A study of the dental pulp glycosamino-glycans from permanent human teeth and rat and rabbit incisors

Histological evaluation of different concentrations of hyaluronic-acid-added zinc oxide eugenol on rat molar pulp

Hyaluronic acid (HA), known for diverse properties, was investigated for its potential in dental pulp therapy. This study investigated the potential of HA in dental pulp therapy by examining the physical properties and effects of zinc oxide eugenol (ZOE) pulpotomy materials containing varying HA concentrations on rat molar teeth. In vitro tests assessed compressive strength and hardness of ZOE materials blended with HA (0.5%, 1%, 3%) and HA gels (0.54%, 0.8%). 120 samples, encompassing the control group, underwent compressive strength testing, while 60 samples were designated for hardness assessment. In vivo experiments on rat molars studied histological effects of HA-containing ZOE on dental pulp over 1 week and 1 month. Gels with HA concentrations of 0.5%, 1%, and 0.54% were used in pulpotomy on 22 rats. Each rat underwent the procedure on four teeth, with one tooth serving as a control, totaling 88 teeth subjected to the intervention. In the analyses, SPSS 22.0 was used and the significance level was set at P = 0.05. Findings showed that HA at 0.5% maintained compressive strength, but higher concentrations decreased mechanical properties significantly (P = 0.001). Histological assessments indicated better outcomes with lower HA concentrations in terms of odontoblast layer continuity (P = 0.005 at 1 month) and pulp vitality (P = 0.001 at 1 week and P = 0.018 at 1 month). The study suggests HA holds promise for pulpotomy and regenerative endodontic treatments, but further research is needed to understand long-term clinical implications.

Ex-vivo recellularisation and stem cell differentiation of a decellularised rat dental pulp matrix

Implementing the principles of tissue engineering within the clinical management of non-vital immature permanent teeth is of clinical interest. However, the ideal scaffold remains elusive. The aim of this work was to assess the feasibility of decellularising rat dental pulp tissue and evaluate the ability of such scaffold to support stem cell repopulation. Rat dental pulps were retrieved and divided into control and decellularised groups. The decellularisation protocol incorporated a low detergent concentration and hypotonic buffers. After decellularisation, the scaffolds were characterised histologically, immunohistochemistry and the residual DNA content quantified. Surface topography was also viewed under scanning electron microscopy. Biocompatibility was evaluated using cytotoxicity assays utilising L-929 cell line. Decellularised scaffolds were recellularised with human dental pulp stem cells up to 14 days in vitro. Cellular viability was assessed using LIVE/DEAD stain kit and the recellularised scaffolds were further assessed histologically and immunolabelled using makers for odontoblastic differentiation, cytoskeleton components and growth factors. Analysis of the decellularised scaffolds revealed an acellular matrix with histological preservation of structural components. Decellularised scaffolds were biocompatible and able to support stem cell survival following recellularisation. Immunolabelling of the recellularised scaffolds demonstrated positive cellular expression against the tested markers in culture. This study has demonstrated the feasibility of developing a biocompatible decellularised dental pulp scaffold, which is able to support dental pulp stem cell repopulation. Clinically, decellularised pulp tissue could possibly be a suitable scaffold for use within regenerative (reparative) endodontic techniques.

Hydrogels and Dentin-Pulp Complex Regeneration: From the Benchtop to Clinical Translation

Dentin-pulp complex is a term which refers to the dental pulp (DP) surrounded by dentin along its peripheries. Dentin and dental pulp are highly specialized tissues, which can be affected by various insults, primarily by dental caries. Regeneration of the dentin-pulp complex is of paramount importance to regain tooth vitality. The regenerative endodontic procedure (REP) is a relatively current approach, which aims to regenerate the dentin-pulp complex through stimulating the differentiation of resident or transplanted stem/progenitor cells. Hydrogel-based scaffolds are a unique category of three dimensional polymeric networks with high water content. They are hydrophilic, biocompatible, with tunable degradation patterns and mechanical properties, in addition to the ability to be loaded with various bioactive molecules. Furthermore, hydrogels have a considerable degree of flexibility and elasticity, mimicking the cell extracellular matrix (ECM), particularly that of the DP. The current review presents how for dentin-pulp complex regeneration, the application of injectable hydrogels combined with stem/progenitor cells could represent a promising approach. According to the source of the polymeric chain forming the hydrogel, they can be classified into natural, synthetic or hybrid hydrogels, combining natural and synthetic ones. Natural polymers are bioactive, highly biocompatible, and biodegradable by naturally occurring enzymes or via hydrolysis. On the other hand, synthetic polymers offer tunable mechanical properties, thermostability and durability as compared to natural hydrogels. Hybrid hydrogels combine the benefits of synthetic and natural polymers. Hydrogels can be biofunctionalized with cell-binding sequences as arginine-glycine-aspartic acid (RGD), can be used for local delivery of bioactive molecules and cellularized with stem cells for dentin-pulp regeneration. Formulating a hydrogel scaffold material fulfilling the required criteria in regenerative endodontics is still an area of active research, which shows promising potential for replacing conventional endodontic treatments in the near future.

Local regeneration of dentin-pulp complex using controlled release of fgf-2 and naturally derived sponge-like scaffolds

Restorative and endodontic procedures have been recently developed in an attempt to preserve the vitality of dental pulp after exposure to external stimuli, such as caries infection or traumatic injury. When damage to dental pulp is reversible, pulp wound healing can proceed, whereas irreversible damage induces pathological changes in dental pulp, eventually requiring its removal. Nonvital teeth lose their defensive abilities and become severely damaged, resulting in extraction. Development of regeneration therapy for the dentin-pulp complex is important to overcome limitations with presently available therapies. Three strategies to regenerate the dentin-pulp complex have been proposed; regeneration of the entire tooth, local regeneration of the dentin-pulp complex from amputated dental pulp, and regeneration of dental pulp from apical dental pulp or periapical tissues. In this paper, we focus on the local regeneration of the dentin-pulp complex by application of exogenous growth factors and scaffolds to amputated dental pulp.

Effects of hyaluronic acid sponge as a scaffold on odontoblastic cell line and amputated dental pulp

It is important to develop a suitable three-dimensional scaffold for the regeneration therapy of dental pulp. In the present study, the effects of hyaluronic acid (HA) sponge on responses of the odontoblastic cell line (KN-3 cells) in vitro, as well as responses of amputated dental pulp of rat molar in vivo, were examined. In vitro, KN-3 cells adhered to the stable structure of HA sponge and that of collagen sponge. In vivo, dental pulp proliferation and vessel invasion were observed in both sponges implanted at dentin defect area above amputated dental pulp, and the cell-rich reorganizing tissue was observed in the dentin defect when HA sponge was implanted as compared with collagen sponge. Expression levels of IL-6 and TNF-alpha in KN-3 cells seeded in HA sponge were nearly the same with those in the cells seeded in collagen sponge, while the numbers (0.67 x 10(3) at 1 week and 0.7 x 10(3) at 3 weeks) of granulated leukocytes that invaded into HA sponge from amputated dental pulp was significantly lower than those (1.22 x 10(3) at 1 week and 1.1 x 10(3) at 3 weeks) of collagen sponge (p < 0.01 at 1 week and p < 0.05 at 3 weeks). These results suggest that HA sponge has an appropriate structure, biocompatibility, and biodegradation for use as a scaffold for dental pulp regeneration.

Distribution of biglycan and decorin in rat dental tissue

Biglycan and decorin are small leucine-rich proteoglycans that play several biological and structural roles in different tissues and organs. Several reports have indicated that biglycan participates in odontoblast and ameloblast differentiation and in the calcification process. In the present study we show that the expression of biglycan changes from within the ameloblasts and odontoblasts to the extracellular space according to the stage of animal development. In predentin and in the pulp space, however, biglycan was continually expressed throughout the period of investigation. In contrast, decorin was absent in odontoblasts and in ameloblasts and was exclusively expressed in predentin throughout the period of observation. In young rats, however, decorin was expressed in the extracellular spaces of the pulp, where it was concentrated mainly in the peripheral pulp.

Developmental changes and regional differences in histochemical localization of hyaluronan and versican in postnatal molar dental pulp

AIM

The main aim of this study was to investigate the developmental changes in the distribution patterns of hyaluronan (HA) and versican in postnatal rat molar dental pulp, in order to confirm the hypothesis that the distribution of both molecules can vary with physiological conditions in the dental pulp.

METHODOLOGY

Thirty postnatal Sprague-Dawley rats, 1, 7, 14, 21, 28, 35, 42 and 49 days old, were used for this study. Immunohistochemistry for versican with monoclonal antibodies 12C5 and CS-56 and histochemical staining for HA with HA-binding protein were applied to paraffin sections of the mandibular first molars at each age.

RESULTS

At day 1, both molecules were evenly distributed in the interior parts of the pulp, but strong reactions for both molecules appeared in the subodontoblastic layer of the coronal pulp by the completion of crown formation. However, a strong reaction for HA and a weak reaction for versican were seen in the subodontoblastic layer of the radicular pulp. Furthermore, a versican-deficient, low-HA area first appeared in the interior of the coronal pulp at day 42 and expanded at day 49.

CONCLUSIONS

Distribution of hyaluronan and versican in the dental pulp varied with age and also showed regional differences between the coronal and the radicular pulp, and this supports the hypothesis described above.

Proteoglycans in dentinogenesis

The predominant proteoglycans present in predentin and dentin are the chondroitin-sulphate-rich decorin and biglycan and the keratan-sulphate-rich lumican and fibromodulin. These are small, interstitial, leucine-rich proteoglycans which have recently been shown to exist in gradients across the predentin. Antibodies recognizing chondroitin sulphate show a decreasing gradient from the pulpal aspect toward the mineralizing front, the converse being true for keratan sulphate. Antidecorin shows an increase toward the mineralization front. Evidence from biochemical, autoradiographic, and immunohistochemical studies implies that such changes may be brought about by gradients of metalloproteinases. This offers the possibility that the proteoglycans organize the collagen network for receipt of phosphoproteins and phospholipids, the former being evident only at the onset of dentin formation. The suggestion is raised that glycosaminoglycan-depleted leucine-rich protein cores act as sequester points for receipt of phosphoproteins in particular. The rigid, spatially oriented glycosaminoglycan chains on decorin and biglycan are known to bind calcium and may feature directly in mineral initiation.

Histochemical localization of hyaluronan and versican in the rat molar dental pulp

The distribution of hyaluronan and versican in the dental pulp of the young rat was mapped histochemically. The pattern of staining showed considerable variation between different teeth and different specimens. The most common pattern was a strong reaction for hyaluronan and a weak reaction for versican in the subodontoblastic region, with the reverse deeper in the pulp. This was not an entirely consistent pattern and there was considerable regional variation in the staining intensity for both molecules. The localization of these molecules at similar sites could thus indicate related roles in the connective tissue matrix rather than any chemical bonding between them.

Identification, partial characterization, and distribution of versican and link protein in bovine dental pulp

The dynamics of changes in the cellularity and extracellular matrix composition of dental pulp varies considerably during tooth development and maturation. In this paper, we studied matrix proteoglycans where we hypothesized that they played important roles in structural, spatial, and transport aspects of pulpal development and maintenance. The pulpal tissue was collected from partially erupted bovine incisors, pulverized, and then extracted with 6 M guanidine-HCl. The extract was subjected to anion column chromatography (DEAE-8HR), and the fractions collected were screened by dot-blot immunoassay by means of monoclonal antibodies generated against 4- and 6-sulfated chondroitin sulfate isomers, and keratan sulfate, 2-B-6, 3-B-3, and 5-D-4, respectively. The chondroitin-6-sulfate was the major glycosaminoglycan species and occurred as a large-molecular-weight proteoglycan (> 500 kDa). After further purification, it was subjected to agarose/acrylamide composite gel electrophoresis, and it migrated as a single band stained with Stains-All. The band was immunopositive against antibody 3-B-3 by Western blot analysis. The partial amino acid sequence analyses of the core protein clearly indicated this molecule to be versican. The presence of link protein was also confirmed by Western blot analysis with an anti-link protein monoclonal antibody, 8-A-4. Furthermore, immunohistochemical study indicated that the distributions of versican and link protein coincide in the dental pulp and are enriched in the peripheral area of the tissue just beneath the odontoblast layer. Since the dental pulp contains hyaluronan, versican may bind to hyaluronan via its hyaluronan-binding domain, where this association is stabilized by link protein. This complex, then, could form large hydrated proteoglycan aggregates that fill the extracellular space, support odontoblasts, and/or facilitate the transport function of metabolites and nutrients within the tissue.

The identification of proteoglycan-associated mRNAs in human dental pulp cells

Characterization of the dental pulp proteoglycans has been largely confined to the glycosaminoglycan component of the proteoglycan molecule, while the protein core has received little attention. This study was conducted to identify mRNAs of previously well-characterized proteoglycans-biglycan, decorin and versican-and link protein in dental pulp cells. Dermal fibroblasts were used as a positive control. Oligonucleotide probes were constructed based on published sequences for the four proteins from human tissues. Total RNA was isolated from cultured human pulp and dermal cells, separated according to size by formaldehyde gel electrophoresis and subsequently transferred to a nylon filter. Northern hybridizations using the oligonucleotide probes revealed the expression of biglycan, decorin, versican and link protein mRNAs. Biglycan and decorin are small proteoglycans that have a regulatory effect on collagen fibrillogenesis. Assuming expression of link protein and versican in vivo, the larger proteoglycans in the dental pulp are capable of forming large proteoglycan aggregates.

Isolation and characterization of the proteoglycans synthesized by adult human pulp fibroblasts in vitro

The proteoglycans synthesized by fibroblasts derived from healthy human adult dental pulps have been isolated and characterized on the basis of their glycosaminoglycan content, molecular size and charge. The proteoglycans were identified by their labelling with [35S] sulphate and susceptibility to digestion by papain. The sulphated glycosaminoglycans associated with the proteoglycans were identified following specific enzymatic and chemical degradations as chondroitin sulphate, dermatan sulphate and heparan sulphate. Dermatan sulphate and chondroitin sulphate and heparan sulphate were the principal glycosaminoglycans associated with the cell layers. The proteoglycans could be fractionated on the basis of their charge and size into a number of heterogeneous pools. The principal proteoglycans isolated were small and contained either chondroitin sulphate or dermatan sulphate and most likely correspond to decorin and biglycan. Other molecules with features similar to versican and syndecan were also identified.

Localization of chondroitin sulphate and dermatan sulphate in human dental pulps--an immunohistochemical study

The distribution of dermatan sulphate and chondroitin sulphate in human dental pulps has been assessed using monoclonal antibodies and immunoperoxidase localization techniques. The pulpal tissues were reacted with specific antibodies following pretreatment of the sections with chondroitinase ACII or chondroitinase ABC. Both the 4- and 6-sulphates isomers of chondroitin sulphate were detected in the tissues studied. Very little dermatan sulphate could be detected. These glycosaminoglycans appeared throughout the pulpal connective tissues with a particularly strong localization to the region adjacent to the odontoblastic and predentine layers. Such distribution strongly implicates chondroitin sulphate in the mineralization process of human dentine.

A chondroitin sulfate epitope in mammalian dental pulp and its developmental expression in mouse dental papilla

The molecular specificity of the dental papilla of a bell-stage tooth was studied by production of dental-papilla-reactive monoclonal antibodies (Mabs). One of the Mabs, designated 7C5, recognized an epitope present in glycosaminoglycan. Several lines of evidence suggested that the 7C5-epitope consists of chondroitin 6-sulfate. The Mab did not react with mouse dental epithelium, but reacted uniformly with mesenchymal tissue in the mandibular process and accumulated in the dental sac and in the papilla of bell-stage tooth germs. The 7C5-staining was lost from the differentiating odontoblasts, while the staining in the molar tooth papilla was accumulated in the subodontoblastic layer. In the developing mouse incisor, the 7C5-epitope was restricted to the lingual-posterior area. The 7C5-epitope was also present in pulpal tissue and predentin of different types of teeth of various mammalian species, including man, sheep, swine, and rat. Collagenase pre-treatment of tissue sections abolished the bulk of the 7C5-reactivity in peridental mesenchyme during embryonic stages while leaving the staining of the dental papilla intact. In newborn and adult teeth, collagenase also impaired the reactivity in the pulp except for the subodontoblastic layer. This suggests the existence of different subpopulations of the 7C5-epitope containing proteoglycans in dental papilla and pulp. A high-molecular-weight proteoglycan, sensitive to chondroitinase ABC but not to heparinase or heparitinase, was immunoprecipitated by 7C5 from extracts of bell-stage mouse tooth germs. We suggest that the evolutionary conservation of chondroitin 6-sulfate in the dental pulp reflects its properties as non-terminally differentiated tissue and perhaps the retention of a potential to differentiate to odontoblasts.

In vivo and in vitro glycosaminoglycans from human dental pulp

A qualitative assessment was made of the type of glycosaminoglycans (GAG) present in normal human dental pulp using electrophoresis on cellulose-acetate plates. A comparison was also made between the GAG derived directly from the dental pulp (in vivo) and those derived from cultured pulp fibroblasts from the same individual (in vitro). The results of this study showed four main types of GAG in normal human dental pulp tissue, which were dermatan sulfate, heparan sulfate, hyaluronic acid, and chondroitin sulfate. GAG synthesis from cultured pulp fibroblasts in vitro was different from the GAG present in the dental pulp (in vivo). Extracellular GAG, as well as pericellular GAG consisted of dermatan sulfate, hyaluronic acid, chondroitin sulfate, and heparin. Cellular GAG, however, contained only dermatan sulfate, hyaluronic acid, and chondroitin sulfate. There was no difference in type of GAG from the second and fourth passaged pulp fibroblasts.

Regulation of glycosaminoglycan synthesis by parathyroid hormone and prostaglandin E2 in cultured dental pulp cells

The effects of parathyroid hormone (PTH) and prostaglandin E2 (PGE2) on glycosaminoglycan (GAG) synthesis in bovine dental pulp cells were studied. Dibutyryl cyclic adenosine 3',5'-monophosphate and isobutyl methylxanthine were used to assess whether their effects were mediated by intracellular cAMP. Glycosaminoglycan synthesis was assayed by measuring [35S]sulfate incorporation into the GAG fraction of dental pulp cells. Glycosaminoglycan synthesis was increased 1.3-fold by PTH (4 units per ml) alone, 1.6-fold by PTH in the presence of isobutyl methylxanthine, 1.2-fold by PGE2 (100 ng per ml) alone, and 1.5-fold by PGE2 in the presence of isobutyl methylxanthine. Dibutyryl cyclic adenosine 3',5'-monophosphate enhanced GAG synthesis in a concentration-dependent manner and mimicked the effects of PTH and PGE2. The effects of these hormones on pulp and gingival cells were compared; addition of PTH, PGE2, and dibutyryl cAMP had no effect on gingival cell GAG synthesis, whereas their addition induced significant increases of GAG in pulp cells. These results indicate that PTH and PGE2 are involved in the differentiation of dental pulp cells and that these effects are mediated by cAMP.

Effects of insulin and parathyroid hormone on DNA synthesis and ornithine decarboxylase activity in cultured bovine dental pulp

The effects of insulin and parathyroid hormone (PTH) on the proliferation of developing bovine dental pulp in an explant culture system were studied. Dental pulp explants were cultured on siliconized lens paper floating on the serum-free medium for up to 72 h. Ornithine decarboxylase (ODC) activity increased and reached a peak after 24 h. DNA synthesis increased continuously after a lag period of 24 h. Insulin (10 milliunits per ml) stimulated ODC activity 1.3-fold and DNA synthesis 1.5-fold. PTH alone (1 unit per ml) stimulated ODC activity in 1.7-fold, but did not affect DNA synthesis. PTH plus insulin caused greater increases in ODC activity and DNA synthesis in dental pulp explants than insulin alone (ODC, 2.6-fold; DNA, 3.7-fold). These results suggest that insulin and PTH are involved in the regulation of growth of dentinogenically active bovine dental pulp.

Odontoblast differentiation and the formation of the odontoblast layer

Origin, cell kinetics, and phenotypic aspects of odontoblast cell lineage are described. Epithelial-mesenchymal interactions regulate odontoblast differentiation. These interactions appear to be mediated by the extracellular matrix. Possible molecular mechanisms of cell-matrix interactions are discussed. Questions still unanswered are recommended for investigation.

The extracellular matrix of the dental pulp and dentin

The dental pulp is a loose connective tissue, characterized by its specific anatomical location. Its extracellular components are obvious subjects for study, since such components are largely responsible for the physiological properties of the tissue. Several clinically important processes occur extracellularly, e.g., defense mechanisms such as inflammatory reactions and formation of calcified tissue. The dental mesenchyme has a crucial role during early tooth morphogenesis. The dental pulp, or rather the dental papilla, seems to have only an indirect role during dentinogenesis. This review discusses proteoglycans and glycosaminoglycans, fibronectin and other non-collagenous proteins, and the different types of collagen that have been studied in pulp connective tissue. With regard to its biochemical constituents, the pulp is similar to other loose connective tissues. Collagen type I is the major fibrous component, but collagen type III also constitutes a large portion. Fibronectin is present, as is a high content of proteoglycan. In the proteoglycans, all normally occurring connective tissue glycosaminoglycans can be demonstrated. The composition of the pulpal extracellular matrix during tooth development is quite different from that of the mature tooth. Thus, it is important not to draw any too-far-reaching conclusions about the situation in human pulp from results obtained by studying pulp from animal teeth with ongoing dentinogenesis. In spite of their common ancestry, pulp and dentin differ considerably in extracellular matrix composition. Proteoglycans and collagen type I are present in dentin. No type III collagen or fibronectin can be found in the dentin, although it is present in the dental pulp.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of vitamin A deficiency on rat incisor formation

Vitamin A deficiency (A-) is known to cause morphologic changes in tooth structures. However, its effects on glycosaminoglycan (GAG) distribution in dental pulp, and the role of retinoic acid (RA) in altering these effects are not clearly defined. Tissue changes induced by vitamin A deficiency and RA administration were evaluated histologically in incisors of rats fed on one of 3 different diets: a) vitamin A sufficient (A+); b) vitamin A deficient (A-); and c) vitamin A deficient supplemented with retinoic acid (A-/RA). Four weeks after the onset of vitamin A deficiency, all rats were killed and their 4 continuously erupting incisors evaluated histologically. A- rats had altered dentine and pulp with disrupted histodifferentiation of pulpal mesenchymal cells to normal odontoblasts. The frequency of these abnormalities in dentine and pulp was lower in A-/RA rats. The enamel organ was unremarkable in the 4-week deficient period. Using special stains, we noted that pulpal GAG accumulation in A- and A-/RA rats was limited to the lingual area, while in A+ rats, GAG were distributed throughout. These data suggest that vitamin A deficiency affects histodifferentiation of pulpal mesenchymal cells to odontoblasts, as well as GAG distribution in pulp. RA administration reduces the A- changes and therefore, appears to have some activity in dentinogenesis.

Vascular reactions in the dental pulp during inflammation

This article deals with blood flow and tissue pressure changes in the inflamed dental pulp. While detailed patho-physiological studies of the circulation in the inflamed pulp are still partly lacking, available data from studies of the normal pulp tissue are also discussed. Knowledge of the normal physiological adjustments may indicate which circulatory changes would take place during inflammation. One of the focal points in the present article is how a localized increased tissue pressure may persist in the inflamed area without a circumferential spread to the rest of the pulp. The article is organized in the following manner: First a short review is given of the vascular changes during inflammation in general. Then available data from morphological and functional studies of the pulpal circulation are treated in some detail. Particular attention is given to the transcapillary fluid flow and the so-called 'self-strangulation theory'. The effect of a localized increased tissue pressure on pulpal blood flow is thereafter discussed.

Chromatography on DEAE-cellulose microcolumns: a quantitative method for the fractionation of small quantities of glycosaminoglycans

A simple, sensitive, and efficient method is described for qualitative and quantitative determination of glycosaminoglycans (GAG) synthesized by embryonic mouse teeth. After release from proteoglycan aggregates by enzymatic treatment, a mixture of different GAG was absorbed on a DEAE-cellulose microcolumn (Whatman DE-52 microgranular) at low salt concentration. The different types of GAG were eluted by stepwise increases in the concentration of NaCl. Glycopeptides, which generally contaminate the extract, can be completely removed prior to the elution of GAG. The eluate fractions were analyzed by rechromatography on the same column, using gradient elution. The stepwise elution is suitable for analysis as well as preparation of labeled GAG, the supply of which is limited in amount. The scale of chromatography can easily be stepped up. Quantitative analysis of GAG from embryonic mouse teeth is presented to demonstrate the usefulness of this method.

The concentration, extractability and characterization of collagen in human dental pulp

Premolar and third molar dental pulps were studied. The amount of collagen in the dried pulps was 25.7 per cent in premolars and 31.9 per cent in third molars. These percentages are much higher than those reported for pulps in other species. Significant differences were further found in the collagen content and cell distribution (DNA) of the coronal, middle and apical parts of the pulp. Collagen content was the lowest in the coronal part, while the cell content was the lowest in the middle part. The extractability of collagen in a neutral salt solution or 0.5 M acetic acid was found to be extremely low (less than 1 per cent). Pretreatment of the pulp with hyaluronidase in order to remove proteoglycans had no effect on the solubility. It is concluded that human pulp collagen is highly cross-linked and cannot be considered as immature. Characterization of collagen was performed by methods in which limited pepsin digestion or CNBr cleavage was used. The digests were analysed by means of quantitative electrophoresis which revealed an amount of 42.6 per cent type III of the total collagen. Because of the large differences between dental pulps from man and experimental animals, extreme caution should be exercised in drawing conclusions from data of other species to explain phenomena observed in human teeth.

Glycosaminoglycans in embryonic mouse teeth and the dissociated dental constituents

The nature, amounts and distribution of glycosaminoglycans (GAG) before and during odontoblast terminal differentiation were studied. GAG have been isolated from intact mouse tooth germs and from dissociated dental epithelia and dental papillae after labeling with [3H]glucosamine or 35SO2-(4) asd precursor. The kinds and relative amounts of 3H-labeled GAG were analyzed by chromatography on a DEAE-cellulose column and cellulose thin-layer sheets. The amounts of individual GAG relative to total GAG were determined from the elution profiles, whereas their nature was identified by the selective removal of chromatographic peaks after enzymatic or chemical degradation. We found hyaluronate and probably a minute quantity of heparan sulfate in the dental epithelium, while hyaluronate, heparan sulfate, and chondroitin sulfate were the main types of GAG in the dental papilla. The chondroitin sulfate recovered was further fractionated by cellulose thin-layer chromatography into two isomers, namely chondroitin-2-sulfate (the major component) and chondroitin-6-sulfate. Changes in the elution profile from DEAE-cellulose chromatography of tooth GAG extracted from different developmental stages suggest that modifications of GAG occur during odontogenesis. Alcian blue staining localized large amounts of hyaluronate and sulfated GAG along the epithelio-mesenchymal junction. Tissue specificity and changing patterns of GAG were demonstrated during odontogenesis.

Dental pulp mucopolysaccharidase: identification and role in tooth resorption

The presence of mucopolysaccharidase activity within the pulps of resorbing deciduous teeth was investigated using histochemical techniques. The loss of toluidine blue metachromasia within glycosaminoglycan film subtrates indicated the presence of enzyme activity. This was related to physiologic resorption.

Possible origin of sulfated glycosaminoglycans in human dental calculus

The sulfated glycosaminoglycans present in human dental calculus have been shown to be dermatan sulfate and chondroitin-4-sulfate. The composition suggests that the glycosaminoglycans present in calculus, particularly subgingival material, could originate as a result of associated periodontal disease since closely similar compounds have previously been identified in normal and inflamed human gingiva.

Qualitative and quantitative analysis of bovine, rabbit and human dental pulp glycosaminoglycans

Bovine, rabbit and human dental pulp glycosaminoglycans were analyzed qualitatively and quantitatively using two-dimensional electrophoresis. The major components of bovine and rabbit dental pulp were chondroitin 4-sulphate and hyaluronic acid, while in the human dental pulp dermatan sulphate and chondroitin 4-sulphate were the major components.