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Biomedical subjects

W R Hume

Publications and source records attributed to W R Hume.

At least 19 recordsLinked to original sources
PubMed1991

An SEM study of the effects of different irrigation sequences and ultrasonics.

The root canals of 30 extracted human teeth with single canals were prepared biomechanically with hand instruments using a flaring technique. Three different irrigation regimes were used, with and without ultrasonic activation of a root canal file. The six irrigation sequences used in this study were as follows: Savlon, Savlon with ultrasound, EDTAC/NaOCl/EDTAC, EDTAC/NaOCl/EDTAC with ultrasound, NaOCl/EDTAC/NaOCl, and NaOCl/EDTAC/NaOCl with ultrasound. Scanning electron microscopic (SEM) examination of the prepared root canal walls showed a complete smear layer when Savlon was used. Ultrasound reduced the amount of smear with Savlon, but did not do so significantly with the other irrigation regimes. The most effective irrigation regime for removing smear layer and other debris was EDTAC/NaOCl/EDTAC. In all groups there was a significant decrease in cleaning efficiency as the apical end of the canal was approached.

Cetrimonium Compounds↗
PubMed1990

Clinical behaviour of high-copper amalgams with time, site, size and class of cavity preparation.

In this study 767 amalgam restorations placed in the posterior permanent teeth of 122 patients were evaluated at 6-monthly intervals up to 2 years. Six commercially available high-copper alloy amalgams were assessed for surface roughness, surface tarnish, marginal staining and marginal fracture and the results were related to product, restoration age, restoration cavity class type, restoration size (normal or large Class II preparations) and tooth type (premolar or permanent molar). Dispersalloy (Johnson and Johnson, East Windsor, USA) gave restorations which were overall superior for the clinical characteristics examined. Large restorations on the occlusal surfaces of molar teeth showed more signs of deterioration over the study than did other restoration types. However, all restorations remained clinically satisfactory throughout the study.

Analysis of Variance↗
PubMed1990

Keeping the pulp alive: the pharmacology and toxicology of agents applied to dentine.

Materials applied to teeth release chemicals which may diffuse through dentine to either harm or help the dental pulp. Chemical threats are minimized by material choice or by using relatively impermeable lining or base materials which are themselves of low chemical toxicity. The most probable long-term threat to the pulp in the restored tooth is bacterial, through leakage around restorations. This may be prevented by the use of treatment sequences designed to develop an effective seal. Pulpal inflammation is treated primarily by removal of the irritant cause; inflammation may also be suppressed in the very short term by corticosteroids, and its resolution aided in the longer term by zinc oxide-eugenol preparations.

Demeclocycline↗
PubMed1990

Antibiotics and endodontics.

Antibiotics can be used as an adjunct to endodontic treatment in a number of ways--locally, systemically and prophylactically. The local or intra-canal use of antibiotics in the form of medicaments is common. However, the commercially available agents for this purpose may not be the ideal mixtures. Systemic antibiotics should be restricted to patients who have local signs of infection, malaise and elevated body temperature. Prophylactic use of antibiotics has been recommended for patients 'at risk' of infective endocarditis, in some pre-surgical situations and following avulsion and replantation of teeth. The tendency towards indiscriminate antibiotic use should be discouraged. The use of broad spectrum drugs should be restricted so that these medications remain effective in serious situations.

Anti-Bacterial Agents↗
PubMed1989

The release and diffusion through human coronal dentine in vitro of triamcinolone and demeclocycline from Ledermix paste.

Crowns from freshly extracted human third molar teeth were used to quantify the release and diffusion of corticosteroid and antibiotic tracer molecules from Ledermix paste used as an indirect pulp-capping agent. These molecules readily diffused through dentine and reached a peak rate of diffusion at 2 h. The rate then decreased exponentially with time. The concentrations of the drugs in the dentine were calculated; this showed that a gradient existed from the cavity floor to the pulp space. The data obtained appeared to have clinical relevance and helped explain the therapeutic benefits of this medicament when used as an indirect pulp-capping agent.

Adolescent↗
PubMed1989

Barriers to diffusion of Ledermix paste in radicular dentine.

Freshly extracted human single-rooted teeth with a single root canal were used to study the effects of 2 irrigation regimens and the effect of cementum on the diffusion of corticosteroid and antibiotic tracer molecules from Ledermix paste placed in the pulp space. An irrigation regime that combined the use of 15% EDTAC and 1% NaOCl resulted in a significant increase in the permeation of the trace molecules through dentine compared with teeth that were irrigated with Savlon solution. Mechanical removal of the cementum also resulted in a significant increase in the permeation of the trace molecules. This study demonstrated that neither the smear layer nor the cementum were complete barriers to diffusion. The data obtained appeared to be of clinical relevance and provided further understanding of the dynamics of drugs in tooth roots.

Adult↗
PubMed1989

Effects of combining Ledermix and calcium hydroxide pastes on the diffusion of corticosteroid and tetracycline through human tooth roots in vitro.

A 50:50 mixture of a corticosteroid/antibiotic paste and calcium hydroxide has been used clinically as a root canal dressing agent. This study investigated the effect on the release and diffusion of the corticosteroid and antibiotic components of Ledermix paste when it was mixed with a calcium hydroxide-methyl cellulose paste. The release rates of the trace molecules were lower when the mixture was used compared with release from Ledermix alone. The results indicated that this combination of materials, when used a long-term intracanal dressing, was likely to be more effective than Ledermix alone.

Calcium Hydroxide↗
PubMed1989

The effect of varnishes and other surface treatments on water movement across the glass ionomer cement surface. II.

The aesthetic restorative glass ionomer cements undergo a rather prolonged setting reaction during which time they are susceptible to water uptake and water loss. If they can be maintained in isolation long enough in the oral cavity then the clinical result will be superior. A further series of surface treatments has been tested and it has been shown that immediate covering of the immature glass ionomer cement surface with light-activated bonding resin is the most effective method of limiting water movement across the surface. This restriction of water movement is not effective for all light-activated bonding resins suggesting that there may be a physico-chemical interaction occurring on the glass ionomer cement surface with certain of the resins.

Composite Resins↗
PubMed1988

In vitro studies on the potential for pulpal cytotoxicity of glass-ionomer cements.

Elution samples of glass-ionomer cement were prepared in sterile tissue culture medium either by direct contact between the fluid and standard cement samples or through a layer of human dentin, and then tested for toxicity to cultured mouse fibroblasts (L929). The directly-prepared eluates of the cements were highly cytotoxic, but those prepared through dentin were of either limited or no cytotoxicity. The degree of toxicity of some directly-prepared eluates was reduced by adjustment of the pH to neutrality. It was apparent that dentin reduced the potential for cytotoxicity of glass-ionomer cements to a large degree. Proposed mechanisms for the reduction were limited availability of water at the dentin-cement interface and thus limited dissolution of components, buffering of acid components of the cements by dentin, or other chemical interactions with dentin.

Adolescent↗