Effect of 2.94 µm Er: YAG laser on the chemical composition of hard tissues.

The aim was to investigate the effect of the Er-YAG laser radiation on morphology and chemical composition of enamel, dentin, and bone. The specimens of the three groups were irradiated with a very long pulse mode (VLP) of 2.94 µm Er-YAG laser with 100 mJ pulse energy and energy density of 8.42 J/ c m 2 for 30 s, at a repetition rate of 15 Hz. The organic and inorganic content of the samples were investigated by Fourier Transforms Infrared spectroscopy (FTIR). The morphological characteristics were investigated with scanning electron microscopy (SEM) and elemental analysis (calcium and phosphorus) with energy-dispersive X-ray spectroscopy (EDX). FTIR data were analyzed with a One-Way ANCOVA test and EDX data with the independent sample t-test. Following the laser radiation, FTIR showed a significant decrease in the organic content of all tissues. The weight percentage (wt %) calcium content of dentin and bone increased significantly following irradiation with a p-value of .002 for both tissues, but the wt % of phosphorus content was not influenced significantly. The morphological alterations expressed signs of fusion in all the samples.

Physical properties of root cementum: part 6. A comparative quantitative analysis of the mineral composition of human premolar cementum after the application of orthodontic forces.

INTRODUCTION: The aim of this study was to examine quantitatively with electron probe microanalysis (EPMA) the calcium (Ca), phosphorus (P), and fluoride (F) concentrations in human first premolar cementum after the application of light and heavy orthodontic forces. METHODS: Thirty-six maxillary and mandibular first premolars (18 experimental, 18 control) were extracted from 16 subjects (10 male, 6 female; mean age, 13.9 years; range, 11.7-16.1 years) who were randomly assigned to the light-force or the heavy-force group. In the light-force group, 25 g of buccally directed force was applied to the experimental premolar; in the heavy-force group, 225 g of buccally directed force was applied to the experimental premolar. The contralateral premolar served as the control. The experimental and control premolars were extracted 28 or 29 days after initial force application and prepared for EPMA. The Ca, P, and F concentrations were measured on the buccal and lingual surfaces at the midpoint of the cervical, middle, and apical thirds of the root from the outer to the middle to the inner third of the cementum. RESULTS: Little change was found in the mineral composition of cementum after the application of light forces; however, there was a trend toward an increase in the mineral composition (Ca, P, and F) of cementum at various areas of periodontal ligament compression. The application of heavy forces caused a significant (P = .000) decrease in the Ca concentration of cementum at certain areas of periodontal ligament tension. The application of both light and heavy orthodontic forces did not appear to influence the F concentrations in cementum. CONCLUSIONS: Heavy orthodontic forces cause alterations in the mineral content of cementum; light forces cause little change.

Physical properties of root cementum: Part 4. Quantitative analysis of the mineral composition of human premolar cementum.

BACKGROUND: The aim of this study was to perform a quantitative analysis of the calcium (Ca), phosphorus (P), and fluoride (F) concentrations in human first premolars. METHODS: This study was conducted on 18 maxillary or mandibular first premolars that were collected from 16 prospective orthodontic patients (10 male, 6 female), mean age 13.9 years (range, 11.7-16.1 years), requiring first premolar extractions. After extraction, the teeth were prepared for electron probe microanalysis. The Ca, P, and F concentrations were measured on the buccal and lingual surfaces at the midpoint of the cervical, middle, and apical thirds of the root from the outer to middle to inner third of the cementum. RESULTS AND CONCLUSIONS: In first premolar cementum, there was significant interindividual variation in the Ca, P, and F concentrations ( P = .024, .017, and .000, respectively). There was no significant difference in the Ca, P, and F concentrations of cementum between the buccal and lingual surfaces, except for a significantly higher F content at the cervical region on the buccal surface ( P = .000). There was a decreasing gradient in the Ca, P, and F concentrations from the cervical to the apical third of the root, which was highly significant from the cervical to middle third ( P = .000) and from the middle to apical third ( P = .000), except for F, for which there was no significant difference from the cervical to the middle third on the lingual surface ( P = .966). There was a significant increasing gradient in the Ca and P concentrations from the outer to inner third of cementum at the cervical ( P < .01) and middle ( P < .01) thirds of the root but no significant difference at the apical third of the root. For F, there was a significant decreasing gradient from the outer to the inner third of cementum at the cervical ( P < .01), middle ( P < .01) and apical ( P < .01) thirds of the root.

Fluoride profiles of perikymata in enamel surfaces of human premolars.

Twenty-five premolars (from Nagoya, Japan < 0.1 parts/10(-6)F in drinking water) were sampled to determine the fluoride content in imbrication lines of Retzius between the grooves and ridges of perikymata on the enamel surface. Eight small windows were formed on each surface in groove and ridge regions using an etched microsampling technique. By using a regression curve, y = ax(-b), fluoride concentrations were compared at depths of 1, 3, 5, 10, 20, 30 and 50 microm in the perikymata regions. Fluoride concentrations increased gradually from the age of 10 to 12 years on the premolar surfaces, but were significantly higher in 12-year-olds or older (erupted teeth) than in 10-year-olds or younger (unerupted teeth). No obvious difference in fluoride concentrations was found between males and females. In the outermost enamel ( < 5 microm depth), fluoride concentrations were significantly higher in the grooves than the ridges of the perikymata. Comparison of the exponential regression coefficients (-b) of the fluoride profiles showed a significant difference between the grooves and ridges. It was concluded that fluoride concentrations and profiles were higher in grooves than in ridges of perikymata, probably because they are naturally porous and are stagnation areas attracting dental plaque.

Fluoride concentrations and distribution in premolars of children from low and optimal fluoride areas.

We have compared the fluoride (F) concentrations from the enamel surface to the dentino-enamel junction (DEJ), and through dentine to the dentino-pulpal junction (DPJ) in premolars extracted from school children in Chemnitz (former Karl-Marx-Stadt), Germany (F: 1.0 ppm in the water supply), Erfurt, Germany (F: 0.2 ppm in the water supply) and Nagoya, Japan (F: 0.1 ppm in the water supply). In teeth from children in Cheminitz, Erfurt and Nagoya, the profiles of F distribution using an abrasive microsampling technique revealed high F concentrations in the enamel surface, with a substantial decrease towards a plateau in the interior. In dentine the F concentrations were higher than in enamel, and also decreased to a plateau from the DEJ, thereafter increasing considerably towards the DPJ. F concentrations at any depth in the enamel and dentine of teeth from Chemnitz were 2-3 times higher than those in Erfurt and Nagoya. There was no significant difference in F concentrations or distributions between Erfurt and Nagoya. Close to the DEJ in both enamel and dentine as well as the enamel surface and the DPJ side of dentine, higher F concentrations were observed in Chemnitz compared with Erfurt and Nagoya.

Hexahedrally based crystals in human tooth enamel.

Mg-containing calcium phosphate crystals including pseudocuboidal, rhombohedral shapes and groupings of quadrangular blades cubically arranged were found in human tooth enamel by scanning electron microscopy and by electron probe microanalysis. In caries-free old enamel, these hexahedrally based crystals measuring 0.5-2.5 microns in length were observed in some crevices of tufts and lamellae. The crystals were rarely seen in the inner crevices of caries-free exfoliated deciduous enamel and none could be seen in sound young enamel. In brown-coloured old enamel possessing arrested caries with lamellae, some of the lamellae contained crystals measuring 0.1-1.5 mu in length adjacent to half-dissolved prisms. These crystals, identified as Mg-containing whitlockite, will grow during a long period after eruption of the tooth or during the enamel caries process.

Mineral content of the innermost enamel in erupted human teeth.

It has been said that the innermost enamel of erupted human teeth is either a hyper- or a hypomineralized layer. Using SEM-EDX, in the present study, the Ca and P mineral contents of the innermost 10-15 microns enamel showing a highly negative birefringence (IE-I) were analyzed and compared with those of the adjacent inner enamel (IE-II) in each cuspal-third, mid-coronal, and cervical-third region. The Ca content in the IE-I zone was significantly lower than that in the IE-II zone in the mid-coronal and cervical-third regions, whereas the significant difference of P content was seen only in the cervical-third region. In the other areas, the IE-I zone tended to be lower than the IE-II zone. These significant and no significant differences of Ca and P contents may be due to the difference in the amount of organic substance in the IE-II zone of the three regions, and that of these mineralization rates after eruption of a tooth.

Retention of lead and cadmium in prehistoric and modern human teeth.

In 5000-year-old premolars from Nubia and in 500-year-old teeth from Greenland, the lead concentrations were very low; modern teeth contained 10-100 times more lead. In contrast, cadmium concentrations varied by 30-fold in the two prehistorical populations; modern-day cadmium levels were in the lower range of this interval. These data suggest that, when compared to preindustrial exposures, the impact of current environmental lead pollution is considerable, while that of cadmium pollution is much less.

Differences in fluoride concentrations in the enamel surfaces of lower first premolars from young human males and females.

There are unconfirmed, reported differences in fluoride concentration in the tooth surfaces of male and female children whose average age was 13.5 yr (range 11.5-15.7 yr) and whose teeth might therefore have been exposed for 2-3 yr after eruption to the oral environment. Thirty-two unerupted and 24 erupted mandibular first premolars were now examined. These had been extracted for orthodontic reasons from children aged from 9 to 10 yr. Samples were removed by acid etching from small areas of the enamel surface, and the fluoride and phosphorus concentrations determined with an electrode and by colorimetry, respectively. Three sites on the buccal surface and one site in the centre of the lingual surface were investigated. Fluoride concentrations were higher in erupted than in unerupted enamel. The fluoride concentration of erupted enamel from the female teeth was significantly higher than that of the males (in contrast to the previous findings), although no analogous differences emerged in the fluoride concentrations of the unerupted enamel.