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PubMed2005

Water absorption characteristics of two types of acrylic resin obturators.

STATEMENT OF PROBLEM: The mechanisms of water accumulation in the inner space of a closed hollow obturator are not understood, and it is not known whether the porosity of acrylic resin is involved in these mechanisms. PURPOSE: The purpose of this study was to evaluate water absorption by solid and closed hollow obturators and to determine the mechanisms of water accumulation in the inner space of the closed hollow obturator. MATERIAL AND METHODS: Twenty solid and 20 closed hollow spherical specimens (30 mm in diameter) were fabricated from heat-polymerized acrylic resin (Acron Clear). Closed hollow specimens consisted of 2 hemispheres (30 mm in diameter, 1.5 mm in thickness) joined with autopolymerizing resin (Unifast II). Ten solid and 10 closed hollow specimens were immersed in distilled water at 37 degrees C, while the other specimens were stored in an atmosphere of 100% relative humidity at 37 degrees C. Each specimen was weighed every 24 hours for 180 days, and weight changes between each group were compared by 2-way ANOVA and the Tukey HSD test. Split-plot design ANOVA was used to compare the course of the weight change over 180 days (alpha=.05). RESULTS: The weight of the closed hollow specimens increased immediately and became saturated by day 30, with an increase of 1.44% from the initial weight. Water accumulation was not observed inside the closed hollow specimen during the 180-day storage period. The weight of solid specimens increased more slowly than that of closed hollow specimens; by day 180 the weight of the latter had increased by 1.16%. However, no significant difference in changes in mean mass of the same type of specimen was observed between the 2 storage conditions. CONCLUSION: These results suggest that water accumulation inside a closed hollow obturator is unrelated to the water absorption properties of the acrylic resin.

Absorption↗
PubMed1990

Polymerization shrinkage of index and pattern acrylic resins.

Inadequate dimensional stability caused by polymerization shrinkage has been reported concerning the various applications of acrylic resins. The objective of the study was to evaluate dimensional changes of two self-curing acrylic resins marketed as pattern and index material. Early volumetric changes were measured with a dilatometer and late linear changes were recorded with an inductive transducer. After 24 hours the volumetric shrinkage was 7.9% for Duralay resin and 6.5% for Palavit G resin; 80% of the change appears before 17 minutes at room temperature. Shrinkage was significantly increased when the proportion of powder in the mix was diminished. Results suggest that these resins should be used with some method to compensate for the shrinkage, when used as index material. However, the dimensional change might provide significant advantages for intracoronal castings.

Acrylic Resins↗
PubMed1978

Fabrication of interim acrylic resin removable partial dentures with clasps.

An orderly sequence of steps for construction of an interim acrylic resin partial denture has been presented. The technique allows the dentist to fabricate an effective restoration that has a definite path of insertion and removal that can be placed in the patient's mouth with little time spent on adjustment and correction. This technique may be used with heat- or cold-curing acrylic resin.

Acrylic Resins↗
PubMed2004

Surface roughness of acrylic resins submitted to mechanical and chemical polishing.

Surface roughness is extremely important as it influences micro-organism accumulation and consequently oral health. The aim of the present study was to evaluate the influence of mechanical polishing (MP) and chemical polishing (CP) on surface roughness of four heat-cured denture base acrylic resins. Twenty sample discs were prepared for each of the following acrylic resins: Classico (CL), QC 20 (QC), Acron MC (AC) and Onda Cryl (ON). The first two are boiling cured resins and the latter two are microwave cured. After curing and deflasking, samples were ground and subdivided into two groups: MP, which received pumice slurry, chalk powder, soft brush and felt cone, at a bench vice; and CP, which received fluid specifically for chemical polisher. Surface roughness was measured using a Surf Corder SE 1700 rugosimeter. Data collected were statistically analysed by analysis of variance followed by Tukey's test. Surface roughness means in mum were: CL-MP: 0.0350; CL-CP: 0.2298; QC-MP: 0.0307; QC-CP: 0.1792; AC-MP: 0.0312; AC-CP: 0.2700; ON-MP: 0.0321; ON-CP: 0.2949. It can be concluded that MP produced significantly smoother surfaces than CP and that surface roughness because of MP was not influenced by acrylic resin type, whereas this was not true of CP.

Acrylic Resins↗
PubMed1997

Retention of Candida albicans on acrylic resin and silicone of different surface topography.

STATEMENT OF PROBLEM: The adhesion of microorganisms to a denture surface is a prerequisite for colonization. PURPOSE: This study compared the retention of Candida albicans on smooth and rough acrylic resin and silicone surfaces after a washing procedure to determine the effect of surface roughness on prosthesis infection and hygiene. MATERIAL AND METHODS: Standardized cell suspensions of C. albicans were incubated with smooth and rough acrylic resin and silicone surfaces for 1 hour at 24 degrees C. After washing, cells that had been retained on the surface were stained with acridine orange and examined with incident beam fluorescent microscopy. RESULTS: There was no significant difference in cell numbers on either of the smooth surfaces. Significantly higher numbers of cells (p > 0.0005) were observed on roughened surfaces (silicone > acrylic resin) than on smooth surfaces. The fitting surface of the maxillary denture was not polished. CONCLUSIONS: Silicones used in prostheses were processed against dental stone. The resultant surface roughness may facilitate microbial retention and infection and should therefore be kept to a minimum.

Acridine Orange↗
PubMed2003

The effect of disinfectant solutions on the hardness of acrylic resin denture teeth.

This investigation studied the effects of disinfectant solutions on the hardness of acrylic resin denture teeth. The occlusal surfaces of 64 resin denture teeth were ground flat with abrasives up to 400-grit silicon carbide paper. Measurements were made after polishing and after the specimens were stored in water at 37 degrees C for 48 h. The specimens were then divided into four groups and immersed in chemical disinfectants (4% chlorhexidine; 1% sodium hypochlorite and sodium perborate) for 10 min. The disinfection methods were performed twice to simulate clinical conditions and hardness measurements were made. Specimens tested as controls were immersed in water during the same disinfection time. Eight specimens were produced for each group. After desinfection procedures, testing of hardness was also performed after the samples were stored at 37 degrees C for 7, 30, 60, 90 and 120 days. Data were analysed using two-way analysis of variance (anova) and Tukey's test at 95% confidence level. According to the results, no significant differences were found between materials and immersion solutions (P > 0.05). However, a continuous decrease in hardness was noticed after ageing (P < 0.05). It was conclude that the surfaces of both acrylic resin denture teeth softened upon immersion in water regardless the disinfecting solution.

Acrylic Resins↗
PubMed1989

[Application of isocyanate separating agent for acrylic resin].

The most widely used agents for separating acrylic resin from gypsum molds are the water-soluble alginates, which produce a very thin water- and organic solvent-insoluble calcium alginate film on the gypsum surface. In the present study, a new type of separating agent, an isocyanate type coating agent, was developed and it's properties were investigated. This coating agent is composed mainly of trimethylol-propane-tolylenediisocyanate and ethyl-acetate, with a small amount of bis-tributyl-tin oxide as catalyst. At first, a thin film was formed on the surface by application of the agent, and then alkyl-phosphate was applied to this film to ensure easy separation of the cured resins from the molds. The molds treated with this separating agent had a glossy, hard surface. The surface of the cured resins treated in this way was glossier and smoother than that of resin treated with the water-soluble alginates.

Acrylic Resins↗
PubMed1999

Soft acrylic resin materials containing a polymerisable plasticiser II: water absorption characteristics.

The main disadvantage of soft acrylic resin denture lining materials is the loss of plasticiser leading to gradual hardening. One possible solution to this problem is the use of a polymerisable plasticiser. A material based on such a plasticiser failed in clinical trials due to a combination of prolonged water uptake and low strength. Similar materials with improved strength have been developed and it is the aim of this study to investigate their water uptake characteristics. Water uptake from distilled water, an artificial saliva and 0.9 M saline has been determined for three experimental materials and 'Supersoft', a commercial plasticised acrylic resin denture lining material. Solubilities were determined after 6 months and diffusion coefficients calculated where appropriate. All the experimental materials had a lower uptake and solubility than 'Supersoft' in all solutions. For each material uptake was lower from solution than from distilled water. All diffusion coefficients were in the range expected for this type of material. The water uptake of the experimental materials was influenced by the relative hydrophilicity of the monomer used.

Absorption↗
PubMed1988

Bond strength of 4-META acrylic resin denture base to cobalt chromium alloy.

This study was designed to compare the bond strength of a conventional poly(methyl methacrylate) acrylic resin denture base (Lucitone 199) with a recently developed acrylic resin base containing 4-META (Meta-Dent) to CoCr metal alloy by using various designs representative of clinical situations. The mechanical bond strength of Lucitone 199 resin was compared with the chemical and combination chemical and mechanical bond strength of Meta-Dent resin. The following conclusions may be extrapolated from the results. 1. The highest bond strength was observed between Meta-Dent resin and the plain flat metal plate. 2. The second highest bond strength was observed between Meta-Dent resin and the flat metal plate with two posts. 3. The lowest bond strengths were observed between Meta-Dent resin and the samples containing mesh retentive mechanisms. 4. The mean bond strength of Lucitone 199 resin was highest for the flat metal plate with two posts, followed by the large mesh. Bond strength with the small-mesh samples was lowest. These differences were not statistically significant. 5. The mean bond strengths of Meta-Dent resin to flat metal plates with or without posts was significantly higher than any of the Lucitone 199 resin metal bond strengths, to the 99% confidence level. Additional studies will be necessary to confirm the validity of these conclusions with respect to clinical removable partial dentures. Longitudinal investigations will be required to reveal clinical performance of these resin systems.

Acrylic Resins↗
PubMedDate not supplied

[External fixation with autopolymerizing acrylic resin].

In November 1970, a new method of skeletal fixation was devised using self-curing acrylic resin. Manipulative reduction of the displaced fracture is made using screws inserted into the bone fragments under an image intensifier. After reduction, the proximal and distal fragments are joined together with the aid of self-curing acrylic resin. Adjacent joints can be exercised immediately after operation and the fixation is so firm that the use of a plaster cast after operation is not necessary. This simple method can be used in osteosynthesis, compression arthrodesis and various types of osteotomy.

Acrylic Resins↗