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D T Zero

Publications and source records attributed to D T Zero.

18 recordsLinked to original sources
PubMed1995

In situ caries models.

By using in situ models, we have the potential to study both fundamental aspects of the caries process as well as more applied research problems such as the effect of food on dental caries and the role of fluoride in caries prevention in human subjects without actually causing caries in the natural dentition. The key experimental parameters that need to be considered in the development of an in situ model are the characteristics of the subject panel, the physical design of the model, the type of hard tissue substrate and the method of assessing mineral status, and the study design and clinical protocol. Each parameter must be carefully considered in relation to the objectives of the research, study design requirements, ethical considerations, impact on clinical relevance, and impact on the control of variation. The major source of variation associated with in situ models should be of biological and not experimental origin. The design and conduct of proper in situ model studies require a clear understanding of the caries process, sound analytical support, and a knowledge of how to work with research subjects to achieve a high level of compliance. Given the complex nature of caries, a combination of hard tissue substrates--including sound, surface-softened lesions and subsurface lesions--may be necessary to model all aspects of caries progression and prevention successfully. Internal validation of in situ models using fluoride dose-response controls is considered to be necessary for studies evaluating the efficacy of new fluoride dentifrice formulations.

Animals↗
PubMed1995

An overview of caries risk assessment, and its potential utility.

The clinical findings that dentists use to estimate the future caries activity of patients are imperfect. Almost invariably there are protective factors in patients who go on to develop clinical caries and there are risk factors that persist in patients who do not develop clinical caries. Therefore, the clinical decision process is characterized by a level of uncertainty concerning the selection of patient management strategies for caries. To the degree that information relating to caries risk assessment can reduce the amount of uncertainty associated with decisions for clinical patient care in the present, that information has utility. Dentists face many treatment decisions daily. The integration of a mechanistic understanding of caries and use of clinical data may yield useful information that will improve clinical patient management. Certain factors affect the potential utility of caries risk screening from the clinician's perspective. These can be summarized in terms of the costs and benefits of the procedures as well as the availability and appeal of alternative procedures. Factored in with these considerations are the investment history one has made toward a given procedure and the propensity for changing one's behavior. These considerations are not easily addressed at present since costs and benefits for different therapeutic approaches have been developed for only a few dental conditions. We have put forth a framework that emphasizes the clinician as the key component in the assessment of caries risk. We argue that integration of the clinician's focus with a mechanistic understanding of caries and a probabilistic, empirical appreciation for caries activity will be beneficial for patient management. These arguments remain untested and should be challenged in a research setting. We need to establish whether information derived from risk assessment procedures leads to improved clinical outcomes. We need to have a better understanding of how clinicians process clinically available risk information. We need to determine what additional risk assessment information will improve the clinician's ability to identify high-risk patients. We also need to establish whether there are differences in the usefulness of additional risk information depending on the level of experience of the clinician.

Cost-Benefit Analysis↗
PubMed1995

Comparison of cell sediment and surface grown "test plaque" using scanning electron microscopy.

Scanning electron microscopy was used to compare the morphology, integrity and distribution of bacterial cells in a test plaque grown on the surface of enamel with that of the cell sediment plaque routinely used in a short-term intraoral caries model. Cultures of S. mutans IB-1600 or S. sobrinus 6715-13 were grown in complex media supplemented with either 2.0% sucrose (glucan plaque) or 0.2% glucose (non-glucan plaque). Cell sediment (CS) plaque was prepared by centrifuging the cultures after incubation, recovering the cell sediment, and spreading it on Metricel membrane filter paper. Surface grown (SG) plaque was prepared by suspending saliva-coated bovine enamel in the culture medium, incubating, and recovering the enamel assembly with bacterial accumulations. Cell morphology and integrity, as well as the appearance of glucan-like material produced by the cells, was similar in both CS and SG test plaques. The cell distribution however, varied in the SG plaque from extremes of all cells to all glucan, whereas the cell sediment plaque was more uniform in cell distribution. A highly standardized test plaque minimizes variability in the intraoral caries model. These findings support the contention that the bacterial cells in a cell sediment plaque are similar in morphology, integrity and glucan production to surface grown plaque, and have the added advantage of uniform distribution, which makes the cell sediment plaque more appropriate for intraoral caries model studies.

Animals↗
PubMed1994

Calcium fluoride formation on sound enamel using fluoride solutions with and without lactate.

The formation of calcium (Ca) fluoride (CaF2) on bovine enamel blocks during clinically relevant treatment times using neutral fluoride (F) solutions (0.26 mol/l F) with and without 0.1 mol/l lactate was investigated. Uncoated and pellicle-coated blocks were evaluated for alkali-soluble (1 mol/l KOH, three consecutive 24-hour treatments) Ca, PO4, and F after treatment by the F solutions for 0, 5, 15, 30, and 60 min. There was an overall time-related increase in F recovery, while Ca tended to remain at baseline levels. Less F was recovered from the pellicle-coated blocks. The addition of lactate to the F treatment solution did not result in an overall increase in alkali-soluble F recovery, but did result in the formation of cuboidal shaped crystals which closely approached the morphology of pure CaF2. A 1:2 stoichiometric ratio Ca:2F (mol:mol) was not established based on chemical analyses. The ultrastructural and elemental composition of surface deposits on the samples, as determined using scanning electron microscopy, X-ray diffraction, and energy-dispersive spectroscopy, established the presence of CaF2 after 24-hour F treatments; however, it was not possible to directly demonstrate the formation of CaF2 after clinically relevant treatment times.

Animals↗
PubMed1993

Effect of chewing xylitol chewing gum on salivary flow rate and the acidogenic potential of dental plaque.

Ten adults participated in the study which consisted of four experimental periods each lasting 2 weeks, during each of which subjects were assigned to one of four gum-chewing regimens: no gum, sucrose gum, sorbitol gum and xylitol gum. At the start and end of each test period unstimulated and stimulated salivary flow rates were determined. At the end of each test period the acidogenic potential of 48-hour dental plaque was measured using a Beetrode pH microelectrode. No statistically significant (p < 0.05) effect on salivary flow rate was observed. The xylitol chewing gum regimen resulted in significantly higher plaque pH than no gum, sucrose gum and sorbitol gum at 2, 10, 20, 30 and 60 min following a 10% sucrose rinse. In addition, xylitol gum regimen exhibited a significantly higher minimum pH and smaller area of the curve below pH 6. The results suggest that the regular use of xylitol-sweetened gum may serve to reduce the acidogenic potential of dental plaque.

Adult↗
PubMed1993

Article in error.

Explore the source record for details and available documents.

Dental Caries↗
PubMed1992

Studies of fluoride retention by oral soft tissues after the application of home-use topical fluorides.

Previous studies have focused on enamel and plaque as the primary sites of fluoride (F) retention in the mouth. The present study was undertaken to evaluate the role of oral soft tissue as a site of F retention by comparing an edentulous subject panel (n = 9) with a fully dentate panel (n = 10). Unstimulated whole saliva samples were collected by having subjects pool saliva for two min. Samples were collected over a 24-hour period after application of a placebo dentifrice (PD; 0.4 ppm F), fluoride dentifrice (FD; 1100 ppm F), fluoride rinse (FR; 226 ppm F), or fluoride gel (FG; 5000 ppm F) delivered in custom trays. There was no statistically significant difference in salivary flow rate between the two panels for any of the treatments. The edentulous panel had higher salivary F levels than the dentate panel, which reached statistical significance (p less than 0.05) for the FD and FG treatments. In a separate study involving the same treatments, F levels at specific soft-tissue sites were measured over a one-hour period by use of absorbent discs placed in different soft-tissue areas of the mouth. The tongue and lower posterior vestibule retained the highest F levels, followed by the upper posterior buccal vestibule and upper anterior labial vestibule, with the lowest F levels retained in the lower anterior vestibule and the floor of the mouth. There was a strong-to-moderate correlation between whole saliva F concentration and F levels at specific soft-tissue sites. This study establishes the importance of oral soft tissue as the major site of F retention in the mouth.

Analysis of Variance↗
PubMed1992

An in situ model for simultaneous assessment of inhibition of demineralization and enhancement of remineralization.

In situ models to assess the ability of oral care products or food components to enhance remineralization and/or inhibit demineralization of tooth enamel or roots must be very carefully designed to minimize the confounding effects of the many variables involved. Controlling these variables as closely as possible is essential if meaningful answers are to be obtained from the models. We have developed an in situ model which combines the experience of several groups. Detailed screening of subjects is essential. Selection criteria should include good general health, good dental health, mandibular partial denture, at least eight natural teeth, no active caries lesions, known fluoride history, normal salivary function, and no medications that affect salivary function. Each subject carries a sound enamel slab and an enamel slab with a pre-formed caries-like lesion (demineralized in vitro) in his/her denture on each side of the mouth for test periods of two or four weeks. The demineralization challenge is controlled by extra-oral immersion of the appliances in sucrose daily. Daily product exposure or daily food component exposure is used as desired. Compliance indicators and a diet diary are included. Whole saliva flow rate (unstimulated), plaque acidogenicity, and salivary fluoride are monitored during the test periods. At the end of the test period, the test slabs are assessed for mineral change, after being sectioned, by means of cross-sectional microhardness or microradiography. The mineral loss or gain (delta M, microns x vol%), compared with adjacent control sections retained in the lab, is calculated as change in delta Z (microns x vol%), namely, delta M = delta ZTEST - delta ZCONTROL.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

An improved intra-oral enamel demineralization test model for the study of dental caries.

The intra-oral enamel demineralization test (IEDT) was introduced by Brudevold et al. (1984). This caries model involves human subjects wearing palatal appliances each holding eight bovine enamel blocks covered by a bacterial cell layer prepared by the harvesting of cultures of Streptococcus mutants (test plaque). The original model used the iodide permeability test for assessment of the extent of demineralization of bovine enamel blocks resulting from acid production by the test plaque after dietary substrate challenge. The IEDT model has been expanded and improved by us in the following ways: (1) Based on encouraging findings from an in vitro study (Zero et al., 1990), the surface microhardness test has been adopted to measure the extent of demineralization occurring at three sites on the enamel blocks corresponding to an area over which the effective plaque thickness is 0.5, 1.5, and 2.5 mm; (2) intra-oral pH of the test plaque is measured by means of a Beetrode miniature pH electrode at baseline, then at five, 10, 15, 30, and 45 min after the start of a test; (3) plaque samples are collected at the end of a test and analyzed for organic acid content by means of HPLC; (4) the bacterial test challenge has been expanded to include different cariogenic bacteria which are grown under various growth conditions. The improved model has the capability of studying fundamental aspects of the caries process, namely, the relationships among dietary substrate challenge, plaque pH change, plaque organic acid profiles, microbial virulence properties, and enamel demineralization. Furthermore, the model has the potential for use in more applied research on caries-preventive agents such as fluoride.

Adult↗
PubMed1992

Fluoride concentrations in plaque, whole saliva, and ductal saliva after application of home-use topical fluorides [published eerratum appears in J Dent Res 1993 Jan;72(1):87].

It is now well-accepted that the primary anti-caries activity of fluoride (F) is via topical action. The retention of F in the mouth after topical fluoride treatment is considered to be an important factor in the clinical efficacy of F. The purpose of this study was to evaluate F levels in ductal saliva, whole saliva, and pooled plaque after treatment with topical F agents intended for home use. Ten consenting adults, mean (SD) age 31.0 (8.2) years, participated in all aspects of the study. Two days before each test, subjects received a professional tooth cleaning and subsequently abstained from all oral hygiene procedures to permit plaque to accumulate, and from the use of F-containing dental products. Treatments consisted of a placebo dentifrice (PD), fluoride dentifrice (FD; 0.24% NaF), fluoride rinse (FR; 0.05% NaF), and fluoride gel (FG; 1.1% NaF). Unstimulated whole saliva and pooled plaque were sampled at multiple points over a 24-hour period. In a separate experimental series, stimulated parotid saliva was sampled over a two-hour period after treatment. Fluoride levels generally followed the same pattern in whole saliva and pooled plaque samples, with FG > FR > FD > PD. Night-time F application resulted in prolonged F retention in whole saliva but not in plaque. Fluoride levels in parotid saliva were only slightly higher after F treatment and returned to baseline levels within two h. The results of this study indicate that the method of F delivery, the F concentration of the agent, and the time of application (daytime vs. night-time) are important factors influencing F levels in the mouth.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Use of an intra-oral model to evaluate 0.05% sodium fluoride mouthrinse in radiation-induced hyposalivation.

The present study was undertaken to evaluate the effect of a twice-daily topical application of a 0.05% NaF mouthrinse on de- and remineralization in the oral cavities of subjects suffering from radiation-induced hyposalivation. Six subjects each wore a bonded intra-oral appliance containing a sound and a demineralized human enamel slab for four weeks. During that period, the subjects used 0.05% NaF rinses, twice daily, instead of the 1.1% NaF gel that had previously been a part of their preventive regimen. Salivary flow rates, plaque pH profiles following a 10% sucrose rinse, S. mutans and lactobacillus counts, fluoride clearance, and enamel microhardness were determined during the study. Sound enamel samples displayed no evidence of demineralization, and the previously demineralized enamel showed remineralization in the outer 50 microns in three of the six subjects. The results suggest that a twice-daily oral rinse with 0.05% NaF can prevent demineralization and enhance remineralization in subjects with radiation-induced hyposalivation.

Bacteria↗
PubMed1990

Comparison of the iodide permeability test, the surface microhardness test, and mineral dissolution of bovine enamel following acid challenge.

The relationship among the iodide permeability (Ip) test, the surface microhardness (SMH) test, and enamel demineralization chemically analyzed as mineral loss was investigated using bovine enamel blocks. Demineralization periods of 0 (control) and 5, 15, 30, and 45 min using 0.05 mol/l lactate (pH 4.75) were chosen to approximate the acid challenge occurring during the intraoral enamel demineralization test. Mineral loss (Ca and PO4) was found to be directly proportional to dissolution time (r = 0.95). Changes (delta) in Ip and SMH each increased linearly over time (r = 0.58 and 0.64, respectively) and were similarly related to mineral loss (r = 0.60 and 0.65, respectively). The correlation between delta Ip and delta SMH was 0.55. When longer demineralization periods (60, 120, and 240 min) were included, the correlation between delta Ip and delta SMH was 0.68. We conclude that both the Ip test and the SMH test can be used as measures of the early stages of enamel dissolution.

Animals↗
PubMed1988

Comparison of fluoride concentrations in unstimulated whole saliva following the use of a fluoride dentifrice and a fluoride rinse.

Recent evidence has suggested that the cariostatic effects of topical fluoride (F) are related to the presence of low concentrations of ionic F in the oral environment. The purpose of this study was to compare the retention of F in the oral environment over 24-hour periods after the use of a F dentifrice or a F rinse. Groups of ten consenting adult subjects (age 18-52 years) brushed and/or rinsed (B/R) in a standardized manner twice per day in the morning (AM) and before bed (PM) with either a placebo dentifrice (8 ppm F), NaF dentifrice (1100 ppm F), or NaF rinse (225 ppm F). Experiments were performed with placebo dentifrice only (PD); F dentifrice only (FD); F dentifrice followed by F rinse (FD/FR); placebo dentifrice followed by F rinse (PD/FR); and F rinse followed by placebo dentifrice (FR/PD). Unstimulated whole saliva samples were collected at baseline and then at 0, 15, 30, and 45 min, 1, 2, and 8 hr after B/R in the AM, after B/R in the PM and upon rising the following morning. Salivary flow rate and F were determined for each sampling interval. The results of this study suggest that: (1) F rinse may be a more effective way of delivering topical F than F dentifrice; (2) based on F retention, the combination of FD/FR was not more effective than FR only (PD/FR); (3) older individuals with gingival recession retained higher F levels; and (4) bedtime F application resulted in longer F retention than did daytime application, which may have important implications for enamel remineralization.

Adolescent↗
PubMed1986

Enamel demineralization by acid produced from endogenous substrate in oral streptococci.

Bovine enamel blocks were covered by a bacterial cell mass and held in the mouths of human volunteers by a palatal appliance, to study the effects of acid production from endogenous bacterial substrate on the pH of the mass and on enamel demineralization. Variables were cells with and without endogenous substrate, rinsing with 10 per cent glucose or sucrose solution, or no rinsing and the type of organism. Acid production from endogenous substrate by Streptococcus mutans strain IB-1600, due, at least in part, to intracellular glycogen degradation, caused a marked and prolonged pH drop and significant enamel demineralization. A similar but less marked effect was obtained with a strain of Streptococcus mitis, Streptococcus sanguis and Actinomyces viscosus. Thus acid production from endogenous sources by plaque bacteria may be of importance in the aetiology of dental caries.

Acids↗
PubMed1986

Oral food clearance and the pH of plaque and saliva.

Carbohydrate clearance, plaque pH, and saliva pH resulting from eating foods containing high levels of sugar or starch were measured in the same experimental runs on the same test subjects. Foods with a higher content of sugar were removed more rapidly and depressed the pH of the plaque for a shorter time than did starchy foods containing less sugar. This finding suggests that retention of food in the mouth may be as important an indicator of its cariogenic potential as is the level of the pH it produces in plaque.

Adult↗
PubMed1986

The intra-oral effect on enamel demineralization of extracellular matrix material synthesized from sucrose by Streptococcus mutans.

The role of extracellular matrix material (EMM) synthesized from sucrose (S) by Streptococcus mutans IB-1600 in altering the demineralizing potential of artificial plaque was evaluated with an intraoral enamel demineralization test (IEDT). The artificial plaque samples were prepared from cells cultivated in Todd-Hewitt broth (THB) supplemented with various S concentrations and by mixing THB-grown cells with increasing proportions of EMM (heat-killed THB + 2% S-cultivated cells). The samples were also evaluated for cell density (DNA content) and acidogenicity in vitro (pH-stat), as well as for in situ pH changes during a 45-minute intra-oral test following a 10% glucose rinse. An increase in the proportion of EMM relative to cell density was associated with an increase in enamel demineralization. This trend reversed when the ratio of cells to EMM was less than 1:19. Experiments involving strains of S. mitis, S. sanguis, and S. salivarius suggested a similar effect of EMM. The intra-oral pH data suggest that the presence of EMM may enhance demineralization by altering diffusion properties of plaque.

Acids↗
PubMedDate not supplied

The effectiveness of sponge-type intraoral applicators for applying topical fluorides in institutionalized older adults.

Many older adults who reside in nursing homes have disabilities which limit their capacity to benefit from the usual protocols for prevention of dental caries. This is a report of a study of the effectiveness of an alternative method of applying topical fluoride in the institutionalized elderly. Fluoride gel (1.1% NaF) was applied to the facial tooth surfaces of 10 elderly nursing home residents using a sponge-type intraoral applicator (IA). Subsequently, the same subjects rinsed with a commercial fluoride solution (0.05% NaF). Salivary fluoride levels were then assessed by the Taves (1968) method. The IA with fluoride produced significantly higher salivary fluoride levels over a period of three hours compared with rinsing.

Aged↗