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As the use of adhesive restorative materials has increased during the last several years, interest in adhesive materials that release fluoride has also grown. The purpose of this study was to measure fluoride release from several adhesive restorative materials and to evaluate its effect on dentin resistance to demineralization and on bacterial metabolism in a modified in vitro system. Standardized cavities (1.8 mm in diameter) were prepared in bovine teeth that had been ground to dentin. One cavity in each tooth was restored with one of the following restorative systems: (a) Single Bond and Z100; (b) Single Bond and Tetric Ceram; (c) Fuji Bond LC and Z100; (d) Fuji Bond LC and Tetric Ceram; (e) Fuji II LC; or (f) Fuji IX GP. The other cavity in each tooth was "restored" with wax as a control. For each restorative system, 12 specimens were evaluated for fluoride release during the first 24 hrs after restoration placement. Dentin adjacent to the restored sites was subjected to lactic acid challenge (pH 4.3) for 3 hrs, after which calcium release was measured. Another 12 specimens in each group were stored for 24 hrs in de-ionized water, and were exposed to an S. mutans suspension (1:1 THB/de-ionized water and 50 mM glucose, A660 = 0.2) for 6 hrs, followed by calcium release and pH measurement. Bulk specimens of each material were also made and stored in water. Fluoride released from Fuji Bond LC, Fuji IX GP, and Fuji II LC in bulk was significantly greater than from the other materials. In the restored dentin specimens, increased resistance to demineralization from a lactic acid challenge was directly related to fluoride release. The same effects were seen as a result of the S. mutans challenge. While fluoride release from restorative materials increased the resistance of dentin to demineralization in this system, the clinical relevance of the findings is not known. [ABSTRACT FROM AUTHOR]

45Ca uptake in mineralizing tissues may occur by net Ca uptake or by isotopic exchange. It is rarely possible to differentiate between these effects, making interpretation of the findings difficult. Unfortunately, this problem is not often considered, and 45Ca uptake is usually regarded as representative of only net calcium uptake. The study reported here was undertaken to estimate the extent to which 45Ca uptake in mineralizing enamel is due to net Ca deposition or to isotopic exchange, and to consider the implications. The enamel surfaces of the lower incisors of adult rats were notched at the gingival line, and the eruption distance over 16 hours was measured. This distance was used to establish the position of a 0.3-mm-wide increment of enamel at the beginning and end of the 16-hour period, during which it passed through the early-maturation stage of enamel formation. The rate of Ca uptake was determined by chemical assay. Other rats were injected with 45Ca, mean plasma specific activity values for the experimental period determined, and the rate of Ca uptake through the same area of enamel formation was estimated. The estimates were from two- to nearly ten-fold greater than those established by chemical assay, indicating that from 50 to 90% of the45Ca uptake occurred by isotopic exchange. 45Ca uptake may indicate more about the labile state of Ca in mineralizing enamel than about the rate of mineral deposition. [ABSTRACT FROM AUTHOR]

We conducted this study to measure maternal plasma, fetal plasma, and fetal enamel fluoride concentrations for four hours following an oral F dose to near-term pregnant guinea pigs. We placed female guinea pigs on de-ionized (Group I) or 3-ppm-F (Group II) drinking water prior to breeding and during gestation. On the 57th day of gestation, we administered a maternal dose of NaF solution (0.6 mg F/kg) by stomach tube. We collected samples of maternal plasma, fetal plasma, and fetal enamel at baseline, at 15 and 30 min, and at one, two, and four h after administration of the dose. We assayed samples for F using a modification of the micro-diffusion and ion specific electrode method. Group I mean baseline F values were: maternal plasma, 0.016; fetal plasma, 0. 002; and fetal enamel, 7.0 ppm. Group II mean values were: 0. 055, 0.004, and 19.0 ppm. After the maternal fluoride dose, the mean maternal plasma /F] rose sharply for 30 to 60 min and declined to about 50% of peak values by four h. Fetal plasma [F] changed less in absolute values, but similarly to maternal changes relative to baseline. Fetal enamel mean [F] rose more in Group II than in Group L Baseline F status had an important effect on F uptake in fetal enamel following an actue maternal fluoride dose. [ABSTRACT FROM AUTHOR]

The surface enamel of fetal bovine teeth was stained with GBIIA to indicate the position of bands of smooth-ended and ruffle-ended ameloblasts relative to the developing enamel. The boundaries of the bands were scored, under a dissecting microscope, and the bulk enamel under each band was collected. The enamel samples were assayed for Ca, PI, F, and proline. The amount of Ca and PI in the enamel increased in successive bands and seemed unrelated to the overlying ameloblast cell type. The loss of proline seemed unrelated to cell type. The fluoride content of enamel increased by approximately 50% in the first stained band immediately adjacent to the secretary zone. The F level returned to secretary values in the succeeding unstained band. Thus, only changes in the F level of developing enamel appeared to be related to GBHA staining patterns. [ABSTRACT FROM AUTHOR]

Eight- and 12-day-old rat pups were injected intraperitoneally with fluoride. Plasma, molar enamel, and bone samples were collected at observation times up to six hr after injection. In a second series, adult rats maintained for six weeks on water containing 5 ppm F were injected with fluoride. Plasma, incisor enamel, and bone samples were collected at the same observation times as those used in the first series. Fluoride assays were conducted by means of the microdiffusion, ion-selective-electrode method. In the suckling rats, plasma [F] levels peaked at 15 min and returned nearly to baseline in one hr. Significant increases in the [F] of developing enamel and bone were observed. No significant decline from the peak [F] seen in the hard tissues was observed over the six-hour period. Similar results were seen in the developing enamel of the adult rats. The data gave no evidence of a short-term reversible component of fluoride uptake in developing enamel. Apparent increases in F uptake in enamel and bone beyond peak plasma values suggest the presence of a diffusion-limiting membrane for fluoride from the extracellular fluids into the mineralizing matrix. [ABSTRACT FROM AUTHOR]

This study investigated the diffusion of fluoride through the enamel organ in vitro. The rat molar explants used were entirely in the secretory stage or predominantly in the maturation stage of enamel formation. The removal of the enamel organ or metabolic inhibition with iodoacetate caused significant increases in enamel fluoride up-take at both stages of enamel formation. Inhibition with dinitrophenol caused a significant increase only in the maturation phase. Uptake of fluoride in enamel was related to the fluoride concentration in the medium, except in the maturation stage explants, where increasing the medium fluoride concentration from 0.05 ppm to 0.08 ppm did not significantly/ increase fluoride uptake at any of the three observation times. The findings indicate that the enamel organ exists as a diffusion-limiting membrane to the movement of fluoride from the extracellular fluid compartment to the developing enamel. [ABSTRACT FROM AUTHOR]

This study was undertaken to map signal transduction pathway (STP) components uniquely associated with the four major receptor groups and their related STPs in association with the events involved in amelogenesis in the rat. Whole-head, freeze-dried sagittal sections were obtained at the level of the maxillary first molars and picked up on transparent adhesive tape. The sections were not decalcified or fixed, providing optimum conditions for immunohistochemical (IHC) localization. Antibodies to pathway components Gsα, Giα, Gqα Sos-1, Grb-2, p125Fak, Jak2, and Vav were localized. The respective patterns of localization indicate that the Gqα-linked, the receptor tyrosine kinase-initiated, and the integrin receptor-initiated pathways are involved in the proliferating pre-ameloblast cells. In the differentiating and differentiated ameloblasts, the Gsα-linked cAMP pathway is involved, apparently reading a factor(s) released by the dentin matrix. The Gqα-linked, the receptor tyrosine kinase-initiated, the integrin receptor-initiated, and the cytokine receptor-initiated pathways are also up-regulated in the proximal ends of the ameloblasts. These observations indicate that all four of the major receptor groups are involved in amelogenesis and that the role of classes of ligands not previously implicated in enamel formation must now be considered. It seems that the cells of the enamel organ respond to the appearance and disappearance of autocrine and paracrine growth factors, but they also up-regulate specific STPs to enable them to respond to circulating hormones and growth factors whose concentrations in the extracellular fluids remain relatively constant. [ABSTRACT FROM AUTHOR]

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. The significance is that similar levels of F can be attained in developing enamel if the same total dose of F is delivered continuously or periodically once a day. Previous studies have shown that there is less chance of producing disturbances in enamel mineralization with continuous F delivery when compared with periodic F delivery at a lower daily dose. [ABSTRACT FROM AUTHOR]

Suckling rat pups were given intraperitoneal fluoride injections at selected ages so that we could study fluoride uptake in the enamel of the maxillary first molar at various stages of enamel development. Plasma fluoride levels in six-day-old and 11-day-old pups were monitored following the intraperitoneal injection of fluoride. The findings indicate that: (1) fluoride was more easily taken up and retained during the early stages of enamel formation, but fluoride uptake can occur during all stages of enamel formation; (2) when injections were started early in enamel formation, more fluoride was contained in the enamel of the maxillary first molar at 13 days of age; and (3) the same dose of fluoride per gram body weight resulted in greater exposure to elevated plasma fluoride levels in six-day-old pups than in 11-day-old pups. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the F levels in plasma and molar enamel from rat pups whose mothers had received various levels of F during pregnancy and/or lactation. Rats were started on water containing 0 (Group I), 50 (Group II), or 100 (Group III) ppm F at the beginning of pregnancy or on the day of delivery. The mothers and pups were killed 13 days after delivery, and plasma F levels, milk F levels, and pup molar enamel F levels were determined. The mean maternal plasma F concentrations were 0.02 ± 0.005 ± ppm in Group I, 0.10 0.031 ppm in Group II, and 0.21 0.05 7 ppm in Group III. The milk F values were about twice as high as the respective plasma concentrations. The plasma F concentration in control pups was 0.003 ± 0.0002 ppm, and there was a rise to 0.006± 0.0002 ppm in Group III Enamel F concentrations were 0.62±0.13 ppm, 4.72 ±0.79 ppm, and 8.80±1.74 ppm, respectively. The plasma and enamel F values obtained from pups were not significantly different between the pre-natal/post-natal, and the post-natal-only groups. It was concluded that: (1) fluoride levels in the plasma and enamel of control rat pups were much lower than those found in adult rats, (2) such values could be increased only slightly when high doses of F were given to the mother, and(3) unlike values reported for other species, rat milk fluoride concentrations were higher than the respective plasma values. [ABSTRACT FROM AUTHOR]

The effects of parathyroid hormone (PTH), calcitonin (CT), 1,25(OH)2D3, and 24,25(OH)2D3 on calcium transport through the secretory stage enamel organ were studied on developing rat molars in vitro. 24,25(OH)2D3 increased 45Ca uptake by the explants. 24,25(OH)2D3 plus PTH further enhanced 45Ca uptake and resulted in an increase in net calcium uptake by the developing enamel. [ABSTRACT FROM AUTHOR]

Autoradiographs of molar teeth from 15-day-old rats that had been injected with 18F showed no tracer uptake in the late-mineralizing enamel. Autoradiographic and quantitative in vitro experiments indicated that the enamel organ limited fluoride uptake during the maturation phase of enamel formation. [ABSTRACT FROM AUTHOR]

The uptake of 48V in developing rat molar enamel was studied in vivo and in vitro using autoradiographic and quantitative methods. It was shown that the uptake of 48V in enamel is less than in bone and dentin, and that plasma protein binding of 48V is primarily responsible for the limited uptake in enamel. [ABSTRACT FROM AUTHOR]

Eleven-day-old rat maxillary first molar explants were removed by microdissection and incubated in vitro to determine the direct effects of parathyroid hormone (PTH), calcitonin (CT), 1,25(OH)2D3, 24,25(OH) 2D3, and a combination of PTH and vitamin D3 metabolites on calcium uptake in the mineralizing enamel of the explants. None of the agents had a statistically significant effect. These results are in contrast to those observed on explants from six-day-old rats, where PTH + 24,25(OH) 2D3 caused a significant increase in net calcium transport. The findings are consistent with the hypothesis that the transcellular transport of calcium through the secretary stage and the maturation stage ameloblasts occurs by different mechanisms. [ABSTRACT FROM AUTHOR]

Objective: To determine whether feeding sweetpotato cannery waste (SPCW) to cattle had adverse effects on dental wear, growth performance, or ruminal tissues., Design: Clinical trial., Animals: 36 Holstein steers., Procedure: Steers were assigned to 1 of 3 groups. All steers received ryegrass hay ad libitum. In addition, steers in group 1 were fed 3.2 kg of corn and soybean meal/steer/d, steers in group 2 were fed 0.45 kg of soybean meal/steer/d and SPCW ad libitum, and steers in group 3 were fed a mixture of SPCW and broiler litter ad libitum. Samples of rumen fluid were collected on day 56. Steers were slaughtered on day 84, and samples of rumen were submitted for histologic examination. Teeth from control steers were removed, and calcium ion loss in response to etching with 2.28% lactic acid solutions buffered to pH of 3.75, 4.0, 4.25, 4.5, and 4.75 was determined., Results: Average daily gain was lower for steers fed SPCW than for steers in the other 2 groups. Steers fed the SPCW-broiler litter mixture had only mild increases in tooth wear and tooth color scores, compared with control steers, whereas steers fed unbuffered SPCW had substantial increases in tooth wear and tooth color scores. Histologic abnormalities were detected in rumens from steers fed diets containing SPCW. Calcium ion loss decreased as pH of the etching solution increased., Clinical Implications: Results indicate that feeding cattle unbuffered SPCW can cause dental erosion, ruminal epithelial changes, and poor growth; however, SPCW buffered with broiler litter can be used as a cattle feed.

45Ca uptake in mineralizing tissues may occur by net Ca uptake or by isotopic exchange. It is rarely possible to differentiate between these effects, making interpretation of the findings difficult. Unfortunately, this problem is not often considered, and 45Ca uptake is usually regarded as representative of only net calcium uptake. The study reported here was undertaken to estimate the extent to which 45Ca uptake in mineralizing enamel is due to net Ca deposition or to isotopic exchange, and to consider the implications. The enamel surfaces of the lower incisors of adult rats were notched at the gingival line, and the eruption distance over 16 hours was measured. This distance was used to establish the position of a 0.3-mm-wide increment of enamel at the beginning and end of the 16-hour period, during which it passed through the early-maturation stage of enamel formation. The rate of Ca uptake was determined by chemical assay. Other rats were injected with 45Ca, mean plasma specific activity values for the experimental period determined, and the rate of Ca uptake through the same area of enamel formation was estimated. The estimates were from two- to nearly ten-fold greater than those established by chemical assay, indicating that from 50 to 90% of the 45Ca uptake occurred by isotopic exchange. 45Ca uptake may indicate more about the labile state of Ca in mineralizing enamel than about the rate of mineral deposition.

The cytogenetic effects of sodium fluoride (NaF) were measured in mice following administration in the drinking water for 6 weeks. Bone fluoride levels were determined and showed a dose-related incorporation of fluoride. Micronuclei were measured in peripheral blood erythrocytes following 1 and 6 weeks of NaF administration. Bone marrow cell preparations were examined for the presence of chromosome aberrations following 6 weeks of treatment; metaphase and anaphase cells were examined. Anaphase cells were scored in three independent laboratories, two of which also scored metaphase cells from the same slides. No increases in micronuclei were seen in peripheral erythrocytes at either time point, and no increases in chromosome aberrations were seen in bone marrow cells when metaphase or anaphase cells were examined. A concurrent positive control, cyclophosphamide, produced significant increases in peripheral blood cell micronuclei and in chromosome aberrations in bone marrow cells in metaphase. No increases in aberrations were seen in the same cyclophosphamide-treated mice when anaphase cells were examined.

The most recent report on fluoride concentrations ([F]) in human bone was published over a decade ago. Such data are of interest in the context of changing patterns in systemic fluoride exposure. In the study reported here, bone samples were collected from 24 human subjects who underwent orthopedic surgery. Medical histories and the best possible life-time systemic fluoride exposure information were obtained from each subject. Bone samples were assayed for fluoride concentration using the acid diffusion, ion selective electrode method. For ash from whole bone, the lowest value was 378 ppm in a 16-year-old subject, and the highest value was 3,708 ppm in a 79-year-old person. Fluoride concentrations in bone were significantly correlated with age (r = .62). The regression line intercept at birth was 442 ppm, and the slope was 22 ppm per year. When measured separately, trabecular bone ash fluoride concentrations were significantly higher than the corresponding cortical bone values. Trabecular and cortical bone samples from rats' drinking water containing 75 ppm F were assayed for F. The mean trabecular bone fluoride concentration was significantly higher than the mean cortical bone concentration. There was close agreement between F assay results using a modification of the acid diffusion method and the method originally reported by Singer and Armstrong. The human bone ash [F] values reported in this study are similar to those reported from other North American subjects over the last three decades. These findings are of interest in the context of evidence indicating increased systemic fluoride exposure in the United States population.(ABSTRACT TRUNCATED AT 250 WORDS)

Nine-day-old rats were given oral fluoride doses (0.5 micrograms F/g body weight). Plasma, enamel organ, muscle and liver samples were collected from nondosed pups (baseline) and 15, 30, 60 and 120 min after the dose. Samples were assayed for fluoride and calcium concentrations. Adult rats were given 20 ppm F water for 6 weeks, and the same tissues were sampled and assayed for fluoride concentrations only. In the first phase of the study, enamel organ had significantly higher fluoride and calcium content than liver and muscle. In adult rats the fluoride content of enamel organ was again significantly higher than for liver and muscle.

The uptake of 48V in developing rat molar enamel was studied in vivo and in vitro using autoradiographic and quantitative methods. It was shown that the uptake of 48V in enamel is less than in bone and dentin, and that plasma protein binding of 48V is primarily responsible for the limited uptake in enamel.

The course and insertion pattern of muscle fibres in the philtrum of the human upper lip were studied in seven post-mortem specimens using serial histological sections and a reconstruction method using sheets of Plexiglas. The fibres of the musculus orbicularis oris entering the upper lip from one side were observed to decussate in the midline and proceed to insert into the skin of the opposite side lateral to the philtral groove. The philtral ridges appeared to represent the medial borders of bilateral muscle insertion zones of the lip in which the fibres of the m. orbicularis oris raised the level of the skin by splaying out and inserting into it. Contributions to philtral form also came from the musculus levator labii superioris as it descended as far medially as the philtral ridge to insert into the vermilion border lateral to the median groove, and from fibres of the musculus nasalis which inserted into the philtral ridges superiorly. The philtral groove corresponded to the more compact median decussation of the orbicularis oris where lip thickness was also reduced by the relative absence of muscle fibre insertions into the skin. The displacment of the vermilion border giving rise to Cupid's bow appeared to result from the lifting action of the m. levator labii superioris lateral to the median groove in conjuction with a depressor action by the m. orbicularis oris on the median tubercle.

The surface enamel of fetal bovine teeth was stained with GBHA to indicate the position of bands of smooth-ended and ruffle-ended ameloblasts relative to the developing enamel. The boundaries of the bands were scored, under a dissecting microscope, and the bulk enamel under each band was collected. The enamel samples were assayed for Ca, Pi, F, and proline. The amount of Ca and Pi in the enamel increased in successive bands and seemed unrelated to the overlying ameloblast cell type. The loss of proline seemed unrelated to cell type. The fluoride content of enamel increased by approximately 50% in the first stained band immediately adjacent to the secretory zone. The F level returned to secretory values in the succeeding unstained band. Thus, only changes in the F level of developing enamel appeared to be related to GBHA staining patterns.

Antero-posterior retardation of upper jaw growth became evident in all five dogs with surgically placed clefts and extirpation of the vomer within 8 weeks following surgery. Five control dogs with congenital cleft palate maintained a normal jaw relationship. The evidence indicated that the difference in growth between the two groups may be explained in terms of the role played by the vomer in the growth and support of the upper jaw in the dog. This observation suggests that the dog may be used as a model for the study of retardation of growth in the antero-posterior dimension and indicates a need for research concerned with the role of the vomer in the human bilateral cleft condition.

The uptake patterns of 90Sr in developing rat molar enamel were studied in vivo and in vitro. Autoradiographic methods were used that preclude loss or translocation of tracers associated with water-soluble compounds in the sections. In eight-day-old rats injected with the tracer, 90Sr uptake in the enamel was significantly less than for dentin and bone, particularly at early sacrifice times. The uptake pattern of 90Sr was somewhat different from that previously observed for 45Ca. The in vitro experiments indicated that the viable intact enamel organ limits uptake of 90Sr by enamel in both the secretory and maturation phases of enamel formation.