Bone-implant interface sections were examined under the optical microscope (Zeiss, Oberkpchen, Germany) using histological laboratory stains such as toluidine blue with Weigert haematoxylin (Merck, Kenilworth, NJ, USA) that allows the differentiation between osteoblasts and osteoclasts [24].

The images were processed and cross-sections were compared by means of the MIP-4 image analyser software (Digital Image Systems, SL, Barcelona) in order to quantify the bone fraction. The MIP-4 software is able to perform area and volume measurements through a computerized system connected to the optical microscope and histological lens. Area and length measurements on the images captured from the microscope were attained. All images were processed with ×10 magnification objective. The bone-to-implant contact (BIC) is calculated as the ratio of the length of the implant in contact to bone tissue and the implant perimeter, i.e. the percentage of the implant surface in contact with bone.

The quantitative results were processed with the statistical package Statgraphics plus 5.1. The significance of the differences between the groups was studied according to Student’s t test and the one-way ANOVA test (analysis of variance). p value was 0.05.