Search PubMed⌕ Search

Biomedical subjects

N H Wilson

Publications and source records attributed to N H Wilson.

At least 55 records · Page 3Linked to original sources
PubMed1999

Development of noncarious cervical notch lesions in vitro.

PURPOSE: The initiation and progression of noncarious cervical notch lesions (NCCL) continues to perplex clinicians worldwide and poses a considerable restorative challenge. The purpose of this brief communication is to report what is believed to be the first in vitro production of notch-shaped lesions in the cervical third of premolar teeth. MATERIALS AND METHODS: The lesions, were produced by axial loading of selected permanent premolar teeth in a 10% aqueous solution of sulfuric acid over a period of 5 days, followed by immersion in water for 7 days. RESULTS: Results revealed macroscopic and microscopic features similar to those observed in noncarious cervical lesions in vivo. The lesions were incidental findings while the authors were studying stress corrosion of enamel at low pH. Although much remains to be investigated regarding the etiology and pathogenesis of NCCL, axial loading and a corrosive environment may be implicated in these processes. The artificial lesions arose in clinically sound teeth, suggesting that there is no simple clinical examination to identify teeth at risk from NCCL. CLINICAL SIGNIFICANCE: The relationship between the development of NCCL and applied stress indicates that occlusal factors may play the most significant role in the initiation and progression of NCCL.

Bicuspid↗
PubMed1999

Glass-ionomer restoratives: a systematic review of a secondary caries treatment effect.

It is generally accepted that glass ionomers inhibit secondary caries in vivo, and data from in vitro studies support this effect. The aim of this review was a systematic assessment, from the literature, of clinical evidence for the ability of glass-ionomer restoratives to inhibit secondary caries at the restoration margin. Inclusion and exclusion criteria for selection of the review papers were established prior to commencement of the literature search. Papers which conformed to these criteria, and reported on secondary caries as an outcome, were selected (N = 52). Primary and secondary lists of systematic criteria for use in the assessment of the papers were drawn up. The primary list of 14 criteria was applied to each paper. No paper fulfilled all these criteria, necessitating the use of the secondary measures: (i) a prospective study and (ii) use of an appropriate control. This yielded 28 papers. Tabulation of these papers by occurrence of secondary caries in the glass-ionomer or control groups demonstrated an even distribution between positive and negative outcomes. Valid evidence is considered to be best obtained from randomized, controlled studies of sufficient sample size. No conclusive evidence for or against a treatment effect of inhibition of secondary caries by the glass-ionomer restoratives was obtained from the systematic review. There is a need for appraisal of the methods currently adopted for the clinical evaluation of glass-ionomer restorative materials, and for further development of the methodology to support future systematic reviews.

Dental Caries↗
PubMed1999

Restoration longevity and analysis of reasons for the placement and replacement of restorations provided by vocational dental practitioners and their trainers in the United Kingdom.

OBJECTIVE: This study examined the reasons given by vocational dental practitioners and their trainers for placement and replacement of restorations. METHOD AND MATERIALS: Each participant was asked to record the reason for placement or replacement of restorations. The age and class of the restoration being replaced were also recorded, as was the material being used and the material being replaced (if known). RESULTS: Details of the reason for placement or replacement was received on 9,031 restorations. Of the restorations placed, 53.9% were amalgam, 29.8% were resin composite, and 16.3% were glass-ionomer cement. The reasons for placement or replacement of the restorations were principally primary caries (41.3%), secondary caries (21.9%), tooth fracture (6.4%), marginal fracture or degradation (6.1%), and noncarious defects (5.8%). Of the amalgam restorations, most were placed to restore Class II and Class I preparations (65.8% and 29.9%, respectively). Of the composite restorations, most were placed in Class III and Class V cavities (35.5% and 26.3%, respectively). Glass-ionomer cement was used predominantly to restore Class V cavities (63.5%). CONCLUSION: Secondary caries was the most prevalent reason for replacement of restorations, regardless of material. Statistical analysis indicated that amalgam provided significantly greater longevity than composite or glass-ionomer materials.

Clinical Clerkship↗
PubMed1999

A short-term clinical evaluation of a tricure glass-ionomer system as a transitional restoration and core buildup material.

OBJECTIVE: A general dental practice study investigated the use of a resin-modified glass ionomer material as a transitional restoration and as a core buildup material. The study also assessed a resin-modified glass-ionomer luting system. METHOD AND MATERIALS: Fifty-one badly broken-down vital permanent molar teeth in 44 patients were restored. No dentin pins were placed; however, preexisting pins were retained in 7 teeth. Following baseline and 3-month assessments, complete veneer gold crowns were placed on the selected teeth. The preparations involved ferruling in sound tooth tissue. The completed crowns were reviewed 3 and 12 months after placement. Modified US Public Health Service criteria were used for assessment throughout. Clinical assessment was complemented by examination of photographic records and replicas obtained from silicone impressions. RESULTS: All 51 transitional restorations were found to be clinically satisfactory at the 3-month review. Nineteen (37%) transitional restorations had limited defects that were eliminated in crown preparation. Of the 51 permanent crowns, 46 (90%) were reviewed at 3 months and 44 (86%) at 1 year. All the crowns reviewed at 3 and 12 months were clinically satisfactory. The luting system investigated showed favorable handling characteristics and excellent short-term performance. CONCLUSION: The materials investigated are, over a period of at least 12 months, effective in the restoration of broken-down molar teeth destined to be crowned. With the use of these materials and ferruling, the use of dentin pins may be unnecessary in selected cases.

Adolescent↗
PubMed1999

Reasons for the placement and replacement of restorations in vocational training practices.

AIM: The reasons for placement and replacement of restorations are central to clinical practice. It is the purpose of this paper to assess the reasons for placement and replacement of restorations in the practices of vocational dental practitioners (VDPs) and their trainers. METHOD: VDPs and their trainers were invited to take part in the study. VDPs were asked to record the principal reason for the placement or replacement of all restorations which they provided for a one-month period and, also, to record the age, Class and materials used for each restoration replaced (if known). Trainers were also asked to participate. The data thereby collected were analysed statistically. RESULTS: 56 VDPs and 17 trainers participated. Data were obtained on a total of 9031 restorations, 4423 (49%) being initial placements and 4608 (51%) replacements. Of the total number of restorations assessed, 54% were amalgam, 30% composite and 16% glass ionomer. Principal reasons for placement/replacement of the restorations were primary caries (41%), secondary caries (22%), tooth fracture (6%), margin fracture/degradation (6%), non-carious defects (6%) and bulk fracture (5%). The type of existing restorative material was recorded for 4196 restorations: secondary caries was the most common reason for the replacement of restorations--for 46.0%, 39.6% and 39.8% of amalgam, composite and glass-ionomer restorations respectively. VDPs placed more restorations as a consequence of caries than their trainers. CONCLUSION: Primary caries is the most common reason for the placement of restorations by the participating dentists, and secondary caries is the most common reason for the replacement of restorations of amalgam, composite and glass ionomer. VDPs placed more restorations as a consequence of caries than their trainers.

Dental Caries↗
PubMed1999

The provision of resin-bonded bridgework within the General Dental Services 1987-1997.

The purpose of this study was to investigate the performance of resin-bonded bridgework provided within the General Dental Services of the National Health Service. The basic procedure involved analysis of data collected from the administering authorities in England, Wales and Scotland between 1987 and 1997. These figures included the cost of the provision of such bridgework and the incidence and cost of refitting bridges which had become debonded in service. The investigation found that while the number of resin-bonded bridges provided had peaked in the early 1990s the number of claims for rebonding was still increasing at a high rate. In the most recent year of the study (1996/97) the number of claims for rebonding bridges was 50% more than the number of bridges actually fitted during that year. It was concluded that resin-bonded bridgework provided under the General Dental Services of the National Health Service was experiencing a high failure rate and that this problem was worthy of further investigation.

Costs and Cost Analysis↗
PubMed1999

Demonstration of "vertical barrelling" using profilometry.

The aim of this study was to demonstrate the extent of tooth flexure under axial loading using profilometry. Fifteen extracted human permanent upper premolar teeth were embedded in hard die stone and divided into 3 groups. One group was left unprepared, the second group had artificial cervical saucer shaped lesions prepared and the final group had artificial cervical notch lesions prepared. The labial profile was taken using a diamond stylus mounted in a Profilometer. The teeth were then loaded in an axial direction to circa 670 N and the labial surface re-profiled 20 s after loading. The results indicate that changes occur in the labial profile of premolar teeth that are subjected to axial loading which could be considered to represent vertical barrelling. Changes in the profile of the artificial saucer and notch lesions prepared at the cervical region suggest that stresses would be generated on restorations of these lesions.

Bicuspid↗
PubMed1999

A two-year randomized, controlled clinical evaluation of bonded amalgam restorations.

PURPOSE: The clinical performance of adhesively bonded dental amalgam restorations was compared with that of traditionally placed non-bonded control amalgams in a randomized prospective study. MATERIALS AND METHODS: One-hundred thirteen Class II Dispersalloy amalgams were placed in permanent molars and premolars of 31 (21 males, 10 females) human subjects with their informed consent. By random assignment, 60 amalgam restorations were adhesively bonded using ED Primer and Panavia 21 TC (both Kuraray Co, Japan), and 53 traditional non-bonded restorations were placed. Most preparations involved replacement of defective amalgam restorations. Clinical recalls were conducted by experienced evaluators using modified USPHS criteria for occlusal and proximal anatomic form, occlusal and proximal marginal adaptation, and occlusal and proximal surface roughness. RESULTS: For the categories of anatomic form, marginal adaptation, surface quality, and temperature sensitivity, there were no significant differences between bonded and non-bonded amalgam restorations (chi-square analysis, p > 0.05). Three non-bonded restorations were lost at 4, 7, and 24 months from preparations with no deliberate retention. CONCLUSION: After two years' clinical service, there were no failures among the amalgam restorations adhesively bonded using ED Primer and Panavia 21 TC, but three non-bonded restorations failed due to lack of retention. For traditional preparations, adhesively bonded amalgams of the type investigated perform as well as non-bonded amalgams over two years' clinical service.

Bicuspid↗
PubMed1999

A three-year evaluation of restorations placed with a smear-layer-mediated dentin bonding agent in non-carious cervical lesions.

PURPOSE: To evaluate the handling characteristics, clinical behavior, and effectiveness of Coltene ART Bond/Brilliant restorations in mixed Class V preparations in maxillary premolar and canine teeth of adult patients over a three-year period. MATERIALS AND METHODS: Single-center, uncontrolled, clinical evaluation of 50 restorations in 26 patients extending over 36 months. RESULTS: At three years, 34 restorations, or 68% of those originally placed, in 20 patients were available for review. One of the 34 restorations had been lost 15 months after placement. In terms of marginal integrity and staining, anatomic form, surface texture and staining, and postoperative sensitivity, over 90% of the restorations reviewed at three years were rated alpha. Following difficulties in obtaining excellent color match in relation to 14 (28%) of the restorations at the time of placement, only 44% of the restorations were rated alpha at three years. CONCLUSION: It was concluded that with the possible exception of excellent color match, ART Bond/Brilliant restorations may be found to perform favorably in mixed Class V lesions in selected adult patients over a period of at least three years. The findings indicate that resin composite restorations placed with a smear-layer mediated dentin bonding agent may be found to have a favorable clinical outcome in non-carious cervical lesions.

Adult↗
PubMed1998

A milled ceramic inlay/onlay system: a report from a series of cases.

The aims of this study were to assess the handling properties of restorations produced by a milled ceramic system (Celay) and to evaluate by direct clinical means some of the characteristics of Celay restorations following placement and after one year of clinical service.

Adolescent↗
PubMed1998

Preparations for porcelain laminate veneers in general dental practice.

OBJECTIVE: To investigate variations in preparations for porcelain laminate veneers (PLVs) in general dental practice. DESIGN: Laboratory-based retrospective analysis of dies for PLVs. SETTING: General dental practice in England and Wales (1994). METHODS: A sample (95 cases) of laboratory models from general dental practice featuring preparations for PLVs was randomly selected from a full service commercial dental laboratory. Aspects of the preparations were quantified and compared with accepted preparation criteria distilled from a review of the literature. RESULTS: The teeth found to be most frequently prepared for PLVs were maxillary incisors (48%). The majority of cases investigated were for one veneer only (56%). The margins of the preparations were variably positioned with more than half of the preparations (55%) having no clear margin. In accordance with current guidelines the incisal edge tended to have been reduced during preparation (47%). In contrast, most teeth were underprepared with an average depth of preparation of 0.16 mm (SD 0.60 mm, 95% CI-0.1, 0.42). CONCLUSIONS: There was little evidence that established guidelines for the preparation of teeth for PLVs had been applied in full.

Dental Porcelain↗
PubMed1998

Ambient light working times of visible light-cured restorative materials. Does the ISO standard reflect clinical reality?

OBJECTIVES: The aim of this study was to determine whether a custom built light box could reliably reproduce clinical conditions and whether the current ISO standard test for the working time of visible light cured (VLC) materials (ISO. Dental Resin-based Restorative Materials. ISO:4049, 1991) reflected clinical reality. METHOD: The ISO test requires a VLC material to remain homogenous after exposure to an 8 kLux light source for 60 s. The relationship between the intensity of ambient lighting and the working times of visible light-cured (VLC) restorative materials was investigated by exposing 23 different VLC composite resin materials to a range of light intensities and measuring the working time in seconds: (a) under clinical operating conditions; (b) in a custom light box at 24 kLux; and (c) at 8 kLux in the light box. Working times were determined by placing 0.06 g samples between two glass plates and gently rotating until clefts or voids appeared. RESULTS: Clinical lighting conditions (24 kLux) gave a mean working time of 54 s (s.d. 14 s). In the light box at 24 kLux the mean working time was 54 s (s.d. 11 s). At 8 kLux (under otherwise identical conditions) the mean working time was 162 s (s.d. 49 s). SIGNIFICANCE: A 24 kLux illuminance in the laboratory gives an optimal correspondence to operative lighting conditions. This is three times the lighting level required for ISO purposes, and gives more realistic working times.

Analysis of Variance↗
PubMed1998

Methyl bromide: 1-year dietary study in dogs.

Average human exposure resulting from consumption of methyl 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 low-, 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.

Animal Feed↗
PubMed1998

Dental practice and the environment.

This paper summarises issues pertaining to the environmental effects of clinical practice. Using examples of environmental awareness, the concept of environmental auditing is introduced by way of a pointer to actions to limit the environmental impact of dentistry. It is concluded that environmental management and auditing would be advantageous to dentistry.

Dental Waste↗
PubMed1998

Teaching Class I and Class II direct composite restorations: results of a survey of dental schools.

The authors surveyed 54 North American dental schools about their teaching programs for posterior composite restorations. Marked variations were noted in the time spent teaching the use of these restorations, their indications and contraindications, and the techniques used for preparing and inserting the restorations. Although the time devoted to teaching placement of posterior composite restorations has increased during the last 10 to 12 years, most recent dental school graduates have minimal clinical experience with Class I and Class II composite restoration.

Bicuspid↗
PubMed1998

Single-use, disposable, presterilized light-activation probe: the future?

OBJECTIVE: The purpose of this study was to compare a single-use, disposable, presterilized light activation probe with an equivalent autoclavable probe. Light output, heat generation, and depth of cure were investigated. METHOD AND MATERIALS: Ten disposable and two reusable probe tips were tested. Three maximum light output readings for each tip were recorded with a radiometer. Heat generation at the probe tip was recorded, at 30-second intervals over a five-minute period, with a thermocouple probe placed under a 3-mm-thick glass slide. After light-activated "compomer" was placed in a sectional two-piece stainless steel mold and cured, depth of cure was evaluated using the scrape technique. RESULTS: With respect to light output and depth of cure, there were no statistically significant differences between probe types, but the disposable probe generated significantly less heat. CONCLUSION: The disposable probe performed clinically as well as an autoclavable counterpart with respect to light output, heat generation, and depth of cure.

Dental Instruments↗
PubMed1998

A survey of the attitudes of members of the European Prosthodontic Association towards the shortened dental arch concept.

A survey of members of the European Prosthodontic Association was undertaken to assess their attitudes to the shortened dental arch concept, and to evaluate their experience with the approach. Data were collected using questionnaires. From an overall response of 42%, 96% of respondents agreed that the approach was acceptable in clinical practice. Almost all respondents had applied the shortened dental arch concept with 72% of respondents having treated less than 50 patients in this way over the previous 5 years. In terms of comfort and function, treatment outcome was satisfactory. However, 42% of respondents indicated that prosthetic extension of shortened dental arches was occasionally required.

Attitude of Health Personnel↗