Search PubMed⌕ Search

Biomedical subjects

J D Featherstone

Publications and source records attributed to J D Featherstone.

At least 37 records · Page 2Linked to original sources
PubMed1996

Modeling the caries-inhibitory effects of dental materials.

The objectives of this review are to compare the models that are used to simulate the caries process in cardiology research and to suggest how these models might be used to assess caries-inhibitory properties of dental materials. Available caries-simulation models fall into the following classifications: 1) in vitro demineralization using acid buffers, 2) in vitro demineralization using bacterially generated acids, 3) in vitro demineralization/remineralization using a pH-cycling system, 4) an artificial mouth where a bacterially generated acid challenge is interspersed with a "saliva" treatment, 5) in vivo animal model (generally with rats), 6) in situ demineralization and/or remineralization using enamel or dentin blocks or slices in the human mouth, and 7) in vivo studies using teeth scheduled for extraction in the human mouth. Most dental materials studies have used simple in vitro demineralization models or component release experiments, each of which is inadequate to answer the questions that are being asked about the caries-inhibitory properties of the material being tested. Experimental methods must be chosen with care to ensure that the material to be tested is examined in an appropriate mode. The ultimate goal is to correctly predict clinical outcomes. The design or redesign of a model must eventually be tied to documented clinical outcomes to improve the model and allow for future successful development of new materials.

Animals↗
PubMed1995

Lasers in dentistry.

Since the development of the ruby laser by Maiman in 1960, there has been great interest among dental practitioners, scientists, and patients to use this tool to make dental treatment more pleasant. Oral soft tissue uses are becoming more common in dental offices. The possible multiple uses of lasers in dentistry, beyond soft tissue surgery and dental composite curing, unfortunately, have not yet been realized clinically. These include replacement of the dental drill with a laser, laser dental decay prevention, and laser decay detection. The essential question is whether a laser can provide equal or improved treatment over conventional care. Safe use of lasers also must be the underlying goal of proposed or future laser therapy. With the availability and future development of different laser wavelengths and methods of pulsing, much interest is developing in this growing field. This article reviews the role of lasers in dentistry since the early 1960s, summarizes some research reports from the last few years, and proposes what the authors feel the future may hold for lasers in dentistry.

Adult↗
PubMed1995

Histomorphometric analysis of iliac crest bone biopsies in placebo-treated versus fluoride-treated subjects.

In a 4-year controlled, prospective trial, histomorphometric analysis was used to compare the tissue-level skeletal effects of fluoride therapy in 43 postmenopausal women (75 mg NaF/day) with those of 35 matching placebo subjects; all subjects received 1500 mg/day elemental calcium supplement. In addition to an initial, baseline biopsy, a second biopsy was obtained after 6, 18, 30 or 48 months. Measurements were made on a third biopsy obtained from 8 subjects following at least 72 months of fluoride therapy. The change in cancellous bone volume or trabecular thickness in fluoride-treated subjects was not different from a change in placebo-treated subjects. However, paired analysis in the fluoride-treated subjects indicated that bone volume was increased between the first and second biopsies (p < 0.005). Both osteoid length and width were significantly increased in fluoride compared with placebo subjects; however, only the osteoid surface increased linearly (r = 0.63, p < 0.001). The mineral apposition rate and relative tetracycline-covered bone surface were not different between fluoride and placebo treatment, although they were decreased in both groups in the second biopsy. The tetracycline-covered bone surface returned to normal in the third biopsy. Definitive evidence for osteomalacia is a prolonged mineralization lag time, which following fluoride treatment was found to be increased 9-fold in the second biopsy and 4-fold in the third biopsy. Further evidence for osteomalacia was increased osteoid thickness by 6 months, evidence of focal areas of interstitial mineralization defects, and broad tetracycline labels of low fluorescence intensity. In the third biopsies, osteoclastic resorption was observed beneath osteoid seams. Fluoride therapy increased the cortical width compared with placebo treatment (p < 0.02), and increased the osteoid surface in Haversian canals, but did not change the osteoid width, resorption surface or cortical porosity. After an initial rise, serum fluoride levels remained constant, and the urine values fell slightly. The bone fluoride concentration rose throughout the treatment period, and was correlated with the change in osteoid-covered bone surface (r = 0.56, p < 0.001). Although we found definitive evidence for osteomalacia, the cause of the osteomalacia was not determined in this study. On the other hand, the presence of bone resorption beneath unmineralized osteoid and of osteocyte halos is suggestive of hyperparathyroidism. Thus, it is possible that the strong stimulus for bone formation brought about by fluoride therapy resulted in relative calcium deficiency.

Aged↗
PubMed1995

Effects of sodium bicarbonate dentifrices on the levels of cariogenic bacteria in human saliva.

This investigation evaluated the efficacy of two bicarbonate-containing dentifrices (one with fluoride and one without) against one placebo dentifrice (containing neither fluoride nor bicarbonate) in vivo in a panel of human volunteers to determine whether or not sodium bicarbonate would affect salivary mutans streptococci and lactobacilli. Ten caries-inactive adults were divided randomly into three groups, each of which was exposed to all three dentifrices, in a crossover manner, during three 4-week test periods. Saliva samples were taken at 1-week intervals. Samples were stored on ice, and microbiological analyses were conducted. The statistical analyses showed that, over a 4-week period, there was a statistically significant (p < 0.05) reduction in numbers of mutans streptococci with the two bicarbonate dentifrices as compared with the placebo dentifrice. Although not statistically significant, a similar trend was observed with lactobacilli. Longer-term, large-scale studies need to be conducted to investigate the possible mechanisms of action of sodium bicarbonate on these organisms and to relate the results to possible cariostatic effects in humans.

Adult↗
PubMed1995

Light deposition in dental hard tissue and simulated thermal response.

Near-IR (approximately 1 micron) lasers are presently used for a variety of intra-oral applications including dental hard tissue ablation, although the light intensity distribution and subsequent heating of the hard tissue are still poorly understood. This paper presents a detailed numerical study of the scattered light intensity distribution along with the corresponding predicted thermal response. The calculations are based on recently published scattering and absorption data for dental hard tissue around 1 micron. Our simulations indicate strongly enhanced energy deposition and concomitant heating near the dentino-enamel junction (DEJ), mainly due to the higher absorption in dentin. We predict from 10 to 20 times higher internal temperatures near the DEJ compared with the surface. For example, for 50-ms pulses of 5-J energy on a 3-mm-diameter spot (approximately 1 kW/cm2 or approximately 50 J/cm2), one can expect internal temperatures near the DEJ in excess of 100 degrees C. Elevated temperatures are predicted to extend far into the dentin, endangering the vitality of the pulp several millimeters below the surface. Our results are compared with published experimental data taken under similar conditions and are found to be in good general agreement. The results of this study do not contradict recently reported ablation of dentin with Nd:YAG laser radiation by contact fiber probes. In this case, the irradiation intensities are 3 to 4 orders of magnitude higher, so plasma formation and plasma shielding of the interior of the tooth are likely.

Absorption↗
PubMed1995

Scanning electron microscope observations of CO2 laser effects on dental enamel.

Studies of the effects of carbon dioxide (CO2) lasers on dental enamel have demonstrated that surface changes can be produced at low fluences (< 10 J/cm2) if wavelengths are used which are efficiently absorbed by the hard tissues. In this study, scanning electron microscopy (SEM) was used to characterize the wavelength dependence of surface changes in dental enamel after exposure to an extensive range of CO2 laser conditions. Bovine and human enamel were irradiated by a tunable, pulsed CO2 laser (9.3, 9.6, 10.3, 10.6 microns), with 5, 25, or 100 pulses, at absorbed fluences of 2, 5, 10, or 20 J/cm2, and pulse widths of 50, 100, 200, 500 microseconds. SEM micrographs revealed evidence of melting, crystal fusion, and exfoliation in a wavelength-dependent manner. Crystal fusion occurred at absorbed fluences as low as 5 J/cm2 per pulse at 9.3, 9.6, and 10.3 microns, in contrast to no crystal fusion at 10.6 microns (< or = 20 J/cm2). Longer pulses at constant fluence conditions decreased the extent of surface melting and crystal fusion. The total number of laser pulses delivered to the tissue did not significantly affect surface changes as long as a minimum of 5 to 10 pulses was used. Within the four easily accessible wavelengths of the CO2 laser, there are dramatic differences in the observed surface changes of dental hard tissue.

Animals↗
PubMed1995

Anticaries efficacy of an improved stannous fluoride toothpaste.

A series of laboratory and animal studies were conducted to confirm the anticaries potential of a new, stabilized stannous fluoride (SnF2) dentifrice relative to clinically proven SnF2 controls. Included in this series of assessments were fluoride uptake into demineralized human enamel, remineralization/inhibition of demineralization for both human enamel and roots, and animal caries studies. Each of these studies demonstrate the new, stabilized SnF2 dentifrice (Crest Gum Care toothpaste) is effective at inhibiting and reversing the caries process. These data confirm that this new dentifrice, formulated with a combination of SnF2, and hydrated silica, is predicted to be highly effective against caries. These tests predict that this new stabilized SnF2 dentifrice (Crest Gum Care toothpaste) provides a level of anticaries activity that is equivalent to Crest Regular toothpaste, a sodium fluoride (NaF)/silica product. The data suggest that this new formulation provides enhanced anticaries efficacy relative to previous, unstabilized SnF2 formulations as a result of improved fluoride bioavailability.

Analysis of Variance↗
PubMed1994

Proton-induced physicochemical calcium release from ceramic apatite disks.

When bone is cultured in acid medium there is net calcium efflux (JCa) and proton influx (JH) relative to the mineral. The acid medium appears to induce physicochemical mineral dissolution as well as cell-mediated bone resorption. To determine the independent effect of acid medium on physicochemical dissolution, we utilized cell-free synthetic ceramic apatite (CAP) disks, which contain carbonate (5.5%) in an apatite structure chemically similar to mammalian bone. CAP disks were cultured in control (Ctl, pH approximately equal to 7.44) or acid (Met, pH approximately equal to 7.11) medium for 48 h and compared to similarly treated neonatal (4-6 days old) mouse calvariae. Medium was changed and analyzed at 3, 24, and 48 h. At 3, 24, and 48 h there was significantly greater JCa from the CAP disks and calvariae incubated in Met compared to Ctl; over the entire 48 h time period there was a greater progressive increase in JCa from the CAP disks than the calvariae incubated in Met. There was no significant JCa at 3, 24, or 48 h from CAP disks or calvariae incubated in Ctl. At 3 h there was significantly greater JH into the CAP disks and calvariae incubated in Met compared to Ctl; JH was greater into the CAP disks than the calvariae. Utilizing a synthetic model of bone mineral we demonstrated that acid medium induces physicochemical calcium efflux and proton influx relative to the mineral.

Animals↗
PubMed1994

Zinc ions in synthetic carbonated hydroxyapatites.

Carbonated hydroxyapatites were synthesized at pH 7.0 and 9.0 with a carbonate content up to 9.2%, in the presence of Zn2+ ions. The uptake of Zn was found to be proportional to the amount of Zn added at precipitation. Chemical, lattice constant, microprobe and thermal analyses indicate incorporation of Zn into the apatite lattice.

Carbonates↗
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↗
PubMed1994

Cariogenic potential of foods. II. Relationship of food composition, plaque microbial counts, and salivary parameters to caries in the rat model.

A series of rat caries experiments was carried out to test the relative cariogenic potential and to identify the major carcinogenic elements of 22 popular snack foods. Parameters that were measured included rat caries, number of cariogenic bacteria in plaque, salivary parameters including flow rate, buffering capacity, total protein, lysozyme and amylase content, and composition of test foods including protein, fat, phosphorus, calcium, fluoride, galactose, glucose, total reducing sugar, sucrose, and starch. Many interesting relationships were observed between food components, numbers of plaque bacteria, salivary components, and specific types of carious lesions. Protein, fat, and phosphorus in foods were all associated with inhibition of both sulcal and buccolingual (smooth-surface) caries. Food fluoride was associated with inhibition of buccolingual caries, whereas calcium was related to inhibition of sulcal caries. Glucose, reducing sugar, and sucrose in foods were all related to promotion of both sulcal and smooth-surface caries. The numbers of Streptococcus sobrinus in plaque were associated with promotion of smooth-surface caries only, whereas lactobacilli, non-mutans bacteria, and total viable flora were related to promotion of both smooth-surface and sulcal caries. The salivary flow rate was associated with inhibition of both buccolingual and sulcal caries. Salivary buffering capacity (at pH 7) and salivary lysozyme delivery were associated with inhibition of number and severity of sulcal caries, while the salivary amylase content was related to the promotion of the number of sulcal lesions.

Amylases↗
PubMed1994

Fluoride, remineralization and root caries.

This paper reviews the probable mechanism of dental caries and the role of fluoride in the inhibition or reversal of that process. The initial stages of root caries are comparable to enamel caries, being the acid dissolution of mineral resulting from acids generated by bacterial metabolism. The fermentation of carbohydrates by oral bacteria including mutans streptococci and lactobacilli initiate the root caries process, removing mineral from among the organic matrix which is primarily composed of collagen. Subsequent to this demineralization, the organic material can be further broken down by bacterial enzymes. Fluoride inhibits mineral loss during the acid dissolution process and enhances remineralization in a similar manner to that which occurs in dental enamel.

Bacteria↗
PubMed1993

A critical review of the relative anticaries efficacy of sodium fluoride and sodium monofluorophosphate dentifrices.

While there is broad consensus in the research community that fluoride dentifrices provide important anticaries benefits, debate still remains as to the most efficient form of fluoride used in toothpastes. Recently, the authors of this paper collaborated as part of a scientific advisory group whose objective was to comprehensively review all clinical information available comparing the anticaries efficacy of the two agents most widely used in fluoridated toothpastes, sodium fluoride (NaF) and sodium monofluorophosphate (SMFP). This review included a detailed analysis of each published study pertinent to the question, a comprehensive meta-analysis of all available clinical findings, and an epidemiological assessment of how anticaries benefits of dentifrices may be anticipated to propagate with time. Overall, the use of meta-analysis of head-to-head clinical comparisons between the two fluoride-active systems was found to be the most valid means for comparing the relative efficacy of NaF and SMFP dentifrices. Results of this analysis demonstrated that NaF was significantly more effective than SMFP in preventing caries (p < 0.01). While the numerical difference in efficacy between NaF and SMFP measured between 5 and 10% (total DMFS) over a 2- to 3-year clinical period, this could be expected, on theoretical grounds, to propagate to substantially larger differences (e.g. 10-20%) over 10-20 years. Hence, the difference in efficacy between these two actives was judged to be clinically important as well as statistically significant. Based upon these findings the authors recommend that NaF be used as the active system in fluoridated dentifrices whenever practically feasible. However, the authors caution that this recommendation pertains to the formulation of NaF in highly compatible abrasive systems, which must be demonstrated by critical evaluation of ionic fluoride within formulations for stability, availability and bioavailability. One additional recommendation emanating from this review is that important improvements must be made in the design, execution and reporting of future caries clinical trials in order to bring these important methods up to scientifically acceptable standards.

Adolescent↗
PubMed1993

Effect of salivary components on dissolution rates of carbonated apatites.

Salivary pellicle has been reported to retard the acid-induced demineralization of dental enamel. However, this effect has not been quantified, nor has the direct protective effect of pellicle on carbonated apatite dissolution been elucidated. We have developed a model capable of further studying these questions. Well-characterized synthetic ceramic carbonated apatite discs were pretreated with parotid or whole salivary secretions for 18 h or 7 days and then challenged with 0.1 mol/l acetate, pH 5.0, in a dissolution apparatus. Surface dissolution rates were compared to those from the same carbonated apatites with no saliva pretreatment. Pellicles formed from whole and parotid saliva in vitro and whole saliva in vivo were capable of reducing surface dissolution rates of ceramic carbonated apatites by up to 83% but the degree of this reduction was dependent on the type of saliva and the conditions of pretreatment.

Adsorption↗
PubMed1993

Caries risk assessment by a cross-sectional discrimination model.

Although the prevalence of dental caries is continuing to decline, it still affects a majority of the US population and can be a serious problem for those afflicted. The objective of this project was to develop and perfect a model for assessment of risk of dental caries onset in children. In the first study, reported herein, a set of clinical, microbiological, biochemical, and socio-demographic variables was identified that distinguished, with an acceptable level of sensitivity and specificity, between children who had no previous caries experience and children who had high caries levels. A total of 313 children--age 12-15 years, 140 from a fluoridated community and 173 from a fluoride-deficient community--was selected on the basis of previous caries experience, either zero DMFS or high DMFS (> or = 6 in the fluoridated or > or = 8 in the fluoride-deficient community). Clinical exams for DMFS, dental fluorosis, and plaque were conducted. Stimulated whole saliva was collected for analysis of mutans streptococci, lactobacilli, total viable flora, and fluoride concentration. A questionnaire was used for collection of demographic data as well as information on prior fluoride exposure, dietary habits, and oral hygiene practices. By means of discriminant analyses, with use of seven key clinical and laboratory variables, it was possible for zero-DMFS subjects to e classified correctly (specificity) in 77.6% of cases in the fluoridated community and in 86.1% of cases in the fluoride-deficient community. High-caries subjects were classified as such (sensitivity) in 79.3% and 88.1% of cases, respectively.

Adolescent↗
PubMed1993

Caries risk assessment in a longitudinal discrimination study.

Our objective was to develop and perfect a model for the assessment of risk of dental caries onset in children. Even though dental caries prevalence in children is continuing to decline, there is still a significant minority for whom it is a problem. In this study, we sought to ascertain whether a set of variables selected in a previous cross-sectional study could be used to differentiate between caries-free six-year-olds who would or would not subsequently present with clinically-detectable caries. A total of 472 caries-free six-year-olds--286 from a fluoridated community and 186 from a fluoride-deficient community--was selected. Clinical examinations for DMFS, dental fluorosis, and plaque were conducted. Stimulated whole saliva was collected for analysis of mutants streptococci, lactobacilli, total viable flora, and fluoride, calcium, and phosphate concentrations. A questionnaire was used for collection of demographic data as well as information on prior fluoride exposure, dietary habits, and oral hygiene practices. By means of linear discriminant analyses, it was possible to predict correctly which children would develop caries within six to 12 months (sensitivity) in 82.8% of cases and which children would not develop caries during that period (specificity) in 82.4% of cases.

Apatites↗