Biomedical subjects

N H Wilson

Publications and source records attributed to N H Wilson.

At least 19 recordsLinked to original sources

PubMed2001

The use and maintenance of visible light activating units in general practice.

AIM: The present study to investigate the use, care and maintenance of light units in everyday clinical practice was undertaken to complement light unit emission surveys, with a view to developing a protocol for light unit use and care in everyday clinical practice. METHOD: The investigative work comprised a survey of selected practices in the Blackburn area with follow-up practice visits to examine light units in situ, and to glean additional information in respect of light unit use and care in the practice environment. RESULTS: Completed questionnaires were returned by 54 of 77 selected practices--a 70% response, including information in relation to 164 light units. Subsequently, 100 (61%) of these light units were examined in 42 practices according to a standardised protocol. The use and care of the light units included in the study was found to be very variable. In addition to finding that 28 (28%) had inadequate light output (<300 mW/cm2), many of the light units were found to be damaged or repaired (47, 47%). Thirty five (35%) of the light units inspected were found to have varying amounts of material adherent to the light guide exit portal. CONCLUSION: It is concluded that practitioners should address practical aspects of their increasing reliance on light units, and to this end, guidance is offered on visible light curing and the care and maintenance of light units.

Dental Equipment↗

PubMed2001

Conference report. Direct adhesive materials: current perceptions and evidence--future solutions.

This paper reports the proceedings, including the consensus views of an Australasian expert group convened to consider current perceptions, evidence and future solutions in the field of direct adhesive materials. This group, in anticipating a trend to preservative dentistry, formed the view that caries risk assessment should increasingly influence the selection of restorative materials. In low caries risk patients, aesthetic demands typically favour the use of resin-based composites. Interactive (biomimetic) materials based on glass-ionomer chemistry have particular application in high caries risk patients. Teaching in dental schools, continuing education programmes and research, both in the laboratory and in the clinical environment should be more attuned to the ever-increasing use of tooth-coloured restorative materials in everyday clinical practice. Linked to this trend are changes in patient--dentist relationships, whereby patients should be encouraged to become more involved in treatment decision-making. Expert group meetings are suggested to be of value in addressing some of the shortfall between the need for good evidence and the relentless challenge of the introduction of new products and concepts in the field of direct adhesive materials.

Child↗

PubMed2001

Influence of patient factors on age of restorations at failure and reasons for their placement and replacement.

OBJECTIVE: This study examined the reasons given by a selected group of dental practitioners for placement and replacement of restorations and correlated the data provided with patient factors, such as patients' age and gender, caries risk, occlusal function and oral hygiene, with restoration longevity. METHOD: A group of general dental practitioners (GDPs) were recruited to take part in the study. Each participant was asked to record the reason for placement or replacement of restorations from a list of potential reasons. The age and Class of the restoration being replaced was also recorded, as also was the material being used and the material being replaced. RESULTS: Details of reason for placement/replacement was received on 3196 restorations from 32 GDPs. Of the restorations placed, 54% were amalgam, 32% composite, 8% compomer and 7% glass ionomer. The reasons for placement/replacement of the restorations were principally primary caries (28%), secondary caries (29%), margin fracture (10%), tooth fracture (7%), and non-carious defects (6%). Overall, the mean age of restorations at failure was 7.1 years. Of the patients who received glass ionomer restorations, 29% were rated as having poor oral hygiene, compared with 18% of the patients who received amalgam restorations, 18% of the patients who received composite restorations and 23% of the patients who received compomer restorations. Of the patients who received glass ionomer restorations, 35% were rated as having high caries susceptibility, compared with 27% of those receiving amalgam restorations, 21% of those receiving composite restorations and 30% of those receiving compomer restorations. CONCLUSION: Primary caries was the principal reason for initial restorations. Secondary caries was the most prevalent reason for replacement of restorations. The results also indicate a selective application of different materials for different patients.

Adolescent↗

PubMed2001

Root canal systems of the mandibular and maxillary first permanent molar teeth of south Asian Pakistanis.

AIM: The purpose of the present ex vivo study was to investigate variations in the root canal systems of mandibular and maxillary first permanent molar teeth of South Asian Pakistanis. METHODOLOGY: The root canal systems of a sample of 30 mandibular and 30 maxillary first permanent molar teeth extracted from South Asian Pakistanis were studied using a clearing technique. RESULTS: The mesial roots of the mandibular molar teeth typically presented with two canals (97%) of type II, IV or VI configuration. The distal roots of these teeth presented with a single canal (50%) of type I or V configuration or with two canals (50%) of type II, IV or VI. The prevalence of four root canals in two-rooted mandibular first permanent molar teeth was 47%. In maxillary molar teeth the mesial roots with a single canal (47%) were type I or type V; those with two canals (53%) were type II, IV or type VI. The distal and palatal roots that presented as a single canal (100%) were type I or type V configuration. The prevalence of four root canals in three-rooted maxillary first permanent molar teeth was 53%. CONCLUSION: It is concluded that four root canals in mandibular and maxillary first permanent molar teeth of South Asian Pakistanis is a common occurrence. The distribution of the different configurations of root canal systems in this population differed from that in Caucasian groups, suggesting that variations in root canal systems may be attributed to racial divergence.

Carbon↗

PubMed2001

How to obtain uniformity of occlusal detail.

At a recent Primary Dental Care Editorial Board meeting it was suggested that a series of short articles providing practical advice on clinical procedures might well be appreciated by our readers. This, then, is an invitation to our readers to submit material of this type, for publication. The text may be kept brief by the use of illustrations. The following example is the type of communication that we have in mind, but any information of a practical nature about the use of dental products would be carefully considered. We are grateful to the publishers of Fenestra (3M Dental Products) and the authors for permission to republish this piece first published in 1999.

Dental Impression Materials↗

PubMed2001

An overview of reasons for the placement and replacement of restorations.

AIM: Surveys on reasons for the placement and replacement of restorations have been conducted in various countries. The purpose of this paper is to bring together and review the data of 10 such surveys with similar methodology. METHOD: The studies reviewed are all based on the protocol described by Mjör in 1981. RESULTS: The surveys reviewed provide data on the reasons for the placement and replacement of a total of 32,777 restorations. Notwithstanding differences between countries, different groups of practitioners and minor variations in methodology, the data included in the selected surveys indicate that everyday clinical practice in Scandinavia, UK and USA during the 1980s and 1990s has involved more replacement than initial restorations, with the ratio of initial to replacement restorations ranging from 1:1.1 to 1:2.4 for amalgam and 1:1.1 to 1:3.8 for composite materials. Primary caries has been consistently found to be the principal reason for the provision of initial restorations of amalgam and composite. The principal reason for the replacement of restorations of amalgam and composite has remained secondary caries as diagnosed clinically. Material failures (marginal degradation, discoloration, bulk fracture and loss of anatomic form) accounted for the replacement of more restorations of composite than amalgam. Recent surveys have reported secondary caries as the principal cause of failure of restorations of glass-ionomer cements and related materials. CONCLUSIONS: The clinical diagnoses of caries may continue to be found to account for the placement and replacement of most intracoronal restorations. Surveys of the type reviewed provide valuable insight into patterns of provision of dental care and highlight research priorities in relation to direct restorations.

Composite Resins↗

PubMed2001

Marginal adaptation of amalgam and resin composite restorations in Class II conservative preparations.

OBJECTIVE: The purpose of this study was to compare and contrast the performance, in terms of marginal adaptation, of a non-gamma-2 amalgam alloy with a compact-filled light-cured composite in the restoration of Class II preparations of conservative design. METHOD AND MATERIALS: Fifty recently extracted teeth were selected for the study. The teeth were restored with either a non-gamma-2 amalgam alloy, Dispersalloy, or a compact-filled resin composite, Z100, using standard techniques. The marginal adaptation of the restorative materials to the proximal surface outline form of each preparation was assessed at magnification x30. RESULTS: Highly significant differences were demonstrated in the mean percentages of perfect margins in all 3 segments of the proximal boxes of the restorations with the resin composite performing significantly better than the amalgam. The percentages of marginal fissuring were significantly higher in the amalgam restorations, except at the cervical margin, where the incidence of fissuring was almost the same for the amalgam and resin composite restorations. The resin composite restorations had significantly fewer underfilled margins than the amalgam restorations. CONCLUSION: In the conservative Class II preparations, the amalgam restorations were of poor quality with respect to marginal adaptation, compared with the resin composite restorations. It is suggested that the use of amalgam as a control in a clinical evaluation of resin composite restorations in conservative preparations cannot be justified, because it is apparently not possible to compare restorations of equivalent initial quality.

Bicuspid↗

PubMed2001

Wastage of a silicone impression material in a general practice setting: a comparison between hand and automixing methods.

A practice-based, randomised, controlled trial has been undertaken to investigate the wastage of impression material when recording full arch one-stage, polyvinyl siloxane impressions using four techniques: putty and automix light viscosity material, putty and automix regular viscosity material, putty and tubed light viscosity material, and putty and tubed regular viscosity material. A total of 100 maxillary impressions, comprising 25 recorded using each of the four techniques, were obtained according to a predetermined scheme for randomisation. All material wasted in dispensing, mixing and applying each impression was determined by repeated weighing. Statistical comparisons of the mean weights of material wasted for each type of impression revealed that significantly (P < 0.01) less wastage occurred with the automix techniques. It is concluded that automix impression techniques may, in more extensive studies, be found to be more cost effective than tubed impression material techniques when recording impressions of the type investigated.

Cost-Benefit Analysis↗

PubMed2000

Tooth preparation techniques for porcelain laminate veneers.

OBJECTIVE: The purpose of this study was to determine the effect that two guides to tooth preparation had on an operator's ability to appropriately and consistently prepare teeth for porcelain laminate veneers. STUDY DESIGN: In-vitro study. MATERIALS AND METHODS: Thirty typodont central incisor teeth were randomly allocated into three groups and a general dental practitioner was asked to prepare the teeth for porcelain laminate veneers. Group A were prepared freehand while Groups B and C were prepared with the assistance of a silicone index and depth preparation bur respectively. Images of the prepared teeth were used to calculate the mean labial depth of preparation and incisal reduction of teeth in each group. RESULTS: The mean labial reduction for Groups A, B and C was 0.37 mm (SD 0.13), 0.62 mm (SD 0.17) and 0.61 mm (SD 0.15) and the mean incisal reduction for Groups A, B and C was 1.0 mm (SD 0.28), 1.0 mm (SD 0.38) and 1.03 mm (SD 0.26) respectively. CONCLUSION: It is suggested that consideration be given to the use of a silicone index or depth gauge bur when teeth are prepared for porcelain laminate veneers.

Dental Instruments↗

PubMed2000

Influence of the isolation method on the 10-year clinical behaviour of posterior resin composite restorations.

The aims of this prospective randomised clinical study were to clinically evaluate a radiopaque, highly filled, hybrid, light-activated resin-based composite for posterior teeth (Occlusin, ICI Dental, Macclesfield, UK and GC Dental, Tokyo, Japan) and compare the performance of restorations placed using rubber dam or cotton roll isolation. One clinician placed 100 (42 Class I and 58 Class II) restorations of the material under investigation. The isolation mode for each restoration was determined randomly: 52 preparations were protected from contamination with cotton rolls and aspiration, and 48 preparations were isolated under rubber dam. At baseline and periodically thereafter (0.5, 1, 2, 3, 4, 5, 6, and 10 years), each composite was evaluated by two practitioners using a modified (USPHS) rating system. After 10 years, 37 restorations were reviewed. The results showed satisfactory clinical performance with and without rubber dam after 10 years. A concern was the number of failures at 10 years due to unsatisfactory proximal contact. The evaluations for the surviving restorations were acceptable but with a large reduction in the percentage with ideal occlusal and proximal anatomy. The 10-year comparison of isolation modes showed no statistically significant differences (Kruskal-Wallis test) for each of the evaluation criteria. Furthermore, survival analysis showed no significant difference between the groups (Mantel-Haenszel method). It was concluded that the 10-year clinical behaviour of the restorations of a posterior composite placed under well-controlled, effective isolation with cotton rolls and aspiration, was not significantly different from the behaviour of restorations placed using rubber dam isolation.

Analysis of Variance↗

PubMed2000

Resistance of two dentin-bonding agents and a dentin densensitizer to acid erosion in vitro.

OBJECTIVES: To determine the resistance of two dentin-bonding agents (DBAs) and a dentin desensitizer to simulated dental erosion. METHODS: Twenty teeth in each of three groups of selected premolars, with exposed cervical dentin, were treated with one of three dentin surface treatment systems: Gluma Desensitizer (Heraeus Kulzer (UK) Ltd), One Coat Bond (Whaledent (UK) Ltd), and Optibond FL (Kerr (UK) Ltd) and exposed to water (control) and an erosive challenge (Coca Cola) for 14 days. Sequential tracings of the specimens were taken, superimposed and the mean reduction in densensitizer or DBA thickness and or tooth loss determined. RESULTS: A mean loss of 77 microns (s.d. 14.6 microns) of tooth tissue over the untreated sites following 14 days exposure to Coca Cola was observed. The application of DBAs, as opposed to Gluma Desensistizer alone, over exposed dentin surfaces afforded substantial protection against erosion by Coca Cola over the period of study. The mean change in vertical profile of teeth treated with a DBA was 20 microns (s.d. 14.7 microns), almost four times less than that seen over untreated sites. SIGNIFICANCE: With the exception of Gluma Desensitizer, which was lost completely, One Coat Bond and Optibond FL demonstrated levels of acid dissolution resistance, which would be of potential value clinically.

Analysis of Variance↗

PubMed2000

Clinical crown length changes from age 12-19 years: a longitudinal study.

OBJECTIVE: The objective of this study was to investigate the relationship between age, gender and clinical crown length using a longitudinal study design. METHOD: Four hundred and fifty-six sets of study models initially obtained for a large prospective longitudinal cohort study of orthodontic needs were examined. Each set of models corresponded to subjects at three different ages: 11-12, 14-15 and 18-19years old. The clinical crown height of the maxillary right central incisor (11), maxillary right canine (13), maxillary left lateral incisor (22) and mandibular left central incisor (31) was measured from gingival crest to the incisal edge using digital calipers. RESULTS: Analysis revealed a significant (p<0.0001) age effect on crown length for all four teeth investigated. A significant gender effect was found in relation to the maxillary right canine, maxillary right central incisor and maxillary left lateral incisor. Pairwise comparisons of the means for each age group for the maxillary right canine, maxillary right central incisor and maxillary left lateral incisor revealed significant (p<0. 0001) increases in clinical crown length between each assessment period. CONCLUSION: The findings of the present study indicate that, the process of passive eruption, resulting in increased clinical crown length appears to continue throughout the teenage years. This finding is considered to be of importance to the clinician making treatment decisions for teenagers and young adults requiring treatment in the anterior segments of the mouth.

Adolescent↗

PubMed2000

Endodontics in the adult patient: the role of antibiotics.

OBJECTIVES: The aim of this study was to review the published work on the indications and efficacy for antibiotics in endodontic therapy. DATA SOURCES: Published works in the medical and dental literature. STUDY SELECTION: Evaluation of published clinical trials in endodontic and other pertinent literature. CONCLUSIONS: Antibiotics are not routinely indicated in the practice of endodontics. Therapeutic antibiotics may be required as an adjunct to operative treatment when there is pyrexia and/or gross local swelling; they are only rarely indicated in the absence of operative intervention. Prophylactic antibiotics may be required for certain patients who are susceptible to serious infective sequaelae.

Adult↗

PubMed2000

The teaching of Class I and Class II direct composite restorations in European dental schools.

OBJECTIVES: The purpose of this descriptive study was to provide updated data on the teaching of Class I and Class II direct composite restorations in Europe as part of a survey of this aspect of the primary dental curriculum in Europe and North America. METHODS: Data on the teaching of posterior composite restorations and related matters were collected by means of a postal questionnaire sent to 185 dental schools known to exist in Europe. Non-respondents were sent a second questionnaire after two months. Further information pertaining to student requirements was sought after six months from all respondents. RESULTS: The response ranged from 92% for dental schools in Scandinavia to 40% from dental schools in Southern Europe with an overall response of 56%. All but four of the 104 participating schools were found to teach the use of composites in Class I and Class II, two-surface situations in at least premolar teeth. Contraindications and techniques taught for posterior composites varied within and between the country groupings of Northern and Central Europe. Scandinavia, Southern Europe and Eastern Europe. However, certain consensus views were identified. The experience of adverse biological reactions to the use of resin-based restoratives in European dental schools was found to be limited. CONCLUSIONS: Notwithstanding the variation in the response from the four geographic regions investigated and the relatively low overall response to the questionnaire, it is concluded that the data reported indicates that most dental schools in Europe teach the use of composites in selected Class I and Class II situations. However, considerable variation exists both within and between the regions investigated in relation to this teaching. Further research and consensus conferences should be planned to reduce variability across Europe in relation to the contraindications and techniques taught for posterior composites.

Composite Resins↗

PubMed2000

Students' perceptions of seminar and lecture-based teaching in restorative dentistry.

In an era of self-directed learning, it is important to seek the views of dental students regarding their learning experience. Using an anonymous questionnaire, clinical dental students' perceptions of seminar and lecture-based teaching in restorative dentistry were sought. 116 of 136 questionnaires circulated were returned for analysis giving a response rate of 85%. Clinical seminars as opposed to lectures were, in the opinion of the students, a more effective way of learning, more relevant to self-development and more interactive. Seminar-based learning was considered to be more amenable to self-direction than formal didactic lectures. It is concluded that the students included in this study were found to prefer seminar-based learning opportunities as opposed to more traditional styles of learning, specifically, didactic lectures.

Attitude↗

PubMed2000

Reasons for placement and replacement of restorations in student clinics in Manchester and Athens.

Data on reasons for the placement and replacement of restorations provide insight into patterns of clinical practice. This study investigated reasons for the provision of restorations in student clinics at the Universities of Manchester and Athens. Using the methods first described by Mjör, data were collected in relation to all initial and replacement restorations placed in adult patients in the main teaching clinics in the 2 schools over a 3-month period. The principal reason for intervention was recorded, according to approved treatment plans. Data were collected on 2620 restorations, 1431 (55%) of which were placed in Manchester. Primary caries was the main reason for the placement of initial restorations: 82% in Athens and 48% in Manchester (p<0.001). The principal reason for restoration replacement was secondary caries, accounting for 54% in Manchester and 33% in Athens (p<0.001). Other differences between the schools, included the ratio of initial placement to replacement restorations (Manchester 1:1.1; Athens 1:0.6: p<0.01) and significantly more 2-surface class II restorations having been placed in Manchester (p<0.001). Class III and IV restorations predominated in Athens. It is concluded, despite the acknowledged limitations of the methods employed, that the patterns of placement and replacement of restorations and the use of materials differ between the dental schools of Manchester and Athens. The differences are considered to relate more to local patterns of dental disease and patient selection for student clinics than to any differences in teaching philosophy. Subsequent studies of the type reported, despite acknowledged limitations would provide insight into the impact on patient care of the teaching of new materials, techniques and treatment philosophies.

Adolescent↗

PubMed2000

Removal of porcelain veneers aided by a fluorescing luting cement.

PURPOSE: Porcelain veneers are a safe and effective treatment modality for selected teeth that have poor esthetics. However, removal of porcelain veneers that have failed may be time-consuming and involve considerable removal of sound tooth structure adjacent to the veneer. The aim of this study was to evaluate a novel method of porcelain laminate veneer removal by incorporating a fluorescent dye into the luting cement that allows the practitioner to visualize the cement on the tooth and remove the veneer without causing residual damage to the adjacent tooth substance. MATERIALS AND METHODS: Porcelain veneers were luted on extracted teeth with a luting cement modified with a fluorescing agent. Faculty teaching staff and final year dental undergraduates were asked to remove the veneers with the aid of a curing light to render the luting cement visible by fluorescing. They were then asked to compare the removal of comparable veneers without this visual aid and to complete a standard questionnaire. The depth of cure of the conventional and modified cements was measured using a penetrometer. RESULTS: Results of the questionnaire indicated that the operators found removing the veneer cemented with the modified (fluorescing) cement considerably easier than removing the veneer cemented with the conventional cement. Microscopy indicated that more damage was caused to the underlying tooth during removal of conventionally cemented veneers. The incorporation of the dye into the cement reduced the depth of cure from 4.238 mm (SD = 0.025) to 3.761 mm (SD = 0.096).

Dental Debonding↗

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↗