Purpose: This study compared the fatigue life of human maxillary premolars restored with
direct composites and indirect ceramic inlays in mesio-occlusodistal (MOD) cavities.
Materials and Methods: Ten human maxillary premolars were divided into two groups of
five and restored with (1) direct composite restorations, or (2) pressed ceramic restorations.
Standardized MOD cavities were prepared for both groups. Teeth in the direct composite
group were restored with Z250 composite and Single Bond adhesive, and those in the
ceramic group were restored with IPS Empress ceramic inlays. The ceramic inlays were
luted with Single Bond and RelyX ARC cement. Under the applied test load of 11.17 kg,
strain measurements were recorded from an electric resistance stain gauge bonded to the
buccal surface. These strains were recorded for the (1) intact tooth, (2) cavity preparation,
and (3) restored tooth. These strain measurements were used to calculate the relative tooth
compliance values for each tooth. The fatigue loading was applied until reinforcement loss
was registered by the strain gauge. Results: A one-way ANOVA showed no significant
compliance difference between the intact and restored tooth conditions, and no significant
difference in fatigue cycles to failure between the two groups. Conclusion: There were
both adhesive and cohesive failures in both restoration groups, indicating that the adhesive
joint is not the only weak link in these restorations. Int J Prosthodont 2003;16:64–69.