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Biomedical subjects

W W Chee

Publications and source records attributed to W W Chee.

At least 19 recordsLinked to original sources
PubMed1995

Tensile bond strength of polyvinyl siloxane impressions bonded to a custom tray as a function of drying time: Part I.

Time-dependent bond strength studies of two polyvinyl siloxane impression materials to acrylic resin disks with their respective adhesives were studied to determine the optimal time for maximum bond strength. Six groups were tested with varying adhesive dry times of 0, 7, 15, and 60 minutes and 8 and 24 hours before testing. The results indicated that the bond strength of the adhesive increased at least twofold from time zero to 7 minutes adhesive dry time and peaked at 60 minutes for one of the materials and at 8 hours for the other. Bond strengths increased rapidly to the 15-minute test interval and then seemed to plateau. Both materials exhibited decreased adhesive bond strengths at 24 hours.

Acrylic Resins↗
PubMed1995

Efficient soldering index materials for fixed partial dentures and implant substructures.

Multiple-unit fixed partial dentures routinely require an intraoral index to ensure accurate fit. One of the most commonly used materials is Duralay acrylic resin, which has yielded satisfactory clinical results, but one disadvantage has been a prolonged setting time. This study compared the setting times of two autopolymerizing resins, Duralay and G. C. Pattern resin. The dimensional accuracy of these materials was also compared with one light-cured resin, G.C. Unifast light-cure resin. All three materials were suitable to relate castings with clinically acceptable outcomes, and chairside time could be saved with the use of recently introduced indexing materials.

Dental Abutments↗
PubMed1995

Treatment planning and soft tissue management for optimal implant aesthetics.

Aesthetic restoration of single anterior teeth is one of the most difficult procedures to execute. This article discusses patient selection criteria, implant position and its relationship to the aesthetic outcome. The importance of soft tissue management in all phases of surgical and restorative phases is emphasized. Guidelines are given for the successful delivery of this service for the patient that will preserve adjacent teeth and fulfill functional and aesthetic needs.

Dental Implantation, Endosseous↗
PubMed1994

Development of implant soft tissue emergence profile: a technique.

Despite successful osseointegration of dental implants, patients can be dissatisfied with the definitive restoration because of a poor esthetic result. An esthetic implant restoration depends on correct implant placement and a well-designed and fabricated prosthesis that includes the prosthetic teeth and the surrounding whether it is acrylic resin or soft tissue. This article describes a technique to help predict, develop, and evaluate implant prostheses and their soft tissue contours at the provisional restoration stage. This technique records the planned and subsequently proven contours, which are then used to guide fabrication of the final prosthesis and produce a predictable esthetic result.

Dental Abutments↗
PubMed1993

Use of radicular attachments with endodontically treated teeth.

An extension of conventional overdenture philosophy with the use of radicular attachments in endodontically treated teeth can be used to improve stability, reduce bony resorption and proprioception and augment retention. However, radicular attachments are not appropriate in all cases. Indications, requirements, advantages and disadvantages of this type of prosthesis are provided.

Dental Prosthesis Design↗
PubMed1992

Polyvinyl siloxane impression materials: a review of properties and techniques.

Polyvinyl siloxane impression materials have been shown to have excellent properties as impression materials; however, they are sensitive to manipulative variables. Several methods of using very high viscosity (putty) materials to form "trays" to obtain uniform bulk of the wash impression are described, and the disadvantages of each of these techniques is pointed out. It is recommended that for best results acrylic resin custom trays should be used routinely. The interaction of polyvinyl siloxane materials with latex products is also discussed and problems that this inhibition can cause are stated. Suggestions to avoid this interaction are outlined. One of the disadvantages of the impression materials is that it has a relatively short working time. Refrigerating the material will increase working time without affecting accuracy.

Acrylic Resins↗
PubMed1991

Indirect inhibition of polymerization of a polyvinyl siloxane impression material: a case report.

The inhibition of polymerization of polyvinyl siloxane impression materials by direct contact with latex gloves has been well documented. Indirect intraoral inhibition of polymerization that results from contact of oral tissues with latex gloves during tooth preparation and gingival retraction procedures has been reported. This case report illustrates the problems that can occur when the dentist used polyvinyl siloxane impression materials while wearing latex gloves. In the reported case, the inhibition is severe and obvious; in most situations the inhibition of polymerization is more subtle and is frequently undetected. Clinicians must be aware of this potential problem and the solution to it.

Dental Impression Materials↗
PubMed1988

The effect of vacuum-mixed autopolymerizing acrylic resins on porosity and transverse strength.

Three brands of autopolymerizing acrylic resin were mixed and polymerized three different ways and tested for transverse strength and porosity. The procedures tested were bench-curing at ambient temperatures, vacuuming the mix before bench-curing, and curing in a pressure device. The data indicate that both vacuuming the mix and pressure-curing are successful in reducing porosity and increasing transverse strength. These improved properties would be valuable in the fabrication of provisional restorations and occlusal splints. The following conclusions can be drawn: 1. Use of a pressure device decreases porosity and increases the transverse strength in samples of autopolymerizing acrylic resin. 2. Use of a vacuum device on the mixed acrylic resin works as well as pressure polymerizing. 3. Use of either technique is indicated to improve the quality and longevity of autopolymerizing acrylic resin restorations, orthodontic appliances, and occlusal splints.

Chemical Phenomena↗
PubMed1988

Effect of chilled monomer on working time and transverse strength of three autopolymerizing acrylic resins.

Samples of three commercially available poly(methyl-methacrylate) autopolymerizing resins were made by using room temperature and chilled monomer. Working and setting times and transverse strengths were determined. The following conclusions can be drawn: 1. Working and setting times increased approximately 2 to 4 minutes when chilled monomer was used. This could be advantageous in certain situations. 2. Transverse strength decreased approximately 17% with the use of chilled monomer. The clinical significance of this decrease is not known.

Chemical Phenomena↗
PubMedDate not supplied

Preliminary investigation of a disinfected gypsum die stone.

The setting time, comprehensive strength, diametral tensile strength, expansion, and fine detail reproduction of disinfectant-containing die stones (Steri-Die A and Steri-Die B) were compared to two commonly used die materials (Vel-Mix and Die-Keen). Six samples of each die material were formed from polysulfide rubber, condensation silicone, polyether, and poly(vinyl siloxane) impression materials. The disinfected die stones compared favorably to the controls in all tests with the following exceptions: Steri-Die B was weaker in both compressive and tensile strength and deficient in detail reproduction, especially with condensation polymerizing silicone.

Calcium Sulfate↗