IN-VITRO CYTOTOXICITY OF DENTAL ADHESIVE SYSTEMS UNDER SIMULATED PULPAL PRESSURE

Objectives. Most of the devices used to evaluate the cytotoxicity of r esin-based composites in vitro use a dentin barrier test. However, it is difficult to obtain the number of freshly extracted teeth, all on t he same day, that is necessary for powerful statistical analysis. Toot h cryopreservation provides a way to build up a supply of teeth. This in vitro study compared cryopreserved teeth and freshly extracted teet h in an evaluation of the cytotoxicity of resin-based composites. In a ddition, this study also evaluated the effects of pulsatile pressure a nd the importance of dentin permeability on the cytotoxic response to bonding resins. Methods. Forty freshly extracted and forty cryopreserv ed third molars were used. A standardized Class I cavity was prepared within the dentin. The hydraulic conductance of each tooth was recorde d. The cavities were filled either with Scotchbond Multi-Purpose Plus and Z 100 (3M Dental Products) or with Optibond and Herculite (Kerr). A plexiglas device was designed to permit 24 h long contact between cu lture medium and the roof of the pulp chamber while a pulsatile pulpal pressure was simulated. The viability of L 929 cells cultured with a control medium and evaluated by an MTT assay was compared to that of L 929 cells cultured with medium which remained for 24 h in contact wit h the pulp chamber of restored teeth. A three-way ANOVA was used to co mpare the cytotoxicity among the different groups. A simple least-squa res linear regression was used to seek a relationship between the hydr aulic conductance of dentin and the cytotoxicity of composite restorat ive materials. Results. No significant differences in cytotoxicity wer e found between the freshly extracted teeth and the cryopreserved teet h (p = 0.53). The cytotoxicity of the resin adhesives was statisticall y higher when a pulsatile pulpal pressure was simulated (p = 0.04). A significant relationship was found between the hydraulic conductance o f dentin and the cytotoxicity of resin-based composites (p = 0.02). Si gnificance. Cryopreserved teeth can be used for in vitro evaluation of the cytotoxicity of resin adhesives. Pulsatile pulpal pressure simula tions increased the in vitro cytotoxicity of the tested materials.