Impact of conservative and traditional endodontic accesses on the strength of maxillary zirconia crowns
Year: 2025
Type: article
Abstract: PURPOSE: Performing endodontic procedures on existing crowns is common when replacing the crown is not feasible. Traditional triangular access (TTA) is standard for maxillary molars, but more conservative designs are reported in the literature. However, research comparing the fracture resistance of maxillary molar zirconia crowns using traditional and novel endodontic access sealed with composite resin remains limited. The purpose of this in vitro study was to evaluate the fracture resistance of maxillary molar zirconia crowns with various endodontic cavity designs: traditional triangular access (TTA), conservative triangular access (CTA), and conservative circular access (CCA). A control group with no endodontic access (NEA) was also included. MATERIALS AND METHODS: A maxillary right first molar typodont tooth was prepared for a full all-ceramic crown. The preparation was scanned, and 48 dies were 3D-printed based on the tooth preparation. A total of 48 zirconia crowns were fabricated (n = 12 per group) and divided into four groups according to the endodontic access cavity design: TTA, CTA, CCA, and a control group without an endodontic cavity. To ensure consistency, all restorations were designed and fabricated using a digital workflow. Endodontic access was created using a specialized bur kit and sealed using a repair kit for damaged ceramic restorations along with resin composite. The restorations were cemented, and all samples underwent artificial aging with 10,000 thermal cycles between 5°C and 55°C, with a dwell time of 30 s. The samples were then loaded to failure using a universal testing machine. The maximum load to fracture was analyzed using a one-way ANOVA and post hoc Tukey honestly significant difference (HSD) test (α = 0.001). Additionally, the fracture patterns of the specimens were evaluated descriptively using a scanning electron microscope. RESULTS: The mean fracture resistance of maxillary molar zirconia crowns varied significantly by endodontic access type. CCA showed the highest resistance (3677 N) among access groups, followed by CTA (3385 N) and TTA (2927 N). The control group NEA (3834 N) exhibited the highest overall resistance, exceeding all access groups. CONCLUSIONS: Conservative access designs increased the fracture resistance of zirconia crowns compared with traditional access, with circular access showing the highest strength. However, all access preparations reduced resistance relative to crowns without endodontic access.
Source: Journal of Prosthodontics
DOI: 10.1111/jopr.70082
Language: English
Subfield: Orthodontics
Field: Dentistry
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W4417523976