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At least 487 records · Page 27Linked to original sources
PubMed1989

Mechanical properties of poly(alkyl alpha-fluoroacrylate)s as denture-base materials.

alpha-Fluoro-substituted acryl polymers, poly(methyl alpha-fluoroacrylate) (PMFA) and poly(2,2,2-trifluoroethyl alpha-fluoroacrylate) (P3FFA) were investigated for extension to denture-base resins. PMFA, in which fluorine attaches to the polymer chain, had excellent mechanical properties: For instance, compressive and bending strength and bending modulus were 50% higher than those of PMMA. P3FFA, in which fluorines are substituted at the end of the pendant alkyl ester, showed poor mechanical properties. Contrary to expectations, the amount of water sorption of PMFA was about twice that of PMMA, while that of P3FFA was almost zero. Copolymers of MFA and 3FFA were prepared in an attempt to optimize the mechanical properties and the water sorption. The copolymer with 40% of 3FFA showed higher compressive, diametral tensile, and bending strength; in particular, the bending modulus and water resistance were about 35% and 20% higher, respectively, than those of PMMA. Improvement of the mechanical properties and increase of the water sorption of PMFA may be due to intermolecular forces induced by polarizability of the fluorine and carboxy group along the polymer chain. Decrease of the water sorption by fluorine substituted on the alkylester group as in P3FFA may be due to higher hydrophobicity and steric effect of the fluoroalkyl substitute.

Acrylic Resins↗
PubMed1999

Color stability of denture base acrylic resins in three food colorants.

STATEMENT OF PROBLEM: Three commonly used artificial dyes in food technology are erythrosine, tartrazine, and sunset yellow. PURPOSE: The color stability of 5 commercially available denture base acrylic resins (QC-20, Meliodent, Trevalon, Trevalon High, and Lucitone) was studied in vitro. METHODS: The specimens were exposed to 3% erythrosine, tartrazine, and sunset yellow solutions at 23 degrees C +/- 1 degrees C. Color changes were determined with a computer-controlled spectrophotometer. Five specimens from each material were processed, and initial color measurements were made after 1, 3, and 6 months of exposure to the staining solutions. Finally, the color stability was quantitatively measured again, and color differences (DeltaE) were calculated. RESULTS: For the observations made in 1, 3, and 6 months intervals, the specimens that exhibited the least color change were in the sunset yellow solution. The greatest color changes observed according to the National Bureau of Standards unit system were Lucitone (2.71) in erythrosine solution, Lucitone (2.54), QC-20 (1.71) in tartrazine solution, and QC-20 (1.66) in sunset yellow solution. The changes in the other acrylic resins in the 3 solutions were slight and at trace level. CONCLUSIONS: All materials tested were acceptable from the standpoint of color stability for long-term exposure to these food colorants.

Acrylic Resins↗
PubMed1980

Tooth movement and dimensional change of denture base materials using two investment methods.

This in vitro investigation evaluated methods of investing a maxillary denture (1) by using a silicone rubber and gypsum base covering all the artificial teeth and (2) by following the generally accepted procedure of investing in a total gypsum environment. The amount of vertical opening found in dentures processed with silicone investment was approximately the same as for those processed with the all-gypsum technique, the horizontal movement of the teeth was more lingual in the silicone investment technique. Comparing the weight of the residual impression between the denture base of acrylic resin and the master die showed no significant difference between the silicone investments and the gypsum technique. The relined denture base provided a more accurate fit than a heat-cured denture processed in both types of investment, silicone and all-gypsum. Finally, a special device was developed that permitted tooth movement in processed dentures to be measured simply and accurately.

Calcium Sulfate↗
PubMed2003

Clinical comparison between a modified light-curing denture base resin and a conventional composite resin for orthodontic bonding.

The purpose of this in vivo study was to evaluate and compare the bond failure rate of a modified visible light-cured denture base resin (Triad VLC Provisional Material; Dentsply International Inc., York, PA) with that of a conventional visible light-cured composite resin (Transbond XT; 3M/Unitek, Monrovia, CA) for the bonding of orthodontic brackets. Both adhesives were used in each patient following a split-mouth design. Thirty-five consecutive patients with fixed appliances were included in the study, and the performance of 655 stainless steel brackets was evaluated: 325 brackets were bonded with the modified Triad VLC resin and 330 were bonded with Transbond XT resin. The incidence and site of bond failures were recorded over a period of 12 months. The overall failure rate of Triad VLC (4.3%) was not significantly different (p>0.05) from that of Transbond XT (3.6%). No significant differences in the failure rates of upper and lower arches within each material or between the two materials were found (p>0.05). Transbond XT showed a significantly higher failure rate (p<0.05) in the anterior (4.8%) than in the posterior teeth (1.6%). The present findings demonstrate that Triad VLC could be used as an alternative bonding material for direct bonding of orthodontic brackets.

Acrylic Resins↗
PubMed1989

[Studies on the flow properties of autopolymerizing hard-setting resins used as direct relining materials for denture bases].

Autopolymerizing hard-setting direct relining resin is currently being used in dentistry to attain denture bases that conform to the supporting tissues with a high degree of accuracy. The purpose of this study is to investigate the flow of six commercial hard-setting direct relining resins (Denture Liner, Kooliner, New Truliner, Rebaron, Swift, Tokuso Rebase) and several types of impression materials (zinc oxide-eugenol, polysulfide rubber, silicone rubber) using the parallel plate viscometer. The viscometer is used to measure the spread radius of samples (a volume of 0.5 cm3) between two parallel flat plates when a load of 750-gram weight is applied at 1, 10, 60, 100 seconds after loading has begun. In this experiment, the load was applied at 120, 150, 180, 210, 240, 300 seconds after mixing had begun. All the samples were mixed according to the manufacturer's recommendations. The findings were as follows; 1. The flow of the six commercial hard-setting direct relining resins could be compared with one another by the spread radius at 1 second after loading (r1) with no relation to time lapse after initiation of the mix. 2. Denture Liner, Kooliner, Rebaron and Swift had the same flow characteristic when r1 was the same. 3. Polysulfide rubber impression materials had similar flow characteristic to hard-setting direct relining resins.

Acrylic Resins↗
PubMed1989

Effect of water and artificial saliva on mechanical properties of some denture-base materials.

Two artificial saliva samples selected on the basis of being chemically and physically similar to natural saliva were used as saturation media so that we could investigate their effects on mechanical properties of four denture-base materials, and the results were compared with the effect of water on the same materials. Diffusion coefficients in the more viscous saliva were different from those in water but, in general, mechanical properties were similarly affected in all liquids, indicating that the aqueous phase of the artificial medium was a major factor influencing the results.

Acrylic Resins↗
PubMed1990

[Mechanical studies on casting titanium alloy denture base].

The mechanical properties of the Akers type clasp, bar and frame made by the newly developed Ti-20Cr-0.2Si alloy were studied in order to obtain the indices for designing the cast partial denture base. In the case of the clasp, the bending strength of the Ti-20Cr-0.2Si alloy and pure Ti was lower than that of the Co-Cr alloy. The Ti-20Cr-0.2Si alloy and pure Ti may have the same retentive force as the gold type IV alloy because its bending behavior was similar to that of the gold alloy. In the cyclic bending test, the permanent deflection of the Ti-20Cr-0.2Si alloy was lower than that of the pure Ti and Co-Cr alloy. It had almost the same value as that of the gold alloy. Considering the permanent deflection and fracture, it is preferable that the undercut of the abutment tooth for the Ti-20Cr-0.02Si alloy clasp is 0.50mm or less. The Ti-20Cr-0.2Si alloy bars and frame showed the same bending behavior and strain distribution as the gold alloy. In the case of the Ti-20Cr-0.2Si alloy bar thickened about 30%, the strain was decreased and close to that of the Co-Cr alloy. It was suggested that the Ti-20Cr-0.2Si alloy bar or frame should be designed like the gold alloy.

Dental Alloys↗
PubMed1977

Biological properties of denture base resins.

The biocompatibility and clinical efficacy of dental materials have been and continue to be a major concern of the dental profession. There are some cases of dental materials that have demonstrated problems with biocompatibility, for example, silicone soft liners. Although rare, allergic stomatitis caused by denture base resin is another example. High purity, very large polymer size, and nonoccurrence in nature significantly contribute to the acceptance of polymers used as biomaterials. New Federal Food and Drug Administration law and requirements of the specification and testing program of the American Dental Association will control the biocompatibility and clinical efficacy of dental biomaterials presently available to the dental profession.

American Dental Association↗