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Biomedical subjects

G L Polyzois

Publications and source records attributed to G L Polyzois.

At least 55 records · Page 3Linked to original sources
PubMed1986

Dimensional accuracy of duplicate dentures prepared by different methods.

The production of a duplicate denture demands a high degree of perfection to maintain dimensional accuracy of the duplicate denture. Duplicate dentures were made by four methods in order to investigate the dimensional accuracy in relation to a master denture. Replicas made from modeling wax (all-wax replica or acrylic resin base-wax teeth replica) demonstrated better dimensional accuracy compared with the all-acrylic resin replicas. It is well known that modeling wax used alone as a temporary denture base is an unsatisfactory material. The inherent shortcomings of the material may be overcome if dentists and patients make their assessment of the duplicate as quickly as possible in the mouth. The other alternative may be the production of a duplicate denture with an acrylic resin base and modeling wax teeth.

Acrylic Resins↗
PubMed1985

Stability of some soluble alginate solutions.

The stability of some water alginates against bacterial degradation was studied. The study was based on viscosity and pH measurements of some typical alginate solutions, containing suitable additives during an extended time period (222 days).

Alginates↗
PubMedDate not supplied

Bond strength of double-sided adhesive tapes used for facial prostheses.

This study evaluated the tensile bond strengths of five silicone facial elastomers to human skin by use of five different double-sided adhesive tapes. Discs of silicone elastomers were fixed in circular metal holders and glued to the inner aspect of a forearm with the various adhesive tapes. The specimens were pulled off 20 seconds after fixation by means of a universal testing machine at a cross-head speed of 1 mm/min. Eight specimens of each silicone/tape combination were tested. Significant differences were observed among the various silicone/tape combinations. MDX4-4210 and Cosmesil facial elastomers had the strongest bond to skin with the majority of adhesive tapes, whereas Silskin II, Cosmesil HC2, and RS 330T-RTV were the weakest. After the bond failure, tapes remained adhered to the skin and not to the silicone specimens.

Adhesiveness↗
PubMedDate not supplied

Color stability of visible light-cured, hard direct denture reliners: an in vitro investigation.

PURPOSE: Previous studies have disclosed the unsatisfactory color stability of autopolymerizing, hard direct denture reliners (HDDR). The present study investigated the color stability of the newly introduced visible light-cured and dual-cured HDDRs. MATERIALS AND METHODS: Five HDDRs were evaluated after 1 hour, 1 day, 7 days, and 30 days of immersion in coffee, tea, and water. Color measurements were obtained with a tristimulus colorimeter, and color differences (delta E*) were calculated. RESULTS: After 30 days of immersion one visible light-cured material exhibited the highest delta E* value (17.8). The other materials showed acceptable color stability in water and coffee. However, tea strongly affected their color. CONCLUSION: Reliners, staining solutions, and immersion time are significant factors that affect color stability. After 7 days of immersion, all of the materials showed perceptible color differences. Tea exhibited higher staining capacity than coffee.

Analysis of Variance↗
PubMedDate not supplied

Mechanical properties of 2 new addition-vulcanizing silicone prosthetic elastomers.

PURPOSE: This study evaluated some mechanical properties of 2 newly introduced, addition-type silicone prosthetic elastomers (Cosmesil and Episil). MATERIALS AND METHODS: The properties evaluated were tensile strength, modulus at 100% elongation, elongation at break, tear strength, and hardness. The properties tested were selected because of their clinical significance for fabricating facial prostheses. RESULTS: Episil showed greater tensile strength (P = 0.0002), elastic modulus (P = 0.0001), hardness (P = 0.0002), and tear strength (P = 0.0004) than Cosmesil material. Cosmesil exhibited a higher elongation at break (P = 0.0002) than Episil. CONCLUSION: Cosmesil and Episil showed reasonable properties as facial prosthetic elastomers and neither was superior for all properties tested. Both materials showed favorable combinations of elongation at break and tear strength.

Elasticity↗
PubMedDate not supplied

Roughness of denture materials: a comparative study.

PURPOSE: Surface properties of denture materials are of clinical importance since they may affect plaque accumulation and staining. This in vitro study investigated the roughness of 20 commercially available denture materials. MATERIALS AND METHODS: Four denture base resins, nine hard lining materials, and seven soft denture lining materials were evaluated for roughness. Roughness measurements were made using a Mitutoyo Surftest SV-400, and the mean arithmetic roughness values (Ra) obtained were used for the comparisons. RESULTS: The overall Ra values ranged from 0.7 to 7.6 microns. The denture base materials group exhibited Ra values from 3.4 to 7.6 microns, whereas the hard liners were from 0.7 to 4.4 microns. The autopolymerized and visible light-cured soft liners presented Ra values from 0.7 to 3.5 microns, while the heat-cured soft liners ranged from 3.5 to 4.0 microns. CONCLUSION: The roughness exhibited by all of the materials tested (Ra values greater than 0.7 micron) indicates that there is a possibility for plaque accumulation, since 0.2 micron is considered the threshold below which no further bacterial adherence can be expected.

Acrylic Resins↗
PubMedDate not supplied

Curing efficiency of visible light- and dual-cured denture reliners.

PURPOSE: The purpose of this study was to evaluate the curing efficiency of 8 light- and dual-cured denture reliners. MATERIALS AND METHODS: The curing efficiency was measured with Fourier infrared micromultiple internal reflectance spectroscopy, calculating the percentage of remaining carbon double bonds on the top and bottom surfaces of each specimen immediately after exposure to the extraoral light-curing unit according to the manufacturer's instructions and after 1 week of storage in dark and dry conditions. Another group of specimens was photopolymerized initially through a denture base resin prior to the extraoral light-curing polymerization. Five specimens of each reliner were tested. RESULTS: The dual-cured reliners showed no statistically significant differences (P > 0.05) between top and bottom surfaces after immediate exposure to the light-curing unit. On the contrary, light-cured reliners revealed significant differences. The majority of the reliners showed reduction of the percentage of remaining carbon double bonds at both surfaces after 1 week of storage in dark and dry conditions. Photopolymerization of light-cured reliners through a denture base resin induced an increased amount of remaining carbon double bonds, whereas no effect was observed in dual-cured materials. CONCLUSION: Dual-cured denture liners exhibited distinct advantages over light-cured ones concerning the curing efficiency.

Acrylic Resins↗
PubMedDate not supplied

Wettability of visible light-curing denture lining materials.

PURPOSE: Wetting characteristics of denture lining materials indicate the degree of salivary lubricating effect, which promotes denture retention and patient comfort. This in vitro study investigated the wettability of ten commercially available visible light-cured denture lining materials. MATERIALS AND METHODS: Ten soft and hard visible light-curing materials, one autopolymerized hard lining material, and one autopolymerized denture base material were evaluated for wettability. Wettability was estimated by measuring the equilibrium and hysteresis contact angles using the dynamic contact angle analysis, or Wilhelmy, technique. RESULTS: The equilibrium contact angle ranged from 59.9 to 77.3 degrees, and contact angle hysteresis ranged from 14.7 to 30.6 degrees. CONCLUSION: Visible light-curing lining materials exhibit wetting properties similar to the conventional hard lining and denture base materials.

Acrylic Resins↗
PubMedDate not supplied

The effect of bonding agents on the bond strengths of facial silicone elastomers to a visible light-activated resin.

Three bonding agents were evaluated to determine their effect on the strength of the bond when Silskin II and Cosmesil SM4 silicone facial elastomers were polymerized to a light-activated denture resin. A silane bonding agent proved to be superior, whereas a light-activated bonding agent had inferior bonding characteristics. Intensive heat aging had no significant effect on bond strength.

Acrylic Resins↗
PubMedDate not supplied

Resilient acrylic resin template for facial prostheses.

Clay or wax is used extensively as a modeling material for trial facial prostheses. This article describes a technique that uses a resilient acrylic resin as a matrix to lodge the ocular component and wax as the sculpturing medium for orbital prostheses. The technique can be adapted and used for all facial prostheses.

Acrylic Resins↗