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Biomedical subjects

D W Bartlett

Publications and source records attributed to D W Bartlett.

At least 19 recordsLinked to original sources
PubMed2006

Downloadable computer models for renal replacement therapy.

Mathematical models can predict solute clearances and solute concentrations during renal replacement therapy. At present, however, most nephrologists cannot use these models because they require mathematical software. In this report, we describe models of solute transport by convection and diffusion adapted to run on the commonly available software program Excel for Macintosh computers and PCs running Windows. Two programs have been created that can be downloaded from http://www.stanford.edu/~twmeyer/ or http://dev.satellitehealth.com/research/journal.asp. The first, called 'Dr Addis Clearance Calculator', calculates clearance values from inputs including the blood flow Q(b), the hematocrit, the ultrafiltration rate Q(f), the dialysate flow rate Q(d), the reflection coefficient sigma and the mass transfer area coefficient K(o)A for the solute of interest, and the free fraction f if the solute is protein bound. Solute concentration profiles along the length of the artificial kidney are displayed graphically. The second program, called 'Dr Coplon Dialysis Simulator', calculates plasma solute concentrations from the clearance values obtained by the first program and from additional input values including the number of treatments per week, the duration of the treatments, and the solute's production rate and volumes of distribution. The program calculates the time-averaged solute concentration and provides a graphic display of the solute concentration profile through a week-long interval.

Animals↗
PubMed2006

A critical review of non-carious cervical (wear) lesions and the role of abfraction, erosion, and abrasion.

The terms 'abfraction' and 'abrasion' describe the cause of lesions found along the cervical margins of teeth. Erosion, abrasion, and attrition have all been associated with their formation. Early research suggested that the cause of the V-shaped lesion was excessive horizontal toothbrushing. Abfraction is another possible etiology and involves occlusal stress, producing cervical cracks that predispose the surface to erosion and abrasion. This article critically reviews the literature on abrasion, erosion, and abrasion, and abfraction. The references were obtained by a MEDLINE search in March, 2005, and from this, hand searches were undertaken. From the literature, there is little evidence, apart from laboratory studies, to indicate that abfraction exists other than as a hypothetical component of cervical wear.

Dental Enamel↗
PubMed2005

An audit of study casts used to monitor tooth wear in general practice.

OBJECTIVE: To assess the outcome of compliance of advice sent to patients and dentists about monitoring tooth wear in general practice. METHOD: Postal questionnaires were sent to 70 patients and their dentists requesting information on the outcome of letters of advice sent to general dental practitioners regarding monitoring tooth wear with study casts. They also requested information about the reasons for the patients' referral, the outcome of treatment and whether study models had been taken. RESULTS: Replies were received from 60 dentists (87%) and 53 patients (75%). Of these, 16 patients and 16 dentists had moved from their recorded address. Study casts were reported as having been taken by 23 dentists (38%) and reported by 18 patients (34%). The most common reason for referral was advice about monitoring the wear and the appearance of their teeth. CONCLUSIONS: The compliance of the patients and dentists in monitoring tooth wear by using study casts in general practice was not successful. It raises issues regarding the value of consultant advice letters to this common clinical problem.

Adult↗
PubMed2004

The surface effects of erosion and abrasion on dentine with and without a protective layer.

OBJECTIVE: The aim of this in situ study was to investigate with four imaging modalities whether covering dentine with adhesive resins could protect against erosion from acids. The objectives were to observe and quantify the effects of acids and the soft tissues, especially the tongue, on dentine and the bonding agents using four assessment techniques: qualitative assessment with SEM, surface roughness and thickness of resin with the TSM and volume loss with the laser profilometer. DESIGN: An in situ investigation using extracted dentine sections embedded in splints held on the palate of 10 volunteers. The dentine sections were protected by two resins and subjected to a tooth wear regime. RESULTS: Both Seal and Protect and Opitbond Solo protected the tooth surfaces from a tooth wear regime. There were no statistical differences between the control surfaces and those protected with dentine bonding agents for resin thickness, roughness and profilometry. The appearance of the slabs under both confocal and SEM showed that the material remained in place despite a vigorous wear regime and therefore protected the tooth surface. CONCLUSIONS: For patients with uncontrolled erosion or tooth wear, applying a dentine bonding agent to exposed dentine is a practical option to prevent further damage.

Adult↗
PubMed2003

Retrospective long term monitoring of tooth wear using study models.

OBJECTIVE: Tooth wear is recognised as a common feature of European dentitions. However, little is known about its progression in susceptible patients. The aim of this study was to assess the degree and progression of tooth wear in patients by examining study casts taken of their teeth on two separate occasions. DESIGN: Over 500 sets of study casts taken during an 18-year period from patients referred for a variety of restorative procedures, were examined at Guy's Dental Hospital. Of these, 34 cases were found to have consecutive models taken at two time intervals and these were used to assess the progression of tooth wear. Study models from 19 females and 16 males, with an average age of 26 years (range 18-60) at the time of their first presentation and were all examined by a single operator. The Smith and Knight tooth wear index was used to assess the degree of tooth wear at presentation and then at another time which was a median of 26 months (interquartile range 14 - 50 months) later. RESULTS: The most common initial TWI score per surface was 1, with 54% of surfaces affected at the first assessment and 57% at the second. Score 2 was less common (14% at both assessments) and the scores for 3 and 4 combined were relatively uncommon with 5% of surfaces effected. Minimal progression of tooth wear was observed on study casts with only 7.3% of surfaces involved. CONCLUSION: In this sample, tooth wear was a slow, minimally progressive process.

Adolescent↗
PubMed2001

Experiences and perceptions of vocational training reported by the 1999 cohort of vocational dental practitioners and their trainers in England and Wales.

OBJECTIVE: To assess the self-reported confidence of vocational dental practitioners (VDPs) in clinical procedures together with vocational trainers' perceptions of the VDPs confidence in the same procedures, immediately after qualification and towards the end of the vocational training year. DESIGN: A questionnaire-based cohort study. SETTING: A general practice study carried out in 1999. SUBJECTS: Vocational Dental Practitioners and vocational trainers in England and Wales. METHOD: VDPs and trainers were asked on a single occasion to grade the clinical confidence of the VDP at the beginning and near the end of vocational training as high, satisfactory or low. RESULTS: Questionnaires were sent to 531 VDPs and 555 trainers; 82 per cent of VDPs and trainers responded. Approximately half the VDPs were male and 57 per cent were white, whilst 89 per cent of trainers were male and 81 per cent white. A large proportion of both VDPs and trainers reported low confidence in orthodontics, molar endodontics and surgical extractions at the start of the training year. Towards the end of training, both groups reported improved confidence levels in most clinical procedures. However, a higher proportion of trainers reported low confidence than their VDPs in most clinical procedures at both time points (p<0.001). VDPs appeared to gain most from experience and training in administration/management and interpersonal skills. CONCLUSION: Vocational training appears to satisfy its aim to enhance clinical and administrative confidence.

Clinical Competence↗
PubMed2001

Mesotrione: a new selective herbicide for use in maize.

Mesotrione is a new herbicide being developed for the selective pre- and post-emergence control of a wide range of broad-leaved and grass weeds in maize (Zea mays). It is a member of the benzoylcyclohexane-1,3-dione family of herbicides, which are chemically derived from a natural phytotoxin obtained from the Californian bottlebrush plant, Callistemon citrinus. The compound acts by competitive inhibition of the enzyme 4-hydroxyphenylpyruvate dioxygenase (HPPD), a component of the biochemical pathway that converts tyrosine to plastoquinone and alpha-tocopherol. Mesotrione is an extremely potent inhibitor of HPPD from Arabidopsis thaliana, with a Ki value of c 6-18 pM. It is rapidly taken up by weed species following foliar application, and is distributed within the plants by both acropetal and basipetal movement. Maize is tolerant to mesotrione as a consequence of selective metabolism by the crop plant. Slower uptake of mesotrione, relative to susceptible weed species, may also contribute to its utility as a selective herbicide for use in maize.

4-Hydroxyphenylpyruvate Dioxygenase↗
PubMed2001

The measurement and prevention of erosion and abrasion.

OBJECTIVES: To develop a reproducible method to measure tooth wear and assess the protection given by dentine bonding agents in an erosive/abrasive wear regime. METHODS: Seal and Protect (Dentsply, UK) and Optibond Solo (Kerr, UK) were each applied to 20 extracted teeth and subjected to 3000 cycles in a reciprocating erosion/abrasion wear machine. A further 20 teeth, without protection, were subjected to the same wear regime and were either brushed in water or immersed in acid. Impressions were taken by a standardised technique and were scanned with a non-contacting laser profilometer. The amount of erosion was measured at the same co-ordinates before and after erosion using 2mm diameter metal discs as reference points. RESULTS: The amount of wear on Seal and Protect had a mean 24.8 microm (SD 57.4 microm) and for Solo it was 1.4 microm (24.5 microm), and this difference was statistically significant (p=0.02). There was no statistically significant difference in the wear measured on the teeth brushed in water or immersed in acid. The wear measured on the unprotected teeth was 243 microm (SD 120 microm) and was statistically significantly different to the protected surfaces (p=0.001). CONCLUSION: Both Seal and Protect and Solo protected the teeth in this wear regime and the technique could be used clinically for patients with uncontrolled dental erosion.

Analysis of Variance↗
PubMed2001

Comparison of the erosive potential of gastric juice and a carbonated drink in vitro.

The aim of this study was to compare the erosive effect of gastric juice and a carbonated drink on enamel and dentine by measuring release of calcium from 30 hemisectioned teeth in vitro. In addition, the titrable acidity (mL of 0.05 M sodium hydroxide required to neutralize) and pH of the fluids was estimated. The mean pH of the seven gastric acid samples was 2.92 (range 1.2-6.78) and mean titratable acidity 0.68 mL (range 0.03-1.64). Both the pH and the titratable acidity of the gastric juice varied between patients all of whom suffered from symptoms of reflux disease. The carbonated drink had a pH of 2.45 and a titratable acidity of 0.29 mL. The median amount of calcium released by the gastric acids from enamel was 69.6 microg L-1 (interquartile range 5.4-144) and 62.4 microg L-1 (2.2-125.3) from dentine. The carbonated drink released 18.7 microg L-1 (13.4-23.4) and 18.6 microg L-1 (11.9-35.3), respectively. The differences in calcium release by gastric juice and the carbonated drink were statistically significant for both enamel (P < 0.005) and dentine (P < 0.01). It is concluded that gastric juice has a greater potential, per unit time, for erosion than a carbonated drink.

Calcium↗
PubMed2001

Bleaching discoloured teeth.

The bleaching of teeth has encountered some legislative problems over the past few years but it is now possible to use both vital and non-vital bleaching techniques in the UK. Hydrogen peroxide has a long history of use and would appear to be safe to use to change the appearance of discoloured teeth. It is conservative of tooth tissue and may delay the need for more invasive veneers and crowns. This article describes some of the methods of bleaching using hydrogen peroxide that are currently available.

Borates↗
PubMed2000

Oral pH and drinking habit during ingestion of a carbonated drink in a group of adolescents with dental erosion.

OBJECTIVES: To investigate the relationship between dental erosion, oral pH and drinking habit in a group of adolescents. METHODS: Oral pH was measured simultaneously at the surface of four teeth in 11 patients, aged 10-16 years, with erosion and in 10 controls subjects without erosion using antimony electrodes. Measurements were made before, during and after drinking 330 ml of a carbonated drink. The method and timing of drinking the beverage, reported dietary intake of acidic foods and flow rate and buffering capacity of saliva were recorded. RESULTS: The erosion patients reported drinking more carbonated drinks (p<0.01) and drinking directly from a can more frequently than the controls (p<0.05). They also drank twice as quickly (p<0.05). The pH at the buccal surface of a molar remained lower for longer in the erosion patients than in the patients without erosion (p<0.01), whilst the labial surface of the upper central incisor had a longer exposure to low pH in the controls subjects (p<0.05). CONCLUSION: The pattern of oral pH differed between subjects with and without erosion after drinking an acidic beverage. This may be related to observed differences in drinking habit, which could have influenced the pattern of erosion in these subjects.

Adolescent↗
PubMed2000

The role of the esophagus in dental erosion.

OBJECTIVE: The aim of this study was to measure lower esophageal sphincter pressure, sphincter length, and esophageal motility in patients with dental erosion and compare the results with measurements made in patients without gastroesophageal reflux or dental erosion. STUDY DESIGN: Lower esophageal sphincter length and esophageal motility were measured in 39 patients (age range, 15-74 years) with dental erosion through use of static esophageal pressure monitoring; the data were compared with those from 10 control subjects (age range, 26-46 years) with nonparametric statistical tests. RESULTS: Median lower esophageal sphincter pressure was 9 mmHg (range, 0-26 mmHg) in the patients with erosion and 9.5 mmHg (range, 0 -14 mmHg) in the controls; there was no statistically significant difference between the two subject groups. Similarly, there was no statistically significant difference in esophageal length between the subject groups. There was a statistically significant difference between the groups (P =.01) in the measurement of esophageal motility; the median value was 8% (range, 0% to 100%) in the patients with erosion and 0% (range, 0% to 18%) in the controls. CONCLUSIONS: It appears that esophageal motility in patients with dental erosion is more likely to be associated with low amplitude changes than with sphincter pressure alone. Poor esophageal motility may therefore be a risk factor in regurgitation erosion.

Adolescent↗
PubMed2000

A literature review of the techniques to measure tooth wear and erosion.

This paper reviews methods to measure tooth wear especially those more recently introduced as a result of improvements in technology. The review searched methods to measure tooth wear and dental erosion from large epidemiological investigations, in vitro and in vivo studies. There seems to be wide variation in techniques used to measure tooth wear and erosion. In vitro techniques may have little direct clinical relevance but can lead to new and more accurate clinical methods. In vivo studies have problems with reference points and accurate validation of the techniques. There is a need for a simple, reliable technique to quantify tooth wear due to erosion.

Diagnostic Imaging↗
PubMed1999

Dealing with sensitive teeth.

Dental pain is extremely common in the UK and can severely reduce the quality of life when it is associated with eating, drinking or speech. Patients often present complaining of a short, sharp, stabbing pain from hot or cold air, foods or drinks: while this may be caused by tooth decay, failing fillings or cracks in teeth, a major cause is sensitivity from exposed dentine. Treatment varies from dietary control, desensitising toothpastes to protection with dentine-bonding agents and glass ionomers. In extreme cases elective devitalisation is necessary.

Dentin Permeability↗
PubMed1999

The role of saliva in regurgitation erosion.

It has been suggested that salivary characteristics are important in the progression of erosion. The aim of this investigation was to measure salivary parameters in 22 patients with erosion, 10 with normal (non-pathological) levels of reflux (Group I) and 12 with previously diagnosed pathological levels of gastro-oesophageal reflux (Group II). A further 10 subjects without evidence of erosion and no history of reflux disease acted as controls (Group III). No statistically significant differences in salivary flow rate, buffering power or the concentrations of calcium, phosphorus and fluoride were detected. The results suggest that variation in the characteristics of unstimulated and stimulated saliva collected during waking hours do not have a major role in erosion.

Adult↗
PubMed1998

The prevalence of tooth wear in a cluster sample of adolescent schoolchildren and its relationship with potential explanatory factors.

OBJECTIVE: To assess the prevalence of tooth wear in adolescents and its relationship with diet, saliva and gastro-oesophageal reflux. DESIGN: Single centre cluster sample epidemiological study. SETTING: A school in London in the summer of 1996. SUBJECTS: 11-14-year-old schoolchildren. MAIN OUTCOME MEASURES: The Smith and Knight tooth wear index (TWI), salivary factors, diet and symptoms of gastro-oesophageal reflux were recorded for all subjects. RESULTS: Results were obtained from 210 subjects. One subject refused to provide a saliva sample and 11 subjects provided insufficient saliva for analysis of buffering power (n = 198). 57% (95% confidence intervals 50.3-63.7%) of subjects had tooth wear on more than ten teeth and a median 12% (interquartile range 6-18%, 95% confidence intervals 8-14%) of surfaces were affected. However, dentine involvement was rare. The median intake of carbonated drinks was 2 cans (interquartile range 1-3) a day. However, there was no correlation with TWI (r = -0.09, P = 0.19). There was no relationship between tooth wear index (TWI) and salivary flow rate (r = -0.02, P = 0.78) or buffering capacity (r = -0.02, P = 0.76). A trend was observed for those with a reported history of regurgitation (n = 27) to have a higher maxillary TWI (median 8, interquartile range 2-13) compared with those who did not (5, 2-9, P = 0.06). CONCLUSIONS: Tooth wear is common in adolescents and the relationship with dietary acid, salivary buffering and symptoms of gastro-oesophageal reflux is complex and requires further investigation.

Adolescent↗