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PubMed1989

Enamel fluoride and caries in Icelandic children and a comparison of enamel fluoride in Swedish and Icelandic children.

The fluoride content in surface enamel and its relationship to caries experience was studied in a group of Icelandic schoolchildren living in a low-fluoride area. Fluoride content was assessed by means of in vivo enamel biopsies sampled from 248 subjects aged 11 and 12 years. Dental examinations were performed in conjunction with the biopsy sampling and by the same examiner 1 year later. The prevalence and incidence of initial (DSI) and manifest (DFS) caries lesions were recorded separately. A median fluoride concentration of 610 ppm at a median biopsy depth of 4.2 microns was observed. A significant positive correlation was found between DSI and enamel fluoride content in girls and all older children. Additionally, surface enamel fluoride was measured in 72 Swedish children from a low-fluoride area but exposed to regular topical fluoride treatments. The difference in mean fluoride concentrations between the Icelandic and Swedish study populations was highly significant. From the measured fluoride concentrations the enamel fluoride profiles for both study populations were constructed. The differences in fluoride content were most pronounced in the outermost layer, apparently reflecting the higher exposure to and acquisition of topical fluoride in the Swedish children.

Age Factors↗
PubMed1997

The cessation of fluoridated water administration and the fluoride distribution profiles in rat molar cementum.

The aim of this work was to obtain further information about the origin of fluoride profiles in cementum. Fluoride was administered to rats at varying doses (0.50, 100 ppm F in drinking water) and for different durations (4, 13 and 25 weeks). Fluoride distribution across the full thickness of molar cementum in rats was measured by means of an abrasive micro-sampling technique. The average fluoride concentrations in cementum increased significantly with increasing dose and duration of fluoride administration. The relative reduction of the average fluoride concentrations after cessation of fluoride administration was 94.2-36.5% at 50 ppm F and 62.2-49.2% at 100 ppm F in the outer layers (1-60 microns) and 91.5-24.1% at 50 ppm F and 74.1-7.6% at 100 ppm F in the middle (61-120 microns) layers of the cementum, respectively. The reduction rates were more closely related to the time intervals following cessation rather than fluoride concentrations in drinking water or specificity within the cementum. Two factors which may influence this are new cementum formation after withdrawal of fluoride and some fluoride release from cementum surfaces when the fluoride supply stopped. It was concluded that the cessation of fluoride administration reduced the fluoride concentration on the outer layers of cementum differing from bone where reduction occurs across the entire thickness.

Analysis of Variance↗
PubMed1986

Fluoride absorption: independence from plasma fluoride levels.

The concept that there are physiologic mechanisms to homeostatically regulate plasma fluoride concentrations has been supported by results in the literature suggesting an inverse relationship between plasma fluoride levels and the absorption of the ion from the gastrointestinal tract of the rat. The validity of the relationship was questioned because of possible problems in the experimental design. The present work used four different methods to evaluate the effect of plasma fluoride levels on the absorption of the ion in rats: (i) the percentage of the daily fluoride intake that was excreted in the urine; (ii) the concentration of fluoride in femur epiphyses; (iii) the net areas under the time-plasma fluoride concentration curves after intragastric fluoride doses; and (iv) the residual amounts of fluoride in the gastrointestinal tracts after the intragastric fluoride doses. None of these methods indicated that plasma fluoride levels influence the rate or the degree of fluoride absorption. It was concluded that, unless extremely high plasma fluoride levels are involved (pharmacologic or toxic doses), the absorption of the ion is independent of plasma levels. The results provide further evidence that plasma fluoride concentrations are not homeostatically regulated.

Absorption↗
PubMed2002

Fluoride release and caries inhibition associated with a resin-modified glass-ionomer cement at varying fluoride loading doses.

PURPOSE: To measure, over time, the release of fluoride from a resin-modified glass-ionomer cement, loaded with different levels of fluoride, then to evaluate the adjacent dentin demineralization inhibition relative to these fluoride levels. MATERIALS AND METHODS: (Phase I) 25 standardized discs were fabricated from a non-fluoridated resin-based composite (control), resin-modified glass-ionomer cement and resin-modified glass-ionomer cement loaded with sodium fluoride at 1%, 2% and 3% by weight fluoride. Fluoride release was evaluated over 30 days. (Phase II) 50 restorations, from the materials listed in Phase I, were placed as Class V restorations in teeth, the teeth were acid-challenged, then dentin margins adjacent to restoration margins were evaluated for demineralization. RESULTS: As sodium fluoride additions increased, fluoride release increased. Evaluation of demineralization indicated the resin-modified glass-ionomer cement inhibited adjacent demineralization in a direct relationship with sodium fluoride concentration where 3% fluoride exhibited significantly less adjacent demineralization than all other groups; 2% and 1% fluoride exhibited significantly less adjacent demineralization than the non-loaded resin-modified glass-ionomer cement and non-fluoridated resin-based composite control (P< 0.05).

Acid Etching, Dental↗
PubMed2006

Surface microhardness changes, enamel fluoride uptake, and fluoride availability from commercial toothpastes.

OBJECTIVE: The aim of the present study was to evaluate the ability of a new fluoride-containing dentifrice to protect surface-softened enamel against further erosive challenges in an in vitro cycling model, and to relate any effects to enamel fluoride uptake (EFU) and free fluoride. METHODOLOGY: Human enamel specimens were subjected to a daily cycling regimen comprising: three two-minute treatments; five two-minute challenges using 1% citric acid pH 3.8; and remineralization in a mixture of human saliva and mucin-containing artificial saliva. Surface microhardness (SMH) was measured at baseline, 10, and 20 days, and the fluoride content of biopsied specimens determined at 20 days. EFU studies were based on method #40 described in the United States Food and Drug Administration (FDA) testing procedures. Free-fluoride availability was determined from slurries of one part toothpaste plus three parts deionized water. RESULTS: SMH showed that a 1150 ppm NaF test dentifrice protected enamel specimens greater than Crest Cavity Protection (1100 ppm NaF) and a fluoride-free placebo at both 10 days and 20 days (p < 0.05). The fluoride content of specimens treated with this prototype was higher than either Crest or the placebo. SMH for a 1450 ppm NaF test dentifrice was greater than for Elmex Sensitive (1450 ppm amine F) and placebo at 10 days, while both products were greater than the placebo at 20 days. The fluoride content of specimens treated with this test dentifrice was higher than Elmex Sensitive, which was higher than placebo. The fluoride uptake seen in the cycling model correlated for the NaF dentifrices with a standard EFU procedure. Different EFU results for a series of commercial dentifrices demonstrated that EFU is not necessarily a function of free-fluoride availability. CONCLUSION: This study demonstrated that fluoride dentifrices can increase the protection of enamel against an erosive challenge in vitro, and that the increased protection correlated with fluoride uptake. The fluoride uptake seen in the cycling model correlated with a standard FDA EFU procedure for the NaF dentifrices. The present studies demonstrate the importance of formulation effects on driving performance in in vitro models.

Cariostatic Agents↗
PubMed1989

[Value of bone fluoride determination in osteoporotic patients treated with sodium fluoride].

In order to find out whether the response of osteoporosis to sodium fluoride treatment or complications arising from this treatment are related to the retention of fluoride in bones, we measured bone fluoride concentrations in 30 patients with primary osteoporosis who had been treated with sodium fluoride for 1 to 8 years. We found a significant correlation (r = 0.74, P less than 0.001) between bone fluoride concentration and total amount of fluoride ingested. However, with any given amount of sodium fluoride, the bone fluoride concentration could vary by up to three times from a patient to another. There was a significant correlation between bone fluoride concentration and trabecular bone volume on the hand (r = 0.54, P less than 0.001) and thickness of osteoid borders measured on the same biopsy specimen on the other hand (r = 0.45, P less than 0.001). Five patients developed lower limb bone fissures after 11 to 18 months of sodium fluoride treatment, but their bone fluoride concentration was not significantly different from that of the 25 patients who had no fracture. These data suggest a relationship between the degree of stimulation of bone formation by fluoride and the bone concentration of that substance; however, peripheral fractures are not dependent on bone fluoride concentration.

Adult↗
PubMed1989

[Fluoride retention and clearance after rinsing with fluoridated mouthwashes].

Oral fluoride clearance and oral fluoride retention were studied in 12 adult volunteers. 5 different mouthrinses were used. The test agents, in part available on the market, includes two Candida mouthrinses containing 1508 and 330 ppm F, respectively, Act containing 308 ppm F, a zinc fluoride-hexetidine (ZH) combination containing 287 ppm F, and an amine fluoride 297/SnF2 (AmF/SnF2) combination containing 241 ppm F. The volunteers rinsed with 10 ml of the above solutions for 30 s each. The oral fluoride concentration was reduced to 1 ppm 99 min after rinsing with Candida original. With the AmF/SnF2 solution, the oral fluoride concentration remained above 1 ppm for 39 min, and for about 20 min after rinsing with Candida reduced, ZH and Act. With both Candida original and ZH significant fluoride levels in the oral fluid were still found after 3 h, while with AmF/SnF2 and Act significant fluoride levels lasted for 2 h. A specific clearance value was determined for each mouthrinse, reflecting the ability of the agent to remain attached to the oral structures. The AmF/SnF2-rinse had a rapid clearance value. About 9 to 17% of the fluoride brought into the oral cavity were not expectorated. For the mouthrinses containing 0.05% NaF the retention was about 0.4 mg F. This value is considered to be harmless. Mouthrinses used after the application of a monofluorophosphate-dentifrice helped to increase the relatively low oral fluid fluoride level. Rinsing with the test agents after brushing with the amine fluoride dentifrice (Elmex) produced no significantly increased fluoride levels. In-between meals eliminated the oral fluoride concentration rapidly.

Adult↗
PubMedDate not supplied

Fluoride release from fluoride-containing materials.

This in vitro study evaluated the amount of fluoride released from fluoride-containing materials over a period of 28 days. Six disk samples (2.06 +/- 0.06 cm2) were prepared of each material and divided at random into seven groups: Group 1: Chelon-Fil; Group 2: Chelon-Silver; Group 3: VariGlass; Group 4: Dyract; Group 5: Vitremer; Group 6: Vitremer + Scotchbond Multi-Purpose; Group 7: Fuji II LC. The cements were mixed according to the manufacturers' recommendations, placed in plastic molds, and pressed between two glass plates. Paraffined dental floss was incorporated into the cements during setting to serve as attachments. The materials in Groups 3, 4, and 5 were light cured (Heliolux) in two different positions for 40 seconds each. In Group 6, the adhesive was light cured in two different positions on both sides for 10 seconds each. The samples were stored at 100% relative humidity for 24 hours. Each sample was then suspended in individual plastic tubes containing 5 ml of deionized water and submitted to constant agitation at 25 degrees C. The water was changed every 24 hours. Fluoride release was determined at 1, 2, 3, 4, 5, 7, 14, and 28 days after buffering the solution with equal volume of TISAB. Fluoride release was measured with a fluoride ion-specific electrode (Orion 96-09) and an ionanalyzer (Orion EA 940) previously calibrated with standard solutions containing 0.05 to 5.00 micrograms F/ml. Fluoride release was expressed as ppm in solution and micrograms F/cm2. ANOVA and Student-Newman-Keuls tests were used to evaluate the data. The results revealed that Chelon-Fil released significantly (P < 0.001) more fluoride for the first 7 days than all the other products. This was followed by Fuji II LC, which exhibited significantly more fluoride release than the rest of the materials for the same 7 days. At days 14 and 28, Chelon-Fil, Dyract, and Fuji II LC released similar amounts of fluoride that were significantly greater than the other products. Group 6 (Vitremer + Scotchbond Multi-Purpose) released significantly less fluoride than the other materials at all time intervals. Fluoride release for all products at days 1 and 2 was significantly greater than the rest of the time intervals, except for Chelon-Silver, which released similar amounts of fluoride for days 2, 3, 4, and 5. Although significance for the remaining time intervals varied for all materials, all fluoride release decreased from day 1 to day 28.

Acrylic Resins↗
PubMedDate not supplied

[Incidence of caries in the Canton Waadt (Vaud) after the change from fluoride tablets to fluoridization of salt].

This report shows results of a survey on dental caries in the Canton of Vaud in the years 1970 and 1974. In this canton fluoridation was carried out by means of fluoride tablets distributed at school until 1969/70 and in subsequent years by adding 250 mg F/kg fluoride to domestic salt. For comparison, results from adjoining and other cantons are also presented. In 1970 the 3 communities in the Canton of Vaud (Moudon, Grandson and Vevey) showed a remarkably low overall caries level due to the distribution of fluoride tablets, supplemented in Grandson with regular brushings with fluoride solution. When the fluoride tablets were discontinued in 1968/70 and fluoridated domestic salt containing 250 mg F/kg NaCl was introduced, caries incidence reached an even lower level. In these 3 communities caries prevalence fell to the lowest level reached, so far, by means of preventive measures in Bettlach (Canton of Solothurn, toothbrushing with fluoride solutions 6 times per year combined with information, fluoride tablets on every school day, and in addition consumption of table salt fluoridated at a suboptimal level of 90 ppm). The children in the control communities Romont (Canton of Fribourg), St-Aubin (Canton of Neuchâtel) and Châtel-St-Denis (Canton of Fribourg) also showed decreases of caries levels from 1970 to 1974. This decrease can be attributed to the distribution of fluoride tablets started at the schools of this community in the late sixties. Caries incidence in the age spans 8 to 12 and 10 to 14 years was estimated. Children from the Canton of Vaud where fluoridated table salt was practically the only preventive measure showed a smaller DMF increase than those from the cantons Fribourg and Neuchâtel. By means of a method combining DMF means of various age groups it was possible to obtain sufficiently large numbers of children for a study of the caries prevalence in each community. All communities showed a decrease of caries levels. In the Canton of Vaud this reduction started at a lower initial level and in 1974 reached consistently lower values than those of the control communities of the cantons of Fribourg and Neuchâtel.

Adolescent↗
PubMed1995

Fluoride retention of incipient enamel lesions after treatment with a calcium fluoride varnish in vivo.

The aim was to determine the fluoride retention in plaque-covered and clean incipient enamel lesions after topical application of a CaF2/NaF varnish (Bifluorid 12). In 50 specimens of bovine enamel an incipient lesion was produced with acidic hydroxyethylcellulose (pH 4.8; 72 h). 40 specimens were fluoride varnished; the 10 remaining specimens were used for measuring baseline fluoride content. Each six of the fluoridated specimens were recessed in the buccal aspects of an intraoral appliance worn for 5 days. During the experimental period one side of the appliance was kept clean, and plaque growth was allowed on the other. KOH-soluble and structurally bound fluoride were determined immediately, 1 day, 3 days and 5 days after fluoridation, and compared with the baseline fluoride content of the enamel. Immediately after fluoridation, a considerable amount of KOH-soluble fluoride was bound, but after 5 days 80% had been lost. Simultaneously a significant increase of non-KOH-soluble or structurally bound fluoride was detected in both plaque-covered and clean enamel. It is evident that this CaF2/NaF varnish deposits more KOH-soluble fluoride on the surface of demineralized enamel than other varnishes, but after 5 days fluoride retention is similar to that from other varnishes.

Analysis of Variance↗
PubMed2006

Relationship between daily fluoride intake from diet and the use of dentifrice and human plasma fluoride concentrations.

The literature contains reports of the relationship between the fluoride concentrations in drinking water and human plasma. None of these studies, however, documented individual levels of daily fluoride intake, which can vary considerably among individuals served by the same water supply. Furthermore, while water can be an important source of fluoride, other sources, especially fluoridated dentifrices, also contribute substantially. This 2-day study with five 25-35-year-old subjects in each of three communities (Bauru, 0.6-0.8 ppm F; Domelia, 0.7 ppm F; Floresta, 0.3 ppm F) determined plasma fluoride concentrations and fluoride intake from diet and the use of dentifrice which, together, approximate total daily fluoride intake. The purposes were to determine: (1) the extent to which plasma fluoride concentrations approached levels known to affect the quality and quantity of bone; (2) the relationship between fluoride intake and plasma concentrations. Plasma was collected at 4-h intervals starting at 0800 h and ending at 2000 h each day. Average fluoride intakes from diet and the use of dentifrice in the three communities ranged from 0.16 to 0.82 mg/day and from 0.29 to 3.16 mg/day, respectively. The overall average plasma concentrations in the three communities were 0.44, 0.45 and 0.54 micromol/l (P<0.005). They were directly related to intake from the use of dentifrice (P=0.030) and to total intake (P=0.033), but were not related to dietary intake (P=0.176). In conclusion, despite fluoride intake from various sources, the plasma fluoride concentrations of the study subjects remained at levels far below those associated with effects on bone production.

Adult↗
PubMed2001

Analysis of fluoride levels retained intraorally or ingested following routine clinical applications of topical fluoride products.

A variety of topical fluorides is now used clinically for the prevention and control of dental caries. It is essential for the dental profession to be fully aware of the relative retention rates of fluoride in saliva and thus its contact with the teeth. These may vary following the use of the different categories and concentrations of agents available and with different methods of use. It is also important to be aware of the amounts of fluoride ion ingested following use of the more concentrated forms and of the resultant elevation in total blood fluoride levels. These parameters were investigated in a series of experiments involving human volunteer subjects using a variety of topical fluoride materials commercially available in Australia. Fluoride mouthrinses appeared to provide the highest salivary retention rates per dose of all forms of topical fluoride. Ingestion rates from concentrated gels were acceptable when effective evacuation methods were applied. The use of custom-made trays resulted in a reduction in amounts of fluoride ion ingested, though simple self-application by toothbrush of smaller quantities proved to be an effective alternative in terms of amount of fluoride ion retained in saliva per amount applied and ingested. None of the concentrated gels used resulted in elevations in total blood fluoride levels which were of concern in adults. It is acknowledged that salivary retention rates of fluoride ion do not necessarily reflect the caries inhibitory effects of topical fluorides. However, these data provide some indication of possible advantages of some products and methods of application over others.

Adult↗
PubMedDate not supplied

A probabilistic estimation of fluoride intake by infants up to the age of 4 months from infant formula reconstituted with tap water in the fluoridated regions of Ireland.

Two probabilistic models were developed to estimate the acute and chronic exposure to fluoride of exclusively formula-fed infants aged 0-4 months as a result of the consumption of infant formula reconstituted with fluoridated tap water in Ireland. The estimates were based on calculated infant formula consumption and accepted body weight standards, together with reported concentrations of fluoride in infant formula powder and measured values for the fluoride content of water in Ireland. The mean acute exposure of infants to fluoride on any single day in areas served by 387 fluoridated water supplies was estimated to be between 0.11 and 0.14 mg/kg body weight depending on age group (95th percentiles 0.2 and 0.26 mg/kg b.w., respectively). These predicted intakes were well below the intake of fluoride associated with acute toxic effects, which is considered to be 5 mg fluoride (F(-))/kg body weight. The mean chronic exposure of infants to fluoride was estimated to be between 0.106 and 0.170 mg/kg b.w./day depending on body weight (95th percentiles 0.108 and 0.172 mg/kg b.w./day, respectively). This estimate described the average daily fluoride intake of infants during the first 4 months of life residing in the areas served by 226 water supplies that achieved an average yearly fluoride concentration below 1.03 mg/l. Dental fluorosis may be considered to be the only risk at these low doses and from our work it is estimated that there is a very low risk of moderate dental fluorosis of the permanent dentition in infants exposed to fluoride at these levels.

Age Factors↗
PubMed1988

Caries prevalence and length of residency in fluoridated and non-fluoridated communities.

The caries experience of grade 6 Canadian schoolchildren was examined related to length of residence in non-fluoridated Camrose (0.23 ppm) and adjacent fluoridated Wetaskiwin (1.08 ppm). The mean age was 11.94 +/- 0.65 years, 115 being examined in Camrose and 89 in Wetaskiwin. The mean DMFT and DMFS values were similar in both the non-fluoridated and fluoridated communities with DMFT of 2.39 and 2.65 and DMFS of 3.40 and 3.54, respectively. When a minimum 5-year residency requirement was imposed, the data changed, showing for those children with 5-year residency DMFT values of 2.43 and 2.26 and DMFS values of 3.35 and 2.79, respectively, for non-fluoridated Camrose and fluoridated Wetaskiwin. Although the fluoridated community had 17% less surfaces with caries, differences between the fluoridated and non-fluoridated communities were not statistically significant. Within the fluoridated community, differences in DMFT and DMFS between children resident less than 5 and greater than 5 years were statistically significant (DMFT p less than 0.05; DMFS p less than 0.01). When comparing regions where adjacent communities exist, with and without water fluoridation, and in making decisions on fluoride supplementation levels for children who have changed residency to such communities, it is important that this type of information is taken into account.

Alberta↗
PubMed1996

Fluoride content of the enamel and dentine of human premolars prior to and following the introduction of fluoridation in New Zealand.

The fluoride content of the enamel and dentine of premolars was used as a determinant of the availability of ingested fluoride in New Zealand prior to and following the introduction of water fluoridation 40 years ago. Premolar teeth, which developed during the periods (PRE and POST respectively) under study, were selected from teeth extracted from 12 to 14-year-old children resident in different geographic areas in the country. The fluoride content, determined by multiple proton microprobe analyses, of surface enamel, deep enamel, and dentine, were for PRE teeth 440, 65 and 115, respectively. For POST teeth the mean values were significantly (p<0.001) higher, by 69, 29 and 102% respectively. The relevance of the change in fluoride content was assessed by comparison with published reports on the fluoride content of teeth developed in communities exposed to low (<0.5 ppm), optimal (1-2 ppm) and high (>3 ppm) naturally occurring fluoride levels in drinking water. The PRE teeth had a fluoride content associated with a low fluoride exposure and POST teeth with optimal fluoride exposure during tooth development. It was concluded that fluoride availability in New Zealand teeth had increased over the past 30 years but this increase is compatible with exposure of the community to optimal rather than excessive levels of ingested fluoride.

Adolescent↗
PubMed1991

Formation of fluoride on enamel in vitro after exposure to fluoridated mouthrinses.

The aim of this study was to quantify the formation of alkali-soluble fluoride (loosely bound fluoride such as calcium fluoride-like material and absorbed fluoride) and alkali-insoluble fluoride (firmly bound fluoride or apatitically bound fluoride) when fluoride mouthrinsing solutions were applied on sound human enamel in vitro. Two commercial products containing 0.2% or 0.05% NaF were used during 30 sec, 60 sec, 5 min, and 60 min. The formation of loosely bound fluoride was determined by KOH extraction and visualized by scanning electron microscopy. The firmly bound fluoride was measured by three consecutive acid etchings of the enamel. Even during short periods of application there were deposits on the enamel surface. The amount of deposit increased with time of exposure to the 0.2% NaF solution. Only after treatment for 60 min with 0.05% NaF were significant amounts of alkali-soluble fluoride deposited. No measurable amounts of firmly bound fluoride were observed.

Calcium Fluoride↗
PubMedDate not supplied

Fluoride release and uptake capacities of fluoride-releasing restorative materials.

Many fluoride-releasing dental materials are being sold on the basis of their cariostatic properties. However, the amount fluoride release of these materials is still uncertain. This study investigated the fluoride release and uptake characteristics of four flowable resin composites (Heliomolar Flow, Tetric Flow, Wave, Perma Flo), one flowable compomer (Dyract flow), one conventional glass ionomer cement mixed with two different powder/liquid ratios (ChemFlex Syringeable and ChemFlex Condensable), one packable resin composite (SureFil), one ion-releasing composite (Ariston pHc) and one resin-modified glass ionomer cement (Vitremer). Seven discs (6-mm diameter and 1.5-mm height) were prepared for each material. Each disc was immersed in 3.5 ml of deionized water within a plastic vial and stored at 37 degrees C. The deionized water was changed every 24 hours and the release of fluoride was measured for 30 days. At the end of this period, the samples were recharged with 2 ml of 1.23% acidulated phosphate fluoride (APF) gel for four minutes. Then, all samples were reassessed for an additional 10 days. The fluoride release of all samples was measured with a specific fluoride electrode and an ionanalyzer. Statistical analyses were conducted using two-way repeated measure ANOVA and Duncan's multiple range tests. For all tested materials, the greatest fluoride release was observed after the first day of the study (p<0.01) but gradually diminished with time. During the test period, Tetric Flow released the lowest amount of fluoride; however, no statistically significant difference was found from Wave and Heliomolar Flow (p>0.05). Ariston pHc released the highest amount of fluoride, followed by ChemFlex Syringeable, Vitremer and ChemFlex Condensable. There were statistically significant differences among these materials (p<0.05). Fluoride release of all materials were significantly increased after the first day following refluoridation and Ariston pHc released the greatest among all materials (p<0.01). At the end of two days of refluoridation, the fluoride release rate for each material dropped quickly and stabilized within three days.

Acidulated Phosphate Fluoride↗
PubMed1979

Industrial fluoride pollution. Chronic fluoride poisoning in Cornwall Island cattle.

An aluminum plant on the south bank of the St. Lawrence river, southwest of Cornwall Island, Ontario, Canada, has emitted 0.816 metric tons of fluoride daily since 1973; considerably higher amounts were emitted from 1959 to 1973. The plant has been designated as the "major source of fluoride emissions impacting on Cornwall Island." Chronic fluoride poisoning in Cornwall island cattle was manifested clinically by stunted growth and dental fluorosis to a degree of severe interference with drinking and mastication. Cows died at or were slaughtered after the third pregnancy. The deterioration of cows did not allow further pregnancies. Fluoride concentrations in ash of biopsied coccygeal vertebrae increased significantly with age and were dependent on distance from and direction to the aluminum plant. Fluoride in bone ash of a 7-month old-fetus exceeded 500 ppm; fluoride thus was passed transplacentally. Analyses of fluoride in ash of bones obtained at necropsy of cattle from 4 months of age to 4 to 5 years of age showed increased amounts with age. Cancellous bone retained far higher amounts than cortical bone, a reflection of the normally higher metabolic rate of cancellous bone. Concentrations exceeding 10,000 ppm fluoride were recorded in cancellous bone of a 4-to 5-year-old cow. The target cells for fluoride in chronic fluorosis were shown to be the ameloblasts, the dental pulp cells and the odontoblasts and, in bone, primarily the resorbing osteocytes and also the osteoblasts. Atrophy and necrosis of the ameloblasts were responsible for enamel defects. The existing enamel showed brown discoloration from fluoride deposits. The pulp cells underwent fibrous and osseous metaplasia and necrosis of the ectopic bone occurred. The odontoblasts were atrophic and the dentin showed brown discoloration. The resorbing osteocytes were inactive and osteosclerosis resulted. This was especially pronounced in areas of normally great apposition, i.e. in the metaphyses. The epiphyseal plate became squeezed between petrotic bone and growth was stunted. Resorption of alveolar bone surrounding the deciduous teeth was severely retarded or arrested. A delay in eruption of permanent teeth occurred; it was up to 3.5 years in incisor teeth. Interference with the resorbing osteocytes in fluorotic bone was also demonstrated by loss of collagen birefringency in such bone. Failure of bone resorption also caused retention of trabecular bone in the cortices; this was observed even in a 4-t0-5-year-old cow. In areas where modeling into osteonic bone had begun, fluoride deposits were extremely heavy but this bone showed numerous soft osteons in microradiographs. The toxic effect of fluoride on osteocytes also resulted in the death of the cells. Such osteonecrosis occurred mainly in gnathic bone. There was atrophy of the osteoblasts. Osteopenia thus resulted from osteonecrosis and osteoporosis. Subperiosteal exostoses were not observed in long bones. The degree of fluorosis in Cornwall Island cattle was severe...

Air Pollutants↗