Properties of various types of denture-base plastics

The effect of fiber reinforcement on the dimensional changes of poly methyl methacrylate resin after processing and after immersion in water: an in vitro study

AIMS AND OBJECTIVES

To evaluate and compare the effect of fiber reinforcement on the dimensional changes of heat-cured poly (methyl methacrylate) resin after processing and immersion in water.

MATERIALS AND METHODS

Three different heat-cure resins were selected for the present study: (1) Nonreinforced heat-cure methyl methacrylate resin, (2) High Impact heat-cured methyl methacrylate resin and (3) Fiberglass reinforced methyl methacrylate resin. Ninety samples were prepared using three different resins and denture bases obtained for the same. The amount of space between the tissue surface and the cast in the anterior, middle and posterior regions is measured after processing and immersion in water for 17 days using a traveling microscope having a least count of 0.001 cm.

RESULTS

Mean and standard deviation were calculated for the dimensional changes and were subjected to statistical analysis (Student t-test, unpaired). Among the three groups of resins, fiber reinforced heat-cured methyl methacrylate resin was found to be statistically highly significant in terms of dimensional changes when compared with the nonreinforced and high impact heat-cured resins.

CONCLUSION

Dimensional changes were evident in all the planes in the three groups studied and were in the following decreasing order-fiberglass reinforced heat-cured poly (methyl methacrylate) resin, high impact heat-cured poly (methyl methacrylate) resin and nonreinforced heat-cured poly (methyl methacrylate) resin.

CLINICAL SIGNIFICANCE

The fibers are added in order to increase the strength of acrylic resin. Considering only the strength may in turn affect the dimensional accuracy of the acrylic resin resulting in loss of retention and stability, affecting the fit of the denture.

Processing shrinkage of heat-curing acrylic resin reinforced with high-performance polyethylene fibre

The incorporation of high-performance polyethylene fibre into acrylic denture-base resin produced a very significant decrease in the processing shrinkage of the material, explained by the highly anisotropic mechanical and thermal properties of the fibres.

A homemade microwaveable denture reline jig

This article describes a procedure for making a denture reline jig for processing denture base resin in a microwave oven. The jig is intended for use with the newer microwave curing denture base resins. The reline jig is economical to produce and is made from fiberglass liquid resin commonly used in automobile body repairs. The fiberglass liquid resin is strengthened by adding fillers of dental stone and chopped fiberglass strands.

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.

Dimensional changes at the posterior border of baseplates made from a visible light-activated composite resin

Dimensional changes of 50 baseplates made of Triad visible light-cured resin were measured before and after curing, placement in water, and drying on the laboratory bench. Results showed that the resin shrinks but improves on storage in water. For persons sensitized to monomer, no free monomer is present in the material. Therefore, Triad resin offers an alternative to conventional self-curing resins often used to make baseplates.