To compare the clinical performance of Dyract, Spectrum-TPH and Dyract layered with Spectrum-TPH (sandwich) in Class II restorations of permanent dentitions.23 adult patients aged 25-62 were selected at random in a general dental practice. Each patient had 3 bicuspid teeth restored with Dyract, Spectrum-TPH and a "sandwiched" combination where Dyract was covered by the composite resin TPH. During the entire study, three patients were lost. Restorations were clinically evaluated using a modified Ryge/USPHS system.Over 36 months all three types of restorations performed well clinically. No post-operative sensitivity was reported by any patient indicating proper bonding and sealing. Only one Dyract/TPH sandwich restoration had to be replaced after 2.5 years due to root caries. The Dyract restorations exhibited significantly higher (P = 0.0039) occlusal wear than the TPH and the Dyract/TPH sandwiched restorations. The marginal integrity was also found to be significantly better (P = 0.001) for the TPH and Dyract/TPH restorations compared to Dyract alone, while no significant difference (P > 0.05) could be demonstrated between TPH and Dyract/TPH restorations. The low rate of failure in the three different restorative systems suggests that they are reliable restorative materials in permanent bicuspids over a 3-year period.