Presentation of gaps around endodontic access cavity restoration by phase contrast-enhanced micro-CT.

OBJECTIVE: To evaluate the feasibility of synchrotron-based phase-contrast (PC) µCT for visualization of the gaps and differentiation between the gaps, restorative, and endodontic materials at the tooth-restoration interface. MATERIALS AND METHODS: Standardized access cavities were prepared in human maxillary molars and subjected to materials, simulating endodontic treatment: (1) saline irrigation; (2) NaOCl and 17% EDTA irrigation; (3) same as group 2, followed by application of Ca(OH)2; and (4) same as group 2, followed by application of root canal sealer. The access cavities were cleaned and restored using an etch-and-rinse adhesive and a composite material in multilayering technique. The samples were thermocycled (1000 cycles, 5-55 °C). Synchrotron-based µCT imaging was performed obtaining absorption and PC µCT images before and after the immersion of the samples into 50% AgNO3. PC µCT images were compared to absorption µCT and conventional optical microscopy images. RESULTS: PC µCT of unstained samples enabled the best visualization of gaps and differentiation of restorative and endodontic materials, contaminating the cavity surface. PC µCT revealed that AgNO3 staining leads to an overestimation of gap size due to anterograde and retrograde AgNO3 infiltration into dentinal tubules and underestimation of large gaps due to lack of AgNO3 penetration. CONCLUSION: Synchrotron PC µCT imaging enables better visualization of gap and differentiation of materials at the tooth-restoration interface. µCT imaging with AgNO3 staining has shown certain over- and underestimations. Future research should be aimed at incorporating PC µCT imaging of unstained samples for the validation of results obtained with other methods. CLINICAL SIGNIFICANCE: Contamination of cavity walls with an endodontic sealer or Ca(OH)2 leads to increased gap formation at the tooth-restoration interface.