Triad: light curing denture base system for partial dentures.
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Acrylic Resins↗
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Residual methyl methacrylate monomer, water sorption, and water solubility of hypoallergenic denture base materials.
STATEMENT OF PROBLEM: Denture base materials have the potential to cause irritation and allergic reaction to the oral mucosa. Water sorption and water solubility of denture base resins affect dimensional behavior and denture stability. A correlation between residual monomer and water sorption exists. PURPOSE: This in vitro study compared the amount of residual monomer, quantity of water sorption, and solubility of 4 denture base materials purported to be hypoallergenic with those of a polymethyl methacrylate-based (PMMA) heat-polymerizing acrylic resin. MATERIAL AND METHODS: The denture base resins Sinomer (heat-polymerized, modified methacrylate), Polyan (thermoplastic, modified methacrylate), Promysan (thermoplastic, enterephthalate-based), and Microbase (microwave polymerized, polyurethane-based), which are purported to be hypoallergenic, and Paladon 65 (heat-polymerized, methacrylate, control group) were examined. Specimens of each material were tested for residual methyl methacrylate (MMA) monomer (% wt, n=3), amount of water sorption (microg/mm3, n=5) and water solubility (microg/mm3, n=5), according to ISO 1567:2000. The residual MMA monomer concentrations were determined by gas chromatography (GC). The data were analyzed with 1-way ANOVA and the Bonferroni-Dunn multiple comparisons post hoc analysis for each test variable (alpha=.05). RESULTS: Significantly lower residual MMA monomer was shown for Sinomer and Polyan compared to the PMMA control group (0.90 +/- 0.20% wt, P<.05). Sinomer contained 0.31% +/- 0.00% wt MMA monomer, and Polyan exhibited residual MMA monomer content of 0.44% +/- 0.01% wt. Promysan and Microbase did not contain detectable residual MMA. Water sorption of Promysan (16.21 +/- 0.96 microg/mm3) was significantly lower than Paladon 65 (23.04 +/- 3.13 microg/mm3, P<.0001), whereas water solubility of the hypoallergenic denture base materials (0.34-0.84 +/- 0.05-0.09 microg/mm3) was not significantly lower than the PMMA material (0.40 +/- 0.06 microg/mm3, P>.05). Except for Sinomer, the tested denture base resins passed the requirements of ISO 1567 regarding residual MMA monomer (<2.2% wt). Sinomer failed to comply with the requirements for residual MMA monomer because the manufacturer claimed that the material did not contain any MMA. The tested denture base materials fulfilled the requirements regarding water sorption (<32 microg/mm3) and solubility (<1.6 microg/mm3). CONCLUSION: The tested hypoallergenic denture base materials exhibited significantly lower residual monomer content than PMMA. Promysan and Microbase showed no detectable residual MMA.
Absorption↗
INTERCHANGEABLE FACINGS AND PORCELAIN DENTURE BASES FOR ANTERIOR FIXED PARTIAL DENTURES.
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Dental Porcelain↗
Comparison of bond strengths of denture base resins to nickel-chromium-beryllium removable partial denture alloy.
PURPOSE: In vitro bond strengths of a traditional denture base resin (Lucitone 199) and three adhesive denture base resins (Meta-Dent, Meta-Fast with liner, and Meta-Fast without liner) to treated nickel-chromium-beryllium (Ni-Cr-Be) partial denture alloy were tested with four alloy surface pretreatments (sandblast, Met-etch, Rocatec with silane, and Rocatec without silane), with or without primer (Dentsply). The Lucitone 199 resin bonded to the nonprimed sandblasted group was the control group. The hypothesis was the use of alloy pretreatments and/or primer does not improve the bond strength of denture base resins to sandblasted Ni-Cr-Be partial denture alloy. MATERIAL AND METHODS: Primed and nonprimed bonded specimens were prepared and finished, stored in 37 degrees C distilled water for 24 hours, then debonded in tension on a testing machine. The bond strength was calculated in megapascals (MPa). Five specimens were prepared and tested for each experimental condition, both with and without primer, for a total of 160 specimens. RESULTS: For three-way analysis of variance, the main effects of resins and treatment were statistically significant (p < 0.05), but the main effect of primer was not statistically significantly (p > 0.05). Without primer, the control group had the lowest bond strength (0 MPa). The three adhesive resin groups produced significantly higher bond strengths than the Lucitone resin groups. For the treated groups, nearly all sandblasted groups produced significantly lower bond strength than the other three treated groups. Meta-Dent to Met-etch treated group had the highest bond strength (23.9 MPa). With primer, the bond strengths of the Lucitone resin groups were significantly higher than the nonprimed groups, and the Lucitone resin-primed Rocatec treated group had the highest bond strength (14.8 MPa). For the three adhesive denture base resins, nearly all primed treated groups had significantly lower bond strengths than nonprimed groups. CONCLUSIONS: Without primer, the Lucitone resin-sandblast treated group (control) had the lowest bond strength (0 MPa). The Meta-Dent denture base resin with the Met-etch treated group had the highest bond strength (23.9 MPa). With primer, the Lucitone resin-primed Rocatec-silane treated group had the highest bond strength (14.8 MPa). For the adhesive denture base resins, nearly all bond strengths of the primed treated groups were significantly lower than the values of the nonprimed groups.
Acid Etching, Dental↗
Compatibility of denture cleansers with some new self curing denture base materials.
All denture base materials are subjected to abrasion during function, but this will be greatest under certain denture cleansing regimens. Two new materials, a 'pour type' and a compression moulding acrylic resin were subjected to mechanical brushing with denture cleansers. It was found that abrasion resistance of the two materials was of the same order, and weight loss was greatest with one of the paste cleansers.
Acrylic Resins↗
A hydrophilic denture base resin.
A Denture Base Resin is marketed with hydrophilic characteristics which, it is claimed, improve retention. The claim has been questioned, but this article is concerned with the physico-chemical properties of the product.
Absorption↗
In vitro antiseptic properties of an ammonium compound combined with denture base acrylic resin.
BACKGROUND: Denture base acrylic resin is easily colonised by oral endogenous bacteria and Candida spp., and eventually by extra-oral species such as Staphylococcus spp., Pseudomonadaceae or members of Enterobacteriaceae. This microbial reservoir can be responsive for denture related stomatitis and aspiration pneumonia, a life-threatening infection especially in geriatric patients. However, the oral and denture hygiene of dependent elderly individuals is extremely poor. OBJECTIVE: This in vitro study aimed to determine the per cent of a quaternary ammonium compound heat-polymerised in acrylic resin necessary to obtain denture base displaying antiseptic properties. DESIGN: Acrylic resin discs containing 2-50% ammonium polymer (Poly 202063A; 0% control) were soaked in artificial saliva for 4 weeks. Resin discs were incubated for 24 hours with Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa [37 degrees C, brain-heart infusion (BHI) broth and phosphate-buffered saline (PBS) buffer] and Candida albicans (30 degrees C, Schaedler broth), in 15 ml (168 discs) and 600 microl (168 discs) of inoculum. Microbial growth was verified at t 0 hours and t 24 hours. Data were recorded as the mean of three colony forming unit (CFU) numerations. The borderline of antimicrobial effect was determined at 0.1% viable cells. RESULTS: In 600 microl of PBS inoculum, resin specimens had a bactericidal effect (E. coli and S. aureus: 2%; P. aeruginosa: 10%) and a fungicidal effect (C. albicans: 50%). Long-term stability and toxicity in vivo studies are now required. CONCLUSION: A 2% quaternary ammonium compound polymerised with a denture acrylic resin displayed antiseptic properties after a 4-week soaking period in artificial saliva. Such antiseptic denture base could help geriatric patients to improve their oral health.
Acrylic Resins↗
The effect of length and concentration of glass fibers on the mechanical properties of an injection- and a compression-molded denture base polymer.
STATEMENT OF PROBLEM: Fiber-reinforcement has been used to overcome the mechanical limitations of denture base polymers. One major difficulty in the use of fiber reinforcement has been the addition of fibers during conventional processing methods. PURPOSE: This study evaluated the effect of various lengths and concentrations of chopped E-glass fiber-reinforcement on the transverse strength, modulus of elasticity, and impact strength of injection and compression-molded polymethyl methacrylate based denture base polymer. MATERIALS AND METHODS: Test specimens (n=10) of 4-, 6-, and 8-mm fiber length and 1%, 3%, and 5% weight fiber concentrations were prepared with either an injection or a compression-molded processing method. Denture base polymer specimens without any fiber reinforcement were used as control for both processing methods. Transverse strength test specimens (65 x 10 x 2.5 mm) were stored in water bath at 37 degrees C for 2 weeks. The transverse strength (MPa) and modulus of elasticity (GPa) was measured with the 3-point bending test. Impact strength (kJ/m(2)) test specimens (60 x 7.5 x 4 mm) were tested with the Charpy-type pendulum impact test setup. The data were analyzed with multifactorial analysis of variance and Tukey post hoc tests (alpha=.05). RESULTS: Injection-molded fiber-reinforced groups showed significantly higher transversal strength, elastic modulus, and impact strength compared with compression-molded groups (P <.001). In the injection-molded groups, fiber concentration increased all mechanical properties tested (P <.05), but fiber length only increased transverse strength and modulus of elasticity (P <.05). In the compression molded groups, fiber concentration affected modulus of elasticity and impact strength significantly (P <.05), but fiber length did not show any significant effect on the mechanical properties tested (P >.05). CONCLUSION: The transverse strength, elastic modulus and impact strength of injection-molded denture base polymer increased significantly with the use of chopped E-glass fibers, whereas the effect was not significant with the compression-molded polymer.
Analysis of Variance↗
Evaluation of adhesion of chairside hard relining materials to denture base polymers.
STATEMENT OF PROBLEM: Removable denture bases are made of modified poly(methyl methacrylate) (PMMA), which has reliable bond strength with resins containing methyl methacrylate (MMA). However, some hard relining materials with different chemical compositions have been reported to have less than adequate bond strength to PMMA denture base polymers. PURPOSE: This in vitro study evaluated the initial bonding properties of chairside hard relining materials to different removable denture base polymers, as well as the structure of the interface. MATERIAL AND METHODS: The tensile strength (MPa) of adhesion of 8 chairside hard relining materials (Original Truliner, GC Reline Hard, Ufigel Hard, Triad Reline, New Truliner, Light Liner, Astron LC Hard, and Flexacryl Hard) was tested against 3 denture base polymers (Ivocap Plus, Paladon 65, and Palapress Vario). Dumbbell-shaped specimens with a 6-mm diameter of bonding surface were used for tensile testing of bond strength (n=5). An MMA containing hard relining material (Original Truliner) was used as a control. Tensile strength of the bond was calculated using the bonding area and maximum force under tension. Statistical analyses of data were conducted with 2-way analysis of variance (alpha=.05). The influence of the bonding agents and the relining materials on the PMMA denture base surface layer and its structure were investigated. The depths of the swollen layers were measured with a transmission light microscope. Fracture surfaces after testing were also visually evaluated. Chemical analyses of all materials prior to testing were performed using high-performance liquid chromatography. RESULTS: Significant differences were found among tensile bond strengths of chairside hard relining materials to PMMA denture base polymers forming 3 different groups (P<.001). No significant difference among different denture base polymers was found with regard to tensile strength of adhesion (P=.918), but the interaction term between hard relining material and denture base polymer was found to be significant (P<.001). The tensile bond strength of the relining materials and denture base polymers was found to range from 8% to 60% of the strength of the PMMA denture base polymers. CONCLUSION: The chemical composition of the bonding agents and the relining materials and their combinations affected the depth of the swollen layers of the denture base polymers and the tensile strength of adhesion.
Acrylic Resins↗
Effect of finishing and polishing procedures on the gap width between a denture base resin and two long-term, resilient denture liners.
STATEMENT OF PROBLEM: The junction between a long-term, resilient denture liner and the denture base is difficult to finish and polish due to differences in the hardness of the materials. Gaps tend to form during finishing and polishing procedures. PURPOSE: This study measured the junctional gap between 2 long-term, resilient denture liners and a denture base material after different finishing and polishing procedures were performed. The surface smoothness of the 2 liner materials also was evaluated. MATERIAL AND METHODS: Molloplast-B and an experimental, heat-polymerized methyl siloxane-resin-based denture liner were processed (according to the manufacturer's instructions) against Lucitone 199 acrylic resin. Control specimens (n = 20) were 2 mm thick and flat. Experimental specimens (n = 64) were fabricated with a raised center section: a 3- x 5- x 15-mm half-cylindrical ridge with a junction at the top of the cylinder between the liner material and acrylic resin. The specimens were finished with 1 of 6 types of burs and polished with different combinations of rubber-impregnated acrylic polishers, pumice, and tin oxide. The finished specimens were examined and photographed with a scanning electron microscope, and the largest gap along the liner/denture base junction on each specimen was measured. Three-way analysis of variance without replication (P<.05) and post-hoc t tests were used to analyze the data and compare groups. RESULTS; Averaged across finishing and polishing techniques, a larger gap was recorded for the experimental liner material (22 microm) than for Molloplast-B (14 microm) (P<.00005). Qualitative evaluation suggested that the experimental liner material polished better than Molloplast-B. The smoothest surfaces were obtained when specimens were finished with fine-tooth cross-cut carbide burs and polished with both pumice and tin oxide. A comparison between polished and unpolished specimens, averaged over materials and finishing techniques, revealed that polishing reduced gap size (P=.015). CONCLUSION: Within the limitations of this study, the 2 denture liners tested behaved similarly. The results suggest that the size of the gap at the liner/denture base junction may be affected by finishing and polishing techniques and vary among materials.
Acrylic Resins↗
The effect of chemical surface treatments of different denture base resins on the shear bond strength of denture repair.
STATEMENT OF PROBLEM: Fracture of a repaired denture base often occurs at the junction of the base and repair materials rather than within these materials. PURPOSE: The purpose of the study was to evaluate the shear bond strengths of 4 denture base acrylic resins following the use of 3 chemical solvents and to examine treated acrylic resin surfaces under a field emission scanning electron microscope (SEM). MATERIAL AND METHODS: Forty discs (15 mm in diameter and 3 mm thick) were fabricated for each denture base material (a conventionally molded, heat-polymerized [Meliodent, M], an injection-molded, heat-polymerized [SR-Ivocap, I], and a microwave-polymerized [Acron MC, A]) repaired with an autopolymerizing acrylic resin (Meliodent), for a total of 120 specimens, processed according to manufacturers' instructions, embedded in acrylic resin blocks, and divided into 4 groups of 10. One of the groups served as control and had no surface treatment. In the 3 experimental groups, specimen surfaces were treated with chemical etchants by immersion in acetone (ac) for 30 seconds, in methylene chloride (mc) for 30 seconds, or in MMA (mo) for 180 seconds, respectively. Then autopolymerizing acrylic resin (Meliodent) was placed on the treated surfaces using a brass ring (6 mm in diameter and 2 mm in height) to confine the material to a standardized dimension. After 24 hours of storage at 37 degrees C, the shear bond strength (MPa) of the specimens was measured in a universal testing machine. A 2-way analysis of variance and the Tukey HSD test were performed to identify significant differences (alpha=.05). The nature of the failure was noted as adhesive, cohesive, or mixed. The effect of the chemical treatments on the surface of base resins was examined under an SEM. RESULTS: Chemical treatments increased the bond strength of repair material significantly. Significant differences were found between the control and experimental groups (P<.001). In the control group, M showed the highest (16.7 MPa) bond strength, and A showed the lowest (9.4 MPa). No significant differences were detected between M (18.9 MPa) and A (19.9 MPa) with acetone treatment, or between M (19.3 MPa) and A (20.3 MPa) with methylene chloride treatment. The SEM observations showed that application of chemical etchants produced smoother surfaces than controls. CONCLUSION: Chemical treatment prior to denture base repair showed significant improvement on the bond strength of the base materials. Although the microwave-polymerized acrylic resin, A, showed the lowest shear bond strength compared to the control groups, the highest percentage increase was obtained with A after chemical treatments.
Acetone↗
Longitudinal study on forces transmitted from denture base to retainers of lower free-end saddle dentures with Aker's clasps.
The aim of this study was to make a longitudinal analysis of the forces transmitted from denture base to retainers of lower free-end saddle dentures with Aker's clasps using a newly developed transducer. The experimental apparatus consisted of two components, a metal framework and a denture base embedded with a force-detecting unit. This device was the transducer, which could detect changes in lateral and vertical forces transmitted from denture base to retainers at the same time. Forces were measured on several separate occasions from the insertion of new dentures to about 4 months afterwards. The result are summarized as follows: (i) the maximal mean value of vertical forces transmitted from denture base to retainers was decreased after 1 week of insertion of new dentures, then increased and reached a constant level (about 10N) 4-6 weeks after the insertion of new dentures; (ii) there were large differences in the maximal mean value of lateral forces between subjects.
Aged↗
[Dimensional accuracy of microwave-cured denture base resin].
Recently, microwave-cured denture base resin was developed, and the resin solved the problem of internal porosity which had been generated by curing the conventional denture base resins with microwave irradiation. In this study, the dimensional accuracy of microwave-cured denture base resin was compared with that of other denture base resins, such as pour-type resin, heat-cured resin and heat-shock resin. From the experiment, the following results were obtained. 1. Dimensional accuracy of microwave-cured denture base resin was better than that of heat-cured resin and heat-shock resin, and was similar to that of pour-type resin. 2. Dimensional accuracy of microwave-cured denture base resin by slow cooling method and rapid cooling method was almost the same. Those findings suggest that microwave-cured denture base resin is valuable in clinic.
Denture Bases↗
Comparison of microwave-polymerized denture base resins.
Three denture base resins, two designed for microwave polymerization and one for host-water-bath-processing, were compared. Results indicated that all four tested thicknesses (3, 6, 11.6, and 17.7 mm) of the water-bath-polymerized samples and one of the microwave-polymerized resins were porosity-free. When the water-bath-polymerized material was microwave processed, porosity was found when resin thickness exceeded 3 mm. When one resin designed for microwave polymerization was irradiated using the high-wattage (513 W), shorter cycle (4 minutes 52 seconds), porosity also occurred when the thickness exceeded 3 mm. Porosity did not occur until there was 9 mm of thickness when the lower-wattage (75.9 W), longer cycle (15 minutes 26 seconds) was used. No significant differences in transverse strength or hardness were noted between the materials.
Denture Bases↗
Flexural strength and moduli of hypoallergenic denture base materials.
STATEMENT OF PROBLEM: Hypoallergenic denture base materials show no residual methyl methacrylate (MMA) or significantly lower residual MMA monomer content compared to polymethyl methacrylate-based (PMMA) heat-polymerizing acrylic resin. There is insufficient knowledge of the mechanical properties of hypoallergenic denture base materials to warrant their use in place of PMMA-based acrylic resins for patients with allergic reaction to MMA. PURPOSE: This in vitro study compared flexural strength and flexural modulus of 4 hypoallergenic denture base materials with flexural strength/modulus of a PMMA heat-polymerizing acrylic resin. MATERIAL AND METHODS: The following denture base resins were examined: Sinomer (heat-polymerized, modified methacrylate), Polyan (thermoplastic, modified methacrylate), Promysan (thermoplastic, enterephthalate-based), Microbase (microwave-polymerized, polyurethane-based), and Paladon 65 (heat-polymerized, methacrylate, control group). Specimens of each material were tested for flexural strength and flexural modulus (MPa, n = 5) according to ISO 1567:1999. The data were analyzed with 1-way analysis of variance and the Bonferroni-Dunn multiple comparisons post hoc analysis for each test variable (alpha=.05). RESULTS: Flexural strength of Microbase (67.2 +/- 5.3 MPa) was significantly lower than Paladon 65 (78.6 +/- 5.5 MPa, P <.0001). Flexural strength of Polyan (79.7 +/- 4.2 MPa, P =.599), Promysan (83.5 +/- 3.8 MPa, P =.412), and Sinomer (72.3 +/- 2.1 MPa, P =.015) did not differ significantly from the control group. Significantly lower flexural modulus was obtained from Sinomer (1720 +/- 30 MPa, P =.0007) compared to the PMMA control group (2050 +/- 40 MPa), whereas the flexural modulus of Promysan (2350 +/- 170 MPa, P =.0005) was significantly higher than the PMMA material. Microbase (2100 +/- 210 MPa, P =.373) and Polyan (2070 +/- 60 MPa, P =.577) exhibited flexural modulus similar to the PMMA material. The tested denture base materials fulfilled the requirements regarding flexural strength (>65 MPa). With the exception of Sinomer, the tested denture base resins passed the requirements of ISO 1567 regarding flexural modulus (>2000 MPa). CONCLUSION: Flexural modulus of Promysan was significantly higher than the PMMA material. Microbase and Sinomer exhibited significantly lower flexural strength and flexural modulus, respectively, than PMMA. The other groups did not differ significantly from the control group.
Acrylic Resins↗
Comparison of bond strengths between adhesive and conventional acrylic resins to cobalt chromium denture base alloy.
In removable partial dentures there is normally no chemical bonding between the cast alloy and the poly(methylemethacrylate). Mechanical retention of the resin to the casting is required and presents a significant challenge during the design of partial dentures. Recently developed adhesive denture base resins which contain the monomer 4-methacryloxyethyl trimellitate anhydride can create a chemical bond to partial denture alloys. This study investigated the bond strength of adhesive denture base resin (Metafast) and conventional acrylic resin (Croform x 10) to partial denture alloy (CoCr) under three different storage conditions (dry, water, water with thermocycling). The results showed that the bond strength of the conventional acrylic resin (Croform x 10) was less than the bond strength of the adhesive denture base resin (Metafast) and the storage environment had a significant effect upon the bond strength of both resins.
Acrylic Resins↗
On the clinical deformation of maxillary complete dentures. Influence of denture-base design and shape of denture-bearing tissue.
This paper aimed to study the influence of denture base design and the shape of the denture-supporting area on the functional deformation of maxillary complete dentures. Six strain-gauged duplicate maxillary dentures were made for the study of two test subjects with different shapes of the palatal vault. Each subject was supplied with two polymethyl methacrylate dentures, one with a 1-mm-thick palatal base and the other 2 mm thick. A third denture was constructed with a cobalt-chromium base. The functional loading tests included maximum biting and the chewing of the food test samples. An analysis based on chewing time and total number of chewing cycles per test piece was also made. The results showed that surface straining is highly complex at the anterior part of the maxillary dentures constructed from polymethyl methacrylate and that increasing the denture thickness per se might not be accompanied by a reduction of strain. The results also suggest that high thrust to the supporting tissue is produced with high palatal vault dentures made in polymethyl methacrylate. The study proposes that cobalt-chromium bases may be used in maxillary dentures to reduce functional deformation and thrust to the supporting tissues at the anterior part of the maxilla.
Aged↗
Bond strength of denture teeth to denture base resins.
PURPOSE: The study examined the bond strength between 2 types of denture teeth and 3 denture base resins. The denture teeth were untreated, prepared with diatorics, or treated with dichloromethane, a solvent. MATERIALS AND METHODS: Conventional denture teeth and cross-linked denture teeth were bonded to either a heat-cured denture base resin, a microwave-cured denture base resin, or a pour-type denture base resin. Compressive load was applied at 45 degrees on the palatal surface of each tooth until fracture. RESULTS: Conventional resin teeth possessed higher bond strength than cross-linked denture teeth. The heat-cured denture base resin significantly surpassed the microwave-cured denture base resin in bond strength. Both materials were better than the pour-type resin. The application of dichloromethane resulted in a significantly better improvement in bond strength compared to the use of diatorics. CONCLUSION: It is recommended that dichloromethane be applied on the denture teeth ridge-lap area prior to denture base processing.
Acrylic Resins↗