Stephen Dunne

The effect of increasing sodium fluoride concentrations on erosion and attrition of enamel and dentine in vitro

OBJECTIVES To investigate the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro. METHODS Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm x 3 mm area) before being randomly allocated to 1 of 5 groups per substrate (n=10/gp): G1 (distilled water control); G2 (225 ppm NaF); G3 (1450 ppm NaF); G4 (5000 ppm NaF); G5 (19,000 ppm NaF). All specimens were subjected to 5, 10 and 15 cycles of experimental wear [1 cycle=artificial saliva (2h, pH 7.0)+erosion (0.3% citric acid, pH 3.2, 5 min)+fluoride/control (5 min)+attrition (60 linear strokes in artificial saliva from enamel antagonists loaded to 300 g)]. Following tape removal, step height (SH) in mum was measured using optical profilometry. RESULTS When the number of cycles increased the amount of tooth surface loss increased significantly in enamel and dentine after attrition and erosion and for dentine after attrition. Attrition and erosion resulted in greater surface loss than attrition alone after 15 cycles of experimental wear of enamel. 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences. CONCLUSIONS The more intensive the fluoride regime the more protection was afforded to enamel from attrition and erosion. However, in this study no such protective effect was demonstrated for dentine.

A survey of the effectiveness of dental light-curing units and a comparison of light testing devices.

The aims of this study were to: 1. survey the light output from 49 light-curing units in clinical use; 2. measure the effect on depth of cure of composite resin caused by a range of light outputs; 3. assess the relationship between radiometer meter readings and depth of cure of composite resin in a human tooth model and a Heliotest. The mean meter reading produced by the 49 lights surveyed using a lampChecker radiometer was 4.4 (+/−2.4 SD), range 0.3 to 10.0. The manufacturer of the radiometer considers optimal light output to provide a meter reading within the range 5.0 to 7.0. Lights of very low output (0.7 +/− 0.1 SD) were found to be capable of curing, after 20 seconds, a 1.9 (+/−0.3 SD) mm thickness of composite resin. However, only approximately 50% of this thickness can be considered fully cured. Increasing the cure time from 20 seconds to 60 seconds increased the mean depths of cure by a factor of approximately 1.4. The mean depths of cure of composite resin placed in the Heliotest were greater than those observed in the natural tooth model, by a factor of approximately 1.3. Correlation coefficients of meter readings and depth of cure were greater for the Efos Cure Rite and Demetron 100 radiometers than the lampChecker unit

A qualitative and quantitative investigation into the effect of fluoride formulations on enamel erosion and erosion–abrasion in vitro

OBJECTIVES To investigate the effect of a single application of highly concentrated SnF(2) and NaF solutions and a NaF/CaF(2) varnish on human enamel subjected to hydrochloric acid erosion and tooth brush abrasion. METHODS Forty enamel samples were prepared from human third molars and NaF (9500ppm, pH 8.0), SnF(2) (9500ppm, pH 2.6) solutions; Bifluorid10(®) varnish (42,500ppm, NaF 5%, CaF(2) 5%) and deionized water (control) was applied to the enamel. Following this three, six and nine cycles of erosion [1 cycle=erosion (0.01M HCl, pH 2.2, 2min)+artificial saliva (1h, pH 7.0)] and erosion-abrasion [1 cycle=erosion (0.01M HCl, pH 2.2, 2min)+artificial saliva (1h, pH 7.0)+abrasion (120 linear strokes in artificial saliva from Tepe medium soft brushes 200g loading)] were carried out. The fluoride treated enamel was analysed using Knoop microhardness, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). RESULTS For erosion alone, there was significantly less microhardness reduction in the Bifluorid10(®) group after three and six cycles of erosion (P<0.05), however no other groups showed statistically different hardness (P>0.05). The EDS analysis showed that only the Bifluorid10(®) group had any detectable fluorine following erosion and erosion-abrasion (0.1wt.% and 0.2wt.% fluorine respectively). The surface fluorine was found to have been removed after erosion and erosion-abrasion for all other surface treatments. Although precipitates were observed after application of the surface treatments, following erosion-abrasion, no visible surface effects from any fluoride preparation remained. CONCLUSIONS Enamel surface precipitates from application NaF, SnF(2) solutions appear to not be able to provide protection against gastric erosion and tooth brush abrasion. The NaF/CaF(2) varnish provided limited protection against erosion but the role for such varnishes in gastric erosion and tooth brush abrasion remains uncertain.

Anticipatory anxiety in children visiting the dentist: lack of effect of preparatory information

AIM This study sought to explore whether viewing a leaflet explaining the benefits of dental treatment would have a significant impact on childrens anticipatory anxiety. METHOD Fifty children aged 8-12, attending the paediatric dental clinic of Kings College Hospital, London, took part in this triple-masked, randomized control study. The participants were randomly allocated to one of two groups and either shown an intervention leaflet containing child-friendly dental information (the experimental group) or a leaflet with child-friendly information on the benefits of healthy eating (the control group). Using the Facial Image Scale, anxiety was measured when the children arrived for their dental appointment, once before reading the leaflet and again after reading the leaflet. RESULTS There was no statistically significant effect of the experimental leaflet on self-reported anxiety levels in this study, although anxiety levels did drop slightly in both groups after reading a leaflet. CONCLUSIONS Providing paediatric patients with preparatory information about what to expect from a visit to the dentist had no effect on anticipatory anxiety in comparison to reading a leaflet about healthy eating. We speculate that reading, or cognitive processing, may have some beneficial effect. Future work should investigate this possibility.

Perceptions of a simulated general dental practice facility - reported experiences from past students at the Maurice Wohl General Dental Practice Centre 2001-2008.

This article assesses the perceived value of a simulated general dental practice centre as reported by past undergraduates over five years. Various aspects of teaching and related outcomes are explored based on responses received from anonymous questionnaires. A team based approach to cooperative learning led by current practitioners experienced in primary dental care was seen as pivotal to the huge success of the teaching model. Moreover the role of cooperative learning and its influence on building individual clinical confidence and acumen was considered highly beneficial as part of the transition from novice to expert.Methodology An anonymous questionnaire was distributed to students six months after qualification for a period of five years. The last registered postal address held by the Institute was used for this purpose. The years surveyed were: 2001-2002, 2002-2003, 2003-2004, 2005-2006 and 2007-2008. The questionnaire provided for both qualitative aspects of feedback and a quantitative representation of the overall perception of effectiveness of the General Dental Practice Centre, as expressed by a visual analogue scale.Results In total 135 questionnaires were returned representing a return rate of 53%. From the responses received 99% of the students reported that they enjoyed their sessions at the Centre with 96% expressing satisfaction with the teaching regime. The mean visual analogue scale rating the centre overall was reported as 83%, with a year on year increase ranging from 76-92%. Rich qualitative data were derived from free text responses.Conclusion A simulated general dental practice centre was highly rated by past dental students in terms of the overall learning experience received and its relevance to later vocational training. By far the most consistently reported attribute was the opportunity to practise close support four handed dentistry with a nurse. Training in practice management and organisational skills were viewed as important with effective teamwork and a friendly environment seen as conducive to building up knowledge and confidence. The role of experienced current primary care practitioners as teachers was seen to be very effective in this setting.

Stress Analysis of Occlusal Forces in Canine Teeth and Their Role in the Development of Non-Carious Cervical Lesions: Abfraction

Non-carious cervical tooth lesions for many decades were attributed to the effects of abrasion and erosion mainly through toothbrush trauma, abrasive toothpaste, and erosive acids. However, though the above may be involved, more recently a biomechanical theory for the formation of these lesions has arisen, and the term abfraction was coined. The aim of this study was to investigate the biomechanics of abfraction lesions in upper canine teeth under axial and lateral loading conditions using a three-dimensional finite element analysis. An extracted human upper canine tooth was scanned by μCT machine (Skyscan, Belgium). These μCT scans were segmented, reconstructed, and meshed using ScanIP (Simpleware, Exeter, UK) to create a three-dimensional finite element model. A 100 N load was applied axially at the incisal edge and laterally at 45° midpalatally to the long axis of the canine tooth. Separately, 200 N axial and non-axial loads were applied simultaneously to the tooth. It was found that stresses were concentrated at the CEJ in all scenarios. Lateral loading produced maximum stresses greater than axial loading, and pulp tissues, however, experienced minimum levels of stresses. This study has contributed towards the understanding of the aetiology of non-carious cervical lesions which is a key in their clinical management.

Restorative dentistry: Dental post-operative sensitivity associated with a gallium-based restorative material

Introduction This study forms part of a 2-year longitudinal clinical trial to compare the performance of a gallium-based restorative material (Galloy) with a high copper, mercury based (Dispersalloy) control material.Method Following Ethical Committee approval, 25 galloy restorations and 25 Dispersalloy controls were placed in 14 adult patients, by a single operator. The cavities were of moderate size, indicating the use of amalgam as the restorative material. All restorations were polished within 1 week of placement, photographed and a silicone impression of the tooth and restoration recorded. In addition, a visual analogue scale (VAS), indicating the extent of any post-operative sensitivity, was completed by each patient for each restoration, immediately prior to polishing. A score of 0 indicated no sensitivity, while a score of 10 indicated the greatest possible sensitivity. At 6-month recall, the VAS scores, silicone impressions and photographs were repeated.Results The mean sensitivity scores for the galloy and Dispersalloy restorations at 1 week were 5.1 (+/–3.4) and 1.0 (+/–1.5), respectively and at 6 months, 1.8 (+/–3.0) and 0.2 (+/–0.1) respectively. The differences between these means at 1 week and at 6 months were significant (P < 0.01).Conclusion Galloy restorations were associated with a much greater severity of post-operative sensitivity than Dispersalloy restorations.

Antibiotic prophylaxis in dentistry: part II. A qualitative study of patient perspectives and understanding of the NICE guideline

Background The National Institute for Health and Clinical Excellence (NICE) recommendations in 2008 for antibiotic prophylaxis before dental treatment contradict previous practice. There is a potential difficulty in explaining the new guidance to patients who have long believed that they must receive antibiotics before their dental treatment.Aim This study investigated the patient-related barriers and facilitating factors in implementation of the NICE guidance.Methods In-depth interviews were conducted with nine patients concerning their views about barriers and factors that could influence the implementation of the NICE guidance on antibiotic prophylaxis before dental treatment. Data were analysed using framework analysis.Results For patients the rationale for the NICE guidance was unclear. They understood that at the population level the risk of infective endocarditis was less than the risk of adverse reaction to antibiotics. However, on an individual level they felt that the latter risk was negligible given their previous experience of antibiotics. They were aware that standards of care change over time but were concerned that this may be an example where a mistake had been made. Patients felt that the characteristics of the person advising them about the new guidance were important in whether or not they would accept them – they wished to be advised by a clinician that they knew and trusted, and who was perceived as having appropriate expertise.Conclusions Patients generally felt that they would be most reassured by information provided by a clinician who they felt they could trust and who was qualified to comment on the issue by respecting their autonomy. The implications of the findings for the development of patient information are discussed.

So how do you see our teaching? Some observations received from past and present students at the Maurice Wohl Dental Centre

This study explores student perceptions of clinical teaching delivered at the Maurice Wohl Dental Centre, Kings College London Dental Institute. An on-line survey together with two paper-based questionnaires were used to invite three immediate past cohorts of final-year dental students to reflect and comment on their experiences during their year of attendance. Supporting data from current student focus group and face-to-face interviews were also included in the study. The principal findings from these triangulated methodologies were that the overwhelming majority of students felt they got on very well with their teachers. The development of a positive professional relationship with the teacher appeared to motivate students to work better. Teaching thought to be overly didactic and authoritarian would not be well received. The principal teaching style identified at the Centre was considered to be supportive and nurturing, encouraging a self-motivated and reflective approach to clinical practice.

Effect of distance from curing light tip to restoration surface on depth of cure of composite resin

Aims While light-activating composite resins, the light tip may not always be close to the surface of the restoration. This may be intentional in an attempt to create a ramp cure. The aim of this study was to determine the effect of a range of separation distances between the light tip and the restoration surface on the depth of composite cure for different types of light-curing units with a broad range of outputs. Methods Three halogen light units, one plasma arc-curing (PAC) light unit and two light-emitting diode (LED) curing lights in clinical use were tested, and a total of 570 restorations cured in a two-part human tooth model at separations ranging from 0 to 15 mm. The tooth was disassembled and depth of cure determined using the scrape test ISO 4049. Light intensity was also measured at each separation distance for each light. Results The depth of cure was generally found to decrease as the separation distance increased for all lights at the various cure times. However, the effect of increasing the separation distance was less than anticipated. The depth of cure was also related to the light output. Conclusions Depth of composite cure was directly related to intensity and duration of light exposure and inversely related to distance of the light source from the surface for halogen and plasma lights. However, the effect of increasing the separation distance up to 15 mm was less than expected. Altering the separation distance in order to modify the polymerisation characteristics is unlikely to be effective.