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Biomedical subjects

M H Reisbick

Publications and source records attributed to M H Reisbick.

At least 19 recordsLinked to original sources
PubMed1997

Color and translucency changes during and after curing of esthetic restorative materials.

OBJECTIVES: This study was conducted to evaluate various types of contemporary resin composites and glass ionomer restorative materials for color differences that occur during light curing and after submersion in water. Additionally, translucency was evaluated through the use of a translucency parameter for each of these materials at these times. METHODS: A translucency parameter was calculated from observed colors of 2 mm thick layers of light, medium and dark shades of popular restorative materials on black and white backings. The colors of these materials were also calculated, based on Kubelka-Munk theory, for layers on a B2 shade backing. Repeated measures analyses of variance were used to identify statistically significant factors for color differences and translucency parameters. RESULTS: A statistically significant interaction was found between the products, shades and time intervals or times studied for both color difference and translucency parameter. There is relatively high variability in both lightness and translucency changes among these popular products, with some products increasing and others decreasing in these parameters with curing and subsequent water submersion. SIGNIFICANCE: Kubelka-Munk theory can be used to calculate the color of a layer of material on a backing other than those used to determine the Kubelka-Munk coefficients, thereby increasing the efficiency of research into the optical properties of esthetic restorative materials. The relatively large optical changes which occur as popular esthetic restorative materials are cured and subsequently submersed in water indicate that these changes should be taken into account during any initial clinical appearance match at placement of the unset material.

Analysis of Variance↗
PubMed1993

A comparison of an accelerated technique for casting post-and-core restorations with conventional techniques.

PURPOSE: This project compares an accelerated technique for the casting of post-and-core restorations with four traditional techniques. The accelerated technique uses two phosphate-bonded investments and the traditional techniques use a gypsum- and a phosphate-bonded investment. The study measures and compares the differences between the seating of the casting and the seating of the acrylic resin pattern. The effects of the techniques on the fit of castings with and without a ferrule are also compared. MATERIALS AND METHODS: Six groups of 10 castings were made from plastic patterns formed on a stainless steel test die. A different investment and/or burnout method was used for each group. Each group had two subgroups: ferruled and nonferruled. The fit of the plastic patterns was measured at two time intervals after forming, 2 weeks and 3 months. The patterns were invested immediately after the 3-month measurement, and the difference in fit of the castings was calculated. An ANOVA and Tuckey-Kramer test were done to determine the statistical validity. RESULTS: The seating of the patterns after 3 months of storage was consistently worse than the 2-week measurements of fit. The ferrule and nonferrule patterns were not statistically different in seating. Measurement of the castings showed that the ferruled castings seated significantly worse than the nonferrule castings. The difference in the seating of the castings as compared with the patterns was considered clinically unacceptable, showing a range of 0.301 mm to 0.528 mm. The nonferrule castings showed a significant difference in seating among groups. The difference ranged from -0.099 mm to 0.322 mm. CONCLUSIONS: The castings of the ferrule subgroups were considered clinically unacceptable and were not analyzed for significance. Among the nonferrule castings, the group using a gypsum investment and conventional technique for investing and burnout but no ring liner showed the best seating. The accelerated technique was intermediate in seating with a difference of 0.148 mm from the seating of the patterns. This group was significantly different from the two best groups but not from the remaining three groups.

Analysis of Variance↗
PubMed1992

Cement luting thickness beneath porcelain veneers made on platinum foil.

Porcelain laminate veneers were made using a platinum foil matrix and were subsequently cemented to mandibular anterior Cymel teeth. Cement film thickness was measured in six predetermined locations. Repeated measures analysis of variance and single degree of freedom contrasts delineated a significant difference between marginal openings at the incisal edge where foil is folded and in four of the other vertical areas (132 versus 74.1 microns). Marginal cement film thickness of veneers made on platinum foil is less than that reported for veneers made on a refractory investment.

Analysis of Variance↗
PubMed1990

Prosthetic and surgical management of osteogenic sarcoma of the maxilla.

Maxillary surgical defects resulting from resection of oral neoplasms vary in size from small perforations of the hard and soft palate to complete removal of these structures. Osteogenic sarcoma is of unknown etiology and is a rapidly growing tumor that may produce pain, paresthesia, and anesthesia. The recommended treatment of radical resection often results in defects that produce significant orofacial disfigurement. These defects, regardless of size, present significant functional disability, with compromised esthetics, mastication, and deglutition. Restoration with a maxillary obturator prosthesis can reestablish the physical separation between oral and nasal cavities and, in soft palate defects, enable normal palatopharyngeal function. Most patients can be rehabilitated successfully with restoration of speech and swallowing to normal levels and significant improvement in appearance.

Deglutition Disorders↗
PubMed1990

Occlusal accuracy of casts made and articulated differently.

This study evaluated the occlusal accuracy of gypsum casts constructed from irreversible hydrocolloid and selected nonaqueous elastomeric materials. Master metal casts were attached to a vertically moving apparatus that allowed their occlusal surfaces to produce repeatable contacts. Impressions were made with irreversible hydrocolloid, polysulfide, and vinylsiloxane. Resulting maxillary casts were mounted with a constant positioning device and mandibular casts were mounted with zinc oxide-eugenol paste records or by maximum intercuspation. Four specific master occlusal contacts were compared with contacts generated from the mounted gypsum casts; a perfect score was 40 (four contacts x 10 casts). A chi-square linear model for category data was used to compare groups. Results indicated that casts made from irreversible hydrocolloid should not be articulated with the use of a zinc oxide-eugenol paste but are best articulated by using maximum intercuspation (32/40 contacts).

Chi-Square Distribution↗
PubMed1988

The effects of a liquid dispersing agent and a microcrystalline additive on the physical properties of type IV gypsum.

This study evaluated the effects of a liquid dispersing agent (LDA) and a microcrystalline additive (MCA) on selected physical properties of type IV gypsum. Working consistency, setting time, setting expansion, and compressive strength (1 hour and 7 days) were determined, following ADA Specification No. 25, on a standard, LDA (0.5, 1, 1.5, and 2 mL), MCA (21.1, 24.1, and 27.1 gm), and combination (LDA 0.75 mL + MCA 12.05 gm) mixes per 300 gm of gypsum. Results indicate that the additives affect the consistency of the mix, but consistency can be kept close to that of the standard by lowering the water/powder ratio. Statistical analysis of the data indicated that the additives significantly affected the setting time, setting expansion, and both the 1-hour and the 7-day compressive strengths. SEM examination of fractured surfaces of test mixes indicated improved crystal packing. The properties of type IV gypsum can be improved by optimizing the amount of LDA and MCA additives.

Calcium Sulfate↗
PubMed1985

Precious and noble-based casting alloys.

Some medium-gold and midrange gold alloys are satisfactory substitutes for Type III alloys, but tarnish may occur. Considering all factors, Type III alloys remain unparalleled as fixed restorative alloys. Some medium-gold and midrange gold metal-ceramic alloys are superior to their high-gold counterparts and are the choice for metal-ceramic restorations.

Biocompatible Materials↗
PubMed1982

Measurement of paint-on die spacers used for casting relief.

Three paints used for die spacing were measured for film thickness. Two of the materials are marketed as die spacers, and the third is sold as a model airplane paint. The materials were applied to stone dies in multiple coats. They were embedded in resin, sectioned, and measured photographically through a microscope. The three die spacing materials were capable of achieving clinically acceptable relief in the range of 20 to 40 mu by using a variable number of coats. Different paints produced different thicknesses. The two paints sold specifically for die spacing gave 11 to 13 mu per coat. The hobby shop paint had the smallest film thickness per coat, yielding approximately 5 mu per layer. It also had the smallest standard deviation. This control plus the relative low cost and availabilty make it attractive for this purpose.

Cementation↗
PubMed1982

Post-ceramic soldering of various alloys.

A base metal alloy was soldered to precious and semiprecious alloys using a post-ceramic soldering technique. The specimens were tested by the tensile mode and the results statistically analyzed. The solder joints involving the base metal had strengths comparable to the precious and semiprecious joints. However, a high percentage of the base metal joints were too weak to be tested. Further study using other solders is indicated.

Dental Alloys↗
PubMed1980

An investigation of epoxy resin dies.

1. Complete crown epoxy resin dies are undersized. 2. MOD onlay epoxy resin dies are accurate. 3. Detail duplication of epoxy resin dies is comparable to that of die stone. 4. Hardness values of epoxy resin are generally less than those of die stone. The hardness of Epoxydent closely approached that of die stone.

Calcium Sulfate↗