Implant-Abutment Fit Measured With Micro CT Versus Optical Microscopy

Endosseous titanium implant treatment is a well documented treatment modality in dentistry today. Replacement of single teeth with implants has become more popular and relies heavily on a stable implant-abutment connection. The interface between implant and abutment has traditionally been defined by cross-sectional analysis techniques. Recently, a new laboratory based scanner using cone beam computed tomography has become available. OBJECTIVES: This study was undertaken to determine the variability of both this new CT technique and cross-sectional analysis. METHODS: Four Straumann synOcta standard plus 10mm implants and four Straumann Meso abutments were connected and torqued to 35 N-cm. All specimens were scanned using a Skyscan model 1172 micro CT scanner at 2 micron resolution. The same specimens were the embedded in Buehler Sample-Kwik autopolymerizing resin, sectioned, and polished to the same level. The specimens were photographed on a Nikon Epiphot200 optical microscope with an Olympus 5060 digital camera, and measurements were obtained using UTSAHSC ImageTool 3.0 software and Adobe Illustrator software. RESULTS: Gap size data failed the Kolmogorov-Smirnov test for normality, so non-parametric tests were used. Optical microscopy estimated the gap size to be significantly larger than did micro CT (Mann-Whitney U: P<0.001). For both optical microscopy and micro CT, Illustrator software resulted in larger measured gap size than ImageTool software (Kruskal-Wallis ANOVA: P<0.001). Multiple scans of the same implant using micro CT yielded significantly different results (Kruskal-Wallis ANOVA: P=0.015). There was no difference in standard deviation between micro CT scans and optical microscope scans. CONCLUSION: These results indicate that there was not a significant difference in variability of gap size measurements made using laboratory micro CT scanning and cross-sectional optical microscopy. An interesting finding was the influence that different image analysis software and protocols had on the size of the gaps between implant and abutment surfaces. NIH-NIDCR Grant DE017991.