Development and characterisation of dental composites containing anisotropic fluorapatite bundles and rods.

Objectives: To develop dental composites incorporating fluorapatite (FA) crystals as a secondary filler and to characterise degree of conversion, key mechanical properties and fluoride release.

Methods: FA rod-like crystals and bundles were hydrothermally synthesised and characterised by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), X-ray diffraction (XRD) and F MAS-NMR. Composites were formulated containing BisGMA/TEGDMA/BisEMA and barium-aluminium-silicate glass (0FA).

An approach to understanding tribological behaviour of dental composites through volumetric wear loss and wear mechanism determination; beyond material ranking.

Objective: To investigate the fundamental wear mechanisms of six resin-based composite (RBC) formulations during short-term in vitro wear testing.

Materials: RBC materials were condensed into rectangular bar-shaped specimens and light irradiated using the ISO 4049 specimen manufacture and irradiation protocol. Wear testing (n=10 specimens for each RBC) was performed on a modified pin-on-plate wear test apparatus and wear facets were analysed for wear volume loss using a white light profilometer.

In vitro enamel thickness measurements with ultrasound.

In the work described here, agreement between ultrasound and histologic measurements of enamel thickness in vitro was investigated. Fifteen extracted human premolars were sectioned coronally to produce 30 sections. The enamel thickness of each specimen was measured with a 15-MHz hand-held ultrasound probe and verified with histology.

In vivo reproducibility study of ultrasound for monitoring enamel thickness.

Objective: This work assesses ultrasound's reproducibility for monitoring enamel thickness in vivo.

Study Design: This clinical reproducibility study recruited 30 healthy consenting volunteers. The enamel thickness on an intact maxillary central incisor was evaluated at 3 sites on 3 separate visits, 1 week apart.

Wear resistance of four types of vacuum-formed retainer materials: a laboratory study.

Objective: To investigate the resistance to wear of four different vacuum-formed retainer (VFR) materials: Essix C+, Essix ACE, Duran, and Tru-Tain. Essix C+ is a polypropylene polymer; the other materials are polyethylene co-polymers.

Materials And Methods: The study was undertaken at the Leeds Dental Institute, Leeds, UK, with 26 samples in each group.

Diagnostic ultrasound tooth imaging using fractional Fourier transform.

An ultrasound contact imaging method is proposed to measure the enamel thickness in the human tooth. A delay-line transducer with a working frequency of 15 MHz is chosen to achieve a minimum resolvable distance of 400 μm in human enamel. To confirm the contact between the tooth and the transducer, a verification technique based on the phase shift upon reflection is used.

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.

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.

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.