title: Influence of thicknesses of smear layer on the transdentinal cytotoxicity and bond strength of a resin-modified glass-ionomer cement.
abstract: This study evaluated the transdentinal cytotoxicity (TC) and the bond strength (BS) of a resin-modified glass-ionomer cement (RMGIC) applied to dentin covered with smear layer (SL) of different thicknesses. Forty dentin discs had thick (TSL) or thin (THSL) smear layer created on their occlusal side. In artificial pulp chambers, MDPC-23 cells were seeded on the pulpal side of the dentin discs and divided into five groups: G1TC: no treatment (control); G2TC: TSL + RMGIC; G3TC: THSL + RMGIC; G4TC: TSL removal + RMGIC; G5TC: THSL removal + RMGIC. After 24 h, cell metabolism and morphology were evaluated by the methyltetrazolium (MTT) assay and by scanning electron microscopy (SEM), respectively. For BS, the following groups were determined: G1BS: TSL removal + RMGIC; G2BS: THSL removal + RMGIC; G3BS: TSL + RMGIC; G4BS: THSL + RMGIC. Shear bond strength was tested to failure in a mechanical testing machine MTS (0.5 mm/min). Statistically significant difference was observed only between the control and experimental groups (Kruskal-Wallis, p<0.05). The metabolic activity of the viable MDPC-23 cells in G2TC, G3TC, G4TC and G5TC decreased by 54.85%, 60.79%, 64.12% and 62.51%, respectively. Mean shear bond strength values for G1BS, G2BS, G3BS and G4BS were 7.5, 7.4, 6.4 and 6.7 MPa, respectively, without significant difference among them (ANOVA, p>0.05). RMGIC presented moderate transdentinal cytotoxic effects. Maintenance or removal of smear layer did not affect the bond strength of RMGIC to dentin substrate.
authors.affiliation: Araraquara Dental School, Univ Estadual Paulista, Araraquara, SP, Brazil.
authors.forename: Adriano Augusto Melo
authors.initials: AA
authors.lastname: de Mendonça
authors.forename: Camila Fávero
authors.initials: CF
authors.lastname: de Oliveira
authors.forename: Josimeri
authors.initials: J
authors.lastname: Hebling
authors.forename: Carlos Alberto de Souza
authors.initials: CA
authors.lastname: Costa
mesh_terms: D018929:Cell Culture Techniques; D002460:Cell Line; D048430:Cell Shape; D002470:Cell Survival / Q000187:drug effects; D004396:Coloring Agents; D055117:Curing Lights, Dental; D001840:Dental Bonding; D003782:Dental Pulp / Q000166:cytology / Q000187:drug effects; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000648:ultrastructure*; D003806:Dentin Permeability / Q000187:drug effects; D005899:Glass Ionomer Cements / Q000737:chemistry / Q000633:toxicity*; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000295:instrumentation / Q000379:methods; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements / Q000737:chemistry / Q000633:toxicity*; D033081:Shear Strength; D016369:Smear Layer; D013314:Stress, Mechanical; D013696:Temperature; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D004396:Coloring Agents; D005899:Glass Ionomer Cements; D019279:Resin Cements; D013778:Tetrazolium Salts; D013844:Thiazoles; D014867:Water; C067790:Vitrabond; C022616:thiazolyl blue