Biomedical subjects

M J Larsen

Publications and source records attributed to M J Larsen.

At least 19 recordsLinked to original sources

PubMed2005

Erosion of the teeth: prevalence and distribution in a group of Danish school children.

AIM: This was to describe the prevalence of eroded tooth surfaces among 15-17 years old school children in a Danish city and to assess the reliability of diagnosis of erosions performed by 9 clinical examiners. METHODS: During a calendar year (2000) a total of 558 children in 4 public schools in Aarhus were examined by 7 examiners and 2 coordinators using the following criteria: intact; erosion confined to enamel; erosion exposing less than half of the dentine, and erosion involving more dentine than half the surface. RESULTS: It was found that 14.0% (95% CL: 11.3%; 17.1%) of the children had more than 3 surfaces eroded. In the maxilla lingual surfaces were more affected than the facial surfaces. No lesions exposing more than half of the dentine were observed. Despite a careful calibration, including a thorough discussion of the criteria and the experience gained during the study, a substantial inter examiner difference in diagnosis was found. CONCLUSION: The most frequently eroded sites were the lingual surfaces of maxillary incisors; the identification of eroded areas is often difficult and subject to a low inter examiner reliability.

Adolescent↗

PubMed2003

Saturation of human saliva with respect to calcium salts.

It may be assumed that free ionic concentrations of calcium and phosphate in resting saliva tend to equilibrate with those in plaque fluid, and that salivary data can therefore be used to illustrate chemical conditions in both saliva and plaque. In the present study, salivary data collected from the literature or obtained in our laboratory were used to calculate degrees of super- and undersaturation with respect to apatites, brushite, beta-tricalcium phosphate, octacalcium phosphate, calcium carbonate and calcium fluoride in the pH range from 3 to 9. Concentrations of calcium, phosphate, fluoride, carbonate, and background ion strength of resting parotid saliva, resting submandibular saliva, and resting and stimulated whole saliva were entered into a computer program, and curves illustrating saturation in the pH range 3-9 constructed. It was found that oral fluids are supersaturated with respect to apatites above pH 5.3 and with respect to octacalcium phosphate and beta-tricalcium phosphate above pH 6. Parotid saliva was undersaturated with respect to brushite whilst submandibular saliva was supersaturated with respect to that salt in the pH range 6-8. Stimulated whole saliva with 25 mmol/l carbonate became supersaturated with respect to calcium carbonate only above pH 7.3, which may explain the absence of this salt in the human oral cavity. To maintain the saturation of oral fluids with respect to calcium fluoride, i.e. to ensure its survival in the mouth required 6 ppm fluoride in the aqueous phase. Therefore, this salt, the outcome of topical fluoride therapy, will inevitably dissolve in the oral fluids.

Adult↗

PubMed2003

Effects of KHEYLRFamide and KNEFIRFamide on cyclic adenosine monophosphate levels in Ascaris suum somatic muscle.

KHEYLRF-NH(2) (AF2) is a FMRFamide-related peptide (FaRP) present in parasitic and free-living nematodes. At concentrations as low as 10 pM, AF2 induces a biphasic tension response, consisting of a transient relaxation followed by profound excitation, in neuromuscular strips prepared from Ascaris suum. In the present study, the effects of AF2 on cyclic adenosine monophosphate (cAMP), cyclic guanosine monophosphate (cGMP) and inositol-1,4,5-triphosphate (IP(3)) levels were measured following muscle tension recordings from 2 cm neuromuscular strips prepared from adult A. suum. AF2 induced a concentration- and time-dependent increase in cAMP, beginning at 1 nM; cAMP levels increased by 84-fold following 1 h exposure to 1 microM AF2. cGMP and IP(3) levels were unaffected by AF2 at concentrations </=1 microM. AF2-induced stimulation of cAMP was unaffected by removal of the dorsal or ventral nerve cord, even though this form of denervation abolished the excitatory phase of the tension response. The effects of 0.1 and 1 microM AF2 on cAMP were also unaffected by 10 microM SDPNFLRF-NH(2) (PF1, an inhibitory FaRP) and 10 microM PF1022A (an inhibitory cyclodepsipeptide), even though each of these peptides abolished the excitatory phase of the tension response induced by AF2. Within an alanine-scan series of AF2 analogues, only KHAYLRF-NH(2) stimulated cAMP production with equipotency to AF2; the effects of this peptide on muscle tension also mimicked AF2. Another excitatory FaRP present in nematodes, KNEFIRF-NH(2) (AF1), also stimulated cAMP production, but was 100-fold less potent than AF2. The stimulatory effects of AF1 on tension and cAMP levels were blocked by an alanine-substituted analogue of this peptide (Ala(6)-AF1, KNEFIAF-NH(2)), while the stimulatory effects of AF2 on tension and cAMP were not affected by this analogue. AF2 and AF1 increase A. suum somatic muscle cAMP by targeting different receptors. Increases in cAMP stimulated by AF2 can be decoupled from the excitatory response caused by this peptide, and it is not possible to establish a causal linkage between the contractile response elicited by this peptide and its effects on cAMP accumulation.

Animals↗

PubMed2001

Type A allatostatins from Drosophila melanogaster and Diplotera puncata activate two Drosophila allatostatin receptors, DAR-1 and DAR-2, expressed in CHO cells.

The type-A allatostatins A (AST-A) are a group of insect peptides with a common C-terminal motif Y/FXFGL-NH(2). The existence of at least four putative type A Drosophila melanogaster ASTs (called type A drostatins or DST-As) has been predicted from the sequence of a recently cloned DST-A preprohormone [C. Lenz et al. (2000) Biochem. Biophys. Res. Commun. 273, 126-1131]. SRPYSFGL-NH(2), (DST-3A), the only DST isolated from Drosophila so far, activated the first cloned DST-A GPCR (DAR-1) [N. Birgül et al. (1999) EMBO J. 18, 5892-5900]. A newly cloned orphan Dm GPCR, which shares 47% overall and 60% transmembrane region sequence identity with DAR-1, was classified as a second putative Dm DST-A receptor (DAR-2) [C. Lenz et al. (2000) Biochem. Biophys. Res. Commun. 273, 571-577]. Although activation of DAR-2 by DSTs has been postulated, no experimental evidence for that has been presented to date. In this study, we expressed both DAR-1 and DAR-2 in CHO cells and used a GTPgammaS and a Ca(2+) mobilization assay for pharmacological evaluation of the receptors. Synthetically prepared DST-As, as well as selected Diplotera punctata (cockroach) ASTs, activated DAR-1 and DAR-2 in both functional assays indicating ligand redundancy and cross species activity. Cell pretreatment with pertussis toxin led to some differences in the nature and magnitude of signaling pathways at the DAR-1 and DAR-2 receptors, suggesting possible differential coupling to cellular effector system(s) and distinct biological functions of each receptor in vivo.

Amino Acid Motifs↗

PubMed2000

A laboratory study evaluating the release of hydroxyl ions from various calcium hydroxide products in narrow root canal-like tubes.

AIM: The aim of the present study was to describe pH changes in a variety of buffering solutions within a narrow test tube containing either a gutta-percha point with incorporate calcium hydroxide, a commercial calcium hydroxide paste (Calcicur) or a freshly mixed paste of calcium hydroxide in distilled water. METHODOLOGY: The test material was placed centrally in a test tube of 2 mm inner diameter. Saline (1%) was placed at one end, whilst the buffering solutions were introduced at the other. The pH of the buffering solutions was monitored using electrodes placed at each end of the test tube. RESULTS: It was found that the pH 4.01 buffer strongly resisted pH changes at levels below 6.0, whilst saliva and bovine serum was buffered less and more evenly in the whole range up to pH 11.5. The calcium hydroxide containing gutta-percha points caused the pH to increase quickly in the sodium chloride solution to levels above 11.5. However, in bovine serum, in saliva and in the pH 4.01 buffer the pH remained below 8.5, 8.0 and 6.0, respectively, 1 mm from the point. In contrast, the release of hydroxyl ions from the two calcium hydroxide pastes brought pH above pH 11.5 irrespective of the buffering of the solutions 5 mm from the paste. CONCLUSION: It is concluded that Calcicur and the calcium hydroxide-water mixture contained substantially more available calcium hydroxide than did the calcium hydroxide containing gutta-percha points, with the result that the release of hydroxyl ions from the points was limited in comparison to that from the pastes.

Animals↗

PubMed1999

Individual variations of pH, buffer capacity, and concentrations of calcium and phosphate in unstimulated whole saliva.

In order to evaluate the risk of development of dental caries and/or of formation of dental calculus, salivary variables have often been used, but not with particular success. A reason for the apparent lack of association could be that the individual temporal variation of a characteristic was so substantial relative to the overall variation that it is not possible to characterize an individual by a single salivary measurement. The aim here was to examine the individual variation of pH, buffer capacity, and concentrations of calcium and phosphate and to compare it with the overall variation of the characteristics in order to shed light on the above problem. Eight weekly samples of up to 4 ml of unstimulated whole saliva were collected from 11 dental students before tooth brushing on their arrival at 8 a.m. in the dental school. Calcium was determined by atomic absorption spectroscopy, phosphate colorimetrically, and pH electrometrically. The buffer capacity was assessed by titration of the saliva sample from the pH initially observed to pH 3. It was found that within each individual the concentration of calcium and of phosphate, pH, the hydroxyapatite ion product and the buffer capacity varied considerably over the 7 weeks. The individual range frequently covered more than a third of the total range. Further, within each of the variables, single individuals could be found whose samples covered 60% or more of the overall range, whilst others covered less than 10% of the range. It was therefore concluded that, although collected at the same time of the day, pH, buffer capacity and concentrations of calcium and phosphate in unstimulated whole saliva in the single individual vary so much that characterization of individuals and of their saliva based on a single salivary analysis is unreliable and hazardous.

Buffers↗

PubMed1999

Pharmacology of FMRFamide-related peptides in helminths.

Nervous systems of helminths are highly peptidergic. Species in the phylum Nematoda (roundworms) possess at least 50 FMRFamide-related peptides (FaRPs), with more yet to be identified. To date, few non-FaRP neuropeptides have been identified in these organisms, though evidence suggests that other families are present. FaRPergic systems have important functions in nematode neuromuscular control. In contrast, species in the phylum Platyhelminthes (flatworms) apparently utilize fewer FaRPs than do nematodes; those species examined possess one or two FaRPs. Other neuropeptides, such as neuropeptide F (NPF), play key roles in flatworm physiology. Although progress has been made in the characterization of FaRP pharmacology in helminths, much remains to be learned. Most studies on nematodes have been done with Ascaris suum because of its large size. However, thanks to the Caenorhabditis elegans genome project, we know most about the FaRP complement of this free-living animal. That essentially all C. elegans FaRPs are active on at least one A. suum neuromuscular system argues for conservation of ligand-receptor recognition features among the Nematoda. Structure-activity studies on nematode FaRPs have revealed that structure-activity relationship (SAR) "rules" differ considerably among the FaRPs. Second messenger studies, along with experiments on ionic dependence and anatomical requirements for activity, reveal that FaRPs act through many different mechanisms. Platyhelminth FaRPs are myoexcitatory, and no evidence exists of multiple FaRP receptors in flatworms. Interestingly, there are examples of cross-phylum activity, with some nematode FaRPs being active on flatworm muscle. The extent to which other invertebrate FaRPs show cross-phylum activity remains to be determined. How FaRPergic nerves contribute to the control of behavior in helminths, and are integrated with non-neuropeptidergic systems, also remains to be elucidated.

Amino Acid Sequence↗

PubMed1999

Enamel erosion by some soft drinks and orange juices relative to their pH, buffering effect and contents of calcium phosphate.

The capability of a soft drink or a juice to erode dental enamel depends not only on the pH of the drink, but also on its buffering effect. As the latter is the ability of the drink to resist a change of pH it may add to the effects of the actual pH. The aim of the present study was to compare the pH and the buffering effect of various soft drinks with their erosive effects and the solubility of apatite. In 18 soft drinks, mineral waters and juices available on the Danish market, pH and the concentrations of calcium, phosphate and fluoride were determined. The buffering effect was determined by titration with NaOH. Human teeth (n = 54) covered with nail varnish except for 3x4-mm windows were exposed to 1.5 liters of the drink for either 7 days or 24 h under constant agitation. The depth of the erosions was assessed in longitudinal sections. The depth was found to vary greatly from 3 mm eroded by the most acidic drinks and fresh orange juice to only slightly affected surfaces by most of the mineral waters. The dissolution of enamel increased logarithmically inversely with the pH of the drink and parallel with the solubility of enamel apatite. Orange juice, pH 4.0, supplemented with 40 mmol/l calcium and 30 mmol/l phosphate did not erode the enamel as the calcium and phosphate saturated the drink with respect to apatite. Generally, the lower the pH the more NaOH was necessary to bring the pH to neutrality. In particular the buffering effect of the juice was high. For all drinks, no effect of their low fluoride concentrations was observed.

Apatites↗

PubMed1997

Human supragingival in vivo calculus formation in relation to saturation of saliva with respect to calcium phosphates.

The aim was to establish if there is a correlation between the rate of formation of supragingival calculus and the degree of supersaturation of saliva with respect to apatite, brushite and other calcium phosphates. The rate of calculus formation was estimated by measuring the calculus formed on lingual surfaces of the lower incisors in 15 individuals during 30 days. Submandibular saliva stimulated with citric acid and resting whole saliva, alter pH determination and ultrafiltration to remove protein was analysed for calcium, phosphate, sodium, potassium and carbonate. The degree of saturation with respect to calcium phosphates was calculated using a computer program. The rate of calculus formation among the 15 participants ranged widely, from a score of 0.5 to a high of 15. A close correlation (r = 0.91) between salivary pH and degree of supersaturation was found A weak correlation between calcium and calculus formation was also found. But neither for unstimulated nor stimulated saliva was a significant relation between supersaturation with respect to any of the calcium phosphates and the rate of calculus formation observed. Therefore, taking into consideration the background of the wide range of rates of calculus formation and of degrees of supersaturation, it was concluded that relation between them is unlikely, and the use of degree of saturation as a diagnostic tool seems unreliable.

Adult↗

PubMed1997

Dissolution of powdered human enamel suspended in acid solutions at a high solid/solution ratio under a 5% CO2 atmosphere at 20 degrees C.

The aim was to examine the nature of enamel dissolution in aqueous suspensions with a high solid/solution ratio and in a CO2-rich atmosphere. Before experimentation, a water-saturated mixture of 95% N2-5% CO2 was passed through the acid solutions for 24 hr. Samples of 2 g of powdered enamel were suspended in 7 ml of either 5 or 10 mmol/l HClO4, with or without 2 parts/10(6) fluoride and kept gently agitated for 24 hr in the above atmosphere. The same enamel samples were repeatedly exposed to fresh acid for 26 runs. All experiments were duplicated. The aqueous phase was analysed after 20 min and 24 hr for calcium, phosphate, fluoride, chloride, sodium and magnesium. It was found that after 20 min the fluoride was invariably taken up in the enamel and the solution was supersaturated with respect to hydroxyapatite with pH ranging 6.7-5.6. During the following 24 hr pH increased further, the supersaturation remained unchanged and the concentrations of calcium and phosphate in solution decreased. In contrast, sodium, magnesium and chloride were released from enamel during the entire period. In the later runs, the supersaturation with respect to hydroxyapatite was only modest and the decrease of calcium and phosphate concentrations limited, as were the release of sodium, magnesium and chloride. It is concluded that despite a CO2-rich atmosphere, calcium, phosphate and carbonate were released from enamel and quickly established a supersaturation with respect to hydroxyapatite with a secondary reprecipitation of mineral. It indicates that within the dental caries lesion in vivo, lesion fluid cannot exist undersaturated with respect to enamel apatite.

Acids↗

PubMed1997

A computer program for correlating dental plaque pH values, cH+, plaque titration, critical pH, resting pH and the solubility of enamel apatite.

A computer program was written in Visual Basic (Microsoft) to calculate (a) the area between a plaque pH curve (as seen after a sucrose rinse) and either a resting pH (around pH 7) or a critical pH value (around 5.5) above at least parts of the pH curve; (b) the solubility of apatite at the pH values in plaque; (c) the area between the plaque pH solubility curve and the apatite solubility at the resting pH/critical pH; (d) the area between plaque cH+ curve and the cH+ value at resting pH/ critical pH; and (e) the area between a plaque pH curve and a cut-off pH value below the curve, e.g. pH 3. It was found that because both the cH+ and the solubility of apatite increased logarithmically with a pH drop, the two latter area functions (d, e) were basically different from those based directly on pH curves. Thus, pH changes around the resting pH value had little effect on areas calculated from concentrations of H+ and solubility. In contrast, a small pH change around pH 4 had a strong impact on both demineralization potential and areas based on cH+. Also, because of the logarithmic nature, demineralization potentials were generally large in comparison to remineralization potentials, a point that has hitherto received little attention.

Apatites↗

PubMed1995

Studies on the influence of fluoride on the equilibrating calcium phosphate phase at a high enamel/acid ratio.

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.

Apatites↗

PubMed1995

Stereomicroscopy, film radiography, microradiography and naked-eye inspection of tooth sections as validation for occlusal caries diagnosis.

In establishing a trustworthy validation for occlusal caries lesions, various methods have been used after sectioning teeth. The aim of the present study was to compare the accuracy of four such methods: stereomicroscopy (SM), film radiography (FR), microradiography (MR) and naked-eye inspection (NEI) for the detection of caries in occlusal tooth surfaces. Further, the interobserver agreement between three observers' registrations of occlusal caries by these methods was evaluated. The material consisted of 18 unerupted third molars known to be sound with respect to caries, as they were embedded in bone prior to removal, and 20 erupted third molars with an unknown 'true state of disease'. The teeth were serially sectioned, coded and examined blindly for occlusal caries by three independent observers by the four validation methods under study. SM was demonstrated to be the only method by which all observers correctly identified all 18 unerupted teeth as sound, resulting in a specificity of 1.00. By the other three methods, 1 or more of the unerupted teeth were falsely classified as carious. In the erupted teeth, 73, 58, 52 and 32%, respectively, of the teeth were determined carious by SM, MR, NEI and FR. As it was possible by SM to detect caries in nearly three quarters of the erupted teeth and at the same time to identify all unerupted teeth as sound, this method seemed to be the most trustworthy of the validation methods under study.

Dental Caries↗

PubMed1995

The distribution of fluoride in carious human enamel.

The proton probe has been used to map F concentration changes in the enamel of 15 teeth showing clinical evidence of caries. Thin sections through the lesions were microradiographed and measurements made of the surface zone (radiodense) and body (radiolucent) areas. Each section was then scanned with a focused beam of 2.5 MeV protons, 2000 spot analyses being performed over areas up to 2 x 3 mm. F was determined by detecting gamma rays from a nuclear reaction and the data used to construct 3-D surface plots. The maximum F concentration in the lesion surface zone was extremely variable, ranging from 1750 to 21,700 ppm, and rarely occurred over the deepest part of the lesion. F levels were elevated in the lesion body but usually to a small extent only. A large increase in F throughout the lesion body was found in 3 lesions only, and was associated with a surface zone that was thin or of low x-ray density. Relatively small F increases in the lesion body were associated with either a thick, x-ray dense surface layer having a greatly increased F level (> 10,000 ppm) or, conversely, with a surface layer having a relatively small F increase. Since F uptake can be regarded as a "marker" of past remineralization events, this study shows that remineralization can and does occur in the body of natural enamel caries lesions, especially when the surface layer is thin or lost. Fluoride availability that encourages the formation of an extremely dense surface layer may result in under-achievement of this natural repair process in the lesion body.

Dental Caries↗

PubMed1994

The effectiveness of bone char in the defluoridation of water in relation to its crystallinity, carbon content and dissolution pattern.

The procedure for charring bone has been found to influence the nature of its mineral phase, and also affects the defluoridation capacity of the char. The aim of this study was to examine the efficiency of defluoridation by char produced from various parts of bones and charred for various lengths of time at various temperatures, relating the preparation of the char to its X-ray diffraction pattern, its content of pyrophosphate and its capacity for defluoridation. Bone was charred for 1 and 4 h at 400 degrees C and 30 min, 4 h and 48 h at 550 degrees C. Batches of the chars were suspended in amounts of 0.25 g in 100 ml of distilled water containing 0.53 mmol/l fluoride for up to 6 days under gentle agitation. At intervals, the pH and concentrations of fluoride, calcium and phosphate in the water were determined and the degree of saturation with respect to the calcium phosphate salts calculated. The charring procedure reduced the organic content of the bone from the 44-26% in intact bone to 3.4% in bone charred at 400 degrees C and to almost zero when charred at 550 degrees C for 48 h. When charred at 400 degrees C for up to 4 h the X-ray diffraction pattern of the bone showed a poorly crystallized apatite similar to that of untreated bone. Heating for 48 h or more at 550 degrees C led to considerably sharper apatite reflections, indicative of a well-crystallized salt.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗

PubMed1994

Experiments on the initiation of calcium fluoride formation with reference to the solubility of dental enamel and brushite.

As calcium fluoride formation following topical application of fluoride may be responsible for at least some of the caries-reducing effect of fluoride, the concentration of fluoride necessary to induce its formation were examined. The aim was to determine the degree of supersaturation with respect to calcium fluoride necessary for inducing its spontaneous precipitation, with close reference to its possible formation and retention on dental hard tissue when topical fluoride solutions are used clinically. Powdered enamel or brushite were suspended for 4 h in aqueous solutions buffered at pH 7.2 and 5.0. After the equilibration, ion concentrations were determined and degrees of saturation with respect to apatite and brushite were calculated. In aqueous solutions at pH 7.2 and 5.0 with similar concentrations as those found in the equilibrated suspensions the fluoride concentration was adjusted to from 5 to 500 parts/10(6). After 2 h of gentle agitation the supernatant was analysed, the precipitate (if any) isolated and examined by X-ray diffraction. Initiation of spontaneous calcium fluoride formation required a calcium fluoride ion-activity product of 10(-7.6) or more, 300 parts/10(6) fluoride were necessary to initiate calcium fluoride formation in neutral solution saturated with enamel, and the increased solubility of enamel apatite at low pH allowed calcium fluoride formation from solutions with as low as 100 parts/10(6) fluoride. When phosphate was present in the solution a competing apatite formation could mask the calcium fluoride formation. In neutral solutions saturated with respect to brushite, spontaneous fluorapatite formation was initiated by 100 pats/10(6) fluoride. With 200 parts/10(6) fluoride a further competing formation of calcium fluoride occurred.

Calcium Fluoride↗

PubMed1994

Dissolution of various calcium fluoride preparations in inorganic solutions and in stimulated human saliva.

The aim of the present study was to examine the dissolution of various preparations of calcium fluoride in inorganic solutions and in human saliva. Calcium fluoride was prepared by mixing either 0.25 or 0.02 mol/l calcium chloride with 0.5 or 0.04 mol/l sodium fluoride. After preparation, the salts were washed in 1 mmol/l calcium chloride solution and in distilled water. A commercial product, calcium fluoride Suprapur (Merck), was used for comparison. The solubility of the salts was examined in distilled water, in a 2-mmol/l sodium phosphate solution, and in whole human saliva, produced by chewing paraffin. It was found that the calcium fluoride ion product after suspension for 1-3 h in distilled water ranged closely around 10(-10.7) for all salts. In the phosphate solution, the commercial product dissolved slowly, the ratio between dissolved fluoride and calcium ranged from 4 to 7, in buffered solutions approaching 2. The supernatant was not saturated by the salt. Our two calcium fluoride salts dissolved quickly and made the phosphate-containing solutions supersaturated with respect to fluorapatite, leading to fluorapatite formation, and because of compensating calcium fluoride dissolution, this led to increasing fluoride concentrations in saliva of up to around 85-95 ppm. The results of this study indicate that calcium fluoride of less than Suprapur standard may dissolve quickly in saliva, unless the dissolution is retarded by a physical barrier, like a forming pellicle.

Apatites↗

PubMed1994

Dental tissue effects of fluoride.

It is now well-established that a linear relationship exists between fluoride dose and enamel fluorosis in human populations. With increasing severity, the subsurface enamel all along the tooth becomes increasingly porous (hypomineralized), and the lesion extends toward the inner enamel. In dentin, hypomineralization results in an enhancement of the incremental lines. After eruption, the more severe forms are subject to extensive mechanical breakdown of the surface. The continuum of fluoride-induced changes can best be classified by the TF index, which reflects, on an ordinal scale, the histopathological features and increases in enamel fluoride concentrations. Human and animal studies have shown that it is possible to develop dental fluorosis by exposure during enamel maturation alone. It is less apparent whether an effect of fluoride on the stage of enamel matrix secretion, alone, is able to produce changes in enamel similar to those described as dental fluorosis in man. The clinical concept of post-eruptive maturation of erupting sound human enamel, resulting in fluoride uptake, most likely reflects subclinical caries. Incorporation of fluoride into enamel is principally possible only as a result of concomitant enamel dissolution (caries lesion development). At higher fluoride concentrations, calcium-fluoride-like material may form, although the formation, identification, and dissolution of this compound are far from resolved. It is concluded that dental fluorosis is a sensitive way of recording past fluoride exposure because, so far, no other agent or condition in man is known to create changes within the dentition similar to those induced by fluoride. Since the predominant cariostatic effect of fluoride is not due to its uptake by the enamel during tooth development, it is possible to obtain extensive caries reductions without a concomitant risk of dental fluorosis.

Amelogenesis↗