Biomedical subjects

N H Wilson

Publications and source records attributed to N H Wilson.

At least 37 records · Page 2Linked to original sources

PubMed2000

Teaching of posterior composite restorations in Japanese dental schools.

AIM: This study was conducted to assess the teaching programmes for Class I and II composite restorations in Japanese dental schools to obtain an overview of what is being taught, the relative teaching volume, the criteria for the provision of posterior composite restorations and the placement techniques taught. DESIGN: Questionnaire forms mailed to the operative dentistry teaching departments in all 29 Japanese dental schools. RESULTS: The response rate was 93 per cent, with replies from 27 of the 29 dental schools. Twenty-five (93 per cent) responding schools taught the use of Class I and two schools stated that they did not teach the use of posterior composite restorations. One of the two schools had no plan to teach posterior composites within the next five years. The other school did not answer this question. Most schools anticipated that the proportion of teaching time devoted to posterior composite restorations would increase within the next five years. Diversities and similarities between teaching programmes were noted between Japanese, North American and European dental schools, the Japanese programmes being closer to those in Europe than those in North America. CONCLUSION: The diversities in the teaching of posterior composite restorations in Japanese dental schools are as great as in other parts of the world. Such diversities must affect the overall quality of restorations in general practice.

Bicuspid↗

PubMed2000

A chemomechanical method for caries removal.

Over recent years the dental profession has shifted towards practising preventive dentistry and adopting more conservative and tooth-preserving procedures. Such progression is considered to be a response to the decline in the level of dental caries and advances in materials science. This shift in caries management will no doubt continue over the coming decades, based on rational clinical and scientific principles. Chemomechanical caries removal involves the application of a solution that selectively softens the carious dentine, thus facilitating its removal. This limits the removal of sound tooth structure, the cutting of open dentinal tubules, pulpal irritation and pain compared with conventional mechanical methods.

Dental Caries↗

PubMed2000

An evaluation of powder-free gloves in general dental practice.

PURPOSE OF STUDY: To evaluate the suitability of two non-sterile, powder-free gloves for routine use in general dental practice. BASIC PROCEDURES: Randomly allocated blind evaluation of two powder-free gloves by five dentists and five dental nurses in general dental practice. Each dentist and dental nurse were allocated a four-day supply of two unnamed powder-free gloves. Following glove usage a questionnaire sought their views regarding ease of donning, operator comfort, puncture and tear resistance, and tactile sensitivity. Details of procedure undertaken, time of wear and puncture and tear formation for the dentists' gloves were also recorded. The dentists' gloves were retained and subsequently tested for punctures and tears. MAIN FINDINGS: In terms of ease of donning, operator discomfort, tear resistance and tactile sensitivity neither glove was ideal, however one glove was rated higher than the other. Overall, the dentists noticed only half of the punctures and tears detected in the laboratory. One glove was more prone to punctures with the other glove more liable to tear. Time worn in excess of 20 minutes and endodontic procedures were associated with a higher incidence of punctures. PRINCIPAL CONCLUSIONS: The two powder-free gloves evaluated in this study would appear not to be suitable for routine use in general dental practice. Further developments are required before powder-free gloves of the type evaluated can be expected to receive widespread acceptance for routine use by dentists and dental nurses in general dental practice.

Chi-Square Distribution↗

PubMed2000

Techniques used by a group of United Kingdom-based dental practitioners during the provision of indirect tooth-coloured restorations.

A number of techniques involving the use of various instruments, brushes and devices have been described for the removal of excess luting material and subsequent finishing around the margins of indirect tooth-coloured restorations. There is little information available on the clinical techniques employed by UK dental practitioners in the placement of these restorations, or on the effectiveness of these techniques. A questionnaire was designed to elicit such information. This was distributed to 500 UK-based dental practitioners. A total of 301 practitioners returned completed questionnaires, giving a response rate of 60%. The results indicated that 88% of the respondents routinely provided porcelain veneers for their patients, with 94% of these respondents indicating that they routinely prepared teeth during the provision of such restorations. A light-cured resin composite luting material was used by 29% of the respondents in placement of veneers, while 69% used a dual cured composite. Excess uncured luting material was removed by a number of methods and a variety of methods were used by respondents to finish the margins of the veneers after placement. Of the respondents 68% indicated that they routinely provided tooth-coloured inlays and onlays, with 89% indicating that they routinely used a dentine bonding system when luting their indirect tooth-coloured restorations. It is concluded that a high proportion of the practitioners surveyed were providing porcelain veneers and tooth-coloured inlays and that a wide variety of materials and finishing techniques were being used.

Composite Resins↗

PubMed2000

Efficacy of preformed metal crowns vs. amalgam restorations in primary molars: a systematic review.

BACKGROUND: The authors evaluated the treatment efficacy of preformed metal crowns, or PMCs, vs. amalgam restorations in primary molars by means of a literature review and meta-analysis. TYPES OF STUDIES REVIEWED: From a literature search, the authors selected clinical studies that evaluated treatment with PMCs vs. amalgam control restorations in primary molars and provided data against which treatment outcomes could be compared. RESULTS: Ten studies with durations ranging from 1.6 to 10 years fulfilled the selection criteria. Their failure rates, based on need for subsequent treatment or retention of the restoration at final evaluation, ranged from 1.9 to 30.3 percent for PMCs and 11.6 to 88.7 percent for amalgam restorations. Overall, PMCs demonstrated greater longevity and reduced retreatment need compared with amalgam control restorations. The odds ratio for all studies fell within the boundary favoring treatment with PMCs. CLINICAL IMPLICATIONS: Analysis of the literature, though mainly retrospective studies, demonstrated evidence of a more favorable outcome for PMCs than for amalgam restorations in primary molars requiring multisurface restorations.

Crowns↗

PubMed2000

Methyl bromide 1-year dietary study in dogs.

Average human exposure resulting from consumption of methyl I bromide (MB)-fumigated food has been estimated to be 0.00125 mg/kg/day. A 1-yr feeding study in beagle dogs was conducted as a safety study in which the high-dose diet was intended to yield a methyl bromide dose of at least 100 times the calculated human dietary exposure. Diets were fumigated with MB and fed to the dogs daily, except for weekends and holidays. MB consumption each feeding day was calculated as a time weighted average (TWA) that accounted for the rate of degassing from the fumigated diet and the rate of feed consumption during the feeding period. TWA compound consumption in the loss-, mid- and high-dose groups, respectively, averaged 0.06 ¿ 0.02, 0.13 ¿ 0.03 and 0.28 ¿ 0.08 mg/kg/day in males and 0.07 ¿ 0.03, 0.12 ¿ 0.03 and 0.27 ¿ 0.09 mg/kg/day in females. Clinical observations, body weight and feed consumption, ophthalmology, clinical pathology, urinalysis, organ weights and macroscopic and microscopic pathology were comparable in control and MB-treated dogs. Under the conditions of this study. the no-observed-effect level (NOEL) for MB was at least 0.28 mg/ kg/day, or approximately 200 times the expected average human dietary exposure.

Administration, Oral↗

PubMed2000

A comparison of the marginal and internal adaptation of amalgam and resin composite restorations in small to moderate-sized Class II preparations of conventional design.

OBJECTIVE: The purpose of this study was to compare the marginal and internal adaptation of a non-gamma-2 amalgam and an ultrafine compact-filled light-cured composite in small to moderate-sized Class II restorations of conventional design. METHOD AND MATERIALS: Fifty recently extracted human premolar and permanent molar teeth were selected for the study. The teeth were restored with either a non-gamma-2 amalgam alloy or a light-cured resin composite. The marginal adaptation of the restorative materials to the proximal surface outline form of each preparation was assessed. The mean percentages of perfect margins, marginal fissuring, and underfilled margins for the 2 restorative materials were recorded and statistically analyzed. RESULTS: Both materials performed equally well in the buccal and lingual segments of the proximal box. At the cervical margin, the resin composite restorations showed a significantly greater number of imperfect margins and marginal fissuring. The incidence of underfilled margins was low for both restorative materials even at the cervical margin. CONCLUSION: Although there was some cause for concern about the marginal adaptation of the resin composite restorations along the cervical margin, the findings support contemporary teaching that small to moderately sized conventional Class II preparations may justifiably be restored with an appropriate resin composite.

Analysis of Variance↗

PubMed2000

A clinical evaluation of Class II composites placed using a decoupling technique.

PURPOSE: This study was undertaken to evaluate the three-year clinical performance of Class II restorations of a fine particle hybrid composite placed using a decoupling placement technique, whereby polymerization shrinkage stresses at the cervical tooth-restoration interface were minimized by separating the initial gingival increment of composite from the body of the restoration using a polyurethane varnish. MATERIALS AND METHODS: The study was a practice-based explanatory, single-center clinical trial. A minimum of 40 Class II restorations of the material under investigation (Tetric) was required to be placed in predominantly molar teeth in selected patients. The restorations were placed using a decoupling incremental technique, bonding being accomplished using Syntac and Heliobond. The restorations were reviewed within 1 month of placement, thereafter at 18 months, then at 2 and 3 to 4 years using predetermined codes and criteria. Impressions and photographic records were used to obtain retrospective, third-party assessments of the restorations. RESULTS: Of 43 restorations originally placed and found to have ideal characteristics at baseline review, 41 (95%) were reviewed at 18 months, 36 (84%) at two years, and 31 (74%) at 3 to 4 years. None of the restorations were found to have suffered significant deterioration, notwithstanding three restorations having been lost to the study because of the replacement of part of the restored tooth for causes other than the catastrophic failure of the material. No secondary caries or postoperative sensitivity was recorded. CONCLUSION: It was concluded that the findings support the use of the material under investigation in the restoration of moderate- to large-sized Class II preparations in selected patients. The decoupling placement technique employed may be found to be an effective means to limit postoperative sensitivity and to contribute to the favorable in-service performance of restorations of the type investigated. Good practice would now require a multicentered, randomized controlled trial to investigate the effectiveness of the material and, in particular, the decoupling technique under the conditions of everyday practice.

Acrylates↗

PubMed1999

Procera all-ceramic crowns: a new approach to an old problem?

Increasing patient expectations regarding the appearance of restorations continue to test the ingenuity and skill of the dental team. To this end the quest for sufficiently strong, metal-free, all-ceramic restorations to function in all areas of the mouth continues apace. We report on a possible solution to this problem that uses computer-aided design/computer-aided milling (CAD/CAM) technology coupled with a novel, densely sintered, ceramic material. In this article we offer suggestions for case selection, preparation design, and luting procedures, and in addition illustrate these with a number of completed cases.

Adult↗

PubMed1999

The development of resin-bonding for amalgam restorations.

Adhesive techniques are now used for many dental restorative materials, including amalgam. Several generations of dentine bonding agents have been developed, mainly for bonding composite resins. When bonding is used with amalgam restorations, the need for retention and resistance form is reduced, the seal is improved, and some procedures, such as amalgam sealants, which were not previously possible, can be considered.

Acid Etching, Dental↗

PubMed1999

The aetiology of the non-carious cervical lesion.

Erosion and abrasion have been widely reported as causes of non-carious cervical lesions (NCCL). However, more recently, tooth flexure has been implicated in the formation of these lesions generating renewed interest in the pathogenesis of the non-carious loss of cervical tooth substance. This paper considers the causes of erosion and abrasion, related to modern lifestyles, and reviews the literature concerning tooth flexure as a cause of NCCL. A description of different types of NCCL is given, as an aid to determining the aetiology, yet at the same time accepting that the causation and pathogenesis of NCCL is probably multi-factorial resulting in many different clinical presentations. Consideration is given to the indications for treatment of NCCL and to the selection of materials for restoring such defects.

Dental Materials↗

PubMed1999

Fracture resistance of teeth restored with onlays of three contemporary tooth-colored resin-bonded restorative materials.

STATEMENT OF PROBLEM: There are uncertainties regarding the use of large indirect composites and ceramics in the restoration of posterior teeth. PURPOSE: This study investigated the fracture resistance of teeth restored with restorations of 3 contemporary resin-bonded tooth-colored materials placed in a standardized onlay preparation. MATERIAL AND METHODS: A random sample of preparations for tooth-colored onlays was obtained from a full service dental laboratory. A preparation was then duplicated in 30 natural teeth by copy milling. An additional 10 teeth were not prepared, and acted as a control. Ten onlays of each of the 3 materials (Belle Glass, SR Isosit, and Empress) were produced and resin bonded into place according to the manufacturers' instructions. The restorations were compressively loaded to fracture and the mode of failure recorded. RESULTS: The fracture resistances obtained for the teeth restored with the composite material (mean 1.56 kN; SD 0.54) were greater than those obtained for the teeth restored with the ceramic material (mean 0.99 kN; SD 0.49) and the fiber-reinforced composite material (mean 0.99 kN; SD 0.56). CONCLUSION: Teeth restored with composite onlay restorations demonstrated a higher fracture resistance than equivalent sized onlay restorations produced from fiber-reinforced composite or a ceramic material. Failure under compressive loading may be found to be less catastrophic when a fiber-reinforced composite rather than a composite or ceramic material is used.

Acrylic Resins↗

PubMed1999

Comparison of two stylus methods for measuring surface texture.

OBJECTIVES: The purpose of this study was to evaluate and compare two "stylus" methods for measuring surface texture of dental tissues and materials. METHODS: The two styli chosen were a contact diamond stylus and a non-contact focussed laser stylus attached to the same measuring apparatus. RESULTS: These indicate that there are significant differences between those obtained from surface texture measurements using a non-contact laser stylus and a diamond contact stylus method despite being mounted in the same profilometer. This is valid for both the test specimens of known surface texture, provided by the manufacturers, and for a "real world" simulation using contoured and finished Dicor ceramic blocks. The only significant agreement between the two styli was found for the Ra parameter. This should not be used alone to describe the roughness of a surface because the parameter is not sensitive to profile shape. Owing to the properties of the stylus used it is essential that the limitations of surface profilometry be recognised. SIGNIFICANCE: Caution should be exercised when comparing the results of surface texture studies of dental hard tissues and restorative materials using varying types of stylus attached to a surface profilometer.

Dental Equipment↗

PubMed1999

Mechanical properties of direct core build-up materials.

OBJECTIVE: This work was undertaken to measure mechanical properties of a diverse group of materials used for direct core build-ups, including a high copper amalgam, a silver cermet cement, a VLC resin composite and two composites specifically developed for this application. METHODS: Compressive strength, elastic modulus, diametral tensile strength and flexural strength and modulus were measured for each material as a function of time up to 3 months, using standard specification tests designed for the materials. RESULTS: All the materials were found to meet the minimum specification requirements except in terms of flexural strength for the amalgam after 1 h and the silver cermet at all time intervals. SIGNIFICANCE: There proved to be no obvious superior material in all respects for core build-ups, and the need exists for a specification to be established specifically for this application.

Analysis of Variance↗

PubMed1999

Clinical evaluation of a posterior composite 10-year report.

OBJECTIVE: The 10-year findings of one of the studies which comprised the multicentre clinical evaluation of a light-cured posterior composite restorative are reported, with special emphasis on the reasons and timing of failure of restorations included in the study. Effects of the use of rubber dam or cotton rolls and aspiration for isolation at the time of placement are considered. METHOD: One hundred Class I and II restorations of the resin composite investigated were placed by a single operator in a group of selected, predominantly young-adult patients under highly controlled conditions, with the use of rubber dam or cotton rolls and aspiration for isolation being determined according to a scheme of randomisation. The restorations were reviewed clinically after 1 week and within 1 month of placement (baseline) and, thereafter, at 6 months, 1, 2, 3, 4, 5, 6 and 10 years using modified USPHS codes and criteria. Epoxy models and photographs were obtained for retrospective analysis. RESULTS: After 10 years, 37 restorations were reviewed and 32 restorations were known to have failed. Regarding the reasons for failure, loss of occlusal anatomic form during the first 5 years and loss of approximal contacts near the end of the study accounted for most of the failures. Only two failures were attributed to recurrent caries. Few of the restorations found to be clinically satisfactory at 10 years had retained ideal functional characteristics. Location, Class and size of restoration and the method of isolation were not found to significantly influence 10-year performance and survival. CONCLUSION: The actual 10-year failure rate, estimated to have been between 40 and 50% is considered to have been high, notably given the limited incidence of recurrent caries and bulk fracture. However, the findings indicate that certain restorations of the material investigated, despite the use of outdated operative techniques, may be found to perform satisfactorily over periods in excess of 10 years.

Adult↗

PubMed1999

British Isles symposium on the future of dental clinical skills training.

A symposium on the future of dental clinical skills training is reported. Abstracts of the symposium presentations review the current and future use of simulation in dental education, future skills training in the creation of new dentists, equipment and methods for simulation, the transition from simulation to clinical practice and recent developments in simulation employing new technologies. The report concludes that simulation will continue to have an important, probably increasing role in dental education, and that further developments in clinical skills training should be sensitive to changing patterns of dental disease and opportunities of provide clinical instruction.

Clinical Competence↗

PubMed1999

Clinical testing of restorative materials: some historical landmarks.

OBJECTIVES: The aim of the study was to review the historical background of the methodologies currently in use for clinical investigations of contemporary tooth coloured dental restorative materials and techniques, and to attempt to identify the likely general direction of such research projects in the future. DATA SOURCES: Published articles obtained as a result of a wide ranging literature search of both dental and medical journals. STUDY SELECTION: Historical and contemporary accounts of clinical trial management, upon which an overview of the key events important in the evolution of clinical methods of evaluation of dental restorative materials, and a prediction of possible future trends in this area, could be based. CONCLUSIONS: Publication of dental restoratives clinical research has not kept up with that in medicine, where editors of leading journals require that clinical trials be run in accordance with the Consolidated Standards of Reporting Trials (CONSORT) guidelines. The current trend towards evidence based treatment in dentistry can be expected to initiate more statistically powerful clinical studies of dental restoratives, and the merit of involving general dentists in practice based research can also be anticipated to become increasingly recognised in the future.

Clinical Trials as Topic↗

PubMed1999

A 2-year inhalation study of phosphine in rats.

Phosphine is a highly toxic gas used as a fumigant, a dopant in semiconductor manufacturing, and in the production of organophosphines. In a chronic toxicity and oncogenicity study of phosphine, 60 male and female F344 rats per group were exposed via whole-body inhalation for 6 h/day, 5 days/wk for up to 104 wk to mean concentrations of 0, 0.3, 1, or 3 ppm phosphine. Three parts per million was considered the maximum exposure level because of lethality seen at higher exposure levels in previous repeat dose studies. Ten rats per sex per group were sacrificed after 52 wk of exposure. Survivors were sacrificed after 104 wk of exposure. There were no phosphine-related effects seen on clinical observations, body weight, food consumption, hematology, clinical chemistry, urinalysis, or ophthalmology. There were no phosphine-related macroscopic findings or effect on absolute or relative organ weights. No histomorphologic alterations attributable to phosphine exposure were seen. In conclusion, under the conditions of this study, there were no treatment-related changes suggestive of a toxic or carcinogenic effect seen in rats following 52 wk or 2 yr of whole-body inhalation exposure to 0.3, 1, or 3 ppm phosphine.

Animals↗