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.

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

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.

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.

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.

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.

An in vitro comparative analysis: scanning electron microscopy of dentin/restoration interfaces.

One hundred maxillary premolar teeth were randomly allocated to ten groups. Each group was restored with one of ten different restorative techniques. The teeth were stored in deionized water for 7d prior to longitudinal sectioning in a mesio-distal plane. Following sectioning, ten specimens from each group were chosen at random from the 20 available sections. The sectioned surfaces were polished using 600-grit SiC abrasive paper and etched for 10 s with 50% phosphoric acid to remove the smear layer produced by sectioning. Five tooth sections from the dentin bonding resin groups were allowed to dry at 20 degrees C for 24h. The glass ionomer-based groups were reimmersed in deionized water during this period. The remaining five sections from each group were replicated using an addition-cure vinyl polysiloxane impression material and an epoxy resin. A comparison was made of the sections and the replicas. All tooth specimens were sputter-coated with gold for 4 min and examined using a scanning electron microscope. Replicas were gold-coated for 3 min. Different tooth/restoration interfaces, associated with different materials, were observed. A marked difference between the replicas and tooth sections was observed for glass ionomer-based restorations but not for resin-based bonding systems. Representative samples of replicas and specimens are shown, and the significance of the observed differences is discussed.

In vitro microleakage associated with posterior composite restorations used with different base/bonding system combinations.

The study aimed to determine the base/restoration combination which allowed the least microleakage in Class II cavities. One hundred premolar teeth were prepared with a standardized, minimal two-surface cavity and randomly ascribed to ten equal groups. The cavities were restored by use of one of ten different material/technique combinations. Restored teeth were sealed to within 1 mm of the restoration margins with nail varnish prior to the immersion of the crowns in 5% (buffered) eosin for 48 h. The teeth were then hemisected longitudinally, in a mesio-distal plane, through the midline of the restoration by means of a diamond disc with water coolant, and one half of each tooth was then photographed. The transparencies were examined by image analysis programmed to facilitate calculation of the percentage of the tooth/restoration interface and of the crown dentin exhibiting dye penetration. Light- and chemically-cured glass-ionomer-based restorations showed similar amounts of leakage when expressed as a percentage area of crown dentin. This was significantly (p less than 0.05) less than that shown by cavities both etched and bonded. Cavities restored without enamel etching or involving the use of a bonding system exhibited significantly (p less than 0.05) greatest leakage.

A technique for three-dimensional microleakage assessment using tooth sections.

Microleakage is commonly assessed using restored teeth, sectioned through the midline of the restoration. It is impossible to determine if this is representative of the leakage throughout the whole tooth. This pilot study examined the feasibility of calculating areas and volumes of leakage using serial sections of restored teeth which had been subjected to dye immersion and image analysis. Using the sections, perspex models of the teeth were constructed to present the pattern of the dye leakage into dentine. This appears to be a viable technique for the three-dimensional assessment of microleakage.

Current status of the cast metal inlay: a survey of dental schools in the UK and Hong Kong.

This study reports on the current status of the gold inlay in the undergraduate curriculum of Dental Schools in the UK and at the Prince Philip Dental Hospital, Hong Kong, to determine if the decline in the use of the cast gold inlay over the past 20 years is reflected in teaching at undergraduate level. A questionnaire, which was mailed to all the heads of departments of conservative dentistry in the UK, was designed to determine current teaching in respect of cast inlays. The results show that although the majority of UK dental schools continue to teach direct and indirect inlay techniques, a minority (4 and 5 respectively) no longer incorporate a practical exercise in this teaching. Reasons cited for the discontinuation of the technique are varied but the availability of simpler, more conservative techniques is emphasized. Examination of the treatment records at the Prince Philip Dental Hospital, Hong Kong, where the Class II inlay technique is taught both theoretically and practically, shows that only a small proportion of all posterior cast restorations fitted between May 1983 and April 1988 were inlays (4.6 per cent).

In vitro marginal microleakage: examination of measurements used in assessment.

Premolar teeth with Class II amalgam restorations placed after the application of cavity varnish (Group A), a light cured glass ionomer base (Group B) and 40 per cent polyacrylic acid as a pretreatment agent, followed by unset cermet cement (Group C) were examined for marginal leakage using dye penetration and image analysis. Including amongst the parameters examined were linear leakage length and leakage area, which were found to have no consistent correlation. Group A and C did not generally show significant differences in the parameters examined, whereas Group B exhibited significantly less linear leakage (P less than 0.001), and significantly less leakage area when the stained area was expressed as a percentage of available dentine (P less than 0.001). While allowing some linear leakage, it was found that the light cured glass ionomer base appeared to prevent the dye from entering the dentine. It is concluded that an assessment based solely on the leakage length is inadequate and that some measurement of penetration into dentine should be included in order to fully assess the microleakage potential of a material or technique.

In vitro marginal microleakage associated with five dentine bonding systems and associated composite restorations.

Fifty sound premolar teeth, extracted for orthodontic purposes and stored at room temperature in physiological saline since extraction, were prepared with a standardized minimal two-surface Class II cavity. The teeth were then ascribed randomly to five groups, each of ten teeth. Each of four groups was restored using a different dentine bonding system and the associated posterior composite resin according to the manufacturer's instructions. The fifth group was restored with Superbond C & B dentine bonding system and Occlusin composite. After immersion in de-ionized water for at least 7 days, the teeth were sealed with nail varnish to within 1 mm of the margin of the restoration. The teeth were then immersed in 5 per cent buffered Eosin for 48 h. Following mesiodistal sectioning the sections were photographed and subjected to image analysis to establish the length of dye penetration at the tooth/restoration interface and the amount of dye penetration into the crown dentine. Tripton/Occlusin and XR Bond/Herculite XR groups showed a significantly (P less than 0.05) smaller amount of leakage than Gluma/Lumifor or Scotchbond 2/P50 combinations when assessed as a percentage of the tooth/restoration interface exhibiting leakage. When the percentage of crown dentine showing dye penetration was considered, the Tripton/Occlusin group showed less leakage than the other material combinations. It is concluded that Tripton, when used with the recommended composite, will allow significantly less microleakage than Gluma/Lumifor, Scotchbond 2/P50 or Superbond C & B/Occlusin combinations and a similar amount to XR Bond/Herculite XR in vitro.

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.

An in vitro assessment of tooth preparation for porcelain veneer restorations.

OBJECTIVES: This in vitro study aimed to examine the depth of preparation and incidence of dentine exposure resulting from the use of a 'freehand' technique to prepare maxillary central incisors for porcelain veneers. METHODS: Twenty-two maxillary central incisors were selected. Prior to preparation an index of the labial surface of each tooth was recorded and the tooth secured in a jig to permit accurate relocation. Two operators each prepared 11 teeth aiming to reduce the labial thickness evenly by 0.5 mm. Low viscosity silicone impression material was then placed on the index and the teeth relocated into the jig. Upon removal, this material was sectioned in the cervical, middle and incisal thirds of the tooth and its thickness measured using a toolmaker's microscope. The teeth were acid etched and also stained with a dentine dye to identify any area of dentine exposed during preparation. RESULTS: Significant differences (P < 0.001) in the depth of preparation at different sites, with least reduction in the mid-incisal region, were found. Greater reduction was found at the cervical and proximal margins with areas of dentine exposed at those sites in the majority of teeth. CONCLUSIONS: In view of the incidence and position of dentine exposure found in this study, the use of a dentine bonding system during the placement of porcelain veneers would appear essential when employing a 'freehand' preparation technique.

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 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.

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.

Speed variability of air-driven motors in the self-threading pin technique.

Effective pin placement is dependent upon correct preparation of the dentine channel. Various factors contribute to the success or otherwise of this channel preparation. One such factor is the rotational speed of the twist drill. It is widely recommended that the twist drill be operated within the 500-800 rpm speed range, in order to prevent a temperature rise in the pulp during the cutting process. This paper examines the ability of air-driven dental motors, when coupled to two speed-reduction handpieces with differing reducing ratios, to operate within this range. The results reveal a wide variation in the speed ranges of the motors tested. Of the two types of handpiece examined, it appears that a 10:1 speed reduction is appropriate for the majority of motors.

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.

In vitro fracture fixation: adhesive systems compared with a conventional technique.

To find out whether adhesive techniques could have a role in bone fixation in selected cases an in vitro comparison between the current 'Champy' miniplate system and bonded stainless steel was undertaken using cyanoacrylate or dental composite cement. 33 bovine ribs were sectioned to simulate fracture separation, divided randomly into three groups, and immobilised by one of the three treatments. Distraction across the 'fracture' was produced using a universal testing apparatus, and forces at failure were recorded in Newtons (N). Image analysis enabled the contact area of the adhesive to be determined in mm2, so the bond strength in N/mm2 was derived. The Champy system failed at a significantly greater force (N) than the adhesives (p = 0.000). There was no significant difference in bond strength between either of the adhesive systems tested.