Restoration of severely damaged endodontically treated premolars: The influence of the endo-core length on marginal integrity and fatigue resistance of lithium disilicate CAD-CAM ceramic endocrowns

• Published in: Journal of dentistry Vol. 68; pp. 41 - 50
• Main Authors: Rocca, G.T., Daher, R., Saratti, C.M., Sedlacek, R., Suchy, T., Feilzer, A.J., Krejci, I.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.01.2018; Elsevier Limited
• Subjects: Adhesion; Adhesives; Bicuspid; Bond strength; CAD-CAM; CAM; Cement; Cementation; Ceramics; Compressive Strength; Computer aided manufacturing; Computer-Aided Design; Crowns; Dental crowns; Dental Marginal Adaptation; Dental Materials; Dental Porcelain - chemistry; Dental Prosthesis Design; Dental Restoration Failure; Dental Restoration, Permanent; Dental restorative materials; Dental Stress Analysis; Dentin; Dentistry; Enamel; Endo-core; Endocrown; Endodontically treated; Endodontics; Fatigue; Fatigue strength; Humans; Influence; Lithium; Lithium disilicate; Marginal integrity; Materials fatigue; Materials Testing; Odontology; Polymerization; Premolars; Restoration; Stress, Mechanical; Survival Analysis; Teeth; Tooth Cervix; Tooth, Nonvital; Treatment Outcome; Lithium disilicate; Endocrown; CAD-CAM; Fatigue; Endodontically treated; Endo-core; Marginal integrity
• ISSN: 0300-5712; 1879-176X
• DOI: 10.1016/j.jdent.2017.10.011

To explore fatigue limits of ceramic endocrowns for premolars. Forty-eight devitalized premolars were cut at the CEJ. They were restored with standardized CAD–CAM lithium disilicate reinforced ceramic restorations (IPS e.max CAD, Ivoclar-Vivadent) and divided into four Groups (n = 12): overlays (Group A, no endo-core, negative control), endocrowns with an endo-core of 2 mm (Group B), 4 mm (Group C) and crowns with post and core (Group D, positive control). All specimens were first submitted to thermo-mechanical cyclic loading (TCML)(1.7 Hz, 49 N, 600000 cycles, 1500 thermo-cycles). Margins were analysed before and after the loading. Survived specimens were then submitted to cyclic isometric stepwise loading (5 Hz, 200N to 1200N) until completion of 105000 cycles or failure. In case of fracture, fragments were analysed using SEM and failure mode was determined. Results of stepwise loading were statistically analysed by Kaplan–Meier life survival analysis and log rank test (p = 0.05). All the specimens survived the TCML test except four specimens of Group A (early restorations' debonding). No difference in percentages of closed margins was found between endocrowns (Groups B, C) and crowns (Group D). After the stepwise test, differences in survival within the groups were not statistically significant. Most of restorations experienced non-reparable fracture. Endocrowns with both 2-mm and 4-mm long endo-cores displayed outcomes after fatigue equivalent to classical crowns. Results of this study discourage the use of flat overlays with only adhesive retention. When restoring extremely destroyed devitalized premolars, adhesive strategies should be coupled to a macro-mechanical retention in the root.