Atais Bacchi1, Aloisio Oro Spazzin2, Gabriel Rodrigues de Oliveira2, Carmem Pfeifer3, Paulo Francisco Cesar4. 1. Department of Biomaterials and Oral Biology, University of São Paulo -USP, São Paulo, Brazil; Department of Prosthodontics and Dental Materials, Meridional Faculty - IMED, Passo Fundo, Brazil. 2. Department of Prosthodontics and Dental Materials, Meridional Faculty - IMED, Passo Fundo, Brazil. 3. Department of Restorative Dentistry, Division of Biomaterials and Biomechanics, Oregon Health & Science University, Portland, OR, USA. Electronic address: pfeiferc@ohsu.edu. 4. Department of Biomaterials and Oral Biology, University of São Paulo -USP, São Paulo, Brazil.
Abstract
OBJECTIVES: The use of thio-urethane oligomers has been shown to significantly improve the mechanical properties of resin cements (RCs). The aim of this study was to use thio-urethane-modified RC to potentially reinforce the porcelain-RC structure and to improve the bond strength to zirconia and lithium disilicate. METHODS: Six oligomers were synthesized by combining thiols - pentaerythritol tetra-3-mercaptopropionate (PETMP, P) or trimethylol-tris-3-mercaptopropionate (TMP, T) - with di-functional isocyanates - 1,6-Hexanediol-diissocyante (HDDI) (aliphatic, AL) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (BDI) (aromatic, AR) or Dicyclohexylmethane 4,4'-Diisocyanate (HMDI) (cyclic, CC). Thio-urethanes (20 wt%) were added to a BisGMA/UDMA/TEGDMA organic matrix. Filler was introduced at 60 wt%. The microshear bond strength (μSBS), Weibull modulus (m), and failure pattern of RCs bonded to zirconia (ZR) and lithium disilicate (LD) ceramics was evaluated. Biaxial flexural test and fractographic analysis of porcelain discs bonded to RCs were also performed. The biaxial flexural strength (σbf) and m were calculated in the tensile surfaces of porcelain and RC structures (Z = 0 and Z = -t2, respectively). RESULTS: The μSBS was improved with RCs formulated with oligomers P_AL or T_AL bonded to LD and P_AL, P_AR or T_CC bonded to zirconia in comparison to controls. Mixed failures predominated in all groups. σbf had superior values at Z = 0 with RCs formulated with oligomers P_AL, P_AR, T_AL, or T_CC in comparison to control; σbf increased with all RCs composed by thio-urethanes at Z = -t2. Fractographic analysis revealed all fracture origins at Z = 0. CONCLUSION: The use of specific thio-urethane oligomers as components of RCs increased both the biaxial flexural strength of the porcelain-RC structure and the μSBS to LD and ZR. CLINICAL SIGNIFICANCE: The current investigation suggests that it is possible to reinforce the porcelain-RC pair and obtain higher bond strength to LD and ZR with RCs formulated with selected types of thio-urethane oligomers.
OBJECTIVES: The use of thio-urethane oligomers has been shown to significantly improve the mechanical properties of resin cements (RCs). The aim of this study was to use thio-urethane-modified RC to potentially reinforce the porcelain-RC structure and to improve the bond strength to zirconia and lithium disilicate. METHODS: Six oligomers were synthesized by combining thiols - pentaerythritol tetra-3-mercaptopropionate (PETMP, P) or trimethylol-tris-3-mercaptopropionate (TMP, T) - with di-functional isocyanates - 1,6-Hexanediol-diissocyante (HDDI) (aliphatic, AL) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (BDI) (aromatic, AR) or Dicyclohexylmethane 4,4'-Diisocyanate (HMDI) (cyclic, CC). Thio-urethanes (20 wt%) were added to a BisGMA/UDMA/TEGDMA organic matrix. Filler was introduced at 60 wt%. The microshear bond strength (μSBS), Weibull modulus (m), and failure pattern of RCs bonded to zirconia (ZR) and lithium disilicate (LD) ceramics was evaluated. Biaxial flexural test and fractographic analysis of porcelain discs bonded to RCs were also performed. The biaxial flexural strength (σbf) and m were calculated in the tensile surfaces of porcelain and RC structures (Z = 0 and Z = -t2, respectively). RESULTS: The μSBS was improved with RCs formulated with oligomers P_AL or T_AL bonded to LD and P_AL, P_AR or T_CC bonded to zirconia in comparison to controls. Mixed failures predominated in all groups. σbf had superior values at Z = 0 with RCs formulated with oligomers P_AL, P_AR, T_AL, or T_CC in comparison to control; σbf increased with all RCs composed by thio-urethanes at Z = -t2. Fractographic analysis revealed all fracture origins at Z = 0. CONCLUSION: The use of specific thio-urethane oligomers as components of RCs increased both the biaxial flexural strength of the porcelain-RC structure and the μSBS to LD and ZR. CLINICAL SIGNIFICANCE: The current investigation suggests that it is possible to reinforce the porcelain-RC pair and obtain higher bond strength to LD and ZR with RCs formulated with selected types of thio-urethane oligomers.
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Authors: Lourenço Correr-Sobrinho; Ana Rosa Costa; Ana Paula P Fugolin; Daniel Sundfeld Neto; Jack L Ferracane; Carmem S Pfeifer Journal: Biomater Investig Dent Date: 2019-11-27