fluorapatite and Dental-Caries

Dental caries is a complex disease process that afflicts a large proportion of the world's population, regardless of gender, age and ethnicity, although it does tend to affect more indivduals with a low socioeconomic status to a greater extent. The physicochemical properties of the mineral comprising the tooth surface and subsurface modulate the development, arrestment and remineralization of dental caries. Post-eruption maturation of enamel surfaces and exposed root surfaces is important in order for more susceptible mineral phases to be modified by incorporation of soluble fluoride from the plaque into dental hydroxyapatite. The chemical reactions that occur during acidic conditions when tooth mineral dissolves (critical pH) are determined by the supersaturation of calcium and phosphate within plaque and saliva, as well as if fluoride is present.

Topics: Apatites; Dental Caries; Dental Enamel; Dental Enamel Permeability; Dental Enamel Solubility; Dental Plaque; Durapatite; Humans; Hydrogen-Ion Concentration; Tooth Demineralization; Tooth Remineralization

Dental caries is a complex disease process that afflicts a large proportion of the world, regardless of gender, age and ethnicity, although it does tend to affect more with a low socioeconomic status to a greater extent. Remineralization may be enhanced by providing low levels of calcium and phosphate, in conjunction with minimal amounts of fluoride. It is truly remarkable the difference that a very small amount of fluoride (<1 ppm) has upon demineralization and remineralization. This is because fluoride acts as a catalyst and influences reaction rates with dissolution and transformation of various calcium phosphate mineral phases within tooth structure and resident within plaque adjacent to tooth surfaces. The incorporation of minimal amounts of fluoride into HAP yields FHAP that resists demineralization to similar level as FAP. New and emerging methods have been and are in the process of being developed. These hold great promise for preventing and reversing caries, especially in the one-fifth of the population that accounts for two-thirds of the caries experience. Still, the mainstay in caries prevention and remineralization is frequent exposure to low levels of fluoride. This may be accomplished with fluoridated toothpastes, supplemented with fluoride mouthrinses, CPP-ACP containing chewing gum and application of fluoride varnishes. The role of systemic fluorides appears to be limited and primarily has a topical effect.

Topics: Apatites; Calcium Phosphates; Cariostatic Agents; Dental Caries; Dental Enamel; Dental Enamel Solubility; Fluorides; Humans; Hydrogen-Ion Concentration; Tooth Remineralization

To evaluate the effects of novel casein phosphopeptide (CPP) formulations CPP-amorphous calcium phosphate (CCP- ACP) and CPP-amorphous calcium fluoride phosphate (CPP-ACFP) versus fluoride varnish on the remineralisation of enamel white spot lesions (WSLs) over a 12-week follow-up period.. Double-blind prospective study. Eligibility criteria were patients between 6 and 14 years old and have WSLs on their permanent teeth. We evaluated 786 WSLs. Participants were divided randomly into three groups. Groups A and B were instructed to daily topical application of GC Tooth Mouse (CPP-ACP) or Mi Paste Plus (CPP-ACFP), Group C received a monthly professional application of Duraphat fluoride varnish. WSLs were categorised according to the International Caries Detection and Assessment System (ICDAS II; grades 0-3) and assessed by laser fluorescence (DIAGNOdent) at baseline and at 4, 8 and 12 weeks. Changes in mineralisation before and after treatment were analysed using two-way analysis of variance, with post hoc Bonferroni's non-parametric tests for multiple comparisons.. DIAGNOdent values were significantly reduced in Group B at 4 weeks, and in Groups A and C at 8 weeks. Mean values in Group B were lower than in Groups A and C at 4 weeks, and lower than Group C at 8 weeks. CPP-ACFP appeared to have a specific effect on smooth-surface caries, but no significant effect on caries in pits and fissures.. At 4 weeks, CPP-ACFP is superior to fluoride varnish at remineralising smooth-surface WSLs. CPP-ACP is not superior to fluoride varnish by any of the measures studied.

Topics: Adolescent; Apatites; Caseins; Child; Dental Caries; Double-Blind Method; Female; Fluorides; Humans; Male; Prospective Studies; Tooth Remineralization

White-spot lesions (WSL) might be susceptible to mechanical damage during orthodontic bracket and adhesive removal. The aims of this in-vitro study were to investigate enamel loss on bracket and adhesive removal when the brackets were surrounded by WSL and to determine the effect of remineralizing these lesions with a 1% (w/v) casein phosphopeptide amorphous calcium fluoride phosphate (CPP-ACFP) solution before bracket and adhesive removal.. Precoated metal mandibular incisor brackets were centrally bonded onto polished third molars and WSL produced by exposure to a demineralization buffer for 4, 12, and 30 days (n = 20 per group). Half of the demineralized window was covered with acid-resistant nail varnish, and the specimens were then subjected to remineralization with 1% CPP-ACFP. Brackets and residual adhesive were removed, and enamel damage was assessed by digital photography, profilometry, and scanning electron microscopy. Lesion depth, mineral loss, and remineralization were measured by transverse microradiography.. WSL enamel around the bracket was more susceptible to iatrogenic damage at adhesive removal compared with sound enamel. Remineralization of lesions with 1% CPP-ACFP before adhesive removal significantly (P <0.002) reduced the area and depth of damage.. Remineralizing WSLs with CPP-ACFP before adhesive removal reduced iatrogenic enamel damage.

Topics: Apatites; Caseins; Dental Caries; Dental Cements; Dental Debonding; Dental Enamel; Equipment Design; Humans; Iatrogenic Disease; Image Processing, Computer-Assisted; Materials Testing; Microradiography; Microscopy, Electron, Scanning; Minerals; Orthodontic Brackets; Photography, Dental; Surface Properties; Time Factors; Tooth Demineralization; Tooth Remineralization; Tungsten Compounds

To investigate the effect of different toothpastes either containing 5,000ppm-F, 1,450ppm-F or bioactive glass (BG) with 540ppm-F on artificial root carious lesions (ARCLs).. The crowns of 23 extracted sound teeth were removed leaving their roots only. Subsequently, each root was divided into four parts. A total of 15 sound root dentine (SRD) was left untreated as baseline. The ARCLs were developed for the remaining roots using demineralisation solution (pH-4.8). 15-ARCLs samples were then left untreated. The rest of samples were divided into four groups (n = 15 each) and treated with Group-1(BG with 540ppm-F); Group-2(5000ppm-F); Group-3(1450ppm-F) and Group-4(deionised water). 13-day pH-cycling included using demineralisation solution for 6 h, then placing samples into remineralisation solution (pH-7) for 16 h. Each sample was brushed with the assigned toothpaste twice a day during pH-cycling. Fluoride concentrations at each time point were measured using F-ISE, whilst calcium (Ca. KHN showed significant surface changes for each group (p<0.001). The uptake of Ca. All toothpastes were promising in fluorapatite formation. BG with 540ppm-F toothpaste released more ions (Ca. Toothpaste containing BG with 540ppm-F, 5000ppm-F and 1450ppm-F toothpastes are likely to have a significant impact in reversing and arresting root caries. However, randomised controlled double-blinded clinical trials are required to translate these results into clinical practice.

Topics: Apatites; Cariostatic Agents; Dental Caries; Fluorides; Humans; Phosphorus; Root Caries; Sodium Fluoride; Tooth Remineralization; Toothpastes

Iontophoresis is a noninvasive technique, based on the application of a constant low-intensity electric current to facilitate the release of a variety of drugs, whether ionized or not, through biological membranes. The objective of this research was to evaluate the effect of iontophoresis using different electric current intensities on the uptake of fluoride in dental enamel with artificial caries lesions. In this in vitro operator-blind experiment, bovine enamel blocks (n = 10/group) with caries-like lesions and predetermined surface hardness were randomized into 6 groups: placebo gel without fluoride applied with a current of 0.8 mA (negative control), 2% NaF gel without application of any current, and 2% NaF gel applied with currents of 0.1, 0.2, 0.4 and 0.8 mA. Cathodic iontophoresis was applied for 4 min. The concentration of loosely bound fluoride (calcium fluoride) and firmly bound fluoride (fluorapatite) was determined. The results were analyzed by the nonparametric Kruskal-Wallis and Dunn tests. Iontophoresis at 0.8 mA, combined with the application of fluoridated gel (2% NaF), increased fluoride uptake in enamel with caries-like lesions, as either calcium fluoride or fluorapatite.

Topics: Animals; Apatites; Calcium Fluoride; Cariostatic Agents; Cattle; Dental Caries; Dental Enamel; Disease Models, Animal; Electricity; Fluorides; Hardness; Iontophoresis; Random Allocation; Surface Properties; Treatment Outcome

The recent studies on fluorapatite and hydroxyapatite, in the context of their medical applications, have shown that the former has relatively higher thermal stability and better mechanical properties than the latter. Moreover, the presence of fluoride ions is relevant for protection of teeth from dental caries since they stimulate processes of mineralization and crystallization. In this report, a silver modified fluorapatite (FAP/Ag), considered as a novel biomedical compound, was tested for its bactericidal, fungicidal and cytotoxicity activity. All these features were compared to the impact of pure FAP and were evaluated against the bacteria and fungi strains, which constitute main pathogenic species among orthopedic clinical isolates of implant-associated infections. Generally, considerable increase in the antimicrobial activity was observed when silver modified fluorapatite was compared to the pure material. This was manifested among others by disturbance of cell growth pattern and various deformations in the final cell shape as revealed using atomic force microscopy (AFM). Regarding toxicity nowadays as a major issue in implantation, we additionally examined whether the Ag

Topics: Animals; Apatites; Bacteria; Dental Caries; Fungi; Humans; Mice; Silver

This study aimed to evaluate the effect of fluoridated dentifrice (FD) and mouthwash (FM) under different treatment regimens on root caries (RC) inhibition.. Dual-species biofilms formed by Streptococcus mutans and Lactobacillus casei were grown on the surface of bovine root dentine slabs which were exposed during 3 consecutive days to one of the following treatments: T1-distilled and deionized water 3×/day; T2-FD (1450ppmF) 2×/day; T3-FD 2×/day+FM (226ppmF) 1×/day; T4-FD 3×/day. Viable microorganisms counts were performed after 4 days of biofilm formation. Percentage of surface microhardness change (%SMC), lesion depth (LD; μm), integrated mineral loss (IML; vol%×μm) and the percentages of change (Δ%) in the ratio of fluorapatite (FAp/amide) and hydroxiapatite (HAp/amide) were calculated.. Minor changes were found on microbial counts in response to different treatments (p<0.05). %SMC in T4 was statistically lower compared with T2, but with no significant difference compared with T3. LD of slabs treated with T4 was statistically lower compared with T2 and T3, which were not significantly different between them. No significant differences were found for IML, FAp and HAp among the fluoridated treatments (p>0.05).. The use of FD 3×/day may be more effective than the use of FD 2×/day or the tested association between FD and FM on RC inhibition.

Topics: Adolescent; Adult; Animals; Apatites; Biofilms; Cattle; Dental Caries; Dental Enamel; Dentifrices; Dentin; Fluorides; Humans; Lacticaseibacillus casei; Mouthwashes; Nonprescription Drugs; Root Caries; Sodium Fluoride; Streptococcus mutans; Tooth; Tooth Demineralization; Tooth Root; Young Adult

The aim of this work was to verify the existence of correlation between Raman spectroscopy readings of phosphate apatite (~960 cm-1), fluoridated apatite (~575 cm-1) and organic matrix (~1450 cm-1) levels and Diagnodent® readings at different stages of dental caries in extracted human teeth. The mean peak value of fluorescence in the carious area was recorded and teeth were divided in enamel caries, dentin caries and sound dental structure. After fluorescence readings, Raman spectroscopy was carried out on the same sites. The results showed significant difference (ANOVA, p<0.05) between the fluorescence readings for enamel (16.4 ± 2.3) and dentin (57.6 ± 23.7) on carious teeth. Raman peaks of enamel and dentin revealed that ~575 and ~960 cm-1 peaks were more intense in enamel caries. There was significant negative correlation (p<0.05) between the ~575 and ~960 cm-1 peaks and dentin caries. It may be concluded that the higher the fluorescence detected by Diagnodent the lower the peaks of phosphate apatite and fluoridated apatite. As the early diagnosis of caries is directly related to the identification of changes in the inorganic tooth components, Raman spectroscopy was more sensitive to variations of these components than Diagnodent.

Topics: Analysis of Variance; Apatites; Dental Caries; Dental Enamel; Dentin; Durapatite; Fluorescence; Fluorometry; Humans; Lasers, Semiconductor; Organic Chemicals; Spectrum Analysis, Raman; Statistics, Nonparametric; Vibration

The purpose of this study was to determine the color of white spot lesions.. Human premolars were subjected to a pH cycling to produce artificial caries lesions and classified into groups (n = 10/group): group 1, immersion in deionized water; group 2, pH cycling without fluoride (F) application; group 3, pH cycling with immersion in 1,000 ppm NaF solution; and group 4, pH cycling with immersion in 5,000 ppm NaF solution. CIE L*a*b* color parameters of the tooth were determined using a spectroradiometer at baseline, after demineralization and after pH cycling. The extent of demineralization was evaluated by scanning electron microscopy (SEM) and electron microprobe analysis (EPMA).. Significant degrees of color change (ΔE*) were observed after demineralization (p < 0.05). The changes were mainly due to an increase in lightness (L*) and a decrease in yellowness (b*). F application induced a significantly large ΔE* in group 4 (p < 0.05). The color reversal after remineralization was mostly due to the recovery of L*. SEM and EPMA verified that net mineral gains occurred in the subsurface lesions.. The initially white appearance of enamel caries was a result of changes of L* and b*. F treatment partially restored the color of white spot lesions.. F-driven remineralization induced both mineral gains and esthetic enhancement of artificially produced enamel white spot lesions. The increase of L* and the decrease of b* contributed to the color changes.

Topics: Apatites; Bicuspid; Calcium; Cariostatic Agents; Color; Dental Caries; Dental Enamel; Electron Probe Microanalysis; Humans; Hydrogen-Ion Concentration; Microscopy, Electron, Scanning; Phosphorus; Sodium Fluoride; Spectrum Analysis; Time Factors; Tooth Demineralization; Tooth Remineralization

The present mechanistic in vitro study aimed to investigate dose-response effects of zinc and fluoride on caries lesion remineralization and subsequent protection from demineralization. Artificial caries lesions were created using a methylcellulose acid gel system. Lesions were remineralized for 2 weeks using citrate-containing artificial saliva which was supplemented with zinc (0-153 μmol/l) and fluoride (1.1 or 52.6 μmol/l) in a 7 × 2 factorial design. Lesions were also remineralized in the absence of zinc and citrate, but in the presence of fluoride. After remineralization, all lesions were demineralized for 1 day under identical conditions. Changes in mineral distribution characteristics of caries lesions after remineralization and secondary demineralization were studied using transverse microradiography. At 1.1 μmol/l fluoride, zinc exhibited detrimental effects on remineralization in a dose-response manner and mainly by preventing remineralization near the lesion surface. At 52.6 μmol/l fluoride, zinc retarded remineralization only at the highest concentration tested. Zinc enhanced overall remineralization at 3.8-15.3 μmol/l. At 76.5 and less so at 153 μmol/l, zinc showed extensive remineralization of deeper parts within the lesions at the expense of remineralization near the surface. Citrate did not interfere with remineralization at 1.1 μmol/l fluoride, but enhanced remineralization at 52.6 μmol/l fluoride. Lesions exhibiting preferential remineralization in deeper parts showed higher mineral loss after secondary demineralization, suggesting the formation of more soluble mineral phases during remineralization. In summary, zinc and fluoride showed synergistic effects in enhancing lesion remineralization, however only at elevated fluoride concentrations.

Topics: Animals; Apatites; Calcium Fluoride; Calcium Phosphates; Cariostatic Agents; Cattle; Citric Acid; Dental Caries; Dental Enamel; Dental Enamel Solubility; Dose-Response Relationship, Drug; Drug Synergism; Durapatite; Fluorides; Hydrogen-Ion Concentration; Lactic Acid; Methylcellulose; Microradiography; Minerals; Phosphates; Saliva, Artificial; Tooth Remineralization; Zinc; Zinc Compounds

Some saliva substitutes have been shown to demineralize dentine in vitro. This effect is counteracted by the application of various fluorides. In contrast, remineralizing saliva substitutes might be supported by these treatments, depending on the dynamics during remineralization. The aim of this in vitro study was to evaluate the effects of fluoride mouthrinses or gels in combination with de-/remineralizing saliva substitutes on dentinal subsurface lesions.. Demineralized bovine dentine specimens were stored either in mineral water [saturation with respect to octacalcium phosphate (S(OCP)): 0.7], Glandosane (G, S(OCP): 0.3) or in a modified saliva substitute Saliva natura (SN, S(OCP): 1.9) for five weeks (37°C). Fluoride agents were applied twice daily for 10 min (n = 15/group): no treatment, Meridol mouthrinse, Elmex sensitive solution, ProSchmelz fluoride gel, Elmex gelée. After storage thin sections were prepared and mineral losses before and after storage were evaluated from microradiographs.. Specimens stored in G alone showed significantly higher mineral loss compared to those stored in water, SN or G in combination with any additional treatment (p < 0.05). Storage in SN and treatment with ProSchmelz fluoride gel led to significantly higher remineralization compared to all other groups (p < 0.05) and resulted in distinct mineral gain within the lesion body.. Under the in vitro conditions chosen, use of fluoride agents in combination with a demineralizing saliva substitute resulted in reduced mineral loss. Storage in modified Saliva natura in combination with the application of ProSchmelz fluoride gel induced the most pronounced remineralization also of deeper lesion areas.

Topics: Amines; Animals; Apatites; Calcium Fluoride; Calcium Phosphates; Cariostatic Agents; Cattle; Dental Caries; Dentin; Diamines; Drug Combinations; Durapatite; Fluorides; Gels; Microradiography; Minerals; Mouthwashes; Random Allocation; Saliva, Artificial; Temperature; Time Factors; Tin Fluorides; Tooth Demineralization; Tooth Remineralization

Patients irradiated in the head and neck region often suffer from severe dry mouth and use acidic saliva stimulating products, which may cause erosion of teeth.. To determine saliva stimulating effects and erosive potential (EP) of acidic saliva stimulating tablets (Xerodent) with and without fluoride in irradiated head and neck cancer patients.. Nineteen irradiated patients (median age 57 years) sucked Xerodent tablets with and without fluoride. Saliva collections were divided into three 10-min sessions in the sequence: unstimulated whole saliva, Xerodent stimulated saliva without fluoride, and with fluoride. Saliva pH was determined without loss of CO(2) and in combination with inorganic measures used to calculate the degree of saturation of hydroxyapatite (HAp) and fluorapatite (FAp). EP was determined directly in all saliva samples by monitored dissolution of HAp crystals.. Saliva flow rates increased significantly (15-fold) when sucking both tablets (p<0.001). Major changes in saliva composition caused undersaturation of HAp in some samples. However, no dissolution of HAp occurred in the saliva obtained with any of the two tablets. This was most likely due to the limited drop in pH resulting in saliva that was still supersaturated with respect to FAp.. Both Xerodent with and without fluoride were evaluated as non-erosive, however, for additional caries protection the fluoride variant is preferable.

Topics: Apatites; Dental Caries; Durapatite; Female; Fluorides; Head and Neck Neoplasms; Humans; Hydrogen-Ion Concentration; Male; Middle Aged; Radioactive Hazard Release; Saliva; Salivary Glands; Tooth Erosion; Xerostomia

The aims of this study were: (1) to correlate surface (SH) and cross-sectional hardness (CSH) with microradiographic parameters of artificial enamel lesions; (2) to compare lesions prepared by different protocols. Fifty bovine enamel specimens were allocated by stratified randomisation according to their initial SH values to five groups and lesions produced by different methods: MC gel (methylcellulose gel/lactic acid, pH 4.6, 14 days); PA gel (polyacrylic acid/lactic acid/hydroxyapatite, pH 4.8, 16 h); MHDP (undersaturated lactate buffer/methyl diphosphonate, pH 5.0, 6 days); buffer (undersaturated acetate buffer/fluoride, pH 5.0, 16 h), and pH cycling (7 days). SH of the lesions (SH(1)) was measured. The specimens were longitudinally sectioned and transverse microradiography (TMR) and CSH measured at 10- to 220-microm depth from the surface. Overall, there was a medium correlation but non-linear and variable relationship between mineral content and radicalCSH. radicalSH(1) was weakly to moderately correlated with surface layer properties, weakly correlated with lesion depth but uncorrelated with integrated mineral loss. MHDP lesions showed the highest subsurface mineral loss, followed by pH cycling, buffer, PA gel and MC gel lesions. The conclusions were: (1) CSH, as an alternative to TMR, does not estimate mineral content very accurately, but gives information about mechanical properties of lesions; (2) SH should not be used to analyse lesions; (3) artificial caries lesions produced by the protocols differ, especially considering the method of analysis.

Topics: Acetates; Acrylic Resins; Anatomy, Cross-Sectional; Animals; Apatites; Buffers; Calcium Phosphates; Cariogenic Agents; Cariostatic Agents; Cattle; Dental Caries; Dental Enamel; Diphosphonates; Durapatite; Fluorides; Gels; Hardness; Hydrogen-Ion Concentration; Lactic Acid; Methylcellulose; Microradiography; Random Allocation; Solutions; Time Factors; Tooth Demineralization; Tooth Remineralization

Topics: Apatites; Cariostatic Agents; Dental Caries; Dental Enamel; Dental Plaque; Dentifrices; Fluoridation; Fluorides; Humans; Hydrogen-Ion Concentration; Saliva; Tooth Demineralization; Tooth Remineralization

Topics: Adolescent; Adult; Apatites; Cariostatic Agents; Child; Child, Preschool; Dental Care for Children; Dental Caries; Fluoridation; Fluorides; Fluorides, Topical; Fluorosis, Dental; Humans; Infant; Mouthwashes; Tooth Remineralization; Toothpastes

This article discusses fluoride-releasing materials, including their caries-inhibiting properties and clinical longevity, as well as provides useful application tips. Based on results from clinical trials, there is growing evidence that fluoride-releasing materials, particularly glass ionomers, reduce the occurrence of recurrent caries. As such, they should be employed-especially in the case of high caries-risk patients-as part of an overall treatment plan for maximum care.

Topics: Apatites; Bacteria; Cariostatic Agents; Compomers; Composite Resins; Dental Caries; Dental Plaque; Dental Restoration Wear; Dental Restoration, Permanent; Fluorides; Glass Ionomer Cements; Humans; Tooth Remineralization

The benefits of using fluoride to prevent caries have been known for many years, but a complete understanding of this mechanism is still being researched. The fluoride concentration in the apatitic structure of enamel does not have as significant an effect on reducing caries as a continuous presence of fluoride in the plaque liquid. Concentrated, topical fluoride agents (such as in toothpaste, fluoride mouth rinses, gels, or varnishes) have a different mechanism of fluoride protection than low-concentration applications (such as fluoridated water). In initial caries lesions and plaque, concentrated agents form globules of a calcium fluoride-like material on the enamel surface. This material is fairly insoluble, possibly because it is coated with phosphates or proteins. This mechanism explains how the topical application of a fluoride varnish, two or three times a year, can result in caries reduction.

Topics: Apatites; Calcium Fluoride; Cariostatic Agents; Dental Caries; Dental Enamel; Dental Enamel Solubility; Dental Plaque; Exudates and Transudates; Fluorides; Fluorides, Topical; Humans; Hydrogen-Ion Concentration; Sodium Fluoride; Tooth Demineralization; Tooth Remineralization

A possible chemical process occurring during caries reversal is conversion of acidic calcium phosphates to apatite. The role of fluoride in this process is of particular interest. The effects of fluoride on the rate of CaHPO4 hydrolysis at 37.4 degrees C were studied by a multimethod analysis involving X-ray diffraction, analyses of variations in solution chemistry, and observation of microstructural evolution. Hydrolysis in low NaF concentrations results in the formation of discrete fluorapatite crystals on the surfaces of the CaHPO4 crystallites. At CaHPO4/NaF molar ratios from approximately 9:1 to 10:2, fluorapatite formed in approximately 3 h as the only crystalline product and complete hydrolysis of CaHPO4 occurred; a pH value as low as 2.4 was attained with solution species being predominantly sodium phosphate. At NaF concentrations beyond those which result in pH minima, fluorapatite and CaF2 are the crystalline products. At 0.6 M NaF, pseudomorphs composed of fluorapatite and CaF2 crystals form without developing morphologies characteristic of individual fluorapatite and CaF2 crystals. CaHPO2 can hydrolyze completely to fluorapatite and CaF2 within a few hours depending on NaF concentration and liquid-to-solids ratio.

Topics: Apatites; Calcium Fluoride; Calcium Phosphates; Chemical Phenomena; Chemistry, Physical; Crystallization; Crystallography; Dental Caries; Humans; Hydrogen-Ion Concentration; Hydrolysis; Microchemistry; Osmolar Concentration; Phosphates; Sodium Fluoride; Temperature; Time Factors; X-Ray Diffraction

Data obtained in a previous study suggested that brushite is the solubility-determining phase when enamel is first exposed to acid solution in a series of repeated equilibrations. Fluoride in solution might be expected to inhibit brushite formation, and experimental studies at low solid/solution ratio support this. We have now re-examined the effect at a very high ratio, in an attempt to mimic what happens in an enamel caries lesion. Powdered enamel was repeatedly exposed to HCl solution, 10-70 mmol/l, containing 2 ppm F, for 24 h, initially in a ratio of 1 g/3 ml. Ion activities were determined after 20 min and 24 h and potential plot diagrams constructed. In early repetitions the -log (Ca2+) (OH-)2 vs. -log (H+)3(PO4(3-)) points tended to follow the brushite line, rather than the hydroxyapatite (HAp) line which one would expect if enamel behaved as pure HAp. Solution F was below measurable limits after 20 min and F then had little influence on the brushite equilibrating phase. In later (> 13) repetitions, points fell closer to the HAp line, with or without F added to the acid solution. However, added F, which was not then completely removed from solution, caused the slope of the regression line through the points to approach the Ca/P ratio of HAp, and therefore may have had a small effect in reducing the brushite phase. It is concluded that high solid/solution ratio, a previously neglected factor in enamel dissolution studies, has a profound effect in increasing the manifestation of a brushite surface phase and reducing the inhibitory effect of F on this phase.

Topics: Apatites; Calcium; Calcium Hydroxide; Calcium Phosphates; Chemical Phenomena; Chemistry, Physical; Dental Caries; Dental Enamel; Dental Enamel Solubility; Durapatite; Fluorides; Humans; Hydrochloric Acid; Phosphates

Acids produced by various oral bacteria cause mineral loss and crystallite dissolution during the development of enamel caries. In order to demonstrate this phenomenon, the initial disappearance of lattice fringes and the formation of a central perforation in crystallites were examined by high resolution electron microscopy (HREM) in initial enamel caries without macroscopic tissue evidence of destruction. Ultrathin sections were also examined by selected area electron diffraction to reveal the mineral phase of the surface layer in carious enamel. A marked variation in the dissolution pattern was disclosed in the initial carious lesions. HREM revealed that disappearance of the lattice fringes from the lateral portion of the crystallites was predominant in the superficial layer covering the lesion, while central perforation of crystallites mainly occurred in the subsurface prismatic region. The beginning of the central dissolution occurred at the dislocated area where lattice striations appeared to be disordered. Selected area electron diffraction of the gradually demineralized enamel revealed a pattern consistent with hydroxyapatite (OH-AP) or fluorapatite (F-AP) mineral. These findings suggest that the susceptibility to caries of enamel crystallites is spatially and temporally different during the progression of the caries. Furthermore, the formation of central perforations and the consequent easy intracrystalline diffusion of acids might induce rapid crystallite dissolution.

Topics: Adult; Apatites; Dental Caries; Dental Enamel; Durapatite; Electron Probe Microanalysis; Humans; Male; Microscopy, Electron; Molar, Third; Tooth Demineralization

Topics: Apatites; Calcium; Child; Dental Caries; Dental Caries Susceptibility; Humans; Lactobacillus; Phosphates; Risk Factors; Saliva; Streptococcus mutans

Human enamel surfaces were exposed to sequential batch cultures of Streptococcus mutans NCTC 10832 in a sucrose-rich medium containing 0-5 mg/l added fluoride (F). In 10-day experiments, subsurface lesion formation was partly inhibited by 1 mg/l F and completely by 2 and 5 mg/l F, but small lesions formed in 2 mg/l F in 21-day experiments. Analysis of the spent media, together with analogous, bacteria-free experiments, suggested that lesion inhibition involved two main effects. First, inhibition of bacterial acid production reduced the pH fall, resulting in reduced undersaturation with respect to hydroxyapatite and consequently reduced rate of demineralization. Secondly, interaction of F with enamel mineral resulted in a small increase in reprecipitation during periods of supersaturation and a much larger reduction in demineralization during periods of undersaturation. It is concluded that, at low F concentrations, inhibition of bacterial acid production is a major factor in lesion inhibition, which may contribute significantly to caries prevention in vivo where plaque fluid F levels are raised by frequent topical applications.

Topics: Apatites; Calcium; Culture Media; Dental Caries; Dental Enamel; Durapatite; Fluorides; Humans; Hydrogen-Ion Concentration; In Vitro Techniques; Streptococcus mutans; Tooth Calcification; Tooth Demineralization

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.

Topics: Apatites; Calcium Phosphates; Child; Dental Caries; Dental Plaque Index; Discriminant Analysis; DMF Index; Durapatite; Fluoridation; Fluorides; Forecasting; Humans; Hydroxyapatites; Lactobacillus; Longitudinal Studies; Male; Models, Statistical; New Hampshire; New York; Predictive Value of Tests; Risk Factors; Saliva; Sensitivity and Specificity; Streptococcus mutans; Surveys and Questionnaires

Topics: Apatites; Dental Caries; Dental Enamel; Durapatite; Fluorides; Humans; Hydroxyapatites

The cariostatic effect of fluoride at different levels of pH in the plaque fluid is discussed. At the pH level 5.5 to 4.5 the plaque fluid is undersaturated with respect to hydroxyapatite and supersaturated with respect to fluorapatite (3). The hydroxyapatite of the enamel then dissolves. With fluoride present in the liquid phase a fluoridated apatite is precipitated in the surface zone of the lesion. In acidic, old plaque the plaque fluid is very likely undersaturated also with respect to fluorapatite (pH less than 4.5) (11). When the liquid phase is undersaturated with respect to fluorapatite no redeposition of mineral lost can occur. In due time an erosion will develop. It is speculated that one reason for the minor effect of fluoride in some caries active patients and in fissures as well is that the plaque fluid is undersaturated with respect to fluorapatite for extended periods.

Topics: Apatites; Dental Caries; Dental Enamel; Dental Enamel Solubility; Dental Plaque; Durapatite; Fluorides; Humans; Hydrogen-Ion Concentration; Hydroxyapatites

The aim of the present study was to evaluate the significance of diffusion barriers in the development of artificial caries-like lesions. A 30-mm2 enamel surface area was covered with a layer of filter paper and exposed to a gently agitated 50 mM acetate buffer, pH 4.5, containing either 0.1 or 1.0 ppm fluoride for up to 48 h at 20 degrees C. Similar enamel surfaces, but unprotected by filter paper, served as controls. It was found that below the filter paper an approximately 60-microns-deep caries-like lesion was developed exhibiting a preserved surface layer, the mineral content of which depended on the fluoride concentration of the buffer. The lesions of the control teeth without a filter paper coverage were erosion-like surface lesions. In the filter paper calcium and phosphate released from the enamel combined with fluoride from the bulk solution had established a supersaturation with respect to fluorapatite while the undersaturation with respect to hydroxyapatite was maintained, which caused a caries lesion to develop. The lesions produced in noncovered enamel by bulk solution unsaturated with respect to both apatites were erosion-like. It was concluded that a diffusion barrier can significantly favor the establishment of supersaturation with respect to fluorapatite and thus facilitate the development of a subsurface caries-like lesion at the expense of the erosion.

Topics: Apatites; Calcium; Dental Caries; Dental Enamel; Diffusion; Durapatite; Filtration; Fluorides; Humans; Hydroxyapatites; Models, Biological; Paper; Phosphates; Solubility; Tooth Erosion

The aim of the present paper was to study the relation between the development of enamel erosion and caries lesion. Intact teeth were exposed to a gently agitated 50 mM acetate buffer, with or without fluoride for various periods of time. Further, intact teeth were exposed to an agitated 0.2 M HCl solution. It was found that irrespective of experimental conditions the aqueous phase was initially unsaturated with respect to both hydroxyapatite and fluorapatite during which period fluorhydroxyapatite was dissolved. Histological examination showed that the dissolving apatite originated from the enamel surface and the resulting lesion exhibited the signs of a dental erosion. The depth of the erosive lesion was found to be a direct function of the amount of mineral dissolved before the aqueous phase became saturated with respect to fluorapatite. The calcium, phosphate and fluoride dissolved made the aqueous phase first saturated and later supersaturated with respect to fluorapatite and a reuptake of fluoride in the enamel began, now under development of a caries-like lesion with preservation of the surface layer over a subsurface demineralizing zone. The demineralization depended on the volume of the aqueous phase. In conclusion, in a closed system with a limited amount of unsaturated solution a double lesion, an erosion over a caries lesion, will develop according to the changing saturation with respect to fluorapatite.

Topics: Apatites; Calcium; Dental Caries; Dental Enamel; Durapatite; Fluorides; Humans; Hydroxyapatites; Solutions; Tooth Erosion

The aim of the present study was to compare the resistance of fluoroapatite (shark enamel) and hydroxyapatite (human enamel) against a high caries challenge in a human in vivo model. Two samples of shark enamel and human enamel were each placed in removable appliances in six children and carried for 1 month and a plaque retentive device was placed over each enamel sample. The results showed that the mean total mineral loss (delta Z) was 1680 vol% micron in human enamel and 965 vol% micron in shark enamel. The corresponding mean values for lesion depth were 90 micron and 36 micron, respectively. It is concluded that even shark enamel containing 30,000 ppm F has a limited resistance against caries attacks.

Topics: Adolescent; Animals; Apatites; Child; Dental Caries; Dental Caries Susceptibility; Dental Enamel; Durapatite; Humans; Hydroxyapatites; Microradiography; Sharks

Dicalcium phosphate dihydrate (DCPD) may play a significant role in the caries lesion since it is a stable calcium phosphate phase under acidic conditions. The reaction of DCPD and fluoride, forming fluorapatite (FAP), may provide a potentially promising treatment regimen for remineralization of caries lesions in vivo. The purpose of this study was to determine whether a two-step DCPD and inorganic wash with fluoride can remineralize artificial caries-like lesions in vitro. We used the single-section technique to facilitate quantitation of the same tissue before and after the experimental regimen. The two-step remineralizing treatment was repeated three times and consisted of a two-minute saturated DCPD treatment (pH 2.1) followed by a 24-hour inorganic wash. Lesion parameters were recorded before and after treatment by the taking of polarized light photomicrographs of each section after imbibition in several media. The changes in the tissue following treatment were expressed as a percent change in the area of the initial pre-treatment lesion. Significant reductions (p < 0.02) in lesion pore volume were observed in all aqueous media examined. In the lesions after imbibition in quinoline, remineralization was also apparent from the significant increase in the area of the dark zone following treatment. This two-step DCPD treatment appears to remineralize artificial caries-like lesions effectively, but additional work is needed to determine whether it affords any protection against subsequent cariogenic challenges.

Topics: Apatites; Calcium Phosphates; Cariostatic Agents; Dental Caries; Dental Enamel; Fluorides; Follow-Up Studies; Humans; Hydrogen-Ion Concentration; Image Processing, Computer-Assisted; Microscopy, Polarization; Photomicrography; Porosity; Quinolines; Tooth Remineralization; Water

Topics: Apatites; Crystallization; Dental Caries; Dental Enamel; Hydroxyapatites; Orthodontic Appliances; Spectrophotometry, Infrared

The beneficial effect of fluoride to tooth enamel and its potentially harmful effect on bone, may be explained by simple and similar mechanisms. In individuals whose skeletal tissues contain higher than normal levels of fluoride there is a possibility that during resorptive and remodeling processes, bone (and bone marrow) cells may be exposed to genotoxic and lethal levels of fluoride. The success of fluoride as a preventive against dental caries does not mean that unnecessary exposure to the element should be tolerated. Total daily fluoride intake from a multiplicity of possible everyday sources should be monitored; and the assumption that sodium fluoride is safe to use as an anti-caries agent, particularly for expectant mothers and children, should be reviewed.

Topics: Absorption; Apatites; Body Weight; Bone and Bones; Bone Diseases; Bone Resorption; Crystallization; Dental Caries; Dental Enamel; Durapatite; Fluorides; Humans; Hydroxyapatites; Kidney; Models, Biological; Osteoclasts; Osteocytes; Time Factors

Topics: Apatites; Buffers; Chemical Phenomena; Chemistry; Chemistry, Physical; Dental Caries; Dental Enamel; Humans; Hydroxyapatites

A diffusion cell comprising two compartments separated by a commerical membrane of known ion permselectivity was used as an experimental model to study factors which may affect caries formation. One compartment (the "lesion") contained an excess of hydroxyapatite or fluorapatite crystals, and its solution was kept near saturation by stirring. An unsaturated acidic calcium phosphate solution flowed continuously through the other compartment (the "plaque-saliva"), thus providing the driving force for dissolution of the crystals as modified by the permeability of the membrane and/or the presence of fluoride. Calcium, phosphate, fluoride, and chloride concentrations, pH, and membrane potential were measured at steady state. The permselective character of the membrane profoundly affected the solution in the "lesion": The initial Ca/P ratio of 1.6 was shifted, at steady state, to less than 1.1 ("neutral" membrane), to less than 0.48 (cation-permselective membrane), and to 3.3 (anion-permselective membrane). All the membranes caused Ca and PO4 concentrations in the "lesion" to increase (e.g., with the cation-permselective membrane, the Ca 22-fold and the PO4 75-fold). Substantial membrane potentials were encountered in all cases. The pH of the steady-state solution was always less than before diffusion was initiated; the average decrease was 1.1 units. In every case, the pH, and the Ca and PO4 concentrations of the F- -containing solution were less than those in the F- -free solution. The changes induced by the "neutral" membrane were unexpectedly large. In two cases, H3PO4 was diffusing against its chemical potential gradient at steady state. The results are relevant for understanding and for modeling of the caries process.

Topics: Apatites; Calcium Hydroxide; Chemical Phenomena; Chemistry, Physical; Dental Caries; Diffusion; Durapatite; Electrochemistry; Humans; Hydroxyapatites; Membranes, Artificial; Models, Biological; Models, Chemical; Permeability; Phosphates; Solubility

The retention of alkali soluble (CaF2) and alkali insoluble (fluorapatite) fluoride in sound enamel and demineralized enamel 2 wk after application of Duraphat was investigated in a group of orthodontic patients from whom pairs of homolog premolars were to be extracted. Demineralization of the enamel was induced during a 4-wk period prior to application of fluoride by applying orthodontic bands to the premolars. The bands also remained attached to the teeth during and after application of fluoride (2 wk) to maintain a cariogenic environment. Three consecutive enamel layers (approximately 5 microns) were subsequently etched off. A significant uptake of fluoride in the first and second layer of sound enamel and in all the three enamel layers of demineralized enamel was found. More fluoride was found in demineralized enamel and a higher proportion of this fluoride was found to be in an alkali insoluble form compared with the fluoride in sound enamel. The SEM study showed a rough enamel surface after three consecutive acid etchings. The etching pattern differed within the etched area. It was suggested that the variation in etching pattern might be due to differences in orientation of the crystallites and the original surface morphology.

Topics: Acid Etching, Dental; Adolescent; Apatites; Calcium Fluoride; Child; Dental Caries; Dental Enamel; Fluorides, Topical; Humans; Microscopy, Electron, Scanning; Sodium Fluoride

Demineralization of enamel was induced by applying orthodontic bands in 15 patients having two of their premolars extracted for orthodontic reasons. After a 4-wk caries induction period, eight patients were instructed to rinse their teeth once daily with a neutral 0.05% NaF solution, whereas seven patients received a single treatment with a neutral 2% NaF solution. The bands were reattached to the teeth during the fluoride treatment period and the teeth were extracted after two more weeks. Three consecutive enamel layers were etched off, and a significant uptake of fluoride in all three layers were found in both treatment groups. A larger part of the deposited fluoride was retained in an alkali insoluble form (i.e. fluorapatite) compared with previous studies of sound enamel. It is suggested that the chemical conditions in the cariogenic milieu were favorable for transformation of the fluoride into a stable apatite structure.

Topics: Alkalies; Apatites; Calcium Fluoride; Dental Caries; Dental Enamel; Fluorides; Humans; Sodium Fluoride; Solubility

Oral application of fluoride for caries prevention may tend to form calcium fluoride (CaF 2) instead of the desired fluorapatite. In view of this, the transformability of CaF2 to fluorapatite has been studied. This investigation shows that CaF2 can be converted to fluorapatite in phosphate solutions ar various temperatures ranging between 25 and 75 degrees C in the pH range of 6.5 to 8.5. In the initial stage, phosphate ions, believed to be HPO4= adsorb on the particle surface. A dissolution/precipitation mechanism is proposed for the growth of fluorapatite.

Topics: Apatites; Calcium Fluoride; Chemical Phenomena; Chemical Precipitation; Chemistry, Physical; Dental Caries; Hydrogen-Ion Concentration; Kinetics; Phosphates; Temperature

In this paper the mechanism of dental enamel dissolution is discussed. Special attention is given to the anisotropic solubility behaviour (hollow tube formation) of demineralized enamel crystallites. The combined evidence strongly indicates that this peculiar dissolution behaviour is caused by dislocations. The dislocations--linear lattice defects--are present in the crystallite center and are the cause of two active dissolution sites in each crystallite. Initial as well as later stages in the caries process are discussed. Experimental evidence is presented which indicates that the active sites can be inactivated by agents like EHDP and MFP. After inactivation, acid penetration is either prevented or strongly retarded.

Topics: Apatites; Calcium; Crystallization; Crystallography; Dental Caries; Dental Enamel; Dental Enamel Solubility; Durapatite; Humans; Hydroxyapatites; Phosphates

Topics: Apatites; Dental Caries; Dentifrices; Fluorides; Humans; Powders; Toothbrushing

Topics: Apatites; Dental Caries; Humans; Tooth; Toothbrushing