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Biomedical subjects

C H Lloyd

Publications and source records attributed to C H Lloyd.

At least 37 records · Page 2Linked to original sources
PubMed1991

The strength of dental ceramics.

Considerable changes have taken place in the range of ceramic materials available for dental use. Although the appearance of dental porcelain is good and biocompatibility excellent, its mechanical properties are somewhat limited. As a consequence, a number of distinct developments have taken place primarily to achieve greater strength; other goals having been to improve accuracy and simplification of production procedure. Progress has been made, but at the present time newer ceramics must still be regarded as complementary to established porcelains.

Ceramics↗
PubMed1990

Retention of core composites, glass ionomers, and cermets by a self-threading dentin pin: the influence of fracture toughness upon failure.

"Core composite" is available, and glass ionomer or materials based upon it (i.e., cermet, alloy/glass-ionomer mix) have potential for core-forming. Cores are retained routinely by pins, and the suitability of the retention of these materials by pins has been investigated. The maximum tensile force sustained by a particular self-threading dentin pin, selected for its retentive capability, was determined. Pins were embedded to a constant depth in cylindrical specimens. All specimens fractured at a force which correlated linearly with the fracture toughness of the embedding material. The glass-ionomer group of materials was inferior to the core composites, and doubts must surround the use of the former when retention of a core is dependent on dentin pins. The adhesive character of the glass-ionomer-based materials did not lead to failure forces higher than those predicted from their fracture toughnesses. When the data points for these materials were placed on a fracture force/fracture toughness plot together with data from earlier research, no point was displaced significantly from the straight line.

Composite Resins↗
PubMed1989

The effect of an elevated level of residual monomer on the whitening of a denture base and its physical properties.

It has been suggested that incomplete or faulty processing leading to a high level of residual monomer is a factor in denture whitening. Laboratory tests which simulate the cleaning procedures used by patients presenting with whitened dentures have been carried out on specimen strips of acrylic denture base material with high or low levels of residual monomer. The results show that these samples exhibit similar changes and that the high level of residual monomer had no effect on the whitening process, this being attributable to the cleaning method. The major factor responsible for whitening is confirmed as a high water temperature irrespective of the presence of the denture cleaning agent. However, some physical properties were adversely affected by a high residual monomer content (due to the processing method) which has serious consequences for denture-wearing patients. The use of short/low temperature curing cycles now common in many dental laboratories should be avoided.

Acrylic Resins↗
PubMed1987

The use of computed tomography in the detection of radiolucent denture base material in the chest.

With the introduction of acrylic resin denture base materials to the dental profession, radiolucency was recognized as a significant deficiency at an early stage. Continuous research into the production of a radiopaque material has been directed at including radiopaque glasses, salts or metals powders in an otherwise radiolucent polymer. However, the majority of new dentures are still made in radiolucent material which is notoriously difficult to locate by conventional radiography and reports continue to appear relating to the inhalation or ingestion of dentures (or fragments of them), occasionally leading to the death of the patient. Advances in radiographic techniques and equipment have seen the development of computed tomography (CT). This has proved invaluable as a diagnostic aid for disease and therapy but little attention appears to have been given to the use of this sophisticated technique in the detection of foreign bodies, in particular those of dental origin. This study investigates the use of CT in the detection of radiolucent denture base material. The results suggest that CT has substantial advantages over conventional radiography in the detection of this material and should be considered as a valuable diagnostic aid in those patients thought to have inhaled dentures or fragments of dentures.

Acrylic Resins↗