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Biomedical subjects

K W Stephen

Publications and source records attributed to K W Stephen.

At least 55 records · Page 3Linked to original sources
PubMed1991

Prediction of caries increment in Scottish adolescents.

Salivary, clinical, and microbiological factors were compared with subsequent 2-yr caries increment in a group of 372 Scottish adolescents. The caries increment was significantly correlated with previous caries experience, salivary buffering capacity and counts of lactobacilli, mutans streptococci and candida. Veillonella levels and salivary flow rate were not correlated with caries increment. Significant improvements in the predictions were obtained when the results of more than one test were included using stepwise regression analysis. On an individual basis, using stepwise discriminant analysis, the caries increment group (low, medium, or high) was identified correctly in 49% of all subjects, but this was reduced to 45% if previous caries experience was excluded from the analysis.

Adolescent↗
PubMed1991

Comparison of the plaque microflora from natural and appliance-borne enamel surfaces.

Human enamel sections and slabs, mounted on a mandibular removable appliance, were worn by 5 adult subjects for a 1-week period. Plaque was allowed to accumulate on the in situ test sites and on the adjacent natural dentition. At the end of the experimental period, the plaque microflora associated with (1) the enamel sections, (2) the enamel slabs, and (3) the acrylic base of the appliance test site was compared with that obtained from lingual and interproximal areas of the lower molar teeth. In addition, the acid anion and pH profiles of plaque obtained from both the exogenous and natural tooth surfaces were also determined. Although some quantitative differences were found between the proportions of isolates obtained from the different enamel surfaces, qualitatively the microflora was very similar, and no significant differences were found in the plaque lactate/acetate ratios or pH measurements following a sucrose mouthrinse. Thus, human tooth specimens mounted on the intra-oral device produced a plaque ecosystem similar to that present on the adjacent natural dentition, suggesting that the model is suitable for studies on early plaque development and the microbiology of enamel demineralization.

Acrylic Resins↗
PubMed1991

Effect of mouthrinsing after toothbrushing with a fluoride dentifrice on human salivary fluoride levels.

In a recent clinical trial of sodium monofluorophosphate dentifrices, oral rinsing habits were found to influence dental caries. Thus an oral fluoride clearance study has been undertaken which was designed to test a possible mechanism for the observed effects. Eight subjects brushed with one of the trial dentifrices and then rinsed using 1 of 8 procedures of varying thoroughness. The salivary fluoride concentration measured 5 min after dentifrice application decreased significantly with increasing rinse volume, rinse duration, and rinse frequency (p less than 0.01, analysis of variance). The area under the clearance curve determined over a further 3 h was significantly higher (300%; p less than 0.01) following use of the least thorough rinsing procedure (5 ml x 2 s once) as compared with the corresponding area under the clearance curve following the most thorough procedure (20 ml x 10 s twice). These findings indicate that rinsing habits may play an important role in the oral retention of fluoride from dentifrices which may, in turn, affect their clinical efficacy.

Adult↗
PubMed1991

Incisor enamel mottling prevalence in child cohorts which had or had not taken fluoride supplements from 0-12 years of age.

Blind photographic assessments were made of the permanent incisors of 322 children who had participated in two successful fluoride drop/tablet hygienist-based preventive dentistry programmes. Two groups of four dental and two lay assessors unanimously scored 57% of dentitions as mottling-free. The dental observers unanimously scored 37 children (12%) with some symmetrical homologous tooth-type mottling, although only 13 decisions (4%) were scored "unacceptable easthetically". The lay assessors rated 77 children (24%) with mottling, 15% being easthetically displeasing. However, no significant mottling differences were noted between cohorts which had commenced oral fluoride supplementation at birth and those which either commenced as late as 7 years of age, or which had never taken any such supplementation. Thus other fluoride sources must have been responsible for the non-drop/tablet diffuse symmetrical mottling noted, the most likely being highly fluoridated dentifrices ingested by youngsters unable to control the volume dispensed and swallowed. Hence the evidence does not suggest that this proven caries-inhibiting F- drop/tablet regime dosage should be reduced. There is, however, a clear and continuing need for both the dental profession and the public to be made more aware of the problem of uncontrolled fluoride ingestion from other sources.

Age Factors↗
PubMed1990

The prevalence of clinically undetected occlusal dentine caries in Scottish adolescents.

During the third examination of a 3-year anti-caries dentifrice study, bitewing radiographs were read to detect occlusal, as well as approximal caries lesions in 2623 subjects aged 14-15 years. These analyses showed that 1.4% of 2107 upper molars and 7.2% of 2288 lower molars (P less than 0.001), previously scored as clinically 'sound', were carious at a radiographic Grade '3' score (dentinal involvement), and 0.2% had radiographic pulpal lesions. However, for teeth which had been deemed as having a 'suspicion' of caries clinically, but which a 0.6 mm blunted probe would not enter, 29.1% of lower molars had definite radiographic evidence of dentinal caries as compared to only 7.6% of upper molars (P less than 0.001), and a further 0.5% exhibited pulpal extension. In addition, 23.9% of lower premolars also showed dentinal involvement in this group. Overall, 12.1% of lower molars and 3.1% of upper molars showed definite radiographic evidence of occlusal caries in the absence of a firm clinical indication. Thus, the use of bitewing radiographs would appear to be a most helpful adjunct to clinical caries diagnosis, not only of approximal lesions, but also for the detection of early occlusal caries, in these days of generally available topical fluoride.

Adolescent↗
PubMed1990

Caries prevalence and microbiological and salivary caries activity tests in Scottish adolescents.

Salivary and microbiological caries activity tests were investigated on three occasions in a group of 372 Scottish adolescents. Counts of lactobacilli, mutans streptococci, and candida were consistently and significantly associated with caries prevalence, as either DS or DMFS score, and buffering capacity was consistently inversely related to DMFS score. However, veillonella counts and salivary flow rate were not correlated with caries prevalence. Significant improvements in the associations were obtained when the results of more than one test were included using stepwise regression analysis. On an individual basis, at most, stepwise discriminant analysis identified the DMFS group correctly in 49% of all subjects, and the DS group in 47%.

Adolescent↗
PubMed1990

Combined fluoride therapies. A 6-year double-blind school-based preventive dentistry study in Inverness, Scotland.

A 6-yr double-blind study was undertaken to compare the caries inhibiting-effectiveness of (a) 1 mgF- tablets (daily at school) plus fortnightly rinsing at school with 1000 ppmF-; (b) 1 mgF- tablets plus placebo rinsing; and (c) placebo tablets plus 1000 ppmF- rinsing. Participants were aged 4.5-5 yr at outset of the trial. At baseline, and annually thereafter, clinical caries and bitewing X-ray examinations were undertaken, hence ethical approval for a negative control was not feasible. Fissure sealant presence was also recorded. Initially, 192 children from predominantly low socio-economic backgrounds were enrolled, and baseline analyses showed no significant differences between groups with respect to primary caries prevalence. After 6 yr, 112 children remained, by which time no significant differences were noted between DMFT and DMFS values for those in the active tablet/active rinse group, as compared to those in the placebo tablet/active rinse group. However, in relation to both indices, in permanent first molars, the effectiveness of the active tablet/placebo rinse regime appeared to be significantly poorer than the placebo tablet/active rinse programme. For the active tablet/active rinse group, the DMFT difference was significantly less than the active tablet/placebo rinse group (37.9%), although for the DMFS difference, significance was not achieved. Similar trends were noted when DMFT and DMFS values for all permanent teeth were considered. The occlusal caries prevalence in permanent first molars followed the DMFT pattern, but differences between combined tablet/rinsing children and tablet-only children could be ascribed solely to the effectiveness of sealant presence.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1990

Salivary levels of mutans streptococci, Lactobacillus, Candida, and Veillonella species in a group of Scottish adolescents.

Salivary levels of mutans streptococci, Lactobacillus, Candida, and Veillonella species were investigated on three occasions at annual intervals in a group of 372 Scottish adolescents. Counts of the micro-organisms studied were logarithmically distributed, with Candida spp. being isolated from approximately half the subjects. Counts of lactobacilli, mutans streptococci, and candida were significantly intercorrelated, while veillonella were associated consistently with mutans streptococci alone. Levels of each of the four micro-organisms were significantly correlated over the three examinations, with levels of the Candida spp. being the most stable over the period studied.

Adolescent↗
PubMed1990

Effect of fluoride concentration on remineralization of carious enamel: an in vitro pH-cycling study.

An in vitro pH-cycling experiment was carried out to investigate the effect of fluoride concentration on enamel demineralization and remineralization. Artificial caries lesions were formed in an acid-buffered solution and subjected daily to a 3-hour acid attack, a 5-min immersion in the test NaF solution (0, 1, 250, 500, 1,000, 1,750 and 2,500 ppm F), and to 21 h in an artificial saliva. Changes in mineral content were assessed weekly for 5 weeks using microradiography/microdensitometry. The lesions in the control group (0 ppm F) and the 1-ppm F group demineralized. Remineralization was significantly higher in the 500-ppm F group compared to the 250-ppm F group. However, higher fluoride concentrations did not produce any further significant increase in remineralization. Laminations were apparent in lesions subjected to the 250- and 500-ppm F solutions.

Bicuspid↗
PubMed1990

The effect of sucrose application and implantation of mutans streptococci on the microbial composition of three-week experimental plaque--an in situ study.

This study describes the predominant cultivable microflora of three-week-old plaque samples obtained from human enamel sites, on the basis of microbial identification of over 9000 fresh isolates. Lower removable appliances, on which were mounted enamel sections and slabs, were worn by five young adult subjects under three experimental protocols. These were (1) 'normal' plaque conditions, (2) extra-oral sucrose applications nine times daily, and (3) inoculation of each subject's own mutans streptococci onto the enamel test sites and sucrose applications, as described above. With the exception of slightly higher proportions of Gram-negative bacilli associated with slab plaque following sucrose application, no significant differences in percentage or absolute counts of organisms were found between normal and sucrose plaques. The inoculation of mutans streptococci, combined with extra-oral sucrose applications, was associated with significantly higher percentages and absolute mean counts of both mutans streptococci and lactobacilli, and lower proportions of S. sanguis and S. oralis. Although the isolation frequency of mutans streptococci increased in all subjects and the overall mean proportion rose following inoculation, considerable inter-subject variation was seen in mean percentage counts of these organisms isolated from the three-week plaque samples.

Adult↗
PubMed1990

An intra-oral appliance study of the plaque microflora associated with early enamel demineralization.

An intra-oral appliance model was used to investigate the composition of the plaque microflora associated with early enamel demineralization. Enamel sections, with exposed windows, were mounted on lower removable appliances, and the devices were worn by volunteers for three-week periods under three experimental conditions. These were: (1) "normal" plaque conditions, (2) extra-oral sucrose applications nine times daily, and (3) inoculation of each volunteer's own mutans streptococci onto the test sites and sucrose applications as described for (2). After 21 days, the plaque overlying each window was removed, and the bacterial composition was determined. Changes in mineral content of the associated enamel were measured by microradiography and microdensitometry, and the total mineral loss (delta z) that had occurred at each site was calculated. The 144 sites studied were divided into four demineralization groups by delta z value, with an increase in mineral loss from group 1 to group 4. A progressive and significant increase in the isolation frequency of mutans streptococci occurred from delta z group 1 to group 4 sites. These organisms were isolated from the plaque of every location with enamel mineral loss of over 1000 delta z units, but were not detected in 27% of the group 3 sites. Lactobacilli comprised 2% to 3% of the total cultivable microflora in groups 1-3 sites, but were found in significantly higher proportions (18%) at those enamel sites experiencing the most extensive mineral loss (group 4). No significant relationship was found between demineralization and the levels of Actinomyces species or Veillonella.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Control of gingivitis and calculus by a dentifrice containing a zinc salt and triclosan.

The effect of unsupervised brushing with a dentifrice containing two antiplaque agents, 0.5% zinc citrate and 0.2% triclosan, on gingival health, plaque, supragingival calculus, and the oral flora was compared to brushing with a non-active control dentifrice. Volunteers were given oral hygiene instruction and their teeth were professionally cleaned. They then used a placebo dentifrice for a pre-experimental phase of 1 month, before being stratified into two groups on the basis of their initial plaque, gingival bleeding, and calculus levels, sex, and age. Over the following 6 months, one group used the control while the other used the test dentifrice. Plaque levels, gingival bleeding, and calculus were assessed at baseline and at 3 and 6 months. Supragingival plaque was sampled for microbiological analysis at the initial examination, at 3 and 6 months (conclusion of study period) and 3 months after the study. Representative oral bacteria and the development of bacterial resistance to triclosan were monitored. Results showed that plaque was reduced and gingival health significantly improved during the 1-month pre-experimental period. During the experimental period, this improvement was not maintained by the control group as gingival bleeding and calculus increased. In contrast, gingival bleeding and calculus levels of the test group were maintained significantly below those of the placebo group. Plaque levels were lower in the test group after 3 and 6 months, but the groups were not significantly (P = 0.05) different. No shifts in oral flora or development of bacterial resistance to triclosan were detected.

Adolescent↗
PubMed1990

Fissure sealant retention: a comparison of three sealant types under field conditions.

Two two-year double-blind clinical trials were undertaken involving the newly-erupted first permanent molars of 133 children aged 5-6 years at the outset. In one study of 76 subjects, half the teeth were sealed with the filled sealants Prismashield or Estiseal. In the other study of 58 children, half were again sealed with Prismashield, and the others with the unfilled Concise white sealant, by a community dental service hygienist, as part of her routine dental duties. Subjects were examined under blind conditions at 6 monthly intervals and, by 24 months in the first study, 71 per cent of Prismashield sites were intact and caries-free, compared with only 53 per cent of Estiseal-treated tooth units (P less than 0.001). In the second study comparing Prismashield and Concise, by two years, 81 per cent of Prismashield resins were complete, compared with 88 per cent of the nonfilled Concise material. There were, however, no differences noted with respect to buccal and palatal site retention for either study. It can be concluded that Estiseal is a poorer material than Prismashield, certainly in relation to its bulk retention properties. Nonetheless it is possible that, along with other tooth-coloured/transparent resins, small fragments may not be as readily detectable as is the case with the unfilled Concise white sealant. However, as the abrasion resistance of unfilled materials is poorer than that of filled resins, the similar buccal/palatal site retention for Prismashield and Concise was also unexpected. Nevertheless this study illustrates again the value of sealant placement in the erupting first permanent molars of 5-6-year-old children, at a time when these teeth are most susceptible to carious attack.

Acrylic Resins↗
PubMed1988

A 3-year oral health dose-response study of sodium monofluorophosphate dentifrices with and without zinc citrate: anti-caries results.

A 3-yr clinical trial has been conducted on 3000 12-yr-old children in Lanarkshire, Scotland, with the aim of investigating the effects on oral health of toothpastes containing both sodium monofluorophosphate and zinc citrate, the former being present at fluoride levels of 1000, 1500, and 2500 ppm F. No significant difference in caries increments was found between the group of children using toothpastes incorporating zinc citrate and their counterparts using zinc-free pastes. However, a significant anti-caries dose-response was demonstrated over the SMFP range used. This dose-response was evident for boys and girls and also for the various types of teeth and tooth surfaces.

Child↗