Bonding of resin to dentin. Interactions between materials, substrate and operators

Abstract: Objectives: The general aim of this thesis was to identify and study factors that affect bonding between resin and dentin, including operator variability. Materials and methods: Bonding sites were generated in vivo and in vitro and compared using SEM. The effects of experimental water- or acetone-based primers on shear bond strength to dentin were studied in vitro. Fourier transform infrared spectroscopy was used to establish any detrimental effects from water on polymerization by determining the degree of conversion of thin films of resin. The interaction between phosphoric acid and dentin was analyzed by measuring calcium leaching by use of atomic absorption spectroscopy. Bond strength of composite resin was measured to dentin with various degrees of demineralization. Gap formation adjacent to composite restorations in standardized dentin cavities was studied in vitro by confocal microscopy. Results: A similar morphological appearance was found for bonding sites generated in vitro vs. in vivo. An acetone-based primer was more dependent on a moist bonding technique than was a water-based system. However, water might influence bonding by interfering with the polymerization of the resin. Calcium leaching from dentin can be predicted by use of a solubility phase diagram. No correlation could be established between calcium leaching and bond strength. Gap formation was more dependent on the operator than the choice of material. A simplified all-in-one adhesive showed less operator variability compared to more complex bonding systems. Conclusions: In vitro bond testing may well indicate the outcome of in vivo trials. The solvents used in bonding agents will influence the performance and, presumably, technique sensitivity. Water rinse time after etching might be a more important consideration than etch time. In spite of the relative importance of the results presented above, the outcome of the multi-operator trial could not be predicted.