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At least 127 records · Page 7Linked to original sources
PubMed1989

[Antibacterial actions of denture base resin on oral bacteria].

Antibacterial action of various denture base resins on thirteen species of bacteria were studied in vitro. Antibacterial effect of 5% tannin-fluoride preparation, 5% tannic acid and 5% chlorhexidine added to resins on these thirteen bacterial species were also investigated using heat-curing denture base resins. Fresh microwave-curing resin and pour-type resin each showed an antibacterial action on one bacterial strain. Fresh self-curing resins had antibacterial actions on several bacterial strains. However, after storage in water at 37 degrees C for one week, antibacterial action of microwave-curing and pour-type resin were diminished and self-curing resins partially lost their antibacterial actions. Denture base resin containing tannin-fluoride preparation or tannic acid showed an antibacterial effect on one bacterial strain. On the other hand, denture base resin containing chlorhexidine had an antibacterial action on eleven bacterial strains. However, color and mechanical properties of the drug-containing resins were not satisfactory.

Bacteria↗
PubMedDate not supplied

Assessment of shear bond strength between three denture reline materials and a denture base acrylic resin.

PURPOSE: This study reports the effect of five surface treatments on the bond strength established between three denture reline materials and a denture base resin. MATERIALS AND METHODS: Cylindric columns of denture reline materials were bonded to columns of denture base resins that received one of the surface treatments: application of dichloromethane, the monomer of the denture base resin, the recommended bonding agent or the monomer of the denture reline material, polishing with 240-grit silicone carbide paper, and air abrasion. A control group without surface treatment was included for each material. Specimens were immersed in water for 1 day and then thermocycled. The strength at which the bond failed under shear was recorded. RESULTS: None of the surface treatments significantly improved the bond strength of Kooliner. Triad bonding agent and denture base monomer applications most significantly improved the bond strengths of Triad and GC reline, respectively. CONCLUSION: Triad bonding agent and denture base monomer should be used in conjunction with Triad and GC reline, respectively, when relining a denture base resin.

Acrylic Resins↗
PubMed1975

Studies on mechanical properties of denture base material laminated with organic fiber reinforced plastics. Part I. Basic consideration of hybrid construction.

Acrylic resin is widely used as a denture base material, but the upper complete denture fails often during use. Therefore, the denture base made from acrylic resin should be reinforced in some way. Therefore, as a new method of reinforcement on the denture base, the authors devised a method to improve the strength and rigidity by laminating the palatal surface of the denture base with an organic fiber reinforced plastic, the so-called canapé construction. In this paper, as the basic experiment, the flexural strength, fatigue strength and the modulus of elasticity in bending of reinforced acrylic resin by the canapé construction were investigated. As the results, the flexural and fatigue strength are improved respectively 160% and 130% compared to the denture base acrylic resin. And the modulus of elasticity in bending is improved 80%. Therefore, it is considered that this new combination of materials using the canapé construction might be sufficiently applied to the denture base.

Acrylic Resins↗
PubMed1992

Longitudinal study on torque transmitted from a denture base to abutment tooth of a distal extension removable partial denture with circumferential clasps.

Not only forces but also torque exerted on abutment teeth are important factors for planning the construction of distal extension removable partial dentures. The purpose of this study was to make longitudinal analysis of torque transmitted from denture base to a direct abutment tooth of these dentures with circumferential clasps. The results are summarized as follows: (i) Vertical Max. MT (maximal mean value of torque) was decreased and became constant after one or one and half months of the insertion of new dentures. (ii) Lateral Max. MT in one subject was changed from the lingual direction to the buccal direction while in another subject it was constant. (iii) In the vertical direction, there were no remarkable differences of Max. MT and Ave. T (average value of torque) between subjects. Max. MT was 5-10 x 10(-3) kgm-1 in the downward. Ave. T was 2-3 x 10(-3) kgm ss-1 in the downward and 0.3 x 10(-3) kgm ss-1 in the upward. (iv) In the lateral direction, there were considerable differences of Max. MT and Ave. T between subjects. Max. MT was less than 20 x 10(-3) kgm. Ave. MT was 2-8 x 10(-3) kgm ss-1.

Aged↗
PubMedDate not supplied

Dimensional accuracy of two denture base processing methods.

The mucosal surfaces of maxillary complete dentures processed using the SR-Ivocap injection technique and the Lucitone heat-polymerized compression molding technique were compared to a metal master impression to determine if one method of denture processing produced a more accurate denture base. Comparisons were made before and after polishing the prepared bases to determine if changes occur as a result of this procedure. The dental comparator, described by Rupp and others in 1957, was used to compare selected points on the palatal surface of the denture bases. No statistical differences were found in the accuracy of the denture bases processed using either of the two techniques.

Dental Casting Technique↗
PubMed1978

Effect of the curing cycle on some properties of a polymethylmethacrylate denture base material.

The properties of a denture base material may be modified by altering both the temperature and the time of heating during the curing cycle. In this study a polymethylmethacrylate denture base containing no crosslinking agent was polymerised using four different curing cycles. The structure of the materials so obtained was investigated by an acid etching technique. The materials were characterized with respect to degree of cure, strength and water sorption. It was concluded that: 1. No correlation was observed between the curing cycles and polymer structure. 2. The curing cycle of 7 h at 70 degrees C plus 1 h at 100 degrees C produced best indentation strength and tensile strength. 3. A correlation was observed between residual monomer, indentation resistance, tensile strength and water sorption. This suggested that residual monomer concentration is the most important parameter in the determination of the properties of the material investigated in this study.

Chemical Phenomena↗
PubMedDate not supplied

The flexural strengths of denture base acrylic resins after relining with a visible-light-activated material.

PURPOSE: Previous studies disclosed the ability of a light-activated denture reline material to strengthen a particular denture base material. The present study investigated the ability of the reline material to strengthen denture base materials processed by other means. MATERIALS AND METHODS: Four denture base materials were tested for flexural strength at proportional limit (FSpl) with or without being relined. RESULTS: The reline material maintained the FSpl of the microwave-processed and the autopolymerizing denture base materials. It increased the FSpl of the heat-processed and the light-activated denture base materials. CONCLUSION: the light-cured reline material increased the flexural strengths of the heat-processed and the light-activated denture base materials and maintained those of the microwave-processed and the autopolymerizing denture base materials.

Acrylic Resins↗
PubMed2005

Minimization of the inevitable residual monomer in denture base acrylic.

OBJECTIVES: Residual monomer ([MMA](R)) in denture base acrylic continues to be of concern. The response surface of concentration vs. time and temperature for the equilibration of methyl methacrylate (MMA) and its polymer (PMMA) allows a prediction of the time to the minimum at any temperature for a closed system. It was the purpose here to determine whether this prediction applies to normal denture base processing, and whether optimum conditions could be identified. METHODS: Denture bases were processed following normal laboratory procedures, including pre-cure for 3 h at 70 degrees C for all tests. Commercial powder and liquid were used at either 95 or 100 degrees C, or a plain PMMA powder and the same liquid at 95 degrees C, for times ranging from 5 to 192 h. Residual MMA was determined by gas chromatography. RESULTS: [MMA](R) decreased steadily from approximately 0.25% to as low as approximately 0.07% with increasing time at temperature, but did not approach equilibrium. The rate of diffusive loss of MMA appears to exceed the rate of depolymerization. SIGNIFICANCE: Residual monomer is inevitable for all PMMA-based products no matter what the curing conditions are. However, extended time at high temperature can allow low values to be attained, and the time allowed can compensate for processing temperatures somewhat lower than the ordinarily recommended 100 degrees C. It is suggested that overnight processing at 95 degrees C should be adopted to minimize [MMA](R) and save energy. This result is of importance for work at high altitude.

Acrylic Resins↗
PubMed1989

Comparison of three- and four-point flexural strength testing of denture-base polymers.

Flexural failure of denture-base materials is considered the primary mode of clinical failure. However, there are several methods of conducting flexural tests, and none has been demonstrated to be the most appropriate. Three- and four-point bend-testing were compared, with four different dental polymers used. The values for modulus of elasticity determined by the two tests were not statistically different. However, the values for flexural strength from the three-point bend test were always greater, suggesting that that parameter is dependent on the testing procedure. Modifications to the existing denture-base material specification are suggested.

Dental Stress Analysis↗
PubMed2002

Tensile bond strength of acrylic resin denture teeth to a microwave- or heat-processed denture base.

STATEMENT OF PROBLEM: Fracture of acrylic resin prosthetic teeth from acrylic resin denture bases can be a problem for some patients. The optimal combination of acrylic resin denture tooth, denture base material, and processing method is not known. Purpose. The objective of this study was to compare the tensile bond strengths of heat- and microwave-polymerized acrylic resins among 4 types of acrylic resin denture teeth. MATERIAL AND METHODS: Heat-polymerized (Lucitone 199) and microwave-polymerized (Acron MC) acrylic resins were used. Four types of acrylic resin denture teeth (IPN, SLM, Vitapan, and SR-Orthotyp-PE) were milled to a fixed diameter according to ADA specification no. 15. Ten specimens of each tooth type were processed to each of the denture base materials according to the manufacturers' instructions. Ten additional resin control specimens without teeth also were fabricated. Specimens were thermocycled and tested for strength until fracture with a custom alignment device. Data were analyzed with analysis of variance and Duncan's multiple range test. A scanning electron microscope was used to identify adhesive and cohesive failures within debonded specimens. RESULTS: The mean force required to fracture the specimens ranged from 5.3 +/- 3.01 to 21.6 +/- 5.2 MPa for the microwave-polymerized base and 11.2 +/- 3.0 to 39.1 +/- 5.1 MPa for the heat-polymerized base. The most common failure was cohesive within the denture tooth. With each base material, Orthotyp and IPN teeth exhibited the highest bond strengths; SLM and Orthotyp bond strengths were similar. In general, heat-polymerized groups failed cohesively within the denture base resin or the tooth, and microwave-polymerized groups failed adhesively at either the ridge lap or occlusal surface of the denture tooth. CONCLUSION: Within the limitations of this study, the results suggest that the type of denture base material and denture tooth selected for use may influence the tensile bond strength of the tooth to the base. Selection of more compatible combinations of base and resin teeth may reduce the number of prosthesis fractures and resultant repairs.

Acrylic Resins↗
PubMedDate not supplied

The effect of chopped poly(methyl methacrylate) fibers on some properties of acrylic resin denture base material.

PURPOSE: The fracture of acrylic resin dentures remains an unresolved problem. Over the years, various approaches to strengthening acrylic resin have been suggested, including modifying or reinforcing the resin. The aim of this study was to investigate the effect of chopped poly(methyl methacrylate) (PMMA) fibers on some properties of acrylic resin denture base material. MATERIALS AND METHODS: PMMA in the form of fibers 0.75 mm in diameter and 5 mm in length was added to acrylic resin denture base material in various percentages to form a composite material. The influence on doughing and manipulation times and transverse strength was examined. The results were subjected to statistical analysis using a one-way analysis of variance and, where appropriate, the Scheffé test. RESULTS: The results showed that the doughing time was decreased by the addition of fibers, with the manipulation and setting times showing inconsistent changes. There was a significant difference between the materials in terms of the transverse strength. When the amount of PMMA fibers in the acrylic resin was increased, there was a decrease in the modulus of rupture and a decrease in the modulus of elasticity. The differences were shown to be statistically significant in some groups. CONCLUSION: The doughing time was decreased by the addition of fibers, while the manipulation and setting times showed inconsistent changes. The incorporation of chopped, randomly oriented PMMA fibers into acrylic resin had no advantage over the unmodified polymer in terms of strength and cannot be recommended as a reinforcing agent for acrylic resin denture base material.

Acrylic Resins↗
PubMed1985

In-office permanent denture base correction technique.

A repair compound made by mixing pink denture base acrylic resin polymer and methyl-2-cyanoacrylate makes it possible to accomplish many denture corrections permanently as in-office procedures. The resulting repairs display color stability and strength that make them virtually indistinguishable from the original denture base. All necessary materials are readily available, and time consuming laboratory processing for repairs can be avoided. This procedure is easily adapted to correct errors such as a complete denture not in centric relation due to incorrect mounting or faulty records, improper vertical dimension of occlusion, alteration of anterior tooth arrangement required to change esthetics, and a broken denture base.

Acrylic Resins↗
PubMed1995

Bond strength of permanent soft denture liners bonded to the denture base.

The purpose of this study was to characterize denture and soft liner adhesion and to determine the adhesive and/or cohesive strength of different soft tissue liners bonded to the denture base by use of a new technique. Two groups of five permanent soft liners (dry or exposed to water for 6 months) were tested by use of a tensile mode to characterize the failure characteristics of soft liners bonded to denture base resin. The method differed from previous test methods because of the specimen's ability to align axially during the test. The results indicated significant differences in the bonding of liners to the denture base, and light-cure systems exhibited the greatest amount of stress needed for failure. Low bond strength was observed when the adhesion was poor or when the cohesive strength of the soft liner was low and lead to pure adhesive or cohesive failure. When both adhesive and cohesive bonds were strong, failure occurred at high stresses. Combinations of adhesive and cohesive failures (mixed mode) were also observed in intermediate cases.

Acrylic Resins↗
PubMed1990

The bond strength of a visible light-cured reline resin to acrylic resin denture base material.

The introduction of Triad visible light-cured denture resin has led to several applications. Among them is direct intraoral relining of complete and partial dentures. This study investigated the bonding characteristics of Triad reline resin to four commonly used heat-cured denture base resins. The shear and tensile bond strengths of Triad resin and four denture base resins were determined and compared with intact tensile strengths. The findings of this study indicate that the bond strength of Triad resin to denture base resin is sufficiently high to suggest its clinical applicability.

Acrylic Resins↗
PubMed2006

[Biocompatibility test of polymethylmethacrylate denture base resin containing silver-supported antimicrobial agent STR-1 at nanometer level].

OBJECTIVE: To evaluate the biocompatibility of polymethylmethacrylate(PMMA) denture base resin containing silver-supported antimicrobial agent STR-1 of nanometer level in vitro. METHODS: According to the national standards for biological evaluation of dental materials, the cytotoxicity of denture base resin containing STR-1 at concentrations of 5 g/L and 10 g/L was examined by molecular filtrating method, and the hemolysis of STR-1, denture base resin containing STR-1 at concentrations of 5 g/L and 10 g/L was also surveyed. RESULTS: The control denture base resin without containing STR-1 and the denture base resins containing STR-1 at concentrations of 5 g/L and 10 g/L were not cytotoxic to L929 cells. Two hours and 24 hours after cell culturing, the filter membranes of the control and experimental groups were stained evenly with blue color. The staining intensity was not decreased and the fading areas were 0 mm2 during the culturing. The cytotoxicity grades were 0. The hemolysis rates of the antimicrobial agent STR-1 and the denture base resins containing STR-1 at concentrations of 5 g/L and 10 g/L were 1.7%, 3.5% and 3.7% respectively. They were less than the national guild standard 5% which represent no hemolysis. CONCLUSION: The PMMA denture base resins containing silver-supported antimicrobial agents STR-1 of nanometer level at concentrations of 5 g/L and 10 g/L exhibit good biocompatibility.

Animals↗