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Biomedical subjects

J D Featherstone

Publications and source records attributed to J D Featherstone.

At least 73 records · Page 4Linked to original sources
PubMed1988

Quantitative analysis of early in vivo tissue response to synthetic apatite implants.

Studies have shown synthetic calcium phosphates such as hydroxyapatite and beta tricalcium phosphate to be biocompatible in vivo. However, few studies have quantitated histological responses to the implants. The aim of this study was to develop a method for the quantitative assessment of tissue biocompatibility to ceramic materials in vivo and to use this method to compare noncarbonated and carbonated apatite implants. Synthetic sintered apatites of 0, 3, and 6% carbonate by weight were prepared and cut into implants 4 X 4 X 1 mm. These were placed 2 mm into the medial aspect of rat femurs. Following sacrifice at 4 weeks, the femurs were fixed in formalin, demineralized in formic acid, and embedded in glycol methacrylate. Sections were cut on an ultramicrotome set at 1.5 micron and stained with toluidine blue. A point counting technique using standard stereological grids and a low-power microscope was used to measure areas of new bone formation. The width of the connective tissue zone adjacent to muscle was measured using an image analyzer. All implants were well accepted by the host tissues judging from criteria of minimal inflammation and degree of fixation. Results showed an increase in new bone formed in the marrow cavity with increasing carbonate content. This may improve stability of the implant in the host bone, particularly during the initial healing period. A technique which should enable quantitative histological evaluation of different ceramic materials has been developed. The use of this method indicates that further studies are warranted to investigate carbonated apatite as an implant material.

Animals↗
PubMed1988

Crystallographic structure and surface morphology of sintered carbonated apatites.

Densely sintered synthetic hydroxyapatite (HA) is used as an implant material because of its excellent tissue biocompatibility. In order to maximize the biological potential of this calcium phosphate, we have investigated the incorporation of carbonate into HA to make a material which more closely resembles the mineral found in bones and teeth. The aim of the present study was to determine the conditions under which sintered carbonated apatites of specific carbonate content could be produced. The apatites were prepared by heating compressed pellets of precipitated carbonated apatite under a carbon dioxide/steam or nitrogen/steam atmosphere between 825 and 1050 degrees C. The products were analyzed chemically and the surfaces examined by x-ray diffraction, infrared spectroscopy, reflected light microscopy, and scanning electron microscopy. The results showed that carbonate loss during sintering could be reliably predicted, making it possible to produce materials with specific carbonate content, and with specific physical and chemical composition.

Carbonates↗
PubMed1988

Retention of topical fluoride in the mouths of xerostomic subjects.

The total fluoride concentration in unstimulated whole saliva was measured before and at selected intervals after a self-applied 1.1% neutral NaF topical fluoride gel or use of a 0.05% neutral NaF fluoride mouthrinse in both normal individuals and patients with radiation-induced xerostomia. As expected, the gel resulted in higher peak fluoride values than the rinse and was retained in the mouth for longer periods of time in both groups. The xerostomic group expressed a mean oral fluoride concentration of 575 micrograms fluoride per gram of saliva within 1 min after the gel application and 150 micrograms/g following use of the mouthrinse, whereas the normal group exhibited peak concentrations of 112 and 71 micrograms/g, respectively, within 1 min after the same two treatments. The initial high levels of fluoride observed in normal subjects following the gel application decreased rapidly to less than 1 microgram/g within 2 h, whereas fluoride levels in the xerostomic subjects remained elevated above 12 micrograms/g for longer than 2 h. Similarly, following use of the mouthrinse, normal subjects' saliva fluoride levels decreased to less than 1 microgram/g within 1 h, whereas xerostomic subjects' saliva fluoride levels remained above 4 micrograms/g for longer than 2 h.

Adult↗
PubMed1988

Effect of an anticalculus dentifrice on lesion progression under pH cycling conditions in vitro.

The aim of the present study was to examine a sodium fluoride anticalculus dentifrice product containing soluble pyrophosphate for its ability to promote remineralization and/or inhibit demineralization of dental enamel in a pH cycling model in vitro. Enamel crowns with windows were subjected to 14 days of alternating demineralization and remineralization periods at 37 degrees C. Teeth were immersed 5 min daily in one of the test dentifrice systems (1:3 slurry in deionized water) between the demineralization and remineralization cycles. Test dentifrices included (1) sodium fluoride (NaF; 1,100 ppm F)/silica abrasive (Crest) and (2) NaF (1,100 ppm F) with 3.3% soluble pyrophosphate/silica abrasive (Crest Tartar Control). Controls included a placebo dentifrice (silica abrasive) with no added fluoride and a group which received no treatment at all, i.e., demineralization/remineralization only. Overall, both of the NaF dentifrices were very effective in limiting in vitro caries progression and were not significantly different from each other. Inclusion of pyrophosphate in the NaF dentifrice did not affect the net outcome of the cycling demineralization/remineralization processes which is in agreement with recent clinical and in situ studies of these products.

Dental Calculus↗
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↗
PubMed1987

Demineralization and remineralization around orthodontic appliances: an in vivo study.

The presence of clinically detectable areas of decalcification (observable as whitened areas) following the removal of orthodontic appliances is well recognized. The aim of the present study was to determine quantitatively the amount of demineralization and the ability of commercially available products to inhibit or reverse orthodontically related demineralization. Twenty orthodontic patients scheduled to have premolars extracted were randomly divided into four groups--one control and three test groups. The extracted premolars (numbering 58) were bracketed using an acid-etch composite system; each patient was given precise oral hygiene instructions and supplied with a sodium fluoride (1,100 ppm fluoride) dentifrice and an orthodontic toothbrush. The control group brushed only with the supplied dentifrice. In addition to brushing with the dentifrice, those in test group I rinsed once each night with a sodium fluoride (0.05%) mouthrinse; group II received a weekly topical APF treatment (1.2% fluoride); and Group III received a weekly topical APF treatment and rinsed once each night with the sodium fluoride mouthrinse. All premolars were extracted after 1 calendar month. Mineral profiles were determined on cross-sectioned teeth 50 to 75 micron occlusal and cervical to the brackets, directly underneath the brackets, and 500 micron away from the brackets. The control teeth (dentifrice only) demonstrated up to 15% demineralization to a depth of 50 micron. All of the test teeth produced rehardening and/or inhibition of demineralization (P less than 0.01). Those in test group III showed a particularly hard outer layer. The study demonstrated that measurable demineralization occurred around orthodontic appliances after only 1 month and this demineralization can be completely inhibited and/or reversed by the use of commercially available fluoride products.

Dental Bonding↗
PubMed1987

Inhibitory effect of barium on human caries prevalence.

The aim of this investigation was to determine if barium in drinking water, in combination with fluoride, has an effect on caries prevalence in a human population. Children, aged 12-14 yr, were selected from two towns which had a similar socioeconomic and racial balance but one had a barium concentration of 8.0-10.0 ppm in its drinking water and the other a level which was less than 0.03 ppm. The caries prevalence, as mean DMFS, was significantly lower in the high barium town (2.76 +/- 0.82) than in the low barium town (5.14 +/- 0.65). The difference in mottling scores between the two towns was not significant (P = 0.44, chi-square test). This difference in mean DMFS between the high and low barium communities could not be explained by an effect of other covariate factors.

Adolescent↗
PubMed1987

Chemical and physical oral findings in a case of anorexia nervosa and bulimia.

The deleterious effect on enamel of continual acid challenge from regurgitation of gastric contents in bulimic subjects is well documented. No previous reports, however, have been published on chemical and physical measurements of teeth from such subjects, or on the importance of fluoride in maintaining their dentition. Teeth were obtained from a deceased anorexic and bulimic patient. Shortly before death this patient had saliva analyses and in vivo enamel biopsies at our clinic, before and after a 3-week regimen of daily rinsing with 0.05% NaF. After 4 years of daily regurgitation there was an almost normal thickness of the enamel surfaces typically "at risk", i.e. the palatal surfaces of the maxillary anterior teeth, with normal hardness measurements 10 micron away from the outer surface. SEM micrographs showed an irregular topography, with crystalline deposits rich in calcium, phosphate and fluoride. These surfaces were more reactive to uptake of additional fluoride when given as a daily rinse, than the more protected, and therefore, presumed unaffected surfaces. Our findings suggest that frequent and meticulous oral hygiene measures can substantially minimize the erosive effect on tooth enamel of gastric contents in bulimic patients, especially if fluoride products are used regularly.

Adolescent↗
PubMed1986

The structure of (100) defects in carbonated apatite crystallites: a high resolution electron microscope study.

Planar defects parallel to (100) with an approximate [1/400] displacement vector have been identified by high resolution transmission electron microscopy and by micro-electron diffraction in the center of synthetic carbonated apatite crystallites. Similar intergrowths, 0.8-1.5 nm in width, have been observed in dental enamel, dentin and bone apatite crystallites. Four possible structural models of the defect core are proposed to explain these experimental features, and computer-simulated lattice images of the models are compared with the experimental images. Typical defects were consistent with a two-dimensional octacalcium phosphate inclusion, one unit cell thick, embedded in an apatite matrix.

Apatites↗
PubMed1986

Dental caries prevalence in Texas schoolchildren using water supplies with high and low lithium and fluoride.

The effect of lithium (Li) in drinking water on caries prevalence in seven Texas towns was investigated. Children (life-long residents) aged 12-14 years were examined for caries prevalence, as DMFS, in towns with drinking water Li concentrations ranging from 0.0 to 165 micrograms/L and fluoride (F) concentrations ranging from 0.20 to 1.94 mg/L. A significant negative relationship was found between F in drinking water and DMFS. When corrected for the F contribution, Li in water supplies showed a positive correlation with DMFS.

Adolescent↗