Introduction: Inlay-retained fixed partial dentures (IRFPDs) have been proposed as a more conservative method for replacing missing dentition instead of the more destructive full crown preparation. Various studies have been conducted on the flexural strength of such restorations; however, there is a lack of evidence on their marginal integrity.
Objectives: Evaluating the marginal integrity of three IRFPD designs fabricated using monolithic translucent zirconia.
Materials and methods: Thirty IRFPDs were fabricated using a translucent monolithic zirconia (Katana STML) and divided randomly into 3 groups according to the cavity design. Group 1 received an inlay cavity preparation including a proximal box and a 2 mm deep occlusal extension, Group 2 received an inlay cavity preparation including a proximal box and a 1.5 mm deep occlusal extension, and Group 3 received only a proximal box cavity preparation without an occlusal extension. The restorations were fabricated and cemented using a dual cure resin cement (Panavia V5 system) and subjected to an equivalent of 5 years of ageing. A dye penetration test was performed on the specimens, and the values of marginal penetration were analyzed under a stereomicroscope.
Results:During the whole 5-year ageing process, no specimens showed signs of cracking, fracture or loss of retention in any or the restorations. There was a significant difference between the marginal leakages values obtained in the 3 groups of the study (H=10.208, p < 0.05). Comparing the groups of the study showed significant difference in marginal leakage between Group 1 and Group 3 (p < 0.05).
Conclusions: The margins of inlay-retained fixed partial dentures performed well after ageing with recommended bonding protocols for zirconia. Inlay cavity design including a proximal box and an occlusal extension exhibited better marginal stability than proximal box without any occlusal extension