Agarose-based spheroid culture enhanced stemness and promoted odontogenic differentiation potential of human dental follicle cells in vitro

Human dental follicle cells (HDFCs) are an ideal cell source of stem cells for dental tissue repair and regeneration and they have great potential for regenerative medicine applications. However, the conventional monolayer culture usually reduces cell proliferation and differentiation potential due to the continuous passage during in vitro expansion. In this study, primary HDFC spheroids were generated on 1% agarose, and the HDFCs spontaneously formed cell spheroids in the agarose-coated dishes. Compared with monolayer culture, the spheroid-derived HDFCs exhibited increased proliferative ability for later passage HDFCs as analysed by Cell Counting Kit-8 (CCK-8). The transcription-quantitative polymerase chain reaction (qRT-PCR), western blot and immunofluorescence assay showed that the expression of stemness marker genes Sox2, Oct4 and Nanog was increased significantly in the HDFC spheroids. Furthermore, we found that the odontogenic differentiation capability of HDFCs was significantly improved by spheroid culture in the agarose-coated dishes. On the other hand, the osteogenic differentiation capability was weakened compared with monolayer culture. Our results suggest that spheroid formation of HDFCs in agarose-coated dishes partially restores the proliferative ability of HDFCs at later passages, enhances their stemness and improves odontogenic differentiation capability in vitro. Therefore, spheroid formation of HDFCs has great therapeutic potential for stem cell clinical therapy.

Epigallocatechin-3-Gallate Promotes Osteo-/Odontogenic Differentiation of Stem Cells from the Apical Papilla through Activating the BMP-Smad Signaling Pathway

Stem cells from apical papilla (SCAPs) are desirable sources of dentin regeneration. Epigallocatechin-3-gallate (EGCG), a natural component of green tea, shows potential in promoting the osteogenic differentiation of bone mesenchymal stem cells. However, whether EGCG regulates the odontogenic differentiation of SCAPs and how this occurs remain unknown. SCAPs from immature human third molars (16–20 years, n = 5) were treated with a medium containing different concentrations of EGCG or bone morphogenic protein 2 (BMP2), with or without LDN193189 (an inhibitor of the canonical BMP pathway). Cell proliferation and migration were analyzed using a CCK-8 assay and wound-healing assay, respectively. Osteo-/odontogenic differentiation was evaluated via alkaline phosphatase staining, alizarin red S staining, and the expression of osteo-/odontogenic markers using qPCR and Western blotting. We found that EGCG (1 or 10 μM) promoted the proliferation of SCAPs, increased alkaline phosphatase activity and mineral deposition, and upregulated the expression of osteo-/odontogenic markers including dentin sialophosphoprotein (Dspp), dentin matrix protein-1 (Dmp-1), bone sialoprotein (Bsp), and Type I collagen (Col1), along with the elevated expression of BMP2 and phosphorylation level of Smad1/5/9 (p < 0.01). EGCG at concentrations below 10 μM had no significant influence on cell migration. Moreover, EGCG-induced osteo-/odontogenic differentiation was significantly attenuated via LDN193189 treatment (p < 0.01). Furthermore, EGCG showed the ability to promote mineralization comparable with that of recombinant BMP2. Our study demonstrated that EGCG promotes the osteo-/odontogenic differentiation of SCAPs through the BMP–Smad signaling pathway.

RORα Regulates Odontoblastic Differentiation and Mediates the Pro-Odontogenic Effect of Melatonin on Dental Papilla Cells

Dental papilla cells (DPCs), precursors of odontoblasts, are considered promising seed cells for tissue engineering. Emerging evidence suggests that melatonin promotes odontoblastic differentiation of DPCs and affects tooth development, although the precise mechanisms remain unknown. Retinoid acid receptor-related orphan receptor α (RORα) is a nuclear receptor for melatonin that plays a critical role in cell differentiation and embryonic development. This study aimed to explore the role of RORα in odontoblastic differentiation and determine whether melatonin exerts its pro-odontogenic effect via RORα. Herein, we observed that RORα was expressed in DPCs and was significantly increased during odontoblastic differentiation in vitro and in vivo. The overexpression of RORα upregulated the expression of odontogenic markers, alkaline phosphatase (ALP) activity and mineralized nodules formation (p < 0.05). In contrast, odontoblastic differentiation of DPCs was suppressed by RORα knockdown. Moreover, we found that melatonin elevated the expression of odontogenic markers, which was accompanied by the upregulation of RORα (p < 0.001). Utilising small interfering RNA, we further demonstrated that RORα inhibition attenuated melatonin-induced odontogenic gene expression, ALP activity and matrix mineralisation (p < 0.01). Collectively, these results provide the first evidence that RORα can promote odontoblastic differentiation of DPCs and mediate the pro-odontogenic effect of melatonin.

Melatonin-induced suppression of DNA methylation promotes odontogenic differentiation in human dental pulp cells

Differentiation potency of human dental pulp cells (hDPCs) is essential for dentin regeneration. DNA methylation is one of the major epigenetic mechanisms and is suggested to involve in differentiation of hDPCs, the machinery of which includes DNA methyltransferase enzymes (DNMTs) and methyl-CpG-binding domain proteins (MBDs). Our previous study has found that melatonin (MT) promoted hDPC differentiation, but its mechanism remains elusive. We aimed to investigate the role of DNA methylation in the promotion of MT to differentiation of hDPCs in vitro. hDPCs were cultured in basal growth medium (CO) or odontogenic medium (OM) exposed to MT at different concentrations (0, 10-12, 10-10, 10-8, 10-6, 10-4 M). The cell growth was analyzed using Cell Counting Kit-8 assay, and mineralized tissue formation was measured using Alizarin red staining. The expression of the 10 genes (DNMT1, DNMT3A, DNMT3B, MBD1-6, MeCP2) was determined using real-time qPCR and western blotting. The abundance of MeCP2 in the nuclei was evaluated using immunofluorescence analysis. Global methylation level was tested using ELISA. We found that mineralized tissue formation significantly increased in OM with MT at 10-4 M, while the levels of MeCP2 and global DNA methylation level declined. The expression of MBD1, MBD3, and MBD4 significantly increased in OM alone, and the expession of DNMT1 and MBD2 was decreased. These results indicate that MT promotes odontogenic differentiation of hDPCs in vitro by regulating the levels of DNMT1, MeCP2, and global DNA methylation, suggesting that MT-induced DNA methylation machinery may play an important role in tooth regeneration.

Exposure to persistent organic pollutants during tooth formation: molecular mechanisms and clinical findings

Persistent organic pollutants (POPs) constitute a relevant part of environmental pollution. POPs are chemical compounds that persist for a long time in the environment, bio-accumulate in the human body and determine significant adverse consequences to human health. The characteristics of these substances are lipo-affinity, semi-volatility and resistance to the degradation processes. Results deriving from several different studies attest that exposure to the main classes of POPs results in multiple toxic effects on humans and experimental animal models. Among the various alterations caused by exposition to and bio-accumulation of POPs, there are abnormalities in tooth formation and related hard dental tissue structure, especially enamel. This review aimed to describe the close association between the exposure of these compounds during the development of the tooth germ and the occurrence of tooth structural anomalies. Indeed, structural defects of the enamel have as possible consequences higher susceptibility of the tooth to caries disease and higher fragility of the crown to the occlusal trauma.

Comparison of sensitivity of bacteria isolated in odontogenic infections to ceftriaxone and amoxicillin-clavulanate

BACKGROUND

Odontogenic infections is a cause of mortality and morbidity in maxillofacial patients. This is largely due to resistance of organisms to antibiotics prescribed.

OBJECTIVES

To isolate organisms involved in odontogenic infections and compare the sensitivity of the organisms to Ceftriaxone and Amoxicillin-Clavulanate.

METHODS

The causative organisms and antibiotic sensitivity were determined by the following steps: Aspiration of pus done with needle, sample of pus or exudate collected using sterile swab if aspiration was unsuccessful and specimen were placed in transport media (thioglycolatebroth) and sent immediately to microbiology laboratory for culture of organisms and antibiotic sensitivity.

RESULTS

Out of a total 55 samples taken for bacteriology, 42 (76.4%) yielded positive culture for bacteria. A total number of 21 bacteria species were identified from the positive cultures. Overall, 52% of isolated organisms were sensitive to amoxicillin-clavulanate, 70% were sensitive to Ceftriaxone while 24% were resistant to both antibiotics (Table 3). Ceftriaxone was statistically significantly more potent in inhibiting bacteria growth than amoxicillin-clavulanate (P =0.009). [Table: see text].

hPL promotes osteogenic differentiation of stem cells in 3D scaffolds

Human platelet lysate (hPL) has been considered as the preferred supplement for the xeno-free stem cell culture for many years. However, the biological effect of hPL on the proliferation and differentiation of dental stem cells combined with the use of medical grade synthetic biomaterial is still under investigation. Thus, the optimal scaffold composition, cell type and specific growth conditions, yet need to be formulated. In this study, we aimed to investigate the regenerative potential of dental stem cells seeded on synthetic scaffolds and maintained in osteogenic media supplemented with either hPL or xeno-derived fetal bovine serum (FBS). Two types of dental stem cells were isolated from human impacted third molars and intact teeth; stem cells of apical papilla (SCAP) and periodontal ligament stem cells (PDLSCs). Cells were expanded in cell culture media supplemented with either hPL or FBS. Consequently, proliferative capacity, immunophenotypic characteristics and multilineage differentiation potential of the derived cells were evaluated on monolayer culture (2D) and on synthetic scaffolds fabricated from poly ’lactic-co-glycolic’ acid (PLGA) (3D). The functionality of the induced cells was examined by measuring the concentration of osteogenic markers ALP, OCN and OPN at different time points. Our results indicate that the isolated dental stem cells showed similar mesenchymal characteristics when cultured on hPL or FBS-containing culture media. Scanning electron microscopy (SEM) and H&E staining revealed the proper adherence of the derived cells on the 3D scaffold cultures. Moreover, the increase in the concentration of osteogenic markers proved that hPL was able to produce functional osteoblasts in both culture conditions (2D and 3D), in a way similar to FBS culture. These results reveal that hPL provides a suitable substitute to the animal-derived serum, for the growth and functionality of both SCAP and PDLSCs. Thus the use of hPL, in combination with PLGA scaffolds, can be useful in future clinical trials for dental regeneration.

Enhanced Capability of Bone Morphogenetic Protein 2-loaded Mesoporous Calcium Silicate Scaffolds to Induce Odontogenic Differentiation of Human Dental Pulp Cells

INTRODUCTION

Calcium silicate bioceramics have been broadly used as reparative or grafting materials with good bioactivity and biocompatibility in dental application. It has been shown that applying a mesoporous process to calcium silicate gives it great potential as a controlled drug delivery system.

METHODS

The aim of this study was to investigate a novel osteoinductive scaffold by loading bone morphogenetic protein 2 (BMP-2) to mesoporous calcium silicate (MesoCS) and fabricating it as 3-dimensional scaffolds using fused deposition modeling combined with polycaprolactone.

RESULTS

The MesoCS/BMP-2 scaffold showed similar patterns to that of a calcium silicate scaffold in releasing calcium and silicon ions in a simulated body fluid (SBF) immersion test for 7 days, but BMP-2 continued releasing from the MesoCS/BMP-2 scaffold significantly more than the CS scaffold from 48 hours to 7 days. Adhesion and proliferation of human dental pulp cells cultured on a MesoCS/BMP-2 scaffold were also more significant than scaffolds without BMP-2 or mesoporous as well as the results of the test on alkaline phosphatase activity.

CONCLUSIONS

The results support that the novel 3-dimensional-printed MesoCS scaffold performed well as BMP-2 delivery system and would be an ideal odontoinductive biomaterial in regenerative endodontics.

High-Throughput Assessment and Modeling of a Polymer Library Regulating Human Dental Pulp-Derived Stem Cell Behavior

The identification of biomaterials that modulate cell responses is a crucial task for tissue engineering and cell therapy. The identification of novel materials is complicated by the immense number of synthesizable polymers and the time required for testing each material experimentally. In the current study, polymeric biomaterial-cell interactions were assessed rapidly using a microarray format. The attachment, proliferation, and differentiation of human dental pulp stem cells (hDPSCs) were investigated on 141 homopolymers and 400 diverse copolymers. The copolymer of isooctyl acrylate and 2-(methacryloyloxy)ethyl acetoacetate achieved the highest attachment and proliferation of hDPSC, whereas high cell attachment and differentiation of hDPSC were observed on the copolymer of isooctyl acrylate and trimethylolpropane ethoxylate triacrylate. Computational models were generated, relating polymer properties to cellular responses. These models could accurately predict cell behavior for up to 95% of materials within a test set. The models identified several functional groups as being important for supporting specific cell responses. In particular, oxygen-containing chemical moieties, including fragments from the acrylate/acrylamide backbone of the polymers, promoted cell attachment. Small hydrocarbon fragments originating from polymer pendant groups promoted cell proliferation and differentiation. These computational models constitute a key tool to direct the discovery of novel materials within the enormous chemical space available to researchers.

Adrenomedullin promotes the odontogenic differentiation of dental pulp stem cells through CREB/BMP2 signaling pathway

Adrenomedullin (AM) could promote the proliferation, the odontogenic differentiation and inhibit the apoptosis of dental pulp stem cells (DPSCs). AM in combination with DPSCs may be an effective strategy for pulp repair. However, there was no report on the mechanisms of AM in the odontogenic differentiation of DPSCs. The aim of this study is to investigate the molecular mechanisms through which AM promotes the odontogenic differentiation of DPSCs. Freshly extracted wisdom teeth were obtained from 27 patients. Cells at passage 3 to passage 5 were used in this study. DPSCs were treated with or without 10-7 M AM in Dulbecco's modified Eagle's medium culture, and then the accumulated calcium deposition was analyzed after 21 days by using alizarin red S staining. Odontogenic differentiation markers were determined by western blot analysis and quantitative real-time PCR. Western blot analysis results showed that AM had the capability of promoting the odontogenic differentiation of DPSCs and AM could enhance the phosphorylation of CREB and up-regulate the expression of BMP2. H89 is a CREB inhibitor which can inhibit the odontogenic differentiation of DPSCs through inhibiting the phosphorylation of CREB. Noggin could inhibit the odontogenic differentiation of DPSCs through inhibiting the activity of BMP2. These results indicated that AM could promote the odontogenic differentiation of DPSCs by upregulating the expression of BMP2 through the CREB signaling pathway.

Timing of dental development in osteogenesis imperfecta patients with and without bisphosphonate treatment

Bisphosphonates have established their role as medical therapy for pediatric osteogenesis imperfecta (OI) patients. Since bisphosphonates have also been shown to delay tooth development in animal models, we aimed to assess whether the medication has a similar effect on children with OI. In this cross-sectional study, bisphosphonate-treated OI patients of whom dental panoramic tomograph was taken between 3 and 16years of age formed the study group. The patients, 22 in total, had been treated with pamidronate, zoledronic acid or risedronate for at least one year before the radiography. Developmental stage of the permanent teeth, resorption of the deciduous teeth, and number of the erupted permanent teeth were radiographically assessed in the left mandibular quadrant. Dental panoramic tomographs of 50 OI patients, naïve to bisphosphonates, and of 50 healthy individuals of the same age were used as controls. The dental development was statistically significantly accelerated in the OI group naïve to bisphosphonates showing median advancement of dental age by 0.63years from chronological age and median increase in the number of erupted teeth by 0.31 as compared to Finnish norms. Bisphosphonate-treated OI patients displayed, however, age-appropriate dental development. The OI patients not treated with bisphosphonates also showed statistically significantly faster resorption of the deciduous teeth than the treated ones, and displayed an altered interrelationship between the resorption stage of an individual primary tooth and the developmental stage of the succedaneous permanent tooth, unlike the OI patients treated with bisphosphonate. No correlation between either cumulative bisphosphonate dose or between treatment length and any measured component of the dental development was found. To conclude, OI itself was found to lead to advanced dental development. Bisphosphonate treatment had a delaying effect in all the three aspects studied, resulting in a rate of dental development indistinguishable from normal.

Dioxin Alters Gene Expression in Mouse Embryonic Tooth Explants

Dioxins are ubiquitous environmental poisons that cause disturbances in developing organs, including the teeth. Exposure to 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) at the cap stage leads to reduced tooth size and deformation of cuspal morphology. Our hypothesis was that TCDD affects the expression of genes specific for tooth development, which leads to these aberrations. Mouse embryonic E14 tooth germs were cultured for 24 hrs with/without 1 μM TCDD. Analysis of total RNA on Affymetrix arrays showed that TCDD altered the expression of 31 known genes by a fold factor of at least 2. Genes implied in tooth development expressed only slight changes. Genes active at the cap stage were selected for quantitative PCR analysis. Of these, the most highly up-regulated were Follistatin and Runx2, while TGFβ 1 and p21 were the most down-regulated genes. Incomplete tooth morphogenesis caused by TCDD may thus result from modified expression of developmentally regulated genes.

Microspheres Assembled from Chitosan-Graft-Poly(lactic acid) Micelle-Like Core-Shell Nanospheres for Distinctly Controlled Release of Hydrophobic and Hydrophilic Biomolecules

To simultaneously control inflammation and facilitate dentin regeneration, a copolymeric micelle-in-microsphere platform is developed in this study, aiming to simultaneously release a hydrophobic drug to suppress inflammation and a hydrophilic biomolecule to enhance odontogenic differentiation of dental pulp stem cells in a distinctly controlled fashion. A series of chitosan-graft-poly(lactic acid) copolymers is synthesized with varying lactic acid and chitosan weight ratios, self-assembled into nanoscale micelle-like core-shell structures in an aqueous system, and subsequently crosslinked into microspheres through electrostatic interaction with sodium tripolyphosphate. A hydrophobic biomolecule either coumarin-6 or fluocinolone acetonide (FA) is encapsulated into the hydrophobic cores of the micelles, while a hydrophilic biomolecule either bovine serum albumin or bone morphogenetic protein 2 (BMP-2) is entrapped in the hydrophilic shells and the interspaces among the micelles. Both hydrophobic and hydrophilic biomolecules are delivered with distinct and tunable release patterns. Delivery of FA and BMP-2 simultaneously suppresses inflammation and enhances odontogenesis, resulting in significantly enhanced mineralized tissue regeneration. This result also demonstrates the potential for this novel delivery system to deliver multiple therapeutics and to achieve synergistic effects.

Procaine Inhibits Osteo/Odontogenesis through Wnt/β-Catenin Inactivation

Introduction

Periodontitis is a complex pathology characterized by the loss of alveolar bone. The causes and the mechanisms that promote this bone resorption still remain unknown. The knowledge of the critical regulators involved in the alteration of alveolar bone homeostasis is of great importance for developing molecular therapies. Procaine is an anesthetic drug with demethylant properties, mainly used by dentists in oral surgeries. The inhibitor role of Wnt signaling of procaine was described in vitro in colon cancer cells.

Methods

In this work we evaluated the role of procaine (1 uM) in osteo/odontogenesis of rat bone marrow mesenchymal stem cells. Similarly, the mechanisms whereby procaine achieves these effects were also studied.

Results

Procaine administration led to a drastic decrease of calcium content, alkaline phosphatase activity, alizarin red staining and an increase in the expression of Matrix Gla Protein. With respect to osteo/odontogenic markers, procaine decreased early and mature osteo/odontogenic markers. In parallel, procaine inhibited canonical Wnt/β-catenin pathway, observing a loss of nuclear β-catenin, a decrease in Lrp5 and Frizzled 3, a significant increase of sclerostin and Gsk3β and an increase of phosphorylated β-catenin. The combination of osteo/odontogenic stimuli and Lithium Chloride decreased mRNA expression of Gsk3β, recovered by Procaine. Furthermore it was proved that Procaine alone dose dependently increases the expression of Gsk3β and β-catenin phosphorylation. These effects of procaine were also observed on mature osteoblast. Interestingly, at this concentration of procaine no demethylant effects were observed.

Conclusions

Our results demonstrated that procaine administration drastically reduced the mineralization and osteo/odontogenesis of bone marrow mesenchymal stem cells inhibiting Wnt/β-catenin pathway through the increase of Gsk3β expression and β-catenin phosphorylation.

Delivery of dexamethasone from bioactive nanofiber matrices stimulates odontogenesis of human dental pulp cells through integrin/BMP/mTOR signaling pathways

Therapeutically relevant design of scaffolds is of special importance in the repair and regeneration of tissues including dentin and pulp. Here we exploit nanofiber matrices that incorporate bioactive glass nanoparticles (BGNs) and deliver the odontogenic drug dexamethasone (DEX) to stimulate the odontogenic differentiation of human dental pulp cells (HDPCs). DEX molecules were first loaded onto the BGN, and then the DEX-BGN complex was incorporated within the biopolymer nanofiber matrix through electrospinning. The release of DEX continued over a month, showing a slow releasing profile. HDPCs cultured on the DEX-releasing BGN matrices were viable, proliferating well up to 14 days. The odontogenic differentiation, as assessed by alkaline phosphatase activity, mRNA expression of genes, and mineralization, was significantly stimulated on the matrices incorporating BGN and further on those releasing DEX. The DEX-releasing BGN matrices highly upregulated the expression of the integrin subsets α1, α5, and β3 as well as integrin downstream signaling molecules, including focal adhesion kinase (FAK), Paxillin, and RhoA, and activated bone morphogenetic protein mRNA and phosphorylation of Smad1/5/8. Furthermore, the DEX-releasing BGN-matrices stimulated Akt and mammalian target of rapamycin (mTOR), which was proven by the inhibition study. Collectively, the designed therapeutic nanofiber matrices that incorporate BGN and deliver DEX were demonstrated to promote odontogenesis of HDPCs, and the integrins, bone morphogenetic protein, and mTOR signaling pathways are proposed to be the possible molecular mechanisms. While further in vivo studies are still needed, the DEX-releasing bioactive scaffolds are considered as a potential therapeutic nanomatrix for regenerative endodontics and tissue engineering.

Endodontic treatment of trauma-induced necrotic immature teeth using a tricalcium silicate-based bioactive cement. A report of 3 cases with 24-month follow-up

BACKGROUND

Pulp necrosis is the second most common complication after traumatic dental injuries and occurs mostly within the first 6-24 months of follow-up period, depending on the type of dental trauma.

CASE REPORT

Three cases with endodontic treatment scenarios of trauma-induced necrosis in immature permanent anterior teeth. All cases were treated by full canal obturation with Biodentine (Septodont, Saint Maur des Fosses, France) and documented for a follow-up period of 24 months.

CONCLUSION

Copious irrigation of the root canal, minimal mechanical preparation, use of calcium hydroxide for a short period of time and complete obturation of these immature teeth with a bioactive cement with superior mechanical properties such as Biodentine were the prominent reasons attributed to the success of these three cases.

TLR signalling can modify the mineralization of tooth germ

OBJECTIVE

The aim of this work is to investigate the possible role of Toll-like receptor 4 (TLR4) during the development of mouse tooth germ. TLR4 is well known to inhibit mineralization and cause inflammation in mature odontoblasts and dental pulp cells. However, unlike these pathological functions of TLR4, little is known about the developmental function(s) of TLR4 during tooth development.

MATERIALS AND METHODS

TLR4 expression was studied via Western blot in developing lower mouse incisors from E13.5 to E18.5. To generate functional data about the effects of TLR4, a specific agonist (LPS) was applied to the medium of in vitro tooth germ cultures, followed by Western blot, histochemical staining, ELISA assay, in situ hybridization and RT-qPCR.

RESULTS

Increased accumulation of biotin-labelled LPS was detected in the enamel organ and in preodontoblasts. LPS treatment induced degradation of the inhibitor molecule (IκB) of the NF-κB signalling pathway. However, no morphological alterations were detected in cultured tissue after LPS addition at the applied dosage. Activation of TLR4 inhibited the mineralization of enamel and dentin, as demonstrated by alizarin red staining and as decreased levels of collagen type X. mRNA expression of ameloblastin was elevated after LPS administration.

CONCLUSION

These results demonstrate that TLR4 may decrease the mineralization of hard tissues of the tooth germ and may trigger the maturation of ameloblasts; it can give valuable information to understand better congenital tooth abnormalities.

Vitamin D Promotes Odontogenic Differentiation of Human Dental Pulp Cells via ERK Activation

The active metabolite of vitamin D such as 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) is a well-known key regulatory factor in bone metabolism. However, little is known about the potential of vitamin D as an odontogenic inducer in human dental pulp cells (HDPCs) in vitro. The purpose of this study was to evaluate the effect of vitamin D3 metabolite, 1α,25(OH)2D3, on odontoblastic differentiation in HDPCs. HDPCs extracted from maxillary supernumerary incisors and third molars were directly cultured with 1α,25(OH)2D3 in the absence of differentiation-inducing factors. Treatment of HDPCs with 1α,25(OH)2D3 at a concentration of 10 nM or 100 nM significantly upregulated the expression of dentin sialophosphoprotein (DSPP) and dentin matrix protein1 (DMP1), the odontogenesis-related genes. Also, 1α,25(OH)2D3 enhanced the alkaline phosphatase (ALP) activity and mineralization in HDPCs. In addition, 1α,25(OH)2D3 induced activation of extracellular signal-regulated kinases (ERKs), whereas the ERK inhibitor U0126 ameliorated the upregulation of DSPP and DMP1 and reduced the mineralization enhanced by 1α,25(OH)2D3. These results demonstrated that 1α,25(OH)2D3 promoted odontoblastic differentiation of HDPCs via modulating ERK activation.

The non-canonical BMP and Wnt/β-catenin signaling pathways orchestrate early tooth development

BMP and Wnt signaling pathways play a crucial role in organogenesis, including tooth development. Despite extensive studies, the exact functions, as well as if and how these two pathways act coordinately in regulating early tooth development, remain elusive. In this study, we dissected regulatory functions of BMP and Wnt pathways in early tooth development using a transgenic noggin (Nog) overexpression model (K14Cre;pNog). It exhibits early arrested tooth development, accompanied by reduced cell proliferation and loss of odontogenic fate marker Pitx2 expression in the dental epithelium. We demonstrated that overexpression of Nog disrupted BMP non-canonical activity, which led to a dramatic reduction of cell proliferation rate but did not affect Pitx2 expression. We further identified a novel function of Nog by inhibiting Wnt/β-catenin signaling, causing loss of Pitx2 expression. Co-immunoprecipitation and TOPflash assays revealed direct binding of Nog to Wnts to functionally prevent Wnt/β-catenin signaling. In situ PLA and immunohistochemistry on Nog mutants confirmed in vivo interaction between endogenous Nog and Wnts and modulation of Wnt signaling by Nog in tooth germs. Genetic rescue experiments presented evidence that both BMP and Wnt signaling pathways contribute to cell proliferation regulation in the dental epithelium, with Wnt signaling also controlling the odontogenic fate. Reactivation of both BMP and Wnt signaling pathways, but not of only one of them, rescued tooth developmental defects in K14Cre;pNog mice, in which Wnt signaling can be substituted by transgenic activation of Pitx2. Our results reveal the orchestration of non-canonical BMP and Wnt/β-catenin signaling pathways in the regulation of early tooth development.

Immature permanent teeth with apical periodontitis and abscess treated by regenerative endodontic treatment using calcium hydroxide and MTA: a report of two cases

Regenerative endodontic techniques have been introduced to overcome the limits of the traditional apexification approach and allow continued root development after treatment of infected immature permanent teeth. The purpose of this report was to describe two cases with severe apical periodontitis and abscess that were successfully treated by regenerative endodontic treatment using calcium hydroxide. The report involves treatment of two patients who developed apical periodontitis and abscesses on their immature premolars affected by dens evaginatus. Regenerative endodontic treatment was performed using calcium hydroxide. The treatment procedures have been shown to result in increased thickening of root walls and encourage continued root development. Different outcomes were observed when calcium hydroxide was placed past and within the coronal half of the canal. Calcium hydroxide can be used as an effective medicament in regenerative endodontic technique, and successful regeneration can be expected even in severe cases of apical periodontitis or abscess.

Ginsenoside Rg1 of Panax ginseng stimulates the proliferation, odontogenic/osteogenic differentiation and gene expression profiles of human dental pulp stem cells

Ginsenoside Rg1 is one of the major active components of Panax ginseng C. A. Mey. Human dental pulp stem cells (hDPSCs) play an important role in the dentin formation, reparation and tooth tissue engineering. This study investigated the effects of ginsenoside Rg1 on the proliferation, odontogenic differentiation of hDPSCs and revealed the underlying molecular mechanisms. [³H]-thymidine incorporation assay and cell cycle analysis were applied to investigate the proliferation of hDPSCs after the treatment of ginsenoside Rg1. Immunocytochemistry analysis and fluorescent quantitative reverse transcriptase-polymerase chain reaction (FQ-PCR) were performed to evaluate the odontogenic differentiation of hDPSCs. Gene and protein expressions of bone morphogenetic protein-2 (BMP-2) and fibroblast growth factor 2 (FGF2) were detected by FQ-PCR and enzyme-linked immunosorbent assay. The Roche Nimblegen Whole Human Genome Expression profile microarray was used to detected representative gene expression profiles of hDPSCs by ginsenoside Rg1. The results indicated that ginsenoside Rg1 significantly increased hDPSCs proliferation (p<0.05). Gene expressions of DSPP, ALP, OCN, BMP-2, FGF2 and protein expressions of BMP-2 and FGF2 were increased compared with the untreated group (p<0.05). Gene expression profile analysis revealed that 2059 differentially expressed genes were detected by ginsenoside Rg1. Ginsenoside Rg1 promoted the proliferation and differentiation of hDPSCs through alteration of gene expression profiles.

Effects of the enamel matrix derivative on the proliferation and odontogenic differentiation of human dental pulp cells

OBJECTIVE

The enamel matrix derivative (EMD) has a positive effect on the proliferation of human periodontal ligament cells and the healing of periodontal tissues. The aim of this study was to evaluate the effects of EMD on the proliferation and differentiation of human dental pulp cells (hDPCs) in vitro.

METHODS

hDPCs were isolated from human impacted third molars and cultured in vitro. After treatment with100μg/mL EMD, the proliferation of hDPCs was determined by a cell counting kit 8 (CCK8) assay. After incubation in EMD osteogenic induction medium for 14 days, the osteogenic differentiation of hDPCs was evaluated by alkaline phosphatase (ALP) activity, alizarin staining and the expression of osteogenesis-related genes.

RESULTS

The EMD osteogenic induction medium enhanced the proliferation of hDPCs. After osteogenic induction, EMD increased the osteogenic potential of hDPCs, as measured by alkaline phosphatase activity and calcium accumulation; the expression levels of osteogenesis-related genes, such as ALP, DSPP, BMP, and OPN were also upregulated. In addition, the expression levels of odontogenesis-related transcription factors Osterix and Runx2 were upregulated.

CONCLUSIONS

EMD could enhance the mineralization of hDPSCs upregulated the expression of markers for odontoblast/osteoblast-like cells. Further studies are required to determine if EMD can improve pulp tissue repair and regeneration.

The role of lysyl oxidase-like 2 in the odontogenic differentiation of human dental pulp stem cells

Adult human dental pulp stem cells (hDPSCs) are a unique population of precursor cells those are isolated from postnatal dental pulp and have the ability to differentiate into a variety of cell types utilized for the formation of a reparative dentin-like complex. Using LC-MS/MS proteomics approaches, we identified the proteins secreted from the differentiating hDPSCs in mineralization media. Lysyl oxidase-like 2 (LOXL2) was identified as a protein that was down-regulated in the hDPSCs that differentiate into odontoblast-like cells. The role of LOXL2 has not been studied in dental pulp stem cells. LOXL2 mRNA levels were reduced in differentiating hDPSCs, whereas the levels of other LOX family members including LOX, LOXL1, LOXL3, and LOXL4, are increased. The protein expression and secretion levels of LOXL2 were also decreased during odontogenic differentiation. Recombinant LOXL2 protein treatment to hDPSCs resulted in a dose-dependent decrease in the early differentiation and the mineralization accompanying with the lower levels of odontogenic markers such as DSPP, DMP-1 and ALP. These results suggest that LOXL2 has a negative effect on the differentiation of hDPSCs and blocking LOXL2 can promote the hDPSC differentiation to odontoblasts.

Effects of simvastain and enamel matrix derivative on Portland cement with bismuth oxide-induced growth and odontoblastic differentiation in human dental pulp cells

INTRODUCTION

We previously reported that bismuth oxide containing Portland cement (BPC) showed similar biocompatibility to Portland cement (PC) in periodontal ligament cells. However, the bioactivity of simvastatin and Emdogain (Biora AB, Malmö, Sweden) on BPC was not reported. The aim of this study was to evaluate the effects of simvastatin and Emdogain on BPC compared with mineral trioxide aggregate (MTA) in human dental pulp cells (HDPCs).

METHODS

Cell growth was determined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide (MTT) assay. Differentiation was evaluated by alkaline phosphatase (ALP) activity, alizarin red staining, and reverse-transcriptase polymerase chain reaction.

RESULTS

The cell growth of HDPCs exposed to Emdogain and simvastatin plus BPC was superior to those administered BPC alone and similar to those that received MTA for 14 days. The simvastatin and Emdogain groups increased the odontogenic potential of the BPC group with respect to ALP activity, mineralization nodules, messenger RNA expression of ALP, osteopontin, osteocalcin, Runx2, and osterix.

CONCLUSIONS

These results suggest that simvastatin and Emdogain improved cell growth and the differentiation of the BPC group in HDPCs and may be useful ingredients in BPC as pulp-capping material.

Chronic fluoride toxicity: dental fluorosis

Dental fluorosis occurs as a result of excess fluoride ingestion during tooth formation. Enamel fluorosis and primary dentin fluorosis can only occur when teeth are forming, and therefore fluoride exposure (as it relates to dental fluorosis) occurs during childhood. In the permanent dentition, this would begin with the lower incisors, which complete mineralization at approximately 2-3 years of age, and end after mineralization of the third molars. The white opaque appearance of fluorosed enamel is caused by a hypomineralized enamel subsurface. With more severe dental fluorosis, pitting and a loss of the enamel surface occurs, leading to secondary staining (appearing as a brown color). Many of the changes caused by fluoride are related to cell/matrix interactions as the teeth are forming. At the early maturation stage, the relative quantity of amelogenin protein is increased in fluorosed enamel in a dose-related manner. This appears to result from a delay in the removal of amelogenins as the enamel matures. In vitro, when fluoride is incorporated into the mineral, more protein binds to the forming mineral, and protein removal by proteinases is delayed. This suggests that altered protein/mineral interactions are in part responsible for retention of amelogenins and the resultant hypomineralization that occurs in fluorosed enamel. Fluoride also appears to enhance mineral precipitation in forming teeth, resulting in hypermineralized bands of enamel, which are then followed by hypomineralized bands. Enhanced mineral precipitation with local increases in matrix acidity may affect maturation stage ameloblast modulation, potentially explaining the dose-related decrease in cycles of ameloblast modulation from ruffle-ended to smooth-ended cells that occur with fluoride exposure in rodents. Specific cellular effects of fluoride have been implicated, but more research is needed to determine which of these changes are relevant to the formation of fluorosed teeth. As further studies are done, we will better understand the mechanisms responsible for dental fluorosis.

Fluoride intake of children: considerations for dental caries and dental fluorosis

Caries incidence and prevalence have decreased significantly over the last few decades due to the widespread use of fluoride. However, an increase in the prevalence of dental fluorosis has been reported simultaneously in both fluoridated and non-fluoridated communities. Dental fluorosis occurs due to excessive fluoride intake during the critical period of tooth development. For the permanent maxillary central incisors, the window of maximum susceptibility to the occurrence of fluorosis is the first 3 years of life. Thus, during this time, a close monitoring of fluoride intake must be accomplished in order to avoid dental fluorosis. This review describes the main sources of fluoride intake that have been identified: fluoridated drinking water, fluoride toothpaste, dietary fluoride supplements and infant formulas. Recommendations on how to avoid excessive fluoride intake from these sources are also given.

Administration of the bisphosphonate zoledronic acid during tooth development inhibits tooth eruption and formation and induces dental abnormalities in rats

Bisphosphonates (BPs) are potent inhibitors of osteoclastic bone resorption and widely used for the treatment of osteoporosis and metastatic bone diseases. Recently, BPs have also been shown to benefit children with primary and secondary osteoporosis, including osteogenesis imperfecta; however, their long-term safety has not been established yet. Clinical and experimental studies have demonstrated that BPs delay or inhibit tooth eruption. The failure of tooth eruption causes several dental abnormalities. In this study, to determine the effects of BPs on tooth formation, the BP zoledronic acid (ZOL) was injected into 7- and 14-day-old rats, and the development of the mandibular teeth was examined. X-ray analysis demonstrated that ZOL inhibited the eruption of both incisors and molars and their formation, especially in the molar roots. Histological examination showed that, in ZOL-treated animals, alveolar bone remained unresorbed around tooth crowns, which injured ameloblasts and enamel matrix, leading to defects of the enamel. Furthermore, haphazard proliferation of odontogenic epithelium and mesenchyme associated with primitive tooth structures, which resembles human odontomas, was induced at the basal end of incisors but not around the molars. Tooth ankylosis to alveolar bone was occasionally observed in molars. These results suggest that administration of BPs during tooth development has the potential to inhibit tooth eruption and formation and to induce several types of dental abnormalities, which may be attributed to the altered osteoclastic activities.

The effect of retinoic acid on mouse mandibular molar development in vitro, using alkaline phosphatase as a molecular indicator of differentiation

INTRODUCTION

An excellent model system that links evolutionary biology and developmental biology in seeking to understand evolutionary diversity is the study of tooth development in mammals. These studies reflect the diversity of mammalian radiations which bear on the interpretation of South African fossil hominids. Tooth development occurs via epithelio-mesenchymal interactions and involves the production of many substances, including alkaline phosphatase, which is necessary for dentine and enamel formation. Retinoic acid is a known morphogen and is important in tooth development. In excess, retinoic acid has been found to alter the formation of teeth.

OBJECTIVES

In order to determine whether retinoic acid has any effect on tooth morphology, exogenous retinoic acid was administered to developing mouse molar teeth in vitro, and alkaline phosphatase was utilized as an indicator of differentiation.

METHODS

Molars were microdissected from 15.5 day mouse embryo mandibles and cultured at the air: medium interface with or without retinoic acid for seven days. Following fixation and embedding, the explants were sectioned for morphological analysis. Alkaline phosphatase activity was detected using a modified Gomori's histochemical method.

RESULTS AND CONCLUSION

Retinoic acid appeared to retard the growth and differentiation of the molar explants. This was coincident with reduced alkaline phosphatase.

Long-term effects of chemotherapy on caries formation, dental development, and salivary factors in childhood cancer survivors

OBJECTIVE

The aim of this study was to investigate the long-term effects of chemotherapy on oral health and dental development in childhood cancer survivors (CCS).

STUDY DESIGN

Ninety-six CCS patients with a mean age of 10.8 years and 96 healthy children of the same age and sex and social background composed the study group. The caries experience of the children was recorded according to the criteria of the World Health Organization, and plaque-gingival status was evaluated according to the Silness-Loe Index. The children were also investigated for stimulated salivary flow rate, buffer capacity, salivary mutans streptococci, and lactobacilli. Disturbances of enamel mineralization were recorded according to the index of developmental defects in dental enamel. Dental development disturbances were diagnosed on panoramic radiographs.

RESULTS

The caries experience, mutans streptococci, and lactobacilli colonization in CCS children were found significantly higher than in the healthy subjects (P < .05). White/cream colored opacities were the most frequent enamel mineralization disturbances (69.8 %). The occurrence of arrested root development with short V-shaped root malformation was significantly higher in CCS children than in the healthy subjects (P < .05). No statistically significant difference was found between group <or=5 years and >5 years.

CONCLUSION

This current investigation has shown that CCS children are at an increased risk of caries and developmental dental disturbances.

Regulating the Role of Bone Morphogenetic Protein 4 in Tooth Bioengineering

PURPOSE

Culture of the whole organ and regulation of its development using biologic and engineering principles can be used to produce structures and organs for reconstructing defects. The application of these bioengineering approaches in artificial tooth development may be the alternative way to replace missing dentition.

MATERIALS AND METHODS

For the artificial bioengineering of a mouse tooth, tooth buds were dissected and transplanted into the diastema of the developing mandible. The mandiblular primordia containing transplanted tooth buds were culture in vitro and in vivo using a bioengineering method. In addition, to regulate the development of tooth germs, bone morphogenetic protein 4 (BMP4) or its antagonist, Noggin was administered.

RESULTS

After the period of in vitro and in vivo culture, the transplanted tooth germ in the diastema showed tooth development with supportive structure formation. In the BMP-treated group, the bioengineered tooth was observed with increased maturation of cusp and enamel matrix. However, in the Noggin-treated tooth germs, the developing molar had a crater-like appearance with the immature development of the cusp and suppressed formation of the enamel matrix.

CONCLUSIONS

This study confirmed that tooth germ transplantation in the diastema and culture with administration of BMP4 could lead to the mature development of the dental structures. In addition, these results suggest the possibility of bioengineering the tooth in morphogenesis and differentiation even in the toothless area.

Microdontia after chemotherapy in a child treated for neuroblastoma

OBJECTIVE

Chemotherapy used on paediatric oncology patients often causes disturbances in dental development. Aim of this case report is to present the late effects of chemotherapy on dental development in a patient treated for neuroblastoma at early age.

DESIGN

Case report.

RESULTS

This paper presents a female patient treated at early age with surgery and chemotherapy for a neuroblastoma (stage IVS) in the right thorax and massive liver metastases. The examination of the patient at age 11.7 years showed microdontia of six teeth. In three of them size and form of the crown were affected, while in the other three the size was reduced but the form was not affected.

CONCLUSIONS

Chemotherapy on children treated for neuroblastoma can adversely influence tooth development. This has to be taken into consideration by the dentist when monitoring the development of the dentition and occlusion.

Qualitative effects of dioxin on molars vary among inbred mouse strains

OBJECTIVE

We evaluated the effects of different levels of the potent environmental toxicant and teratogen, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), on molar development in mice in six inbred strains, all with TCDD responsive Ahr alleles.

DESIGN

Pregnant females were exposed on gestation day 13 to 4 different levels of TCDD (control, 0.01, 0.1 and 1.0 microg/kg) and their offspring were examined for the frequency of missing third molars (M3s) and for differences in first mandibular molar (M1) cuspal morphology.

RESULTS

Missing M3s were prevalent only in mice in two strains, C3H/HeJ and CBA/J, and their frequency significantly increased with increasing TCDD exposure. The frequency of the M1 variant was high in mice in only one strain, C57BL/10J, and was significantly higher in the treated compared with the control group.

CONCLUSIONS

Inbred mice strains exhibited differential responses to TCDD suggesting that there is a genetic component, beyond Ahr differences, mediating the effects of TCDD on molar development.

Fluoride alters type I collagen expression in the early stages of odontogenesis

Fluoride alters the expression and post-translational modifications of extracellular matrix proteins in dentin. The aim of our study was to determine the effects of fluoride on type I collagen expression during the early stages of tooth germ development in rats. Pregnant dams were divided into three groups and fed a standard diet. From the fifth day of pregnancy the three groups received tap water with, respectively, trace amounts of fluoride (C), a low fluoride concentration (FL) or and a high fluoride concentration (FH). Changes in type I collagen expression and distribution were evaluated. The expression of type I collagen was restricted to the extracellular spaces of cells of mesenchymal origin. In the youngest animals the most intense immunoreactivity for type I collagen was detected in predentin of the FL group. Although the intensity of immunostaining increased in proportion to the age of the animals, the largest increase in the groups investigated was detected in the FL group. We concluded that a low concentration of fluoride can act as a stimulator of type I collagen deposition in the extracellular matrix of dentin, while high concentrations of fluoride have an opposite effect, acting as an inhibitor of type I collagen formation in dentin.

Comparison of mineral trioxide aggregate and calcium hydroxide as pulpotomy agents in young permanent teeth (apexogenesis)

PURPOSE

The purpose of this study was to compare mineral trioxide aggregate (MTA) with calcium hydroxide (Ca(OH)2) clinically and radiographically as a pulpotomy agent in immature permanent teeth (apexogenesis).

METHODS

Fifteen children, each with at least 2 immature permanent teeth requiring pulpotomy (apexogenesis), were selected for this study. All selected teeth were evenly divided into 2 test groups. In group 1, the conventional Ca(OH)2pulpotomy (control) was performed, whereas in group 2, the MTA pulpotomy (experimental) was done. The children were recalled for clinical and radiographic evaluations after 3, 6, and 12 months.

RESULTS

The follow-up evaluations revealed failure due to pain and swelling detected at 6 and 12 months postoperative evaluations in only 2 teeth treated with Ca(OH)2. The remaining 28 teeth appeared to be clinically and radiographically successful 12 months postoperatively. Calcific metamorphosis was a radiographic finding in 2 teeth treated with Ca(OH)2 and 4 teeth treated with MTA.

CONCLUSIONS

Mineral trioxide aggregate showed clinical and radiographic success as a pulpotomy agent in immature permanent teeth (apexogenesis) and seems to be a suitable alternative to calcium hydroxide.

Inhibition of apoptosis in early tooth development alters tooth shape and size

Apoptosis plays important roles in various stages of organogenesis. In this study, we hypothesized that apoptosis would play an important role in tooth morphogenesis. We examined the role of apoptosis in early tooth development by using a caspase inhibitor, z-VAD-fmk, concomitant with in vitro organ culture and tooth germ transplantation into the kidney capsule. Inhibition of apoptosis at the early cap stage did not disrupt the cell proliferation level when compared with controls. However, the macroscopic morphology of mice molar teeth exhibited dramatic alterations after the inhibition of apoptosis. Crown height was reduced, and mesiodistal diameter was increased in a concentration-dependent manner with z-VAD-fmk treatment. Overall, apoptosis in the enamel knot would be necessary for the proper formation of molar teeth, including appropriate shape and size.

Early in vivo and in vitro effects of amelogenin gene splice products on pulp cells

Recombinant amelogenin gene splice products A+4 and A-4, implanted in the pulp, induce the recruitment, proliferation, and differentiation of reparative cells. Our aim was to investigate the precocious events occurring in the pulp 1 d and 3 d after implantation of agarose beads alone or loaded with A+4 or A-4. Proliferation and cell recruitment towards an odonto/osteogenic phenotype were visualized by detection of the proliferation cell nuclear antigen (PCNA) and RP59. After implantation of beads alone or loaded with A+4, at day 3, pulp cells were moderately immunopositive for osteopontin (OP), whereas labeling was strongly positive upon treatment with A-4. Dentin sialoprotein (DSP) labeling was not detectable. Parallel in vitro studies were carried out on odontoblastic and mesenchymal progenitor cells in order to evaluate the effect of the amelogenin peptides on the expression of a series of marker genes involved in the odontoblastic/osteogenic/chondrogenic differentiation pathways. Altogether, our results suggest that the 'signaling' effects of the amelogenin peptides A+4 and A-4 may differ according to the type of target cells, their stage of differentiation, the time of treatment, and the type of amelogenin peptide (A+4 or A-4).

Comparative evaluation of endodontic management of teeth with unformed apices with mineral trioxide aggregate and calcium hydroxide

PURPOSE

The purpose of this study was to compare mineral trioxide aggregate (MTA) and calcium hydroxide (Ca(OH)2) for their efficacies and time taken for formation of apical biological calcific barriers and resolution of periapical radiolucencies, if present at baseline, in teeth with unformed apices.

METHODS

Twenty nonvital permanent maxillary incisors with unformed apices, stratified according to the size of periapical radiolucencies and stage of root development, were equally allocated to MTA and Ca(OH)2 groups. In group 1 (MTA group), after 7 days of disinfection with Ca(OH)2, MTA was packed into the apical one third of the root canals and obturation with gutta percha (GP) was performed in 90% (9/10) of cases within 15 to 30 days. In group 2 (Ca(OH)2 group), obturation was performed following clinical and radiographic depiction of the apical stop.

RESULTS

The mean time taken for apical biological barrier formation was 3 +/- 2.9 months for group 1 and 7 +/- 2.5 months for group 2 (P=.008). The periapical radiolucencies were resolved in 4.6 +/- 1.5 months for group 1 and 4.4 +/- 1.3 months for group 2 (P=.83). The total treatment was completed in 0.75 +/- 0.4859 months and 7 +/- 2.5 months for groups 1 and 2, respectively.

CONCLUSION

The 2 materials were found to be equally efficacious in the management of nonvital teeth with unformed apices. Time taken to complete the treatment and the biological barrier formation in group 1 was significantly less than that for group 2. The healing time for periapical radiolucencies was almost identical.

Alteration of the sialylation pattern of the murine tooth germ after ethanol exposure

BACKGROUND

Ethanol consumption during pregnancy leads to changes in murine dental morphogenesis, dental size, cellular differentiation, enamel mineralization, and delayed eruption. It has been proposed that glycoproteins play a role during embryonic dental development that may determine the dental morphological pattern and extracellular matrix secretion. O-glycosylation and sialylation appear to actively participate in the differentiation and maturation processes. Because glycosylation may be affected by teratogens that can alter the maturation of several organisms, in this work we describe the main modifications of the sialylation pattern in prenatal day (PD) 18.5 murine tooth germs exposed to ethanol.

METHODS

Pregnant female mice were divided into groups that were given 15% or 20% ethanol solutions, or water as a control. The histochemistry of tooth germs from PD 18.5 fetuses was revealed with lectins specific for sialic acid (Neu5Ac), such as Sambucus nigra (SNA), Maackia amurensis (MAA), and Machrobrachium rosenbergii (MRL), and for sialylated-O-glycosidically linked glycans, such as Amaranthus leucocarpus (ALL).

RESULTS

The basement membrane, preameloblasts, inner-enamel epithelium, preodontoblasts, and subodontoblastic cells of the test groups showed changes in labeling according to the 4 lectins used. Intranuclear staining was observed with SNA (specific for Neu5Acalpha2,6Gal/GalNAc) in the control group, but this was reduced in the test groups. The nuclei of dental papillary cells under the experimental conditions were stained with MAA (Neu5Acalpha2,3Gal).

CONCLUSIONS

Dental development involves different types of sialylated O-glycosidically linked glycans that are likely to regulate cell-to-cell and cell-to-matrix interactions. Our results suggest that ethanol consumption during pregnancy alters the sialylation pattern during murine dental morphogenesis.

[The multifaceted effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in organisms, especially dentition changes]

Dioxins are by products of various technological processes in many branches of industry and products of the combustion of chlorine compounds at low temperatures. They include polychlorated dibenzo-p-dioxins and dibenzofurans. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the most dangerous to the human organism and is a model substance to define the toxicity of particular dioxins in mixture. TCDD in small doses exerts a toxic influence on embryos and maturing persons. Dioxin exposure to animals and people causes changes in the immunological system, fetus failure, and defects in fertility and in internal organs and is carcinogenic. Knowledge in this area is rather well documented and has expanded. However, there is little information about dioxin's influence on dentition development. In this review, recent literature reports and the results of own investigations of the general biological effects of dioxins, especially for dentition, are presented.

EGF-R and erbB-2 in murine tooth development after ethanol exposure

BACKGROUND

Alcohol consumption during pregnancy can frequently lead to a congenital disorder known as fetal alcohol syndrome (FAS); however, not all children born to alcoholic women develop FAS. Alcohol consumption may affect diverse organs and systems during embryonic development, including craniofacial structures. Small teeth, enamel alterations, and delayed eruption have been observed after ethanol exposure. Epidermal growth factor receptors (EGF-Rs) participate in dental proliferation and differentiation, and changes in these receptors were considered here to be a likely mechanism associated to the dental anomalies observed in this syndrome. Epidermal growth factor receptor type 1 (EGF-R) and epidermal growth factor receptor type 2 (erbB-2) immunoexpression during the lower first molar morphogenesis was investigated in mouse fetuses exposed to ethanol during gestation.

METHODS

Pregnant female mice were divided into groups, consuming either 5, 10, 15, 20, or 25% ethanol solutions, or water (control group). Heads were obtained from 16.5- and 18.5-day fetuses. Immunohistochemistry was applied to EGF-R and erbB-2.

RESULTS

At days 16.5 and 18.5, fetuses from 15%, 20%, and 25% ethanol groups showed delayed differentiation, degenerative changes in dental epithelial tissues and reduced dental size; additionally, they displayed an enhanced immunoreactivity to EGF-R and erbB-2.

CONCLUSIONS

Our results suggest that ethanol consumption during pregnancy affects the expression of EGF receptors and induces a delay in murine fetal dental morphogenesis. Dental development is a process that involves a number of growth factors; hence we consider that further research is required to show whether the changes in glycosylation and growth-factor signaling pathways observed in other cells are also involved in the alterations observed in this study.

Long-term effects of chemotherapy on dental status in children treated for nephroblastoma

Dental abnormalities among children treated at a young age for Wilms tumor are reported. The authors retrospectively reviewed the dental records and panoramic radiographs of 27 children treated for nephroblastoma between 1994 and 1998. They evaluated the frequency of apparent microdontia, excessive caries, root stunting, hypodontia, and enamel hypoplasia and compared this group to a control group of 78 children. Seventy percent of the children developed dental abnormalities, comprising root stunting (44%), enamel hypoplasia (22%), microdontia (18%), and hypodontia (7%). Results of control subjects were significantly different regarding dental abnormalities, especially microdontia and taurodontia. These results indicate that chemotherapy in children may lead to troubles affecting teeth growing at the time of treatment. Information and prospective dental care are needed, and further investigations are required.

Disturbed root development of permanent teeth after pediatric stem cell transplantation. Dental root development after SCT

BACKGROUND

Deficient dental root development has been reported after conventional pediatric anticancer therapy, but less information is available on stem cell transplantation (SCT) recipients.

METHODS

Root-crown (R/C) ratios of fully developed permanent teeth were assessed from panoramic radiographs of 52 SCT recipients, who were treated when they were age < 10 years. Using standard deviation scores (SDSs), the authors compared the R/C ratios to the corresponding tooth and gender-specific values in a healthy population. The percentage of affected R/C ratios per individual was examined in a subgroup of 39 (SG39) patients with advanced tooth development. The effects of total body irradiation (TBI) and SCT age on the R/C ratios were studied in TBI and high-dose chemotherapy (HDC = non-TBI) groups and in 3 age groups (< or = 3.0 years, 3.1-5.0 years, > or = 5.1 years).

RESULTS

Per individual, 77% of the fully developed permanent teeth were affected in SG39. At the tooth level, in 77% of the 945 teeth studied (52 patients), the R/C ratios were outside +/-2 SDSs. More teeth were affected in the TBI (85%) than in the non-TBI (55%) group (P < 0.001). The teeth of the patients who were ages 3.1-5.0 years old at SCT presented with the most severe aberrations of the R/C ratio (mean SDS = -4.4) whereas the teeth of the youngest (age < or = 3.0 years) and the oldest (age > or = 5.1 years) patients were equally affected (mean SDSs = -3.1 and -3.0, respectively).

CONCLUSIONS

Disturbances of dental root growth always followed pediatric SCT. HDC alone intensely harmed root growth but TBI further increased the adverse effects that were most extensive in the patients 3.1-5.0 years at SCT. These sequelae should be taken into account during the lifelong dental follow-up to minimize the clinical consequences of dental injuries.

Long-term effects of cancer therapy on dental development: a case report

As the prognosis of malignant conditions in children improve by cancer therapy, long-term side effects due to antineoplastic treatment may be encountered. This case report demonstrates the long-term alterations on dental development in patient who had been treated for malignant condition. Alterations were observed during radiographic control 8 years after the therapy and included short, blunted, tapered and V-shaped root malformations as well as delayed and ectopic eruptions.

Maturogenesis: is it a new concept?

The treatment of an undeveloped (immature) tooth with a carious exposure has been reported extensively in the literature. The main objective of treatment is to provide vital pulp therapy to allow continued development of root dentin in the hope that the root will attain full maturity. A case report is presented that illustrates root development (maturogenesis), not just closure of the apex (apexogenesis). A direct pulp cap was performed after a carious pulp exposure using calcium hydroxide with iodoform paste. The crown was restored with a glass ionomer/composite resin cement.

Long-term effects of chemotherapy on orodental structures in children with non-Hodgkin's lymphoma

The aim of this study was to investigate the late effects of treatment for childhood non-Hodgkin's lymphomas (NHL) on oral health and dental development. Thirty-six long-term survivors that had been treated with chemotherapy of childhood NHL were included in this study and 36 volunteers with similar age and sex distribution served as controls. Both groups underwent a complete orodental examination for decayed, missing and filled teeth and surfaces, gingival and periodontal health according to the Loe-Silness Gingival Index and Sillnes-Loe Plaque Index, enamel defects and discolorations, root malformations, eruption status, agenesis, premature apexifications and microdontia. The severity of these disturbances related to age at the time of NHL diagnosis were also evaluated by creating two groups as < 5 yr and > 5 yr. Although none of the parameters altered with age, patients had significantly higher plaque index, more enamel discolorations and root malformations than did the controls. The results show that long-term survivors of NHL patients exhibit some orodental disturbances that may be attributed to the chemotherapy regimens.

Fgf-2 regulates enamel and dentine formation in mouse tooth germ

We examined the effects of basic fibroblast growth factor (FGF-2) on cultured lower molar tooth germ at the differentiative (bell) stage. Although FGF-2 has been detected in odontogenesis, its roles in biological activities, such as cell proliferation, differentiation and extracellular matrix mineralization are unclear. We assayed mRNA levels of the differentiation markers, dentine sialophosphoprotein (DSPP), amelogenin and alkaline phosphatase (ALP) using reverse transcription-polymerase chain reaction (RT-PCR), and histological methods. Tooth germs dissected from 17-day-old embryonic mice were cultured for 4 days with either recombinant human FGF-2 or specific antisense phosphorothioate oligodeoxynucleotide (antisense ODN) for FGF-2. Exogenous FGF-2 decreased the gene expression of differentiation markers in molars at the bell stage. Abrogation of endogenous FGF-2 by antisense ODN increased the gene expression of differentiation markers, and also significantly enhanced enamel and dentine formation. This histological change was recovered by adding exogeneous FGF-2. These findings suggest that FGF-2 at the bell stage regulates cell differentiation and matrix secretion.

[Effects of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) on the formation of dental hard tissue of mouse molar tooth germs in organ culture system]

In the developing tooth, 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) causes hypoplasia and hypomineralization of enamel and dentine. The present study was undertaken to clarify the effects of HEBP on the formation of dental tissues of tooth germs in an organ culture system. Mandibular first molars from 17.5-day-old mouse embryos were cultured with or without 250 microM HEBP in culture medium. Cultured tooth germs were analyzed by histological examination and by immunohistochemical localization using anti-amelogenin antibody. In cultured tooth germs treated with HEBP before the commencement of calcification in dentine, calcification of dentine matrix was inhibited completely and enamel formation was not observed. Ameloblasts were directly adjacent to dentine matrix. However, immunohistochemical data indicated that these ameloblasts secreted amelogenin. In the experiments of adding HEBP to cultured tooth germs on culture day 13, calcified dentine and enamel had formed before the administration of HEBP, but the dentine matrix newly formed after the administration of HEBP had not calcified. It was confirmed by immunohistochemical observations that enamel matrix-like material had penetrated into uncalcified dentine matrix and accumulated in dental papilla of tooth germs. However, no enamel matrix-like material was observed in calcified dentine and predentine underneath the calcified dentine by immunohistochemical staining. From these results, it might be concluded that ameloblasts secreted enamel matrix in the presence of HEBP and diffused through uncalcified dentine matrix into dental papilla. These findings suggests the calcification of dentine might be essential for the physical barrier to accumulate the enamel matrix and form a distinct layer of enamel as enamel.

Dental abnormalities in children after chemotherapy treatment for acute lymphoid leukemia

The frequency of dental abnormalities, such as delayed dental development, microdontia, hypoplasia, agenesis, V-shaped root and shortened root was evaluated in 76 acute lymphoblastic leukemia (ALL) pediatric patients who had been off chemotherapy for 6 months. These children had been subjected to one of the three Brazilian Protocols or the BFM86 Protocol. The patients were divided into three groups: Group I (GI; high risk) treated with one of the three Brazilian Protocols who received high-dose chemotherapy, intensive maintenance and cranial radiotherapy; Group II (GII; low risk) who were also treated with one of the three Brazilian Protocols using low-intensive chemotherapy with no radiotherapy; and Group III (GIII) based on the BFM86 Protocol. Of 76 children, 13 showed no dental abnormalities (8 were at the age of tooth formation). The remaining 63 children (82.9%) showed at least one dental anomaly. The abnormalities were probably caused by the type, intensity, frequency of the treatment and age of the patients at ALL diagnosis and this might have important consequences for the children's dental development.

Effects of a Macrolide Antibiotic on Enamel Formation in Rat Incisors-Primary Lesion of Ameloblast at the Transition Stage

A novel macrolide antibiotic was administered orally to 5-week-old Jcl:Wistar rats at a dose of 5,000 mg/kg/day for 5 weeks, and then a half of animals were maintained without any treatment for 10 weeks. A white discolored lesion with horizontal stripes developed on the surface of the upper and lower incisors after dosing for 4 weeks, and these macroscopical incisal lesions disappeared with the eruption in 4 weeks after stop of administration. Histopathologically, increase in number of karyopycnosis of ameloblast at the transitional stage, vacuolar degeneration of ameloblast and cystic change in the maturation stage, and impaired iron pigment secretion at the pigmentation stage were observed. Microradiography, calcio-traumatic zones, which means hypocalcification, were observed on the superficial layer of enamel. These results suggest that the primary lesion induced by a novel macrolide antibiotic is the increased karyopycnosis of ameloblast at the transitional stage, and followed by later stage.