Micro determination of carbonate in dental enamel

Morphology and elemental composition of subgingival calculus in two ethnic groups

BACKGROUND

The aim of the present study was to compare the morphology and elemental composition of subgingival calculus between Indo-Pakistani and Caucasian patient groups.

METHODS

Extracted teeth from 14 Indo-Pakistani and 19 Caucasian subjects were collected. Of these, 12 Indo-Pakistani and 10 Caucasian teeth had sufficient subgingival calculus for analysis. Subgingival calculus present on the 22 teeth was classified into six morphological types: 1) crusty/spiny/nodular; 2) ledge/ ring; 3) thin, smooth veneers; 4) finger/fern-like; 5) individual islands/spots; or 6) supramarginal on submarginal. Subgingival calculus was zoned: coronal, mid, and apical. A sample obtained from each zone was subdivided to allow 3 separate analyses: transmission electron microscopic (TEM) x-ray microanalysis for elemental composition, fluoride analysis, and carbonate analysis.

RESULTS

Crusty/spiny/nodular, ledge/ring, and thin, smooth veneers were more commonly found in the Indo-Pakistani group; individual islands were more prevalent in the Caucasian subjects. Supramarginal on submarginal calculus was found only in the Indo-Pakistani group. No finger/fern-like deposits were found. No differences within or between the two ethnic groups were found with regard to calcium:phosphate ratios, fluoride, or carbonate content. However, the Indo-Pakistani group showed significantly lower levels of sodium in apical samples than in coronal samples (ANOVA, F1,16 = 5.98, P= 0.03), and significantly lower levels of sodium (ANOVA, F1,12 = 4.75, P= 0.05) and magnesium (ANOVA, F1,12 = 5.16, P= 0.04) in apical samples than in those from Caucasians. After adjusting for smoking, the magnesium results remained significant (ANOVA, F2,11 = 4.64, P= 0.05).

CONCLUSIONS

Subgingival calculus demonstrated differences in morphology between these two ethnic groups and differences in elemental composition, which may influence its overall solubility and contribute to its greater accretion in the Indo-Pakistani subjects.

The chemical composition of tooth enamel in junctional epidermolysis bullosa

The junctionalis form of epidermolysis bullosa (EBJ) is associated with a number of clinical problems involving tooth enamel, including increased susceptibility to caries. The aim here was to carry out a chemical characterization of the enamel of teeth from EBJ patients compared with that of unaffected controls. The results showed that while protein concentration, amino acid composition and carbonate content were similar in both groups, EBJ enamel contained a significantly reduced mineral per volume content, resulting in enamel hypoplasia. In addition, Western blotting revealed the presence of serum albumin (a known inhibitor of enamel crystal growth) in EBJ enamel. This was not detected in control enamel or in enamel of teeth from patients with the dystrophic form of the disease. It is concluded that EBJ enamel is developmentally compromised and that the enamel defects are commensurate with the reported genetic lesions.

The chemical composition of tooth enamel in recessive dystrophic epidermolysis bullosa: significance with respect to dental caries

Previous reports have linked the prevalence of tooth abnormalities with high caries experience in the different types of epidermolysis bullosa (EB). However, it is not known to what extent the apparent susceptibility to enamel caries is due to disease-related altered enamel chemistry in these cases. The aim of this study was to characterize the enamel of teeth from patients suffering from recessive epidermolysis bullosa dystrophica (rEBD) in terms of its mineral content, carbonate content, protein content, and amino acid composition. The results showed that dental enamel from these patients was essentially normal in terms of its chemistry. It is therefore concluded that the high caries experience in recessive dystrophic epidermolysis bullosa patients is probably related to other factors, such as compromised oral hygiene and prolonged oral clearance due to extensive oral soft tissue damage and a cariogenic diet.

Characterization of the enamel ultrastructure and mineral content in hypoplastic amelogenesis imperfecta

Amelogenesis imperfecta (AI) comprises a diverse group of hereditary enamel disorders that are characterized by hypoplastic and in some cases hypomineralized defects. The specific biochemical abnormalities remain unknown for all AI types, making histologic and chemical analyses of affected dentitions essential for resolving the etiology of AI. The purpose of this investigation was to characterize the ultrastructure and mineral content of smooth hypoplastic AI enamel. The AI enamel showed no evidence of surface pitting and was uniformly reduced in thickness by approximately 60% compared with control enamel. Imbibition studies indicated that the AI enamel was generally porous. The first 30 microns of AI enamel adjacent to the dentinoenamel junction was translucent with poorly formed prisms. Abnormal prism structure was seen throughout the AI enamel. Amorphous, presumably organic material that may have been retained enamel protein was also seen. Although the crystallite widths were similar in both AI and normal enamel, the AI teeth showed areas where the crystallite order and continuity appeared disrupted. The mean mineral content was similar for all variables measured except sodium, which was significantly lower in the AI teeth. The calcium concentration was very low in the AI enamel directly adjacent to the dentinoenamel junction and showed a steeper concentration gradient moving from the dentin to the surface compared with control teeth. It may be concluded that the ameloblasts in smooth hypoplastic AI produce a tissue of reduced thickness, which is excessively porous and displays alterations in its ultrastructural organization.

Carbonate content in developing human and bovine enamel

The present study describes the detailed changes in carbonate distribution throughout the different stages of development in human and bovine enamel, from early formation to maturation. Twenty-two human maxillary and mandibular deciduous anterior teeth and 46 bovine teeth were studied. The major mineral ions, calcium and phosphorus, were also analyzed to facilitate comparison of carbonate content with progressing mineralization. The results showed that as enamel matured and mineral concentration increased, carbonate concentration decreased. The observed decrease in percent carbonate per weight enamel mineral may be due to dilution by an influx of relatively carbonate-free mineral, and could, in part, explain the observed increase in crystallinity of enamel mineral as the tissue matures.

Micro-analysis of mineral saturation within enamel during lactic acid demineralization

In this study, the physicochemical factors responsible for caries-like lesion propagation were investigated by means of a micro-analytical system used to study the fluid within a lesion during a simulation of the decay process. Four 500-microns-thick serial sections prepared from a single human molar were mounted between glass plates with only the natural surface of the tooth exposed. Microwells were then drilled into sound and pre-existing carious regions of the section through one of the plates. These microwells were then filled with fluid under mineral oil, and after a week of equilibration, the natural surface of the section was exposed to a lesion-producing fluid. The concentrations of calcium, phosphate, and hydrogen ions of the fluid in the wells were then followed as a function of time as the lesion advanced. The results of this study, in which lactic acid was used to demineralize enamel, were consistent with those previously reported (Vogel et al., 1987a): The solution within the lesion remained saturated during the acid attack. Differences in initial mobilities of the calcium and phosphate and other ions, a result of the permselectivity of the enamel, increased the concentrations within the lesion and permanently changed the ratio of these ions in the lesion solution. Based on these results, we suggest that the ionic permselectivity of tooth enamel can have a profound effect on the transport of mineral from a caries lesion.

Biochemical and microanalytical methods

Because of the small amounts of material available for study, investigations of plaque, caries lesions in enamel, and antibodies in saliva pose difficult challenges for investigators. Sophisticated biochemical and fluorescence techniques can now be used to investigate the microbial composition of plaque, thereby avoiding the need for tedious culturing techniques from single sites on tooth surfaces. A range of microchemical methodologies is available which greatly facilitates the analysis of plaque fluid, thereby enhancing our understanding of tooth-plaque interactions. The application of a range of novel physiochemical techniques should help to clarify our knowledge of the interactions involved in pellicle formation and elucidate the phenomena involved in the formation of the early caries lesion. A range of techniques is now available for the study of antibodies in saliva. These include ELISA, RIA, and solid-phase immunoassay. The application of these methodologies to the investigation of oral diseases should facilitate our understanding of the pathogenesis of dental maladies at the molecular level.

The influence of carbonate on the atomic structure and reactivity of hydroxyapatite

A series of synthetic carbonated and non-carbonated apatites was investigated using high resolution transmission electron microscopy, and their dissolution behavior was tested under sink conditions, using the rotating disc method. n-Beam lattice images of the apatite samples were of a resolution greater than has been previously reported, and revealed an increase in crystalline disorder with the incorporation of carbonate in the apatite structure. This resulted in an increased rate of dissolution and a decreased activation energy for dissolution for the carbonated apatites. Thus, carbonate increased the reactivity of hydroxyapatite.

Variations in the composition of developing rat incisor enamel

The developing enamel of rat incisors was dissected into a series of samples extending from the newly-formed partially-mineralised matrix to the mature.enamel. Chemical analysis showed that, on a dry weight basis, the tissue achieved the composition of mature enamel well before the completion of mineral uptake. The enamel at this stage was porous and relatively soft. As more mineral was acquired, its hardness increased. Throughout the developing region, the Ca:P ratio remained fairly constant, but the CO2:P and Mg:P ratios both decreased due, apparently, to dilution by an influx of relatively C02- and Mg-free mineral.