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.

An appraisal of the literature on centric relation. Part III.

The literature directly and indirectly related to centric relation (CR) has been reviewed chronologically. More than 300 papers and quoted sections of books have been divided into three sections. The first two parts are related to CR. Studies in this group mainly compared, either the position of the mandibular condyle or the mandible itself in different CR recordings. Various tools were discussed for this purpose. The third part of the paper is about CR-centric occlusion (CO) discrepancy. CR still remains one of the controversial issues in prosthodontics and orthodontics. Debates such as mounting casts on the articulator by reproducible records for orthodontic treatment planning and end results, and whether or not orthodontic treatment based on CO causes TMJ dysfunction, remain unsolved. The references are listed at the end of Part III.

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.

An appraisal of the literature on centric relation. Part I.

The literature directly and indirectly related to centric relation (CR) has been reviewed chronologically. More than 300 papers and quoted sections of books have been divided into three sections. The first two parts are related to CR. Studies in this group mainly compared either the position of the mandibular condyle or the mandible itself in different CR recordings. Various tools were discussed for this purpose. The third part of the paper is about CR-centric occlusion (CO) discrepancy. CR still remains one of the controversial issues in prosthodontics and orthodontics. Debates such as mounting casts on the articulator by reproducible records for orthodontic treatment planning and end results, and whether or not orthodontic treatment based on CO causes temporomandibular joint dysfunction, remain unsolved. The references are listed at the end of Part III.

Intercondylar width as a guide to setting up complete denture teeth.

A clinical study was designed to investigate the relationship between intercondylar width (ICW) and inter-dental widths of the upper and lower canines and first molars to aid in denture teeth positioning. The study was divided into two parts so that the results of the first part could be verified in the second part. In the first part, 27 adult subjects were selected according to the exclusion criteria of the study. A kinematic hinge axis locator was used to locate the true point of condylar rotation. The distance between these points was considered to be the ICW. A strong correlation was found between ICW and interdental measurements, with ICW and upper first molars being the strongest (r=0.612, P= 0.004). A set of indices developed from the results was recommended for the positioning of complete denture teeth. In the second part of the study, inter-dental measurements were estimated using the indices obtained in the first part. The estimated inter-dental widths showed no significant differences compared with the real widths (P= 0.109, P=0.849, P=0.353, P=0.41). Based on the results of this study, ICW measurements can be used for setting up canines and first molars in complete dentures.

A retrospective study of shared learning on the BMedSci Dental Technology course at The University of Sheffield.

The aim of this study was to identify the level of shared learning on a Bachelor of Medical Science in Dental Technology (BMedSci) course at the University of Sheffield, School of Clinical Dentistry. A summative evaluation of the course was carried out, using semi-structured nominal group interviews. BMedSci students, BDS students and recent graduates were questioned and their answers analysed to identify shared learning activities. The results revealed that different levels of shared learning opportunities occurred within the different departments which delivered the course modules. Shared learning was viewed favourably by the students. It has the potential to maximise the use of resources and offers the opportunity for developing an integrated dental team.

An appraisal of the literature on centric relation. Part II.

The literature directly and indirectly related to centric relation (CR) has been reviewed chronologically. More than 300 papers and quoted sections of books have been divided into three sections. The first two parts of the paper are related to CR. Studies in this group mainly compared either the position of the mandibular condyle or the mandible itself in different CR recordings. Various tools were discussed for this purpose. The third part deals with CR-centric occlusion (CO) discrepancy. CR remains one of the controversial issues in prosthodontics and orthodontics. Debates relating to mounting casts on the articulator by reproducible records for orthodontic treatment planning and end results, and whether or not orthodontic treatment based on CO causes temporomandibular joint (TMJ) dysfunction, remain unsolved. The references are listed at the end of Part III.

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.

Dental education resources on the Web.

New methods of delivering educational material are being developed in order to improve effectiveness and efficiency of learning. They are not designed to replace conventional teaching methods, but to complement them and encourage self-directed learning among students. In the present technological age, the use of computers in teaching and learning is almost mandatory. This article describes the development of educational aids available on the World Wide Web through the project DERWeb (Dental Education Resources on the World Wide Web) and its expansion as a site for dental information for the whole dental community. Courses and demonstrations to various groups by the team have led to interest and uptake by those who were previously unaware of this form of information dissemination or were "afraid" to use computers. The project is expanding continually and projections for future development are discussed.

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.

Utilisation of domiciliary dental services.

OBJECTIVES: To develop undergraduate dental student understanding of the attitudes of elderly people towards dentistry and of the barriers which prevent them from seeking treatment. DESIGN: Each student interviewed a) an elderly person already known to them and b) an elderly person at a Day Rehabilitation Unit using a questionnaire. Students were not trained nor standardised. SETTING: a) in the student's home locality, b) in a Rehabilitation Unit in Sheffield. SUBJECTS: 161 people were interviewed with mean ages a) 78 years and b) 85 years. MAIN OUTCOME MEASURES: Perceptions of treatment need and domiciliary treatment by these elderly people. The results are summarised but not analysed because of the inherent limitations of data derived by unsupervised students. CONCLUSIONS: This educational exercise successfully engaged the studentsí minds and, for some, generated enthusiasm. They achieved valuable insight into the topic and realised that many people who inevitably have dental problems either feel that this is acceptable or do not know that they can obtain domiciliary dental care.

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.

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 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.