Influence of selective acid etching on microtensile bond strength of a self-adhesive resin cement to enamel and dentin

Aim: To evaluate the selective acid etching of enamel and dentin on microtensile bond strength (¦ÌTBS) of a self-adhesive resin cement. Methods: Forty-eight bovine teeth were selected and had the buccal surface ground to obtain a flat dentin (n=24) or enamel (n=24) surface. Z250 composite resin blocks (4 x 3 x 8 mm) were prepared for cementation at enamel and dentin. Each substrate received three experimental resin cementation strategies: 1) 37% phosphoric acid etching before the application of RelyX Unicem; 2) application of RelyX Unicem alone; 3) RelyX ARC as a control. Samples were light-cured using a halogen light (Optilux 501, 700mW/cm2), for 40 s. Hourglass-shaped specimens were obtained and submitted to a tensile strength at a crosshead speed of 0.5 mm/min in a universal testing machine. For statistical analysis, data were submitted to ANOVA and Tukey¡¯s test at a pre-set alpha (¨¢=0.05). Results: RelyX Unicem showed similar bond strength value (16.5 MPa) when compared to the pretreatment with acid etching (11.9 Mpa) and to the conventional resin cement (18.1 MPa) for enamel. All luting strategies presented similar dentin bond strength, but significantly lower than enamel bond strength. Conclusions: Acid etching prior to RelyX Unicem application did not improve microtensile bond strength for enamel and dentin.

Efeito da irradiação dos agentes clareadores no esmalte dental com lesão de cárie / Effect of bleaching agents irradiated on dental enamel with caries-like lesions

Analisar os efeitos do peróxido de hidrogênio (35%) irradiado ou não e do dentifrício fluoretado (DF) aplicados no esmalte dental com lesão de cárie. Foram analisados dois agentes clareadores (Whiteness HP Maxx e Easy White) e três modos de aplicação (sem irradiação, irradiação com aparelho de lâmpada halógena ou LED/laser de diodo). Os clareamentos foram realizados nos 1º, 6º e 12º dias de ciclagem de pH. Os resultados de microdureza mostraram que não houve diferença entre os grupos. A microscopia de luz polarizada mostrou desmineralização superficial e na subsuperfície do esmalte para todos os grupos. O DF não foi capaz de controlar a perda mineral provocada pelo clareamento, sugerindo cautela na indicação do clareamento em condições de atividade de cárie.

Effect of storage and disinfection methods of extracted bovine teeth on bond strength to dentin

The aim of this study was to evaluate the effect of storage and disinfection methods (SDM) on bond strength (BS) to bovine dentin, using two adhesive systems: Adper Single Bond and Clearfil Protect Bond. Method: Extracted bovine teeth were assigned to the following SDM: 100% Humidity (HU); Gamma Radiation (GR); Autoclave (AU); 0.10g/mL Thymol (TH); 10% Formalin (FO); Frozen (FR); 0.2% Sodium Azide (SA) and 0.5% Chloramine T (CT) (n=10). The GR and AU groups were submitted to sterilization methods and stored at 100% humidity for 24 hours at 37Cº, before testing. TH,FO, FR, SA and CT groups were stored for three months at 5Cº, except for FR (-4Cº). The adhesive systems were applied according to manufacturerÆs instructions. For BS testing, the micro-shear test was performed, using Tygon mold (0.75mm diameter and 1mm high), which was filled with Clearfil AP-X (Kuraray) composite resin. Data were analyzed by two-way ANOVA and Tukey Test (p<0.05). BS of adhesive systems was similar for all SDM, except for 10%formalin. HU, GR, AU, TH and SA did not change the BS for the adhesives tested. For most of SDM, BS of adhesive systems was similar. Some 3 month-SDM groups (FR, FO and CT) reduced the BS.