Morphology and chemical composition of dental calculi mainly composed of whitlockite.

The morphology and chemical composition of two subgingival calculus samples, which were composed of magnesium-whitlockite with a Mg/Ca molar ratio of approximately 0.1 as shown by X-ray powder diffraction, were analyzed semiquantitatively using energy-dispersive spectroscopy (EDS) combined with scanning electron microscopy (SEM). The Ca/P molar ratio values for 33 EDS-analyzed materials ranged from 1.24 to 2.03 with an average of 1.49, and the (Mg+Ca)/P molar ratio values ranged from 1.43 to 2.28 with an average of 1.63. The average Mg/Ca molar ratio was 0.10, a value very close to that obtained by X-ray diffraction analysis. The EDS-analyzed materials were grouped morphologically into three types; Type A materials were typical rhombohedral crystals, Type B were crystals of ill-defined form or small crystallite aggregations and Type C materials had a small granular structure or were amorphous. The values of (Mg+Ca)/P molar ratio for Type A ranged from 1.57 to 2.28 and averaged 1.81, those for Type B ranged from 1.43 to 1.56 and averaged 1.48, and those for Type C ranged from 1.46 to 2.06 and averaged 1.62. Type A crystals had higher molar ratios while Type B crystallites had values similar to that of whitlockite. Type C materials covered the ranges of both Type A and Type B. These results show that the materials resembling whitlockite morphologically did not have the (Mg+Ca)/P ratio of whitlockite and vice versa. This suggests that whitlockite crystals may substitute some ions for PO4 as well as Mg for Ca to a larger extent than thought previously, and that care is needed in the identification of these materials.

Scanning electron microscopy and electron probe microanalyses of the crystalline components of human and animal dental calculi.

A review of the use of scanning electron microscopy (SEM) and electron probe microanalyses in the study of dental calculus showed that such studies provided confirmatory and supplementary data on the morphological features of human dental calculi but gave only limited information on the identity of the crystalline or inorganic components. This study aimed to explore the potential of combined SEM and microanalyses in the identification of the crystalline components of the human and animal dental calculi. Human and animal calculi were analyzed. Identification of the crystalline components were made based on the combined information of the morphology (SEM) and Ca/P molar ratios of the crystals with the morphology and Ca/P molar ratio of synthetic calcium phosphates (brushite or DCPD; octacalcium phosphate, OCP; Mg-substituted whitlockite, beta-TCMP; CO3-substituted apatite, (CHA); and calcite. SEM showed similarities in morphological features of human and animal dental calculi but differences in the forms of crystals present. Microanalyses and crystal morphology data suggested the presence of CaCO3 (calcite) and CHA in the animal (cat, dog, tiger) and of OCP, beta-TCMP and CHA in human dental calculi. X-ray diffraction and infrared (IR) absorption analyses confirmed these results. This exploratory study demonstrated that by taking into consideration what is known about the crystalline components of human and animal dental calculi, combined SEM and microanalyses can provide qualitative identification.

Analytical transmission electron microscopy of the distribution of elements in human supragingival dental calculus.

Thin sections of supragingival calculus from lower anterior teeth of 26 subjects were examined. From each specimen, an average of 10 spectra was collected from a densely-mineralized area less than 100 micron diameter. Only spectra showing peaks for minor elements or unusual Ca:P peak ratios were collected, stored and analysed semi-quantitatively. Ca:P weight percentage ratios varied within each specimen. Although most lay within the range 1.6 to 1.8, ratios of less than 1 and greater than 22 were obtained. The latter indicated the presence of some P-free Ca salts. The minor elements Mg and Zn occurred most frequently but the concentration within a specimen varied from the undetectable up to approx. 3 per cent by weight for Mg and 1 per cent for Zn. Low peaks for Ti, Ni, Co, As, Sr, Zr, Mo, Cd and Sn occurred in 1 to 3 spectra from a few specimens, indicating localized areas rich in one of these elements. Low to questionable Pb peaks were present in at least one spectrum from each of 20 specimens. There is thus a non-homogeneous distribution of Ca and P and of many minor elements throughout the calculus.

In vivo remineralization of human enamel and dental calculus formation.

The aim of this investigation was to determine the inorganic composition and the surface morphology of remineralized enamel areas and of dental calculus in heavy-calculus-formers (five subjects) and to compare these results with those of non-calculus-formers (two subjects). Electron probe micro-analysis (EPMA) was carried out on sound, acid-etched, and in vivo remineralized enamel samples from heavy- and non-calculus-formers. The mean values of Ca, P, Na, Mg, Al, Si, S, Cl, and K were compared with the SEM morphology. EPMA measurements showed no significant differences in the Ca/P ratio of the surface layers of prism-oriented and/or homogeneous enamel remineralization. The variations of remineralization pattern after acid-etching are similar in teeth from heavy dental-calculus-forming patients and in teeth from non-calculus-formers. The SEM appearances of remineralized areas and of the inner surface of mature dental calculus must be considered to be totally different. The experiments carried out suggest that the remineralization of enamel is not related to the formation of calculus.

A case report of unusual dental calculus formation.

A case is presented in which an unusual amount of intraoral calculus was seen in a 59-year-old woman. The deposits completely covered all surfaces of most teeth and extended over the facial and lingual gingivae. The relationship between certain chemical salivary parameters and heavy calculus formers is briefly described.

Relations between early dental calculus production and calcium and phosphate parameters of salivary fractions.

A pilot study was carried out to obtain an idea of the strength of the relations between early mandibular calculus production in humans and amounts and concentrations of bound calcium and phosphate in three salivary fractions. The salivary fractions were: (1) the spontaneous precipitate from incubated whole saliva, (2) the spontaneous precipitate from incubated centrifugal (20,000 X g) saliva supernatant and (3) the fresh centrifugal saliva sediment. Strong and highly significant correlations were found for the amount and concentration of calcium in the fresh sediment and whole saliva precipitate fractions. Although the correlations for the calcium parameters of the saliva supernatant precipitate were not significant, there were significant differences in these parameters between low and high calculus formers as determined by Student's t test. Relations between calculus production and amount and concentration of phosphate were weaker and not significant for all fractions. The data suggest that the amount or concentration of calcium in fresh saliva sediment is an important determinant of early mandibular calculus production.