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Biomedical subjects

J W O'Hara

Publications and source records attributed to J W O'Hara.

15 recordsLinked to original sources
PubMed1990

The caries status of occlusal amalgam restorations with marginal defects.

The purpose of this study was to examine histologically occlusal amalgam restorations with both defective and sound margins for comparison of their caries status. Thirty extracted teeth with occlusal amalgam restorations were sectioned so that a ditched and a clinically sound margin could be examined on the same tooth in the mouth. Histological examination showed a low prevalence of caries lesions in the outer enamel. However, lesions were present in the enamel of the cavity wall in 54% of specimens, whether the margin was defective or sound. If the results of this study are applicable to all occlusal amalgams with defective margins, it would appear that a defective margin alone is not an indication that a restoration needs to be replaced.

Dental Amalgam↗
PubMed1990

Practical considerations concerning glass ionomer cements used for basing amalgam restorations.

Despite the intense interest in composite resins, amalgam is still the direct restorative material of choice in posterior teeth where there are significant occlusal forces. The criteria for basing an amalgam are ill-defined, and the research regarding the use of cavity varnish is equivocal. The purpose of this article is to examine the clinical characteristics of six glass ionomer cement materials, currently being marketed as base/liner materials, when used for basing amalgam restorations. It is not the purpose of this article to set criteria for use of a base.

Color↗
PubMed1976

Carcinoma of the nasopharynx and nasa fossa: report of case.

A brief history of a case of nasopharyngeal carcinoma is described. A general discussion of the problems of diagnosis, treatment, and classification of the more frequent histologic type is presented. Currently, the most favorable prognosis is in patients in whom the condition is detected early. This serious disease sometimes occurs near or adjacent to the area of the dentist's primary responsibility. The dentist should always assume his professional responsibility by promptly referring any patient with suspected cancer to an appropriate specialist.

Adult↗
PubMedDate not supplied

Comparison of marginal adaptation between direct and indirect composites.

The evaluation of composite resin as a posterior restorative material has been slow and attended by several problems. Gap formation has been considered a serious problem by many researchers. The purpose of this in vitro study is to compare the marginal adaptation of posterior composite resins placed by a direct method with those placed by an indirect method utilizing flexible dyes. Conclusions drawn from the results of this study are that both techniques produced marginal gaps. Also there were no differences in the width of marginal gaps in the composite resin restorations placed by our direct or indirect methods, and no marginal gap differences were observed as a result of anatomical location.

Analysis of Variance↗
PubMedDate not supplied

Strength of posterior composite repairs using different composite/bonding agent combinations.

Posterior composites are becoming a viable alternative to amalgam in selected cases. As the use of posterior composites increases, the necessity of repair of fractured, discolored, or worn restorations will increase. A number of studies have demonstrated that clinically acceptable repairs can be obtained for anterior composites. This study examined the bond strength of repairs made to aged posterior composite substrates when different bonding agent/composite pairs were used. Dentin bonding agent/composite pairs gave the highest bond strengths and were greater than the bond strength of resin to etched enamel. An enamel bonding agent/composite repair gave the lowest bond strengths, which were less than resin/etched enamel bond strengths.

Analysis of Variance↗