Mineral Content of Human and Seal Cementum

Relationship between root resorption and individual variation in the calcium/phosphorous ratio of cementum

INTRODUCTION

The purpose of this study was to investigate whether individual variation in the hardness and chemical composition of the cementum in the root apex affects the degree of root resorption.

METHODS

In a previous study, we evaluated the Vickers hardness scale of 50 extracted teeth. For this study, we classified the 50 extracted teeth into soft, moderate, and hard groups according to the Vickers hardness scale. Then, we randomly selected 7 teeth from each group and measured the resorbed areas of the apical cementum in vitro using human osteoclast precursor cells. We also investigated the calcium/phosphorous (Ca/P) and magnesium/calcium ratios of these 21 extracted teeth using energy-dispersive x-ray microanalysis studies to determine the chemical composition of the cementum in the root apex.

RESULTS

In the pit formation assay, the resorbed area in the soft group showed a greater extent than it did in the moderate and hard groups (P < 0.01). A correlation was noted between the Vickers hardness and the resorbed area of the cementum in the root apex (r = -0.714; P < 0.01). The Ca/P ratios in the soft and moderate groups were lower than the ratio in the hard group (P < 0.01 and P < 0.05, respectively). A correlation was noted between the Vickers hardness and the Ca/P ratio of the cementum in the root apex (r = 0.741; P < 0.01).

CONCLUSIONS

These results suggest that the hardness and Ca/P ratio of the cementum may be involved in root resorption caused by orthodontic forces.

Evaluation of blood cell attachment on Er: YAG laser applied root surface using scanning electron microscopy

BACKGROUND

Periodontal regeneration is dependent on the uninterrupted adhesion, maturation and absorption of fibrin clots to a periodontally compromised root surface. The modification of the root surface with different agents has been used for better fibrin clot formation and blood cell attachment. It is known that Er:YAG laser application on dentin removes the smear layer succesfully.

AIM

The aim of this study is to observe blood cell attachment and fibrin network formation following ER:YAG laser irradiation on periodontally compromised root surfaces in comparison to chemical root conditioning techniques in vitro.

MATERIALS AND METHODS

40 dentin blocks prepared from freshly extracted periodontally compromised hopeless teeth. Specimens were divided in 5 groups; those applied with PBS, EDTA, Citric acid and Er:YAG. They were further divided into two groups: those which had received these applications, and the control group. The specimens were evaluated with scanning electron microscope and micrographs were taken. Smear layer and blood cell attachment scoring was performed.

RESULTS

In the Er:YAG laser applied group, smear layer were totally removed. In the blood applied specimens, better fibrin clot formation and blood cell attachment were observed in the Er:YAG group. In the group that had been applied with citric acid, the smear layer was also removed. The smear layer could not be fully removed in the EDTA group.

CONCLUSION

Er:YAG laser application on the root dentin seems to form a suitable surface for fibrin clot formation and blood cell attachment. Further clinical studies to support these results are necessitated.

Physical properties of root cementum: Part 3. Hardness and elastic modulus after application of light and heavy forces

BACKGROUND

The aims of this investigation were to evaluate the hardness and elastic modulus of untreated human premolar cementum and to investigate the changes after application of light and heavy orthodontic forces.

METHODS

Thirty-six maxillary and mandibular first premolars were collected from 16 prospective orthodontic patients. The patients were assigned to 1 of 2 groups. Group I (light force) consisted of 8 subjects (4 male, 4 female, mean age 14.8 years) who had 25 g of buccally directed orthodontic force applied to the first premolars on 1 side. Group II (heavy force) consisted of 9 subjects (7 male, 2 female, mean age 13.8 years) who had 225 g of buccally directed orthodontic force applied to first premolars on 1 side. Contralateral premolars served as the control in both groups. The force was applied for 4 weeks; then each first premolar was extracted and stored in deionized water. Physical properties were tested on unprepared cementum on buccal and lingual surfaces at the cervical, middle, and apical thirds with an ultra-micro-indentation system.

RESULTS

Mean (+/- standard deviation) hardness of the untreated cementum at the cervical, middle, and apical thirds, respectively, was 0.25 +/- 0.09 GPa, 0.24 +/- 0.07 GPa, and 0.18 +/- 0.06 GPa on the buccal surface and 0.24 +/- 0.08 GPa, 0.24 +/- 0.06 GPa, and 0.21 +/- 0.06 GPa on the lingual surface. Mean elastic modulus at the cervical, middle, and apical thirds, respectively, was 4.4 +/- 2.4 GPa, 3.4 +/- 2.0 GPa, and 2.4 +/- 1.8GPa on the buccal surface and 3.8 +/- 2.1 GPa, 3.2 +/- 1.4 GPa, and 2.4 +/- 1.5 GPa on the lingual surface.

CONCLUSIONS

The mean hardness and elastic modulus of untreated human premolar cementum gradually decreased from cervical to apical regions of the buccal and lingual surfaces. A similar decrease was observed in the experimental teeth of light-force and heavy-force groups. There were no statistically significant differences between the control and experimental teeth; this is probably due to large intraindividual variation.

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.

Root resorption and its association with alterations in physical properties, mineral contents and resorption craters in human premolars following application of light and heavy controlled orthodontic forces

OBJECTIVES

To study the effect of different orthodontic force levels on cementum, investigating from the point of view of its physical properties, alterations in the mineral components, type and location of the resorption craters and the exploration in 3D of space.

DESIGN

In vivo human premolars subjected to heavy and light forces were employed for this study. After a period of movement they were analyzed for hardness and elasticity. Also, the mineral composition measuring Ca, P and F of the cementum root surface was investigated. A new method for volumetric analysis of resorption craters was developed.

RESULTS

There were no significant differences for hardness and elastic modulus between the light and heavy force groups and no significant effects for different tooth positions. Significant inter-individual variation in the Ca, P and F concentrations was noted. Force-related data showed that mean volume of the resorption crater in light-force group was 3.49-fold greater than the control group, and the heavy-force group 11.59-fold more than control group. The heavy force group had 3.31-fold greater total resorption volume then light force group. Buccal cervical and lingual apical regions demonstrated significantly more resorption craters than the other regions. The 2D measurements were strongly correlated to 3D measurements.

CONCLUSION

The application of light and heavy forces did not show any statistically significant differences in hardness and elastic modulus when compared with untreated teeth. The inconsistent increase or decrease of Ca, P and F contents between control and experimental teeth at sites of compression and tension were difficult to explain. There was more resorption by volume in the heavy force group as compared with the light group and controls. Our data also suggested that the high-pressure zones might be more susceptible to resorption after 28 days of force application.

Distribution of fluoride in sound and periodontally diseased human cementum

Fluoride distribution was investigated by an abrasive micro-sampling technique. The fluoride concentration increased with age in both sound and diseased cementum. In sound teeth, the fluoride profiles (distribution of fluoride from the surface to interior) of the middle and apical cementum were similar. In the diseased cementum the profile of the middle region tended to be more variable than that of the apical cementum, suggesting a possible effect of the oral environment on the fluoride profile at this site.

Proteoglycans of bovine cementum: isolation and characterization

The proteoglycans associated with the mineralized matrix of bovine cementum have been studied biochemically and their distribution within this tissue localized immunohistochemically. Both hyaluronate and proteoglycans were fractionated by DEAE-Sephacel ion-exchange chromatography. The proteoglycans eluted in three separate peaks of which two contained alkali labile protein associated with glycosaminoglycans, and one appeared as free glycosaminoglycan chains. Analysis of the glycosaminoglycans identified chondroitin sulfate as the predominant species, although minor quantities of dermatan sulfate and heparan sulfate were also identified. Agarose-acrylamide gel electrophoresis and Sepharose CL-6B molecular sieve chromatography of the proteoglycans indicated them to be smaller in size with respect to periodontal ligament and gingival proteoglycans, but similar to bone and dentine proteoglycans. Amino acid analyses indicated subtle differences between cementum and bone proteoglycans. Using a monoclonal antibody (9-A-2) which recognizes the unsaturated disaccharide of chondroitinase ACII-digested glycosaminoglycans, chondroitin sulfate was identified in the pericellular environment within the lacunae housing the cementoblasts as well as in the extracellular matrix of cementum.

Fluoride distribution and histological structure of human cementum

Thirty-one teeth taken post-mortem from 10 subjects aged from 40 to 66 years were studied. A close relationship was found between fluoride (F) distribution and histological structure. Although, as in all mineralized tissues, F concentrations tended to be highest towards the external surface, individual patterns of F distribution also seemed to reflect the histological pattern, especially the distribution of cellular or acellular cementum. In general, F concentrations were high in acellular and low in cellular cementum.

Electron probe study of human and red deer cementum and root dentin

A topographical description of the concentration profiles of Ca, P, Mg, Zn, F, S, and K in human and red deer cementum and root dentin is given. The concentrations reported should be regarded as semiquantitative values. A downward slope of the Ca, P and Mg profiles toward the pulpal cavity seemed largely to correspond with the secondary dentin. Marked elevations of the Zn profiles, modest elevations of the F profiles, and in a few instances of the S profiles, toward root surface and pulpal cavity were registered. In a couple of scans a slight elevation of the K profile toward the root surface ws observed. A high degree of concordance in human and red deer teeth was ascertained.

Electron probe microanalysis of cementum and underlying dentin in young permanent teeth

The amount of calcium, phosphorus, and magnesium in human cementum and subjacent dentin of young permanent teeth was studied with the use of an electron probe microanalyzer and was correlated with morphology with the use of a scanning electron microscope. The mineral content of the cementum and the granular layer of Tomes was significantly lower than that of tubular dentin and the hypermineralized zone.