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PubMedDate not supplied

Adherence of phenotypically switched Candida albicans to denture base materials.

PURPOSE: The purpose of this study was to investigate in vitro the levels of adhesion of phenotypically switched and nonswitched Candida albicans to the smooth and rough surfaces of heat-cured acrylic resin, Molloplast B, and Novus. MATERIALS AND METHODS: Nonswitched and switched cells of C. albicans 3153A were prepared and adhesion assays were performed. RESULTS: There was no difference in the level of adhesion of blastospores in their nonswitched or switched state. The adherence of hyphae to all three denture base materials was statistically significantly increased when in a switched form. There was greater adhesion to the two soft lining materials than to the acrylic resin. CONCLUSIONS: Rough surfaces promote adhesion. There was no significant difference in the adhesion of switched and nonswitched blastospores, but there was increased adhesion of hyphal cells.

Acrylic Resins↗
PubMed1988

Clinical and laboratory evaluation of visible light-cured denture base resins and their application to orthodontics.

A series of investigations is being conducted to examine the applicability of visible light-cured resins to orthodontics. The experimental vehicle is the Hawley retainer, which is made from autopolymerized (AP), heat-cured (HC), thermoplastic Biocryl 2 (BC), and Traid visible light-cured (VLC) resins. In all physical property testing, it was found that VLC resins met or exceeded required values as established by ADA Specification No. 12 for denture base polymers. In vitro bacterial adherence studies showed that more organisms adhered to heat-cured specimens than to the other specimens. In vivo studies using split-palate Hawley retainers demonstrated slightly less bacterial adherence to BC than to the other resins. Scanning electron microscopy (SEM) observations have shown the BC surface to be the smoothest, although surface chemistry also seems important. None of the materials being tested appears to cause any significant change in the subjacent subgingival bacterial flora. There was no adverse tissue reaction under any of the materials when observed clinically. Manipulation characteristics and time of fabrication appear to be dependent on the depth of the palate and the skill of the operator.

Acrylic Resins↗
PubMed1980

Fracture toughness of denture base acrylics.

Two types of fracture toughness specimen, the tapered cleavage (TC) and single edge notch (SEN), are compared. Their reproducibility, accuracy, and ease of preparation are investigated. The fracture toughness of four types of acrylic resin, heat cured, autopolymerized, injection molded, and high impact resistant, has been determined by one or both of the above methods. High impact acrylic proved too ductile for either of the specimens to be used to assesss K1c; however, these deviations from brittle behavior were revealed by the tests and some insight into impact resistance was gained. The SEN specimens proved capable of distinguishing between the fracture toughness characteristics of the four types of denture base acrylics and proved easy to fabricate. The TC specimens proved difficult to fabricate requiring specialized equipment; however, once made, the specimens revealed more of the fracture process than did the SEN specimens.

Acrylic Resins↗
PubMed2003

The effect of the addition of poly(methyl methacrylate) fibres on some properties of high strength heat-cured acrylic resin denture base material.

The self-reinforcement of acrylic resin with butadiene styrene surface treated poly(methyl methacrylate) fibres has been reported to have the potential to substantially improve the transverse bend strength of conventional heat-cured acrylic resin. The aim of this study was to investigate the effect of the addition of butadiene styrene surface treated poly(methyl methacrylate) fibres in cross-ply arrangement to high impact acrylic resin on the transverse and impact strength. Specimens were prepared as specified in the International Standard Organization and British Standards for the Testing of Denture Base Resins (ISO 1567, 1988; BS 2487, 1989) and the British Standard Specification for Orthodontic resins (BS 6747, 1987) for transverse bend and impact testing. The impact strength was measured using a Zwick pendulum impact tester and the transverse bend strength measured using a Lloyds Instruments testing machine. The results showed that the impact strength was not improved with the addition of fibres, high impact acrylic resin with fibres (LF) 11.1 kJ m-2 and high impact acrylic resin (L) (12.5 kJ m-2). The modulus of rupture was decreased with the addition of fibres (57.8 MPa) for (LF) compared with (60.4 MPa) for (L). The modulus of elasticity was also reduced with the addition of fibres (1834.9 MPa) (LF) and 2086.2 MPa (L) as was the peak load (LF) (50.8 N) and (L) (55.8 N). It was concluded that the addition of surface treated poly(methyl methacrylate) fibres in cross-ply arrangement to high strength acrylic resin did not produce an improvement in the impact or transverse strength and cannot be recommended as a method of reinforcement.

Acrylic Resins↗
PubMed1999

Method for enhancing retention in complete denture bases.

STATEMENT OF PROBLEM: Physical retention of a denture depends on adhesion of a salivary film to its fitting surface and supporting tissues. Adhesion is influenced by many factors. PURPOSE: This study examined the effect of the texture of the fitting surface on denture retention. MATERIAL AND METHODS: According to the method developed, mucosal-supported palatal bases were made for 10 dentate subjects who had no obvious oral disease, history of allergy to dental materials, or palatal mucosal undercuts. A specially designed strain gauge force transducer and a pen-chart recorder were used to record forces that were needed to dislodge the bases from the palate. Forces were recorded 30 times (10/day) for each subject. Similar forces were recorded after the fitting surface of each base was uniformly air-particle abraded under 4 kg/cm2 of pressure for 1 minute with 50-microm grit alumina dust. Data were analyzed with a 2-sample Student t test and a paired t test. RESULTS: Substantial variations for all measurements were observed both between and within subjects. Notwithstanding, these variations, the mean retention of the bases significantly (P <.05) increased by more than 2-fold when the fitting surface was air-particle abraded. These force values were similar to those recorded previously for well-fitting mucosal-supported palatal bases in a separate group of dentate subjects. CONCLUSIONS: While reinforcing the importance of good adaptation of the denture to the tissues, these findings also suggest that an additional improvement in denture retention can be accomplished after the fitting surface is air-particle abraded.

Adult↗
PubMed1984

Denture base resins.

Numerous investigations have concluded that the conventional acrylic resins, processed with the usual technique of compression molding, produce dentures that are just as stable in dimension and as satisfactory as dentures produced with special resins and elaborate processing equipment. The physical properties of injection molded dentures are not superior to those of acrylic resin dentures produced by the usual carefully controlled compression molding techniques. Cold-curing acrylic resins produce dentures that are as satisfactory as those made from heat-curing resins.

Acrylic Resins↗