Quality of communication and master impressions for the fabrication of cobalt chromium removable partial dentures in general dental practice in England, Ireland and Wales in 2009.

The aim of this study was to investigate the quality of communication and master impressions for the fabrication of cobalt chromium removable partial dentures (RPDs) in general dental practice in England, Ireland and Wales in 2009. Two hundred and ten questionnaires were distributed to 21 laboratories throughout England, Ireland and Wales. Information was collected regarding the quality of written communication and selection of master impression techniques for cobalt chromium partial dentures in general dental practice. One hundred and forty-four questionnaires were returned (response rate = 68%). Alginate was the most popular impression material being used in 58% of cases (n = 84), while plastic stock trays were the most popular impression tray, being used in 31% of cases (n = 44). Twenty-four per cent (n = 35) of impressions were not adequately disinfected. Opposing casts were provided in 81% of cases (n = 116). Written instructions were described as being 'clear' in 31% of cases (n = 44). In 54% of cases (n = 76), the technician was asked to design the RPD. Based on the findings of this study, written communication for cobalt chromium RPDs by general dental practitioners is inadequate. This finding is in breach of relevant contemporary legal and ethical guidance. There are also concerns in relation to the fabrication process for this form of prosthesis, particularly, in relation to consideration of occlusal schemes.

The effect of bleaching, varying the shade or thickness of composite veneers on final colour: an in vitro study.

OBJECTIVE: To investigate whether bleaching prior to placement of a composite veneer had an effect on the final shade of the restoration and whether this was affected by the thickness or shade of the veneer. METHODS: Twenty bovine teeth were collected, sectioned and divided into two groups. One group was the non-bleached control, while the other was the bleached group. A colour reading was recorded using a spectrophotometer. The bleached group then underwent external bleaching with 38% hydrogen peroxide and a colour reading was recorded. Each of these two groups were further sub-divided into four subgroups, on which composite veneers were placed. These subgroups were: 0.5 m thick A1, 1 m thick A1, 0.5 mm thick A4 and 1 mm thick A4 composite veneers. Colour readings were recorded after veneer placement. Statistical significance was assessed using analysis of variance. RESULTS: There was a difference between the colour produced for the same veneer properties, between the bleached and non-bleached groups. For a thin (0.5mm) A4 veneer bleaching produced a statistically significant difference in the amount of colour change (DeltaE) compared to veneering alone. For A1, non-bleached group there is a significant difference in the DeltaE produced by altering the thickness of the veneer. CONCLUSION: Within the limitations of this study, we can conclude that bleaching prior to placement of a thin A4 dark veneer produces a significant difference in colour change. If no bleaching is performed, altering the thickness of an A1 veneer produces a significant colour difference DeltaE. However, if bleaching is carried out there is no significant difference.

An investigation into most effective method of treating stained teeth: an in vitro study.

OBJECTIVE: To assess the most efficacious method of treating stained teeth: bleaching alone, veneering alone or a combination of bleaching and veneering and whether the choice alters depending on the degree of staining. METHODS: Extracted teeth were sectioned to give 117 samples. These samples were split into unstained, lightly and darkly stained groups based on CIE-Lab value L*. The lightly and darkly stained groups were stained using tea. Teeth from each group were then assigned to one of four subgroups (control (C), bleaching alone (B), veneering alone (V), or a combination of bleaching and veneering (BV), each containing 13 samples. Veneering was performed using 0.8-mm thick ceramic veneer of shade B1. CIE-Lab values were recorded using a spectrophotometer and the colour difference (Delta E) was calculated for each intervention. The final colour was compared to the value for obtained from a B1 (Vita) Shade tab. Statistical significance was assessed using analysis of variance. RESULTS: In all three test groups, intervention resulted in a statistically significant colour change compared to the C group (p

Quality of master impressions and related materials for fabrication of complete dentures in the UK.

The aim of this study was to examine the quality of master impressions and related materials for fabricating complete dentures in the UK. One hundred and fifty pre-piloted questionnaires were distributed to a number of dental laboratories in the UK with large catchment areas. Information requested related to the quality and choice of techniques for the master impression stage of fabricating complete dentures, as well as prescription of materials for occlusal registration, amongst others. All information was recorded anonymously. One hundred and forty-four completed questionnaires were returned. All items were provided on a private basis. Eighty-three per cent (n=119) of master impressions were made using a custom tray, the remainder were made using a plastic stock tray. The most commonly used impression material was zinc oxide-eugenol (42%, n=60), followed by polyvinylsiloxane (39%, n=56) and irreversible hydrocolloid (19%, n=28). Master casts were poured after a minimum of 4 days. Eleven per cent of impressions examined (n=16) were judged to have errors. It was reported that 64% of master impressions (n=92) examined had been disinfected adequately. While this study revealed evidence of good clinical practice, particularly in relation to the selection of impression trays and quality of master impressions for complete dentures, there were some areas of concern, particularly in relation to the disinfection of the impressions examined. Dental practitioners should aim to provide their patients with high-quality prostheses by observing best clinical practice at all times.

Undergraduate requirements in restorative dentistry in the UK and Ireland.

OBJECTIVES: To ascertain the requirements in restorative dentistry that undergraduate dental students have to fulfil in order to sit the finals examinations in dental schools in the UK and Ireland and to compare those requirements with the competencies stipulated by the GDC in The first five years. METHODS: Fifteen anonymised questionnaires, of open and closed question design, were sent by post to academics in the university departments of restorative dentistry in each of the undergraduate dental schools in the UK and Ireland. The first section concerned numerical information regarding total numbers of procedures that were required to be completed in undergraduate restorative dentistry. The second section was designed to ascertain information as to how decisions are made with respect to an undergraduate's readiness to sit the finals examination in restorative dentistry (such as continual assessment and/or competency assessments). RESULTS: A total of 15 replies were received for analysis, a 100% response rate. Several institutions emphasised that they do not have 'requirements', but provide guidelines as to what should be achieved. Six institutions did not have set numerical requirements for direct placement restorations or bridges. The number of direct placement restorations required at the other nine institutions ranged from 50 to 160. Five institutions did not have numerical requirements for dentures; four institutions did not set numerical targets for crowns, veneers, inlays/onlays or endodontics. In institutions where numerical requirements were not used, forms of competency assessments were completed. The requirements across all institutions for periodontology, integrated treatment planning and completed cases were ill-defined. CONCLUSIONS: This study shows that there is a wide disparity amongst institutions in the UK and Ireland with regards to finals requirements in restorative dentistry. Ideally, such requirements should be similar between institutions and should be closely mapped to the GDC's required learning outcomes (The first five years) for the UK institutions.

The effect of enamel porcelain thickness on color and the ability of a shade guide to prescribe chroma.

OBJECTIVE: To test the null hypothesis that there is no color change when enamel porcelain thickness is changed and to evaluate the ability of a shade guide to prescribe chroma. METHODS: Three shades (3M1, 3M2 and 3M3) were selected from a Vitapan 3D master shade guide. Five disk specimens were prepared for each shade, consisting of three layers (opacious dentin, dentin and enamel) at thicknesses of 0.6, 0.8 and 0.6mm, respectively. The color of each disk was measured using a spectrophotometer. Enamel porcelain was reduced in thickness to 0.3mm and porcelain disks were remeasured. RESULTS: Reducing the enamel thickness of porcelain disk specimens significantly increased L) (p<0.05), b*, metric chroma and hue angle (p<0.001). For the three shades studied (3M1, 3M2 and 3M3) L* values were not significantly different (p>0.05) and chroma increased for 3M1 with the lowest chroma to 3M3 with the highest chroma, which is in line with the shade guide specifications. Although statistically significant (p<0.001) changes in hue angle between the three shades were small (less than 3 degrees overall). The difference in chroma between the three shades 3M1, 3M2 and 3M3 was greatest for the thin enamel layer than the thick enamel layer. SIGNIFICANCE: A change in enamel thickness from 0.6 to 0.3mm resulted in a three-unit change in L* and metric chroma and a 4 degrees change in hue angle. A change in enamel porcelain thickness will have a greater effect on higher chromatic shades than those with lower chroma. The ability of the shade guide to prescribe chroma was demonstrated but this could be offset by an anomalous enamel thickness.

The effect of colour defective vision on shade matching accuracy.

One hundred and forty one male dental students and staff were screened for colour-defective vision. Ten colour-defective and 20 non colour-defective subjects then carried out a shade matching exercise using nine selected shades and another matched, shade tab (to test for consistency) from Vita shade guides. All shade matching took place under standard lighting conditions. Each subject also completed a short questionnaire relevant to shade matching. There were no significant differences found between colour-defective and non colour-defective subjects in shade matching abilities. Although both subject groups were similar in their shade matching abilities, individuals with colour defective vision perceived it to be a slightly more difficult exercise.

Undergraduate training as preparation for vocational training in England: a survey of vocational dental practitioners' and their trainers' views.

AIMS: To compare the views of new vocational dental practitioners (VDPs) and their trainers regarding how undergraduate dental education has prepared them for their vocational training (VT) in England. This study also aims to identify areas of relative weakness in dental undergraduate education that could influence the future training needs of vocational trainees. METHOD: Structured postal questionnaires were completed by VDPs and trainers from five Deaneries in England. The usable response rate was 71% (n = 186 VDPs and 186 trainers). RESULTS: The vast majority of VDPs and trainers perceived the undergraduate training in history taking, diagnosis and treatment planning for general practice to have been covered 'well' or even 'very well'. Undergraduate training in routine restorative dentistry, oral pathology and paediatric dentistry was also perceived to have been covered well. However, a large proportion of VDPs and trainers reported that they felt that undergraduate training in orthodontics, molar endodontics, surgical endodontics and surgical extraction of teeth had not adequately prepared them for VT. CONCLUSIONS: Newly qualified dentists appear to lack certain competencies recommended by the General Dental Council in The First Five Years. This has implications for dental undergraduate education, but also highlights current training needs during VT.

Deviation from the Broadrick occlusal curve following posterior tooth loss.

Production of an appropriate occlusal curve for dentitions which have become deranged because of tooth loss, overeruption, tipping and drifting can present challenges for the dental technician. An earlier paper (J Oral Rehabil, 2005 32: 895-900.) demonstrates that the use of the Broadrick flag method for producing the occlusal curve is relatively accurate for most intact arches. This study demonstrates that when a posterior tooth has remained unopposed for 5 years or more positional changes, which cause deviation from the Broadrick curve, occur. The extent of the deviation may be extreme, potentially leading to difficulties in restoring a harmonious occlusal scheme. This study also demonstrates that the Broadrick curve may provide an accurate reproduction of the occlusal curve, even when the tooth forming the posterior determinant of the curve is tipped. A moderate degree of tipping of this tooth has little effect on the radius of the Broadrick curve.

A study of the proximity of the Broadrick ideal occlusal curve to the existing occlusal curve in dentate patients.

Increasingly, clinicians are called upon to restore dentitions, which have become mutilated because of tooth loss, wear, trauma and disease. In many cases, restoration of the occlusal plane may be required. A simple tool, which provides the laboratory technician with an approximation of the patient's original occlusal curve may be useful. The purpose of this study is to determine the accuracy of the occlusal curve designed using the Broadrick flag. A total of 100 patients with intact dental arches were examined, and deviations from the Broadrick curve were measured on scanned study models using a software package. Simple descriptive statistics were used to investigate the data, and intra-examiner reliability was examined using a Bland Altman plot. The results demonstrated little deviation from the Broadrick curve in natural adult dentitions, mean deviation 0.1262 mm, 95% confidence interval -0.32 to 0.2844. Good intra-examiner reliability was achieved. It can be concluded that the Broadrick flag method may be of use in determining an appropriate occlusal curve for dentate individuals with deranged occlusal planes.

Microleakage of glass-ionomer cement placed in association with non-setting calcium hydroxide.

The purpose of this investigation was to determine whether non-setting calcium hydroxide [Ca (OH)2] cement placed in the root canal system of premolar teeth would affect the subsequent microleakage of a glass-ionomer restoration (GIC). Following selection, 62 human premolar teeth extracted for orthodontic reasons were accessed and root canals prepared according to a standardized procedure. The specimens were then allocated randomly into two major groups each of 30 teeth. Two other teeth were used as a positive and a negative control. The control group was restored with glass-ionomer cement following drying of the canal and placement of a cotton wool pledget. The test group had all canals dressed with non-setting Ca(OH)2 and then was subdivided, one set (n = 22) being restored following conditioning of the access cavity margins, the other (n = 8) having the margins cleaned with a hand excavator. Samples were assessed for microleakage using a two-point scoring system (leakage or no leakage) in conjunction with a clearing technique using AgNO3. Using Fisher's exact test, a statistically significant difference was found between the control and test groups (P < 0.05) but there was no significant difference between the excavated and conditioned cavities (P=0.55). It is concluded that contamination of access cavity margins with Ca(OH)2 during medication of a root canal interferes with the bond of GIC, resulting in increased microleakage in vitro.

Assessment of a contrast medium as an adjunct to endodontic radiography.

AIM: To assess if a contrast medium improved diagnostic yield of endodontic radiographs. METHODOLOGY: Forty-five extracted mandibular premolar teeth were radiographed in bucco-lingual and mesio-distal planes. Access cavities were prepared, pulpal tissue extirpated and Ultravist contrast medium introduced under pressure. Radiographs were retaken and the teeth cleared following perfusion with India ink. Three examiners assessed all the films for: number of roots, number of root canals, curvature of root and/or root canal, presence of lateral canals, presence of a single foramen or apical delta and the presence or absence of canal obstructions. The examiners' interpretations were compared with the anatomy revealed by clearing. RESULTS: Kappa scores were calculated for each of the examiners, for each set of radiographs, to assess the level of intra- and inter-examiner agreement. Only moderate agreement was found throughout (kappa = 0.40-0.61). For multiple root canals a false-positive result was significantly more likely with contrast (P < 0.05). The use of contrast did not significantly improve the sensitivity of diagnosis of lateral canals or a single apical foramen. Contrast significantly increased the risk of falsely perceiving lateral canals (P < 0.002). Overall there was no statistically significant difference in the overall assessment of the anatomy of the root canals using contrast or plain radiographs (P > 0.2). CONCLUSIONS: Plain film radiographs confidently predict the presence of root or canal curvature but apical anatomy was assessed accurately in only 46% of cases. Plain radiographs were insensitive in assessing the number of root canals present, the presence of lateral canals and the occurrence of canal obstructions. The use of Ultravist contrast medium to improve diagnosis of root canal morphology of premolars is not supported.

Eruptive tooth movement--the current state of knowledge.

How the dentition erupts, and what controls it, is fundamental to almost all aspects of clinical dentistry, yet the mechanisms behind this have not yet been fully elucidated. When the process continues into space that has been created through toothwear or tooth loss, problems in placing restorations can be encountered. This review examines the possible mechanisms of tooth eruption. Differences between processes in animals and humans are highlighted. The limitations of conclusions drawn from animal studies are then discussed with reference to human dental conditions. The differing forms of overeruption in humans are described and the treatment options for overerupted teeth, including prevention of the situation arising, are provided with a discussion of the quality of the evidence base behind these.

A clinical report of 85 fractured metallic post-retained crowns.

AIM: To determine any patient, technique or material factors that were significantly associated with post fracture in metallic post systems. SUMMARY: Eighty-five fractured metal posts were retrieved over a 5-year period from a total of 84 patients who attended a dental hospital for treatment. A record was kept of the patient's dentition to identify the tooth with the fractured post, the number of teeth present, the excursive guidance scheme and the likely post design and material. Radiographs of 67 of these teeth were available. The presence or absence of a periapical lesion was noted as was the quality of the root filling. Maxillary lateral incisors, followed by maxillary centrals were associated with most of the fractured posts. The median survival to fracture was 36 months. The number of teeth in the dentition had a mode of 28. The most commonly fractured post design was a serrated and parallel design with an average diameter of 1.2 mm at the site of fracture. Apical lesions were found in 67% of the teeth with radiographs. Only 12% of teeth with a 'good' apical filling as opposed to 55% with a 'poor' apical filling had apical lesions. KEY LEARNING POINTS: . Maxillary lateral incisors, followed by maxillary central incisors are at greatest risk of having a fractured metallic post. . Having a large number of teeth in the dentition or an adequate length of post was not protective against metallic post fracture. . Teeth with fractured post-retained crowns had a high incidence of apical lesions.

In vitro dentine permeability: the relative effect of a dentine bonding agent on crown preparations.

OBJECTIVE: The aim of this study was to determine whether a dentine bonding agent (DBA) had an effect in reducing fluid filtration under cemented provisional crowns. METHODS: Crown preparations on 34 premolars, randomly allocated to two equal-sized test and control groups, were assessed for dentine permeability by a fluid filtration technique. In the test group, prepared crowns were acid-etched and then treated with a DBA (Prime & Bond NT). In the control group, no such DBA was applied. Provisional crowns were cemented on both groups of teeth using non-eugenol zinc oxide cement. Fluid filtration rates were measured repeatedly after crown preparation, at cementation, 1 h, 1 day, 1 week and 3 weeks following crown cementation for both groups. Filtration rates were also measured after acid-etching and dentine bonding for the test group. RESULTS: There was insufficient evidence to suggest any statistically significant differences either between the two groups or, on average, across the five time points in each group in terms of the relative percentage of fluid filtration. CONCLUSION: The DBA used did not seal dentinal tubules any more than did the smear layer and provisional crowns luted with a non-eugenol ZnO cement.

A study of the incidence of overeruption and occlusal interferences in unopposed posterior teeth.

OBJECTIVES: To determine the incidence and extent of overeruption in unopposed posterior teeth; to determine the incidence of occlusal interferences associated with unopposed posterior teeth; and to detect an association between the extent of overeruption and the presence of occlusal interference. DESIGN: The study was a single centre clinical retrospective analysis. Setting The setting was in the Combined Care Clinic of Leeds Dental Institute. The patients were undergoing routine restorative care by final year undergraduate dental students during 2000. SUBJECTS AND METHODS: All patients over18 years of age with one or more unopposed posterior tooth, were invited to participate. A sample group of 120 subjects were recruited. A clinical occlusal examination was carried out and the presence of initial retruded contact position (RCP) contacts and excursive interferences were recorded. Study models were made and digitally scanned. OUTCOME MEASURES: Measurements of overeruption from the curve of Spee were made from the images obtained, by a single observer. Reliability of the measurements was assessed by means of a Bland Altman Plot. The presence and site of RCP contacts and excursive interferences were recorded by a single observer. Reliability of the measurements was assessed by means of Kappa scores. The association between overeruption and the presence of occlusal interference was examined using Spearmans Correlation Coefficient. RESULTS: A total of 120 subjects were recruited, with a total of 155 unopposed sites. Eighty-one of the sites belonged to male subjects, 74 to female subjects. The mean age of the group was 50.9 years, Standard deviation 13.9 Eighty-three per cent of sites displayed overeruption (95% CI 78-90), ranging from under 0.5 mm to 5.4 mm. The reliability of the observations was found to be good. A total of 51.6% (95% CI 44-60) of unopposed teeth were involved in RCP contacts or excursive interferences. Thirty-two sites were involved in more than one contact or interference. The intra-examiner agreement was found to be good, using Kappa. The findings of the Spearman's correlation, show that if an association exists between overeruption and occlusal interference, it is weak, and of no statistical significance. CONCLUSIONS: Eighty-three per cent of unopposed teeth are likely to overerupt, and the extent of the overeruption may be marked. The incidence and extent of overeruption is of clinical significance, not only in terms of treatment planning to prevent undesirable vertical movement, but also in the restoration of the edentulous space. The reliability of observations made in the study was found to be good, justifying the methodology. Fifty-one point six per cent of unopposed teeth are likely to be involved in RCP contacts or excursive interferences. The incidence is of clinical significance when planning the restoration of unopposed teeth, or the associated edentulous space. Only a weak statistical association was demonstrated between the degree of overeruption and the presence of occlusal interferences.

The effect of luting media on the fracture resistance of a flame sprayed all-ceramic crown.

OBJECTIVES: This in vitro study investigated the effect of selected luting media on the fracture resistance of a flame-sprayed all-ceramic crown. METHODS: Three groups of 10 human upper premolar teeth were prepared for crowning using a standardised technique. Flame sprayed crowns were fabricated and cemented onto the preparations using zinc phosphate (ZPC), glass polyalkenoate (GPC) or composite luting cement (CLC). During crown seating, a pressure perfusion system simulated pulpal fluid outflow equivalent to 300mm of H2O. Compressive fracture resistance was determined for each group using a Universal Testing Machine with a crosshead speed of 1mm min(-1). A group of unrestored teeth acted as a control. RESULTS: The fracture resistance of the groups ranked as follows: ZPC>CLC>>GPC=unrestored teeth. The difference between the fracture resistance of ZPC and CLC groups and the control group was statistically significant. The mode of fracture between the luted crowns and natural crowns was markedly different. CONCLUSIONS: When tested in compression, a new, flame-sprayed all-ceramic crown, when luted in place using ZPC, GPC or CLC, could produce strengths comparable to or greater than natural unrestored teeth. The luting agent used significantly affected the recorded fracture loads.

A pilot study of intraoral temperature changes.

The aim of this in vivo pilot study was to record variations in temperature at various sites in a subject's mouth in response to a standardised thermal challenge and to determine a more realistic thermocycling regimen for future use. A volunteer who suffered from no dentinal hypersensitivity had modified study models prepared for constructing vacuum-formed PVC splints. Perforations 2 mm in diameter were placed for thermocouples facially and lingually in the midcoronal sites of the upper and lower central incisors, canines, second premolars, and second molars to measure temperatures at these sites. A standardised drinking regimen was followed of hot black coffee (72.5 degrees C) followed by cold orange juice (6.0 degrees C). Contralateral sites experienced similar temperature changes of short duration. A maximum of 68.0 degrees C and a minimum of 15.4 degrees C were recorded. Less extreme temperatures were experienced posteriorly, and little or no discernible changes were noted at the facial aspects of the upper second molars or lingually on the lower second molars. Most commonly used thermocycling regimens are clinically unrealistic, and temperatures vary widely throughout the mouth when hot or cold drinks are taken.

A fluid filtration and clearing technique to assess microleakage associated with three dentine bonding systems.

OBJECTIVES: The aims of this in vitro study were to (a) measure fluid flow through teeth restored with one of three dentine bonding systems and a resin composite restoration; (b) measure the distribution of a silver tracer through the same teeth, and make a comparison with fluid flow; and (c) investigate the effect of thermocycling on both measurement types. METHODS: Coronal segments of 30 premolars, randomly allocated to three equal groups, were assessed by fluid filtration. Each group was restored with a resin composite restoration in conjunction with Fuji Bond LC (FBLC), Scotchbond Multi-Purpose Plus (SMP+) or Prime&Bond 2.1 (P&B2.1). Fluid filtration rates were measured in the intact crown and then after cavity preparation, conditioning, dentine bonding, restoration and at 2 and 24 h, 1 week and 1 month following restoration. Six specimens from each group were thermocycled at 1 week. After final filtration measurements the specimens were perfused with silver nitrate and cleared before scoring tracer penetration. RESULTS: No significant differences (P > 0.05) in fluid filtration rates were found amongst the different bonding systems or at any restoration stage. Thermocycling was not associated with any significant (P > 0.05) increase in fluid filtration. Final fluid filtration and tracer distribution showed a weak and not statistically significant correlation (P > 0.05). The penetration of silver stain indicated a failure of the restorations to seal the cavity and demonstrated a possible pathway by which in vivo post-operative sensitivity could occur. CONCLUSIONS: Although not statistically significant, conditioning of the cavity increased the dentinal permeability but this effect was variable. Thermocycling had no statistically significant effect on microleakage.

In vitro dentinal penetration by tracers used in microleakage studies.

Many microleakage studies, in their methodology, employ different tracers which may penetrate around restorative materials to varying extents due to their physical or chemical characteristics. The present series of in vitro studies were designed to compare the ability of freshly obtained microleakage tracers to enter cut dentinal tubules. Tracers selected were 5% eosin, 2% methylene blue, 50% silver nitrate and Indian ink all buffered, where necessary, to a range of pH 6.9-7.2. The solution of Indian ink was further investigated by particle size analysis to determine the range of particle sizes within the solution. Particles ranged from < 1 micron to 600 microns. Buffered and unbuffered solutions of the tracers were applied for 1 h to open cavities, devoid of a smear layer, prepared in 42 premolars. Specimens were sectioned longitudinally through the cavities either with or without water coolant. Penetration into dentinal tubules by the tracer resulted in an area of stained dentine and this area was subsequently measured using image analysis. The results demonstrated that there were few statistically significant differences between the areas of dentinal penetration associated with each tracer. Neither the tracer used, its pH nor sectioning technique had a predictably significant effect on dentinal penetration. Indian ink was observed to be capable of entering dentinal tubules.