The effect of stromelysin-1 (MMP-3) on non-collagenous extracellular matrix proteins of demineralized dentin and the adhesive properties of restorative resins.

Dentin non-collagenous matrix components (NCPs) are structural proteins involved in the formation, the architecture and the mineralization of the extracellular matrix (ECM). We investigated here how recombinant metalloproteinase stromelysin-1, also termed MMP-3, initiates the release of ECM molecules from artificially demineralized human dentin. Analysis of the supernatants by Western blotting reveals that MMP-3 extracts PGs (decorin, biglycan), and also a series of phosphorylated proteins: dentin sialoprotein (DSP), osteopontin (OPN), bone sialoprotein (BSP) and MEPE, but neither dentin matrix protein-1 (DMP1), another member of the SIBLING family, nor osteocalcin (OC), a non-phosphorylated matrix molecule. After treatment of dentin surfaces by MMP-3, scanning electron microscope (SEM) examination of resin replica shows an increased penetration of the resin into the dentin tubules when compared to surfaces only treated by demineralizing solutions. This preclinical investigation suggests that MMP-3 may be used to improve the adhesive properties of restorative materials.

Matricellular molecules and odontoblast progenitors as tools for dentin repair and regeneration.

This review summarizes the in vivo experiments carried out by our group after implantation of bioactive molecules (matricellular molecules) into the exposed pulp of the first maxillary molar of the rat or the mandibular incisor of rats and mice. We describe the cascade of recruitment, proliferation and terminal differentiation of cells involved in the formation of reparative dentin. Cloned immortalized odontoblast progenitors were also implanted in the incisors and in vitro studies aimed at revealing the signaling pathways leading from undifferentiated progenitors to fully differentiated polarized cells. Together, these experimental approaches pave the way for controlled dentin regenerative processes and repair.

Dentin structure in familial hypophosphatemic rickets: benefits of vitamin D and phosphate treatment.

OBJECTIVE: To evaluate the outcome of 1-(OH) vitamin D and oral phosphate treatment on dentin structure in patients with familial hypophosphatemic rickets, and expression of SIBLINGs (a family of non-collagenous proteins involved in dentinogenesis) and osteocalcin. PATIENTS AND METHODS: Seven patients with familial hypophosphatemic rickets (age 3-16 years) were studied before or during treatment. Deciduous and permanent teeth were prepared for scanning electron microscopy (SEM) analysis and immunohistochemistry. RESULTS: Untreated or inadequately treated patients had necrotic teeth with impaired dentin mineralization including unmerged calcospherites and accumulation of non-collagenous proteins in wide interglobular spaces. Most of the primary incisors analyzed displayed fissures linking enamel subsurface to pulp horn. These elements may explain the bacterial penetration and dental abscesses despite the absence of carious lesions. Well-treated patients had healthy teeth with good dentin mineralization and little evidence of calcospherites. CONCLUSION: Treatment of hypophosphatemic children with 1-(OH) vitamin D and oral phosphate insures good dentin development and mineralization, and prevents clinical anomalies such as the dental necrosis classically associated with the disease. Starting treatment during early childhood and good adherence to the therapy are mandatory to observe these beneficial effects.

Dentonin, a MEPE fragment, initiates pulp-healing response to injury.

Phosphorylated extracellular matrix proteins, including matrix extracellular phosphoprotein (MEPE), are involved in the formation and mineralization of dental tissues. In this study, we evaluated the potential of Dentonin, a synthetic peptide derived from MEPE, to promote the formation of reparative dentin. Agarose beads, either soaked with Dentonin or unloaded, were implanted into the pulps of rat molars, and examined 8, 15, and 30 days after treatment. At day 8, Dentonin promoted the proliferation of pulp cells, as visualized by PCNA-labeling. RP59-positive osteoblast progenitors were located around the Dentonin-soaked beads. PCNA- and RP59-labeling were decreased at day 15, while osteopontin, weakly labeled at day 8, was increased at 15 days, but dentin sialoprotein was undetectable at any time. At 8 days, precocious reparative dentin formation occurred in pulps containing Dentonin-soaked beads, with formation slowing after 15 days. These results suggest that Dentonin affects primarily the initial cascade of events leading to pulp healing.

Dentin alteration of deciduous teeth in human hypophosphatemic rickets.

Familial hypophosphatemic rickets is in most cases transmitted as an X-linked dominant trait and results from mutation of the PHEX gene, predominantly expressed in osteoblast and odontoblast. Patients have been reported to display important dentin defects, and therefore, we explored the dentin structure, composition, and distribution of extracellular matrix (ECM) molecules in hypophosphatemic human deciduous teeth. Compared to age-matched controls, the dentin from hypophosphatemic patients exhibited major differences: presence of large interglobular spaces resulting from the lack of fusion of calcospherites in the circumpulpal dentin; defective mineralization in the interglobular spaces contrasting with normal Ca-P levels in the calcospherites on X-ray microanalysis; abnormal presence of low-molecular weight protein complexes recognized on Western blots by antibodies against matrix extracellular phosphoglycoprotein (MEPE), dentin sialoprotein, osteopontin, and reduced osteocalcin (OC) level; and accumulation in the interglobular spaces of immunolabeling with antibodies against DSP, dentin matrix protein, bone sialoprotein, MEPE and OC, while chondroitin/dermatan sulfate glycosaminoglycans were exclusively located inside calcospherites. Alterations of the post-translational processing or partial degradation of some ECM appear as key factors in the formation of the defective hypophosphatemic dentin.

The role of matrix metalloproteinases (MMPs) in human caries.

The objective of this review is to summarize our understanding of the role of host matrix metalloproteinases (MMPs) in the caries process and to discuss new therapeutic avenues. MMPs hydrolyze components of the extracellular matrix and play a central role in many biological and pathological processes. MMPs have been suggested to play an important role in the destruction of dentin organic matrix following demineralization by bacterial acids and, therefore, in the control or progression of carious decay. Host-derived MMPs can originate both from saliva and from dentin. They may be activated by an acidic pH brought about by lactate release from cariogenic bacteria. Once activated, they are able to digest demineralized dentin matrix after pH neutralization by salivary buffers. Furthermore, the degradation of SIBLINGs (Small Integrin-binding Ligand N-linked Glycoproteins) by the caries process may potentially enhance the release of MMPs and their activation. This review also explores the different available MMP inhibitors, natural or synthetic, and suggests that MMP inhibition by several inhibitors, particularly by natural substances, could provide a potential therapeutic pathway to limit caries progression in dentin.

Clinical evaluation of the Carisolv chemomechanical caries removal technique according to the site/stage concept, a revised caries classification system.

The objective of the present study was to assess the efficiency and benefit of a chemomechanical system for carious dentin removal, Carisolv, in general practice. A revised caries classification, the site/stage concept, was used to describe the clinical situations of all carious lesions treated. The study was performed by 12 investigators, and 120 carious lesions were treated with Carisolv. Sixty percent of the cases were treated without anaesthesia, and we found a significant correlation between chemomechanical treatment without anaesthesia and absence of pain ( P=0.01). In 78.3% of the cases, carious dentin was totally removed with Carisolv, and in 21.7%, the dentin treatment was completed by drilling. In cases performed with Carisolv alone, the time required to remove carious dentin was 11.1+/-9.51 min (mean+/-SD). Treatment time was equivalent for all sites and increased significantly with each successive stage of lesion progression ( P<0.001). In 82.5% of cases, the clinicians were satisfied with Carisolv, and in 99.2%, so were the patients. We conclude that, using clinical examination methods, Carisolv seems to remove carious dentin at all sites and stages of carious lesions but must be made more efficient for use in general practice.

The dentino-enamel junction revisited.

The dentino-enamel junction is not an simple inert interface between two mineralized structures. A less simplistic view suggests that the dentino-enamel junctional complex should also include the inner aprismatic enamel and the mantle dentin. At early stages of enamel formation, fibroblast growth factor (FGF)-2 is stored in and released from the inner aprismatic enamel, possibly under the control of matrix metalloproteinase (MMP)-3. The concentration peak for MMP-2 and -9 observed in the mantle dentin coincided with a very low labeling for TIMP-1 and -2, favoring the cross-talk between mineralizing epithelial and connective structures, and as a consequence the translocation of enamel proteins toward odontoblasts and pulp cells, and vice versa, the translocation of dentin proteins toward secretory ameloblasts and cells of the enamel organ. Finally, in X-linked hypophosphatemic rickets, large interglobular spaces in the circumpulpal dentin were the major defect induced by the gene alteration, whereas the mantle dentin was constantly unaffected. Altogether, these data plead for the recognition of the dentino-enamel junctional complex as a specific entity bearing its own biological characteristics.

Human dermal and gingival fibroblasts in a three-dimensional culture: a comparative study on matrix remodeling.

Free-floating collagen lattice is considered a useful tool for assessing wound healing in vitro. This work compared extracellular matrix remodeling in collagen lattices populated by gingival or dermal fibroblasts. For 21 days we followed gel contraction and changes in cell number of collagen lattices seeded with l.5 x 10(5) fibroblasts of each tissue. We also used indirect immunodetection to study extracellular matrix components, metalloproteinases (MMPs), and their tissues inhibitors (TIMPs). In addition, the presence of MMPs and TIMPs in the culture media was analyzed by zymography and western blotting. No significant difference was found concerning gel contraction and changes in cell number. We observed the early expression of fibrillin I and collagen type III, apparently codistributed and at the end of the gel contraction their disappearance. Concomitantly we demonstrated the expression of MMPs and TIMPs, initially localized in cellular cytoplasm, then spreading in the extracellular compartment, and even found in the culture medium. This remodeling was more rapid and intense with gingival fibroblasts than dermal fibroblasts. In conclusion, gingival fibroblasts seem more efficient at remodeling the connective tissue than dermal fibroblasts and could lead to the better wound healing observed in vivo.