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D C Clark

Publications and source records attributed to D C Clark.

At least 55 records · Page 3Linked to original sources
PubMed1995

Evaluation of aesthetics for the different classifications of the Tooth Surface Index of Fluorosis.

The prevalence of dental fluorosis for children both from fluoridated and non-fluoridated communities has increased dramatically in some regions of North America. This study evaluated the aesthetics of dental fluorosis for school-aged children from a reference population of 1131 children. The methodology from the Social Acceptability Scale of Occlusal Conditions (SASOC), part of the Dental Aesthetics Index (DAI), was used to assess fluorosis-related aesthetics. Pairs of semantic differentiated adjectives adapted from SASOC were used to rate fifty 35 mm slides of anterior teeth. Sampling of children from the different categories of the Tooth Surface Index of Fluorosis (TSIF) on anterior permanent teeth was weighted to permit sufficient numbers of slides for the different classifications of the TSIF. Each slide was presented to a stratified random sample of pairs of parents and children who were participants in the original study. A convenience sample of dental professionals was also included. Analysis compared different classifications of "affected" slides (non-zero TSIF scores), with the mean aesthetic score computed from all "non-affected" slides (TSIF = 0). Results from children, parents, and professionals showed that there were highly significant differences between ratings of low and high TSIF scores. The only non-significant differences were between TSIF 4 and TSIF 5 & 6, which all three groups did not distinguish, as well as TSIF 1 versus TSIF 2 & 3, which children could not distinguish.

Attitude of Health Personnel↗
PubMed1995

DQE(f) of four generations of computed radiography acquisition devices.

Measurements were made of the MTF(f), NPS(f), and DQE(f) of four generations of computed radiography (CR) imaging plates and three generations of CR image readers. The MTF generally showed only a minor change between generations of plates and readers, but the DQE(f) has improved substantially from a very early plate/reader combination to a more recent one. The DQE in the more recent plate/reader combination is 1.3X greater at low frequencies and about 3X greater at high frequencies than the much earlier versions. Thus there has been substantial improvement in the imaging performance obtainable with CR since some of the early observer studies which indicated poorer performance with CR than with screen-film.

Humans↗
PubMed1994

Cheek cell membrane fluidity measured by fluorescence recovery after photobleaching and steady-state fluorescence anisotropy.

Membrane fluidity of human cheek cells was determined using fluorescence recovery after photobleaching (FRAP) and steady-state fluorescence anisotropy. The FRAP data showed that the lateral diffusion coefficient (D) and mobile fraction (%R) of lipid in the plasma membrane of control cells were 2.01 x 10(-9) cm2/sec and 54.25%, respectively. Trypsin treatment increased D and %R to 6.4 x 10(-9) cm2/sec and 72.15%. In contrast, the anisotropy (r) for control cells was 0.270 which remained unchanged by trypsin treatment. The results show that diffusion of lipids in the plane of the membrane is restricted by trypsin-sensitive barriers.

Cell Membrane↗
PubMed1994

Influence of exposure to various fluoride technologies on the prevalence of dental fluorosis.

An increase in the prevalence of dental fluorosis among children in North America is well documented. Published reports of the relationship between the occurrence of dental fluorosis and early exposure to various fluorides and the use of different types of infant feeding practices have begun to provide insights into possible causes for this increase. This study was designed to investigate this issue for children living in a non-fluoridated and a fluoridated community in British Columbia, Canada. Parents or guardians completed a questionnaire which detailed exposure to different types of fluorides and infant feeding practices during the first 6 yr of life. Completed questionnaires were returned and examinations were performed on 1131 children. 60% of children had dental fluorosis, and only 8% presented with scores of 2 or greater. Logistic regression analyses showed that the use of infant formula and parental educational attainment were significantly associated with the occurrence of dental fluorosis in the range of scores from 2 to 6. Despite these statistically significant findings, these variables actually had little additional predictive value beyond a chance occurrence in determining which children would have dental fluorosis.

Adolescent↗
PubMed1994

Trends in prevalence of dental fluorosis in North America.

This review of the literature was undertaken to demonstrate the changing trends in the prevalence of dental fluorosis in North America. Using Dean's early work to establish a baseline for the prevalence of dental fluorosis, results of more recent prevalence surveys were used to establish a range for the occurrence of dental fluorosis today. These results suggest that the prevalence of dental fluorosis now ranges somewhere between 35% and 60% in fluoridated communities and between 20% and 45% in nonfluoridated areas, depending on the influence of different local conditions. While the increase has occurred primarily in the very mild and mild categories of dental fluorosis, there is also some evidence that the prevalence is increasing in the moderate and severe classifications as well.

Adolescent↗
PubMed1994

The effectiveness of three different strengths of chlorhexidine mouthrinse.

Dental caries in dentate elderly patients may be controlled with chlorhexidine. The purpose of this study is to establish the effectiveness of two low-concentration chlorhexidine mouthrinses in reducing the microbial counts of cariogenic bacteria in a sample of institutionalized elders. Stimulated saliva samples from all subjects before treatment produced counts greater than or equal to 105 colony-forming units (CFU)/mL of lactobacilli and/or mutans streptococci. Treatment consisted of daily rinsing with 4.0 mL of mouthrinse before bed for 14 days. Bacterial counts were re-assessed two weeks after commencing treatment. The mean reduction in mutans streptococci counts in subjects receiving the regular-strength chlorhexidine mouthrinse (Group B) was significantly greater than for subjects using either of the low-concentration rinses (Groups A and C). These findings failed to demonstrate the effectiveness of the lower-concentration mouthrinses (Groups A & C).

Aged↗
PubMed1994

Chlorzoin.

Explore the source record for details and available documents.

Canada↗
PubMed1993

Appropriate uses of fluorides for children: guidelines from the Canadian Workshop on the Evaluation of Current Recommendations Concerning Fluorides.

OBJECTIVE: To prevent fluorosis caused by excessive fluoride ingestion by revising recommendations for fluoride intake by children. OPTIONS: Limiting fluoride ingestion from fluoridated water, fluoride supplements and fluoride dentifrices. OUTCOMES: Reduction in the prevalence of dental fluorosis and continued prevention of dental caries. EVIDENCE: Before the workshop, experts prepared comprehensive literature reviews of fluoride therapies, fluoride ingestion and the prevalence and causes of dental fluorosis. The papers, which were peer-reviewed, revised and circulated to the workshop participants, formed the basis of the workshop discussions. VALUES: Recommendations to limit fluoride intake were vigorously debated before being adopted as the consensus opinion of the workshop group. BENEFITS, HARMS AND COSTS: Decrease in the prevalence of dental fluorosis with continuing preventive effects of fluoride use. The only significant cost would be in preparing new, low-concentration fluoride products for distribution. RECOMMENDATIONS: Fluoride supplementation should be limited to children 3 years of age and older in areas where there is less than 0.3 ppm of fluoride in the water supply. Children in all areas should use only a "pea-sized" amount of fluoride dentifrice no more than twice daily under the supervision of an adult. VALIDATION: These recommendations are almost identical to changes to recommendations for the use of fluoride supplements recently proposed by a group of European countries. SPONSORS: The workshop was organized by Dr. D. Christopher Clark, of the University of British Columbia, and Drs. Hardy Limeback and Ralph C. Burgess, of the University of Toronto, and funded by Proctor and Gamble Inc., Toronto, the Medical Research Council of Canada and Health Canada (formerly the Department of National Health and Welfare). The recommendations were formally adopted by the Canadian Dental Association in April 1993.

Canada↗
PubMed1993

Expression and characterization of the N-terminal domain of an oleosin protein from sunflower.

Oil bodies of plant seeds contain a triacylglycerol matrix surrounded by a monolayer of phospholipids embedded with alkaline proteins termed oleosins. Although oleosins are amphipathic proteins, they are unlike bilayer membrane proteins since they are associated with a single lipid:water interface at the oil body surface. Oleosins are unusual proteins because they contain a 70-80-residue uninterrupted nonpolar domain, flanked by relative polar C- and N-terminal domains. In the present study, we report the expression of the N-terminal domain of the 18-kDa oleosin isoform from sunflower as a recombinant fusion protein in Escherichia coli and the determination of its secondary structure using CD and Fourier transform infrared spectroscopy either as a purified but partially denatured peptide or reconstituted into liposomes. The structure derived from physical studies was then compared and assigned with those predicted from analysis of the primary sequence of the N-terminal domain. Based on data derived from CD spectroscopy analysis of purified and partially renatured N-terminal polypeptide, it contains about 10% alpha-helical structure, 20-30% beta-strand structure, approximately 8% beta-turn structure, and 60% random coil structure. However, analysis of the polypeptide reconstituted into liposomes showed an increased content of alpha-helical structure to about 20% and an increased beta-strand structure content to about 30-40%. Data derived from Fourier transform infrared spectroscopy studies and compared with the data predicted from the primary sequence showed the peptide is well structured with some antiparallel beta-strand structure from residues 2-9, parallel beta-strand structure from residues 30-37 and/or 42-49, and alpha-helical structure from residues 10-23 and/or 43-49. There is potential amphipathic alpha-helix from residues 10-23. Based on these results, the following model for the secondary structure of the N-terminal domain of sunflower oleosin can be proposed. Residues 2-9 would produce amphipathic antiparallel beta-strand structure. Residues 10-23 would produce an amphipathic alpha-helical structure. Residues 30-37 and/or 42-49 would give parallel beta-strand structure, or residues 42-49 could form a nonpolar alpha-helical structure that would insert into the oil matrix.

Amino Acid Sequence↗
PubMed1993

The natural history of interstitial cystitis: a survey of 374 patients.

A survey directed at determining the natural history of interstitial cystitis was conducted at our clinic. Information on demographics, risk factors, symptoms, pain and psychosocial factors was elicited from 374 patients who satisfied the National Institute of Arthritis, Diabetes, Digestive and Kidney Diseases criteria for interstitial cystitis and had all been diagnosed as having interstitial cystitis by a urologist. With regard to demographics, patients were predominantly female (89.8%) and white (94.1%), with a mean age of 53.8 +/- 0.7 years (standard error) and age at the first symptoms of 42.5 +/- 0.8 years. Information on 25 potential risk factors included 44.4% of the women reporting hysterectomy, 38.2% of the patients having strong sensitivities or allergic reactions to medication and only 2.7% being diabetic. With regard to interstitial cystitis symptoms, frequency and urgency were reported by 91.7% and 89.3% of the patients, respectively, while pelvic pain, pelvic pressure and bladder spasms were reported by more than 60% of respondents and burning by 56%. Location and degree of pain were also reported. Urination relieved or lessened interstitial cystitis pain for 73.6% of the patients and medication was effective for 46.8%. Other behaviors (for example hot baths, heating pads, lying down or sitting) were less effective. Conversely, stress, constrictive clothing and intercourse increased interstitial cystitis pain in more than 50% of the patients. In addition, acidic, alcoholic or carbonated beverages, and coffee or tea increased interstitial cystitis pain in more than 50% of the patients. More than 60% of the patients were unable to enjoy usual activities or were excessively fatigued and 53.7% reported depression. Travel, employment, leisure activities and sleeping were adversely affected in more than 80% of the patients. Pain location and degree differed significantly between patients with and without ulcers in the bladder. In addition, there was an apparent plateau in the frequency and urgency among patients after approximately 5 years with symptoms.

Adult↗
PubMed1993

Aesthetic concerns of children and parents in relation to different classifications of the Tooth Surface Index of Fluorosis.

Increasing prevalence of dental fluorosis for children both from fluoridated and non-fluoridated communities are now well documented. Along with recent studies purporting possible adverse health effects from fluorides, this proven public health intervention is again being challenged. This study was undertaken to determine the prevalence of dental fluorosis for children from fluoridated and non-fluoridated areas in British Columbia. In addition, children and parents were provided with an opportunity to express concerns about the aesthetics of the child's anterior teeth. Children from representative schools in two communities were surveyed using the Tooth Surface Index of Fluorosis (TSIF). Questionnaires were sent home to parents to detail their child's use of various fluoride preventive practices and residence histories. Completed questionnaires were returned and exams were performed on 1131 children. Of those examined, 60% had dental fluorosis on at least two tooth surfaces, only 8% had scores ranging from "2" to "6", and 52% were classified with a score of "1". Parental and child ratings on the aesthetics or color of the child's teeth suggests that there are few children with aesthetic problems in the TSIF category of "1". While concerns of parents were more common, the actual source of those concerns was not assessed in the questionnaire. Not unexpectedly, children with fluorosis on anterior teeth ranging between TSIF scores of "2" to "6" appear to have increased concerns about tooth color. Data from children with confirmed residence histories from fluoridated communities suggest that the occurrence of aesthetic problems in these children is rare.

Adult↗
PubMed1993

Predictors of caries in old age.

This study measured the incidence of dental caries for one year and identified factors associated with the risk of caries in a sample of 156 elderly subjects. The subjects were examined at baseline and after one year to record the number of missing, filled and decayed teeth, to measure oral hygiene and flow of saliva, and to estimate the numbers of Streptococcus mutans and Lactobacilli cultured from samples of saliva. All subjects were interviewed on both occasions for information on their use of medications and dental services and on their ingestion of sugar. At baseline the elders had a mean of 19 natural teeth with 5 decayed surfaces (DS), 38 filled surfaces and a mean Plaque Index (PI) of 1. The independent group, on average, had more teeth and fillings but a lower PI and less caries. At the end of the year more than two-thirds (71%) of the 98 institutionalised subjects and over half (59%) of the 58 independent subjects had at least one new decayed/filled surface (DFS). The mean net DFS increment per subject was 4.6 and 2.0 respectively. Regression analyses on multivariate models identified caries at baseline, residence in long term care facilities, high numbers of Lactobacilli, poor oral hygiene and frequent sugar consumption as the variables contributing most significantly to the risk of caries in old age.

Aged↗
PubMed1993

Assessing the severity of depressive states in recently detoxified alcoholics.

The problem of how to assess "unbiased" symptoms of depression meaningfully in the context of alcoholism bedevils studies of concomitant alcoholism and affective disorder. This study summarizes this controversy and discusses its implications for developing improved measures of depression severity among alcoholics. The Beck Depression Inventory (BDI) responses of 130 alcoholic applicants applying for inpatient care were evaluated using a two-parameter normal item response model. This study demonstrates that a single dimension of depression severity accounts for patient responses well, but that seven BDI items were relatively poor markers of syndrome severity for these alcoholics. The study documents growing consensus among investigators as to which BDI items constitute a fair scale of depression severity among alcoholic patients The availability of "unbiased criteria" for assessing the severity of depression among alcoholics applying for inpatient treatment will enable investigators and clinicians to recognize patients with concomitant alcoholism and affective disorder for special attention and/or treatment. The modified BDI scale proposed here is a candidate for a clinical definition of depression severity among alcoholic patients by virtue of this study's demonstration that it defines a distinct syndrome in this patient sample; but the modified scale must undergo independent tests of validity before its clinical utility can be established.

Adult↗