Fatigue resistance and failure mode of CAD/cam indirect restorations: effect of thickness, prosthetic material and cusp coverage

Author(s)

Mayara dos Santos Noronha

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2022-02-22

Examining board members

Marcelo Giannini; Lourenço Correr Sobrinho; Paulo Henrique dos Santos; Marcia Socorro da Costa Borba; Renata Marques de Melo Marinho

• Advisor: Marcelo Giannini

Abstract

The aim of this thesis was to evaluate the influence of thickness, type of prosthetic material and cusp protection on fatigue strength and failure mode of CAD/CAM full crowns or partial restorations. Three accelerated fatigue studies were performed with 225 upper molars (n=15). For the study 1 (E1), thin (0.5-0.7 mm) and thick (1.5-1.7 mm) full crowns (FC) of three CAD/CAM materials were tested: lithium disilicate (LiDi, e.max CAD), zirconia-reinforced lithium silicate (LiSi-Suprinity) and polymer infiltrated ceramic network (PICN, Enamic). In study 2 (E2), endodontically treated teeth (ETT) were restored only with direct composite resin (CR, Herculite XVR), Control (C), or with CR associated with thin (0.4-0.6 mm) and thick partial restorations (1.4 mm-1.6 mm) using CAD/CAM materials of lithium silicate with zirconia (LS, Celtra Duo) and resin composite (RC, Cerasmart). For study 3 (E3), a simulation of lingual cusp fracture was performed, in ETT, which were later restored with or without buccal cusp protection, using hybrid ceramic CAD/CAM materials (PICN, Enamic) and composite resin (CORE, Cerasmart 270). In E1, luting was done with dual cement (Panavia V5), while in E2 and E3, by thermo-modified resin technique with composite resins (Herculite and Z100), respectively. Sample were storage 1 year for E1 and at least 24 hours for E2 and E3. After luting and storage, the samples were submitted to the fatigue test (Acumen3, MTS Systems), with 5Hz of frequency, load between 200N and 1800N and maximum number of cycles of 115000 (E1) and 131000 (E2 and E3). Fatigue resistance was analyzed through the survival rate by the Kaplan Meier survival curve and groups were compared by post-hoc tests with a 95% significance level. All samples were analyzed and categorized into failure mode. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were performed at E2 and E3, to analyze the structure and chemical composition of the materials tested. LiDi FC showed higher fatigue strength (P>0.001). Thickness did not affect the fatigue strength of partial restorations on ETT (P>0.001), and thick LS showed higher strength than CR and C (P<0.05). Thin LS, CR and C did not differ from each other (P>0.05). Cusp protection affected PICN (P<0.05). No differences were found in PICN and CORE materials, with and without cusp protection (P>0.05). FC Thick LiDi (87%), thick LiSi partial (60%) and Cusp- protected PICN (40%) showed the largest samples that survived the entire test. Thick LiDi (13%) FC, partial Thin CR (20%) and CORE with cusp coverage (33%) had more repairable failures. Thin LiDi FC (73%), partial thick CR (80%) and CORE without cusp coverage (60%) showed more catastrophic failures. Fatigue strength was affected by thickness in FC with LiDi and cusp coverage of PICN. Differences were found in the type of material in all studies (AU)

• FAPESP's process: 17/04257-7 - Effect of thickness and type of prosthetic material on load to failure and fatigue resistance of full crowns and overlays made with CAD/CAM system
• Grantee: Mayara dos Santos Noronha
• Support Opportunities: Scholarships in Brazil - Doctorate