Managing the Unstable Mandibular Complete Denture ­ Tooth Placement and the Polished Surface.

Constructing satisfactory conventional mandibular complete dentures is often challenging in comparison to the upper counterpart partially due to differences in the anatomy of the denture-bearing area. This problem is exaggerated in the atrophic mandible, where supporting structures are frequently ill-defined and suboptimal in quality. Implant-retained prostheses offer well recognized benefits but are not always a feasible options, so conventional methods must be relied upon. The importance of impression quality and registration has been reviewed previously. This article aims to discuss the influence of tooth placement, the polished surfaces and the neutral zone on the success of lower dentures. Clinical relevance: This article highlights the importance that polished surface contouring and tooth prescription can have on the outcome of lower dentures. Techniques for assessing and recording the neutral zone are explained, along with alternative occlusal schemes.

Summary of: the influence of specialty training, experience, discussion and reflection on decision making in modern restorative treatment planning.

AIMS: This study was designed to determine the effect of reflection and discussion of a group of dentists with differing backgrounds and qualifications in the management of failed endodontic treatment. MATERIALS AND METHODS: During the Dental Pan-Society plenary session (16-17 November 2007) delegates (n = 393) were asked a series of questions on the management of a case with failed endodontic treatment of four maxillary incisors restored with linked crowns in a patient with a high smile line. The case had been previously posted on the conference website in addition to being presented on the day of the forum. Responses of delegates to predetermined questions and options on the management of the case were recorded using closed-circuit devices for each individual delegate. The questions were repeated after the case was opened up for discussion by the delegates in conjunction with a panel of leading experts. The discussion topics included the factors affecting the outcome of secondary root canal treatment, post-extraction changes and the options for prosthetic replacement including the provision of implants in the aesthetic zone. RESULTS: The initial response of the majority (58%) of delegates favoured extraction and prosthetic rehabilitation over endodontic retreatment of the affected teeth. Following the discussion this figure reduced to 50%. In respect to those individuals who were specialists, extraction was again the preferred option before the discussion for periodontists (74%), prosthodontists (64%) and restorative dentists (65%). This was in contrast to endodontists who preferred endodontic retreatment, with only 30% identifying extraction as the treatment of choice. Following the discussion, the number of periodontists and endodontists who favoured extraction reduced by 3% and 5% respectively, whereas the number of prosthodontists and restorative dentistry specialists who preferred extraction increased by 2% and 4% respectively. CONCLUSION: Reflection and discussion can make individuals reconsider their initial treatment decisions. These personal skills may become more significant when planning treatment for complex restorative cases.

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.

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.

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

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.

Posts and the root-filled tooth.

It is clear that teeth often require significant reconstruction following root canal treatment. It is also evident that there is an enormous variety of ways that can be used to achieve this. Although there is some debate about the relative contributions of the root filling and coronal restoration to endodontic success, it is agreed that the best results are gained with a good root filling and a well-sealed coronal restoration. Posts, pins and/or bonding are all possible solutions to retain the coronal restoration but it is often difficult to decide, on the basis of evidence rather than fashion or anecdote, which is preferable.

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.