Long term durability of composite resin restorations in vivo and improvement

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In order to evaluate the long term durability of composite resin restorations, cervical cavities were prepared Various bonding agents were applied according to the manufacturers' instructions. Clinical findings of these fillings were periodically observed. In order to observe the marginal adaptation, impressions of these restorations were taken and precision replicas were made. These replicas were observed by scanning electron microscope. In many cases, marginal adaptation of early stage was good. Marginal steps were observed after 18 months. The width of steps was extended with time. When the bonding layer was exposed at the margin, abrasion progressed from the exposed bonding layer and the marginal fracture of resin materials occurred. Enamel etching effectively improved the adaptation to enamel.