Bone sialoprotein-induced reparative dentinogenesis in the pulp of rat's molar

SrCuSi4 O10 /GelMA Composite Hydrogel-Mediated Vital Pulp Therapy: Integrating Antibacterial Property and Enhanced Pulp Regeneration Activity

Vital pulp therapy (VPT) is considered a conservative treatment for preserving pulp viability in caries-induced dental pulp infections. However, bacterial contamination negatively affects dentine-pulp complex repair. The common capping materials show limited antimicrobial effects against some microorganisms. To improve the VPT efficacy, capping materials with increased antibacterial properties and enhanced odontogenic and angiogenic activities are needed. Herein, a SrCuSi4 O10 /gelatin methacrylate(SC/Gel) composite hydrogel has been proposed for infected dental pulp treatment. SrCuSi4 O10 (SC) is a microscale bioceramic composed of assembled multilayered nanosheets that possesses good near-infrared photothermal conversion ability and multiple bioactivities due to sustained Sr2+ , Cu2+ , and SiO3 2- ion release. It is shown that the SC/Gel composite hydrogel efficiently eliminates Streptococcus mutans and Lactobacillus casei and inhibits biofilm formation under photothermal heating, while the ion extract from SC promotes odontogenesis of rat dental pulp stem cells and angiogenesis of human umbilical vein endothelial cells. The as-designed therapeutic effect of SC/Gel composite hydrogel-mediated VPT has been proven in a rat dental pulp infection model and yielded improved dentine-pulp complex repair compared with the commercially used iRoot® BP Plus. This study suggests that the SC/Gel composite hydrogel is a potential pulp-capping material with improved effects on dentine-pulp complex repair in infected pulp.

3D-printed microgels supplemented with dentin matrix molecules as a novel biomaterial for direct pulp capping

OBJECTIVES

To develop a 3D-printed, microparticulate hydrogel supplemented with dentin matrix molecules (DMM) as a novel regenerative strategy for dental pulp capping.

MATERIALS AND METHODS

Gelatin methacryloyl microgels (7% w/v) mixed with varying concentrations of DMM were printed using a digital light projection 3D printer and lyophilized for 2 days. The release profile of the DMM-loaded microgels was measured using a bicinchoninic acid assay. Next, dental pulp exposure defects were created in maxillary first molars of Wistar rats. The exposures were randomly capped with (1) inert material - negative control, (2) microgels, (3) microgels + DMM 500 µg/ml, (4) microgels + DMM 1000 µg/ml, (5) microgels + platelet-derived growth factor (PDGF 10 ng/ml), or (6) MTA (n = 15/group). After 4 weeks, animals were euthanized, and treated molars were harvested and then processed to evaluate hard tissue deposition, pulp tissue organization, and blood vessel density.

RESULTS

All the specimens from groups treated with microgel + 500 µg/ml, microgel + 1000 µg/ml, microgel + PDGF, and MTA showed the formation of organized pulp tissue, tertiary dentin, newly formed tubular and atubular dentin, and new blood vessel formation. Dentin bridge formation was greater and pulp necrosis was less in the microgel + DMM groups compared to MTA.

CONCLUSIONS

The 3D-printed photocurable microgels doped with DMM exhibited favorable cellular and inflammatory pulp responses, and significantly more tertiary dentin deposition.

CLINICAL RELEVANCE

3D-printed microgel with DMM is a promising biomaterial for dentin and dental pulp regeneration in pulp capping procedures.

Stage-Dependent Regulation of Dental Pulp Stem Cell Odontogenic Differentiation by Transforming Growth Factor-β1

Transforming growth factor-β1 (TGF-β1) is an important multifunctional cytokine with dual effects on stem cell differentiation. However, the role of TGF-β1 on odontogenic differentiation of dental pulp stem cells (DPSCs) remains to be entirely elucidated. In the present study, we initially investigated the effect of TGF-β1 at a range of concentrations (0.1-5 ng/mL) on the proliferation, cell cycle, and apoptosis of DPSCs. Subsequently, to determine the effect of TGF-β1 on odontogenic differentiation, alkaline phosphatase (ALP) activity and Alizarin Red S (ARS) staining assays at different concentrations and time points were performed. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis were used to determine the levels of odonto-/osteo-genic differentiation-related gene and protein expression, respectively. For in vivo studies, newly formed tissue was assessed by Masson's trichrome and von Kossa staining. Data indicated that TGF-β1 inhibited DPSCs proliferation in a concentration-and time-dependent manner (p < 0.05) and induced cell cycle arrest but did not affect apoptosis. ALP activity was enhanced, while ARS reduced gradually with increasing TGF-β1 concentrations, accompanied by increased expression of early marker genes of odonto-/osteo-genic differentiation and decreased expression of late-stage mineralization marker genes (p < 0.05). ALP expression was elevated in the TGF-β1-treatment group until 14 days, and the intensity of ARS staining was attenuated at days 14 and 21 (p < 0.05). Compared with the control group, abundant collagen but no mineralized tissues were observed in the TGF-β1-treatment group in vivo. Overall, these findings indicate that TGF-β1 promotes odontogenic differentiation of DPSCs at early-stage while inhibiting later-stage mineralization processes.

Osteopontin on the Dental Implant Surface Promotes Direct Osteogenesis in Osseointegration

After dental implantation, osteopontin (OPN) is deposited on the hydroxyapatite (HA) blasted implant surface followed by direct osteogenesis, which is significantly disturbed in Opn-knockout (KO) mice. However, whether applying OPN on the implant surface promotes direct osteogenesis remains unclarified. This study analyzed the effects of various OPN modified protein/peptides coatings on the healing patterns of the bone-implant interface after immediately placed implantation in the maxilla of four-week-old Opn-KO and wild-type (WT) mice (n = 96). The decalcified samples were processed for immunohistochemistry for OPN and Ki67 and tartrate-resistant acid phosphatase histochemistry. In the WT mice, the proliferative activity in the HA binding peptide-OPN mimic peptide fusion coated group was significantly higher than that in the control group from day 3 to week 1, and the rates of OPN deposition and direct osteogenesis around the implant surface significantly increased in the recombinant-mouse-OPN (rOPN) group compared to the Gly-Arg-Gly-Asp-Ser peptide group in week 2. The rOPN group achieved the same rates of direct osteogenesis and osseointegration as those in the control group in a half period (week 2). None of the implant surfaces could rescue the direct osteogenesis in the healing process in the Opn-KO mice. These results suggest that the rOPN coated implant enhances direct osteogenesis during osseointegration following implantation.

Facilitating Reparative Dentin Formation Using Apigenin Local Delivery in the Exposed Pulp Cavity

Apigenin, a natural product belonging to the flavone class, affects various cell physiologies, such as cell signaling, inflammation, proliferation, migration, and protease production. In this study, apigenin was applied to mouse molar pulp after mechanically pulpal exposure to examine the detailed function of apigenin in regulating pulpal inflammation and tertiary dentin formation. In vitro cell cultivation using human dental pulp stem cells (hDPSCs) and in vivo mice model experiments were employed to examine the effect of apigenin in the pulp and dentin regeneration. In vitro cultivation of hDPSCs with apigenin treatment upregulated bone morphogenetic protein (BMP)- and osteogenesis-related signaling molecules such as BMP2, BMP4, BMP7, bone sialoprotein (BSP), runt-related transcription factor 2 (RUNX2), and osteocalcin (OCN) after 14 days. After apigenin local delivery in the mice pulpal cavity, histology and cellular physiology, such as the modulation of inflammation and differentiation, were examined using histology and immunostainings. Apigenin-treated specimens showed period-altered immunolocalization patterns of tumor necrosis factor (TNF)-α, myeloperoxidase (MPO), NESTIN, and transforming growth factor (TGF)-β1 at 3 and 5 days. Moreover, the apigenin-treated group showed a facilitated dentin-bridge formation with few irregular tubules after 42 days from pulpal cavity preparation. Micro-CT images confirmed obvious dentin-bridge structures in the apigenin-treated specimens compared with the control. Apigenin facilitated the reparative dentin formation through the modulation of inflammation and the activation of signaling regulations. Therefore, apigenin would be a potential therapeutic agent for regenerating dentin in exposed pulp caused by dental caries and traumatic injury.

The effect of different irrigation solutions and activation techniques on the expression of growth factors from dentine of extracted premolar teeth

AIM

To evaluate in a laboratory study, the effect of different canal irrigant solutions and activation techniques on transforming growth factor (TGF-β1), insulin growth factor-1 (IGF-1), bone morphogenetic protein-7 (BMP-7) and vascular endothelial growth factor-A (VEGF-A) release levels from the dentine of extracted premolar teeth.

METHODOLOGY

Seventy premolar teeth with single root and canal were used. The lengths of the root segments were standardized to 12 mm, and the root canals were prepared up to size 100 with hand files. All surfaces of the teeth were covered with nail polish except the inner root canal surface. The root canals were irrigated with 1.5% NaOCl. Ten teeth were allocated to the control group. The remaining sixty teeth were divided into 2 main groups according to the chelating agent used (17% EDTA, 10% Citric acid; CA) and 3 subgroups (n = 10) according to irrigation activation technique (conventional syringe irrigation (CSI), passive ultrasonic irrigation (PUI) and Er:YAG laser activation). After the activation procedure, the root segments were placed into eppendorf tubes containing 1 mL of phosphate-buffered saline solution and kept at 37℃. TGF-β1, IGF-1, BMP-7 and VEGF-A release levels from dentine were measured using the enzyme-linked immunosorbent assay (ELISA) method at 24 h and at day 7. The volume of root canals was calculated using cone-beam computed tomography. The growth factor levels were calculated in ng/mL except VEGF-A (pg/ml). Normality analysis of the data was evaluated with the Kolmogorov-Smirnov test. Statistical analysis was performed using the Mann-Whitney-U and Wilcoxon tests.

RESULTS

Regardless of the activation type and sampling time, EDTA caused significantly more IGF release than did CA, whereas EDTA and CA were equally effective for the release of the other growth factors. For either EDTA or CA, the lowest and highest growth factor release levels were observed in the CSI and Er:YAG laser groups, respectively (p < .05). All of the growth factors were released significantly more at 24 h than on day 7 (p < .05).

CONCLUSIONS

Irrigation activation techniques with EDTA or CA increased the release levels of all growth factors from the dentine of canal walls in extracted premolar teeth.

Pulpal Response to the Combined Use of Mineral Trioxide Aggregate and Iloprost for Direct Pulp Capping

Purpose: The present study aims to assess the combined effects of mineral trioxide aggregate (MTA) and iloprost when used as a pulp capping material on pulpal inflammation and tertiary dentin formation compared with MTA and iloprost alone in rat molar teeth. Methods: Eighty maxillary first molar rat teeth were exposed and capped with iloprost solution, MTA, or MTA mixed with iloprost (MTA-iloprost). The cavities were then filled with resin-modified glass ionomer. The cavity was restored with glass ionomer without the use of pulp capping agent in the control group. The rats were sacrificed after one and four weeks. Block sections of the molar specimens were prepared and subjected to hematoxylin and eosin staining for evaluation. Statistical analysis was done using the Kruskal–Wallis test, followed by Dunnett’s test. Results: At week one, the control group showed significantly more severe pulpal inflammatory reactions than the iloprost (p = 0.00), MTA (p = 0.04), and MTA-iloprost (p = 0.00) groups. Hard tissue formation was commonly found in the iloprost, MTA, and MTA-iloprost groups. After four weeks, pulpal tissue degeneration was observed in the control group. Complete hard tissue barriers were found in 50%, 72.7%, and 77.8% of the specimens in iloprost, MTA, and MTA-iloprost groups, respectively, with no significant differences among the experimental groups. The dentinal tubule patterns were mostly regular in the MTA-iloprost group and irregular in the iloprost and MTA groups. Conclusions: The application of iloprost, MTA, and MTA-iloprost as a pulp capping material resulted in similar pulpal responses in the mechanically exposed pulp of rat molars. Therefore, mixing MTA with iloprost might not be clinically significant.

Comparative evaluation of pulpal repair after direct pulp capping using stem cell therapy and biodentine: An animal study

The response of the dentin-pulp complex in rat teeth was investigated after direct capping with biodentine with or without bone marrow-derived stem cells (BMDSCs). Following mechanical exposure, pulps were randomly capped with one of the followings materials: calcium hydroxide, biodentine or 1 × 10⁵ BMDSCs mL^-1 + biodentine. Histological examination was performed by light microscopy after 1, 3 and 5 weeks. Inflammatory reaction, necrotic tissue formation and calcific bridge formation were scored. Analysis showed that compared with the effects of calcium hydroxide or biodentine, BMDSCs + biodentine substantially reduced inflammatory reaction and necrotic tissue while promoting calcified tissue formation. Therefore, the combination of biodentine and BMDSCs could potentially stimulate pulp tissue regeneration after direct pulp capping.

Expression of BSP-GFPtpz Transgene during Osteogenesis and Reparative Dentinogenesis

Bone sialoprotein (BSP) is a member of the SIBLING family with essential roles in skeletogenesis. In the developing teeth, although the expression and function of BSP in the formation of acellular cementum and periodontal attachment are well documented, there are uncertainties regarding the expression and function of BSP by odontoblasts and dentin. Reporter mice are valuable animal models for biological research, providing a gene expression readout that can contribute to cellular characterization within the context of a developmental process. In the present study, we examined the expression of a BSP-GFPtpz reporter mouse line during odontoblast differentiation, reparative dentinogenesis, and bone. In the developing teeth, BSP-GFPtpz was expressed at high levels in cementoblasts but not in odontoblasts or dentin. In bones, the transgene was highly expressed in osteoblasts at an early stage of differentiation. Interestingly, despite its lack of expression in odontoblasts and dental pulp during tooth development, the BSP-GFPtpz transgene was detected during in vitro mineralization of primary pulp cultures and during reparative dentinogenesis following pulp exposures. Importantly, under these experimental contexts, the expression of BSP-GFPtpz was still exclusive to DSPP-Cerulean, an odontoblast-specific reporter gene. This suggests that the combinatorial use of BSP-GFPtpz and DSPP-Cerulean can be a valuable experimental tool to distinguish osteogenic from dentinogenic cells, thereby providing an avenue to investigate mechanisms that distinctly regulate the lineage progression of progenitors into odontoblasts versus osteoblasts.

Reparative Dentin Formation Using Stem Cell Therapy versus Calcium Hydroxide in Direct Pulp Capping: An Animal Study

Direct pulp capping process is a therapeutic method aimed at maintenance of pulp vitality and health by using a biocompatible material placed directly over the exposed pulp. The aim of this study was to evaluate and compare the effect of direct pulp capping procedures by dental pulp stem cells (DPSCs) or calcium hydroxide on dentin tissue formation. Three mongrel dogs were used as experimental model. Two access cavities were prepared in the right and left mandibular fourth premolars in all dogs to expose and extirpate the pulp tissues which were processed in the lab to obtain a single-cell suspensions. The isolated cells were cultures in odontogenic medium for subsequent differentiation. The maxillary teeth (3 incisors and one canine) of the corresponding dog number were subjected to class V cavities to expose their pulps which were assigned into 2 groups of 12 teeth each ( group I - pulp capping with calcium hydroxide) and (group II - pulp capping with dental stem cells DPSCs). The operated teeth were collected after 3 months and processed for histological and electron microscopic examinations. Specimens were subjected to elemental analysis of calcium and phosphorus. EDX elemental analysis revealed significant differences in the calcium and phosphorous wt, % in the reparative dentin of calcium hydroxide treated group which confirmed histologically. Direct pulp capping by DPSCs has shown promising generative potential for regaining normal dentin.

Evaluation of dentinogenesis inducer biomaterials: an in vivo study

When exposure of the pulp to external environment occurs, reparative dentinogenesis can be induced by direct pulp capping to maintain pulp tissue vitality and function. These clinical situations require the use of materials that induce dentin repair and, subsequently, formation of a mineralized tissue. Objective: This work aims to assess the effect of tricalcium silicate cements and mineral trioxide aggregate cements, including repairing dentin formation and inflammatory reactions over time after pulp exposure in Wistar rats. Methodology: These two biomaterials were compared with positive control groups (open cavity with pulp tissue exposure) and negative control groups (no intervention). The evaluations were performed in three stages; three, seven and twenty-one days, and consisted of an imaging (nuclear medicine) and histological evaluation (H&E staining, immunohistochemistry and Alizarin Red S). Results: The therapeutic effect of these biomaterials was confirmed. Nuclear medicine evaluation demonstrated that the uptake of ^99mTc-Hydroxymethylene diphosphonate (HMDP) showed no significant differences between the different experimental groups and the control, revealing the non-occurrence of differences in the phosphocalcium metabolism. The histological study demonstrated that in mineral trioxide aggregate therapies, the presence of moderate inflammatory infiltration was found after three days, decreasing during follow-ups. The formation of mineralized tissue was only verified at 21 days of follow-up. The tricalcium silicate therapies demonstrated the presence of a slight inflammatory infiltration on the third day, increasing throughout the follow-up. The formation of mineralized tissue was observed in the seventh follow-up day, increasing over time. Conclusions: The mineral trioxide aggregate (WhiteProRoot^®MTA) and tricalcium silicate (Biodentine™) present slight and reversible inflammatory signs in the pulp tissue, with the formation of mineralized tissue. However, the exacerbated induction of mineralized tissue formation with the tricalcium silicate biomaterial may lead to the formation of pulp calcifications

Effects of sclerostin on lipopolysaccharide-induced inflammatory phenotype in human odontoblasts and dental pulp cells

Previously we have demonstrated that sclerostin inhibits stress-induced odontogenic differentiation of odontoblasts and accelerates senescence of dental pulp cells (DPCs) Odontoblasts and DPCs are main functioning cells for inflammation resistance and tissue regeneration in dentine-pulp complex. Sclerostin is relevant for systemic inflammation and chronic periodontitis processes, but its effects on dental pulp inflammation remains unclear. In this study, we found that sclerostin expression of odontoblasts was elevated in lipopolysaccharide-induced inflammatory environment, and exogenous sclerostin increased the production of pro-inflammatory cytokines in inflamed odontoblasts. Furthermore, sclerostin activated the NF-κB signaling pathway in inflamed odontoblasts and the NF-κB inhibitor reversed the exaggerative effects of sclerostin on the pro-inflammatory cytokines production. Additionally, sclerostin promoted adhesion and migration of inflamed DPCs, while inhibiting odontoblastic differentiation of inflamed DPCs. Sclerostin also might enhance pulpal angiogenesis. Taken together, it can therefore be inferred that sclerostin is upregulated in inflamed odontoblasts under pulpal inflammatory condition to enhance inflammatory responses in dentine-pulp complex and impair reparative dentinogenesis. This indicates that sclerostin inhibition might be a therapeutic target for anti-inflammation and pro-regeneration during dental pulp inflammation.

Characterization of Odontoblast-like Cell Phenotype and Reparative Dentin Formation In Vivo: A Comprehensive Literature Review

INTRODUCTION

The primary aim was to explore the criteria used in characterization of reparative cells and mineralized matrices formed after treatment of pulp exposures, and the sequence of relative events. The secondary aim was to evaluate whether the reparative events depend on the experimental model species, age, and therapeutic intervention.

METHODS

A literature search of databases using different combinations of the key words was undertaken. Data analysis was based only on studies having histological or histochemical assessment of the pulp tissue responses. The search yielded 86 studies, 47 capping material-based and 39 bioactive application-based experiments, which provided data on morphological or functional characterization of the mineralized matrices and the associated cells.

RESULTS

In 64% of capping material-based and 72% of bioactive application-based experiments, a 2-zone mineralized matrix formation (atubular followed by tubular) was detected, whereas characterization of odontoblastic differentiation is provided in only 25.5% and 46.1% of the studies, respectively. In 93.3% of the studies showing odontoblast-like cells, differentiated cells were in association with tubular mineralized matrix formation. Analyses further showed that cell- and matrix-related outcomes do not depend on experimental model species, age, and therapeutic intervention.

CONCLUSIONS

The evidence of the reviewed scientific literature is that dental pulp cells secrete a dentin-like matrix of tubular morphology in relation to primitive forms of atubular or osteotypic mineralized matrix. Furthermore, data analysis showed that dental pulp cells express in vivo the odontoblastic phenotype, and secrete matrix in a predentin-like pattern, regardless of the model species, age, and therapeutic intervention used.

Effects of the exposure site on histological pulpal responses after direct capping with 2 calcium-silicate based cements in a rat model

Objectives

Direct pulp capping is a treatment for mechanically exposed pulp in which a biocompatible capping material is used to preserve pulpal vitality. Biocompatibility tests in animal studies have used a variety of experimental protocols, particularly with regard to the exposure site. In this study, pulp exposure on the occlusal and mesial surfaces of molar teeth was investigated in a rat model.

Materials and Methods

A total of 58 maxillary first molars of Wistar rats were used. Forty molars were mechanically exposed and randomly assigned according to 3 factors: 1) the exposure site (occlusal or mesial), 2) the pulp-capping material (ProRoot White MTA or Bio-MA), and 3) 2 follow-up periods (1 day or 7 days) (n = 5 each). The pulp of 6 intact molars served as negative controls. The pulp of 12 molars was exposed without a capping material (n = 3 per exposure site for each period) and served as positive controls. Inflammatory cell infiltration and reparative dentin formation were histologically evaluated at 1 and 7 days using grading scores.

Results

At 1 day, localized mild inflammation was detected in most teeth in all experimental groups. At 7 days, continuous/discontinuous calcified bridges were formed at exposure sites with no or few inflammatory cells. No significant differences in pulpal response according to the exposure site or calcium-silicate cement were observed.

Conclusions

The location of the exposure site had no effect on rat pulpal healing. However, mesial exposures could be performed easily, with more consistent results. The pulpal responses were not significantly different between the 2 capping materials.

Dentinogenic effects of extracted dentin matrix components digested with matrix metalloproteinases

Dentin is primarily composed of hydroxyapatite crystals within a rich organic matrix. The organic matrix comprises collagenous structural components, within which a variety of bioactive molecules are sequestered. During caries progression, dentin is degraded by acids and enzymes derived from various sources, which can release bioactive molecules with potential reparative activity towards the dentin-pulp complex. While these molecules’ repair activities in other tissues are already known, their biological effects are unclear in relation to degradation events during disease in the dentin-pulp complex. This study was undertaken to investigate the effects of dentin matrix components (DMCs) that are partially digested by matrix metalloproteinases (MMPs) in vitro and in vivo during wound healing of the dentin-pulp complex. DMCs were initially isolated from healthy dentin and treated with recombinant MMPs. Subsequently, their effects on the behaviour of primary pulp cells were investigated in vitro and in vivo. Digested DMCs modulated a range of pulp cell functions in vitro. In addition, DMCs partially digested with MMP-20 stimulated tertiary dentin formation in vivo, which exhibited a more regular tubular structure than that induced by treatment with other MMPs. Our results indicate that MMP-20 may be especially effective in stimulating wound healing of the dentin-pulp complex.

Current status of direct pulp-capping materials for permanent teeth

Direct pulp-capping is a method for treating exposed vital pulp with dental material to facilitate the formation of reparative dentin and to maintain vital pulp. Two types of pulp-capping materials, calcium hydroxide and mineral trioxide aggregate, have been most commonly used in clinics, and an adhesive resin has been considered a promising capping material. However, until now, there has been no comprehensive review of these materials. Therefore, in this paper, the composition, working mechanisms and clinical outcome of these types of pulp-capping materials are reviewed.

Effects of phosphatidylserine-containing liposomes on odontogenic differentiation of human dental pulp cells

Phosphatidylserine (PS) is known to enhance biomineralization due to the ability to accumulate calcium ions. In this study, the effects of PS on odontogenic differentiation and mineralization of human dental pulp cells (HDPCs) were investigated using phosphatidylserine-containing liposomes (PSLs). PSL was slightly cytotoxic at 125 µM in growth medium, and ALP activity was up-regulated in the PSL-treated HDPCs at non-cytotoxic concentrations. Mineralization was also enhanced by PSL, while mRNA expressions of DSPP and OCN genes were slightly attenuated. The mRNA expression of Runx2 was not altered by PSL. It is thus likely that PSL selectively affected odontogenic differentiation processes of HDPC. Finally, the interaction between PSL and HDPC was investigated by staining with annexin V-FITC in PSL-treated HDPC. It was found that PS was gradually incorporated into HDPC cytoplasm for several days. The results of this study suggest that PSL is able to stimulate dentin formation in dental pulps.

Biological evaluation of a new pulp capping material developed from Portland cement

This study evaluates the biological properties of a new pulp capping material developed from Portland cement. This study was conducted on 48 teeth in 4 dogs (12 teeth/dog). The dogs were classified into two equal groups (n=24 teeth) according to the evaluation period including: group A (3 weeks) and group B (3 months). Each group was further subdivided into three equal subgroups (n=8 teeth) according to the capping material including: subgroup 1: mineral trioxide aggregate (MTA), subgroup2: Portland cement+10% calcium hydroxide+20% bismuth oxide (Port Cal) and subgroup 3: Portland cement+bismuth oxide. After general anesthesia, a class V buccal cavity was prepared coronal to the gingival margin. After pulp exposure and hemostasis,the capping materials and glass ionomer filling were placed on the exposure sites. All histopathological findings, inflammatory cell count and dentin bridge formation were recorded. Data were analyzed statistically. After 3 months, the histopathological picture of the pulp in subgroup 1 showed normal pulp, continuous odontoblastic layer and complete dentin bridge formation while subgroup 2 showed partial and complete dentin bridge over a normal and necrotic pulps. Subgroup 3 showed loss of normal architecture, areas of necrosis, complete, or incomplete dentin bridge formation, attached and detached pulp stones and fatty degeneration in group B. For group A, MTA subgroup showed the least number of inflammatory cell infiltrate followed by Port Cal subgroup. While subgroup 3 showed the highest number of inflammatory cell infiltrate. For group B, the mean inflammatory cell count increased with the three tested materials with no statistical difference. Regarding dentin bridge formation at group A, no significant differences was found between subgroups, while at group B, MTA subgroup exhibited significantly higher scores than other subgroups. In conclusion, addition of calcium hydroxide to Portland cement improves the dentin bridge formation qualitatively and quantitatively.

Pulp stem cells: implication in reparative dentin formation

Many dental pulp stem cells are neural crest derivatives essential for lifelong maintenance of tooth functions and homeostasis as well as tooth repair. These cells may be directly implicated in the healing process or indirectly involved in cell-to-cell diffusion of paracrine messages to resident (pulpoblasts) or nonresident cells (migrating mesenchymal cells). The identity of the pulp progenitors and the mechanisms sustaining their regenerative capacity remain largely unknown. Taking advantage of the A4 cell line, a multipotent stem cell derived from the molar pulp of mouse embryo, we investigated the capacity of these pulp-derived precursors to induce in vivo the formation of a reparative dentin-like structure upon implantation within the pulp of a rodent incisor or a first maxillary molar after surgical exposure. One month after the pulp injury alone, a nonmineralized fibrous matrix filled the mesial part of the coronal pulp chamber. Upon A4 cell implantation, a mineralized osteodentin was formed in the implantation site without affecting the structure and vitality of the residual pulp in the central and distal parts of the pulp chamber. These results show that dental pulp stem cells can induce the formation of reparative dentin and therefore constitute a useful tool for pulp therapies. Finally, reparative dentin was also built up when A4 progenitors were performed by alginate beads, suggesting that alginate is a suitable carrier for cell implantation in teeth.

Functionalized scaffolds to control dental pulp stem cell fate

Emerging understanding about interactions between stem cells, scaffolds, and morphogenic factors has accelerated translational research in the field of dental pulp tissue engineering. Dental pulp stem cells constitute a subpopulation of cells endowed with self-renewal and multipotency. Dental pulp stem cells seeded in biodegradable scaffolds and exposed to dentin-derived morphogenic factors give rise to a pulplike tissue capable of generating new dentin. Notably, dentin-derived proteins are sufficient to induce dental pulp stem cell differentiation into odontoblasts. Ongoing work is focused on developing ways of mobilizing dentin-derived proteins and disinfecting the root canal of necrotic teeth without compromising the morphogenic potential of these signaling molecules. On the other hand, dentin by itself does not appear to be capable of inducing endothelial differentiation of dental pulp stem cells despite the well-known presence of angiogenic factors in dentin. This is particularly relevant in the context of dental pulp tissue engineering in full root canals in which access to blood supply is limited to the apical foramina. To address this challenge, scientists are looking at ways to use the scaffold as a controlled-release device for angiogenic factors. The aim of this article was to present and discuss current strategies to functionalize injectable scaffolds and customize them for dental pulp tissue engineering. The long-term goal of this work is to develop stem cell-based therapies that enable the engineering of functional dental pulps capable of generating new tubular dentin in humans.

Pulp development, repair, and regeneration: challenges of the transition from traditional dentistry to biologically based therapies

The traditional concept of replacing diseased tooth/pulp tissues by inert materials (restoration) is being challenged by recent advances in pulp biology leading to regenerative strategies aiming at the generation of new vital tissue. New tissue formation in the pulp chamber can be observed after adequate infection control and the formation of a blood clot. However, differentiation of true odontoblasts is still more speculative, and the approach is largely limited to immature teeth with open apices. A more systematic approach may be provided by the adoption of the tissue engineering concepts of using matrices, suitable (stem) cells, and signaling molecules to direct tissue events. With these tools, pulplike constructs have already been generated in experimental animals. However, a number of challenges still remain for clinical translation of pulp regeneration (eg, the cell source [resident vs nonresident stem cells, the latter associated with cell-free approaches], mechanisms of odontoblast differentiation, the pulp environment, the role of infection and inflammation, dentin pretreatment to release fossilized signaling molecules from dentin, and the provision of suitable matrices). Transition as a process, defined by moving from one form of "normal" to another, is based not only on the progress of science but also on achieving change to established treatment concepts in daily practice. However, it is clear that the significant recent achievements in pulp biology are providing an exciting platform from which clinical translation of dental pulp regeneration can advance.

Reactionary and reparative dentin formation after pulp capping: Hydrogel vs. Dycal

Background

After indirect capping, injured odontoblasts generate reactionary dentin, whereas after direct capping of a pulp exposure pulp, cells stimulate the formation of reparative dentin. The aim of this study was to evaluate and compare the effects of two direct capping agents on pulp tissue reactions: Hydrogel (a bovine serum albumin (BSA)/glutaraldehyde,) and Dycal (a calcium hydroxide-based capping agent).

Methods

In 6-week-old male Sprague–Dawley rats, occlusal cavities were drilled in the first maxillary molars, and the pulps were exposed. In one of the groups, 24 right molars were capped with Hydrogel (G1), whereas in the other group 24 M were capped with Dycal (G2). After 1 to 4 weeks, the rats were anaesthetized intraperitoneally (six rats per group) and perfused intracardiacally with 4 % paraformaldehyde fixative. Maxillary molar’s blocks were demineralized with a 4.13 % EDTA solution, embedded in paraffin, and the sections were histologically stained. Measurements of the thickness of reactionary dentin and area of inflammation were measured with ImageJ software. Results were compared with Kruskal Wallis and Mann Whitney U tests at p = 0.05.

Results

One week after Dycal capping, a statistically significant large number of aggregates of pulp cells enlightened pulpal inflammation compared to Hydrogel. At 2–3 weeks, reactionary dentin formation was increased at the periphery of the pulp chamber. After 4 weeks, a dentinal bridge sealed partially the pulp exposure, while tunnel defects persisting across reparative osteodentin. In contrast, 1 week after Hydrogel capping, inflammation was barely detectable. Hydrogel induced the massive apposition of reactionary dentin at the pulp periphery, and reparative dentin was developing within the pulp. The degradation of Hydrogel releases glutaraldehyde acting on pulp cells as a fixative and consequently favoring BSA bioactivity.

Conclusion

After Hydrogel capping, nemosis stimulates pulp mineralization, improving reactionary and reparative dentin formation. In contrast, the highly alkaline compound Dycal produced inflammation within the pulp. The differences between the two capping agents suggest that Hydrogel might present some clinical advantages over Dycal.

Perivascular Stem Cells at the Tip of Mouse Incisors Regulate Tissue Regeneration

Cells with in vitro properties similar to those of bone marrow stromal stem cells are present in tooth pulp as quiescent cells that are mobilized by damage. These dental pulp stem cells (DPSCs) respond to damage by stimulating proliferation and differentiation into odontoblast-like cells that form dentine to repair the damage. In continuously growing mouse incisors, tissue at the incisor tips is continuously being damaged by the shearing action between the upper and lower teeth acting to self-sharpen the tips. We investigated mouse incisor tips as a model for the role of DPSCs in a continuous natural repair/regeneration process. We show that the pulp at the incisor tip is composed of a disorganized mass of mineralized tissue produced by odontoblast-like cells. These cells become embedded into the mineralized tissue that is rapidly formed and then lost during feeding. Tetracycline labeling not only revealed the expected incorporation into newly synthesized dentine formation of the incisor but also a zone covering the pulp cavity at the tips of the incisors that is mineralized very rapidly. This tissue was dentine-like but had a significantly lower mineral content than dentine as determined by Raman spectroscopy. The mineral was more crystalline than dentine, indicative of small, defect-free mineral particles. To identify the origin of cells responsible for deposition of this mineralized tissue, we genetically labeled perivascular cells by crossing NG2(ERT2) Cre and Nestin Cre mice with reporter mice. A large number of pericyte-derived cells were visible in the pulp of incisor tips with some having elongated, odontoblast-like shapes. These results show that in mouse incisors, rapid, continuous mineralization occurs at the tip to seal off the pulp tissue from the external environment. The mineral is formed by perivascular-derived cells that differentiate into cells expressing dentin sialo-phosphoprotein (DSPP) and produce a dentine-like material in a process that functions as continuous natural tissue regeneration.

Matricellular proteins in drug delivery: Therapeutic targets, active agents, and therapeutic localization

Extracellular matrix is composed of a complex array of molecules that together provide structural and functional support to cells. These properties are mainly mediated by the activity of collagenous and elastic fibers, proteoglycans, and proteins such as fibronectin and laminin. ECM composition is tissue-specific and could include matricellular proteins whose primary role is to modulate cell-matrix interactions. In adults, matricellular proteins are primarily expressed during injury, inflammation and disease. Particularly, they are closely associated with the progression and prognosis of cardiovascular and fibrotic diseases, and cancer. This review aims to provide an overview of the potential use of matricellular proteins in drug delivery including the generation of therapeutic agents based on the properties and structures of these proteins as well as their utility as biomarkers for specific diseases.

Regenerative endodontics--Creating new horizons

Trauma to the dental pulp, physical or microbiologic, can lead to inflammation of the pulp followed by necrosis. The current treatment modality for such cases is non-surgical root canal treatment. The damaged tissue is extirpated and the root canal system prepared. It is then obturated with an inert material such a gutta percha. In spite of advances in techniques and materials, 10%-15% of the cases may end in failure of treatment. Regenerative endodontics combines principles of endodontics, cell biology, and tissue engineering to provide an ideal treatment for inflamed and necrotic pulp. It utilizes mesenchymal stem cells, growth factors, and organ tissue culture to provide treatment. Potential treatment modalities include induction of blood clot for pulp revascularization, scaffold aided regeneration, and pulp implantation. Although in its infancy, successful treatment of damaged pulp tissue has been performed using principles of regenerative endodontics. This field is dynamic and exciting with the ability to shape the future of endodontics. This article highlights the fundamental concepts, protocol for treatment, and possible avenues for research in regenerative endodontics.

Dentinogenic Specificity in the Preclinical Evaluation of Vital Pulp Treatment Strategies: A Critical Review

Reviews on the clinical performance of vital pulp treatment strategies and capping materials repeatedly showed an insufficient grade of evidence concerning their therapeutic validity. The biological mechanisms underlying the regenerative potential of pulp-dentin complex have attracted much attention during the last two decades, since new pulp treatment modalities have been designed and tested at the preclinical level. It has been recognized that evaluation should be based on the specific ability of therapeutic interventions to signal recruitment and differentiation of odontoblast-like cells forming a matrix in a predentin-like pattern, rather than uncontrolled hard tissue deposition in a scar-like form. The aim of the present article was to critically review data from histological experimental studies on pulp capping, published during the last 7 decades. A comprehensive literature search covering the period from 1949 to 2015 was done using the Medline/Pubmed database. Inclusion of a study was dependent on having sufficient data regarding the type of capping material used and the unit of observation (human permanent tooth in vivo or animal permanent dentition; primary teeth were excluded). The post-operatively deposited matrix was categorized into three types: unspecified, osteotypic, or dentin-like matrix. One hundred fifty-two studies were included in the final evaluation. Data from the present systematic review have shown that only 30.2% of the 152 experimental histological pulp capping studies described the heterogenic nature of the hard tissue bridge formation, including osteotypic and tubular mineralized tissue. Structural characteristics of the new matrix and the associated formative cells were not provided by the remaining 106 studies. Analysis showed that more careful preclinical evaluation with emphasis on the evidence regarding the dentinogenic specificity of pulp therapies is required. It seems that selection of appropriate vital pulp treatment strategies and pulp capping materials would be further facilitated in terms of their therapeutic validity if international consensus could be reached on a select number of mandatory criteria for tissue-specific dentinogenic events.

Active Nanomaterials to Meet the Challenge of Dental Pulp Regeneration

The vitality of the pulp is fundamental to the functional life of the tooth. For this aim, active and living biomaterials are required to avoid the current drastic treatment, which is the removal of all the cellular and molecular content regardless of its regenerative potential. The regeneration of the pulp tissue is the dream of many generations of dental surgeons and will revolutionize clinical practices. Recently, the potential of the regenerative medicine field suggests that it would be possible to achieve such complex regeneration. Indeed, three crucial steps are needed: the control of infection and inflammation and the regeneration of lost pulp tissues. For regenerative medicine, in particular for dental pulp regeneration, the use of nano-structured biomaterials becomes decisive. Nano-designed materials allow the concentration of many different functions in a small volume, the increase in the quality of targeting, as well as the control of cost and delivery of active molecules. Nanomaterials based on extracellular mimetic nanostructure and functionalized with multi-active therapeutics appear essential to reverse infection and inflammation and concomitantly to orchestrate pulp cell colonization and differentiation. This novel generation of nanomaterials seems very promising to meet the challenge of the complex dental pulp regeneration.

Regeneration of dentin–pulp-like tissue using an injectable tissue engineering technique

An injectable tissue engineering technique to regenerate dentin–pulp complex.

Induction of reparative dentin formation on exposed dental pulp by dentin phosphophoryn/collagen composite

The ultimate goal of vital pulp therapy is to regenerate rapidly dentin possessing an excellent quality using a biocompatible, bioactive agent. Dentin phosphophoryn (DPP), the most abundant noncollagenous polyanionic protein in dentin, cross-linked to atelocollagen fibrils was applied to direct pulp capping in rats. After 1, 2, and 3 weeks, the teeth applied were examined on the induction of reparative dentin formation and the response of pulp tissue, compared to calcium hydroxide-based agent conventionally used. The reparative dentin formation induced by DPP/collagen composite was more rapid than by calcium hydroxide. In the morphometrical analysis, the formation rate of reparative dentin by DPP/collagen composite was approximately the same as that by calcium hydroxide at 3 weeks. Nevertheless, the compactness of reparative dentin formed by DPP/collagen composite was much superior to what resulted from calcium hydroxide. Also, DPP/collagen composite showed high covering ability of exposed pulp. Moreover, DPP/collagen composite led only to slight pulp inflammation at the beginning whereas calcium hydroxide formed necrotic layer adjacent to the material and induced severe inflammation in pulp tissue at 1 week. The present study demonstrates a potential for DPP/collagen composite as a rapid biocompatible inducer for the formation of reparative dentin of excellent quality in rats.

Matricellular proteins and biomaterials

Biomaterials are essential to modern medicine as components of reconstructive implants, implantable sensors, and vehicles for localized drug delivery. Advances in biomaterials have led to progression from simply making implants that are nontoxic to making implants that are specifically designed to elicit particular functions within the host. The interaction of implants and the extracellular matrix during the foreign body response is a growing area of concern for the field of biomaterials, because it can lead to implant failure. Expression of matricellular proteins is modulated during the foreign body response and these proteins interact with biomaterials. The design of biomaterials to specifically alter the levels of matricellular proteins surrounding implants provides a new avenue for the design and fabrication of biomimetic biomaterials.

MM-MTA for direct pulp capping: a histologic comparison with ProRoot MTA in rat molars

AIM

To compare the histomorphological response of rat dental pulps capped with MM-MTA and ProRoot MTA at 1, 2 and 4 weeks postoperatively.

MATERIALS AND METHODS

Direct pulp capping with MM-MTA and ProRoot MTA, overlaid with light-cured composite resin, was performed on right and left maxillary first molars of 20 Wistar rats. Animals were killed at 1, 2 and 4 weeks postoperatively. Biopsy samples were stained and viewed by light microscopy to determine dentin bridge formation. Data were statistically evaluated with the Kruskal-Wallis test (p < 0.05).

RESULTS

Absence of dentin bridge formation at 1 week, partial dentin bridge formation at 2 weeks and complete dentin bridge formation at 4 weeks are observed with MM-MTA and ProRoot MTA. The results showed no statistically significant difference between both materials at 4 weeks.

CONCLUSION

Both materials produced similar responses in the pulp when used for pulp capping in intact, caries-free molars of rats.

Advances in regeneration of dental pulp--a literature review

This review summarizes the biological response of dentin-pulp complexes to a variety of stimuli and responses to current treatment therapies and reviews the role of tissue engineering and its application in regenerative endodontics. An electronic search was undertaken based on keywords using Medline/PubMed, Embase, Web of Science and Ovid database resources up to March 2012 to identify appropriate articles, supplemented by a manual search using reference lists from relevant articles. Inclusion criteria were mainly based on different combinations of keywords and restricted to articles published in English language only. Biological approaches based on tissue engineering principles were found to offer the possibility of restoring natural tooth vitality, with distinct evidence that regeneration of lost dental tissues is possible. Studies to formulate an ideal restorative material with regenerative properties, however, are still under way. Further research with supporting clinical studies is required to identify the most effective and safe treatment therapy.

Novel bioactivity of phosvitin in connective tissue and bone organogenesis revealed by live calvarial bone organ culture models

Egg yolk phosvitin is one of the most highly phosphorylated extracellular matrix proteins known in nature with unique physico-chemical properties deemed to be critical during ex-vivo egg embryo development. We have utilized our unique live mouse calvarial bone organ culture models under conditions which dissociates the two bone remodeling stages, viz., resorption by osteoclasts and formation by osteoblasts, to highlight important and to date unknown critical biological functions of egg phosvitin. In our resorption model live bone cultures were grown in the absence of ascorbate and were stimulated by parathyroid hormone (PTH) to undergo rapid osteoclast formation/differentiation with bone resorption. In this resorption model native phosvitin potently inhibited PTH-induced osteoclastic bone resorption with simultaneous new osteoid/bone formation in the absence of ascorbate (vitamin C). These surprising and critical observations were extended using the bone formation model in the absence of ascorbate and in the presence of phosvitin which supported the above results. The results were corroborated by analyses for calcium release or uptake, tartrate-resistant acid phosphatase activity (marker for osteoclasts), alkaline phosphatase activity (marker for osteoblasts), collagen and hydroxyproline composition, and histological and quantitative histomorphometric evaluations. The data revealed that the discovered bioactivity of phosvitin mirrors that of ascorbate during collagen synthesis and the formation of new osteoid/bone. Complementing those studies use of the synthetic collagen peptide analog and cultured calvarial osteoblasts in conjunction with mass spectrometric analysis provided results that augmented the bone organ culture work and confirmed the capacity of phosvitin to stimulate differentiation of osteoblasts, collagen synthesis, hydroxyproline formation, and biomineralization. There are striking implications and interrelationships of this affect that relates to the evolutionary inactivation of the gene of an enzyme L-gulono-γ-lactone oxidase, which is involved in the final step of ascorbate biosynthesis, in many vertebrate species including passeriform birds, reptiles and teleost fish whose egg yolk contain phosvitin. These represent examples of how developing ex-vivo embryos of such species can achieve connective tissue and skeletal system formation in the absence of ascorbate.

Tooth Tissue Engineering: Potential and Pitfalls

All over the world a large number of people suffer from tooth diseases like dental caries, tooth abscess, and plaques. Tooth loss or damage, which occurs frequently in our society are generally repaired by applying several conventional methods, such as root-canal treatment, direct pulp capping and dental implants. These methods are quite painful, create damage to the surrounding tooth tissues and also may at times have adverse side-effects. The limitations of the conventional methods can be overcome by applying the concept of tooth tissue engineering. Tooth tissue engineering is the application of biosciences and engineering to regenerate a biofunctional tooth, which can be used to replace the missing tooth or repair the damaged tooth. Tissue engineering involves three key elements - cell, scaffold and growth factors, which interact with each other to regenerate a specific tissue. The success of tissue engineering depends on the proper selection of these three key elements and understanding the interactions among them. To bring us close to the realization of a tissue-engineered tooth, immense progress is going on in understanding how tooth is first developed, and there is a good advancement in tooth regeneration. In this review, “tooth tissue engineering” will be discussed, along with the recent advancements and challenges in bring a biofunctional tooth from laboratory out into clinical use.

Dental pulp tissue engineering

Dental pulp is a highly specialized mesenchymal tissue that has a limited regeneration capacity due to anatomical arrangement and post-mitotic nature of odontoblastic cells. Entire pulp amputation followed by pulp space disinfection and filling with an artificial material cause loss of a significant amount of dentin leaving as life-lasting sequelae a non-vital and weakened tooth. However, regenerative endodontics is an emerging field of modern tissue engineering that has demonstrated promising results using stem cells associated with scaffolds and responsive molecules. Thereby, this article reviews the most recent endeavors to regenerate pulp tissue based on tissue engineering principles and provides insightful information to readers about the different aspects involved in tissue engineering. Here, we speculate that the search for the ideal combination of cells, scaffolds, and morphogenic factors for dental pulp tissue engineering may be extended over future years and result in significant advances in other areas of dental and craniofacial research. The findings collected in this literature review show that we are now at a stage in which engineering a complex tissue, such as the dental pulp, is no longer an unachievable goal and the next decade will certainly be an exciting time for dental and craniofacial research.

Biological approaches toward dental pulp regeneration by tissue engineering

Root canal therapy has been the predominant approach in endodontic treatment, wherein the entire pulp is cleaned out and replaced with a gutta-percha filling. However, living pulp is critical for the maintenance of tooth homeostasis and essential for tooth longevity. An ideal form of therapy, therefore, might consist of regenerative approaches in which diseased/necrotic pulp tissues are removed and replaced with regenerated pulp tissues to revitalize the teeth. Dental pulp regeneration presents one of the most challenging issues in regenerative dentistry due to the poor intrinsic ability of pulp tissues for self-healing and regrowth. With the advent of modern tissue engineering and the discovery of dental stem cells, biological therapies have paved the way to utilize stem cells, delivered or internally recruited, to generate dental pulp tissues, where growth factors and a series of dentine extracellular matrix molecules are key mediators that regulate the complex cascade of regeneration events to be faithfully fulfilled.

Dental stem cell therapy with calcium hydroxide in dental pulp capping

Calcium hydroxide has been extensively and steadily used for direct pulp capping in modern clinical dentistry. As it was known to have potential to induce hard tissue repair, this chemical has been applied to the exposed dental pulp and the hard tissue is expected to be regenerated above the pulp. During the reparative process of exposed pulp, primary odontoblasts that were lost as a result of extensive damage are replaced with newly differentiated odontoblast-like cells. This process is known to follow the sequential steps of proliferation, migration, and differentiation of progenitor cells. This research will examine the relationship between calcium hydroxide and the recruitment, proliferation, and mineralization of postnatal dental stem cells, obtained from an immature dental tissue of beagle dogs. Immunocytochemical staining and reverse transcriptase-polymerase chain reaction were used to identify the putative stem cell markers. Immunoblot analysis, wound healing assay, cell migration assay, and alizarin red staining were used to evaluate proliferation, migration, and mineralization capacity of the calcium hydroxide-treated stem cells. As an in vivo study, a combination of calcium hydroxide and autologous dental pulp stem cells (DPSCs) was applied for the treatment of intentionally created tooth defects on the premolars and the molars in beagle dogs to observe dentin regeneration. Ex vivo expanded DPSCs and periodontal ligament stem cells expressed STRO-1 and CD146, the mesenchymal stem cell markers. It was evident that calcium hydroxide increased recruitment, migration, proliferation, and mineralization of the DPSCs and periodontal ligament stem cells. Such results are valuable for future availability of DPSCs, which are recently focused as the stem cell reservoir for regeneration of dentin upon tooth injury, as well as for elucidation of the role of calcium hydroxide in pulp capping therapy.

Acemannan, an extracted product from Aloe vera, stimulates dental pulp cell proliferation, differentiation, mineralization, and dentin formation

This study investigated the effect of acemannan (Aloe vera gel polysaccharide) on dentin formation. Primary human dental pulp cells were treated with acemannan. New DNA synthesis, bone morphogenetic protein-2, alkaline phosphatase activity, dentin sialoprotein expression, and mineralization were determined by [(3)H]-thymidine incorporation, enzyme-linked immunosorbent assay, biochemical assay, western blotting, and Alizarin Red staining, respectively. Then the upper first molars of 24 male Sprague Dawley rats were intentionally exposed and capped with either acemannan or calcium hydroxide. At day 28, the teeth were histopathologically examined and evaluated for the degree of inflammation, dentin bridge formation, and pulp tissue organization. The results revealed that acemannan significantly increased pulp cell proliferation, bone morphogenetic protein-2, alkaline phosphatase activity, dentin sialoprotein expression, and mineralization, compared with the untreated group. The acemannan-treated group also exhibited a complete homogeneous calcified dentin bridge and good pulp tissue organization, whereas neither was detected in the calcium hydroxide-treated and sham groups. In the acemannan-treated group, either mild or no inflammation was found, whereas the other groups had various degrees of inflammation. The data suggest that acemannan promotes dentin formation by stimulating primary human dental pulp cell proliferation, differentiation, extracellular matrix formation, and mineralization. Acemannan also has pulpal biocompatibility and promotes soft tissue organization.

Rat molar teeth as a study model for direct pulp capping research in dentistry

The aim of this review is to evaluate the suitability of rat molar teeth in preclinical evaluation of medical devices for direct pulp capping. The ISO standard 7405 states clearly that only non-rodent mammals are suitable species for animal research in dentistry. Furthermore, without clear justification a considerable number of researchers previously rejected results of animal experiments concerning preclinical evaluation of the biocompatibility of dental materials undertaken in rat molar teeth. However, in the past 50 years about 70 studies have been published using rat molar teeth in order to evaluate direct pulp capping, pulpotomies and tissue reactions after pulp exposure. Numerous studies showed that the healing of rat molar pulp tissue after direct pulp capping is histologically comparable with humans and other animal species pulp tissue. Rat molar teeth, including pulp tissue, can be seen anatomically, histologically, biologically, and physiologically as miniature human molar teeth. Hence, the essential biological reactions of the pulp tissue and the interaction during the different stages of wound healing of rat molar teeth are comparable with that of other mammals. Rat molar teeth are a valid study model in order to provide valuable data concerning pulp tissue reaction after direct pulp capping and related questions in dentistry. Therefore, the use of rats may significantly reduce the number of currently used higher animals in research. Tests in higher developed animals should be limited to experiments which clarify inconsistent results. However, some technical difficulties, like the small size of rat molar teeth must be dealt with before undertaking any research.

Modulation of bone resorption by phosphorylation state of bone sialoprotein

We have determined transmembrane protein tyrosine phosphorylation (outside-in signaling) in cultured osteoclasts and macrophages in response to added native purified bone sialoprotein (nBSP) and its dephosphorylated form (dBSP). There were selective/differential and potent inhibitory effects by dBSP and minimal effect by nBSP on intracellular tyrosine phosphorylation in macrophages and osteoclasts. Further studies on the downstream gene expression effects led to identification of a large number of differentially expressed genes in response to nBSP relative to dBSP in both macrophages and osteoclasts. These studies were extended to a bone resorption model using live mouse neonatal calvarial bone organ cultures stimulated by parathyroid hormone (PTH) to undergo bone resorption. Inclusion of nBSP in such cultures showed no effect on type I collagen telopeptide fragment release, hence overall bone resorption, whereas addition of dBSP abolished the PTH-induced bone resorption. The inhibition of bone resorption by dBSP was shown to be unique since in complementary experiments use of integrin receptor binding ligand, GRGDS peptide, offered only partial reduction on overall bone resorption. Quantitative RANKL analysis indicated that mechanistically the PTH-induced bone resorption was inhibited by dBSP via down-regulation of the osteoblastic RANKL production. This conclusion was supported by the RANKL analysis in cultured MC3T3-E1 osteoblast cells. Overall, these studies provided direct evidence for the involvement of covalently bound phosphates on BSP in receptor mediated "outside-in" signaling via transmembrane tyrosine phosphorylation with concurrent effects on downstream gene expressions. The use of a live bone organ culture system augmented these results with further evidence that links the observed in vivo variable state of phosphorylation with bone remodeling.

Partial pulpotomy on caries-free teeth using enamel matrix derivative or calcium hydroxide: a randomized controlled trial

AIM

To compare the effect of enamel matrix derivative (EMD) and calcium hydroxide [Ca(OH)(2)] on exposed human pulp.

METHODOLOGY

Fifteen pairs of human contralateral premolars were intentionally and partially pulpotomized. The exposed pulps were randomly capped with either EMDgel (Emdogain) or a mix of Ca(OH)(2) and sterile water. The subjects recorded pain or discomfort during the first 10 days and were also interviewed and examined by a blinded examiner at 1 day, 2 weeks, 3 and 6 months post-operation. Periapical radiographs were taken prior to the operation, and 3 and 6 months post-operation. After 6 months, the teeth were extracted and processed for histological evaluation. The data were described and analysed using McNemar test and Kaplan-Meier survival analysis.

RESULTS

The EMDgel-treated teeth had significantly less tooth hypersensitivity than the Ca(OH)(2)-treated teeth during the first 2 weeks (P = 0.031) but were not significantly different after 2 weeks (P = 0.125). No detectable periapical radiographic changes were observed in any teeth and radiographic evidence of dentine bridge formation from both groups were not significantly different during the follow-up periods (P > 0.05). Histological evaluation demonstrated that the Ca(OH)(2)-treated teeth had less inflammation and more dentine bridge formation than those in the EMDgel-treated teeth.

CONCLUSIONS

After 6 months, healthy pulps capped with Ca(OH)(2) had more favourable results than counterparts capped with EMDgel. However, similar clinical and radiographic results were seen in both groups.

Bioactive materials in endodontics

Endodontic treatment in dentistry is a delicate procedure and many treatment attempts fail. Despite constant development of new root canal filling techniques, the clinician is confronted with both a complex root canal system and the use of filling materials that are harmful for periapical tissues. This paper evaluates reported studies on biomaterials used in endodontics, including calcium hydroxide, mineral trioxide aggregate, calcium phosphate ceramics and calcium phosphate cements. Special emphasis is made on promising new biomaterials, such as injectable bone substitute and injectable calcium phosphate cements. These materials, which combine biocompatibility, bioactivity and rheological properties, could be good alternatives in endodontics as root canal fillers. They could also be used as drug-delivery vehicles (e.g., for antibiotics and growth factors) or as scaffolds in pulp tissue engineering.