Walison Arthuso Vasconcellos

Tensile bond strength of self-etching versus total-etching adhesive systems under different dentinal substrate conditions

The use of acid etchants to produce surface demineralization and collagen network exposure, allowing adhesive monomers interdiffusion and consequently the formation of a hybrid layer, has been considered the most efficient mechanism of dentin bonding. The aim of this study was to compare the tensile bond strength to dentin of three adhesive systems, two self-etching ones (Clearfil SE Bond--CSEB and One Up Bond F--OUBF) and one total-etching one (Single Bond--SB), under three dentinal substrate conditions (wet, dry and re-wet). Ninety human, freshly extracted third molars were sectioned at the occlusal surface to remove enamel and to form a flat dentin wall. The specimens were restored with composite resin (Filtek Z250) and submitted to tensile bond strength testing (TBS) in an MTS 810. The data were submitted to two-way ANOVA and Tukeys test (p = 0.05). Wet dentin presented the highest TBS values for SB and CSEB. Dry dentin and re-wet produced significantly lower TBS values when using SB. OUBF was not affected by the different conditions of the dentin substrate, producing similar TBS values regardless of the surface pretreatments.

Effect of the post geometry and material on the stress distribution of restored upper central incisors using 3D finite element models. Stress distribution on incisors with posts

This study evaluated the effect of geometry and material of posts on the stress distribution in maxillary central incisors, using the finite element method. Four 3D models were developed: (i) healthy tooth and restored teeth using (ii) tapered, (iii) cylindrical and (iv) two-stage cylindrical posts. Materials used were stainless steel, titanium, zirconium dioxide, carbon and glass fibers on Bis-GMA matrix. Two stress concentration regions were verified: (i) adjacent to the alveolar bone crest and (ii) dentin-post boundary. Tensile and compressive stresses were concentrated on the palatal and facial surface, respectively, for all the analyzed models. In the dentin portion close to the alveolar bone crest, different anatomical form and material posts presented similar patterns of stress distribution. However, in the dentin-post boundary, more favorable results were presented by glass fibers and carbon fibers posts, followed by titanium, being the worst results associated to the use of stainless-steel or zirconium dioxide posts. Still in the dentin-post boundary, tapered posts presented more favorable results than cylindrical posts, followed by two-stage cylindrical posts, which presented the highest levels of stress concentrations. It was concluded that the insertion of post alters the pattern of stress distribution when compared with the healthy tooth and that smaller stress concentrations are associated to the use of glass fiber or carbon fiber tapered posts.

Influence of cavity preparations and restorative procedures on stress distribution by finite element method

Floriano J. C. Bello, Carlos A. Cimini Jr1, Rodrigo C. Albuquerque2, Walison A. Vasconcellos3 Restorative Dentistry, University Federal de Minas Gerais, 1Department of Mechanical Engineering, School of Engineering, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, 2Department Restorative Dentistry, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, 3Department Dentistry, Estadual University of Montes Claros, Montes Claros, Minas Gerais, Brazil

Tensile bond strength: Evaluation of four current adhesive systems in abraded enamel and deep dentin

This study aimed to evaluate the tensile bond strength of adhesive systems in abraded enamel and deep dentin of the occlusal surface of forty human molar teeth. Enamel surfaces as well as the rest of the teeth were coated with epoxy resin and regularized and polished with silicon carbide sandpapers. The 40 teeth were randomized into eight groups of five teeth per group. Four groups were assigned to have deep dentin as the dental substrate and the other four had abraded enamel as the substrate for the adhesives to be tested. The adhesives being tested were the total etching Single Bond: SB, the self-etching Clearfil SE bond: CSEB, self-etching One Up Bond F: OUBF and the self-etching Self-Etch Bond: SEB adhesives. The samples (teeth) were restored with composite resin and subjected to a traction assay. The results were statistically analyzed using the ANOVA and TUKEY tests. The total etching SB adhesive system had the greatest bonding strength of all the adhesives tested, on both dental substrates (20.1 MegaPascals (MPa) on abraded enamel and 19.4 MPa on deep dentin). Of the self-etching dental adhesives tested, CSEB had the greatest bonding strength on both substrates (14.6 MPa on abraded enamel and 15.4 MPa on deep dentin). Both OUBF (11.0 MPa for enamel, 13.1 MPa for dentin) and SEB (10.2 MPa for enamel, 12.6 MPa for dentin) showed comparable bonding strengths without any significant differences for either substrate Thus, the total etching SB adhesive system had better bonding strength than the other self-etching adhesives used, regardless of the dental substrate to which the adhesives had been bonded.