Biomedical subjects

Adrian C Shortall

Publications and source records attributed to Adrian C Shortall.

3 recordsLinked to original sources

PubMed2002

Potential countersample materials for in vitro simulation wear testing.

OBJECTIVES: Any laboratory investigation of the wear resistance of dental materials needs to consider oral conditions so that in vitro wear results can be correlated with in vivo findings. The choice of the countersample is a critical factor in establishing the pattern of tribological wear and in achieving an efficient in vitro wear testing system. This research investigated the wear behavior and surface characteristics associated with three candidate countersample materials used for in vitro wear testing in order to identify a possible suitable substitute for human dental enamel. METHODS: Three candidate materials, stainless steel, steatite and dental porcelain were evaluated and compared to human enamel. A variety of factors including hardness, wear surface evolution and frictional coefficients were considered, relative to the tribology of the in vivo situation. RESULTS: The results suggested that the dental porcelain investigated bore the closest similarity to human enamel of the materials investigated. SIGNIFICANCE: Assessment of potential countersample materials should be based on the essential tribological simulation supported by investigations of mechanical, chemical and structural properties. The selected dental porcelain had the best simulating ability among the three selected countersample materials and this class of material may be considered as a possible countersample material for in vitro wear test purposes. Further studies are required, employing a wider range of dental ceramics, in order to optimise the choice of countersample material for standardized in vitro wear testing.

Analysis of Variance↗

PubMed2002

Influence of fiber type and wetting agent on the flexural properties of an indirect fiber reinforced composite.

STATEMENT OF PROBLEM: Different fiber types are available for reinforcing composite restorations. Little information exists regarding optimal fiber type/bonding agent combinations. PURPOSE: This in vitro study examined the influence of storage time and 2 fiber wetting agents on the flexural properties of an indirect dental composite reinforced by 3 fiber types. MATERIAL AND METHODS: Three types of fiber (ultra-high molecular weight polyethylene, Kevlar, and Glass fiber) were used to reinforce samples of an indirect composite (Artglass) prepared to test flexural properties. Each fiber type was used to prepare 3 groups of 10 specimens after fiber wetting with an unfilled or a filled resin bonding agent. All fibers were weighed to an accuracy of 0.01 mg to standardize the amount of fiber placed in the base (tensile side) of the specimen preparation mold (2 x 2 x 25 mm). Fiber-reinforced samples wetted with the unfilled resin were stored for 24 hours before flexural testing, whereas separate groups of fiber-reinforced samples wetted with the filled resin were tested after both 24 hours and 6 months storage in water at 37 degrees C. Two additional groups of unreinforced composite control specimens (10 samples per group) were prepared, one for each of the 2 storage times, resulting in 11 groups total. Mean flexural strengths (MPa) and flexural modulus (GPa) values were determined in a 3-point bend test at a crosshead speed of 1 mm/min by use of a universal testing machine. Comparisons between means were performed with 2- and 1-way analysis of variance tests (alpha=.01) to demonstrate the influence of storage time, fiber wetting agent, and fiber type on the flexural properties of the indirect dental composite tested. RESULTS: Significant increases (124% to 490%) in mean flexural strength (P<.01) were found for all fiber-reinforced groups in comparison to the unreinforced controls at both storage time intervals. The silane containing unfilled bonding agent gave the greatest reinforcing effect (364%) when used with the glass fiber material. After 6 months storage in water, a significant decline (28%) occurred in the mean flexural strength of the glass fiber-reinforced specimens (P<.01) when the filled bonding agent was used. CONCLUSION: Within the limitations of this study, the choice of fiber type and wetting agent was shown to have a significant positive influence on the flexural properties of the fiber-reinforced composite. When used with the silane containing unfilled bonding agent, the glass fiber increased the mean flexural strength of the unreinforced indirect composite by 364%.

Analysis of Variance↗

PubMed2002

Effect of accelerated restorative techniques on the microleakage of Class II composites.

PURPOSE: To assess the marginal seal of Class II resin-based composite restorations cured by a high intensity halogen light or a plasma arc light. MATERIALS AND METHODS: Class II cavities were prepared in extracted molar teeth with cervical margins located apical to the cemento-enamel junction. Cavities were restored with a posterior resin-based composite (Tetric Ceram) using either a two-increment or a bulk placement and cure restorative technique after application of bonding agent (Excite). Test parameters included light unit type/curing mode, application of flowable composite and restorative technique. After thermocycling, the teeth were immersed in basic fuchsin dye. Sectioned restorations were examined under a stereomicroscope (x 25) and extent of microleakage (mm) was recorded using an image analysis system. Data was analyzed by non-parametric statistical tests. RESULTS: No leakage was observed at the occlusal enamel margin of a nyrestoration. Median gingival leakage values for the different test groups ranged from 0.02-2.51 mm. Light unit type had a highly significant effect on leakage (P=0.0002). The highest leakage scores were recorded with the plasma arc light used in standard curing mode and the lowest with the halogen light in turbo-boost mode.

Acid Etching, Dental↗