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PubMed1992

Characterization of stable beryllium fluoride, aluminum fluoride, and vanadate containing myosin subfragment 1-nucleotide complexes.

Beryllium and aluminum fluorides are good phosphate analogues. These compounds, like orthovanadate, form stable complexes with myosin subfragment 1 (S1) in the presence of MgADP. The formation of the stable S1-nucleotide complexes is characterized by the loss of ATPase activity. For the complete loss of ATPase activity there was necessary a higher concentration of aluminum than of beryllium or vanadate. In the presence of MgATP the onset of the inhibition is delayed, which indicates that stable complexes cannot form when a specific site is occupied by the gamma-phosphate of ATP or by P(i) derived from the gamma-phosphate. The half-lives of the S1-MgADP-(BeF3-), S1-MgADP-(AlF4-), and S1-MgADP-Vi complexes at 0 degrees C are 7, 2, and 4 days, respectively. In the presence of actin the rate of decomposition of all of the complexes is significantly enhanced; however, the order of decomposition is reversed, the fastest rate being observed with beryllium and the slowest with aluminum. The formation of the S1-MgADP-(BeF3-) and S1-MgADP-(AlF4-) complexes is accompanied by an increase in tryptophan fluorescence similar to that observed upon addition of MgATP to S1. The fluorescence increase develops rather slowly, by suggesting that the rate-limiting step in the formation of the stable complex is an isomerization. The rate of the fluorescence change accompanying the formation of the Be complex is faster than that for the Al complex. Addition of vanadate to S1 causes a static quenching of the tryptophan fluorescence.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1990

Modulation of gamma-aminobutyric acid release in cerebral cortex by fluoride, phorbol ester, and phosphodiesterase inhibitors: differential sensitivity of acetylcholine release to fluoride and K+ channel blockers.

In this study we have used fluoride as a tool to investigate the involvement of G protein-coupled effector systems in the regulation of the depolarization-induced release of gamma-aminobutyric acid (GABA) from rat cerebral cortex. To distinguish among the activating effects of NaF on G proteins linked to different effectors, such as adenylate cyclase, polyphosphoinositide phospholipase C, and K+ channels, agents specific to these effectors have been used in parallel. NaF induced a marked dose-dependent facilitation of the K(+)-evoked release of [14C]GABA, with an EC50 of 1.26 mM, increasing release by 103% at 5 mM NaF. No effect on basal release was seen up to 3 mM NaF, and no modulation of [3H]acetylcholine (ACh) release was seen up to 5 mM NaF. Phorbol 12,13-diacetate (PDA) produced a similar dose-dependent facilitation of the K(+)-evoked release of [14C]GABA, potentiating the release of [14C]GABA by 50% at 10 microM PDA. The phosphodiesterase inhibitors, 3-isobutyl-1-methylxanthine (IBMX) and theophylline, inhibited the K(+)-evoked release of [14C]GABA, and IBMX reversed the NaF facilitation of GABA release in a dose-dependent manner (pA2 2.57). The K+ channel blocker (IA current) tetrahydroaminoacridine (THA), which markedly inhibits the K(+)-evoked release of [14C]GABA, also reversed the NaF facilitatory effect, but the release of [3H]ACh was less sensitive to the inhibitory effect of THA. On the other hand, the K+ channel blocker, tetraethylammonium, which has no effect on the release of [14C]GABA, caused a significant facilitation of K(+)-evoked release of [3H]ACh. From these studies, it is concluded that GABA release in cerebral cortex is subject to regulation by G protein-linked effector systems that are distinct from those affecting the release of [3H]ACh in cerebral cortex.

1-Methyl-3-isobutylxanthine↗
PubMed1981

Relationship between plasma, dentin and bone fluoride concentrations in rats following long-term fluoride administration.

A detailed knowledge of fluoride (F) pharmacokinetics is necessary if its pharmacologic and toxicologic effects are to be adequately understood. In the present study plasma F concentrations have been analysed using repeated blood samples taken from the ethmoidal sinus of rats given 25, 50, 100 and 150 p.p.m. F in drinking water ad libitum for 79 days. A close relationship between the F-concentration in the drinking water and plasma F concentrations was found. When the administration of F was stopped, a rapid decline in plasma F concentration was noted during 48 hrs in all groups. The plasma F concentrations in the 25 p.p.m. group returned to preexperimental levels but remained elevated in the other groups. The F concentrations of dentin and bone were determined and calculated on a dry fat free basis. The results show that there was a close relationship between plasma, bone and dentin concentrations.

Animals↗
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↗
PubMed1997

Salivary fluoride concentration and plaque pH after using a fluoride-containing chewing gum.

The aim was to study the salivary fluoride (F) concentration and plaque pH recovery on the chewing and the non-chewing side of the dentition during and after chewing 1 piece of chewing gum containing 0.25 mg F as NaF. Ten subjects refrained from toothbrushing for 3 days. On the fourth day, they rinsed for 1 min with 10 ml of a 10% sucrose solution. When plaque pH had reached a low value, they started to chew for either 5, 10, 15, 20, 30 or 45 min. Measurements of F concentration in saliva and of pH of approximal plaque were carried out at 2 contralateral sites for up to 60 min. In each individual, the chewing and non-chewing side were registered. Two to 3 times higher salivary F concentrations (expressed as area under the curve, AUC) were found on the chewing than on the non-chewing side (p < 0.05 or p < 0.01). The most pronounced recovery of plaque pH after the sucrose rinse was also registered for the chewing side, but the difference between the chewing and the non-chewing side was not so obvious as for the salivary F concentration. Significantly higher values of plaque pH (expressed as AUC) were found during prolonged chewing (p < 0.05 or p < 0.01), while only small numerical differences in salivary F concentration were noted between short and long chewing times. Thus, this study showed: (1) that the F concentrations in saliva after chewing a F-containing chewing gum were highest on the chewing side, and (2) that a prolonged chewing time increased the plaque pH recovery after a sucrose rinse, but had only a minor effect on the salivary F concentration.

Adult↗
PubMedDate not supplied

Effect of conditioning with fluoride and phosphoric acid on enamel surfaces as evaluated by scanning electron microscopy and fluoride incorporation.

The etching effect of 50% H-3PO-4 applied together with 2% NaF or SnF-2 was compared with the effect of H-3PO-4 on pre- and postfluoridated enamel by scanning electron microscopy. Substantial etching of enamel resulted with use of 50% H-3PO-4 with 2% NaF. High fluoride incorporation in the surface provided additional protection of the conditioned enamel.

Dental Enamel↗
PubMed1981

A study of in vivo fluoride uptake by dental tissues from fluoride-containing silver amalgams.

Teeth to be extracted for orthodontic reasons were filled in vivo with regular and fine-cut silver amalgams containing 1% and 5% SnF2. The teeth were extracted after 15 or 30 d, and the in vivo fluoride release and uptake by the dental tissues were studied using an electron microprobe analysis technique. The obtained results show that the use of SnF2 silver amalgams can be of potential value for minimizing caries adjacent to dental restorations.

Dental Amalgam↗
PubMed1985

Fluoride uptake and fluoride resistance in oral streptococci.

Fluoride uptake was examined in the highly F-sensitive Streptococcus salivarius strain 25975, the F-resistant mutant Flr103, and the relatively insensitive S. sanguis H7PR3. F was taken up by all strains from media at neutral pH, containing 1 or 10 micrograms F/ml (0.053-0.526 mmol/L), and uptake was directly proportional to the delta pH that was maintained by the cells. The final intracellular concentrations of F in the F-resistant strains were higher than those in the F-sensitive strain. Similar differences in F uptake were observed in buffer at pH 5.5, although both delta pH and F uptake were higher in all strains at the lower pH. These experiments demonstrate that resistance to F does not necessarily involve the exclusion of F from the cells. The lower uptake of F by F-sensitive cells is attributed to the finding that F dissipates the transmembrane pH gradient, and this, in turn, limits the concentration of intracellular F.

Cell Membrane↗
PubMed1987

A comparison of the effects of continuous and periodic fluoride delivery on fluoride levels in plasma, enamel, and bones of nursing rats.

The purpose of this study was to determine and compare the F levels in plasma, enamel, and bones of nursing rat pups that received the same daily dose of F by continuous or periodic delivery during enamel development. The hypothesis was that F delivered continuously would result in enamel F levels higher than those attained when F was delivered periodically. For continuous delivery, copolymer devices (Southern Research Institute) that provide slow release of F were implanted in the backs of four-day-old rat pups. For periodic delivery, rat pups received F by intraperitoneal injection or gastric intubation. The doses were 0.01, 0.02, or 0.04 mg F/day. The rats were killed at 13 days of age, 24 hours after the last periodic delivery. Plasma was collected, femur and calvaria bones were removed, and enamel was scraped from developing first molars. Fluoride assay was by the microdiffusion method of Taves, with a F electrode. For the 0.02 mg F/day dose, plasma levels in control, implanted, injected, and gastric-intubated rats were 0.004, 0.020, 0.011, and 0.009 ppm, respectively. Enamel F levels were 1.1, 61.9, 54.0, and 42.3 ppm, respectively. Femur F levels were 2.2, 81.2, 84.8, and 68.1 ppm, respectively. Calvaria F levels were 2.5, 79.3, 80.1, and 67.9 ppm, respectively. The results showed that there was no significant difference in the enamel F levels or in the bone F levels in rat pups that received continuous or periodic, by injection, delivery of F at the same daily dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Amelogenesis↗
PubMed2005

Low-fluoride dentifrice and gastrointestinal fluoride absorption after meals.

A low-fluoride (F) dentifrice has been recommended to reduce the risk of dental fluorosis, but its anti-caries efficacy is questionable compared with that of conventional dentrifices (1000-1100 microg F/g). The tested hypothesis was that conventional dentifrices might be safe if used soon after meals, since food interferes with F absorption. In a crossover, double-blind study, 11 volunteers ingested a dentifrice slurry containing 0 (placebo), 550 (low F), or 1100 microg F/g in 3 gastric content situations: on fasting, or 15 min after breakfast or lunch. F was analyzed in saliva and 24-hour urine samples. The conventional dentifrice ingested after lunch resulted in only 10% higher F absorption than the low-F ingested on fasting. Analysis of the data suggests that the risk of fluorosis could be reduced by the use of either a low-F dentifrice or a conventional dentifrice, if toothbrushing occurred soon after meals.

Absorption↗
PubMed2005

Effect of topical fluoride and fluoride varnish on in vitro root surface lesions.

PURPOSE: To evaluate the effect of a fluoride varnish on demineralization and remineralization of root surfaces in vitro. METHODS: 80 caries-free teeth were selected from a large pool of extracted anterior and premolar teeth from elderly patients. Acid resistant nail varnish was painted on all surfaces except for a window (l x 4 mm) on the buccal or lingual root surfaces. Teeth were randomly divided into four treatment groups: CONTROL: washed with deionized/distilled water; Daily gel: treated with Karigel-N (5,000 ppm) for 4 minutes daily; Weekly gel: treated with Karigel-N for 4 minutes weekly; and Weekly varnish: treated with Duraflor (22,600 ppm) weekly (the varnish was removed 24 hours after each application). Teeth were then placed in a cycle of demineralization (6 hours at pH 4.3) and remineralization (17 hours at pH 7.0) for 21 days. Half the specimens of each group were brushed with no dentifrice for 10 seconds twice daily. Specimens were evaluated under polarized light microscopy and contact microradiography. The depth of each lesion and width of the remineralization bands were measured. An ANOVA model was used to assess the effect of different treatments. RESULTS: The control group had the deepest lesions and the daily gel group had the shallowest lesions. The weekly varnish group was found to have significantly shallower lesions than the weekly gel group. The varnish brushing subgroup had significantly deeper lesions than varnish non-brushing subgroup (P = 0.01). Remineralization bands were detectable in most lesions. There was no significant difference in band width between different groups (F = 0.634, P = 0.594). However, a significant difference was found when remineralization bands were calculated as percentage of lesion depth between different groups (F = 4.24, P = 0.001). The varnish non-brushing subgroup had significantly higher percentage than the control group, but daily gel non-brushing had the highest percentage. Brushing was a significant factor in the varnish group. Lesions were significantly shallower in the non-brushing varnish subgroup.

Aged↗
PubMed2005

Prevalence of enamel defects and MIH in non-fluoridated and fluoridated communities.

AIM: This was to study the prevalence of enamel defects and molar incisor hypomineralisation (MIH) in children attending Leeds Dental Institute (UK) and Westmead Dental Hospital, Sydney (Australia). METHODS: Prospective dental examinations were carried out on 25 children referred to two orthodontic departments. A questionnaire was completed to obtain background information and about previous fluoride (F) exposure followed by an oral examination. First permanent molars and permanent incisors were examined for presence, type and severity of enamel defects using the modified DDE screening index. Chi square tests were used to compare results. RESULTS: Data for 24 children in Sydney and 20 in Leeds presented with at least one enamel defect. Of 300 teeth examined, 155 in Sydney and 82 in Leeds had a defect (p < 0.005). Severity of enamel defects was higher in Sydney. The children presenting with any type of enamel defect in at least one incisor or molar were 21 in Sydney and 10 in Leeds. However, if only demarcated defects were considered, the number in Sydney dropped to 11 and in Leeds remained at 10. CONCLUSIONS: There was a higher prevalence of enamel defects in those children living in F Sydney than in non-F Leeds, but the prevalence of MIH was the same supporting the view that F is not associated with the aetiology of MIH.

Adolescent↗
PubMed1990

Longitudinal study of dental caries prevalence and incidence in the rapakivi (high fluoride) and olivine diabase (low fluoride) areas of Laitila, Finland.

This paper is a continuation of the author's study published in 1975. The teeth of the school children included in the study were first examined in 1952, re-examined in 1972 and subsequently at 5-year intervals. Children in the village of Salo had drinking water with a high fluride content and those in the village of Suontaka drank water with a low fluoride content. In the first examination, the Salo children showed a caries prevalence, measured with the DMF inxed, ca. 67% lower than the Suontaka children. With some exceptions, such as the first molars, the absolute differences in caries prevalence between subjects from the two villages had remained practically the same throughout the years. By the 1987 examination, the difference had been reduced, measured with the DMF index, to about 23% and with the DMFS index, to about 28%. In the last 5 years (1982-87), the DMFS index of the Suontaka pupils increased by 2.5 and that of the Salo pupils by 4.1. In the preceding two 5-year periods the increment in each group was ca. 7.0%.

Adult↗
PubMed1994

The effect of soft laser irradiation on fluoride release of two fluoride-containing orthodontic bonding materials.

Laser technology offers new treatment possibilities in dentistry. The effect thereof on dental biomaterials is however not yet known. Two fluoride (F) containing orthodontic bonding materials were investigated in this study. Group A = FluorEver OBA (Macro Chem) and group B = Light-Bond (Reliance Orthodontic Prod. Inc.). A galium arsenide aluminium (Ga As Al) low level laser with an energy transmission of 5.45 J (30 mW for 180 seconds) and an energy density of 27.54 J/cm" was used to irradiate the orthodontic bonding materials. SEM evaluation showed that the laser irradiation had no superficial physical ultrastructural effects on either of the two materials. In addition, the F release of Group A could be enhanced for up to seven months by a sole laser treatment (p < 0.05). Although the F release in the lased Group B was also higher, it was not statistically significant (p > 0.05). The difference in the F release of the two materials after laser irradiation may be due to differences in the composition of the orthodontic bonding materials, but cannot be adequately explained.

Dental Cements↗