been reported in several studies. It has also been demonstrated that the cause of failure of immediate loaded implants is due to the micromotion on the bone-implant interface induced by immediate loading. There should be a minimum gap between the implant and the peri-implant bone, without micromotions occurring above a definite threshold risk as they induce bone resorption and fibrosis around the implant. Measurement of the torque necessary to insert an implant in the bone is a parameter for measuring initial stability. The higher the implant insertion torque, the higher the initial stability attained. The aim of this study was to evaluate in vitro the correlation between the micromotion of cylindric screw implants ad modum Branemark and the insertion torque in bone of different densities., Material and Methods: The test was carried out on 2 × 2 cm samples of fresh bovine bone of three different densities: hard (H), medium (M) and soft (S). One hundred and fifty hexa implants ad modum Branemark were used, 3.75 mm in diameter and 9 mm long. To screw in the implants, a customized manual key was used, controlled digitally to evaluate the peak insertion torques. Ten implants were prepared for each torque (20, 35, 45, 70 and 100 N/cm). The bone sample was then fixed on a loading device, which allowed evaluating the micromotion. On each sample, we applied a 25 N horizontal force., Results: The results indicate that the peak insertion torque and the implant micromotion are statistically correlated, and statistically significant differences in H and M bone were found compared with S bone. In S bone, we noted a micromotion significantly higher than the risk threshold, and it was not possible to reach peak insertion torque above 35 N/cm. In H and M bone, the micromotion is below the threshold of all insertion torques., Conclusions: Increasing the peak insertion torque, we can reduce the extent of the micromotion between the implant and the bone when submitted to lateral forces in vitro. In soft bone, the micromotion was always high; hence, immediate loading of implants in low-density bone should be evaluated with care., (© 2010 John Wiley & Sons A/S.)

Objectives: Measuring peak insertion torque in relation to different bone densities, the present study seeks to determine whether micromotion at the interface is related to primary stability achieved by increasing insertion torque., Material and Methods: A total of 120 Ti-Bone implants were placed in fresh bovine bone samples representing three density categories: hard, normal and soft (HNS). Five groups of peak insertion torque (20, 35, 45, 70 and 100 N/cm) were evaluated in the three bone density categories noted. Customized electronic equipment connected to a PC was used to register the peak and other insertion torque data. A loading device, consisting of a digital force gauge and a digital micrometer, was used to measure the micromovements of the implant during the application of 20, 25 and 30 N lateral forces. The data were analyzed for statistical significance by ANOVA and Spearman's rank correlation coefficient tests., Results: A statistically significant difference between implant micromobility placed with different levels of torque and in different bone densities was demonstrated by ANOVA. Spearman's rank correlation coefficient showed a high dependency between the peak insertion torque and the observed micromovement. Particularly, in soft bone, it was not possible to achieve more than 35 N/cm of peak insertion torque., Conclusions: Results showed that increasing the peak insertion torque reduces the level of implant micromotion. In addition, micromotion in soft bone was found to be consistently high, which could lead to the failure of osseointegration. Thus, immediate functional loading of implants in soft bone should be considered with caution.