Biomedical subjects
Publications and source records attributed to J P Ralph.
Since restorative dentistry was established as a specialty in the UK in 1973, consultant appointments in the field have largely centred around the dental teaching hospitals with a considerable shortage of posts in the district general hospitals. This article explains the growing demand for restorative consultants and calls for the expansion of the hospital restorative dental service.
The views of general dental practitioners, practising in part of the Yorkshire Region, as to how they would cope with a variety of restorative problems were sought using a questionnaire. If advice or advice and treatment were to be requested from a consultant in restorative dentistry, the questionnaire was designed to discover whether the distance from a hospital created a barrier to the preferred course of action. Only one-third of the dentists were happy to treat a troublesome complete denture case, provide a replacement obturator or look after a natural dentition with considerable periodontal problems. Travel constraints were particularly apparent when it came to seeking help for the elderly edentulous patient. The results of the study indicate that in the Yorkshire Region, there is a high level of demand for consultant advice and treatment for a number of common restorative problems.
OBJECTIVES: This in vitro study aimed to examine the depth of preparation and incidence of dentine exposure resulting from the use of a 'freehand' technique to prepare maxillary central incisors for porcelain veneers. METHODS: Twenty-two maxillary central incisors were selected. Prior to preparation an index of the labial surface of each tooth was recorded and the tooth secured in a jig to permit accurate relocation. Two operators each prepared 11 teeth aiming to reduce the labial thickness evenly by 0.5 mm. Low viscosity silicone impression material was then placed on the index and the teeth relocated into the jig. Upon removal, this material was sectioned in the cervical, middle and incisal thirds of the tooth and its thickness measured using a toolmaker's microscope. The teeth were acid etched and also stained with a dentine dye to identify any area of dentine exposed during preparation. RESULTS: Significant differences (P < 0.001) in the depth of preparation at different sites, with least reduction in the mid-incisal region, were found. Greater reduction was found at the cervical and proximal margins with areas of dentine exposed at those sites in the majority of teeth. CONCLUSIONS: In view of the incidence and position of dentine exposure found in this study, the use of a dentine bonding system during the placement of porcelain veneers would appear essential when employing a 'freehand' preparation technique.
This evaluation was based on replies from a random sample of general dental practitioners who were asked to complete questionnaires before and after being sent a video and accompanying booklet on partial denture design. Forty per cent (257) of the original sample (636) completed and returned both questionnaires. A total of 212 respondents (82%) felt the video had been of value and 175 (68%) said they would be more likely to provide metal partial dentures after having watched it. The positive effects of the video were greatest amongst the most recently qualified. Despite some improvement after watching the video, there remained 105 (40%) who indicated that they would leave all partial denture design decisions to the technician on at least some occasions. Comparison of data from first and second questionnaires showed little evidence of substantial shifts in choice of denture design for a series of specific situations. It was concluded that whilst the programme had been well received and had produced changes in intention, there was less objective evidence of change.
Using glucose as a marker, a detailed study of retention at 5 different sites in the mouth of 1 subject and a less detailed examination of 4 selected sites in the mouths of 10 other subjects revealed site-specific differential patterns of oral retention (or clearance). These patterns seemed independent of sometimes large, absolute day-to-day variations in oral retention which occur in all subjects but appeared to vary somewhat between subjects, probably reflecting slight differences in the anatomy and physiology of the individual mouth. In general, the patterns resembled those recently derived from studies of other oral phenomena such as rates of diffusion out of plaque, fluoride uptake by mineral and hydrogen ion concentrations in plaque. They will dictate the concentrations and thereby influence the activity of all extraneous substances in different regions of the oral cavity and may relate to the site-specific patterns of oral disease.
As more people keep their teeth later in life, more and more patients in the future will still be partially dentate at an age when, previously, the edentulous state was the norm. The overdenture has a part to play in restorative dentistry for these patients. It can be a relatively simple, inexpensive prosthesis; but, like so many other aspects of dentistry, will provide long-term success only if the patient and the mouth have been assessed with care and a rigorous after-care programme instituted.
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After rinsing with a fluoride solution, the amounts of fluoride taken up by small pieces of dentine placed strategically about the mouth varied considerably from site to site in the oral cavity. The pattern of fluoride availability in this subject's mouth was in line with previous findings about fluoride distribution in his labial sulcus. The present results therefore suggest by analogy that considerable variations in fluoride clearance and concentration must exist throughout the oral cavity. These previous studies of fluoride clearance from the labial sulcus also showed that there are marked differences between individuals. The present findings, emerging from a study of 1 subject, therefore imply a need for more information about the variations in the availability, concentration and clearance of fluoride and, by extrapolation, of other substances throughout the mouths of different individuals.
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Even though the temporomandibular joint is loaded in function, it often arthroses under heavy use. The effects of stress to the joint are not well understood. This study utilized three-dimensional photo-elastic stress analysis to visualize the intensity and direction of stress within the mandibular condyle generated by various occlusal forces. Functional stress were shown to concentrate in the condylar neck, but were reduced within the condylar head due to its elliptical shape. Stress directions within the condyle were found to be non-preferential, varying with different mandibular positions. This supports the idea that the condyle is designed to receive light varied forces rather than heavy, cyclical unidirectional forces.