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What does current studies indicate about the response of the pulp to composite resin?

Cytotoxicity studies suggest that composite resin which has been polymerised as far as possible probably causes minimum pulpal irritation. However, incompletely cured resin is a potential hazard. HEMA is regarded as an essential component of most of the light-activated composite resins; this is strongly hydrophilic and strongly allergenic. Even when fully light activated, not all HEMA will be bound, and some will he released with the possibility of an allergic response. It has been shown that HEMA is able to traverse dentine tubules and appear in the pulp tissue and there have been reports of allergic responses.