Fracture Resistance of CAD/CAM Lithium Disilicate of Endodontically Treated Mandibular Damaged Molars Based on Different Preparation Designs

Abstract

The aim of this study was to evaluate the fracture resistance of 2 different types of all-ceramic crown using immediate dentin sealing (IDS), obtained using a CAD/CAM system on molars with different preparations. Forty extracted lower molars were endodontically treated and divided into four groups (n = 10) according to the dental preparation. Group 1 (SP0) was prepared without filling the pulp chamber and crown-root junction was located at the cementoenamel junction (CEJ). Group 2 (SP1) was prepared without filling the pulp chamber and crown-root junction was located 1-mm above the CEJ. Groups 3 and 4 contained a flat preparation surface with no axial wall height. Group 3 (CP0) was made IDS with complete filling of the pulp chamber with composite resin and crown-root junction was located at the CEJ. Group 4 (CP1) was prepared with complete filling of the pulp chamber and crown-root junction was located 1-mm above the CEJ. All groups were restored with CAD/CAM lithium disilicate ceramic crowns. Specimens were subjected to the fracture test and statistically analyzed using analysis of variance (ANOVA). Fracture mode was determined using a stereoscopic microscope, classified as repairable or nonrepairable, and analyzed using Fischer’s exact test. Results indicated that there were no significant differences between the groups in terms of fracture resistance or fracture pattern (p >0.05). Fracture resistance was the lowest in the SP0 group, followed by the SP1 group (1634.38 N) of CP0 (1821.50 N), and it was the highest in the CP1 group. There was a predominance of nonrepairable fractures and there were no significant differences in the fracture resistance and fracture mode of CAD/CAM lithium disilicate molar all-ceramic crowns. Endodontically treated molars teeth might be restored with endocrowns or all-ceramic crowns on flat preparation; however tooth fracture failures that affect reliability of these types of restorations should be considered.

Effect of Inlays, Onlays and Endocrown Cavity Design Preparation on Fracture Resistance and Fracture Mode of Endodontically Treated Teeth: An In Vitro Study

“…Moreover, fracture localizations and modes have changed with different preparation design cavities. These results are in agreement with previous studies where the highest fracture resistance was recorded with endocrowns 16,25 …”

“…Other studies have shown that endocrowns are indicated in endodontically treated teeth and that they had a better fracture strength outcome when compared to conventional restorations. 11,25 However, Gré et al 30 reported similar value of fracture resistance with endocrowns and conventional crowns.…”

“…In a 3D finite element analysis study, Yoon et al 29 reported that the onlay cavity design protected the tooth structure more effectively than the inlay design for adhesively bonded leucite‐reinforced ceramic restorations. Other studies have shown that endocrowns are indicated in endodontically treated teeth and that they had a better fracture strength outcome when compared to conventional restorations 11,25 . However, Gré et al 30 reported similar value of fracture resistance with endocrowns and conventional crowns.…”

“…These results are in agreement with previous studies where the highest fracture resistance was recorded with endocrowns. 16,25 Fracture resistance of teeth with inlay cavity preparations depends on the remaining wall thickness limits that should be more than 2 mm. 1,26 Moreover, complete occlusal coverage exhibited the most favorable pattern of stress distribution in the tooth-restoration complex and large preparations require cuspal coverage to prevent possible fracture.…”

Fracture strength and failure load of CAD/CAM fabricated endocrowns performed with different designs

“…On the other hand, the group with 2mm of ferrule, showed lower rates of fracture resistance, and the worst results when assessing the fracture pattern of the pieces, since 60% of the samples had catastrophic fractures (Type I) corroborating with the findings from recent studies 8,21 . In contrast, some studies observed that the presence of ferrule increased fracture resistance 2,6 .…”