Biomedical subjects

S N White

Publications and source records attributed to S N White.

8 recordsLinked to original sources

PubMed1992

The effect of adhesive luting agent-dentinal surface interactions on film thickness.

This study investigated the effect of luting agent-dentinal surface interactions on the film thicknesses of new adhesive luting agents. The method was in compliance with American National Standards Institution/American Dental Association (ADA) Specification No. 8 for zinc phosphate cement. In the control groups the luting agents were placed between two glass plates, as described in ADA Specification No. 8, but in the test groups the luting agents were positioned between a glass and a dentinal plate. The materials selected were zinc phosphate cement, glass ionomer cement, polycarboxylate cement, and a resinous cement with a dentinal bonding agent. A two-way analysis of variance was performed, and t tests were computed to compare glass with the dentinal plate within each material. Zinc phosphate and glass ionomer cements exhibited a significant decrease in film thickness when measured in contact with dentin, as compared with contact with the glass plate. However, polycarboxylate cement and the resinous cement with its dentin bonding agent showed a slight nonsignificant increase when contacting dentin, as compared with the glass plate. An explanation was offered and suggestions were made regarding future research.

Adhesives↗

PubMed1992

Effect of seating force on film thickness of new adhesive luting agents.

This study examined the effect of seating force on the film thickness of new adhesive luting agents. The method was in compliance with American National Standards/American Dental Association Specification No. 8 for zinc phosphate cement. The materials tested were zinc phosphate cement, glass ionomer cement, polycarboxylate cement, and a resinous cement with a dentinal bonding agent. All materials were manipulated exactly as described in the manufacturer's instructions, and an electronic gauge with an accuracy of 0.5 micron was used. Each class of material was measured 10 times at six different seating forces. Analysis of variance and multiple comparisons testing disclosed that the seating force and class of material strongly influenced the film thicknesses of luting agents. A mathematical model describing the response of zinc phosphate cement within the range tested was reported.

Analysis of Variance↗

PubMed1992

Microleakage of new crown and fixed partial denture luting agents.

This study measured the in vitro microleakage of conventional and new FPD luting agents. Standardized preparations were made on 42 freshly extracted premolars. Facial and lingual chamfer margins were placed in enamel, mesial and distal in dentin and cementum, and castings were made in Rexillium III alloy and were then cemented with a standardized technique. Six groups of seven samples were tested, (1) polycarboxylate, (2) zinc phosphate, (3) glass ionomer, (4) Den-Mat Thin Film cement, (5) Panavia Ex, and (6) Den-Mat Thin Film cement with Tenure. The ranking of groups for stain ingress was from the greatest (1) to the least (6). A one-way analysis of variance and Tukey-Student range analysis revealed significantly similar groups, p less than 0.05:(1,2,3,4) (5,6).

Adhesives↗

PubMed1992

Framework design for bone-anchored fixed prostheses.

Fixed implant-supported restorations for edentulous patients provide excellent function, but can often be difficult to maintain. Design considerations are important to enable the patient to maintain optimal oral hygiene while complementing and enhancing the structural integrity of the prosthesis.

Acrylic Resins↗

PubMed1992

Film thickness of new adhesive luting agents.

This study determined and compared the film thicknesses of new adhesive luting agents. The method was in compliance with American National Standards Institution/American Dental Association (ADA) Specification No. 8 for zinc phosphate cement. Each of the 20 materials tested was manipulated exactly as described in the manufacturers' instructions. An electronic gauge with an accuracy of 0.5 micron was recalibrated after each recording, and each luting agent was measured 10 times. The mean film thickness and standard deviation were calculated for each luting agent; an analysis of variance and a multiple comparison test were also performed. Nine materials satisfied the ADA type I specification for film thicknesses less than 25 microns, and these included a hydroxyapatite cement, glass ionomer cements, zinc phosphate cements, and polycarboxylate cements. Five other materials met the ADA type II specification for film thicknesses of less than 40 microns, and these included a glass ionomer cement, a resinous cement, a zinc phosphate cement, and glass ionomer-resinous hybrids. Six resinous cements recorded film thicknesses greater than 40 microns, and suggestions were made regarding future development and research.

Adhesives↗

PubMed1992

The effect of ion strengthening time/temperature kinetics on the flexural strength of feldspathic porcelains.

The kinetics of ion exchange strengthening of three feldspathic porcelains were investigated. Data describing the effects of treatment time and temperature on flexural strength were produced. The temperature effect results support the hypothesis that the opposing phenomena of diffusion and relaxation control residual stress. The time effect results suggest that Fick's Law of diffusion and diffusional creep control flexural strength. Mechanisms were proposed. These findings suggest that precise control of temperature is more critical than control of time in this process of ion strengthening. Further investigations on the ion strengthening of low-fusing porcelains should be carried out.

Analysis of Variance↗

PubMedDate not supplied

In vitro microleakage of dentin adhesives.

This in vitro study measured the microleakage of current dentin bonding agents and glass-ionomer bases. Freshly extracted human molars were prepared to a flat surface, and dentin adhesives and composite resins were applied in a plastic matrix. Samples were stored in water at 37 degrees C, thermocycled, stained with AgNO3, embedded in epoxy resin, and sectioned for evaluation of stain penetration at the composite resin/tooth interface. The reliability index of the dentin adhesives varied significantly between materials. The enamel control had essentially no microleakage, and the aluminum oxalate dentin adhesive on dentin had significantly less microleakage than other dentin adhesives tested. Present dentin adhesives were unable to prevent, but may reduce, microleakage.

Acrylic Resins↗

PubMedDate not supplied

Improved marginal seating of cast restorations using a silicone disclosing medium.

This study was conducted to determine the effectiveness of a silicone disclosing medium, G-C Fit-Checker, as an aid in the improvement of marginal integrity. Standardized preparations were made on 42 freshly extracted premolars. Base metal alloy castings were finished externally and initially adjusted internally. The castings were placed on their respective teeth and the marginal opening was determined. They were then adjusted twice using the silicone material and remeasured. The preadjustment mean marginal opening was 92 microns and the postadjustment measurement 55 microns, yielding a mean reduction of 37 microns (SEM 3 microns) or 39%.

Bicuspid↗