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Biomedical subjects

B G Tidmarsh

Publications and source records attributed to B G Tidmarsh.

At least 19 recordsLinked to original sources
PubMed1994

Effect of storage media on subsequent water loss and regain by human and bovine dentine and on mechanical properties of human dentine in vitro.

This study was designed to determine whether storage media and time affect any changes in water loss with dehydration of dentine. The effect of storage of prepared bars was also compared with storage of whole teeth. Prepared bovine dentine bars were stored for 3 days or 12 weeks in deionized water, phosphate-buffered saline or neutral-buffered formalin and whole teeth were stored in neutral-buffered formalin for 12 weeks before the preparation of dentine bars. Specimens were removed from storage and weight loss with dehydration, determined gravimetrically, was equated directly to water loss. Tensile and three-point bend tests were made on human dentine bars that had been stored in deionized water or neutral-buffered formalin for 3 days. Results were subjected to analysis of variance and Duncan's new multiple-range test. Weight loss by evaporation from dentine at 22.3 degrees C and 53.2% relative humidity was rapid and non-linear, reaching 5.05 +/- 0.55% for bovine dentine compared with 3.33 +/- 0.63% for human dentine after 7 days. Water loss with dehydration was not affected by 3-day storage of specimens in different media or by 12-week storage of whole teeth, but was affected when prepared specimens were stored for 12 weeks. Different storage media had no significant effect (p > 0.05) on the strength or toughness of human dentine. Water loss in human dentine was associated with shrinkage of specimens, but these dimensional changes were fully recovered with rehydration. Storage of teeth in neutral-buffered formalin followed by minimal storage time for prepared specimens is recommended to minimize changes in dentine after extraction.

Animals↗
PubMed1993

The effects of dehydration and rehydration on some mechanical properties of human dentine.

This study was designed to investigate the effect of dehydration and rehydration on the brittleness and toughness of human dentine. Tensile and three-point bend tests were carried out on hydrated, dehydrated and rehydrated dentine bars, sectioned from sound extracted, human third molar teeth. The stress, strain and fracture energy (toughness) were calculated and the results were analysed using ANOVA and Duncan's multiple range test at p = 0.01. Stress at fracture did not differ significantly between hydrated, dehydrated or rehydrated dentine in bending or tensile tests. Strain at fracture and fracture energy were significantly greater for hydrated and rehydrated than for dehydrated dentine. In bending, the elastic energy (resilience) of dehydrated dentine was significantly greater than that of hydrated or rehydrated dentine, but dehydrated dentine showed no plastic energy (deformation) in contrast with the high values for hydrated and rehydrated dentine. Dehydration of human dentine resulted in decreased strain at fracture and demonstrated a brittle behaviour. The absence of plastic energy of deformation and the significantly reduced energy required to induce fracture were indicative of decreased toughness by dehydration. These changes were abolished after rehydration.

Body Water↗
PubMed1993

Simulation models for teaching endodontic surgical procedures.

Models which simulate oral conditions pertaining to endodontic surgical procedures are most suitable if they contain natural teeth and have hard and soft tissues which handle realistically. In addition, the model should possess radiological characteristics similar to bone. A simple custom-built model which fulfils these requirements is described.

Audiovisual Aids↗
PubMed1989

Dentinal tubules at the root ends of apicected teeth: a scanning electron microscopic study.

Two groups of teeth, one of which contained teeth of known age, were examined by scanning electron microscopy to ascertain the presence of a potential pathway for leakage at the root ends of apicected teeth. At a point approximately 3 mm from the apex, a level chosen as being typical for apicectomy, and half-way between the root canal and the dentine-cementum junction, there were found to be, on average, 27,000 tubules per mm2. Older teeth also displayed large numbers of tubules. Close to the dentine-cementum junction, an area which may communicate with the root canal even in the presence of a retrograde root filling, an average of 13,000 tubules per mm2 were found.

Dental Cementum↗
PubMed1987

Radiographic interpretation of endodontic lesions--a shadow of reality.

The radiographic interpretation of pathological lesions which are endodontic in origin is relatively imprecise as so many variables are involved. Even the presence or absence of a lesion cannot be determined with accuracy and there is little agreement on the criteria which should be applied. Strict attention to the technique of exposing, processing and viewing radiographs is necessary if the information to be gained is to be optimal. The major problem of visual interpretation and the psychological factors involved have been subjected to a certain amount of study and recent work on the mental processes of clinical decision making provide further insight. There is considerable promise being shown by methods of computer analysis and image enhancement and it may be that further development in these fields will provide the degree of objectivity that is essential if improved accuracy in diagnosis is to be achieved.

Bone Resorption↗
PubMed1986

Porous metal coatings for resin-bonding systems.

Two porous coating systems produced surfaces 20 to 30 microns thick, capable of engaging the unfilled component of composite during bonding procedures. A technique is suggested whereby the thickness of porous coating may be compensated by die spacing. The film thickness of the cement tested would be unlikely to affect the fit of any such prosthesis. Prostheses constructed in this manner would have the benefits of microretention without the technical problems of electrolytic etching.

Chromium Alloys↗