(PR01) Guided Endodontic Access for the Endodontic Retreatment of Maxillary Molars Restored with All-ceramic Crowns

This ex vivo study investigated the use of static guided access for the endodontic retreatment of maxillary molars restored with all-ceramic crowns. Impact on operating time, ability to locate a missed canal, and fracture strength of the crown were assessed. 30 extracted maxillary molars presenting with four separate canals were matched to create three standardized groups (n=10). Endodontic treatment was performed in all canals except MB2. Teeth were restored with crowns (e.max CAD, Ivoclar-Vivadent). 3-dimensional radiographic and intraoral optical scans were taken to create the static guides using Sicat software (Sicat, Bonn, Germany). Two groups were retreated using either traditional access cavity (TAC) or guided access cavity (GAC), and one group was used as control (intact crown). After endodontic retreatment, samples of GAC and TAC groups were restored with composite. All samples were subjected to occlusal force until fracture using a universal testing machine. Statistical analysis was performed with significance set at 5%. The mean time to access was 480.4s (±159) for GAC and 533.1s (±159) for TAC group (p>0.05). MB2 was located in all retreated samples. Fracture resistance was significantly higher for the control group (p < 0.05), and there was no statistically significant difference in the fracture load between GAC and TAC. Guided access was able to consistently locate a missed canal in teeth restored with all-ceramic crowns, but operating time was similar to traditional endodontic access. Intact crowns presented higher fracture strength compared to crowns accessed for retreatment, regardless of the type of endodontic access.