Radiographic and histological density of peri-implant bone in animal study

Abstract

Radiographic density analysis of jaw bone by adding an aluminum step wedge has shown high precision, accuracy and diagnostic specificity in previous studies. Objectives: To determine aluminum equivalent density(AED) values of peri-implant bone at implant neck, threads and apical regions, identify bone density changes after healing and check if AED values can identify absence of osseointegration, using histological images as gold-standard. Methods: Ten Göttingen minipigs received 40 implants (20 commercially pure titanium; 20 Osseospeed 3.5S, Astra Techs) and were sacrificed 3 months later. Standardized intra-oral radiographs were taken at implant placement (baseline) and after 3 months. Custom-made and DBSwin software (DürrDental) were used to measure bone density(AED) and marginal bone level, respectively. For histomorphometrical analyses, implant sections were stained to visualize mineralized and non-mineralized bone and measure bone defect depth and peri-implant bone volume. Statistical analyses used linear regression analysis, Kruskal-Wallis, Wilcoxon and Pearson correlation tests at significance level of 0.05. Results: Bone around implant threads and apical region showed a significantly higher bone density than around implant neck(table1-2). No significant changes of AED were found after 3 months, despite the higher values compared to baseline(table3-4). AED was significantly, but weakly, correlated to bone defect depth(table5) and bone loss(table6), however no correlation was found with peri-implant bone volume(r=0.21; p=0.18). AED values lower than 5mmAleq at baseline showed bone loss greater than 2.0mm after 3 months healing(table7/fig.3). Conclusions: AED is a promising diagnostic tool to predict bone tissue response to titanium implants. An increased bone loss (>2mm) seem more likely to occur at low density bones(<5mmAleq). Distinct bone densities are found around implant neck, threads and apical regions. Yet, for a more precise analysis of osseointegration, further studies are needed to better diagnose the absence of bone formation around implant by means of radiological images.