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Thermocycling is widely used in the evaluation of dentin bonding agents. The purpose of this study was to determine the effect of increasing thermocycling times on the shear bond strength of composite resin to dentin using a NTG-GMA/BPDM-type bonding agent. Fifty human molar teeth were ground flat on the buccal surface into dentin (600 grit). Ten specimens were prepared for each thermocycling group of 100, 500, 1000, 2000, and 4000 cycles. The adhesive agent was applied to the dentin according to the manufacturer's instructions. A cyclindrical-shaped matrix was used to form the composite resin that was light cured to the treated dentin surface for 60 seconds. Thermocycling was started after 24 hours of storage in deionized water at 37 degrees C. Shear bond strengths were determined with an Instron universal testing machine at a cross-head speed of 0.5 mm per minute. The bond strengths in megapascals (MPa) were : 100 cycles 18.1 (+/- 5.2) MPa, 500 cycles 19.4 (+/- 4.0)MPa, 1000 cycles 16.5 (+/- 2.9), 2000 cycles 14.6 (+/- 5.1), and 4000 cycles 19.9 (+/- 3.2)MPa. When this data was subjected to an ANOVA, no significant difference was found between the groups.

Adhesion of porcelain to dentin may be important in those cases with little remaining enamel. The purpose of this study was to determine the bond strength of porcelain to dentin using a dentin adhesive (All-Bond) and compare it to the enamel bond strength. Sixty human molar teeth had either a dentin or enamel bonding site prepared by flat grinding to a 600 grit. The teeth were divided into three groups of 20 each. Sixty porcelain cylinders were prepared, hydrofluoric acid etched on one end and silane treated. Twenty of the cylinders were bonded to enamel, 20 bonded to dentin with a dentin adhesive to be tested at 48 hours, and 20 bonded to dentin with a dentin adhesive to be tested after 24 hours of thermocycling (800 cycles at 6 degrees C to 60 degrees C). The specimens were tested in an Instron at a crosshead speed of 0.5 mm/minute. The following bond strengths were found: enamel (19.0 +/- 2.9 MPa), dentin at 48 hours (14.4 +/- 5.4 MPa), and dentin after thermocycling (10.1 +/- 3.8 MPa). When this data was subjected to statistical analysis (ANOVA), there was a significant difference between the groups. A Scheffe's test found that the dentin-porcelain bond at 48 hours was stronger than the thermocycled group, and that the enamel bond was significantly stronger than the two dentin bonds.

Two adhesives, Super Bond and Panavia, were evaluated for shear bond strength to dentin. Twenty human teeth were used for each adhesive. Bonding sites were prepared in dentin (600 grit) and the adhesives applied according to the manufacturers' instructions. Bond strengths were determined with an Instron testing machine at 24 hours. Super Bond developed the strongest bond of 21.59 +/- 3.91 MPa. Panavia produced a lower bond strength of 2.68 +/- 1.45 MPa. Statistically, Super Bond was found to have a stronger bond than Panavia. The same two adhesives were applied to Ni-Cr-Be specimens and compared to Comspan. Twenty Rexillium III specimens were used for each adhesive at 24 hours and 20 for thermocycling. The metal specimens were ground flat (600 grit) and then air abraded with 50-micron aluminous oxide. The adhesives were applied to the metal surface in accordance with the manufacturers' instructions. One group was tested at 24 hours while the second group was tested after thermocycling (2,500 cycles at 6 degrees C to 60 degrees C). At 24 hours, Super Bond had a significantly stronger bond than the other materials. Comparison of the 24-hour to thermocycled bond strengths found Comspan had a significant increase in bond strength, Panavia had no significant change and Super Bond had a significant decrease in bond strength. After 2,500 thermocycles, Comspan, Panavia, and Super Bond were not significantly different in bond strength.

A method for fabrication of a fluoride-releasing retainer is described. The insert releases low levels of fluoride, which should promote remineralization and reduce caries potential. Previous research on the amount of fluoride release is also discussed.

The shear bond strength of the All-Bond system to dentin and a nonprecious alloy was evaluated. Eighty human molar teeth (10 per group) were used in the dentin bonding phase of the study. A bond site was prepared in dentin, and both the succinic anhydride modified HEMA and 10 percent phosphoric acid dentin conditioning techniques were evaluated under both wet and dry conditions. Eighty Rexillium III specimens were used in the metal bonding phase of the study. All-Bond primer and opaquer were applied to the metal surface, followed by a visible light-cured composite restorative material. Dentin bond strengths were determined at 24 hours, while metal bond strengths were evaluated both at 24 hours and after thermocycling (2,500 cycles). Separate groups were established for adhesion to both dentin and metal with the composite placed in a plastic matrix or a gelatin capsule. The highest mean shear bond values to dentin were obtained in the groups with the gelatin capsule bonding procedure, where the dentin was treated with 10 percent phosphoric acid and then blotted dry (wet technique) before the bonding procedure (39.99 MPa). These values were higher than the succinic anhydride modified HEMA-treated group with gentle air drying (wet technique-29.56 MPa). There was essentially no difference in mean shear bond strengths to dentin when a succinic anhydride modified HEMA dentin conditioner was used with aggressive (dry technique) or gentle air drying (wet technique) [29.56 versus 29.08 MPa]. High bond strengths to Rexillium III were obtained when the All-Bond adhesive system was used in combination with a dual-care opaquer and a composite restorative material.(ABSTRACT TRUNCATED AT 250 WORDS)

This study investigated the shear bond strength of a new 4-META adhesive cement (C & B-Metabond) to dentin and Ni-Cr-Be alloy (Rexillium III). Fifteen human molar teeth had dentin bonding sites prepared by grinding away the enamel on a water-cooled abrasive wheel to a 600 grit. Fifteen metal alloy specimens were cast, ground to a 600 grit, and air abraded with 50 micron alumina. The 4-META cement was applied to the dentin and metal in accordance with the manufacturer's instructions. After 24 hours in water at 37 degrees C, the shear bond strengths were recorded. The mean bond strength to dentin and the metal alloy was 20.1 megapascals.

A recently introduced porcelain repair system utilizing 4-META (Etch-Free Primer with C & B-Metabond) was evaluated for bond strength to porcelain. This system purportedly eliminates hydrofluoric acid-etching and silane pretreatment. Forty porcelain specimens were prepared and treated with the 4-META repair system. A resin cylinder was bonded to the treated porcelain surface. Twenty of the specimens were tested after 24 hours while the other 20 were tested after thermocycling (800 cycles at 6 degrees C to 60 degrees C). The mean bond strengths were: 24 hours 17.4 MPa (+/- 4.8), thermocycled 19.1 MPa (+/- 7). Cohesive failure of the porcelain occurred in all of the specimens, both the 24 hour and the thermocycled. These bond strengths compare favorably with or exceed those of other porcelain repair systems tested in other studies.

This study evaluated the ability of five interim endodontic restorative materials to resist microleakage. Sixty extracted human molars were prepared for initial endodontic therapy via occlusal access preparations. After removal of the pulpal tissue, a cotton pellet was placed in the pulp chamber. The access preparations were sealed with one of the following materials or combinations: TERM, Cavit, IRM, Ketac-Silver, or a IRM-Cavit "sandwich" restoration. The specimens were thermocycled for 24 hours (800 cycles), immersed in methylene blue dye for 4 hours, sectioned, and evaluated under a microscope for microleakage. TERM, Cavit, and the IRM-Cavit "sandwich" had virtually no microleakage, while Ketac-Silver and IRM exhibited gross microleakage.

Five new visible light-cure cavity liners/bases that contain fluoride were evaluated for fluoride release over an 8-month period. Fluoride was released from all the materials but decreased significantly over the test period. There was also a significant difference in the amount of fluoride released between the materials. At 8 months, only XR Ionomer and Vitrabond were releasing detectable fluoride, with XR Ionomer releasing significantly more.

Five microfilled resin restorative materials were evaluated for ease of polish and surface finish. Ease of finish was evaluated subjectively; surface smoothness with a profilometer. In addition, scanning electron microscope examinations were conducted to evaluate the structural composition of the microfills. No difference was found in ease of finish, but surface smoothness varied among the five products. The SEM evaluation revealed that four of the products had a heterogeneous composition while the fifth appeared to be a homogeneous microfill.