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Biomedical subjects

J C Rodda

Publications and source records attributed to J C Rodda.

At least 19 recordsLinked to original sources
PubMed1999

Barodontalgia: a review, and the influence of simulated diving on microleakage and on the retention of full cast crowns.

This paper reviews the causes of barodontalgia and reports on a study that indicates a possible cause of barodontalgia in the diver. In the study, extracted teeth had full cast crowns cemented with either a zinc phosphate, a glass ionomer, or a resin cement, and simulated diving to 30 m (3.0 atmospheres) was performed. During simulated diving, the teeth were pressure cycled 15 times to 3 atmospheres and microleakage was monitored. The force required to dislodge the crown was then tested; a significant difference was found between the zinc phosphate and the glass ionomer cement groups (p < 0.01). No difference was found between the resin cement groups. Microleakage was also detected in the zinc phosphate and glass ionomer cement groups and was found to occur sooner, and to a greater extent with zinc phosphate. No microleakage was detected in the resin cement experimental group. This study showed that the retention of full cast crowns to extracted teeth is reduced after pressure cycling and that microleakage does occur if the crowns are cemented with either zinc phosphate cement or glass ionomer cement.

Barotrauma↗
PubMed1997

The effect of environmental pressure changes during diving on the retentive strength of different luting agents for full cast crowns.

STATEMENT OF PROBLEM: The effect of pressure cycling on the bond strength of cement luting agents is largely unknown. PURPOSE: This study investigated the effect of pressure cycling on the retention of full cast crowns to extracted teeth. MATERIAL AND METHODS: Sixty extracted single-rooted premolar teeth had full cast crowns cemented, 20 with a zinc phosphate cement, 20 with a glass ionomer, and 20 with a resin cement. After 7 days of storage, each of the teeth in the experimental groups was pressure cycled 15 times from 0 to 3 atmospheres (304 KPa), after which the force required to dislodge the crowns was tested in an Instron testing machine. RESULTS: A significant difference was found (Students t test; p > 0.01) between the force required to remove the crowns in the zinc phosphate control (142.10 +/- 36.42 N) and experimental (15.93 +/- 11.13 N) groups and the glass ionomer cemented control (186.33 +/- 24.33 N) and experimental (91.50 +/- 33.07 N) groups; no difference was found between the resin cemented control (291.15 +/- 78.48 N) and experimental (281.32 +/- 85.43 N) groups. CONCLUSION: This study showed that the retention of full cast crowns to extracted teeth is reduced after pressure cycling if the crowns are cemented with either zinc phosphate cement or glass ionomer cement. Dentists should consider using a resin cement when cementing crowns and fixed partial dentures for patients, such as divers, who are likely to be exposed to pressure cycling.

Air Pressure↗
PubMed1993

The protein of pigmented Polynesian dental enamel.

This enamel contained 1.4-3.7% protein, calculated from amino acid residues, in which glutamic acid and leucine were the most generally abundant and lysine was the most abundant basic amino acid. The amino acid profiles of both French Polynesian and Maori pigmented enamel protein were similar and closely resembled that of tuft protein and certain non-amelogenins. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of extracts of pigmented enamel showed an absence of amelogenin protein and the presence of two principal proteins at M(r) 55,000-66,000, indicating that the protein of pigmented Polynesian enamel was non-amelogenin. This contrasts with hypomaturation amelogenesis imperfecta in which the protein has the amino acid profile of amelogenin.

Adolescent↗
PubMed1992

The oral health and attitudes to dental treatment of a dentate elderly population in Mosgiel, Dunedin.

As part of the Mosgiel Community Study, a longitudinal investigation of the health of the elderly, a dental survey was used to determine the oral health status and treatment needs, both objective and subjective, of a group of dentate older adults. Sixteen percent of the 817 subjects were dentate. Of these, 95 were available for the dental survey, and they were questioned and examined at their homes. The mean age was 77 years, and 55 percent of subjects were male; disproportionately more older males than females had retained some of their natural teeth. Seventy-two percent regularly sought dental treatment, and 39 percent felt they were in need of treatment. Few real barriers to treatment were identified, although a major obstacle preventing many from seeking treatment was their lack of perceived need. However, even the realisation that they required treatment was not sufficient cause for many to seek treatment. All subjects required some form of dental treatment. Eighty-five of the 95 subjects required at least one restoration, and 16 percent advanced restorative treatment. The frequencies of coronal and root surface caries were similar. Oral mucosal pathology was also common. Sixty-five percent of denture wearers required prosthetic treatment. Most subjects needed simple periodontal treatment, but 11 percent required advanced therapy. The main oral health problems of this group related to the simple management of plaque-related disease, and the wearing of dentures. However, 24 percent of people required complex restorative and periodontal treatment, or both.

Aged↗
PubMed1989

The polarized light microscopy and ultrastructure of Polynesian pigmented tooth enamel.

Transmitted and polarized light microscopy of unerupted and erupted teeth affected by a pigmented anomaly found in two geographically isolated Polynesian populations, the New Zealand Maori and the French Polynesian Marquesas Islander, showed similar histological characteristics. Mounted in water, the pigmented areas were positively birefringent and covered with a thin negatively birefringent surface layer 200-250 microns thick. Cervical areas were negatively birefringent. Transmission electron microscopy of argon-ion-beam thinned specimens of affected enamel revealed large voids, disruption in the packing of crystals and spacing at prism boundaries. In the surface layer of enamel from erupted and unerupted teeth, the intra- and interprismatic spaces were occluded by fine crystals or amorphous material. A well-defined prism structure and close crystal packing were found in cervical enamel. The ultrastructure of these pigmented enamels was similar to and consistent with a hypomaturation type of amelogenesis imperfecta.

Birefringence↗
PubMed1988

Artificial caries around restorations in roots.

An artificial caries technique was used to produce caries-like lesions in the cavity walls adjacent to microfilled resin restorations with and without dentin bonding agent, and glass-ionomer cement restorations, in the roots of extracted teeth. The lesions had histological characteristics similar to those of natural lesions and to those of the lesions produced by other experimental methods. The zonal pattern of the lesions was examined by means of polarized light microscopy and microradiography, and the depth of the lesions was measured for assessment of the microleakage around the restorations. Three cavity cleaning regimes-water spray alone, 50% citric acid, and a proprietary cleaner-were compared in conjunction with the three restorative methods. Cavity cleaning with the citric acid or the proprietary cleaner, and the use of a fluoride-releasing restorative material, acted to reduce the depths of the lesions. Glass-ionomer cement restorations in cavities cleaned with citric acid showed lesions significantly shallower than those treated with other restorations. The glass-ionomer cement was soluble in the acidic environment but promoted the precipitation of minerals in the lesions. The use of a dentin bonding agent did not affect the depth of demineralization around the microfilled resin restorations.

Adhesives↗
PubMed1975

Colour television image analysis of carious lesions.

The new technique of colour television image analysis has been used to produce seven-colour contour maps of the radiodensity of micro-radiographs of enamel caries. This method permits the detailed measurement of the mineral content of enamel carious lesions to a sensitivity of +/-3% of the level of complete mineralisation. By selection of appropriate aluminium step-wedges, exposed simultaneously with the tooth section, the whole range of mineral content can be assessed.

Calcium↗
PubMed1971

Why hydrology ?

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News↗