Oxygen and pH-sensitivity of human osteoarthritic chondrocytes in 3-D alginate bead culture system.

OBJECTIVE: To identify the effect of alterations in physical parameters such as oxygen and pH on processes associated with cellular redox balance in osteoarthritic chondrocytes. METHOD: Human osteoarthritic chondrocytes (HOAC) were isolated from total knee arthroplasty samples and cultured in 3-D alginate beads in four different oxygen tensions (<1%, 2%, 5% and 21% O2), at pH 7.2 and 6.2 and in the presence or absence of 10 ng/ml, interleukin-1ß (IL-1ß). Cell viability, media glycosaminoglycan (GAG) levels, media nitrate/nitrate levels, active matrix metalloproteinase (MMP)-13 and intracellular adenosine triphosphate (ATPi) were measured over a 96-h time course. Intracellular reactive oxygen species (ROS), mitochondrial membrane potential, intracellular pH and reduced/oxidised glutathione (GSH/GSSG) were additionally measured after 48-h incubation under these experimental conditions. RESULTS: Hypoxia (2% O2) and anoxia (<1% O2), acidosis (pH 6.2) and 10 ng/ml IL-1ß reduced HOAC cell viability and increased GAG media levels. Acidosis and IL-1ß increased nitrite/nitrate release, but increases were moderate at 2% O2 and significantly reduced at <1% O2. ATPi was significantly reduced following hypoxia and anoxia and acidosis. At 48 h cellular ROS levels were increased by acidosis and IL-1ß but reduced in hypoxia and anoxia. Mitochondrial membrane potential was reduced in low oxygen, acidosis and IL-1ß. Anoxia also resulted in intracellular acidosis. GSH/GSSG ratio was reduced in low oxygen conditions, acidosis and IL-1ß. CONCLUSIONS: This study shows that oxygen and pH affect elements of the redox system in HOAC including cellular anti-oxidants, mitochondrial membrane potential and ROS levels.

The determination of toxic metals in simulated stomach contents by energy dispersive X-ray fluorescence analysis and a fatal case of mercury poisoning.

Soup is used as a simulated stomach contents matrix to determine the lower level of detection for 16 metals. All of the metals can be detected at the levels which might be expected for acute fatal doses even if the stomach contents are considerably diluted. However where small doses are administered over a prolonged period this method may not be sufficiently sensitive. A case of fatal poisoning by the ingestion of mercuric chloride is described to illustrate the effectiveness of the method. In this case mercury was also detected and determined at highly significant levels in blood and liver by the same technique. This energy dispersive X-ray fluorescence (EDXRF) method is easy to use, rapid and non-destructive.

The height of occlusal registration blocks before and after jaw registration.

OBJECTIVES: To assess the height of occlusal registration blocks made in dental laboratories compared with recommended dimensions. To relate these dimensions to the height of the blocks after registration of the occlusion. METHODS: All occlusal registration blocks received in a complete denture clinic at the Charles Clifford Dental Hospital, Sheffield, over a 1-year period were measured in height before and after registration of the occlusion. RESULTS: The height of occlusal registration blocks as received corresponded to the recommendations in the literature. However, after registration, a significant reduction in height was seen for both maxillary and mandibular blocks. CONCLUSIONS: Occlusal registration blocks produced by laboratories are 34 mm too high, requiring removal of excess wax in the surgery.

Report on the Annual Conference of the British Association of Teachers of Conservative Dentistry.

The Annual Conference of the British Association of Teachers of Conservative Dentistry (BATCD) was held in Sheffield on 16 and 17 September 1993. The main programme addressed educational issues in three areas: the undergraduate/vocational-trainee interface, the teaching of implants in the undergraduate curriculum, and the changing role of dental instructors in restorative dentistry. The programme also included a number of research papers and poster demonstrations, which were submitted for the Association's new QED/Maillefer prizes in Restorative Dentistry. This paper presents reports of the four principal lectures, and abstracts of the research papers and poster demonstrations, with details of the prize winners.

The laboratory construction and teaching of ceramic veneers: a survey.

OBJECTIVE: The aim of this study was to identify current trends in the methods and materials used during teaching and construction of ceramic laminate veneers within the laboratory. METHOD: A questionnaire was designed to determine the most popular laboratory techniques and materials used during the teaching and construction of ceramic veneers at a number of university dental schools and teaching hospitals in the United Kingdom, Ireland and Hong Kong, and to identify the role of technical staff. RESULTS: The responses showed that approximately 63% of teaching hospitals and 53% of dental schools were involved with either the construction or teaching of laboratory techniques for ceramic veneers. Of two substrate materials identified, it was clear that the use of phosphate refractory models was preferred to the platinum foil technique. A wide range of refractory and ceramic materials was reported, some of which were supplied as combined system products. However, a larger number were ceramics and refractory materials acquired from independent manufacturers and therefore not necessarily matched. CONCLUSION: Although clear information was provided by the manufacturers to identify the thermal expansion coefficient of their dental ceramic, this is not the case for most of the phosphate refractory materials. As a result, intermixing of individual ceramic and refractory products was commonplace with some combinations having different thermal expansion coefficients. To avoid this thermal mismatch, clear information relating to both products needs to be provided by the manufacturers.

The DERWeb project--dental education resources on the Internet.

The delivery of dental education, in common with other forms of higher education, has altered considerably over the last decade. The introduction of the World Wide Web enabled resources for dental education to be delivered in a new and innovative manner. DERWeb was funded by HEFC-JISC. The primary resource consists of a library of 1600 clinical dental images each with keywords and a description. Selected images were used to create teaching materials to demonstrate to dental educators world wide how the image library could be used by individual institutions. Hands-on courses were held to demonstrate the new resource and to evaluate computer skills in the dental community. Since the commencement of the project in September 1994 DERWeb has become one of the leading resources for dental education world wide. The site has been accessed by 79 countries with approximately 107000 accesses in October 1996. DERWeb also designs and maintains the British Dental Association pages together with other professional organisations. Its resources also include dental contact addresses and links to quality dental sites world wide. Further funding has enabled DERWeb to expand further and explore new technologies to develop interactivity on the Web.

The introduction of dental team education.

An initial experiment of introducing trainee dental nurses to assist dental undergraduates for one session a week has led to the introduction of dental team education within the department of restorative dentistry, University of Sheffield. At the same time, self-directed and problem based learning was introduced for the team. This article outlines the development and results of the exercise.

The quality of impressions for crowns and bridges received at commercial dental laboratories.

OBJECTIVE: To determine the quality of impressions for crown and bridge work made in general dental practice. DESIGN AND SETTING: All impressions for crown and bridge work which had been sent to four commercial dental laboratories in the UK were assessed by two examiners, each laboratory being visited on two occasions. MATERIALS AND METHODS: 290 cases which had been received by the laboratories on the days of the visits were assessed for a number of factors related to quality. There was no selection or rejection--all impressions received were examined. RESULTS: Flexible plastic trays were used for the majority of working impressions for crown and bridge work in general dental practice (72%), many had been re-used (> 13%), defects in the recording of the prepared teeth were common, and cross infection control was not routine. CONCLUSIONS: Quality standards for impressions for crown and bridge work in general dental practice in the UK are a cause for concern if the sample of cases seen in this study is typical.

The influence of the impression tray on the accuracy of impressions for crown and bridge work--an investigation and review.

OBJECTIVE: To evaluate the accuracy of working casts for crown and bridge restorations made from twin mix putty/wash silicone elastomeric impression materials using different types of stock tray. DESIGN: A master cast was made from ivorine teeth in a mandibular model. Three teeth were prepared for full crown restorations to simulate a single unit and a three unit bridge. Impressions were taken using four different types of impression tray and two different viscosities of silicone putty, together with a wash. Full metal crowns were constructed and seated on duplicate master casts and measurements made of the marginal discrepancies. SETTING: The work was carried out in a dental technology laboratory in a university department of restorative dentistry in 1995/1996. RESULTS: Metal and rigid plastic impression trays showed the least discrepancy (about 50 microns), the latter slightly greater with the normal putty than the soft one. Impressions taken with flexible plastic trays produced considerable discrepancy with both putties, approximately 210 microns and 180 microns respectively. CONCLUSIONS: Metal and rigid plastic stock trays give greater accuracy in the putty/wash silicone twin mix impression technique compared with flexible plastic ones for crown and bridge work. Those using the latter should be aware of their shortcoming in this respect.

A study of the quality of impressions for anterior crowns received at a commercial laboratory.

A report is presented of a study which was carried out to investigate the standard of impressions for anterior crowns received at a commercial dental laboratory in Great Britain. Aspects examined were the type of tray and its suitability to the impression technique used, fixation of the impression to the tray, the method of storage in transit, contamination, defects on the preparations and defects elsewhere affecting the occlusion. The quality of the actual preparation was not examined in this study. Similar details were noted for the opposing impression. Of the 50 cases examined only 12 were recorded as totally satisfactory, with 26 cases being recorded as not being of an acceptable standard for the construction of an adequate restoration. The results are presented with the conclusion that in this survey the general quality of impression was unacceptable.

Metal-ceramic bridges from commercial dental laboratories: alloy composition, cost and quality of fit.

The quality of construction of fixed bridge prostheses directly affects their long-term survival. The cost, alloy composition and marginal fit of bridges made by 30 commercial dental laboratories is assessed. Duplicate models of a three unit bridge preparation were sent to 30 different laboratories, as if required for a patient receiving treatment under the General Dental Service. Material was sent via general dental practitioners, requesting metal-ceramic bridges made from 45% Au alloy, precious metal or non-precious metal. Proximal contacts were overbuilt at 65% of sites and pontic tissue contacts were excessive in all but one bridge. Eight laboratories did not use alloys corresponding to the request made. The mean marginal gaps of non-precious metal bridges (145 microns) were significantly greater than those for 45% gold alloy (106 microns). Marginal fit was poor and a number of factors have been observed, with other postulated, which may have contributed to this problem.

The use of sutures in the mouth.

The purpose of this communication is to establish a case for a more critical review of the indications for the use of sutures in oral surgery. Observations are made on the underlying principles of surgery and, where appropriate, modifications to suit some standard surgical techniques including apicectomy are suggested, which will reduce both the post-operative inconvenience for the patient and the indications for suturing. The case is supported by a retrospective review of the sutures used in a consecutive series of 149 oral surgery patients admitted to hospital for operation under general anaesthesia.

The management of fractures of the mandible.

In some countries there is a move away from the traditional use of predominantly closed or semi-closed procedures in the management of facial fractures to widespread use of aggressive surgical techniques. Observations are made on the effect that this trend may have on the trainee Oral Surgeon. An analysis of a series of 156 consecutive cases of mandibular fracture bears out the impression that simple jaw support, when there is patient co-operation, is adequate for the treatment of the majority of mandibular fractures and that when fixation is indicated, the eyelet wiring technique gives excellent results without complicating management. When open operation is indicated, intraosseous wire suture is proposed as a convenient method for first consideration. The necessity to determine accurately the pre-accident occlusion in cases of possible malocclusion is underlined and a plea is made to exercise patience in the management of fractures, particularly when the condylar neck is involved.

Crown and bridge impressions--a comparison between the UK and a number of other countries.

The quality of impressions for crown and bridge work in seven countries were compared with the results found in the United Kingdom in a previous study. The results showed that metal impression trays were used more frequently, and flexible plastic trays less frequently, in the countries visited than in the United Kingdom. Other differences and similarities were noted.

Dimensional change of refractory materials used for ceramic veneers.

The current literature considers a number of clinical factors which affect the fit of all-ceramic laminate veneers. However, little consideration has been given to the refractory die materials, and the laboratory techniques used during the construction of these restorations. This study found a wide range of dimensional change occurred during setting and through six firing cycles, for seven refractories recommended for the construction of laminate veneers. It is therefore important that where patient treatment involves the use of veneers the clinician considers the suitability of the materials offered by the laboratory, in order to obtain the optimum marginal integrity.

Lifelong education and the dental profession.

Provision of education is constantly under review, with regular changes to address new needs. In addition, demands that cannot be met from within initial training courses have spawned a plethora of educational courses to update knowledge and develop new skills--in effect promoting lifelong education. The aim of this paper is i) to define and explain commonly used educational terms relevant to the understanding of lifelong education, ii) to make a distinction between lifelong education and continued education, and iii) to offer a rationale for the increasing importance of lifelong education for the dental profession.