Comparison of Techniques to Determine Microleakage for Different Substrates

Objective:  To compare two techniques for determining microleakage and to compare microleakage of human and bovine teeth for adhesive bond systems.

Methods: 20 human teeth and 20 bovine teeth had cavities (3mmØX1.5mm) made on the buccal surface. The teeth were divided into 4 groups of 10 according to the substrate and adhesive (Clearfil SE Bond (Kuraray, Japan) or Scothbond 1 (3M, USA)). Composite (Wave-SDI, Australia) was applied in two increments, each cured for 30s. The specimens were stored in 100% relative humidity at 37°C for 24h and submitted to 1000 thermal cycles (5-55^oC 1min dwell), followed by immersion in aqueous rhodamine 0.6% for 48h. They were rinsed and sectioned at the centre of the restoration. Microleakage was measured and a score was allocated using the scale: 0–none, 1–up to enamel junction, 2–up to pulp wall, 3-in pulp wall, 4–beneath pulp wall. Penetration was submitted to ANOVA and Tukey test (5%) and the scores were submitted to a Kruskal-Wallis and Dunn's multiple comparison test (5%).

Results: Means of penetration in percentage (SD) and median of scores are showed:

When bovine teeth were used, Scothbond showed statistically higher mean penetration than Clearfil. When human teeth were used no difference was found. When scores were analyzed, Scothbond showed no difference to Clearfil, however Clearfil showed statistically less infiltration in bovine teeth than in human teeth when optical microscopy was used.

Conclusions: Confocal microscopy showed higher sensitivity for the stain and clearer leakage limits. Bovine teeth may be not suitable for adhesive microleakage tests.