The effect of ferrule heights on fracture resistance of anterior CAD/CAM endocrowns

Purpose: There is limited evidence regarding the effect of ferrule height on the fracture resistance and failure modes of anterior endocrowns. To address this gap, the present study aimed to evaluate how different ferrule heights influence the fracture resistance and failure modes of anterior endocrown restorations. Materials and Methods: Sixty extracted maxillary incisors were collected (n=60) and divided into five samples (n=12): endocrowns with 0mm ferrule height (Group Z), 1.00 mm ferrule height (Group O), 2.00 mm ferrule height (Group T), a conventional post and core followed by a lithium disilicate crown, positive control (Group P), and untreated tooth, negative control (Group N). The samples were subjected to root canal treatment followed by the placement of smart dentin replacement resin. Then the teeth were embedded in epoxy resin blocks. The preparation of the samples with different ferrule heights and the pulp chamber depth of 4.00 mm were prepared. Lithium disilicate restorations were fabricated using a CAD/CAM CEREC system and cemented with a dual-cure resin adhesive. All samples were subjected to static loading test applied at 45° angle. Fracture resistance was determined using a universal testing machine; median failure loads (N) and the failure modes were assessed by descriptive analysis and categorized under restorable and non-restorable groups. The data was recorded in SPSS and was analyzed using Kruskal-Wallis test, followed by a post hoc, Pairwise Analysis. The failure modes of the samples were analyzed statistically with Chi-Square test. The statistically significant difference was set at p<0.05. Results: There is a statistically higher fracture resistance in Group Z (1701.82 N), followed by Group T (1387.06 N), Group O (1327.3 N), Group P (750.58 N) and the lowest was in Group N (402.97 N). Anterior endocrowns were associated with higher non-restorable failures in comparison to conventional crowns. Conclusion: Anterior endocrowns featuring a 0 mm ferrule preparations demonstrated the highest fracture resistance. However, majority of the samples exhibited an increased risk for non-restorable failures. Further recommendation is to conduct long-term clinical study to evaluate the success/survival rate of anterior endocrowns.