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PubMed1996

Composition and effect of denture base resin surface primers for reline acrylic resins.

This study investigated the effect of resin surface primers for reline acrylic resins on the surface texture of denture base resin by use of scanning electron microscopy. Analysis of the composition of the primers was also conducted. The composition of the primers was classified into three groups: solvent based, monomer based, and monomer and polymer based. Scanning electron microscopic observation revealed various effects of the primers on the denture base resin surface, which depended on the composition of primers.

Acetone↗
PubMed1996

Effect of light-exposure duration on the amount of leachable monomers from light-activated reline material.

Leaching of monomers from light-activated direct intraoral reline material (Lebaron LC) was determined by means of high-pressure liquid chromatography analysis. This study evaluated the effects of exposure duration and thickness to determine appropriate curing conditions that reduce the levels of unreacted monomeric components. Prolonged duration of exposure (30 minutes) reduced the amount of leached monomer. However, the results of this study indicated that the amount of leached monomeric components increased with an increasing reline material thickness. The results suggest that the light-activated reline material should be cured for sufficient prolonged exposure duration.

Chromatography, High Pressure Liquid↗
PubMed1996

Unrestricted linear dimensional changes of two hard chairside reline resins and one heat-curing acrylic resin.

The selection and use of hard chairside reline resins must be made with regard to dimensional stability, which will influence the accuracy of fit of the denture base. This study compared the dimensional change of two hard chairside reline resins (Duraliner II and Kooliner) and one heat-curing denture base resin (Lucitone 550). A stainless steel mold with reference dimensions (AB, CD) was used to obtain the samples. The materials were processed according to the manufacturer's recommendations. Measurements of the dimensions were made after processing and after the samples had been stored in distilled water at 37 degrees C for eight different periods of time. The data were recorded and then analyzed with analysis of variance. All materials showed shrinkage immediately after processing (p < 0.05). The only resin that exhibited shrinkage after 60 days of storage in water was Duraliner II; these changes could be clinically significant in regard of tissue fit.

Acrylic Resins↗
PubMed1997

Refining hollow obturator base using light-activated resin.

The disadvantages of an open-type hollow obturator include difficulty in polishing and cleaning of the internal surface, food accumulation in the hollow obturator and inability to obtain support from the superior aspect in the defect area. This article describes and easy time-saving procedure that uses visible light-activated denture base materials as a reline material to close an open type interim obturator. This procedure can be used successfully for both late stage interim obturators and/or for correcting leakage problems for patients who wear definitive obturators.

Acrylic Resins↗
PubMed1998

Water sorption, solubility, and bond strength of two autopolymerizing acrylic resins and one heat-polymerizing acrylic resin.

STATEMENT OF PROBLEM: Because water sorption of autopolymerizing acrylic reline resins is accompanied by volumetric change, it is a physical property of importance. As residual monomer leaches into the oral fluids and causes tissue irritation, low solubility of these resins is desired. Another requirement is a satisfactory bond between the autopolymerizing acrylic resins and the denture base acrylic resin. PURPOSE: This study compared the water sorption, solubility, and the transverse bond strength of 2 autopolymerizing acrylic resins (Duraliner II and Kooliner) and 1 heat-polymerizing acrylic resin (Lucitone 550). MATERIAL AND METHODS: The water sorption and solubility test was performed as per International Standards Organization Specification No. 1567 for denture base polymers. Bond strengths between the autopolymerizing acrylic resins and the heat-polymerizing acrylic resin were determine with a 3-point loading test made on specimens immersed in distilled water at 37 degrees C for 50 hours and for 30 days. Visual inspection determined whether failures were adhesive or cohesive. RESULTS: Duraliner II acrylic resin showed significantly lower water sorption than Kooliner and Lucitone 550 acrylic resins. No difference was noted in the solubility of all materials. Kooliner acrylic resin demonstrated significantly lower transverse bond strength to denture base acrylic resin and failed adhesively. The failures seen with Duraliner II acrylic resin were primarily cohesive in nature. CONCLUSIONS: Autopolymerizing acrylic reline resins met water sorption and solubility requirements. However, Kooliner acrylic resin demonstrated significantly lower bond strength to denture base acrylic resin.

Absorption↗
PubMed1998

A procedure for relining a complete or removable partial denture without the use of wax.

Various procedures are used to reline removable dentures. Some of these involve the use of wax to seal the denture to the cast for flasking and processing. This necessitates the use of high temperatures for an extended period and involves the risk of warpage of the denture. It is also relatively time-consuming. This article describes a procedure that uses polyvinyl siloxane instead of wax. The procedure is more time efficient and decreases the risk of warpage of the denture.

Dental Impression Materials↗
PubMed1999

Residual monomer concentrations in denture-base acrylic resin after an additional, soft-liner, heat-cure cycle.

OBJECTIVES: To determine the effects on methylmethacrylate (MMA) monomer concentration of a second heat-cure cycle introduced for the purpose of processing a denture soft-liner. METHODS: Two denture-base resins (Lucitone199 and Trevalon; Dentsply International, York, PA, USA) were selected. Heat-cure cycles were S (73 degrees C/90 min + 100 degrees C/30 min); L (73 degrees C/9 h); SM (S + 100 degrees C/2 h); LM (L + 100 degrees C/2 h). Cycles SM and LM thus simulated the effect of a further, soft-liner, heat-cure cycle. Groups (n = 6) of the specimens of the denture-base were prepared in the form of thin polymer disks. Monomer was then obtained from the broken fragments of disks by acetone extraction. Concentrations of MMA monomer were determined by reversed-phase high performance liquid chromatography (HPLC). Two-way ANOVA and independent sample t-tests were used to compare the results. RESULTS: The cycle S, applied to Lucitone199, gave a mean concentration of 1.95 wt% MMA (SD 0.24). The cycle L gave the highest level of residual concentration of MMA monomer in both materials. Cycles SM and LM, applied to Trevalon and Lucitone199, gave significant reductions of residual concentration of MMA monomer (p < 0.05). SIGNIFICANCE: The HPLC method was suitable for determining the amount of residual monomer in the denture-base acrylic resin. A further (soft-liner) heat-cure cycle had a statistically significant effect on reducing residual monomer concentrations, and this may have an effect upon mechanical properties.

Acrylic Resins↗
PubMedDate not supplied

The effect of chairside relining materials on rat palatal mucosa.

OBJECTIVES: To investigate the effects of denture relining materials on oral mucosa in vivo in a rat model. METHODS: Denture-like appliances covering the palate in Wistar rats were relined with a resilient soft linting material and a hard 'chairside' relining material. The effects on the palatal epithelium were studied by quantitative analysis using computerized planimetry. RESULTS: The relining materials caused an increase in the thickness of the keratinized layer, while not increasing the total epithelial thickness. CONCLUSIONS: Relining materials are not totally without effect on oral mucosa. Further in vivo research is indicated.

Acrylic Resins↗
PubMed2001

Effect of the reducing agent on the oxygen-inhibited layer of the cross-linked reline material.

The purpose of this study was to clarify the effect of the reducing agent on the oxygen-inhibited layer of the cross-linked reline material. A commercial autopolymerizing reline resin containing 1,6-hexanediol dimethacrylate as cross-linking agent and 1 wt.% sodium sulphite solution as a reducing agent was prepared. The inhibited layer was observed using an optical transmission microscope under the conditions of the application of sodium sulphite for 0, 1, 5 and 15 min after curing for 10 min in air. As a control, the reline material was cured on sealing from air. Moreover, the three-point flexural strength test was performed under the same conditions. The fracture was then observed using scanning electron microscopy (SEM). Although hardness of the inhibited layer was enhanced after the application of the reducing agent, the layer was still observed. The flexural strength of the control and the groups after application of the reducing agent was significantly higher than the group without reducing agent. SEM examination revealed many polymer beads on the group without reducing agent, whereas polymer beads could not be observed on the groups applying the reducing agent. These results indicated that the application of sodium sulphite was effective in hardening the surface unpolymerized zone.

Analysis of Variance↗
PubMed2001

Effect of viscoelastic properties of resilient denture liners on pressures under dentures.

In order to evaluate the influence of viscoelastic properties of resilient denture liners on the pressures under dentures, a series of creep and stress relaxation tests were carried out using a simplified mandibular edentulous model and denture model. Two diaphragm pressure sensors were attached to the edentulous model so that they contacted the residual ridge and the buccal slope. The results may be summarized as follows: (i) The use of resilient denture liners is effective for stress relief under dentures. (ii) The thickness increase of each denture liners causes the effect of stress relaxation. (iii) The material exhibited viscoelastic behaviour after applying the stress and has the ability to distribute stress or stress relaxation. It is important to understand the viscoelastic behaviours of each resilient denture liner and choose the material according to the clinical situation. The information obtained should be useful to clinicians when they select materials for their patients.

Acrylic Resins↗
PubMed2001

Bonding strength between a hard chairside reline resin and a denture base material as influenced by surface treatment.

Direct relining of dentures made with hard chairside reline resins is faster than laboratory-processed reline systems and the patient is not without the prosthesis for the time necessary to perform the laboratory procedures. However, a weak bond between the autopolymerizing acrylic reline resins and the denture base material has been observed. This study evaluated the effect of six different surface treatments on the bond strength between a hard chairside reline acrylic resin and a heat-cured acrylic resin. Specimens of the heat-cured acrylic resin were divided into seven groups. One of these groups remained intact. In the other groups, a 10-mm square section was removed from the centre of each specimen. The bonding surfaces were then treated with (i) methyl methacrylate monomer, (ii) isobutyl methacrylate monomer, (iii) chloroform, (iv) acetone, (v) experimental adhesive and (vi) no surface treatment -- control group. Kooliner acrylic resin was packed into the square sections and polymerized. The bonding strength was evaluated by a three-point loading test. The results were submitted to one-way analysis of variance (ANOVA) followed by a Tukey multiple range test at a 5% level of significance. No significant difference was found between the surface treatment with Lucitone 550 monomer or chloroform, but both were stronger than the majority of the other groups. The bond strength provided by all the surface treatments was lower than that of the intact heat-cured resin.

Acetone↗
PubMed2002

Effect of a heat-treatment on the linear dimensional change of a hard chairside reline resin.

STATEMENT OF PROBLEM: Little data are available regarding the effect of heat-treatments on the dimensional stability of hard chairside reline resins. PURPOSE: The objective of this in vitro study was to evaluate whether a heat-treatment improves the dimensional stability of the reline resin Duraliner II and to compare the linear dimensional changes of this material with the heat-polymerized acrylic resin Lucitone 550. MATERIALS AND METHODS: The materials were mixed according to the manufacturer's instructions and packed into a stainless steel split mold (50.0 mm diameter and 0.5 mm thickness) with reference points (A, B, C, and D). Duraliner II specimens were polymerized for 12 minutes in water at 37 degrees C and bench cooled to room temperature before being removed from the mold. Twelve specimens were made and divided into 2 groups: group 1 specimens (n=6) were left untreated, and group 2 specimens (n=6) were submitted to a heat-treatment in a water bath at 55 degrees C for 10 minutes and then bench cooled to room temperature. The 6 Lucitone specimens (control group) were polymerized in a water bath for 9 hours at 71 degrees C. The specimens were removed after the mold reached the room temperature. A Nikon optical comparator was used to measure the distances between the reference points (AB and CD) on the stainless steel mold (baseline readings) and on the specimens to the nearest 0.001 mm. Measurements were made after processing and after the specimens had been stored in distilled water at 37 degrees C for 8 different periods of time. Data were subjected to analysis of variance with repeated measures, followed by Tukey's multiple comparison test (P<.05). RESULTS: All specimens exhibited shrinkage after processing (control, -0.41%; group 1, -0.26%; and group 2, -0.51%). Group 1 specimens showed greater shrinkage (-1.23%) than the control (-0.23%) and group 2 (-0.81%) specimens after 60 days of storage in water (P<.05). CONCLUSIONS: Within the limitations of this study, a significant improvement of the long-term dimensional stability of the Duraliner II reline resin was observed when the specimens were heat-treated. However, the shrinkage remained considerably higher than the denture base resin Lucitone 550.

Acrylic Resins↗
PubMed1996

Analysis of composition and structure of hard autopolymerizing reline resins.

The authors investigated the composition and structure of six hard auto-polymerizing reline resins. The chemical compositions, glass transition temperatures, molecular weights and particle size distributions of the powders, and the chemical compositions of the liquids were examined. The powder compositions were classified into three groups. The first group contained poly(methyl methacrylate). The second contained poly(ethyl methacrylate) and poly(methyl methacrylate/ethyl methacrylate) and the third contained poly(ethyl methacrylate). The average molecular weights of these powders was about 2 x 10(5). The indexes of molecular weight dispersion suggested that all powders contained polymers that had a narrow molecular weight distribution. The particle size distribution of these powders was classified into two groups. The first group was mainly in the range of 50-100 microns and the second mainly between 20 and 50 microns. The composition of the liquids was classified into three groups. The first group contained a monofunctional methacrylate monomer. The second contained a monofunctional methacrylate monomer and a plasticizer and the third contained monofunctional methacrylate monomers and cross-linking agents. The results of this experiment showed the differences in composition among the products. This will be useful for examining the relationship between the composition and mechanical properties of hard autopolymerizing reline resins.

Acrylic Resins↗