Biomedical subjects

A S Juszczyk

Publications and source records attributed to A S Juszczyk.

7 recordsLinked to original sources

PubMed2006

The effect of cyclic drying on dimensional changes of acrylic resin maxillary complete dentures.

Poly(methyl methacrylate) dentures may exhibit dimensional changes when drying. Drying has been shown to destroy Candida albicans. This study investigates the effect of simulating overnight cyclic drying on dimensional changes of four complete denture base materials. Denture specimens used in this study had been prepared for a previous study. All dentures had been kept hydrated at room temperature for 2 years. The materials used were, group 1, conventionally packed and cured Trevalon, group 2 was injection moulded and conventionally cured (Trevalon Success), group 3 (Acron MC) and group 4 was Microbase, which is injection moulded and microwave cured. The measurements of the inter-molar and inter-premolar width, and anterior posterior dimension between the premolars and molars were recorded after 8 h drying and then after four cycles of dehydration and rehydration. The dentures were more dimensionally stable in the anterior posterior than the cross arch dimension. There was a statistically significant (P < 0.02) increase in the intermolar width for Trevalon, Trevalon Success and Acron after 8 h drying and after four cycles. There was a statistically significantly difference between Microbase and the other materials after 8 h drying and there was a significant difference between the injection moulded groups in the interpremolar width (Trevalon Success versus Acron, Trevalon Success versus Microbase) after cyclic drying. Although statistically significant dimensional changes were observed for all materials these were small and were considered not to be clinically significant. Microbase was the least dimensionally stable material during air-drying.

Acrylic Resins↗

PubMed2005

Immediate replacement removable partial dentures with cobalt-chromium frameworks: rationale, technology and a case report.

The advantages of removable partial dentures with cobalt-chromium frameworks over those made entirely of acrylic resin, in oral health and hygiene, are well documented. However, in cases where teeth are to be extracted for fitting the removable partial denture, a difficulty arises because of the need to test the fit of the removable partial denture framework. The advent of two modern technologies-- laser welding and metal bonding agents -- make it possible to test the fit of the major part of the framework prior to adding additional metal components to support artificial teeth. A case is described in which the four lower incisors were extracted. The main part of the framework was constructed and its fit tested. A second casting was laser-welded to the lingual plate of the first casting to support the artificial incisor teeth. This technique avoids the need to make an acrylic resin temporary denture but incurs the cost of the additional technical work and so the advantages may be considered to be economically neutral.

Adult↗

PubMed2000

The influence of handling technique on the strength of phosphate-bonded investments.

OBJECTIVES: This study examined the influence of six handling techniques on the strength of four phosphate-bonded investment (PBI) materials. The size and distribution of pores produced by the handling techniques were investigated and their effect on room temperature strength determined. METHODS: Specimens were tested for strength using four point bend at a cross-head speed of 1 mm min-1. The fracture surface of randomly selected specimens was viewed through a light microscope to determine the pore size. A three-parameter Weibull distribution was used to describe strength giving values of Weibull modulus and characteristic strength. RESULTS: The handling technique that produced the smallest pore size resulted in the highest strength. Significant differences in strength (90% confidence level) were found between most handling techniques. The reduction of pore size by mechanical spatulation and setting under pressure was found to be the most effective method of increasing the strength of PBI. SIGNIFICANCE: Previous studies have related handling technique to the inclusion of air bubbles in dental investments but have not reported any consequent effect on strength. PBI materials are used in production of a range of dental appliances with a variety of different material forming processes and are required to withstand the loads applied without fracture or distortion to ensure accuracy of fit of these prostheses. The use of a handling technique that reduces pore size can significantly increase the strength of PBIs, thereby decreasing the possibility of die fracture or degradation.

Dental Casting Investment↗

PubMed1993

Accuracy of fit of cobalt-chromium removable partial denture frameworks on master casts.

Fifty-six cobalt-chromium removable partial denture frameworks made to the same design were found to fit their master casts poorly. Spaces were significantly greater between palatal aspects of abutment teeth and palatal reciprocal arms, and between buccal aspects of occlusal rests and rest seats. Excessive contraction towards the centre of the palate was found. Expansion of the refractory investment may not have compensated adequately for solidification and cooling contraction of the cobalt-chromium alloy. Although dimensional changes in investment and casting are by volume, no evidence of anisotropic expansion of castings in a vertical direction was found.

Chromium Alloys↗

PubMed1993

An examination of cingulum rest seats in incisor and canine teeth.

This study examined rest seats prepared in the cingula of incisor and canine teeth in terms of their form and their ability to offer denture support. Fifty rest seats prepared in vivo were examined and the fit of the denture framework was assessed at the trial insertion stage. Twenty two of the rests investigated showed no approximation (within 0.1 mm) between the casting and the floor of the rest seat. Investigations in vitro showed the provision of rest seats reduced the labial displacement of incisor and canine abutments under transmitted load compared to the same teeth without preparations.

Cuspid↗

PubMed1991

A two part hinged partial denture design for lower Kennedy Class 4 cases.

It is often difficult to provide patients who have lost lower anterior teeth with a retentive and aesthetic restoration, particularly if the molar and premolar teeth are lingually tilted. A two part hinged denture fully engaging all lingual undercuts for retention provides a useful extension to recognised partial denture design practice.

Denture Design↗

PubMedDate not supplied

The surface of investments poured against different duplicating media.

Two phosphate-bonded investments that were poured into molds of a duplicating gel and a poly(vinyl siloxane) duplicating medium were examined for surface hardness. Untreated surfaces were also examined by the confocal microscope and the scanning electron microscope. The Brinell hardness of samples poured in poly(vinyl siloxane) was greater than that of the same investment poured in duplicating gel. Investments were hardest as set and were significantly softened by drying. Cast hardeners achieved some rehardening of the dried investment samples. Microscopic examination of the investment surfaces revealed greater irregularity of samples poured in duplicating gel than in poly(vinyl siloxane), particularly in one investment.

Agar↗