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Biomedical subjects

S R Jefferies

Publications and source records attributed to S R Jefferies.

11 recordsLinked to original sources
PubMed1998

The art and science of abrasive finishing and polishing in restorative dentistry.

Effective use of rotary cutting burs and bonded, coated, and loose abrasives can greatly simplify and improve the effectiveness of finishing and polishing procedures. Fluted carbide finishing burs appear to be the optimal rotary contouring devices for posterior composite resins. Finishing diamonds are preferred for gross finishing of adjusted porcelain. Coated abrasive discs and strips provide unique interproximal and incisal access and are preferred for finishing and polishing of microfil resins. Rubberized bonded abrasives have evolved to provide a greater range of finishing and polishing action on composite resin and for polishing porcelain. A wide selection of aluminum oxide and diamond polishing pastes, together with highly effective felt and foam application devices, are now available to polish composite and porcelain to an enamel-like appearance. Aluminum oxide composite polishing pastes are highly effective and strongly recommended for use on highly filled hybrid composites but have limited utility on microfil resins, with use of extrafine (0.3-mu) pastes clearly contraindicated.

Aluminum Oxide↗
PubMed1997

Adherence of "stuck" restorations to demineralized dentin following use of experimental primers.

PURPOSE: This in vivo study histopathologically evaluated the biocompatibility of four self-conditioning dentinal primer formulas in four bonding systems and evaluated the pulpal responses of the self-conditioning dentinal bonding systems for Class V tooth preparations in primates. MATERIAL AND METHODS: The basic formula consisted of proprietary carboxylic diacid monomer, dipentaerythritol pentaacrylate phosphoric acid ester, acetone, and ethanol that was used alone or mixed with other commercial priming agents. After application of primers, Prisma Universal Bond 3 was selected to restore the cavity preparations. RESULTS: All systems were judged histopathologically biocompatible. "Stuck" restorations that were resistant to acid demineralization necessary for processing of histologic slides, occurred more frequently with intact smear layers and increasing use of dehydrating agents. CONCLUSIONS: Tests should be performed to determine whether "stuck" restorations in in vivo studies that maintain dentin-pulpal relationships can support in vitro shear bond strength tests.

Acetone↗
PubMed1978

L-asparaginase bound to collagen membranes: effect of glutaraldehyde crosslinking on stabilization of catalytic activity.

Reconstituted bovine collagen has been used extensively in our laboratory as a carrier for immobilized E. coli L-asparaginase. The activity and catalytic stability of these collagen-asparaginase membranes can be altered substantially by conditions used in membrane crosslinking with glutaraldehyde. As the concentration of glutaraldehyde used in tanning is increased, the initial specific activity of collagen-asparaginase membranes decreased asymptotically to a limiting value. Similar results occurred when membranes were subjected to increasing time periods of tanning at a constant glutaraldehyde concentration. These observations point to a time-concentration relationship for glutaraldehyde tanning and its effect on the specific activity of collagen-asparaginase membranes. Specific activities of membranes tanned a glutaraldehyde concentrations of 5% or higher appear to be very stable over long periods of alternate storage and assay. This result, however, is not observed with membranes tanned at glutaraldehyde concentrations lower than 5% for short periods of time (approximately 30 sec to 1 min). It is not clear whether the instability of membranes tanned at lower concentrations of glutaraldehyde or shorter intervals of tanning is due to enzyme elution from the membrane or denaturation of the bound enzyme.

Aldehydes↗
PubMed1977

Preliminary studies with L-asparaginase bound to implantable bovine collagen heterografts: a potential long-term, sustained dosage, antitumor enzyme therapy system.

In this study, L-Asparaginase has been bound to collagen heterografts derived from carotid bovine arteries. The immobilization procedure utilizes both non-covalent and covalent interactions to fix the enzyme. Binding of the enzyme to the graft material was shown to the pH dependent, with optimum binding occurring at pH 6.0 and pH 8.5. Amidohydrolysis by the bound enzyme exhibited zero-order kinetic behavior at substrate saturating conditions. Total apparent asparaginase activity expressed by the grafts as a function of the number of repeated in vitro assay trials demonstrated that over a span of 3 months of intermittent storage and use, the enzyme-grafts retained as much as 62% of their initial activities. Implantation of 4 asparaginase-collagen grafts in various locations of the thoracic and abdominal aorta resulting in prolonged reductions of plasma asparagine levels in 3 of the 4 implants. Presence of plasma asparaginase was checked in one of the four implants and determined to be less than 2 X 10(-4) I.U./ml. Removal of grafts from 3 of the 4 animal subjects showed reductions in the apparent asparaginase activity expressed by the grafts of 7 to 70 percent after in vivo contact times which varied from 6 to 15 days.

Animals↗
PubMedDate not supplied

In vitro evaluation of two new dentin adhesive systems.

Two new experimental dentin adhesive systems were evaluated to determine in vitro dentin bond strengths and marginal microleakage. Scanning electron microscopy examinations were also conducted on one of the systems that was designed to modify the smear layer. Mean shear bond strength for the two experimental systems were 6.77 +/- 1.94 MPa and 18.73 +/- 2.4 MPa. Marginal microleakage from the enamel margin was not observed and the experimental primer system limited leakage from the dentin margins. The SEM examinations showed that the primer did not significantly alter the smear layer on the prepared dentin surface.

Acid Etching, Dental↗
PubMedDate not supplied

Use of a visible light cured elastomeric resin to stabilize cervical matrix in restoration of Class V erosion lesion.

Effective moisture control and gingival retraction are essential prerequisites for success in the restoration of Class V bonded restorations. Various techniques exist for cervical isolation and moisture control in Class V restorations. This case report details a modified technique in which a visible light cured elastomeric resin was utilized to stabilize a cervical matrix in restoration of a Class V erosion lesion. The resultant customized matrix provides effective isolation, moisture control, and gingival retraction when used in conjunction with Class V restorations.

Dental Cavity Preparation↗
PubMedDate not supplied

Bond strength, microleakage, and scanning electron microscopy examination of the Prisma Universal Bond 2 adhesive system.

Dentin shear bond strength and marginal microleakage of a new primer/adhesive system were evaluated in this study and compared to Tenure Solution, Gluma, XR Primer/XR Bond, and Scotchbond 2. In addition, scanning electron microscopy examinations were conducted to evaluate the effect of the new primer on the smear layer, determine the film thickness of the primer/adhesive, and examine the resindentin interface of restorations placed with the new system.

Adhesives↗
PubMedDate not supplied

Three composite finishing systems: a multisite in vitro evaluation.

Selection of appropriate finishing and polishing devices is critical to the optimal appearance and longevity of composite resin restoratives. This report compares the effectiveness of three specific finishing and polishing systems when used to prepare the surfaces of composite restorative materials provided by the respective manufacturers. Profilometer surface roughness analyses were conducted at two separate laboratories to cross-correlate numerical smoothness data in this study. Statistically significant differences in mean surface roughness were found between various finishing system/composite resin pairings. Surprisingly, a hybrid composite resin finished and polished with its respective finishing/polishing system gave a significantly smoother surface than a microfill composite surface prepared with its corresponding sequentially coated abrasive disc system. This finding was corroborated at a second site using a separate methodology for profilometer analysis.

Analysis of Variance↗
PubMedDate not supplied

Retentive properties and film thickness of 18 luting agents and systems.

In the past, retention of castings depended on mechanical interlocking or adhesion to enamel and dentin by means of chelation in the case of some cements. Some new luting agents adhere to metal and tooth structure. The era of bonded casts for crowns and bridges has arrived through a combination of dentin primers and luting agents that bond to enamel, dentin, and precious and nonprecious metals. For a few systems, the retentive forces (in an otherwise nonretentive experimental design) more often than not exceeded tooth strength.

Analysis of Variance↗