The dentin matrix protein-1 (DMP-1) gene is identified in odontoblasts during both embryonic and postnatal development. In vitro study suggests that this noncollagen acidic phosphoprotein plays a role in mineralization. However, deletion of the Dmp-1 gene has little effect on tooth development during embryogenesis. To address the role of DMP-1 in tooth during postnatal development, we analyzed changes of dentinogenesis in Dmp-1 null mice from 3 days after birth to 1 year. Here we show that Dmp-1 null mice postnatally develop a profound tooth phenotype characterized by a partial failure of maturation of predentin into dentin, enlarged pulp chambers, increased width of predentin zone with reduced dentin wall, and hypomineralization. The tooth phenotype of these mice is strikingly similar to that in dentin sialophosphoprotein (Dspp) null mice and shares some features of the human disease dentinogenesis imperfecta III. We have also demonstrated that DSPP levels are reduced in Dmp-1 null mice, suggesting that DSPP is probably regulated by DMP-1 during dentinogenesis. Finally, we show the absence or delayed development of the third molar in Dmp-1 null mice, which is probably secondary to defects in Dmp-1 null bone. Taken together, these studies suggest that DMP-1 is essential for later dentinogenesis during postnatal development.Dentin is a mineralized tissue that closely resembles bone in composition and mechanism of formation. The mechanisms for mineralization are largely unclear, although two hypotheses are proposed to explain initiating mineralization: matrix vesicles in mantle dentin and collagen-phosphophoryn complexes in circumpulpal dentin (1). The in vitro studies also suggest that phosphorylated extracellular matrix (ECM) 1 proteins localized within collagen gap zones can bind calcium and phosphate ions in an appropriate conformation to nucleate the formation of apatite crystals (2, 3). One of the noncollagenous proteins that appears to play an important role in dentin ECM formation and mineralization is dentin matrix protein-1 (DMP-1).DMP-1, an acidic phosphorylated extracellular matrix protein (4), is expressed in odontoblasts that secrete matrix proteins to form dentin. Using protein chemistry approaches, some progress has been made in identifying the normally processed forms of DMP-1 in mineralized tissues (5). Although full-length DMP-1 has been cloned and sequenced, the corresponding intact protein has not been isolated from mineralized tissues. However, two proteolytic fragments, a 37-kDa N-terminal fragment and a 57-kDa C-terminal fragment, have been isolated from bone and dentin extracts (5). Recent studies suggest that DMP-1 can be cleaved by bone morphogenetic protein-1/tolloidlike proteinases (6).In vitro studies suggest that overexpression of Dmp-1 induces differentiation of mesenchymal cells to odontoblast-like cells and enhances mineralization (7) and that DMP-1 can bind to Ca 2ϩ and initiate mineral deposition in vitro (8). However, effects of recombinant DMP-1 on in vitro mineralization are ...

The regeneration of bone tissue is regulated by both osteogenic and angiogenic growth factors which are expressed in a coordinated cascade of events. The aim of this study was to create a dual growth factor-release system that allows for time-controlled release to facilitate bone regeneration. We fabricated core−shell SF/PCL/PVA nanofibrous mats using coaxial electrospinning and layer-by-layer (LBL) techniques, where bone morphogenetic protein 2 (BMP2) was incorporated into the core of the nanofibers and connective tissue growth factor (CTGF) was attached onto the surface. Our study confirmed the sustained release of BMP2 and a rapid release of CTGF. Both in vitro and in vivo experiments demonstrated improvements in bone tissue recovery with the dual-drug release system. In vivo studies showed improvement in bone regeneration by 43% compared with single BMP2 release systems. Time-controlled release enabled by the core−shell nanofiber assembly provides a promising strategy to facilitate bone healing.

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Silk fibroin is regarded as a natural fibrous protein with tunable mechanical properties, acceptable biocompatibility, and favorable capability of enhancing attachment, proliferation, and differentiation of chondrocytes. These properties make it suitable for the fabrication of scaffolds and a broad range of silk fibroin-based biomaterials for cartilage regenerative therapy, which can heal functional cartilage without scar tissue. It can be used as a single material for making different kinds of scaffolds or as a composite with other types of biomaterials. Together with some growth factors, silk fibroin scaffolds can form a support for the growth and differentiation of seeding cells, such as chondrogenic lineage cells and mesenchymal stem cells. Recent advancements of silk fibroin in cartilage regeneration are summarized in this review. Furthermore, the manufacturing methods of silk fibroin materials and their applications in the regeneration of cartilage are also discussed.

The treatment of massive bone defects is still a significant challenge for orthopedists. Here we have engineered synthetic porous AuPd alloy nanoparticles (pAuPds) as a hyperthermia agent for in situ bone regeneration through photothermal therapy (PTT). After being swallowed by cells, pAuPds produced a mild localized heat (MLH) (40−43 °C) under the irradiation of a nearinfrared laser, which can greatly accelerate cell proliferation and bone regeneration. Almost 97% of the cranial defect area (8 mm in diameter) was covered by the newly formed bone after 6 weeks of PTT. RNA sequencing analysis was used to obtain insight into the molecular mechanism of the MLH on cell proliferation and bone formation. These results demonstrated that the Wnt signaling pathway was involved in the MLH. This Letter provides a unique strategy with mild heat stimulation and high efficiency for in situ bone regeneration.

The occurrence of dental trauma is significantly related to the pattern and position of the maxillofacial fractures.

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As the mandible is susceptible to fracture, the aim of this study was to use multivariate logistic regression analysis to identify and distinguish various internal factors that may influence the location of mandibular fractures. The study included 1131 patients with maxillofacial fractures during the period from January 2000 to December 2009 to evaluate the association of mandibular fracture location (unilateral symphysis, body, angle, condylar, or bilateral condylar fractures) with various internal factors. Among the 1131 patients, 869 had mandibular fractures. Data on age, sex, soft tissue injuries, dental trauma, and maxillofacial fracture type were collected and analyzed using multivariate logistic regression. In total, 387, 210, 139, 319, and 172 patients were diagnosed with unilateral symphysis, body, angle, unilateral, or bilateral condylar fractures, respectively. The dental trauma in patients with bilateral condylar fractures differed from that in patients with unilateral condylar fractures. Patients with mandibular fracture (unilateral symphysis, body, unilateral or bilateral condylar) possessed an approximately equal risk of soft tissue injuries in the mandible. Patients with either unilateral or bilateral condylar fractures were associated with a low risk of mandibular angle fracture (OR < 1). Similarly, patients with mandibular angle fracture were associated with a low risk of unilateral or bilateral condylar fractures (OR < 1). Moreover, patients with symphysis fracture were associated with a low risk of bilateral condylar fractures (90 of 387 [23.3%], OR 0.899). By contrast, patients with bilateral condylar fractures were associated with a high risk of symphysis fracture (90 of 172 [52.3%], OR 17.38). Patients with condylar fractures, particularly those with bilateral condylar fractures, were infrequently associated with secondary mandibular fractures. Mandibular fractures tended to have less of an association with midfacial fractures. The occurrence of mandibular fractures is strongly correlated with age, sex, soft tissue injuries, dental trauma, and the pattern and position of the maxillofacial fractures in patients.