Effect of 1-p-bromotetramisole on mineralization of hamster tooth germs in vitro: a light and electron microscopic study

In culture, 10(-3)M 1-p-bromotetramisole (1-pBTM) inhibited mineralization of in vitro secreted enamel matrix in two-day old neonatal hamster first maxillary molar tooth germs. In contrast, in control tooth germs cultured without the inhibitor, new enamel and dentin matrices were secreted and subsequently mineralized in vitro. It is suggested that the arrested enamel matrix mineralization in vitro is a result of reduced phosphate uptake due to alkaline phosphatase inhibition by 1-pBTM. In addition, 1-pBTM induced accumulation of secretory granules in odontoblasts and ameloblasts, but not in the other cells. This is probably a specific effect of the inhibitor on these cells due to alkaline phosphatase inhibition.

Influence of EHDP and F on Ca and P loss from enamel during the intra-oral cariogenicity test

The effect of anticalculus agent EHDP (0.05%) on caries has been studied in the presence and absence of 0.1% F- under the conditions Intra Oral Cariogenicity Test (ICT). Whereas EHDP had no influence on the change in microhardness of the produced by sucrose in the presence of absence of fluoride, it increased the F- effect inside the lesion thereby preventing the formation of minerals with a mol Ca/P ratio deviating from apatite. The EHDP effect was additioned to the F- effect demonstrating that both components act independently of one other. In this respect it has been suggested that 0.05% EHDP acts mainly on demineralization by decreasing the acid production of the micro-organisms whereas F- stimulates remineralization particularly by acting on the enamel surface.

Partial purification and some characteristics of hamster molar alkaline phosphatase

A rapid 3-step method is given to purify partially hamster molar alkaline phosphatase. Molecular weight was 50,200 and isoelectric point 3.7. The alkaline phosphatases in the mesenchymal and ectodermal parts of the tooth are probably identical.

Biosynthesis of tooth germ proteins in vitro: a fast quantitative extraction of amelogenins from intact hamster molar tooth germs

A three step extraction procedure was carried out on intact hamster molar tooth germs in vitro labelled with 32PO4 and/or 3H-proline, in order to quantify separately the synthesis of dentine matrix (collagen) and the proline rich enamel matrix proteins. The extraction was based on the high solubility of the proline rich enamel matrix proteins compared with the relatively insoluble dentine matrix collagens. Pretreatment with 10% trichloroacetic acid (step 1) demineralized and removed the non-incorporated amino acids and/or small sized peptides. A consecutive water extraction (step 2) removed a large percentage of the phosphorylated amelogenins as assessed by SDS-urea-polyacrylamide-electrophoresis and amino acid analyses. Collagenase digestibility data showed that only small amounts of collagens were present in this extract. Further extraction with 10% formic acid (step 3) released only small amounts of amelogenins from the explants but also increased contamination with collagens and another predominantly low molecular components. Most of the 3H-activity remaining in the residues was found in the collagenase labile material and was considered to be an appropriate measure for production of dentine collagens. On the other hand, the residues also contained small amounts of 3H-labelled material with the same electrophoretic mobility as amelogenins but had much more 32P-activity than the amelogenins derived from the water and formic acid extracts. It is suggested that this material in the residues probably contains the crystal bound enamel matrix proteins.

Correlation between some salivary tests, oral hygiene and caries in children

gn 137 children whose ages varied from 2-14 years, salivary tests and oral hygiene levels were determined for boys and girls separately. Only the unstimulated flow (flow 1) differed significantly between boys and girls. For the initiation and further development of new caries lesions more precise definitions were used in which the results were corrected for number of teeth present and for the time interval between the observations. The caries scores for all children together were correlated with the several salivary test results as well as with oral hygiene levels. The initiation of caries was correlated with oral hygiene as well as with the Snyder test. The further development of caries correlated almost significantly with the inorganic composition of the saliva alone. No correlation was found between the initiation and the further development of caries.

A histological study of the short-term effects of fluoride on enamel and dentine formation in hamster tooth-germs in organ culture in vitro

First maxillary molars in early stages of secretory amelogenesis were exposed in vitro to fluoride (F-) concentrations ranging between 2.63 microM and 2.63 mM for up to 3 days. In contrast to the dentine papilla, which seemed unaffected by F- in concentrations up to 1.31 mM, the enamel organ was dose-dependently extremely sensitive for F-. Young ameloblasts which became secretory in vitro were in particular sensitive and did not secrete enamel adjacent to new, in vitro-formed dentine. Hypermineralization of the dentine at the enamel-dentine junction suggested that these ameloblasts still transport and deposit minerals. 52 microM was the lowest concentration of F- that inhibited deposition of enamel in the cervical-loop region. Ameloblasts, secretory at the time of exposure to F-, in concentrations of 52 microM up to 1.31 mM secreted an abnormal, amorphous, von-Kossa-negative enamel matrix. 1.31 mM of F- was the lowest concentration which induced the formation of a hypermineralized band in the pre-exposure enamel. 2.63 mM of F- was highly toxic for the enamel organ but had only moderate effects on the dentine papilla.

Long-term (8 days) effects of exposure to low concentrations of fluoride on enamel formation in hamster tooth-germs in organ culture in vitro

Second maxillary molars of 3-4-day-old hamsters were cultured for 7-8 days in the continuous presence of fluoride (F-) or chloride in concentrations between 2.63 microM and 1.31 mM. For biochemical study, explants were labelled during the last 24 h of culture with a triple label of [3H]-proline, 45Ca and 32PO4. The 3H-labelled presumptive amelogenins were separated from the 3H-labelled dentine collagens by a three-step extraction procedure. Histologically, chronic exposure to F- had no obvious effects below 26.3 microM; at 26.3 microM of F-, a non-mineralizing enamel matrix was observed besides that of a normal mineralizing enamel. From 52 microM of F- onwards, only a non-mineralizing enamel matrix was found in decreasing amounts extracellularly as F- concentrations increased. Except for the presence of globular dentine, dentinogenesis was not obviously affected by F-. Biochemically, total synthesis of presumptive amelogenins was hardly disturbed, but their solubility was changed by chronic F- treatment; more amelogenins became formic-acid soluble at the expense of water-soluble amelogenins. Chronic exposure to F- decreased the water-soluble amelogenin fraction according to a logarithmic function of the medium F- concentration. By extrapolation, it was calculated that concentrations higher than 1-2 microM of F- affect amelogenesis in vitro. Synthesis of dentine collagen was not affected by chronic exposure to F- in vitro. Chronic exposure to F- decreased uptake of 45Ca and to a less extent trichloroacetic acid-soluble 32PO4. Chronic F- exposure may inhibit energy production in the enamel organ resulting in an impairment of enamel matrix secretion as well as that of a trans-epithelial transport mechanism for calcium.

Studies of alkaline phosphatase inhibition by p-bromotetramisole in non-mineralizing and mineralizing neonatal hamster tooth germs in vitro

The effects of l and d-, p-bromotetramisole (pBTM) on alkaline phosphatase were studied in relation to 45Ca2+, 32phosphate and 3H-thymidine uptakes in non-mineralizing second (M2) and mineralizing first (M1) maxillary hamster molar tooth germs under the conditions of organ culture. At the concentration used in culture (10(-3)M), l-pBTM completely inhibited alkaline phosphatase activity in tooth germ homogenates. About 30% of the enzyme activity was inhibited by d-pBTM at the same concentration. In culture, there were no significant differences between the effects of l and d-pBTM isomers on all the parameters measured. In the non-mineralized M2 molars, l and d-pBTM significantly reduced both TCA-soluble and TCA-insoluble 32phosphate uptakes but not 45Ca2+. However, 3H-thymidine uptake was also significantly decreased. In M1 molars, the pBTM isomers significantly reduced the uptake of TCA-soluble 32phosphate and 45Ca2+ but not TCA-insoluble 32phosphate. Ouabain, a specific inhibitor of Na+-K+-ATPase (but not alkaline phosphatase), also significantly reduced 3H-thymidine uptake to the same extent as the pBTM isomers in the non-mineralizing M2 molars, but it did not significantly affect either 32phosphate (TCA-soluble and TCA-insoluble) or 45Ca2+ uptake. Although this inhibitor significantly reduced both 45Ca2+ and TCA-soluble 32phosphate uptake in the mineralizing M1 molars, this effect was much less dramatic than was the case with the pBTM isomers. The reduced 45Ca2+ uptake in the M1 molars is probably a consequence of reduced mineralization since in the non-mineralizing M2 molars calcium uptake was not significantly affected by the pBTM isomers.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of fluoride on mineral loss in the intra-oral cariogenicity test

The loss of Ca and P was determined in different layers of enamel slabs after an Intra-Oral Cariogenicity Test with 3% sucrose in the presence and absence of F-. The mineral loss could be inhibited largely by 0.1% F-. A direct relationship between indenter penetration change and mineral loss was demonstrated in the absence of F-.

Carbonate incorporation and carbonic anhydrase activity in developing hamster molars in vitro

Hamster molar tooth germs were tested in vitro for their capacity to incorporate 45Ca, 32PO4 and H14CO3 into their mineral. Concomitantly, the activities of alkaline phosphatase and carbonic anhydrase were measured in the cultured tooth germs. Incorporation of calcium and phosphate into the dental mineral increased with time in culture (0-10 days), whereas carbonate incorporation decreased slightly. Alkaline phosphatase and carbonic anhydrase increased with time. These results suggest that carbonic anhydrase is probably not involved in carbonate deposition, but in carbonate depletion of the dental mineral, carbonate being probably replaced by phosphate.

Remineralization in human premolars of different posteruptive age

In human premolars with posteruptive ages varying from 6 months to 4 years demineralized enamel was remineralized for 3 days at 37 degrees C in a recalcifying medium containing 2 mM Ca2+, 1.2 mM phosphate, 0.05 mMF- and 150 mM NaCl (pH = 7). The Ca, P and Ca/P molar ratio of the mineral gained were determined at various distances from the enamel surface. Whereas, particularly at 30 micrometers from the surface remineralization was higher and more extensive in young demineralized enamel, no difference could be found in Ca/P molar ratio, suggesting precipitation of an apatitic mineral in both young and old demineralized human enamel. The probable nature of the precipitate is that of a fluoridated hydroxyapatite.

Effect of developmental stage of explants on further in-vitro development of hamster molars

With morphometrical and biochemical methods the in-vitro development of 1-4-day-old 2nd maxillary molars was studied up to 10 days and compared with previously reported in-vivo development. Incorporation of [3H]-thymidine and increase in dry weight were used as biochemical parameters for cell proliferation and growth respectively specific alkaline phosphatase activity and uptake of 45Ca as the measure for mineralization. In explants of 2-4-day-old hamsters, formation of dentine and enamel matrix was consistent: both mineralized. These explants attained stages beyond enamel matrix formation, possibly the transitional stages of amelogenesis. The amounts of matrices produced appeared to be related to the final size the explants attained. Best in-vitro development histologically was in explants of 2 and 3-day-olds. Thus in-vitro development was qualitatively similar to in vivo.

Histological and biochemical studies of vitamin C requirements of hamster molars during development in vitro

The dose response relationship between medium concentrations of vitamin C (0-350 micrograms/ml) and the hydroxylation of in vitro incorporated 3H-proline showed that in (small) 2nd molars 50 micrograms/ml vit C at level of a maximum hydroxylation was attained at whereas in (larger) 1st molars higher medium concentrations seemed to be required (150 micrograms/ml or more). No cytotoxic effects were observed in media containing concentrations of vit C up to 350 micrograms/ml. In the absence of vit C odontoblasts in young 2nd molars failed to differentiate normally and an abnormal jelly-like substance was produced. Dentinogenesis in the 2nd molars was normal in the presence of at least 50 micrograms/ml vit C. In the 1st molars, in which production of collagenous dentine matrix had already started at the time of explantation, significantly less 3H-hydroxyproline was measured during vit C deficiency as early as the first day of culture, suggesting that there is a high need for vit C during dentinogenesis in vitro.

Changes in calcium and phosphorus content in young human enamel during demineralization in vitro

Premolars extracted about 6 months after eruption were divided into four parts by sectioning through the mesial- and distal midplanes. The enamel of each part was subjected to demineralization by hydroxy-ethyl-cellulose (H.E.C.) gel at pH 4 for periods varying between 2 and 24 hrs. The Ca and P contents of the gel as well as that of 10 microns slices prepared from the enamel after demineralization were determined. Then the Ca and P content of the HEC gel as well as that of 10 microns slices sequentially sectioned from the surface of the demineralized enamel inwards, were determined. The data indicate that initially, demineralization was predominant in the layers between 20 and 60 microns depth together with a reprecipitation in the surface 20 microns layer. After about 6 h of demineralization more mineral loss was found from layers deeper than 60 microns. Further, it was shown that the molar Ca/P ratio of mineral loss from these young teeth at depths of between 40 and 50 microns was extremely high (about 3) whereas in older teeth it was normal. This might be due either to preferential dissolution of carbonate containing mineral or to preferential precipitation of HPO4(2)--containing mineral or both especially at that depth.

Organ culture of tooth germs: relationship between alkaline phosphatase and mineralization in vitro

In the 3rd day 2nd molar of the hamster, mineralization of the tooth germ has been studied in vitro starting from unmineralized predentine stage up to secretory amelogenesis. The explants were cultured in BGJb medium containing 15% foetal calf serum. The biochemical data on whole tooth germs were compared morphometrically with its main calcifying components. The alkaline phosphatase seems not to be related to cell-division but more to mineralization. There the alkaline phosphatase appeared to be more correlated with the phosphorus than with the calcium uptake. Its function in mineralization of the tooth germ seems also to be more expressed in dentinogenesis than in amelogenesis.

X-ray diffraction of enamel from human premolars several years after eruption

Small slices were cut from rods prepared from the labial surface of premolars extracted 4 and 5 years after eruption. Consecutive slices (200 microns thick) were taken at distances 500 microns apart from each other. X-ray diffractograms were obtained from each slice in a Guinier camera. Distinct reflections were obtained from slices up to depths of 2000 microns. The average depth of good cristallinity was 1000 microns in these older teeth in contrast to freshly erupted teeth where it is about 300 microns. No gradient could be detected in the lattice parameters from the surface layer towards the dentino-enamel junction in these older teeth. The average lattice parameters were a = 9.453 A and c = 6.890 A. Compared to data obtained on young teeth (Driessens et al., J. Biol. Buccale 10: 55, 1982) the crystallinity of the mineral appeared to increase with age in deeper layers. This result is consistent with the decrease of the caries susceptibility of human enamel with age postulated in the literature.

Ultrastructural changes in developing hamster molars during vitamin C deficiency in vitro

Second day maxillary molars of hamsters were cultured during 4, 8 and 10 days in the presence or absence of 250 micrograms/ml vitamin C. After 8 days of culture without vit. C the basal lamina in the cervical loop region (proliferation zone) was locally disrupted; after 10 days it was completely absent or only remnants of it could be found. In the differentiation zone an abnormal amorphous predentine matrix was found during vit. C deficiency; from the 4th day on the basal lamina had changed in structure or ruptured prematurely. A role of the basal lamina in directing odontoblast differentiation is possible but was not actually demonstrated. It is suggested that the failure of the pre-ameloblasts to differentiate was due to changes in the extracellular matrix. The observations support a cell-matrix type of interaction for the differentiation of the ameloblast.

X-ray diffraction of enamel of a freshly erupted human tooth

Small slices were cut from enamel prepared from the labial surface of a freshly erupted human premolar. Consecutive slices (200 micrometers thick) were taken at distances 500 micrometers apart from each other. X-ray diffractograms were obtained from each slice in a Guinier camera. Only the slices cut from the outer 500 micrometers of human enamel resulted in distinct reflections. Typical lattice parameters were a = 9.462 A and c = 6.898 A for one slice and a = 9.457 A and c = 6.890 A for another slice of outer enamel. Non-apatitic reflections could not be detected. The line-broadening occurring in deeper layers was shown to be due either to intracrystalline strain or to inhomogeneities on the crystalline level. Theoretical models and submicroscopical findings of other authors are discussed in relation to the present findings.

A morphometric and biochemical study of the pre-eruptive development of hamster molars in vivo

Surface area measurements of cross-sections of M1 and M2 at 1-11 days were related to biochemical parameters for cell proliferation ([3H]-thymidine incorporation) and mineralization (45Ca uptake) and with increase in dry weight. The pre-eruptive development of molar tooth germs was divided into 4 phases which partly reflect the life cycle stages of the ameloblast. In phase 1 (proliferation phase, duration in M2 about 5 days) mitotic activity and increase in total area were great; ameloblasts were undifferentiated or in a pre-secretory state. In phase 2 (differentiation phase, duration 2-3 days) the number of secretory ameloblasts increased and 45Ca uptake started and increased rapidly. At the end of phase 2, crown morphogenesis was completed and cell proliferation ([3H]-thymidine incorporation) became less. In phase 3 (secretion phase, duration 0.5-1 days) all ameloblasts throughout the tooth germ had differentiated into secretory ameloblasts and enamel matrix surface area increased about twice as fast as that of dentine. At the end of phase 3, the surface area of the enamel matrix almost attained its final value. In phase 4 (maturation phase, duration in M1 till first eruption about 2-3 days), post-secretory ameloblasts increased in number and, in contrast to the surface area of the enamel matrix, that of the dentine continued to increase. The fast, linearly increasing total uptake of 45Ca during phase 4 which was attributed to the mineralization of both newly formed dentine and existing maturing enamel was the main cause of the rapid increase in dry weight of the whole tooth germ.