Microleakage is the term used for the passing of fluids, microorganisms or ions between the restoration and the adjacent preparation walls. Microleakage occurs around all restorations currently used in restorative dentistry, including those that are adhesively bonded to enamel and dentine. Such leakage provides a path for the ingress of bacteria and their products around restorations and has been implicated in a variety of clinical conditions, including marginal discoloration, pulpal irritation and subsequent necrosis, postoperative sensitivity, recurrent caries and eventual failure of restorations15,16.
The methods used to treat the preparation walls before restoration placement have changed over the years. This is thought to be a response to better understanding of the cause of pulpal damage, Brannstrom's hydrodynamic theory of pulpal pain17,18 and the development of new dental materials.
Traditional dental teaching advocated the generous use of bases and liners under restorations (especially amalgam) to limit postoperative sensitivity and to act as a thermal insulator. It was originally thought that the primary cause of pulpal inflammation was related to the direct cytotoxic effect of the dental restorative material. However, this has been shown to be a mild and transitory effect18.
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