DIFFERENCES IN IMPLANT STABILITY ASSOCIATED WITH VARIOUS METHODS OF PREPARATION OF THE IMPLANT BED: AN IN VITRO STUDY

Statement of problem. It is difficult to achieve the primary stability necessary for immediate loading in the posterior maxilla because of thin cortical bone, low density trabecular bone, and inadequate bone height due to the presence of the maxillary sinus. Purpose. The purpose of this study was to examine the primary stability of dental implants placed by using different methods of preparation for in vitro monocortical and bicortical models of the posterior maxilla. Material and methods. Sixty screw-shaped implants (4.0 x 10 mm) were inserted into solid rigid polyurethane blocks. The implants were divided into 6 groups (n=10) to test 2 variables: 1) location (monocortical or bicortical block) and 2) preparation method (standard preparation, underpreparation, or the osteotome technique). The insertion and removal torques were measured and resonance frequency analysis (RFA) was performed to determine the primary stability of each implant. Insertion and removal torque data were analyzed by 2-way ANOVA, followed by the post hoc Tukey HSD multiple comparison test. RFA data were analyzed by 2-way and 1-way ANOVAs and the Tukey HSD multiple comparison test (alpha=.05). The Pearson correlation analysis was also performed to examine correlations among the values. Results. The preparation method had a significant effect on insertion torque, RFA value, and removal torque; however location had a significant effect only on the removal torque (P<.001). There was a significant interaction between location and preparation method for RFA values (P=.045) and a significant difference in standard preparation method according to the location (P=.039); however, there was no significant difference in underpreparation (P=1.00) and osteotome technique (P=1.00). Statistically significant correlations were found between insertion torque and RFA values (r=0.529, P<.001), insertion torque and removal torque values (r=0.517, P<.001), and removal torque and RFA values (r=0.481, P<.001). Conclusions. Underpreparation and bicortical fixation significantly increased implant stability and the osteotome technique decreased implant stability in synthetic bone models that mimicked the posterior maxillary region. The primary stability values had statistically significant correlations to each other. (J Prosthet Dent 2012;107:366-372)