The flexural properties of endodontic post materials.

OBJECTIVES: To measure the flexural strengths and moduli of endodontic post materials and to assess the effect on the calculated flexural properties of varying the diameter/length (D/L) ratio of three-point bend test samples. METHODS: Three-point bend testing of samples of 2mm diameter metal and fiber-reinforced composite (FRC) rods was carried out and the mechanical properties calculated at support widths of 16 mm, 32 mm and 64 mm. Weibull analysis was performed on the strength data. RESULTS: The flexural strengths of all the FRC post materials exceeded the yield strengths of the gold and stainless steel samples; the flexural strengths of two FRC materials were comparable with the yield strength of titanium. Stainless steel recorded the highest flexural modulus while the titanium and the two carbon fiber materials exhibited similar values just exceeding that of gold. The remaining glass fiber materials were of lower modulus within the range of 41-57 GPa. Weibull modulus values for the FRC materials ranged from 16.77 to 30.09. Decreasing the L/D ratio produced a marked decrease in flexural modulus for all materials. SIGNIFICANCE: The flexural strengths of FRC endodontic post materials as new generally exceed the yield strengths of metals from which endodontic posts are made. The high Weibull modulus values suggest good clinical reliability of FRC posts. The flexural modulus values of the tested posts were from 2-6 times (FRC) to 4-10 times (metal) that of dentin. Valid measurement of flexural properties of endodontic post materials requires that test samples have appropriate L/D ratios.

The effect of clinically relevant thermocycling on the flexural properties of endodontic post materials.

OBJECTIVES: It is suggested that fibre-reinforced composite (FRC) posts have lower elastic moduli than metal posts and this will reduce the incidence of root fracture. However, the mechanical properties may be altered in the oral environment. The aims of this study were to determine the effect on the flexural properties of FRC and metal post materials produced by: (1) a thermocycling regime which was clinically relevant and representative of that which would occur during 1 year in the mouth and (2) storage for 1 year at body temperature. METHODS: Nine FRC and two metal post material samples were sealed in polythene sleeves and thermocycled between 10 degrees C and 50 degrees C for 10,000 cycles. Additional samples were stored dry at 37 degrees C for 1 year. The flexural strength and moduli were determined by three-point bending and compared with untreated control samples. RESULTS: Thermocycling and storage at 37 degrees C for 1 year decreased the mean flexural modulus of all materials. This was statistically significant for 8 of 11 materials after thermocycling, and 4 of 11 materials after storage at 37 degrees C (p<0.05). Thermocycling and storage at 37 degrees C produced a non-significant increase in yield strength for both metal post materials. Thermocycling significantly increased the flexural strength of Postec while it decreased for the other FRC materials. Storage at 37 degrees C increased the flexural strength of three FRC materials (significantly for Postec) while it was decreased among the other materials. CONCLUSIONS: Although some of the changes noticed in flexural properties were statistically significant, it is doubtful that they are of sufficient magnitude to affect clinical performance.

Mandibular two implant-supported overdentures as the first choice standard of care for edentulous patients--the York Consensus Statement.

The Annual Conference of the BSSPD (British Society for the Study of Prosthetic Dentistry) was held in York on 6 and 7 April 2009. At the symposium on mandibular overdentures, presenters offered a synopsis of the research available on the efficacy of implant-supported mandibular overdentures in the edentulous mandible. Emphasis was given to both qualitative and quantitative research based on patient-centred outcomes of treatment. A draft consensus was circulated to all presenters and to the Council members of the BSSPD and to BSSPD members on the Society's website. The statement was modified in the light of their comments, audience feedback following the presentations and members' feedback. We hope that this consensus statement will be a useful guide for patients and clinicians and that it will act to stimulate wider debate. We also hope that it will prove useful to other patient and professional organisations and will inform discussions with providers of national healthcare and with independent funders.

Trends in indirect dentistry: 5. Impression materials and techniques.

UNLABELLED: A fundamental pre-requisite for the construction of satisfactory indirect restorations is the ability to record an accurate and detailed impression of the dental structures. Knowledge of the key properties of the available impression materials and their handling behaviour is necessary if they are to be used effectively. A variety of techniques can be employed in different situations, each of which can be highly successful, but only if attention is paid to the detail of their execution and the clinician is aware of their individual limitations and pitfalls. Where imperfections occur, an appreciation of how they have been caused, and the strategies to take to prevent them will lead to greater success in impression taking. CLINICAL RELEVANCE: Current materials exceed our needs in terms of accuracy and stability, and yet the impressions produced are frequently flawed. By realizing why faults occur, being aware of the range of techniques available and having an understanding of the behaviour of materials, clinicians can achieve the quality in their impressions that is possible and necessary to provide excellence in indirect restorations.

The Effectiveness of Systemp.desensitizer in the treatment of dentine hypersensitivity.

PURPOSE: This study reports the effectiveness of Systemp.desensitizer (Ivoclar Vivadent, Schaan, Liechtenstein), when used both with and without an acid-etch step, in the treatment of patients with dentine hypersensitivity in UK dental practices. MATERIALS AND METHODS: Ten general dental practitioners (GDPs) were selected from two practice-based research groups. The GDPs were each requested to use Systemp.desensitizer in the treatment of at least ten patients who presented with pain due to dentine hypersensitivity. Systemp.desensitizer was applied to the sensitive dentine area in strict accordance with the manufacturer's handling instructions, except that the patients were divided into two groups. For the first, group NE, the procedure was to isolate the tooth, gently blot it dry with cotton wool pellets, rub Systemp.desensitizer into the tooth for 20 seconds, then gently air-dry it. For the second, group E, the procedure was identical except that after isolation, the treatment area was etched for 15 seconds with 35% phosphoric acid. Patients were asked to complete a pro forma using a 10 cm visual analogue scale designed to provide details of the extent of their pain before treatment, 24 hours post-treatment, one week post-treatment, one month post-treatment, and three months post-treatment. The zero end of the scale was marked 'no pain' and the 10 cm end was marked 'extreme pain'. The percentage change in the patients' perception of their pain, relative to pretreatment, was calculated using repeated measures analysis and suitable follow-up confidence intervals for the mean changes in perceived pain. Comparisons were then made between the treatment groups NE and E. RESULTS: Ninety-one patients completed the first pro forma and 77 completed all the pro formas. Overall, there was a significant reduction in pain at each of the time points after treatment but the pattern of pain reduction across the two groups was different. In general, the non-etched group (group NE) saw an 'immediate' reduction in pain which was then fairly consistent across the longer term, whilst, in general, the etched group (group E) saw less reduction in pain 24 hours after treatment, and then further reduction in pain at both one week and one month after treatment. Thus the non-etched group experienced an early reduction whilst the etched group took longer to perceive a reduction in pain; however, there were no statistically significant differences between the reductions in pain scores between the two groups at any of the time points after treatment. CONCLUSION: It is concluded that Systemp.desensitizer was effective in reducing pain from dentine hypersensitivity in the patients treated, and this finding was unaffected by whether or not the tooth was acid-etched prior to application of the reagent.

Rectangular collimation and radiographic efficacy in eight general dental practices in the West Midlands.

INTRODUCTION: Rectangular collimation is recommended in order to reduce radiation doses to patients. However, anecdotal reports suggest that it may result in more retakes, with a possible net increase in patient dosage. METHOD: To test this hypothesis, eight general dental practitioners were recruited to participate in a project. Each took 25 pairs of bitewing radiographs of patients before and 25 after fitting rectangular collimators to their x-ray machines. Double-pack films were used so that duplicates could be examined. These were assessed by a consultant oral radiologist according to the National Radiographic Protection Board (NRPB) grading system for positioning and general film quality. RESULTS: Initially, positioning quality was above the target level for six of the eight dentists; however, for all but one, this dropped after using rectangular collimation. General film quality was of a lower overall standard initially. Using rectangular collimation had an effect on general film quality but the direction and size of this varied among the dentists. CONCLUSION: It was concluded that amongst the participating dentists, although numbers of retakes increased by 7%, there would be a net reduction in dosage to patients following rectangular collimation.

Endodontics and new graduates, Part 2: Undergraduate experience and course evaluation.

A postal survey of recent United Kingdom dental graduates was undertaken to establish the amount of their undergraduate endodontic experience and their opinions of their training. A 75% response was achieved from all but two schools. Recent graduates had generally undertaken fewer cases as students than older graduates. Several had undertaken very few endodontic procedures as students. Differences and trends were seen in the opinions of students and their experiences among the schools, and between the two year groups studied. Most students were not very confident to undertake molar endodontics. Many felt they needed more practical experience as students and training in newer techniques and instrumentation.

Occupational exposures occurring among dental assistants in a UK dental school.

PURPOSE: The cross-infection risks for dentists have been well recognised, and much has been published regarding the incidence of occupational exposures to patient body fluids. Less has been reported regarding the risks to dental assistants. The purpose of this study was to evaluate the incidence of occupational exposures to patient body fluids among dental assistants, to assess the rate of reporting of such incidents, and to evaluate the association of various factors with these exposures. METHOD: All 84 dental assistants working at Birmingham Dental Hospital were asked to complete a confidential questionnaire to provide retrospective information regarding the nature and incidence of any occupational exposures they had experienced. RESULTS: An overall response rate of 94% was achieved. Dental nurses experienced fewer occupational exposures than dental students at the same institution, and reported incidents more frequently. More injuries occurred after the treatment session. Handling local anaesthetic syringes was associated with more injuries, and percutaneous injuries predominated. Trainee nurses had experienced more occupational injuries in the preceding six months than their qualified colleagues. There was no significant association with any of the other factors evaluated. CONCLUSIONS: The general incidence of occupational exposures among the dental assistants in this survey was low in comparison to dental students at the same institution. A further reduction may be possible by increasing the training of unqualified nurses with particular regard to post-treatment handling of sharp dental instruments and equipment.

Endodontics and new graduates: Part I, Practice vs training.

Surveys have demonstrated that many dentists, even the recently qualified, do not carry out endodontics using currently recommended materials and techniques. To assess the scale and nature of this finding among young graduates, a questionnaire was sent to all graduates from the mainland United Kingdom dental schools qualified for either one or four years. Widespread reduction in the number of radiographs taken and rubber dam use was found. A minority had adopted techniques and materials without published guidelines. It is suggested that alterations are required in undergraduate teaching, vocational training and the United Kingdom National Health Service remuneration system in order to improve the standard of endodontics in general practice.