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PubMedDate not supplied

Effect of fluoride-releasing filling materials on underlying dentinal lesions in vitro.

Fluoride-releasing materials placed over carious tissue are assumed to enhance remineralisation of the underlying lesion. This remineralisation, however, also depends on the availability of calcium and phosphate, which may be supplied by the pulpal fluid. The aim of this study was to measure the fluoride release of glass ionomer cements (GICs) into underlying dentin and to measure the effect of the released fluoride on the remineralisation of the underlying dentinal lesions using transversal microradiography. Discs of fluoride-releasing GIC were placed on top of dentinal lesions in an in vitro model. The discs and the dentin slabs were covered completely by a protective layer of nail varnish, leaving only the pulpal side of the dentin slab open, and hence the dentinal tubules as the pathway for the incubation fluid to the GIC disc. Specimens were incubated in a remineralisation buffer. The materials tested were a conventional GIC, an experimental GIC that was designed to have a high fluoride release, and an inert material. Fluoride was found to penetrate through the dentin slab into the surrounding fluid. Fluoride uptake from the experimental GIC was higher than from the conventional GIC. Mineral content-depth profiles after 10 weeks' remineralisation revealed that in the outer 30 microm of the lesion a higher mineral deposition occurred for the experimental GIC than in both other groups. No differences in the overall change of integrated mineral loss were found for the tested materials. We conclude that high fluoride release from filling materials only results in superficially increased remineralisation of underlying demineralised dentin.

Analysis of Variance↗

PubMed2006

The effect of lesion characteristics at baseline on subsequent de- and remineralisation behaviour.

The aim was to study the effect of lesion characteristics at baseline on subsequent de- and remineralisation behaviour. Artificial lesions used during in vitro and intra-oral studies exhibit an increasing tendency toward net remineralisation with increasing integrated mineral loss at baseline (DeltaZ(base)). Proposed explanations include: (i) small lesions may be more vulnerable to demineralisation, and (ii) large lesions may be more difficult to remineralise. To evaluate these hypotheses, subsurface lesions were created in numerous blocks of human and bovine enamel, with a range of depths and DeltaZ(base), measured by microradiography. One group of lesions was further demineralised, a second group remineralised, and subsequently, both groups re-analysed. Under demineralising conditions, there was a marked decrease in further mineral loss with increasing DeltaZ(base). Under remineralising conditions lesions gained mineral in proportion to DeltaZ(base). The decrease in demineralisation of lesions with larger DeltaZ(base) may be partially a result of decreased intrinsic solubility through modified chemical composition, e.g. loss of magnesium, carbonate etc. The results may explain the tendency toward net remineralisation with increasing DeltaZ(base) in pH-cycling regimes.

Acids↗

PubMed1981

Radioisotopic and morphometric evaluation of the effects of beta-aminopropionitrile on chick bone matrix formation and its mineralization.

Bones from 2-week-old chicks, fed a diet containing 0.05% beta-aminopropionitrile (beta-APN), were studied for 3H-tetracycline and 3H-proline incorporation at 7, 14 and 21 days of the experiment. Liquid scintillation counts showed a comparable amount of 3H-proline incorporation in the controls and experimentals. However, the incorporation of 3H-tetracycline was significantly lower in experimentals at all intervals. Fluorescent microscopy after cold tetracycline injections at similar intervals showed a comparable amount of linear bone apposition in controls and beta-APN-fed chicks. The bone ash content in beta-APN-fed chicks was lower at all intervals whereas the serum calcium level was similar to the controls. Microradiography showed that cortical and marrow areas, in cross sections, were not significantly different in the controls and beta-APN-fed chicks. On the basis of these data it is suggested that beta-APN at the dose used does not inhibit the bone matrix synthesis but inhibits its mineralization.

Animals↗

PubMed1988

The effect of X-ray irradiation on the demineralization of bovine dental enamel. A constant composition study.

In this study the effect of X-ray irradiation on demineralization of bovine dental enamel in vitro was investigated. Enamel specimens were irradiated with 72 Gy and subsequently demineralized (140 h) under reproducible constant composition conditions at pH = 5 in the presence of methylhydroxydiphosphonate (MHDP). Microhardness measurements after demineralization without MHDP showed significant differences (p less than 0.001) between irradiated and nonirradiated enamel specimens; no significant differences were found in the presence of MHDP. Quantitative microradiography showed that both mineral loss and lesion depth were significantly lower (p less than 0.001) for the irradiated enamel specimens compared with the nonirradiated ones. Surface layer formation was observed in irradiated enamel demineralized in a solution without MHDP. It was shown that X-ray irradiation decreased the enamel acid solubility in vitro.

Animals↗

PubMed1989

Effect of topical F- solutions on caries-like lesions in root surfaces.

Topical F- solutions, NaF, SnF2, TiF4, or Fe-Al-NaF, were applied to root surfaces to examine the effect on caries-like lesions produced in vitro. Extracted premolars were treated with a solution for 10 min prior to a 20-day period in acid gel. The lesions were studied by microradiography and light microscopy, and concentration profiles of 12 elements were determined by secondary ion mass spectrometry. The results indicated that the solutions retarded the development of lesions. The greatest effect was obtained with TiF4 and SnF2 solutions. Element analyses revealed that high concentrations of F (up to 3.5%) accumulated in the outer third of the lesion and that SnF2 and TiF4 formed depots in the cementum, although both Sn and Ti also penetrated the lesion. NaF had a weaker effect on lesion formation, but induced a high F concentration in the demineralized zones. The Fe-Al-F solution affected the lesion only marginally and deposited a relatively low F concentration in the lesion, although Fe and Al penetration and depot formation were noted.

Adolescent↗

PubMed1990

Enamel and dentin fluoride levels and fluorosis following single fluoride doses: a nuclear microprobe study.

Female rats were given single intraperitoneal doses of fluoride (F) (0, 4, 7, or 14 mg F/kg body weight). Plasma F levels returned to predose values within 24 h. Incisors from animals killed 35 or 70 days after the F doses had been given were analyzed for mineralization defects by microradiography, and for F and P concentrations by nuclear microprobe. At 35 days, all F-injected rats had enamel fluorosis. At 70 days, by which time the incisors would have been renewed nearly twice, fluorosis was still evident in the 14 mg/kg body weight group. The enamel and dentin F concentrations at each time point were proportional to the administered F doses that had been given weeks earlier. The F concentrations at 35 days were similar to those found at 70 days. The results support the hypothesis that, following pulse loading, F can be mobilized from the bone adjacent to the enamel organ and result in local F concentrations sufficiently large to adversely affect amelogenesis.

Animals↗

PubMed1990

Remineralization of human dentine in vitro.

In this paper the in vitro remineralization of human dentine with 0, 0.5, 2 and 10 ppm F in the remineralization solution is presented and analyzed by microradiography. Furthermore, the remineralization data of human and bovine dentine are quantitatively compared. The main results of this paper are: (1) the efficacy of human (and bovine) remineralization is about proportional to the square root of the F level in the remineralizing solution, and (2) the amount of mineral effectively deposited in the dentine is most likely controlled by the diffusion of fluoride into the tissue. This study shows furthermore that although numerical differences exist in the remineralization of human and bovine dentine, the general remineralization behaviour is quite similar. The presence of F- in the parts per million range is essential for the remineralization efficacy in vitro and also for the 'overremineralization' of the outer dentine surface.

Adolescent↗

PubMed1991

Demineralization of human dentine compared with enamel in a pH-cycling apparatus with a constant composition during de- and remineralization periods.

A comparison was made between the demineralization of enamel and dentine with and without abraded surfaces. This was done in a pH-cycling experiment for different demineralization/remineralization ratios--in the range from 1:1 to 1:4--and for different fluoride additions (up to 2 ppm) in solution. A new automatic pH-cycling system, in which the de- and remineralization solutions have a constant composition during the de- and remineralization cycles, was used to create mineral loss in human dentine and enamel. Changes in mineral content were monitored by means of longitudinal microradiography. A linear correlation was found between the amount of mineral lost and the total demineralization time for both dentine and enamel. The demineralization rates were comparable for abraded enamel and dentine and for polished enamel and dentine, and this rate was roughly doubled by the removal of the outer surface for both tissues. This showed that the presence of the outer surface is equally important to dentine and enamel. Under the pH-cycling conditions used, a logarithmic relation was found between the addition of fluoride and the decrease in demineralization for both enamel and dentine. The inhibitory effect of fluoride on demineralization was most pronounced on abraded enamel, followed by pumice-polished enamel, abraded dentine and pumice-polished dentine. About 2 ppm fluoride was needed under the conditions used to stop enamel demineralization completely; in the case of dentine, however, this amount of added fluoride did not inhibit demineralization.

Analysis of Variance↗

PubMed1992

The influence of various amphiphilic phosphates on in vitro caries lesion formation in human dental enamel.

Some newly designed surface-active phosphates were investigated with respect to their capacity to inhibit caries lesion formation in vitro. On the labial or buccal surfaces of sound human third molars, windows were prepared for investigation. One half of each window was treated with the test compound at pH values of 7.5, 5.5, or 3.5. The other half served as a control. Both halves were demineralized and the generated caries lesions in both parts were compared by means of quantitative microradiography. Mono-, bis- and trisphosphates differed only marginally in their effect on the demineralization. The compounds diminished the demineralization down to 30% of that of untreated enamel. Per molecule at least one long alkyl chain (more than 12 C atoms) was required for achieving decreased demineralization, indicating the importance of a low surface tension. The results suggest that some of the tested compounds have promising properties for their use as anticaries agents, especially when applied in combination with fluoride.

Dental Caries↗

PubMed1992

Secondary caries in situ around fluoride-releasing light-curing composites: a quantitative model investigation on four materials with a fluoride content between 0 and 26 vol%.

In the literature, secondary caries around composite restorations is reported often. Fluoridated composites are therefore interesting materials because they might reduce or inhibit secondary caries. In this article an in situ model investigation is presented in which the effect of F-releasing composites on enamel demineralisation around an artificial gap of 200 microns width was quantified after 1 month. The fluoride content of the composites varied between 0 and 26 vol%. The beneficial effect of the fluoride released was larger in the gap than at the outer enamel surface. In the gap, all fluoridated composites reduced the enamel demineralisation statistically significantly with respect to the non-fluoridated control. Microradiography showed a reduction of lesion depth values of 27-45%, and a reduction of mineral loss values of 25-56%. At the outer enamel surface next to the artificial gap, a beneficial fluoridation effect was measurable only near the most fluoridated composite. The results indicate that fluoridated composites may play a role in the future prevention of secondary caries.

Acrylic Resins↗

PubMed1992

Effects of fluoride and methanehydroxydiphosphate on enamel and on dentine demineralization.

The aim of this article was to investigate the effects of methanehydroxydiphosphonate (MHDP) and fluoride (F) separately and combined, on the demineralization process in enamel and in dentine under constant composition conditions. The demineralization was carried out in solutions containing 3 mM calcium, 3 mM phosphate, pH = 5.0, and either 6 microM MHDP, 12 microM F or 6 microM MHDP and 12 microM F. After demineralization periods (t) between 24 and 140 h, the lesion depth l and the mineral loss delta Z were measured by transverse microradiography of the enamel and dentine specimens. The amount of mineral lost during demineralization averaged over the lesion depth, R = delta Z/l, was calculated. R approximately 17 vol% for both enamel and dentine, both delta Z and l being greater for dentine than for enamel by approximately the same factor. The results show that under the same conditions dentine is attacked much more strongly than enamel. The lesion progress with time is quite different for the two tissues: in enamel the lesion depth progresses als l3 = alpha t + beta, in dentine as l2 = alpha't + beta'. The slopes alpha and alpha' decrease in the order MHDP > F > MHDP+F. In enamel the combined inhibitor effect is only slightly larger than the effect of F alone; in dentine the inhibiting effects of F and MHDP are approximately additive. The inhibitor interactions can be described by the Langmuir adsorption theory.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗

PubMed1997

An in situ interproximal model for studying the effect of fluoride on enamel.

This crossover study determined the ability of an interproximal, intra-oral model to demonstrate a fluoride dose response to 0-, 250- and 1,100-ppm fluoride (sodium fluoride) dentifrices with respect to fluoride uptake into, and remineralization of, incipient subsurface enamel lesions. Following a 1 week 'lead in' period during which 30 panelists were randomly assigned to use one of the products, two enamel specimens with artificial carious lesions were mounted into a specially designed functional partial denture worn by each panelist. Panelists continued to brush three times daily with their test dentifrice for 4 weeks, after which the specimens were removed and analyzed for fluoride uptake and remineralization. The procedure was repeated until each panelist had followed all three treatment regimens. Fluoride analyses were performed using a microdrill biopsy technique, and mineral content changes were determined by transverse microradiography. Fluoride uptake data were significantly different (p < 0.01) for all three products with the effect of 1,100 ppm F > 250 ppm F > placebo. The 1,100 ppm F dentifrice also effected significantly greater remineralization (p < 0.01) than did the 250-ppm-F or placebo dentifrices. Relative efficacy of the three fluoride dentifrices tested in this study was similar to that established in a clinical trial, and, therefore, supports the use of this model for in situ studies of the effects of fluoride-containing products on enamel lesions.

Adult↗

PubMed1990

Subcapsular zones of discontinuity in the human lens.

Zones of discontinuity parallel to the lens surface can be seen in the normal lens on slitlamp examination. These zones have been suggested to be surfaces at which the refractive index changes from one value to another. Normal lenses from tumor eyes have been examined by quantitative microradiography. The protein concentrations has been determined in thin sections from the anterior cortex. These measurements revealed jumps in the protein concentration at the same location as the zones of discontinuity. The magnitude of these jumps corresponds to changes of the refractive index that can explain the increased scatter of light in the zones of discontinuity.

Crystallins↗

PubMed1994

Diffuse calcification in human coronary arteries. Association of osteopontin with atherosclerosis.

Coronary atherosclerosis is frequently associated with calcification of arterial plaque. To understand the mechanisms responsible for the formation of atherosclerotic calcification, we examined human coronary arteries for the presence and extent of mineral. In sections stained specifically for mineral, staining was diffuse and present in all atherosclerotic plaques. Hydroxyapatite was not detected in normal coronary artery sections. Distribution of hydroxyapatite coincided with a similar distribution of calcium detected by a radiodense pattern using contact microradiography of the same sections before cytochemical staining. By energy-dispersive x-ray microanalysis, the chemical composition of calcified sites was identical to hydroxyapatite (Ca10[PO4]6[OH]2), the major inorganic component of bone. Osteopontin is a phosphorylated glycoprotein with known involvement in the formation and calcification of bone and is regulated by local cytokines. Human coronary artery segments (14 normal and 34 atherosclerotic) obtained at autopsy were evaluated immunohistochemically using polyclonal antibodies generated against human osteopontin. Immunohistochemistry for osteopontin indicated intense, highly specific staining in the outer margins of all diseased segments at each calcification front; staining was evident throughout the entire plaque. Conversely, arterial segments free of atheroma and calcification and sections treated with nonimmune serum had no evidence of positive staining. Osteopontin, a protein involved in mineralization is specifically associated with calcific coronary atheroma and may play an important role in the onset and progression of this disease in human coronary arteries. The deposition of noncollagenous proteins such as osteopontin may regulate the presence or absence of calcification and ultimately alter vessel compliance.

Adult↗

PubMed1990

Bronchiolar morphology after systemic arterial interruption.

To assess ischemic lesions as a factor in obliterative bronchiolitis after lung transplantation, the authors severed the left bronchial arteries of 15 dogs, together with the left stem bronchus, the latter being immediately reanostomosed. They examined the bronchioles at weekly interfals up to three and a half months. On the week chosen each dog was anesthetized, totally heparinized, and exsanguino-perfused with saline. Just after heart arrest, the thoracic aorta was injected with a barium solution until this white medium appeared in the bronchial arteries. The heart-lung blocs were excised en bloc, submitted to soft-tissue x ray, fixed, and then sliced to 1 cm. Corresponding right and left 5-mm-thick samples of these slices were prepared for contact microradiography followed by histologic 5-to-20-micron-thick, stained, correlated specimens. For two weeks the left bronchial arteries remained empty, but there was no necrosis or edema. Between two and four weeks barium solution appeared in the bronchial arteries, and the bronchiolar epithelium had become multistratified. Later the left bronchiangiogram became similar to the right, but there were more folds of the mucosa and a little submucosal fibrosis. These studies provide proof that no significant ischemic lesions occurred during repermeation of the bronchiolar vascular bed. Ischemia, if existent, is not a significant factor in obliterative bronchiolitis.

Anastomosis, Surgical↗

PubMed2001

Remineralization of caries lesions extending into dentin.

Remineralization is one aspect of the overall process of tooth decay. However, it is primarily studied in shallow lesions. The aim of this study was to explore whether caries lesions in enamel and extending into the dentin can be remineralized. A single-section model was developed for the longitudinal and non-destructive monitoring of changes in enamel and dentin. Lesions at least 200 microm into dentin were formed in undersaturated acetate buffers. Next, the lesions were divided into groups (three treatment and one control) and remineralized. The treatments were: weekly immersion in 1,000 ppm fluoride, single treatment with methanehydroxybisphosphonate, and a constant level of 1 ppm fluoride. De- and remineralization was assessed by transverse microradiography. Remineralization was observed in enamel, but also in dentin, indicating that, deep into dentin, the pores become supersaturated to apatite formation. Treatments affected remineralization only in the outer part of enamel. Both findings are explained by a relatively fast diffusion of mineral ions, with precipitation being rate-limiting. The results suggest that dentin remineralization, underneath enamel, can be achieved and could possibly be used in clinical treatment strategies.

Analysis of Variance↗

PubMed2001

Remineralization of enamel subsurface lesions by sugar-free chewing gum containing casein phosphopeptide-amorphous calcium phosphate.

Casein phosphopeptide-amorphous calcium phosphate nanocomplexes (CPP-ACP) exhibit anticariogenic potential in laboratory, animal, and human in situ experiments. The aim of this study was to determine the ability of CPP-ACP in sugar-free chewing gum to remineralize enamel subsurface lesions in a human in situ model. Thirty subjects in randomized, cross-over, double-blind studies wore removable palatal appliances with six human-enamel half-slabs inset containing sub-surface demineralized lesions. The appliances were inserted immediately before gum-chewing for 20 min and then retained for another 20 min. This was performed four times per day for 14 days. At the completion of each treatment, the enamel half-slabs were paired with their respective demineralized control half-slabs, embedded, sectioned, and subjected to microradiography and densitometric image analysis, for measurement of the level of remineralization. The addition of CPP-ACP to either sorbitol- or xylitol-based gum resulted in a dose-related increase in enamel remineralization, with 0.19, 10.0, 18.8, and 56.4 mg of CPP-ACP producing an increase in enamel remineralization of 9, 63, 102, and 152%, respectively, relative to the control gum, independent of gum weight or type.

Adult↗

PubMed1987

The prevention of sub-surface demineralization of bovine enamel and change in plaque composition by casein in an intra-oral model.

The ability of bovine milk phosphoprotein (casein) to be incorporated into plaque, prevent enamel sub-surface demineralization, and affect bacterial composition was determined using a modified intra-oral caries model. The intra-oral model consisted of a removable appliance containing a left and right pair of bovine enamel slabs placed to simulate an approximal area. Supragingival plaque was collected and impacted into the left and right inter-enamel spaces. The left side of the appliance was exposed to various sugar and salt solutions, while the right side was exposed to sugar and casein solutions. Sodium caseinate, the major fraction alpha s1-casein, and a tryptic digest of alpha s1-casein (TD-casein) were studied. Sodium caseinate at a level of 2% w/v in a 3% sucrose-3% glucose-salt solution (pH 7.0) prevented sub-surface enamel demineralization over a ten-day period as shown by microradiography and microhardness. Two exposures of a 2% w/v sodium caseinate, alpha s1-casein, or TD-casein solution (pH 7.0) per day prevented sub-surface enamel demineralization caused by six exposures of a 3% sucrose-3% glucose-salt solution per day over a ten-day period. Intact alpha s1-casein and tryptic peptides were shown immunochemically to be incorporated into the inter-enamel plaque. The incorporation of casein and its breakdown in plaque did not produce a significant change in the amount or composition of plaque bacteria. The ability of casein and tryptic peptides to prevent enamel demineralization was related to their incorporation into plaque, thereby increasing plaque calcium phosphate and acid-buffering capacity by the phosphoseryl, histidyl, glutamyl, and aspartyl residues and indirectly through catabolism by plaque bacteria.

Adolescent↗