Je Seon Song

The Prevalence and Morphologic Classification of Distolingual Roots in the Mandibular Molars in a Korean Population

INTRODUCTION The aims of this study were to determine the incidence and concurrency rate of distolingual (DL) roots on mandibular molars and to classify them according to their morphologic features. METHODS Serial cross-sectional computed tomography images of the mandibles were collected retrospectively from 1,775 Korean patients of Mongoloid origin. The incidence of DL roots was calculated for each molar, and their patterns of concurrence were analyzed with the Fisher exact test. DL roots were categorized into five groups according to their morphologic characteristics using the three-dimensional reconstructed images. RESULTS The incidence rate of DL roots was highest for first molars (24.5%) and lowest for second molars (0.7%). They were often present concurrently in adjacent molars (p < 0.004). The morphologic characteristics of DL roots in the first molars varied greatly from a severely curved type (type III, 40.5%) to an underdeveloped small type or a conical type (2.5% and 1.4%, respectively). CONCLUSION Data regarding the pattern of occurrence and the morphologic features of DL roots can provide useful information to clinicians, leading to higher rate of success of endodontic treatment.

Incidence and relationship of an additional root in the mandibular first permanent molar and primary molars

OBJECTIVES The mandibular first permanent and primary molars occasionally have an additional root located distolingually. This study aimed to determine the incidences of an additional root in these molars and their relationship. STUDY DESIGN This study involved 4050 children for whom periapical radiographs of the mandibular molar area were available. The incidence of an additional root for each molar was calculated and the pattern of concurrent additional roots in different molars was also investigated. RESULTS Additional roots were present in 33.1%, 27.8%, and 9.7% of the first permanent, second primary, and first primary molars, respectively. When an additional root was present in a primary molar, the probability of the posterior adjacent molar also having an additional root was greater than 94.3%. CONCLUSION The presence of an additional root in a primary molar can be used to predict the presence of an additional root in molars posterior to it.

Color Changes of Teeth after Treatment with Various Mineral Trioxide Aggregate–based Materials: An Ex Vivo Study

INTRODUCTION Mineral trioxide aggregate (MTA) materials have been used for many years as a pulp therapy material. The most widely used product, ProRoot MTA (Dentsply, Tulsa, OK), has a major drawback in that it causes tooth discoloration. Alternatives have recently been developed such as ENDOCEM Zr (MARUCHI, Wonju, Korea) and RetroMTA (BioMTA, Seoul, Korea). The purpose of this study was to compare the discoloration of these various MTA-based materials. METHODS Discoloration of discs prepared from 4 different MTA-based materials (ProRoot MTA, MTA Angelus [Angelus, Londrina, PR, Brazil], ENDOCEM Zr, and RetroMTA) were observed at 15 and 30 minutes after exposure to light at an intensity of 1000 mA/cm(2). In a tooth model, 12 premolars were used per each group to retrofill the pulp chamber with MTA-based materials. The degree of discoloration was measured over a 16-week period using a digital spectrophotometer. RESULTS Distinct color changes were observed for discs made from ProRoot MTA and MTA Angelus, but no clear change was observed for those made from either ENDOCEM Zr or RetroMTA. In the tooth model, more distinct, time-dependent color changes were observed for teeth filled with ProRoot MTA and MTA Angelus than for those filled with ENDOCEM Zr and RetroMTA. CONCLUSIONS Less discoloration was observed with ENDOCEM Zr and RetroMTA (which contain zirconium oxide) than with ProRoot MTA and MTA Angelus (which contain bismuth oxide) in both of the test models used.

The effect of epigallocatechin-3-gallate (EGCG) on human alveolar bone cells both in vitro and in vivo

OBJECTIVE The effects of epigallocatechin-3-gallate (EGCG), a major catechin in green tea, on human and mouse osteoblasts remain controversial. This study investigated the direct effects of EGCG on human alveolar bone-derived cells (hABCs) both in vitro and in vivo. DESIGN hABCs which were collected from eight children (aged 7-9 years, seven males and one female) were treated with EGCG at various concentrations (1, 5, 10, 25, and 50μM), and a proliferation assay, flow cytometric analysis for apoptosis evaluation, migration assay, and in vitro osteogenic differentiation were performed. hABCs that were pretreated with 10μM EGCG and mixed with calcium phosphate carrier combined with EGCG (0.1, 0.5, or 1.5mg) in vivo were transplanted into immunodeficient mouse. Histological staining, quantitative gene expressions, and alkaline phosphatase activity were evaluated in the retrieved transplants. RESULTS The proliferation and migration were decreased when EGCG was present at over 25μM. The osteogenic differentiation increased slightly when EGCG was present at up to 10μM, and clearly decreased for higher concentrations of EGCG. In vivo, the potential for hard-tissue formation was slightly higher for the group with 0.1mg of EGCG than for the control group, and decreased sharply for higher concentrations of EGCG. CONCLUSION The present observations suggest that EGCG at a low concentration can slightly enhance the osteogenic effect in vivo, whereas at a higher concentration it can prevent the osteogenic differentiation of hABCs both in vitro and in vivo.

Comparative Study of Pulpal Responses to Pulpotomy with ProRoot MTA, RetroMTA, and TheraCal in Dogs' Teeth

INTRODUCTION This study was conducted to evaluate and compare pulpal responses to ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK), RetroMTA (Meta Biomed Co, Ltd, Seoul, Korea), and TheraCal (Bisco Inc, Schamburg, IL) in dog partial pulpotomy models. METHODS Partial pulpotomies were performed on 60 beagle teeth. The exposed pulp tissues were randomly capped with either ProRoot MTA (n = 15), RetroMTA (n = 15), TheraCal (n = 15), or interim restorative material as a negative control (n = 15). After 4 weeks, the teeth were extracted and processed for histologic and immunohistochemical examinations using osteocalcin and dentin sialoprotein. Calcific barrier formation, inflammatory reaction, and the odontoblastic layer were evaluated and scored in a blind manner. The areas of newly formed calcific barriers were measured for each group. RESULTS In most of the ProRoot MTA and RetroMTA specimens, continuous calcific barriers were formed, and the pulps contained palisading patterns in the odontoblastic layer that were free of inflammation. However, the TheraCal specimens had lower quality calcific barrier formation, extensive inflammation, and less favorable odontoblastic layer formation. Overall, areas of newly formed calcific barrier were higher in the ProRoot MTA and RetroMTA specimens than in the TheraCal specimens. Also, immunohistochemistry revealed that osteocalcin and dentin sialoprotein were more clearly visible in the ProRoot MTA and RetroMTA specimens than in the TheraCal specimens. CONCLUSIONS RetroMTA could provide an alternative to ProRoot MTA. Both materials produced favorable pulpal responses that were similar in nature, whereas TheraCal produced less favorable pulpal responses.

In vitro and in vivo characteristics of stem cells from human exfoliated deciduous teeth obtained by enzymatic disaggregation and outgrowth

OBJECTIVE Stem cells from human exfoliated deciduous teeth (SHED) are a good source of dental tissue for regeneration therapy, and can be obtained using different primary culture methods. The aim of this study was to determine the differences in the in vitro and in vivo characteristics between SHED isolated via enzymatic disaggregation (e-SHED) and outgrowth (o-SHED) primary culture methods. DESIGN Dental pulp stem cells were isolated from 14 exfoliated deciduous teeth by enzymatic disaggregation (n=7) and outgrowth (n=7). Their proliferation potential and colony-forming ability were evaluated in vitro, as was their mesenchymal stem-cell-marker expression (using flow cytometry), and their differentiation was verified using quantitative real-time PCR (qPCR) and histochemical staining. In addition, the qualitative and quantitative characteristics of the hard tissue that was generated after in vivo transplantation were compared using haematoxylin and eosin staining, immunohistochemical staining, qPCR, and quantitative alkaline phosphatase analysis. RESULTS The cell-proliferation potential, colony-forming ability, and Stro-1 and CD146 expression were higher in e-SHED than in o-SHED. While the in vitro adipogenic differentiation potential was greater in e-SHED than in o-SHED, the in vitro osteogenic differentiation did not differ significantly between the two cell types. Although in vivo hard tissue formation was greater following transplantation of o-SHED into mice, there was no difference in the quality of hard tissue generated by e-SHED and o-SHED. CONCLUSION The findings of this study indicate that e-SHED exhibit stronger stemness characteristics, but that o-SHED are more suitable for hard-tissue regeneration therapy in teeth.

Comparative gene expression analysis of the human periodontal ligament in deciduous and permanent teeth.

There are histological and functional differences between human deciduous and permanent periodontal ligament (PDL) tissues. The aim of this study was to determine the differences between these two types of tissue at the molecular level by comparing their gene expression patterns. PDL samples were obtained from permanent premolars (n = 38) and anterior deciduous teeth (n = 31) extracted from 40 healthy persons. Comparative cDNA microarray analysis revealed several differences in gene expression between the deciduous and permanent PDL tissues. These findings were verified by qRT-PCR (quantitative reverse-transcription–polymerase chain reaction) analysis, and the areas where genes are expressed were revealed by immunohistochemical staining. The expressions of 21 genes were up-regulated in deciduous relative to PDL tissues, and those of 30 genes were up-regulated in permanent relative to deciduous PDL tissues. The genes that were up-regulated in deciduous PDL tissues were those involved in the formation of the extracellular matrix (LAMC2, LAMB3, and COMP), tissue development (IGF2BP, MAB21L2, and PAX3), and inflammatory or immune reactions leading to tissue degradation (IL1A, CCL21, and CCL18). The up-regulated genes in permanent PDL tissues were related to tissue degradation (IL6 and ADAMTS18), myocontraction (PDE3B, CASQ2, and MYH10), and neurological responses (FOS, NCAM2, SYT1, SLC22A3, DOCK3, LRRTM1, LRRTM3, PRSS12, and ARPP21). The analysis of differential gene expressions between deciduous and permanent PDL tissues aids our understanding of histological and functional differences between them at the molecular level.

Comparative Gene-Expression Analysis of the Dental Follicle and Periodontal Ligament in Humans

The human dental follicle partially differentiates into the periodontal ligament (PDL), but their biological functions are different. The gene-expression profiles of the dental follicle and PDL were compared using the cDNA microarray technique. Microarray analysis identified 490 genes with a twofold or greater difference in expression, 365 and 125 of which were more abundant in the dental follicle and PDL, respectively. The most strongly expressed genes in the dental follicle were those related to bone development and remodeling (EGFL6, MMP8, FRZB, and NELL1), apoptosis and chemotaxis (Nox4, CXCL13, and CCL2), and tooth and embryo development (WNT2, PAX3, FGF7, AMBN, AMTN, and SLC4A4), while in the PDL it was the tumor-suppressor gene WIF1. Genes related to bone development and remodeling (STMN2, IBSP, BMP8A, BGLAP, ACP5, OPN, BMP3, and TM7SF4) and wound healing (IL1, IL8, MMP3, and MMP9) were also more strongly expressed in the PDL than in the dental follicle. In selected genes, a comparison among cDNA microarray, real-time reverse-transcription polymerase chain reaction, and immunohistochemical staining confirmed similar relative gene expressions. The gene-expression profiles presented here identify candidate genes that may enable differentiation between the dental follicle and PDL.

A new type of dental anomaly: molar-incisor malformation (MIM)

A molar-incisor malformation (MIM) is a newly discovered type of dental anomaly of the permanent first molars, deciduous second molars, and permanent maxillary central incisors. MIM anomalies of the permanent first molars and deciduous second molars may include normal crowns with a constricted cervical region and thin, narrow, and short roots, whereas the affected maxillary central incisors may exhibit a hypoplastic enamel notch near the cervical third of the clinical crown. Although the etiology of MIM remains to be determined, it is thought to be attributable to an epigenetic factor linked to brain- and central nervous system-related systemic diseases at around age 1 to 2 years. MIM teeth are associated with clinical problems such as impaction, early exfoliation, space loss, spontaneous pain, periapical abscess, and poor incisor esthetics. Children with MIM teeth should be observed closely with respect to their medical history, and dentists should formulate a wider-ranging treatment plan.

Decellularized Human Dental Pulp as a Scaffold for Regenerative Endodontics

Teeth undergo postnatal organogenesis relatively late in life and only complete full maturation a few years after the crown first erupts in the oral cavity. At this stage, development can be arrested if the tooth organ is damaged by either trauma or caries. Regenerative endodontic procedures (REPs) are a treatment alternative to conventional root canal treatment for immature teeth. These procedures rely on the transfer of apically positioned stem cells, including stem cells of the apical papilla (SCAP), into the root canal system. Although clinical success has been reported for these procedures, the predictability of expected outcomes and the organization of the newly formed tissues are affected by the lack of an available suitable scaffold that mimics the complexity of the dental pulp extracellular matrix (ECM). In this study, we evaluated 3 methods of decellularization of human dental pulp to be used as a potential autograft scaffold. Tooth slices of human healthy extracted third molars were decellularized by 3 different methods. One of the methods generated the maximum observed decellularization with minimal impact on the ECM composition and organization. Furthermore, recellularization of the scaffold supported the proliferation of SCAP throughout the scaffold with differentiation into odontoblast-like cells near the dentinal walls. Thus, this study reports that human dental pulp from healthy extracted teeth can be successfully decellularized, and the resulting scaffold supports the proliferation and differentiation of SCAP. The future application of this form of an autograft in REPs can fulfill a yet unmet need for a suitable scaffold, potentially improving clinical outcomes and ultimately promoting the survival and function of teeth with otherwise poor prognosis.