Content Of Enamel Research Articles

Evaluation of mineral content of enamel prepared by erbium, chromium:yttrium–scandium–gallium–garnet laser

The aim of this study was to evaluate the mineral content of enamel etched at two different power settings with an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser. Buccal, lingual and mesial or distal surfaces of five premolar teeth were cut, and three enamel slabs were obtained from each tooth. Fifteen enamel specimens were divided into three groups (1 W, 2 W and control) of five specimens each and subjected to Er,Cr:YSGG laser. The mean percentage weights of the five elements [calcium (Ca), potassium (K), magnesium (Mg), sodium (Na) and phosphorus (P)] in each slab were measured by inductively coupled plasma-atomic emission spectrometry (ICP-AES). One way analysis of variance (ANOVA) was used to analyze differences among the groups (1 W, 2 W and control). There were no significant differences among the groups (1 W, 2 W and control) for Ca, K, Mg, Na, or P, or for the Ca/P ratio (P > 0.05). Scanning electron microscopy (SEM) photographs indicated that the surface irregularities increased with increased power setting. Laser treatment did not affect the mean percentage weights of Ca, K, Mg, Na, and P, or the Ca/P ratio, in any group.

Argon laser induced changes to the carbonate content of enamel

Argon laser irradiation can be used to cure orthodontic brackets onto teeth in significantly less time than conventional curing lights. In addition, it has been shown that the argon laser seems to impart a demineralization resistance to the enamel. The purpose of this study was to use surface science techniques to ascertain if this demineralization resistance is possibly a result of a decrease in the carbonate content of enamel. Eleven mandibular third molars previously scheduled for extraction were collected and used in the present study. The teeth were sectioned in two and randomly assigned to either the argon laser (457–502 nm; 250 mW cm −2) or the control (no treatment) group. The sections assigned to the argon laser group were cured for 10 s and analyzed. To exaggerate any potential changes the experimental sections were then exposed to a further 110 s of argon laser irradiation. Surface analysis was performed using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results showed no statistically significant change in the carbonate content of enamel after argon laser irradiation ( p > 0.05). Thus, it is suggested that any demineralization resistance imparted to the enamel surface by argon laser irradiation is not due to alterations in carbonate content.

Polymerization contraction stress in resin–tooth bonds under hydrated and dehydrated conditions

Objective This study hypothesizes that, with enamel or dentin as a bonding substrate, intrinsic water affects the development of polymerization contraction stress in the bonds of self-etching adhesives during bonding. Materials and methods The influence of the water content in dentin and enamel (wetness with water as control and acetone-dried specimens) on the stress development in self-etching adhesives was determined with a tensilometer. Thin layers of self-etching primer and/or adhesive resins were created between a glass plate and a flat enamel or dentin surface. Results After an initial maximum shortly after light curing for 30 min, the contraction stress was decreased in the dentin (30–70%) and enamel (approximately 20%). In the acetone-dried specimens, the stress was continuously increased for 20–50%. Significance The intrinsic water content of tooth tissue influences the initial polymerization of polymers. This effect is favorable for stress relief in resin restoration but causes unwanted nanoleakage channel formation in resin–tooth bonds.

Effect of a Fluoridated Food Item on Enamel in situ

After the consumption of food items prepared with fluoridated salt elevated fluoride concentrations can be observed in saliva, whereby enamel mineralization is supposed to be positively affected. The aim of this double-blind (with respect to fluoride), placebo-controlled, randomized, cross-over study was to evaluate the effects of the consumption of either a fluoridated (effect) or a placebo food item on the mineral content of sound and pre-demineralized human enamel in situ. During both phases of the study 8 enamel specimens in each of 10 intraoral appliances were positioned, either recessed or flush with the acrylic surface. One of the flanges was brushed twice daily with fluoride-free toothpaste prior to the storage of the appliance in sucrose solution. The subjects were asked to refrain from other sources of fluorides except for the consumption of either a highly fluoride-containing (0.5 mg) or a placebo cookie (3 times daily) during the respective study phase. Mineral content and lesion depth were measured in the enamel specimens and fluoride concentrations in saliva and urine. Significantly increased urinary and salivary (immediately after food consumption) fluoride concentrations compared to baseline were observed during the effect phase. In the absence of fluorides more pronounced demineralization was observed, especially for the recessed specimens of both surface conditions. Brushing was shown to inhibit demineralization, particularly during the placebo phase. In conclusion, fluorides added to food items seem to be efficacious to inhibit enamel demineralization in plaque-covered enamel but might be less effective if oral hygiene is adequate.

In vitro Evaluation of the Effectiveness of Acidic Fluoride Dentifrices

This study evaluated the effectiveness of acidic low-fluoride dentifrices compared to conventional neutral dentifrices. Enamel blocks were submitted to pH cycling and treatment with slurries of dentifrices containing 0, 275, 412, 550 and 1,100 µg F/g (pH 4.5 or 7.0), and also a commercial dentifrice (1,100 µg F/g) and a commercial children’s dentifrice (500 µg F/g). Variations in surface microhardness and in the mineral content in enamel after pH cycling were calculated. Enamel blocks treated with acidic dentifrices exhibited less mineral loss compared to neutral dentifrices (ANOVA; p < 0.05). The acidic dentifrices with 412 and 550 µg F/g had the same effectiveness as the neutral 1,100-µg F/g dentifrice and commercial 1,100-µg F/g dentifrice.

Quantitative analysis of the calcium and phosphorus content of developing and permanent human teeth

It was the aim of this study to investigate the distribution of Ca, P and C in predentin, dentin and enamel in human tooth buds and permanent teeth by EDX element analysis. The mandible of a 16-week-old human fetus containing eight mineralizing tooth buds and three human permanent molars were fixed in formaldehyde and embedded in Technovit 9100. Serial sections of 80 microm thickness of the mandible were cut in the frontal-dorsal direction, and polarized light micrographs were taken of these sections. The permanent teeth were cut in mesio-distal direction. The sections were investigated with scanning electron microscopy and EDX element analysis with a Philips XL 30 FEG scanning microscope and an EDAX energy-dispersive X-ray system using spot measurements, EDX line-scans and element mapping. Quantitative measurements were made in predentin, mineralizing dentin adjacent to predentin, mature dentin, mineralizing enamel and young enamel of developing teeth and mature enamel of permanent teeth. In developing teeth the Ca and P content increased rapidly from outer predentin towards mineralizing dentin. In enamel prisms of developing teeth the Ca and P content increased linearly from the surface towards the enamel-dentin junction. In permanent teeth only a small layer of predentin was found. The Ca and P content in enamel and circumpulpal dentin of permanent teeth was higher than in developing teeth. The Ca/P ratio differed between predentin and dentin areas reflecting different calcium phosphate compositions, but it was the same in mineralizing and young enamel. The differences in the distribution of Ca and P reflect different mineralizing patterns of the enamel and dentin matrices.

Thirty-five percent carbamide peroxide application causes in vitro demineralization of enamel

Objectives The objective of this in vitro study was to investigate whether a high concentration ‘in-office’ bleaching agent affected the mineral content of enamel and dentin. Methods A commercially available 35% carbamide peroxide bleaching agent was applied for 2 h to sectioned teeth ( n = 11). Specimens were then immersed in artificial saliva at 37 °C for a further 24 h to simulate the oral environment. Tomographic images of these sections were obtained (micro-CT 80, Scanco, Switzerland) prior to and post-bleach application. Eight three-dimensional regions of interest (ROI), starting from the enamel surface extending to the dentinoenamel junction, were selected for each section. The hydroxyapatite equivalent mineral concentrations (g/cm 3) of the ROIs were calculated. Any changes in mineral content as a consequence of the bleaching procedure were calculated in relation to each ROI. Results There was a significant reduction in the mineral content of enamel specimens post-bleach application extending to a depth of 250 μm (paired t-test, p < 0.05); this reduction in mineral content was greatest in the ROI's closest to the tooth surface. There was, however, no significant difference in the mineral content of dentin as a consequence of bleaching. Significance This in vitro study has shown that significant demineralization of enamel occurred following bleaching with 35% carbamide peroxide. The concept that ‘in-office’ bleaching is a non-destructive cosmetic procedure should be reconsidered.

Influence of the water content in dental enamel and dentin on ablation with erbium YAG and erbium YSGG lasers

The theory of the ablation of dental hard tissue with erbium lasers is based on a process of thermomechanical interaction, which is explained by the absorption of the radiation in the water component of the tissue. The abrupt evaporation of the water is the cause of tissue fragments being blasted out of the tooth structure. The aim of this study is to examine the effect of the water contained in dental hard tissues on the efficiency of ablation. 192 specimens of both bovine dental enamel and bovine dentin are irradiated with an Er:YAG and an Er,Cr:YSGG laser. Half of the specimens are dehydrated beforehand. Irradiation is carried out in subgroups: without water spray and with water spray at flow rates of 0.8 and 3 mls. The ablated volume is determined following histological preparation. Only in dentin, and then only with irradiation with the Er:YAG laser, is the water contained in the tissue found to have a significant influence (p < 0.0001) on the ablated volume. The water content has no effect on the efficiency of laser ablation in any of the other test groups. In contrast, the externally supplied water always has a significant influence on the effectiveness of the ablation process.

Fructooligosaccharides Consumption Inhibits the Loss of Iron from the Incisor Enamel Surface in Gastrectomized Rat

We examined the effects of fructooligosaccharides (FOS) on the reduction in the incisor iron content in gastrectomized rat. Twenty-eight 5- wk-old male Sprague-Dawley rats were divided into two groups: sham operated (bSH) and gastrectomized (bGX). After 4 wk, each group was divided into two subgroups according to the presence or absence of 7.5% FOS in the synthetic diet (SH, SH+FOS, GX, and GX+FOS). At 10 wk after surgery, the maxilla was prepared to examine the iron content of the incisor enamel surface at four points. These points corresponded to the iron content at 6, 7, 8, and 10 wk, respectively. Blood was collected to determine serum iron levels at 4 and 10 wk. The serum iron level significantly decreased at 4 and 10 wk in the GX group. At 10 wk, the level in the GX+FOS group significantly increased but did not reach that in the SH group. The iron content of the enamel surface time-dependently increased and no significant differences were seen between SH and GX+FOS at 8 and 10 wk. These results suggest that FOS consumption impaired the loss of enamel content following gastrectomy, and this effect preceded the effect on the serum iron level.

Microcomputerised tomography evaluation of 10% carbamide peroxide applied to enamel

There is still some controversy in the dental literature whether carbamide peroxide bleaching causes demineralization of teeth. One of the reasons for this controversy is that there is as yet no reliable, non-destructive in vitro method for assessing mineral loss in bleached teeth. The objective of this study was to investigate the possible demineralization effect of 10% carbamide peroxide bleaching agent on enamel and dentine non-destructively. microCT images were obtained of 12 human molar tooth sections. These sections had 10% carbamide peroxide applied for eight hours a day over a period of 15 days. Further tomographic images were obtained and the mineral content prior to and post bleaching assessed. A total of 144 regions were evaluated using the image processing language available in the work station. The application of 10% carbamide peroxide was found to cause demineralization of the enamel extended to a depth of 50 microm below the enamel surface (Paired t-test, p<0.05). This study confirmed that microCT was indeed a highly suitable method for assessing mineral content of dental enamel after bleach application. It is recommended that application of bleaching agents should be carefully considered in patients susceptible to caries and tooth wear.

Detection of Mature Collagen in Human Dental Enamel

Mature dental enamel is the most mineralized of all mammalian tissues and considered to be free of collagen. Hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) are two nonreducible cross-links of mature collagen. Hydroxyproline (Hyp) is an amino acid that is believed to be indicative of the presence of collagen. We set out to assess the concentrations of Hyp, HP, and LP in dental enamel and dentin (control) to clarify whether there was minor collagen content in dental enamel. We studied 17.53 g of enamel and 22.12 g of dentin gained from 120 extracted human teeth. Enamel and dentin (control) were separated with a diamond dental drill under microscopic control by wasting a margin of enamel (Ca. 2 mm) at the dentin-enamel border. Collagen alpha-chains were analyzed by Sodium dodecylsulfate-polyacrylamide gel (SDS-PAGE) after decalcification and collagen extraction. Concentrations of HP and LP where measured by using high-performance liquid chromatography (HPLC). Hyp was analyzed by a spectrophotometric method. The pooled probe of enamel contained 0.23 mug/g of Hyp. This concentration was 49 times lower than that in dentin. Concentrations of HP and LP in enamel were 0.07 nmol/g and 0.02 nmol/g, respectively being 605.57 (HP) and 251.50 (LP) times lower in enamel as compared to dentin. Collagen type I was found in enamel; collagen types I and V were found in dentin samples. In reports of many studies and textbooks, collagen is considered to be completely absorbed in the course of the mineralization and maturation of dental enamel. We show that this is not the case. However, the concentration of collagen in enamel was considerably lower as compared to that in dentin.

Diagenesis and the reconstruction of paleoenvironments: A method to restore original δ 18O values of carbonate and phosphate from fossil tooth enamel

Intra-tooth δ 18O variations within the carbonate (δ 18Oc) and phosphate (δ 18Op) components of tooth apatite were measured for Miocene and Pliocene hypsodont mammals from Afghanistan, Greece and Chad in order to evaluate the resistance of enamel to diagenetic alteration. Application of water-apatite interaction models suggest that the different kinetic behaviours of the phosphate-water and carbonate-water systems can be used to detect subtle oxygen isotope disequilibria in fossil enamel when intra-individual variations are considered. Selective alteration of the oxygen isotope composition from the carbonate component of Afghan and Greek enamels suggests inorganic isotopic exchange processes. Microbially-induced isotopic exchange for phosphate is demonstrated for the first time in enamel samples from Chad, in association with extensive recrystallization. In Chad, δ 18Op values were derived from partial isotopic exchange with fossil groundwater during early diagenesis. Mass balance calculations using average carbonate content in enamel as a proxy for recrystallization, and the lowest δ 18Op value of dentine as a proxy for the isotopic composition of the diagenetic fluid, indicate that diagenesis can alter δ 18Op by as much as 3‰ in some enamel samples. This diagenetic alteration is also responsible for a decrease in intra-individual variations of up to 1‰ in affected specimens. The effects of diagenesis on δ 18Op values of fossil enamel are not systematic, however, and can only be estimated if sequential δ 18Op and δ 18Oc analyses are performed on fossil enamel and dentine. Reconstruction of large temporal- or spatial-scale paleoclimates based on δ 18Op analyses from mammalian teeth cannot be considered valid if enamel has been affected by bacterial activity or if the data cannot be corrected for diagenetic effects.

Influence of microhardness and fluoride content of tooth structure by fluoride-containing restorative materials

The purpose of this study was to compare the microhardness and the fluoride content of enamel and dentin around fluoride- or non fluoride-containing restorations. Forty extracted human teeth were used and prepared cervical cavities on proximal surface. Experimental teeth were divided into five groups . Group 1 : Prime & Bond NT and Z100, Group 2 Prime & Bond NT and F2000, Group 3 : Scotchbond Multi-purpose and Z100, Group 4 : Scothcbond Multi-purpose and F2000, Group 5 : Fuji II LC. The cavities were filled with dentin adhesives and restorative materials. After each tooth was bisected, one half was tested microharaness and the other half was analyzed the fluoride at the enamel and dentin by an EPMA-WDX device. The results were as follows; 1. There was no statistical difference among the microhardness of enamel surface in all group. 2. The microhardness at dentin of point in Group 2 and point in Grocup 4 was lower than that of normal dentin (p>0.05). 3. There was no statistical difference among the fluoride content of enamel surface in all group. 4. The fluoride content at the dentin of point in Group 2 and 5 were higher than those at point in Group 2 and normal dentin (p point, Group 2 showed higher fluoride content than Group 1 and 3, and Group 5 showed higher fluoride content than other groups.

In vivo studies on lead content of deciduous teeth superficial enamel of preschool children

The amount of lead in the superficial enamel of deciduous teeth from 4- and 5-year-old children was determined by means of an enamel biopsy followed by lead analysis by graphite furnace atomic absorption spectrometry. Children examined in this study ( n=329) attended public preschools in the city of Piracicaba, SP, Brazil. The selection of preschools was based on geographical location: some were located in an industrial area of the city, whereas others were located in an area devoid of industries. The objectives of this study were (1) to test whether enamel biopsies were an appropriate method for lead content population screening in young children; (2) to verify the lead content of superficial enamel of preschool children's deciduous teeth and to compare the results obtained from children exposed to different environments; (3) to analyze how biopsy depth correlated with lead content and affected comparisons between groups. An adhesive tape with a central hole (diameter=1.6 mm) was placed on one of the upper central incisors. Five microliters of 1.6 mol l −1 HCl in 70% glycerol (v/v) were applied to this area for 20 s, followed by a rinse with 5-μl ultrapurified water for 10 s. It was shown that the technique was feasible for population studies on young children. The lead concentration in enamel biopsies from the industrial area children (median: 169 ppm Pb) was significantly higher than that from the children living far from industries (118.1 ppm Pb) ( P<0.0001). Analysis of the data showed that biopsies deeper than 3.9 μm gave more reliable results for comparisons between groups. To our knowledge, this study is the first to use an enamel microbiopsy to characterize a large sample of young children in vivo for lead monitoring in teeth.

Elemental composition of teeth with and without odontoclastic resorption lesions in cats.

To determine elemental composition of teeth with and without odontoclastic resorption lesions (ORL) in cats. Normal teeth from 22 cadaver cats and ORLaffected teeth from 21 cats admitted to the veterinary hospital for dental treatment. An electron microprobe was used to analyze weight percentages of calcium, phosphorus, fluorine, sodium, magnesium, sulfur, potassium, and iron in enamel, dentin, and cementum. Calcium and phosphorus were the most abundant elements. Fluorine, sodium, and magnesium combined were < 5% and sulfur, potassium, and iron combined were < 0.1% of total elemental composition. In enamel of normal teeth, a significant sex-by-jaw location interaction was seen in mean (+/- SD) phosphorus content, which was higher in mandibular teeth of females (1764+/-0.41%) but lower in mandibular teeth of males (16.71+/-0.83%). Mean iron content in dentin of normal teeth was significantly lower in mandibular teeth than maxillary teeth (0.014+/-0.005% vs 0.023+/-0.019%). Mean enamel sodium content was significantly higher (0.77+/-0.046% vs 0.74+/-0.025) and mean enamel iron content was significantly lower (0.017+/-0.008% vs 0.021+/-0.005%) in ORLaffected teeth, compared with normal teeth. In cementum, mean fluorine content was significantly lower (2.98%+/-0.27 vs 2.99+/-0.20%) and mean magnesium content was significantly lower (0.54+/-0.13% vs 0.60+/-0.13%) in ORL affected teeth, compared with normal teeth. Results of our study establish baseline mineral content of enamel, dentin, and cementum for normal teeth in cats. Minimal differences in mineral content of enamel and cementum of normal and ORL-affected teeth were detected.

Defects in mandibular bone area, enamel iron content and dentine formation following gastrectomy in rats

Fourteen 5-week-old male Sprague–Dawley rats were equally divided into two groups, sham-operated and gastrectomized. Tetracycline and calcein were given to label dentine. Four weeks after surgery, blood was collected for measurement of serum iron, calcium and parathyroid hormone (PTH) and the mandibles and maxillae were then removed. Sagittal sections of the maxilla or cross-sections of the mandible were prepared and examined. Backscattered electron images of the maxilla were taken and the iron content at the neck of incisors was measured by energy-dispersive X-ray. The dentine apposition rate in maxillary incisors was measured by fluorescence microscopy. Serum iron was significantly decreased, while PTH was significantly elevated without any change in the serum calcium in gastrectomized rats. Gastrectomy caused a gross loss of iron content in superficial enamel. The dentine apposition rate was significantly reduced by 30%. Both cortical and cancellous bone in the mandibula were significantly reduced. However, the total bone area in gastrectomized rats was similar to that in sham-operated rats. These results suggest that bone resorption was enhanced and dentine formation was reduced after gastrectomy.

Effect of saliva substitutes on mineral content of demineralized and sound dental enamel.

The aim of this in vitro study was to evaluate the effects of commercially available saliva substitutes on the mineral content of pre-demineralized and sound enamel. From 56 bovine incisors 224 enamel specimens were prepared and hand-polished. The specimens were partially covered with nail varnish (control of sound enamel). In group 1, 112 samples were demineralized (18 days; 37 degrees C; pH 5.0) and a portion of the demineralized area was likewise covered with nail varnish. Subsequently, 16 specimens were exposed (14 days; 37 degrees C) to 10 ml of each of several different saliva substitutes (Artisial; Glandosane; Oralube; Saliva medac), or mouthwash solutions (Biotène; Meridol), respectively. Non-carbonated, fluoride-containing mineral water (Eptinger) was used as control. In group 2, the 112 sound enamel specimens were immersed directly in the solutions (without a demineralization period). After immersion, the specimens were cut perpendicular to the surface, and slabs (110 microns) were ground. Contact microradiographs were obtained and studied with a digital image-analyzing system. A dedicated software (TMR 1.24) was used to calculate the mineral content. Sound enamel (group 2) was significantly demineralized after immersion in Biotène and Glandosane (P < 0.001; Kruskal-Wallis). In group 1, mineral loss after storage in Biotène and Glandosane was significantly increased (P < 0.001), compared with the mineral content after demineralization. All other solutions revealed a significant mineral gain (P < 0.01; Wilcoxon), with the most pronounced effects after use of Oralube and mineral water (both containing calcium, phosphates, and fluorides). Therefore, administration of products similar to the last named can be recommended for dentate patients with salivary gland hypofunction.

Unique enamel phenotype associated with amelogenin gene (AMELX) codon 41 point mutation.

Different mutations in the amelogenin gene (AMELX) result in the markedly different enamel phenotypes that are collectively known as amelogenesis imperfecta (AI). We hypothesize that unique phenotypes result from specific genetic mutations. The purpose of this study was to characterize the enamel compositional and structural features associated with a specific AMELX mutation in three families with X-linked AI. We performed mutational analysis by amplifying AMELX exons and sequencing the products. Permanent and primary affected (N = 6) and normal (N = 3) teeth were collected and examined by light, scanning, and transmission electron microscopy. Enamel proteins were evaluated by immunolocalization of amelogenin and amino acid analysis. AI-affected individuals all shared a common AMELX point mutation (C to A change at codon 41). The dental phenotypic findings were remarkably consistent in all affected individuals. The AI enamel was opaque, with numerous prism defects or holes encompassing the entire prism width. Affected crystallites appeared more radiolucent and morphologically less uniform, compared with that of normal enamel. Immunogold labeling with anti-amelogenin antibodies localized amelogenin to the crystallites but not to the inter-crystalline spaces. No immunogold labeling was seen in normal enamel. There was an increased and amelogenin-like protein content in AI enamel (0.95%) compared with normal enamel (0.13%). We conclude that this codon 41 C to A missense point mutation, in a highly conserved region of the AMELX gene, results in a remarkably consistent phenotype.

ESR Study of elephant tooth enamel from the Kärlich-Seeufer site in Germany

Enamel from 6 different positions in a well preserved elephant tooth from the Kärlich-Seeufer site in Germany has been irradiated up to 32 kGy. The X-band ( ν=9.5 GHz) ESR spectra of two subsamples have been decomposed into three real components with Maximum Likelihood Common Factor Analysis (MLCFA). One of these components due to orthorhombic CO − 2 radicals is predominant. Dose response curves for the contributions of these MLCFA components and for different heights in the ESR spectra have been obtained and fitted with different models. Depending on the model, the equivalent dose for the preferably used height at g=1.9973, due to CO − 2, ranges from 70 to 130 Gy. Due to a very low uranium and thorium content in both enamel and dentine (≤∼ 10 ppb) and to an important external γ-attenuation, the ages fluctuate between 300 and 575 ka.

Disturbed enamel formation in wild boars (Sus scrofa L.) from fluoride polluted areas in central Europe

The pathological alterations of enamel structure in the teeth of wild boars from fluoride polluted areas in N-Bohemia (Czech Republic) and S-Saxony (Germany) were studied on a macroscopic and a microscopic level. Mandibular bone fluoride concentration (mg F(-)/kg, dry wt; mean +/-SD, individuals <24 months of age) in the specimens from N-Bohemia (754.3+/-149.6) and S-Saxony (490.8+/-135.1) was significantly higher than that of controls (free of dental fluorosis), originating from the western part of Germany (304.7+/-91.0). Fluoride content in bulk enamel (mg F(-)/kg, ash wt) of fluorotic permanent teeth from N-Bohemia (382.1+/-165.2) and S-Saxony (125.0+/-38.3) was likewise significantly increased over that of non-fluorotic control teeth from W-Germany (33.6+/-26.7). Macroscopically, fluorosed wild boar enamel exhibited opacity and discoloration of varying extent, accentuated perikymata as well as hypoplastic and posteruptive surface defects. Microradiographic and scanning electron microscopic analyses revealed enamel subsurface hypomineralization, accentuated Retzius lines and occurrence of broad, hypomineralized incremental bands of abnormal structure underlying hypoplastic enamel surface defects. The presence of zones of aprismatic enamel was associated with these bands. Incremental bands with altered enamel structure and enamel surface hypoplasias, both denoting a severe disturbance during the secretory stage of amelogenesis, have previously been observed in rodents following acute parenteral fluoride dosing. It is concluded that in the chronically fluoride exposed wild boars periods of especially elevated plasma fluoride levels exerted an acute toxic effect on the secretory ameloblasts. A feature not previously reported from fluorosed enamel was the occurrence of canal-like structures that originated at the broad incremental bands and extended into the external enamel. The presence of these canals presumably results from a delay in the resumption of secretory activity by groups of ameloblasts following a fluoride insult. Based on experimental evidence in domestic pigs and in sheep, the overall subsurface hypomineralization of fluorosed wild boar enamel is attributed to a disturbance of enamel maturation. The distribution of fluorotic enamel changes within the dentition of the wild boars could be related to the developmental sequence of tooth formation in the species. Teeth whose crown formation took place prenatally (deciduous teeth) or largely pre-weaning (permanent first molars) exhibited no or only moderate fluorotic enamel alterations. Based on the extension of enamel surface hypoplasias along the coronoapical axes of the tooth crowns, the timing of excess fluoride exposure that caused a marked disruption of enamel matrix secretion was estimated in specimens with a known date of death. The results indicate that the wild boars had been exposed to a particularly severe fluoride impact during autumn and winter of their first year of life.