Bruno de Castro Ferreira Barreto

Microtensile Bond Strength of Methacrylate and Silorane Resins to Enamel and Dentin

The aim of this study was to evaluate the microtensile bond strength (µTBS) of two substrates (enamel and dentin) considering two study factors: type of composite resin [methacrylate-based (Filtek Supreme) or silorane-based (Filtek LS)] and aging time (24 h or 3 months). Twenty human molars were selected and divided into 2 groups (n=10) considering two dental substrates, enamel or dentin. The enamel and dentin of each tooth was divided into two halves separated by a glass plate. Each tooth was restored using both tested composite resins following the manufacturers instructions. The samples were sectioned, producing 4 sticks for each composite resin. Half of them were tested after 24 h and half after 3 months. µTBS testing was carried out at 0.05 mm/s. Data were analyzed by three-way ANOVA and Tukeys HSD tests at α=0.05. Significant differences between composite resins and substrates were found (p<0.05), but no statistically significant difference was found for aging time and interactions among study factors. The methacrylate-based resin showed higher µTBS than the silorane-based resin. The µTBS for enamel was significantly higher than for dentin, irrespective of the composite resin and storage time. Three months of storage was not sufficient time to cause degradation of the bonding interaction of either of the composite resins to enamel and dentin.

Influence of chlorhexidine on dentin adhesive interface micromorphology and nanoleakage expression of resin cements

This study focused on adhesive interface morphologic characterization and nanoleakage expression of resin cements bonded to human dentin pretreated with 1% chlorhexidine (CHX). Thirty‐two non‐carious human third molars were ground flat to expose superficial dentin. Resin composite blocks were luted to the exposed dentin using one conventional (RelyX ARC) and one self‐adhesive resin cement (RelyX U100), with/without CHX pretreatment. Four groups (n = 8) were obtained: control groups (ARC and U100); experimental groups (ARC/CHX and U100/CHX) were pretreated with 1% CHX prior to the luting process. After storage in water for 24 h, the bonded teeth were sectioned into 0.9 × 0.9 mm2 sticks producing a minimum of 12 sticks per tooth. Four sticks from each tooth were prepared for hybrid layer evaluation by scanning electron microscope analysis. The remaining sticks were immersed in silver nitrate for 24 h for either nanoleakage evaluation along the bonded interfaces or after rupture. Nanoleakage samples were carbon coated and examined using backscattered electron mode. Well‐established hybrid layers were observed in the groups luted with RelyX ARC. Nanoleakage evaluation revealed increase nanoleakage in groups treated with CHX for both resin cements. Group U100/CHX exhibited the most pronouncing nanoleakage expression along with porous zones adjacent to the CHX pretreated dentin. The results suggest a possible incompatibility between CHX and RelyX U100 that raises the concern that the use of CHX with self‐adhesive cements may adversely affect resin‐dentin bond. Microsc. Res. Tech. 76:788–794, 2013.

Finite Element Analysis in Dentistry - Improving the Quality of Oral Health Care

The primary function of the human dentition is preparation and processing of food through a biomechanical process of biting and chewing. This process is based on the transfer of masticatory forces, mediated through the teeth (Versluis & Tantbirojn, 2011). The intraoral environment is a complex biomechanical system. Because of this complexity and limited access, most biomechanical research of the oral environment such as restorative, prosthetic, root canal, orthodontic and implant procedures has been performed in vitro (Assuncao et al., 2009). In the in vitro biomechanical analysis of tooth structures and restorative materials, destructive mechanical tests for determination of fracture resistance and mechanical properties are important means of analyzing tooth behavior. These tests, however, are limited with regard to obtaining information about the internal behavior of the structures studied. Furthermore, biomechanics are not only of interest at the limits of fracture or failure, but biomechanics are also important during normal function, for understanding property-structure relationships, and for tissue response to stress and strain. For a more precise interrogation of oral biomechanical systems, analysis by means of computational techniques is desirable.

Effect of previous desensitizer and rewetting agent application on shear bond strength of bonding

This study evaluated the effect of desensitizer and rewetting agent on dentin shear bond strength. One hundred thirty five bovine incisive teeth had their buccal surfaces ground down to produce a fl at superficial dentin surfaces and received the following treatments: G1- One Step Plus (OSP) and resin cylinder adhesive fi xation (RI); G2- Gluma One Bond (GOB) and RI; G3- Single Bond (SB) and RI; G4- Aqua-Prep (AP) + OSP and RI; G5- Gluma Desensitizer (GD) + GOB and RI; G6- GD + SB and RI; G7- GD + OSP and RI; G8- AP + GOB and RI; G9- AP + SB and RI. The specimens were stored at 37°C and 100% humidity for 24 hours and a shear bond test was performed with a mechanical testing machine, at a crosshead speed of 0.5 mm⁄min. The data were submitted to one-way ANOVA followed by the Tukey test (p<0.05). The results (MPa) were: G1: 10.75(2.64)a; G2: 10.28(2.58)a; G3: 11.63(4.59)a; G4: 10.93(4.88)a; G5: 10.15(3.95)a; G6: 11.82(4.14)a; G7: 9.85(2.15)a; G8: 5.48(1.94)b; G9: 10.62(2.83)a. The resistance of the GOB adhesive system was negatively affected by AP application. The use of desensitizer and rewetting agent does not compromise the bond strength when they are compatible with the adhesive system used.