Biomedical subjects
Publications and source records attributed to R C Paterson.
A number of systems for the biological testing of dental materials have been suggested. This paper presents a critical review of the protocols suggested in the ISO standards for the initial and secondary biological testing of root canal sealing materials.
A number of systems for the biological testing of dental materials have been suggested. This paper reviews the protocols suggested in the ISO standards for the in-use or 'usage' tests for root canal sealing materials.
A series of studies has been conducted in which monoinfected gnotobiotic rats were used to study the responses of the dental pulp to micro-organisms isolated from carious lesions in dentine. In this study pulp responses to L. plantarum (formerly odontolyticus) (NCTC 1406) in pure culture and in combination with S. mutans (NCTC 10919) are reported. The incidence of inflammation/necrosis/dentine bridge formation observed in animals monoinfected with L. plantarum was similar to that reported in previous germ-free studies. There was a greater incidence of dentine bridge formation in rats monoinfected with L. plantarum compared with those monoinfected with S. mutans. When the two organisms were combined, periapical inflammation was observed in 14% of the teeth examined after 28 days, but there was no significant difference in the incidence of dentine bridge formation. Considerable variation in the density of staining of the two microorganisms in histological sections was observed.
The pulpal response to and cariogenicity of a third strain of Streptococcus mutans, namely S. mutans (NCTC 10832), was studied in monoinfected gnotobiotic rats of the Fischer strain using the techniques described previously by the present authors. Unlike S. mutans (NCTC 10449 and 10919), S. mutans (NCTC 10832) was associated with the presence of inflammatory cell infiltrates in the coronal pulp of a small number of teeth and extensive periapical inflammation 28 days after the creation of untreated pulpal exposures. S. mutans (NCTC 10832) was associated with the presence of extensive pulpal necrosis and reduced dentine bridge formation. These changes were similar to those noted with the other two strains of S. mutans. S. mutans (NCTC 10832) was non-cariogenic in monoinfected gnotobiotic rats of the Fischer strain.
This paper describes the development of a printed distance learning programme by a coordinated team approach. The programme has two components, a resource book and three patient management problem leaflets or challenges and is designed to update general dental practitioners on the management of fissure caries. It includes strategies to meet the educational needs of three groups of general dental practitioners with different educational requirements. It is concluded that the approach described meets the CRISIS criteria for effective continuing education and offers a useful approach to distance learning in dentistry.
This is the third of a series of articles reviewing the current knowledge on bonding systems. In the two previous papers the nature of the dentine smear layer and the preparation of the dentine surface for bonding were considered. This article reviews the current knowledge of the mechanisms of dentine bonding and presents a summary of the composition and mode of action of some of the more recent proprietary bonding systems.
A postal/telephone survey of 452 general practitioners working in the Greater Glasgow and Lanarkshire Health Board areas was carried out between March and June, 1989. The aim was to investigate the use of sealant restorations under section 6 of the National Health Service fee scale for general dental practitioners. Section 6 itemizes fees for fissure sealant, glass-ionomer cement plus sealant, composite resin plus sealant and the laminate restoration. A response rate of 83% was obtained. Eighty-one per cent of the respondents were placing sealant restorations, but less than half were using the laminate or sandwich technique. A wide variety of materials and curing lights were employed. Enamel etching times varied considerably and rubber dam was seldom used. Eighty-nine per cent indicated that they would welcome illustrated fact sheets demonstrating the use of sealant restorations.
In these two papers the nature of the smear layer will be considered first. The clinical management will then be discussed, and finally, preparation of the dentine surface to receive the new bonding systems will be considered. A subsequent paper will discuss bonding agents.
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Gnotobiotic rats mono-infected with Streptococcus mutans (NCTC 10919) were maintained on a high sucrose diet in an isolator. When they were 8 weeks old the pulps of their maxillary first and second molars were mechanically exposed and left open to the oral environment. The rats were sacrificed in groups after 7 and 28 days. Thirty-seven teeth were available for study in the 7-day group, and 30 teeth in the 28-day group. The test S. mutans was non-cariogenic. After 7 days, necrosis of the superficial layers of the pulp was noted; however, after 28 days pulpal necrosis was much more extensive and calcific repair was observed in only one-third of the teeth examined. The microorganism did not provoke inflammation in the pulp or periapical tissues. This is the second strain of S. mutans tested in this manner. These results are very similar to those reported previously for S. mutans (NCTC 10449) and strengthens the view that organisms of the S. mutans group have a low pathogenicity for the pulp.
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This study investigates the validity of the treatment decisions made by 10 hospital dentists, who examined the fissures of extracted teeth using a visual-only technique. The study shows that 8 of the 10 dentists were more likely to leave carious teeth unrestored than unnecessarily treat sound teeth. The authors suggest that this system of diagnosing occlusal caries is a satisfactory one in terms of its sensitivity and specificity.
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Using gene-specific probes derived from four mouse gamma-crystallin cDNAs, we have examined the regulation of different members of the mouse gamma-crystallin gene family during lens development. Our analysis revealed that, while the different gamma-crystallin genes appear to be coordinately activated during embryogenesis, the steady-state levels of their corresponding transcripts are differentially regulated, resulting in variations in the relative abundance of individual species at different stages of development. This complex pattern of gene regulation presumably accounts for one of the mechanisms determining the spatial distribution of different gamma-crystallins within the lens.
The maxillary molar pulps of germ-free rats were mechanically exposed, and suspensions of a strain of freshly grown Streptococcus mutans were applied to the pulp wounds. The pulps were left open to the oral environment, and the animals were maintained in the isolator until they were killed in groups after 2, 7, and 28 days. After 2 days there was little evidence of any pulp response. In the 7-day group early pulp necrosis was present. No evidence of inflammatory infiltration was detected in either the 2- or 7-day animals. After 28 days there was extensive pulp necrosis in many specimens. Dentine bridges were present in fewer than one fourth of the teeth.
The maxillary molar pulps of germ-free rats were mechanically exposed and suspensions of a strain of freshly grown Lactobacillus casei were applied to the pulp wounds. The pulps were left open to the oral environment, and the animals were maintained within the isolator until death. In the majority of teeth, pulp necrosis was evident and apical inflammation was present in 40% of the specimens. The remaining monoinfected animals were bred and the litters were placed on a 46% sucrose diet to determine the cariogenicity of the test strain of L. casei in the mandibular molars. The organism proved to be noncariogenic. The effects of mechanical exposure of the maxillary molars in these animals were similar to those observed in the direct-inoculation study, with the exception of a reduced incidence of apical inflammation.
Three materials, which had been previously found to be toxic when applied as pulp-capping agents in conventional rat molar pulps, were retested in germ-free rats. All produced much more favorable responses in the pulp, with a lack of inflammation and the presence of dentine bridges in the majority of teeth. It appears that much of the pulp damage previously attributed to the chemical toxicity of materials may be caused by the presence of bacteria. The design of studies intended to evaluate the response of the pulp to materials should include staining techniques that will detect the presence of bacteria on the floors of test cavities.
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