Denture identification marking should be standard practice.

The focus of this opinion article is to revisit whether denture identification marking should be routine and standard practice at manufacture in the United Kingdom. The benefits of denture identification marking are evident in the literature particularly for those who are in residential care or who will have to seek care due to dementia or physical frailty; however, within the UK it is not normally practised. Many patients would appear to be unaware of denture marking, but present positive attitudes towards it. Results of a survey of UK dental laboratories would indicate that the vast majority of them offer an inclusion denture marking service with a mean cost of £5 per denture. Is the lack of denture marking in the UK due to dental professionals having differences in opinion, lack of education of professionals in training or financial disincentives?

The bond between acrylic resin denture teeth and the denture base: recommendations for best practice.

Failure of the bond between denture teeth and base acrylic resin has been shown to be a cause of denture failure leading to inconvenience and costly repair. The optimal combination of acrylic resin denture tooth, denture base material, laboratory protocol and processing method has not yet been established. Extensive research enables the following recommendations for best practice to be made. Adopt practices that maximise the strength of the bond: select appropriate denture teeth; select base acrylic resin from the same manufacturer as the denture teeth; remove the glaze from ridgelaps of the denture teeth; apply monomer to the ridgelaps of the denture teeth before packing the base acrylic resin dough; use the manufacturers' recommended liquid/powder ratio; follow the manufacturers' recommended curing cycle; allow the flask to cool slowly and rest before deflasking. Adopt practices that avoid factors detrimental to bond strength: remove all traces of wax from the ridge laps of the denture teeth; remove all traces of mould seal from the ridgelaps of the denture teeth. It is evident that a number of factors are involved which may assist or prevent formation of an adequate bond, suggesting that attention to detail by the dental technician may be the most critical factor.

Developing professional status: an investigation into the working patterns, working relationships and vision for the future of UK clinical dental technicians.

AIMS: To investigate the working patterns and patient base of registered clinical dental technicians (CDTs); their relationships with dentists and other professionals in the dental team; their willingness to work within the NHS and their expectations for the future as a new professional group. METHODS: Face-to-face qualitative interviews of registered CDTs, selected because of their geographic representation and mode of working, informed the development of a postal questionnaire survey of all early registrants with the General Dental Council (GDC). RESULTS: The majority of CDTs reported working part-time, often combining clinical practice with their role as a dental technician. They reported both positive and negative working relationships with dentists and dental technicians, demonstrating collaboration and/or competition depending on whether the scope of CDTs was respected and patient care was shared or lost. CDTs role in the NHS was limited because they did not have the status of becoming a recognised provider of dental care. There was a desire to expand their scope of practice in future. CONCLUSION: CDTs are embracing their new status as an occupational group within dentistry. Core features of becoming a professional group were exhibited including the importance of social and financial status and the need to negotiate their current and future roles in the healthcare system.

The effect of monomer/polymer mixing ratio, time between mixing and packing of heat cured acrylic resin denture base material and bond assisting agents on the bond strength to acrylic resin denture teeth.

The aim of the study was to investigate the effect of varying the monomer/polymer mixing ratio, the time from mixing to packing heat cured acrylic resin and the effect of two bond assisting agents on the strength of the bond between denture base acrylic resin and acrylic resin denture teeth. Statistical differences were found in bond strength with monomer/polymer ratio and time between mixing and packing with one of the heat cured resins investigated. The benefit of using the bonding agents was not demonstrated.

Peer review: a view based on recent experience as an author and reviewer.

Peer review is an important stage in academic publishing, as a form of quality control to maintain the integrity of both the articles and the journals they appear in. However, the confidential nature of the relationship between reviewer and author does not necessarily benefit the system; with some reviewers using their anonymity to give unnecessary, injudicious comment. This paper explores the motives behind the reviewer's comments and how peer review could be improved by openness and honesty.

Effect of welding parameters of the Nd:YAG laser on the penetration depth of cobalt chromium alloys.

The aim of the investigation was to study the effect of the laser welding parameters of energy and spot diameter on the penetration depth of the weld of cast Co-Cr alloy when a single weld was performed. Within the limitations of the study as voltage increased and the spot diameter decreased, penetration depth increased. However, SEM investigation showed more defects in the welded area under these circumstances. The clinical significance is that during selection of the welding parameters the thickness of the components to be welded should be considered to achieve an extended welded area without the induction of micro-structural defects.

Flexural strength and degree of polymerization of a proprietary denture base acrylic resin designed to be cured using long or short cycles.

The flexural strength and degree of polymerization of Diamond D acrylic resin prepared with a long cure monomer and a short cure monomer were investigated using Trevalon as a control. Flexural strength and degree of polymerization of Diamond D acrylic resin were not affected by either using a long cure monomer or the short cure monomer. There was no significant difference in the glass transition temperature Tg between the long and slow cure Diamond D. Provided the manufacturer's instructions are followed the flexural strength, degree of polymerization and glass transition temperature are comparable with more traditional products.

The retentive forces of the locator attachment system at different angulations.

The change of retentive force of three types of Locator inserts when the implant analogue was positioned perpendicular to horizontal, 5 degrees and 10 degrees to perpendicular after 4,200 cycles in vitro was measured using an EnduraTech fatigue testing machine lubricated with artificial saliva. The more rapid decrease in retention occurred up to three months and stabilized after one year of simulated use. The Locator inserts provided more retention when the analogue was placed at 5 degrees to perpendicular compared to 0 degrees and 10 degrees after 9 months of simulated clinical use. After 2 years of simulated clinical use, there was a reduction in retention for all the three inserts of between 70% and 80%.

Current trends in removable partial denture teaching in British dental schools.

AIM: To investigate current teaching of removable partial denture construction in British dental schools. MATERIALS AND METHOD: A questionnaire was sent by email to each of the 15 UK dental schools. RESULTS: Replies were received from the 12 long established schools, although one declined to participate. The more recently established schools did not respond. All schools have a pre-clinical/technical course, which either precedes or runs in parallel with the early part of the students' partial denture experience, but students complete very little, if any technical work for their clinical cases. The majority of teaching takes place in multidisciplinary teaching clinics in years 2-5 although the majority of schools concentrate teaching of the basics early in the programme. Fewer cases appear to be treated than previously reported, especially cases requiring removable partial dentures with cobalt chromium frameworks. Students may only treat one such case, the remainder of dentures being constructed of acrylic resin. Lack of experience treating cases requiring a combination of complete and removable partial dentures was a concern. CONCLUSION: Participating schools appear to meet the General Dental Council's requirements. The amount of clinical work undertaken by students may have decreased slightly. There has been a greater decrease in the technical component.

Current trends in complete denture teaching in British dental schools.

AIMS: Against the background of the publication of the General Dental Council's interim report on undergraduate dental education the aim was to investigate current trends in teaching of complete denture construction to undergraduates in the twelve long established dental schools and to gather the opinions of lead teachers of complete denture courses regarding students' competence on graduation. MATERIALS AND METHOD: A questionnaire containing twenty-five factual questions and eight opinion questions was sent by email to the lead teacher in each of the twelve long established dental schools. RESULTS: Replies were received from all twelve schools. All schools teach complete denture construction although the number of cases students are required to treat varies from 5-6 to 1-2. Laboratory courses also varied in content and in most schools all technical work for patients was completed by technicians. Opinions varied regarding the level of competence achieved by students and their preparedness for Vocational Training. Three respondents thought students were adequately prepared, four thought they were, but with reservations and five thought their students were under prepared. The majority thought that the external examiner system, Teaching Quality Assessments and GDC visitations did not ensure GDC requirements for competence in complete denture construction were being met.

Effect of curing cycles on the mechanical properties of heat cured acrylic resins.

Traditionally long curing cycles have been recommended for heat cured acrylic resin denture base materials. Recently manufacturers have produced materials for which they recommend short curing cycles. Specimens conforming to British Standards Specification were made using three different brands of heat cured acrylic resin denture base material. Each material was processed in three batches using either the manufacturer's recommended short curing cycle, an arbitrary medium curing cycle or a traditional long cycle. Specimens were subjected to a three point bending test. With one exception using the arbitrary medium curing cycle, all specimens achieved the British Standard suggesting that the manufacturers' recommended cycles should be followed.

UK dental laboratory technicians' views on the efficacy and teaching of clinical-laboratory communication.

BACKGROUND: The General Dental Council states that 'good dental care is delivered by a team' and restorative treatment is enhanced by communication between team members. Commercial dental laboratories are ideally placed to comment on effective communication. AIMS OF THE STUDY: To investigate contemporary attitudes and communication between dentist and dental technician from the technician's perspective. MATERIALS AND METHODS: Eight hundred and three dental laboratories were invited to take part in a postal survey covering dentist/laboratory communication and the dentist's understanding of technical procedures. RESULTS: Forty percent of laboratories responded. Only 9% scored communication as very good, 48% scored communication with newly qualified dentists better than with established dentists but only 26% considered that dental students were taught to communicate with dental laboratories effectively. The free comments that the respondents were invited to make identified three distinct themes, 'recognition within the dental team', 'effective communication between dentist and dental technician' and 'dentists lack of technical knowledge'. CONCLUSIONS: Effective communication between dentist and dental technician is often poor. It was the view of the dental technicians who responded that newly qualified dentists do not have an appropriate understanding of technical techniques. Dental schools are still not preparing new graduates to communicate effectively with dental laboratories.

The effect of cyclic drying on dimensional changes of acrylic resin maxillary complete dentures.

Poly(methyl methacrylate) dentures may exhibit dimensional changes when drying. Drying has been shown to destroy Candida albicans. This study investigates the effect of simulating overnight cyclic drying on dimensional changes of four complete denture base materials. Denture specimens used in this study had been prepared for a previous study. All dentures had been kept hydrated at room temperature for 2 years. The materials used were, group 1, conventionally packed and cured Trevalon, group 2 was injection moulded and conventionally cured (Trevalon Success), group 3 (Acron MC) and group 4 was Microbase, which is injection moulded and microwave cured. The measurements of the inter-molar and inter-premolar width, and anterior posterior dimension between the premolars and molars were recorded after 8 h drying and then after four cycles of dehydration and rehydration. The dentures were more dimensionally stable in the anterior posterior than the cross arch dimension. There was a statistically significant (P < 0.02) increase in the intermolar width for Trevalon, Trevalon Success and Acron after 8 h drying and after four cycles. There was a statistically significantly difference between Microbase and the other materials after 8 h drying and there was a significant difference between the injection moulded groups in the interpremolar width (Trevalon Success versus Acron, Trevalon Success versus Microbase) after cyclic drying. Although statistically significant dimensional changes were observed for all materials these were small and were considered not to be clinically significant. Microbase was the least dimensionally stable material during air-drying.

Immediate replacement removable partial dentures with cobalt-chromium frameworks: rationale, technology and a case report.

The advantages of removable partial dentures with cobalt-chromium frameworks over those made entirely of acrylic resin, in oral health and hygiene, are well documented. However, in cases where teeth are to be extracted for fitting the removable partial denture, a difficulty arises because of the need to test the fit of the removable partial denture framework. The advent of two modern technologies-- laser welding and metal bonding agents -- make it possible to test the fit of the major part of the framework prior to adding additional metal components to support artificial teeth. A case is described in which the four lower incisors were extracted. The main part of the framework was constructed and its fit tested. A second casting was laser-welded to the lingual plate of the first casting to support the artificial incisor teeth. This technique avoids the need to make an acrylic resin temporary denture but incurs the cost of the additional technical work and so the advantages may be considered to be economically neutral.

The future of teaching of complete denture construction to undergraduates in the UK: is a replacement denture technique the answer?

Due to changes in the amount of curriculum time available for teaching complete denture construction to undergraduate students, course content requires reconsideration and possible modification. The idea that a replica complete denture technique may offer some advantages is explored. A review of the relevant literature fails to support many of the claimed benefits of this technique such as relative ease of adaptation by the elderly to new dentures. This article suggests that the replica denture technique should be considered as no more than an alternative method of making dentures. The relative demerits of the technique are discussed. A modification of the replica block technique to include important aspects of conventional complete denture courses is described. It is suggested that, because less clinical time is required, it may be a suitable way of introducing students to complete denture construction and educating them to a level which would encourage some to take further postgraduate study and would allow all graduates to treat routine cases or diagnose, treatment plan and refer to clinical dental technicians.

Pressure and temperature changes in heat-cured acrylic resin during processing.

OBJECTIVES: The aims of this study were to measure the pressure and temperature changes of acrylic resin during processing, to record the highest temperature reached when fast cured in boiling water and to determine the elevated boiling point of monomer under high pressure. METHODS: A subminiature pressure transducer (temperature compensated to 94 degrees C) and a thermocouple were placed on the palate of a standardized maxillary complete denture base. A heat-cured resin (Trevalon C) was polymerized by a long heating cycle (72 degrees C for 6.5 h and 92 degrees C for 1.5 h). Recordings of pressure and temperature (n=6) were made at initial clamping of denture flasks and throughout the processing cycles of resin. The temperature of the resin was also monitored during a fast cycle, which was accomplished by placing the flask directly into boiling water for 40 min. RESULTS: The pressure of acrylic dough inside the clamped flask was initially 11.5 atm (SD=3.2) and reached a peak of 22.0 atm (SD=3.5) during the long heating cycle. The elevated boiling point of monomer at increased pressure was calculated to be about 193 degrees C (at 11.5 atm) and 228 degrees C (at 22.0 atm). These elevated boiling points are higher than the maximum temperature 131 degrees C (SD=6.6) reached during the fast curing cycle. No porosity was observed even in the denture bases heat-cured by the fast cycle. SIGNIFICANCE: The highest temperature reached by heating of resin during processing is well below the elevated boiling point of monomer. Monomer therefore does not boil in clamped denture flasks under sufficient pressure. Thus adequate clamp pressure prevents gaseous porosity irrespective of curing cycle used.

The future of teaching of complete denture construction to undergraduates.

For some time there has been a need to discuss the undergraduate complete denture curriculum in the light of the inception of the specialist lists and the impending introduction of clinical dental technicians to ensure that general dental practitioners can continue to provide a complete denture service to the public. Publication in draft form by the General Dental Council of their document 'The First Five Years - The undergraduate dental curriculum increases the need for this debate.

Usage and status of cobalt-chromium removable partial dentures 5-6 years after placement.

The aim of this study was to describe the usage of cobalt-chromium (Co-Cr) removable partial dentures (RPDs) by patients 5-6 years after denture insertion and to find out the factors that affected their denture usage. A random sample of patients provided with Co-Cr RPDs from a dental teaching hospital in Hong Kong was selected. Patients were interviewed using a structured questionnaire concerning their assessment and use of the dentures. Those who had been constantly wearing their original RPDs were examined by one calibrated examiner under optimal clinical conditions. The response rate of the patients who could be contacted was 98%. The results from 189 patient interviews showed that usage of the RPDs declined with time and that half of the dentures had been discarded or replaced 5-6 years after insertion. These discarded RPDs had been in use for an average of 19.5 months. The main reason given by the patients for not using the RPDs was general dissatisfaction with the dentures in various combinations of comfort, fit and chewing ability and, less importantly, with food trapping and appearance. No statistically significant association between denture usage and their respective Kennedy classification was found. The status of the Co-Cr RPDs that had been constantly used for 5-6 years was generally good. The majority of these RPDs demonstrated fair to good cleanliness, stability and retention and had no defect of any sort.

The contribution of imaging and digitised data to mandibular reconstruction and implant stabilised occlusal rehabilitation: a case report.

Different methods are recommended for the surgical reconstruction of the resected mandible. The advantages for implant stabilised prostheses in restoring the occlusion are recognised but few papers provide adequate data to identify the successful outcome of treatment. The literature is reviewed and the advantages of imaging together with the use of digitised data is highlighted by a case requiring rehabilitation with enhanced planning methods.

The physical mechanisms of complete denture retention.

The purpose of this article is to assist the practitioner to understand which factors are relevant to complete denture retention in the light of the current understanding of physics and materials science and thus to guide design. Atmospheric pressure, vacuum, adhesion, cohesion, surface tension, viscosity, base adaption, border seal, seating force and muscular control have all been cited at one time or another as major or contributory factors, but usually as an opinion without proper reference to fundamental principles. Although there has been a detailed analysis published, it seems appropriate that a restatement of the points in a collated form be made. In fact, denture retention is a dynamic issue dependent on the control of the flow of interposed fluid and thus its viscosity and film thickness, while the timescale of displacement loading affects the assessment. Surface tension forces at the periphery contribute to retention, but the most important concerns are good base adaptation and border seal. These must be achieved if full advantage is to be taken of the saliva flow-related effects.