Dynamic versus static bond-strength testing of adhesive interfaces.

ABSTRACT

UNLABELLED A static bond-strength test is often regarded as clinically less relevant, since such abrupt loading of the adhesive-tooth bond clinically never occurs. Therefore, dynamic fatigue testing is often claimed to better predict the clinical effectiveness of adhesives. OBJECTIVES: To measure the micro-tensile fatigue resistance (µTFR) of adhesives bonded to dentin, and to compare their µTFR to their micro-tensile bond strength (µTBS). METHODS: The bonding effectiveness (including fracture analysis) of three adhesives (OptiBond FL, Kerr 3-step etch-and-rinse adhesive or 3-E&Ra; Clearfil SE, Kuraray 2-step self-etch adhesive or 2-SEa; G-Bond, GC 1-step self-etch adhesive or 1-SEa) was measured by means of both a dynamic µTFR and a static µTBS approach. Preparation and test set-up of the micro-specimens were identical for both tests. In fatigue, specimens were tested with a wide range of selected loads at 2Hz and at 10Hz until failure, or until 10(4) cycles were reached. At 2Hz, the µTFR was also measured after 3-month water storage. The µTFR was determined using a logistic regression model. Two-way ANOVA and Tukey HSD multiple comparisons test were used to determine statistical differences in µTBS. RESULTS: The 1-SEa recorded significantly lower values in µTFR at 10Hz and in µTBS than the 2-SEa and 3-E&Ra. The 1-SEa and the 2-SEa performed significantly lower in µTFR than the 3-E&Ra, when tested at 2Hz after 3-month water storage. Fatigue testing at 2Hz after 1-week water storage did not reveal any differences in µTFR between the three adhesives. SIGNIFICANCE: The 3-E&Ra performed best in terms of bonding effectiveness, irrespective of the experimental condition or test used. The µTBS test proved once more to be a reliable laboratory test in ranking contemporary adhesives on their bonding effectiveness.