Effect of mucoprotein on the bond strength of resin composite to human dentin.

The purpose of this study was to test the bond strength and analyze the morphology of the dentin-adhesive interface of two etch and rinse and two self-etch adhesive systems with two kinds of artificial saliva (with and without 450 mg/L mucin) contamination under different conditions of decontaminating the interface. Bonded specimens were sectioned perpendicularly to the bonded surface in 1-mm thick slabs. These 1-mm thick slabs were remounted in acrylic blocks and sectioned in sticks perpendicular to the bonding interfaces with a 1-mm(2) area. Nine specimens from each condition were tested after 24 h on a testing machine (Instron) at a speed of 0.5 mm/min for a total of 360 specimens. Mean and standard deviations of bond strength (MPa) were calculated. ANOVA showed significant differences as well as Fisher's PLSD intervals (p < 0.05). The following values are the results for different groups: Control group 34-60 MPa, saliva without mucin 0-52 MPa, and saliva with mucin 0-57 MPa. Failure sites were mixed and adhesive failure was common for the low bond strength results. P&BNT with ideal conditions and following the manufacturer's instructions (control) had the highest bond strengths and the dentin-adhesive interface exhibited an ideal morphology of etch-and-rinse system. SEM gave complementary visual evidence of the effect in the dentin/adhesive interface structure with some contaminated conditions compared with their respective control groups. This in vitro artificial saliva model with and without mucin showed that an organic component of saliva could increase or decrease the bond strength depending on the specific bonding agent and decontamination procedure.

Force needed to separate acrylic resin from primed and unprimed frameworks of different designs.

PURPOSE: Poor mechanical and chemical bondings at the interface between a framework and denture base resin have been responsible for many removable partial denture failures. This study tested the force necessary to separate acrylic resin bases from test frameworks using different acrylic retention designs (smooth metal plate, metal plate with bead retention, lattice retention, and mesh retention). The force needed to separate acrylic resin from primed test frameworks was also measured. MATERIALS AND METHODS: Eighty chromium-cobalt test frameworks were fabricated using preformed wax patterns and cast according to manufacturer's instructions. Half the specimens were primed prior to acrylic processing. The same base acrylic was used for all specimens. Separation forces that fractured acrylic resin from test frameworks were generated by a universal testing machine at a crosshead speed of 25 mm/min. Loads at failure and types of failure were recorded. Data were analyzed using ANOVA. RESULTS: The mean separation force of acrylic resin from unprimed retention designs was highest for the metal plate with beads (3.1 kN), followed by mesh (2.8 kN) and lattice (2.1 kN), and lowest (0.1 kN) for the smooth metal plate. The mean separation force for primed acrylic retention designs was highest for the metal plate with beads (4.2 kN), followed by mesh (3.4 kN) and smooth metal plate (3.0 kN), and lowest for lattice retention (2.6 kN). Bond failure occurred both adhesively at the interface between metal and acrylic resin and cohesively within the acrylic resin. Cohesive bond failure increased when specimens were primed. The rate of cohesive bond failure remained the same for primed mesh retention specimens. CONCLUSIONS: Significantly increased force was necessary to separate the acrylic from each design of primed test specimens compared with unprimed specimens of the same design. The primed metal plate with beads exhibited significantly greater separation force than the other three designs. Primed mesh had significantly greater separation force values than primed lattice and smooth metal plate. Primed lattice was significantly less retentive than the other three primed designs. Except for the retentive mesh specimens, there was higher occurrence of cohesive failures in the acrylic resin when the frameworks were primed.

In vitro tensile bond strength of denture repair acrylic resins to primed base metal alloys using two different processing techniques.

PURPOSE: Approximately 38% of removable partial denture (RPD) failures involve fracture at the alloy/acrylic interface. Autopolymerizing resin is commonly used to repair RPDs. Poor chemical bonding of repair acrylic to base metal alloys can lead to microleakage and failure of the bond. Therefore, ideal repair techniques should provide a strong, adhesive bond. This investigation compared the tensile bond strength between cobalt-chromium (Super Cast, Pentron Laboratory Technologies, Llc., Wallingford, CT) and nickel-chromium (Rexalloy, Pentron Laboratory Technologies, Llc.) alloys and autopolymerized acrylic resin (Dentsply Repair Material, Dentsply Int, Inc, York, Pa) using three primers containing different functional monomers [UBar (UB), Sun Medical Co., Ltd., Shiga, Japan: Alloy Primer (AP) Kuraray Medical Inc., Okayama, Japan; and MR Bond (MRB) Tokyuyama Dental Corp., Tokyo, Japan] and two processing techniques (bench cure and pressure-pot cure). MATERIAL AND METHODS: One hundred and twenty eight base metal alloy ingots were polished, air abraded, and ultrasonically cleaned. The control group was not primed. Specimens in the test groups were primed with one of the three metal primers. Autopolymerized acrylic resin material was bonded to the metal surfaces. Half the specimens were bench cured, and the other half were cured in a pressure pot. All specimens were stored in distilled water for 24 hours at 37 degrees C. The specimens were debonded under tension at a crosshead speed of 0.05 cm/min. The forces at which the bond failed were noted. Data were analyzed using ANOVA. Fisher's PLSD post hoc test was used to determine significant differences (p < 0.05). Failure modes of each specimen were evaluated under a dissecting microscope. RESULTS: Significant differences in bond strength were observed between combinations of primers, curing methods, and alloys. Primed sandblasted specimens that were pressure-pot-cured had significantly higher bond strengths than primed sandblasted bench-cured specimens. The pressure-pot-curing method had a significant effect on bond strength of all specimens except Co-Cr alloy primed with UB. The highest bond strength was observed for both Co-Cr and Ni-Cr alloys that were sandblasted, primed with MRB, and pressure-pot cured. Co-Cr alloys primed with UB had the lowest bond strength whether bench cured or pressure-pot cured. Primed specimens generally experienced cohesive bond failures within the primer or acrylic resin. Nonprimed specimens generally experienced adhesive bond failures at the resin/metal interface. CONCLUSIONS: Within the limitations of this study, MRB provided the highest bond strength to both Ni-Cr and Co-Cr alloys. Generally, bond strength improved significantly when specimens were primed. Pressure-pot curing, in most cases, resulted in higher bond strength than bench curing. The results of this in vitro study suggest that MRB metal primer can be used to increase bond strength of autopolymerized repair acrylic resin to base metal alloys. Curing autopolymerized acrylic under pressure potentially increases bond strength.

Materials used in prefabricated post and core systems. A review of the literature.

A plethora of prefabricated post and core materials is currently available for the restoration of endodontically treated teeth. The materials presented demonstrate a variety of mechanical properties and esthetic potential, while the selection of the optimum post and core system depends upon clinical judgment and the specific clinical situation.

Effect of core diameter and surface treatment on the retention of resin composite cores to prefabricated endodontic posts.

PURPOSE: With advances in adhesive dentistry and current emphasis on esthetic restorations, dowel systems have been developed to take advantage of these new techniques. Of interest when using these systems is the interaction between core materials and post materials. This investigation compared the tensile retentive force of two resin composite core materials to two metallic and one non-metallic prefabricated endodontic posts. Two dimensions of core build-up and two post-surface treatments were tested. MATERIALS AND METHODS: One hundred twenty posts (stainless steel, titanium alloy, and glass fiber-impregnated resin) were secured in a jig with 4 mm of the post extending into a cylindrical matrix. The matrix formed cylinders with diameters of 3 and 5 mm into which resin composite was inserted. The posts were treated or not treated with a bonding agent. After storage for 24 hours at 100% humidity, five specimens per condition were tested in an Instron testing machine at a crosshead speed of 0.5 mm/min. Failure loads were recorded in kilograms and failure modes were observed under light microscopy (40 x). Four-way analysis of variance and multiple comparison testing were used to compare means at the 0.05 level of significance. RESULTS: The means and standard deviations of tensile loads were calculated. All variables were significant in either main effects or interactions ( p<0.05). Fisher's PLSD intervals for post, core, treatment, and diameter were 2.0, 1.6, 1.6, and 1.6 kg, respectively. In most cases, the retentive force recorded for metallic posts was higher than that of glass fiber posts. Titanium posts had higher retentive forces than did the stainless steel posts. For metallic posts, 5-mm cores provided higher forces than 3-mm cores. In the glass fiber group, core diameter was not significant. For core materials, Build-It gave higher results with stainless steel posts, and FluoroCore gave higher results with the titanium ones. The surface treatment results were mixed. In the metallic post groups the adhesive failure data ranged between 80% and 100%, whereas in the glass fiber post groups, adhesive failures ranged between 60% and 70%. CONCLUSIONS: Within the limitations of this study, the metallic post groups always provided higher tensile retentive forces, with the titanium post groups showing higher retentive forces than the stainless steel ones. In the glass fiber post groups, different core diameters did not affect retention values.

Effect of filler addition on the bonding parameters of dentin bonding adhesives bonded to human dentin.

PURPOSE: To determine the effect of filler addition on two total-etch, single component bonding systems on the bond strength, displacement at debonding, stiffness of debonding and energy absorbed to debonding of resin composites to human dentin. METHODS: Two dentin bonding systems with no-filler (OS and SB) and filler-added (OSP and SBP) versions were studied. The dentin surfaces of human teeth were exposed with 600-grit SiC. TPH Spectrum A2 was used to bond to the dentin surfaces in the form of a truncated cone, 3 mm in diameter at the bonding surfaces and 5 mm in diameter at the base. Bonded specimens were stored in distilled water at 37 degrees C for 24 hours. They were then debonded in tension with a universal testing machine at a cross-head speed of 0.5 mm/minute. Displacement at debonding, stiffness and energy to debonding were calculated based on the stress-displacement curve. RESULTS: Bond strength, displacement at debonding and energy to debonding (measured and elastic) were influenced by the brand of the adhesive (OS/OSP vs. SB/SBP), but were not influenced by the filler addition based on two-way analysis of variance. Bond strength was in the range of 24.4-30.1 MPa, and there were significant differences between the bond strengths of OS and SB. Displacement and energy to debonding (measured and elastic) were different between the adhesives. Bond strength, bond stiffness and energy to debonding (measured) showed significant correlations.

Bond strength of composite to astringent-contaminated dentin using self-etching adhesives.

PURPOSE: To determine the effects of contamination by ferric sulfate and aluminum chloride astringents on the bond strength of composite bonded to superficial dentin using self-etching adhesives. METHODS: Freshly extracted human teeth were ground to expose superficial dentin and polished to 600 grit. One of three self-etching adhesive systems and restorative composites were bonded to the specimens, with contamination by one of three astringents and five surface conditions (no contamination, moist dentin control; contaminant, air, adhesive; contaminant, water rinse, air, adhesive; contaminant, water rinse, glycolic acid scrub, rinse, adhesive; contaminant, water rinse, chlorhexadine scrub, rinse, adhesive). Composite was bonded to the surfaces in the shape of an inverted, truncated cone (n = 5, 180 specimens total). Specimens were stored in water at 37 degrees C for 24 hours, then de-bonded in tension with a testing machine at a crosshead speed of 0.5 mm/minute. Tensile bond strengths (MPa) were calculated. RESULTS: Means (SD) were compared using analysis of variance. Significant differences (Fisher's PLSD) were found among all variables. SE and ABF had the highest control values, but were affected most by astringent contamination. Ferric sulfate reduced bond strengths the greatest in most cases, and aluminum chloride putty reduced bond strengths the least. Chlorhexadine rinse was most effective in restoring bond strength values.

Factors affecting in vitro bond strength of bonding agents to human dentin.

Four generations of total-etch (fourth, fifth) and self-etching (sixth, seventh) bonding agents for use with resin composites are commercially available in the United States. Innovations in bonding agents include: filled systems, release of fluoride and other agents, unit dose, self-cured catalyst, option of etching with either phosphoric acid or self-etching primer, and pH indicators. Factors that can affect in vitro bond strength to human dentin include substrate (superficial dentin, deep dentin; permanent versus primary teeth; artificial carious dentin), phosphoric acid versus acidic primers, preparation by air abrasion and laser, moisture, contaminants, desensitizing agents, astringents, and self-cured restorative materials. This article reviews studies conducted at the Houston Biomaterials Research Center from 1993 to 2003. Results show that in vitro bond strengths can be reduced by more than 50% when bonding conditions are not ideal.