Biomedical subjects

Nigel L Bubb

Publications and source records attributed to Nigel L Bubb.

3 recordsLinked to original sources

PubMed2006

The use of confocal microscopy to assess surface roughness of two milled CAD-CAM ceramics following two polishing techniques.

OBJECTIVE: To assess the effects of two polishing techniques on the surface roughness of a commercial and experimental dental ceramic for use in a chairside CAD-CAM system. METHODS: A standard onlay was reproduced fifteen times in each of the two materials. Each stub was retained and examined using confocal microscopy in reflection mode. Five random samples of each were polished with Sof-Lex aluminium oxide discs, five polished with diamond impregnated polishing wheels and five left in the as-machined state. Surface roughness parameters were measured for each material group in each condition and statistical analyses carried out to determine the efficacy of the polishing techniques for each material. RESULTS: The as-machined surfaces of both materials had a statistically similar surface finish. Polishing with Sof-Lex discs was effective at reducing surface roughness of both materials. Whilst the polishing wheels were effective in reducing surface roughness for the commercial material, there was no statistically significant difference in the surface roughness of the experimental material in the as-machined or wheel polished states. SIGNIFICANCE: Although Sof-Lex discs were effective in reducing surface roughness of the two materials examined in this study, wheel polishing should not be used to reduce surface roughness of the experimental material. This will need to be taken into consideration in any future clinical studies of this material.

Aluminum Oxide↗

PubMed2005

Thermal conductivity through various restorative lining materials.

OBJECTIVES: Traditional teaching has advocated the placement of insulating materials under restorations to protect against 'thermal shock'. Often this involves placement of a thick zinc-oxide eugenol cement lining. The purpose of this in vitro study was to assess the heat transfer through four lining materials and dentine and to relate these findings to the temperature exposures that may be experienced in the oral environment. METHODS: Two 'traditional' linings, zinc oxide eugenol cement (ZNOE) and calcium hydroxide paste (CAOH), and two more contemporary materials, a resin modified glass polyalkenoate (RMGP) and dentine bonding system (DBS) were studied in addition to dentine itself. Seven samples of each material were tested by utilising a Lees' Disc apparatus. Incorporation of thermocouples allowed heat transfer through the sample to be recorded. Thermal conductivity (J/m/s/ degrees C) was calculated for individual samples and a mean value obtained for each material. One way ANOVA and post hoc Tukey's tests were applied to the data obtained. RESULTS: In ascending order of thermal conductivity, DBS<CAOH<RMGP<DENTINE<ZNOE. Statistical analysis revealed that the thermal conductivity of DBS was significantly less than RMGP, DENTINE and ZNOE (p<0.05); CAOH was significantly less than DENTINE and ZNOE (p<0.05); RMGP was significantly higher than DBS and significantly less than DENTINE and ZNOE (p<0.05). CONCLUSIONS: Thermal insulation is not a major consideration in cavity lining and therefore other criteria for selection of a lining material should be applied.

Analysis of Variance↗

PubMed2005

Reinforcement of poly(methyl methacrylate) denture base with glass flake.

OBJECTIVES: Since the introduction of poly(methyl methacrylate) as a denture base material, it has suffered from having relatively poor mechanical properties. Many methods of improving its strength and toughness have been investigated. Most of these have not been adopted due to: increased cost, the need for specialist processing equipment or increased laboratory time due to more complicated procedures. Glass flake has been used as a reinforcing agent in many industrial polymers, but is as yet untested with denture base acrylic materials. The aim of this study is to evaluate the effect of adding glass flake to denture base acrylic powder on the fracture toughness of the set material. METHODS: Glass flake was added in 5, 10 or 20% w/w to Trevalon denture base powder. The material was mixed, flasked, packed and processed in a manner typical for a denture base material. Fracture toughness was determined using a double torsion test technique. RESULTS: The addition of glass flake gave up to a 69% increase in fracture toughness compared to plain Trevalon material. The addition of 5% glass flake lead to an improvement in fracture toughness that was statistically significant compared to both plain Trevalon and the 10 and 20% groups. SIGNIFICANCE: The significant improvement in fracture toughness of a denture base acrylic material using glass flake is an extremely promising result. Other mechanical properties will require testing before glass flake can be recommended as a reinforcing agent for denture base acrylic materials.

Dental Materials↗