A.A.M. Mendonça

Adhesion strategy and early bond strengths of glass-fiber posts luted into root canals

This study investigated the effect of coinitiator solutions and self-adhesive resin cement on the early retention of glass-fiber posts. Cylindrical glass-fiber posts were luted into 40 incisor roots with different adhesion strategies (n = 10): SB2, Single Bond 2 + conventional resin cement (RelyX ARC); AP, Scotchbond Multipurpose Plus (SBMP) activator + primer + ARC; APC, SBMP activator + primer + catalyst + ARC; and UNI, self-adhesive cement (RelyX Unicem). Pull-out bond strength results at 10 min after cementation showed APC > UNI > SB2 = AP (P < 0.05). The adhesion strategy significantly affected early bonding to root canals.

Effect of temporary cements on the bond strength of a resin cement to a pre-hybridized dentin = Influência de cimentos temporários na resistência de união de um cimento resinoso sobre a dentina pré-hibridizada

This study assessed the bond strength of a resin cement when Immediate Sealed Dentin (ISD) was contaminated by different temporary cements applying a microshear test. Forty-eight fragments of third molar crowns were mounted in acrylic resin and worn until the dentin was exposed. The substrates were sealed with a 3-step conventional adhesive system and divided into four groups (n=12): Control (without temporary cement) and three groups that used different temporary cements - Provy, RelyX Temp NE, and Provitemp. The temporary cements were removed after 7 days of storage. Resin cement RelyX ARC was applied to the contaminated substrates. Microshear bond strength was evaluated using a universal testing machine (0.5 mm/min). Data was analyzed with ANOVA and a Dunnett post-hoc test (p<0.05). Additionally, three samples from each group were prepared for scanning electron microscope analysis. Means and standard deviations of microshear bond strength (MPa) were 17.96±1.65, 16.70±1.43, 20.43±1.30 and 33.75±4.72 for Control, Provy, RelyX Temp, and Provitemp, respectively. Statistically significant difference was observed between the Control and Provitemp samples (p=0.0002). Adhesive failures were dominant (50%), followed by cohesive failures with cement (26%), and cohesive failures with dentin (24%). Residues of Provy and Provitemp were observed on the sealed dentin. Provitemp temporary cement sealing increased the microshear bond strength of the resin cement on dentin treated with IDS.

Efeito da intensidade de fontes de luz e barreiras de cerâmica na microdureza de cimento resinoso dual

IntroducaoO cimento resinoso dual e o principal material para cimentacao de cerâmicas. Contudo, fatores, como fonte de luz, podem influenciar no desempenho do cimento.ObjetivoAvaliar a influencia de duas fontes de luz de diferentes intensidades sobre a microdureza de um cimento resinoso quando fotoativado sob diferentes cerâmicas.Material e metodoForam fotoativados 40 especimes de cimento resinoso dual (10 mm × 1,0 mm) por meio de duas fontes de luz LED, com intensidades de 1.000 mW/cm² e 800 mW/cm² durante 40 segundos, sob cerâmicas (15 mm × 2 mm) a base de zirconia, espinelio MgAl2O4 e dissilicato de litio. No grupo controle, foi utilizada uma placa de vidro de mesma dimensao. As amostras tiveram a superficie regularizada com lixa d`agua (600 e 1200). Apos armazenagem a seco no escuro (24 h), foram realizadas as medidas de microdureza Vickers (HMV Shimadzu - 50g/10 segundos). Os dados foram submetidos a Anova fatorial e ao teste de Tukey com nivel de significância de 5%.ResultadoO cimento polimerizado apresentou valor medio de microdureza e desvio padrao para o grupo controle de 43,9±1,5 e 43,4±1,3, para as intensidades de 1.000 mW/cm2 e 800 mW/cm2, respectivamente. O menor valor de microdureza do cimento foi observado para a cerâmica a base de espinelio MgAl2O4, polimerizado a 800 mW/cm², com valor de 34,3±3,3.ConclusaoO tipo de cerâmica e a intensidade da fonte de luz influenciam na microdureza do cimento. A intensidade de 1.000 mW/cm2 sobre as cerâmicas a base de zirconia e espinelio MgAl2O4 resultaram na melhor combinacao de valores de dureza do cimento.