Histomorphometric Study of Tissue Reaction to Mini Screws with Composite Coating

Stability of mini screws depends on mechanical factors in the primary phase and biological factors after osseointegration. The mini screws can transfer thermal shocks in the oral cavity to the bone marrow. It has been shown that level of osseointegration and inflammation are related to the failure of mini screws. The aim of this study was to compare the tissue response to mini screws with and without composite coating in the head.
In this in vitro, experimental study, mini screws with 1.4mm diameter and 6mm length were implanted in the maxilla of 12 male rabbits. One mini screw was implanted in each of the right and left quadrants of the maxilla. The right side mini screws had composite coatings on their head. The left side mini screws did not have such coatings. In the next three months, cold (1C) and warm water (40C) were injected into their mouth, 10 times daily. After three months, the rabbits were sacrificed and paraffinized tissue blocks were prepared. The tissue reaction was examined under light microscopy. The paired t-test and Wilcoxon Signed Rank test were used for statistical analysis.
The mean rate of osseointegration of mini screws with and without composite coatings was 32.1±5.3 and 20.4±3.43, respectively. The rate of osseointegration was significantly higher for mini screws with composite coatings than mini screws without them (P>0.0001). In both groups, the newly formed bone was woven and no inflammatory reaction was noted.
The rate of osseointegration of mini screws with composite coatings in the head was higher than that of miniscrews without them.