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Biomedical subjects

N H F Wilson

Publications and source records attributed to N H F Wilson.

At least 19 recordsLinked to original sources
PubMed2006

Challenges to teaching posterior composites in the United Kingdom and Ireland.

Recent surveys from general dental practice have found increased placement of direct composite resin restorations in occlusal (Class I) and occlusoproximal (Class II) cavities in permanent teeth by general dental practitioners. This has been matched, and possibly driven, at least in part, by the development of new composite resin materials and bonding technologies. Recent studies by the authors have found an increase in the teaching of Class I and Class II composite resin restorations in the UK, Ireland, the US, and Canada. The increased teaching in the UK and Ireland, however, was not as great as in North America, and several worrying trends were observed. The aim of this paper is to discuss these trends and related factors considered important to the necessary further development of the teaching of Class I and Class II direct composite resin restorations, let alone modern operative dentistry in general, in the UK and Ireland.

Acrylic Resins↗
PubMed2006

A comparison of 2D and 3D finite element analysis of a restored tooth.

The finite element method is widely used in dental research. The decision to use two-dimensional (2D) or three-dimensional (3D) modelling is dependent on many interrelated factors. The purpose of the present study was to compare and contrast 2D and 3D finite element analysis (FEA) in investigating the mechanical behaviour of a maxillary premolar restored with a full crown under similar conditions of axial and lateral occlusal loading. The 2D analysis required modelling both a buccolingual and mesiodistal section of the restored premolar and for comparison sections of a 3D model were examined. Differences in the results for displacement and maximum principal stress distribution within the component structures and interfaces of the 2D and 3D models were, in general, attributable to differences in geometry represented in the models. Maximum principal stresses tended to be greater under lateral rather than axial occlusal loading. It was concluded that 2D FEA may find application in investigating key aspects of the mechanical behaviour of a dental restoration in a single tooth unit, but that in certain situations combinations of 2D and 3D FEA may offer the best understanding of the biomechanical behaviour of complex dental structures. Sophisticated FE models are required to better understand the mechanical behaviour of restored tooth units.

Bicuspid↗
PubMed2006

Teaching of posterior composite resin restorations in undergraduate dental schools in Ireland and the United Kingdom.

PURPOSE: The aim of this study was to investigate the current teaching of posterior composite resin restorations to undergraduate dental students in Ireland and the United Kingdom (UK). The investigation was a follow-up to a survey undertaken in 1997. MATERIALS AND METHODS: A questionnaire was distributed by e-mail to the Heads of Departments of Restorative Dentistry/Units of Operative Dentistry in each of the 15 dental schools with undergraduate dental degree programmes in Ireland and the UK. The questionnaire sought information relating to the teaching of posterior composite resin restorations in each dental school. RESULTS: Fifteen completed questionnaires were returned (response rate = 100%). All schools (n = 15) taught the placement of composite resin restorations in occlusal cavities, 14 schools taught composite resin placement in two-surface occlusoproximal cavities and nine schools taught composite resin placement in three-surface occlusoproximal cavities. Respondents anticipated that the amount of preclinical teaching of posterior composite resin placement will increase twofold over the next 5 years, whilst the corresponding teaching of amalgam will fall to two-thirds its current level. Variation was found between dental schools in the teaching of the principles of cavity design, contraindications to placement, indications for lining and basing techniques, matrix and wedging techniques, and the use of curing lights. CONCLUSIONS: The amount of teaching of posterior composite resin restorations in undergraduate dental schools in Ireland and the UK has increased since the time of a previous survey in 1997. Composite resin may soon equal or overtake amalgam as the material of choice when restoring posterior cavities in Irish and UK dental schools. There was, however, much variation in the nature and extent of the teaching and the techniques taught.

Composite Resins↗
PubMed2005

Influence of explorer tip diameter in identifying restoration margin discrepancies.

OBJECTIVES: Evaluations of the marginal adaptation of restorations in clinical trials rely on subjective assessments by evaluators. The purpose of the present study was to assess the use of dental explorers with different tip diameters to detect simulated marginal discrepancies. METHODS: Using three devices simulating vertical steps, horizontal gaps, and the combination of vertical and horizontal discrepancies and explorers with five different tip diameters, 10 experienced dental faculty members were asked to identify discrepancies at the boundary between Alfa (replacement unnecessarily) and Bravo (replacement questionable) ratings, according to modified United States Public Health Service criteria. RESULTS: A significant correlation was found between the tip diameters of the explorers and the Alfa/Bravo boundaries for the horizontal gaps, but not for the vertical steps. CONCLUSION: It was concluded that the tip diameter of dental explorers had no significant effect on the detection of vertical steps, but had a significant effect on the detection of horizontal gaps. The diagnosis of restoration marginal discrepancies and the rating of marginal adaptation in clinical trials may subsequently be found to be best achieved using techniques other than the probing of restoration margins.

Dental Instruments↗
PubMed2005

Contemporary dental practice in the UK: indirect restorations and fixed prosthodontics.

OBJECTIVES: To investigate, by questionnaire, the use and selection of materials and techniques for indirect restorations and fixed prosthodontics by dental practitioners in the North West of England and Scotland. METHODS: A questionnaire was sent to 1,000 general dental practitioners selected at random from dentists in Scotland and the North West of England. Non-responders were sent another questionnaire after a period of 4 weeks had elapsed. RESULTS: A total of 701 usable questionnaires were returned, giving a response rate of 70%. When selecting a material for the core build-up of vital teeth, practitioners used the following materials (%): amalgam (60), dual and light-cured resin composite (54), glass-ionomer cements (47), compomer (29) and resin-modified glass-ionomer cements (24). Where the use of a post was indicated indirect posts of both precious (67) and non-precious (37) alloys were preferred to prefabricated posts by the majority of practitioners for the restoration of root filled teeth. Direct titanium (14) and stainless steel (14) posts were not used extensively. Impression materials used by the practitioners were as follows: addition-cured silicone (70), condensation-cured silicone (20), polyether (9) and polysulphide (2). Traditional glass-ionomer cements (59) were used for the luting of single and multiple porcelain fused to metal units, with zinc phosphate and polycarboxylate cements (33) being the preferred alternatives. CONCLUSIONS: The majority of the practitioners surveyed in this study used: amalgam for core build-ups; indirect posts; addition-cured silicone for impressions; and glass-ionomer cements for luting procedures.

Crowns↗
PubMed2005

Contemporary dental practice in the UK: demographic data and practising arrangements.

OBJECTIVES: To investigate, by questionnaire, various aspects of primary dental care provision in the North West of England and Scotland. METHOD: A questionnaire containing 79 questions was sent to 1,000 practitioners, selected at random, in the North West of England and Scotland. Non-responders were sent another questionnaire after a period of 4 weeks had elapsed. RESULTS: Overall a response rate of 70% was achieved. The majority of practitioners were practice principals (65%), working in a group NHS practice (80%) located in a city or town centre (49%). On average 10-20 patients were treated each session with fewer patients treated per session under private arrangements. Many practitioners were found to lack hygienist support (44%) and to employ unqualified dental nurses (82%). Younger practitioners were more likely than senior colleagues to have access to up-to-date computers whilst 37% and 74% of respondents never used CAL programmes or magnification respectively. Contemporary cross-infection control standards were used by the majority of practitioners, although 3% of practitioners reported only autoclaving their handpiece once a day. CONCLUSIONS: The majority of practitioners, involved in this study, worked under National Health Service (NHS) regulations as principals in a group practice where the workload was greater than the private/independent sector. Contemporary cross-infection procedures were used routinely. In contrast computer-aided learning programmes and magnification were not used routinely. The practitioners in this study employed significant numbers of unqualified dental nurses.

Anesthesia, Dental↗
PubMed2005

A cohort investigation of the changes in vocational dental practitioners' views on repairing defective direct composite restorations.

OBJECTIVE: To investigate changes in vocational dental practitioners (VDPs) views on repairing direct composite restorations (DCRs) during the vocational training (VT) year 2002-2003. DESIGN: A questionnaire-based cohort study. METHOD: Data on the repair of DCRs, including indications and details of operative techniques were collected by a questionnaire sent at the beginning of the VT year (September 2002) to all 12 Postgraduate Dental Deans in England. A follow-up questionnaire was sent to the Deans near the end of the VT year (May 2003). They were asked, on both occasions, to distribute the questionnaires among their VDPs and to return the completed questionnaires. RESULTS: Ten deaneries participated in the study. The September 2002 and May 2003 findings (306 respondents [66%] and 313 respondents [67%] respectively) were analysed using Chi-square statistic and t-test to identify any significant differences (P<0.05). Significant changes in the attitudes of the VDPs during the VT year included a shift to viewing reduction in treatment time (30% to 48%), cost to patient (12% to 20%) and the management of the partial loss of a restoration (57% to 70%) as indications for repairs. In contrast, there was a significant change in viewing secondary caries as an indication for repair (46% to 29%). In addition, there was a significant, worrisome shift in relation to the use of bonding systems and finishing instruments, together with a reduction in the anticipated longevity of composite repairs. CONCLUSION: Aspects of VDPs' attitudes to the repair of DCRs were found to change significantly during the VT year. Not all aspects of the changes observed were considered to be positive. Knowledge and understanding of repairs to DCRs need to be strengthened.

Administrative Personnel↗
PubMed2005

[Microstructure and mechanical property of a new IPS-Empress 2 dental glass-ceramic].

OBJECTIVE: To investigate the microstructure and mechanical properties of a new IPS-Empress 2 dental glass-ceramic. METHODS: AFM, SEM and XRD were used to analyze the microstructure and crystal phase of IPS-Empress 2 glass-ceramic. The flexural strength and fracture toughness were tested using 3-point bending method and indentation method respectively. RESULTS: IPS-Empress 2 glass-ceramic mainly consisted of lithium disilicate crystal, lithium phosphate and glass matrix, which formed a continuous interlocking structure. The crystal phases were not changed before and after hot-pressed treatment. AFM showed nucleating agent particles of different sizes distributed on the highly polished ceramic surface. The strength and fracture toughness were 300 MPa and 3.1 MPam(1/2). CONCLUSION: The high strength and fracture toughness of IPS-Empress 2 glass ceramic are attributed to the fine lithium disilicate crystalline, interlocking microstructure and crack deflection.

Aluminum Silicates↗
PubMed2004

Contemporary dental practice in the UK: aspects of direct restorations, endodontics and bleaching.

OBJECTIVES: To investigate by questionnaire, the use and selection of materials and techniques for the placement of direct restorations and the provision of endodontics and bleaching by dental practitioners in the North West of England and Scotland. METHODS: A questionnaire was sent to 1,000 general dental practitioners selected at random from dentists in Scotland and the North West of England. Non-responders were sent another questionnaire after a period of 4 weeks had elapsed. RESULTS: A total of 701 usable questionnaires were returned, giving a response rate of 70%. The most commonly used material for the restoration of Class II cavities in premolar and permanent molar teeth was amalgam (n = 605, 86%) and (n = 634, 90%) respectively. Many practitioners (n = 419, 60%) felt amalgam should continue to be used but a majority (n = 374, 66%) remained unconvinced about the merits of amalgam bonding. A minority (n = 63, 9%) of practitioners used predominantly directly placed resin composite rather than amalgam to restore Class II cavities in premolar and permanent molar teeth. Home-based vital bleaching was provided by a significant number (n = 245, 35%) of practitioners with only 18% (n = 123) providing practice-based bleaching. The most commonly used endodontic obturation technique was cold lateral condensation (n = 527, 75%) with 61% (n = 425) of respondents not using rubber dam routinely for endodontics. CONCLUSIONS: For the practitioners in this survey, amalgam was the most frequently selected direct restorative material. Few practitioners used amalgam bonding let alone direct resin composite for posterior restorations. Home-based rather than practice-based bleaching procedures were preferred, as were more traditional endodontic obturation techniques.

Dental Materials↗
PubMed2004

Curricular issues changing from amalgam to tooth-coloured materials.

OBJECTIVE: To provide an overview of curriculum issues in changing from amalgam to tooth-coloured materials. KEY POINTS: Changing from amalgam to tooth-coloured materials in teaching the restoration of posterior teeth may be found to have a considerable enriching effect on the dental curriculum. Subject to meeting a number of prerequisites, the change from amalgam to tooth-coloured materials may cause relatively little curriculum disruption, with the added bonus of a consequential shift from reparative to preservative, minimal invasive dentistry. CONCLUSION: Changing from amalgam to tooth-coloured materials may enrich the typical dental curriculum.

Composite Resins↗
PubMed2004

Finite element analysis of fixed partial denture replacement.

The purpose of this study was to investigate, by means of the finite element method the mechanical behaviour of three designs of fixed partial denture (FPD) for the replacement of the maxillary first premolar in shortened dental arch therapy. Two-dimensional, linear, static finite element analyses were carried out to investigate the biomechanics of the FPDs and their supporting structures under different scenarios of occlusal loading. Displacement and stress distribution for each design of FPD were examined, with particular attention being paid to the stress variations along the retainer-abutment--and the periodontal ligament-bone interfaces. The results indicated that displacement and maximum principal stresses in the fixed-fixed, three-unit FPD were substantially less than those in the two-unit cantilever FPDs. Of the two cantilever FPDs investigated, the distal cantilever design was found to suffer less displacement and stresses than the mesial cantilever design under similar conditions of loading. The highest values for maximum principal stress in the cantilever FPDs were found within the connector between the pontic and the retainer, and within the periodontal ligament and adjacent bone on the aspect of the retainer away from the pontic.

Bicuspid↗
PubMed2004

Biomechanics of cantilever fixed partial dentures in shortened dental arch therapy.

PURPOSE: The purpose of the present study was to investigate, by means of 3-dimensional finite element analysis, aspects of the biomechanics of cantilever fixed partial dentures replacing the maxillary canine in shortened dental arch therapy. The null hypothesis was that no differences would be identified by finite element analysis in the mechanical behavior of the 2 designs of cantilever fixed partial denture under different scenarios of occlusal loading. MATERIALS AND METHODS: Single- and double-abutted cantilever fixed partial dentures were modeled and analyzed using the finite element packages PATRAN and ABAQUS. Displacement and maximum principal stresses (magnitude and location) within the fixed partial dentures, supporting structures, and the periodontal ligament/bone and abutment/retainer interfaces were examined under 20 different scenarios of axial and lateral occlusal loading. RESULTS: The results indicate that more displacement occurred in the 2 rather than the 3-unit cantilever fixed partial denture, with the greatest displacement having occurred under lateral loading. The maximum principal stresses observed in the periodontal ligament/bone interfaces were greatest buccocervically, with the highest value being observed in the 2-unit fixed partial denture under lateral loading. The highest maximum principal stresses observed in the retainer/abutment interfaces were located cervically in relation to the distal margin of the retainer of the 2-unit fixed partial denture under axial loading. CONCLUSIONS: It was concluded that in adopting a cantilever fixed partial denture approach for the replacement of a missing maxillary canine in shortened dental arch therapy, there may be merits, in terms of mechanical behavior, in selecting a double-rather than a single-abutment design. Furthermore, prostheses' displacement and functional stresses may be minimized by reducing lateral loading and avoiding pontic only loading.

Biomechanical Phenomena↗
PubMed2003

New horizons in the regulation of dentistry.

I'm delighted to have the opportunity to share with you my understanding of the much-needed and long-awaited reform of the General Dental Council. Change is moving apace and the new, modern GDC, for which the existing Council has been working so hard, is taking shape as part of widespread fundamental reforms in the regulation of healthcare.

Dental Auxiliaries↗
PubMed2003

The repair of direct composite restorations: an international survey of the teaching of operative techniques and materials.

This article reports the findings of a study on the aspects of the teaching of repair as a conservative alternative to the replacement of failing direct composite restorations (DCRs) in primary dental degree curricula in the UK and Ireland, Germany and Scandinavia. Data on teaching, including operative techniques applied in the repair of DCRs, were collected by means of a questionnaire sent to 58 dental schools in the surveyed countries. Based on the overall response rate of 83%, the findings indicate that the majority (59%) of the schools in the countries surveyed may be found to teach the repair of DCRs. However, marked variations were observed in respect of this teaching and the expected longevity of repaired DCRs. Where the repair of DCRs was not taught, views differed as to the intentions, if any, to include this teaching in the curriculum. It is concluded that the teaching of DCRs may be found to be widespread in dental schools in the UK and Ireland, Germany and Scandinavia, with this teaching being subjected to considerable variation within and between countries.

Composite Resins↗
PubMed2003

Quality of marginal adaptation evaluation of posterior composites in clinical trials.

The evaluation of margins of restorations in clinical trials relies on the subjective assessment of evaluators, with no instrument having been developed, let alone validated, to assist in the process. The purpose of the present study was to assess the quality of evaluations of marginal adaptation by analyzing the distribution of marginal steps rated according to clinical criteria. Replicas of 435 restorations, the marginal qualities of which had been evaluated according to modified USPHS criteria, were randomly selected from the Occlusin multi-center clinical trial program. The marginal step height in the most deteriorated area of each restoration was measured by means of a digital step-height instrument. An overlap between the steps in the restorations with A (Alfa; replacement unnecessary) and B (Bravo; replacement questionable) ratings was found to be in the range of 101 microm to 321 microm. When the steps with a height greater or less than one standard deviation of the mean were excluded, the overlap was reduced to a range of 168 micro m to 173 microm. This finding indicates a marginal height boundary between A and B ratings for marginal adaptation of 170 +/- 3 microm.

Chi-Square Distribution↗
PubMed2002

Systematic review of ceramic inlays.

The purpose of the present study was to conduct a systematic review of ceramic inlays, assess the quality of published clinical studies, and determine the clinical effectiveness of ceramic inlays compared to other forms of posterior restorations. Prospective clinical trials of ceramic inlays published from 1990 to 2001 were retrieved by electronic and hand searching. The methodological quality of each study was assessed by two calibrated reviewers using a standardised checklist. The clinical effectiveness of ceramic inlays was evaluated in terms of failure rate, postoperative pain, and aesthetics. The results were compared to those of other forms of posterior restorations by means of an odds ratio. Among 46 articles selected for quality assessment, only five (10.6%) reported randomised controlled trials and 15 (32.6%) presented controlled clinical trials. The remaining 26 papers (56.5%) were longitudinal clinical trials lacking control groups. Only three papers fulfilled the requirement for statistical analysis to evaluate the clinical effectiveness of ceramic inlays. The results indicate no significant differences in longevity or postoperative sensitivity between ceramic and other posterior restorations over assessment periods of up to 1 year. It is concluded that no strong evidence is available to confirm the clinical effectiveness of ceramic inlays in comparison to other posterior restorations. Greater attention is required to the design and reporting of studies to improve the quality of clinical trials of ceramic inlays.

Clinical Trials as Topic↗