Marginal integrity of monolithic zirconia crowns in endodontically treated premolars: effects of finish line position and post and core types incorporating deep marginal elevation and crown lengthening procedures

BACKGROUND: Sufficient information is not available regarding the selection of ideal post and core types or the preferred method to access the subgingival margin to achieve optimal marginal integrity in the reconstruction of teeth with deep cervical lesions. This study aimed to evaluate how the position of the finish line and different post and core types, combined with deep marginal elevation (DME) and crown lengthening (CL) procedures, affect the marginal integrity of monolithic zirconia crowns in endodontically treated premolars. METHODS: In the present laboratory experiment, 60 endodontically treated maxillary first premolars were assigned to six groups (n = 10): composite core supported by prefabricated fiber post (FP/CC) with DME (FP/CC-DME), composite core reinforced with polyethylene fiber (PEF/CC) with DME (PEF/CC-DME), cast post and core (CPC) with DME (CPC-DME), FP/CC-CL, PEF/CC-CL, and CPC-CL. Marginal integrity was assessed at the TheraCem-core, core-tooth, TheraCem-dentin, and TheraCem-enamel interfaces. Data were analyzed statistically (α = 0.05). RESULTS: In the DME approach, the lowest marginal integrity was noted at the TheraCem-core and core-tooth interfaces in the CPC group, followed by FP/CC and PEF/CC (P < 0.05). In the CL approach, there was no significant variation among the groups (P > 0.05). With FP/CC, TheraCem-core, core-tooth, and TheraCem-dentin interfaces showed comparable marginal integrity (P > 0.05). With PEF/CC, the least marginal integrity was recorded at the TheraCem-dentin interface, followed by the TheraCem-core and core-tooth interfaces. With CPC, the TheraCem-core and core-tooth interfaces showed lower marginal integrity than dentin (P < 0.05). CONCLUSIONS: The type of post and core significantly affected the marginal integrity in the DME approach (PEF/CC > FP/CC > CPC) but not in the CL approach. DME, compared with CL, increased the marginal integrity with PEF/CC, decreased the marginal integrity with CPC, and did not affect the marginal integrity with FP/CC.