Detection of the initial gap at different implant-abutment connections.

STATEMENT OF PROBLEM: The seal at the implant-abutment connection (IAC) is crucial for ensuring implant-prosthetic function and reducing the risk of peri-implant diseases. An accurate determination of the first IAC gap under realistic dynamic-loading conditions is needed to investigate current and future IAC designs. PURPOSE: The purpose of this in vitro study was to use a novel method of determining the load and probability of occurrence of the elastic first IAC gap that overcomes most of the limitations of the representative IACs currently available. MATERIAL AND METHODS: Three flat-straight and 4 conical-tapered connections with varying abutment cone angles with 8 specimens per configuration (n=8) were tested with an in situ loading experiment underwater by following the International Organization for Standardization (ISO) 14801 standard. Before load application, the IACs were filled with toluidine, and the screws tightened to 35 Ncm. Incremental loading of 20 N was applied over 1000 cycles until leakage was detected by a video recording macro-equipped camera. Differences between the means were determined by 1-way ANOVA (alpha=.05). The probability of gap occurrence was calculated from the data obtained based on the maximum occlusal force values reported in literature. RESULTS: The method allowed the detection of the first IAC gap in the elastic regime. Flat connections showed a linear relationship between connection diameter and the first gap load ranging from 140.0 +/-21.4 N (O3.0 mm) to 255.0 +/-31.6 N (O4.1 mm). On O3.5 mm connections, the gap at flat connections opened at 193.8 +/-22.0 N, while, at conical connections, the loads needed were significantly lower and the dispersion higher, irrespective of the angle between the abutment and the implant connection cones: 135.0 +/-80.5 N (0 degrees), 100.0 +/-54.5 N (0.4 degrees, P<.05), 77.5 +/-37.7 N (0.8 degrees, P<.05) and 82.5 +/-49.5 N (1.2 degrees, P<.05). Consequently, conical connections had a higher probability of gaps, particularly in the posterior zone, ranging from 8.2% to 29.0% of the reported mastication force. CONCLUSIONS: This innovative in situ leakage detection method enabled the identification of disparities in the masticatory load at which initial gaps occurred across various flat and conical IAC configurations.