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Background: A new bone preparation technique, using smooth tamps for bone compaction, has increased crucial initial implant stability. However, preparing the femur with bulky smooth tamps, which from size to size increases the same amount in anterior to posterior as in lateral to medial dimensions, has increased the risk of a femoral fracture. This study examined whether compaction also involved an increased femoral fracture risk when using newly developed smooth tamps with a slim anterior to posterior dimension., Methods: One femur in each pair of 10 cadaver femurs was prepared by the compaction technique using cylindrical reamers and smooth tamps. The contralateral femur was conventionally prepared with conical reamers and toothed rasps. The tamps and rasps differed in design as a proximal lateral tip was only present on the smooth tamps. Using a standardized test protocol, the instruments were driven into the femoral canal in controlled manner by a drop tower., Findings: At maximum test conditions, five of 10 femurs in the compaction group had fractured, as compared with no fractures in the rasping group. All fractures were longitudinal fissures in the greater trochanter, and these fissures were associated with the extended proximal lateral tip of the tamps., Interpretation: Since the lateral fractures in the compaction group were associated with the extended proximal lateral tip of the tamps, it seems that fracture rates are influenced by instrumentation design. Therefore adequate pre-clinical evaluation is warranted prior to the introduction of new implantation techniques.

A new surgical technique, compaction, has been shown to improve implant fixation. It has been speculated that the enhanced implant fixation with compaction could be due to a spring-back effect of compacted bone. However, such an effect has yet to be shown. Therefore we investigated in a canine model whether implant cavities prepared with compaction had spring back. Before killing the animals, we used one of two surgical techniques to make implant cavities of identical dimensions in both lateral femoral condyles of 7 dogs. One side had the implant cavity prepared with compaction, the other side with drilling. The cavities were left empty in vivo for 10 minutes before the dogs were killed. Postoperative micro-CT scanning showed that the diameters of the compacted cavities were significantly smaller than those of the drilled cavities, although they had had identical dimensions initially. Thus we found a spring-back effect of compacted bone, which may be important for increasing implant fixation by reducing initial gaps between the implant and bone.

The aim of this study was to compare diagnostic accuracy of a caries detection program with that of human observers. A total of 190 extracted teeth were radiographed with two Trophy RVG (RadioVisioGraphy) digital sensor systems. Four observers scored the approximal surfaces in all images on a disease severity scale. Each observer thereafter used the Logicon Caries Detector (LCD) program to analyse the surfaces in the digital images and recorded their outcome. To determine the true absence or presence of caries, histological validation was used. Sensitivities, specificities, positive and negative predictive values were calculated and differences between the diagnostic methods tested. Specificities for the outcome with the LCD were significantly lower for three observers than when they themselves assessed the RVG images and, correspondingly, the positive predictive values were lower for the LCD outcome for three of the observers. Sensitivity was also lower for two observers on the diagnostic threshold caries in dentine. It was concluded that the automated caries detection program is less accurate than human observers in detecting approximal caries lesions.