Influence of silane and solvated bonding agents on the bond strength to glass-fibre posts

The combined use of silane and solvated bonding agents on the bond strength to glass-fibre posts was investigated. A model Bis-GMA/HEMA adhesive was formulated with no solvent, 30% of ethanol or 80% of acetone. The surfaces of rectangular-shaped posts were silanated or not and one of the agents was applied, except for the control group. Cylinders of resin cement (RelyX ARC, 3M ESPE, Saint Paul, MN, USA) were built-up on the surfaces (n=20) and submitted to shear testing. All groups showed higher bond strengths when the surfaces were silanated. When no silanization was carried out, the use of bonding agents, either solvated or non-solvated, increased the bond strengths. All groups treated with both silane and bonding agent showed higher bond strengths than the group that was only silanated. Control and ethanol-based adhesives were similar, whereas the acetone-based agent yielded higher bond strengths. Adhesive failures were predominant. Combination of silane and adhesive enhanced the bond to fibre posts.39312212

Effect of Various Aging Protocols and Intermediate Agents on the Bond Strength of Repaired Composites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Purpose: To evaluate the effect of two adhesive systems and different aging protocols on the bond strength of a repaired microhybrid composite. Materials and Methods: Eighty test specimens (n = 20) and 10 control specimens measuring 8 x 4 mm were fabricated of a microhybrid composite (4 Seasons, shade A2) and grouped according to time/aging protocol: G1: 24 h in artificial saliva; G2: 7 days in artificial saliva; G3: 30 days in artificial saliva; G4: artificial accelerated aging (AAA) for 384 h; G5: control. After aging, samples were submitted to three types of surface treatment: SB2: Adper Single Bond 2, a two-step adhesive (3M ESPE); SB3: Adper Scotchbond Multi-Purpose, a three-step adhesive (3M ESPE); C: without application of adhesive (control). After this, test specimens were repaired with the same composite of a different shade (C3), and submitted to the microtensile test at a crosshead speed of 0.5 mm/min. Failure modes were analyzed by scanning electron microscopy (Jeol JSM 7500). Statistical analysis was performed using ANOVA and Tukey's test (p < 0.05). Results: G2/SB2 presented significantly lower bond strength values in comparison with the other groups (p < 0.05). The control group presented the highest bond strength values, which differed statistically significantly from SB3, G3/SB2, and G4/SB2 (p < 0.05). Fractographic analysis demonstrated that most samples presented predominantly cohesive failures, excepting GI/SB2, which presented mixed and cohesive failures, and G4/SB2 and G1/SB3, which showed adhesive failures. Conclusion: The repair was more effective when performed after a short period of time and when the 3-step adhesive system (SB3) was used.152137144Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)NAP/MEPA - College of Agriculture "Luiz de Queiroz" - University of Sao PauloFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [2008/11381-7

Light- and time-dependent polymerization of dual-cured resin luting agent beneath ceramic

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Objective. In this study we investigated the degree of conversion (DC) of a dual-cured resin luting agent beneath a ceramic of different thickness. Material and Methods. The luting material (RelyX) was photo-activated for 40 s through ceramic disks (Empress Esthetic, 0.7, 1.4, or 2 mm thick). Dual (DUC) and chemically cured (CC) control groups were obtained. A delayed exposure (DE) procedure was tested in which the material was light-activated after 5 min without using ceramic. DC (%) was measured using infrared spectroscopy at 40 s, 1, 2, 4, 6, 8, and 10 min. Light irradiance and spectrum transmitted through ceramic were measured using a power meter and a spectrometer. Results. A decrease in irradiance was detected with increasing ceramic thickness, but no alteration in the emission profile was observed. At 10 min, all groups showed DC higher than at 40 s. No significant differences were detected for DUC compared with the groups indirectly activated through the ceramic disks. Generally, CC showed the lowest DC values. No significant effect in DC was detected for DE after 10 min. A significant increase in DC was generally detected only up to 4 min. Conclusions. The luting agent was dependent on light exposure and time to obtain improved DC. Neither the indirect activation nor the DE procedure significantly influenced the final DC.665257261Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [140233/2007-5

Short-term PTH administration increases dentine apposition and microhardness in mice

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Objective: The purpose of this study is to investigate the effects of intermittent parathyroid hormone (PTH) administration on the apposition rate and structural features of dentine from mouse incisors. Methods: Young male A/J Unib mice were treated daily for 6 and 10 days with 40 mu g/kg of hPTH 1-34 or a vehicle. Dentine apposition rates measured by fluorescent labels (tetracycline and calcein) and alkaline phosphatase (ALP) plasma levels were evaluated after 6 days of treatment. Knoop microhardness testing and element content measurements in at.% of calcium (Ca), phosphorus (P), oxygen (0), and magnesium (Mg) in the peritubular and intertubular dentine were performed by Energy Dispersive X-ray (EDX) microanalysis via Scanning Electron Microscopy (SEM) after 10 days of treatment. Results: Histometric analysis revealed an increase of 5% in the apposition rate of dentine and 25% in the ALP plasma levels in the PTH treated group. In addition, knoop microhardness testing revealed that the animals treated with PTH had a greater microhardness (11%). EDX microanalysis showed that PTH treatment led to increases in P (23%) and Ca (53%) at.% content, as well as the Ca/P ratio (24%) in peritubular dentine. The chemical composition of intertubular dentine did not vary between the groups. Conclusions: These findings indicate that intermittent administration of hPTH (1-34) increases apposition and mineralization of the dentine during young mice incisor formation. (c) 2012 Elsevier Ltd. All rights reserved.571013131319Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FAPESP [2009/06125-4

Surface/Interface Morphology and Bond Strength to Glass Ceramic Etched for Different Periods

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This study evaluated the influence of etching periods on the surface/interface morphology and bond strength to glass ceramic with or without application of an unfilled resin after silane. Ceramic discs were divided into 12 groups, defined by etching time with 10% hydrofluoric acid: G1/G7 - etching for 10 seconds, G2/G8 - 20 seconds; G3/G9 - 40 seconds; G4/G10 - 60 seconds; G5/G11 - 120 seconds and G6/G12-60 + 60 seconds. All the groups were silanated after etching and G7 - G12 received a layer of unfilled resin after silane. Microshear testing using resin cement was performed, with 12 resin cylinders tested per group. The data was submitted to two-way ANOVA and the Student-Newman-Keuls' test (p<0.05). Evaluation of the etching pattern and bonding interfaces was conducted by SEM. The bond strength means (MPa) were: 19.4 +/- 3.5, 22.3 +/- 5.1, 22.2 +/- 3.2, 17.8 +/- 2.1, 15.3 +/- 3.0 and 14.3 +/- 1.8 for G1-G6 and 17.4 +/- 4.8, 21.3 +/- 2.1, 21.1 +/- 2.3, 24.7 +/- 5.8, 20.4 +/- 2.2 and 18.5 +/- 4.6 for G7-G12. Poor etching was detected after 10 seconds of conditioning; whereas deep channels were extensively observed on surfaces etched for 120 and 60 + 60 seconds. Unfilled voids underlying the ceramic-cement interface were detected when only silane was applied. Full completion of the irregularities on G11 was detected using unfilled resin. When only silane was applied, the 60-second group and those etched for longer periods showed lower bond strengths. When both silane and unfilled resin were applied, all etching periods generally showed similar values. In conclusion, the etching period influenced the surface/interface topography and bond strength to ceramic. The application of unfilled resin was able to infiltrate all unfilled voids beneath the ceramic-cement interface, except on re-etched surfaces.354420427Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [308128/2006-0

Effects of Chlorhexidine and Fluoride on Irradiated Enamel and Dentin

The effectiveness of mouthwash protocols in preventing gamma irradiation therapy damage to the ultimate tensile strength (UTS) of enamel and dentin is unknown. It was hypothesized that the use of chlorhexidine and fluoride mouthwash would maintain the UTS of dental structures. One hundred and twenty teeth were divided into 2 groups: irradiated (subjected to 60 Gy of gamma irradiation in daily increments of 2 Gy) and non-irradiated. They were then subdivided into 2 mouthwash protocols used 3 times per day: 0.12% chlorhexidine, 0.05% sodium fluoride, and control group (n = 10). The specimens were evaluated by microtensile testing. The results of the Tukey test (p < 0.05) indicated that the gamma irradiation therapy significantly reduced the UTS of the enamel, crown, and root dentin. Macromolecular alterations were suggested by optical retardation data in dentin. Structural alterations, in both substrates, were detected by scanning electron microscopy analysis. Mouthwash with 0.12% chlorhexidine partially prevented the damage to the mechanical properties of the irradiated crown dentin, whereas the 0.05% sodium-fluoride-irradiated enamel showed UTS similar to that of non-irradiated enamel.905659664Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG

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 x 0.9 mm(2) 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. 2013. (C) 2013 Wiley Periodicals, Inc.76878879

Influence of Abutment Screw Design and Surface Coating on the Bending Flexural Strength of the Implant Set

The purpose of this study was to analyze the influence of the setting and the presence of solid lubricant on the abutment screw surface on the flexural strength of the joint implant/abutment/screw. Forty abutments were connected to external hex implants, divided into 4 groups (n = 10): FE (titanium alloy screw threaded in the extremity), LE (titanium alloy screw with solid lubricant and thread in the extremity), FT (titanium alloy screw with threaded in all its length), and LT (titanium alloy screw with solid lubricant and thread in all its length). Through the mechanical flexural test, the implant/abutment resistance was evaluated with load applied perpendicular to the long axis in a mechanical testing machine (EMIC) under a speed of 0.5 mm/min. Data were submitted to a statistics test, and results showed statistically significant differences between the FE group and the other groups, and the FE group showed the lowest values. The LE group showed greater values than the LT group, and the values were statistically significant. According to the methodology used, it can be concluded that within noncoated titanium screws, a screw threaded along its entire length provided greater rigidity to the implant set, while with the screw containing solid lubricant, the screw threaded in all its length provided less rigidity of the implant set than screws with the thread only on the end. Among screws with the same geometry, those with the solid lubricant are statistically higher than those which do not have threads just at the end, but those with threads along their entire length do not show statistically significant differences.40212312