Method: Teeth free from caries, morphological defects and previous restorations were treated with three prototypes of varying viscosity of a nano-filled resin sealant (n=24; GC Corporation, Tokyo, Japan). A circular outline was drawn on the smooth surfaces, mesial and distal or labial and lingual, of each tooth and one of three materials (resin based: A, B, C) were applied by 8 operators using either a brush (n=68) or micro-brush (n=69). Baseline digital photographs were taken to assess the accuracy of application. The samples were then exposed to a dye treatment using 1.5% Procion Orange-14 dye pre and post thermocycling. Photographs were taken to assess microleakage pre and post thermocycling (8500 cycles in 3 water baths at 5±2°C, 22±2°C and 55±2°C with a dwell time of 30 seconds in each bath). The three resins were analysed for accuracy of application and microleakage using the image analysis functions of Photoshop CS5 (Adobe Systems Inc., California, USA) and statistical analysis (weight ANOVA, Feasible Generalized Least Squares) using Minitab 16 (Minitab Inc, State College, PA, USA).
Result: Operator handling variables were strongly associated with inaccurate application (p=0.000) and microleakage pre (p=0.000) and post thermocycling (p=0.021). The interactions between application method and material was significant to the seal of the material as indicated by the penetration of dye prior to thermocycling (p=0.034).
Conclusion: The results suggest that the placement of a smooth surface resin sealant is operator dependent and material properties contribute to the quality of the final seal.