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PURPOSE: This study aimed to investigate the electrochemical behavior of commercially pure titanium (grade II) coupled with type IV gold alloy and nickel-chromium alloy at different surface area ratios in 3 different electrolytes. MATERIALS AND METHODS: Titanium was coupled with gold (Ti/Au) and nickel-chromium (Ti/Ni-Cr). For each couple, 9 surface area ratios between titanium and gold or nickel-chromium were prepared. The electrolytes used were 1% lactic acid, tryptic soy broth media, and Streptococcus mutans culture supernatant. The corrosion polarization curves were obtained, and average values of corrosion potential and corrosion current density were calculated. RESULTS: Both Ti/Au and Ti/Ni-Cr were affected by surface area ratios and different electrolytes, showing the least corrosion rate when the ratio was 1:1 and when the lactic acid was used as an electrolyte. CONCLUSIONS: The greater the difference in surface area between titanium and restorative materials, the more corrosive behavior the materials show. The existence of bacteria such as S mutans may aggravate corrosive behavior between different metals. [ABSTRACT FROM AUTHOR]

This study investigated the effect of marginal gap width, luting cement, and restorative material on the wear resistance of the luting cement in areas where no occlusal contact is present. Three types of resin luting cement and one resin-modified glass-ionomer cement were used with two inlay systems, a resin composite, and an all-ceramic system. Bovine enamel represented tooth structure. Toothbrush abrasion was the wear modality. Three predetermined gap widths were selected: 240 +/- 30 microns, 150 +/- 30 microns, and 60 +/- 30 microns. All specimens were thermocycled. Regardless of the luting cement or the restorative material, there was a significant difference (P < 0.05) in wear resistance of the cement among the three gap distances at both the enamel and restoration interface. Vertical wear of the luting cement at the enamel interface increased linearly with marginal gap distance when all four cements were considered together (r2 > 0.51), regardless of type of restorative material used. The resin-modified glass-ionomer cement showed the least amount of wear for all variables considered. Significant differences in wear were found between the four luting cements at wide gap distances (240 microns) at the enamel interface, regardless of type of restorative material used. No significant differences were found between the two restorative materials at the enamel interface at the three gap distances.

Infrared soldering was compared to gas-oxygen torch soldering by testing specimens made from each of the following four classes of metal ceramic alloys: gold-platinum-palladium, gold-palladium, palladium-silver, and nickel-chromium-beryllium. There was no significant difference between infrared and torch soldering for the gold-palladium, palladium-silver, and base metal alloy specimens. However, infrared soldering of the gold-platinum-palladium alloy samples produced significantly weaker joints than those produced by torch soldering.

The dimensions of 120 maxillary first premolar all-ceramic tooth preparation designs were measured and analyzed to determine relationships between design features and recorded differences in the strengths of restorations fabricated for each preparation design. To assess clinical feasibility, the remaining dentin thickness of each preparation design was measured. A total occlusal convergence angle of 10 degrees provided the best combination of restoration strength and remaining dentin thickness. Five degrees produced the weakest restorations, and 15 degrees and 20 degrees required greater tooth reduction and pulp proximity. Stronger restorations were noted when the shoulder finish line had a sharp axiogingival line angle, possessed minimal cervical inclination, and was located as close as possible to the same occlusocervical level on all four axial surfaces.

Three denture base resins, two designed for microwave polymerization and one for host-water-bath-processing, were compared. Results indicated that all four tested thicknesses (3, 6, 11.6, and 17.7 mm) of the water-bath-polymerized samples and one of the microwave-polymerized resins were porosity-free. When the water-bath-polymerized material was microwave processed, porosity was found when resin thickness exceeded 3 mm. When one resin designed for microwave polymerization was irradiated using the high-wattage (513 W), shorter cycle (4 minutes 52 seconds), porosity also occurred when the thickness exceeded 3 mm. Porosity did not occur until there was 9 mm of thickness when the lower-wattage (75.9 W), longer cycle (15 minutes 26 seconds) was used. No significant differences in transverse strength or hardness were noted between the materials.

Four acrylic resins and two composite resins for fabricating provisional fixed prosthodontic restorations were studied to determine temperature change during polymerization, surface hardness, marginal fit, wear resistance, transverse strength, transverse repair strength, surface roughness and polishability, color stability, and stain resistance. While certain materials exhibited advantageous properties in one or more of the tests, no one material was superior to the others in all tests.

Two methods of evaluating the accuracy of resin complete denture bases were compared by measuring the fit of four resin materials and two processing techniques. The use of moire topography was found to be comparable to measuring the weight of impression material retained between the denture base and master cast.