Yin-Lin Wang

Retrospective survey of biopsied oral lesions in pediatric patients.

BACKGROUND/PURPOSE Although the general profile of oral biopsies from Asian children has been reported, it was still worth examining whether there were racial and geographic variations in the categories and incidence of pediatric oral lesions. This retrospective study mainly evaluated the categories and incidence of biopsied oral lesions in Taiwanese pediatric patients. METHODS Biopsy records of all oral lesions from pediatric patients, aged 0-14 years, in the files of the Department of Pathology, National Taiwan University Hospital from 1988 to 2007 were evaluated. The patients were divided into three age groups (0-5, 6-10, and 11-14 years), and the oral lesions were classified into four main categories: inflammatory and reactive, cystic, neoplastic, and other lesions. RESULTS Of a total of 11,986 biopsied oral lesions, 797 (6.6%) were found in pediatric patients. The most common oral lesions were inflammatory and reactive (45.5%), followed by neoplastic (23.5%), cystic (22.2%), and other (8.8%) lesions. The majority of oral biopsies (47.3%) were taken from patients in the 11-14 years age group. Of the 187 oral neoplastic lesions, 178 (95%) were benign and nine (5%) were malignant, including two premalignant lesions. The maxilla (66 cases) and the mandible (61 cases) were the two most common sites for pediatric neoplastic lesions. The top five oral lesions in pediatric patients were mucous extravasation phenomenon (195 cases), dentigerous cyst (84 cases), odontoma (83 cases), radicular cyst (38 cases), and dental follicle (26 cases). CONCLUSION The mucous extravasation phenomenon, odontoma, or dentigerous cyst was the most common inflammatory and reactive, neoplastic, or cystic lesion, respectively, in pediatric patients. The relatively high incidence of inflammatory and reactive lesions in pediatric patients implies the importance of stringent oral hygiene in children. Most oral neoplastic lesions in pediatric patients are benign, and malignant oral tumors rarely occur in pediatric patients.

Effect of triethylene glycol dimethacrylate on the cytotoxicity, cyclooxygenase-2 expression and prostanoids production in human dental pulp cells

AIM To evaluate the effect of TEGDMA on cell cycle progression as well as alterations of cell cycle-related gene and protein expression. METHODOLOGY Human dental pulp cells were exposed to 0-5 mmol L(-1) TEGDMA for 24 h. Cytotoxicity was evaluated by 3-(4, 5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay. Cell cycle progression was analysed by propidium iodide (PI) flow cytometry. Cell death pathway was surveyed by annexin V/PI dual-staining flow cytometry. The mRNA expression of cell cycle-related genes (cdc2, cyclinB1 and p21) and COX-2 was evaluated by reverse transcriptase-polymerase chain reaction, and their protein expression was evaluated by Western blotting. The production of PGE(2) and PGF(2α) in the culture medium was determined by enzyme-linked immunosorbent assay. RESULTS Triethylene glycol dimethacrylate inhibited cellular growth and induced cell cycle deregulation in dental pulp cells. High-dose exposure provoked both necrotic and apoptotic cell death. The gene and protein expression of cdc2, cyclin B1 and cdc25C declined obviously whilst cells treated with 2.5 mmol L(-1) TEGDMA concurrent with the elevated expression of p21. The mRNA and protein expression of COX-2, along with production of PGE(2) and PGF(2α), are drastically raised by 2.5-5 mmol L(-1) TEGDMA. CONCLUSIONS Triethylene glycol dimethacrylate induced cytotoxicity, cell cycle arrest and apoptosis in dental pulp cells, which was associated with the decline of cdc2, cyclin B1, cdc25C expression and elevation of p21 expression. Concomitantly, COX-2 expression, PGE(2) and PGF(2α) production increased. These effects may contribute to explain the pulpal damage and inflammation induced by TEGDMA after operative procedures.

Application of Ni-Ti Rotary Files for Pulpectomy in Primary Molars

Nickel-titanium (Ni-Ti) instruments are widely used in adult endodontics as an efficient technique, but are rarely used for endodontic treatment for primary molars. To explore the feasibility of using Ni-Ti rotary instruments for root canal preparation in primary molars, 51 primary molars with intact root apex in 22 children, who ranged in age from 3.2 years to 7.7 years, were treated. A modified protocol for ProTaper(superscript ®) Ni-Ti rotary files using only two instruments (SX and S2) was used for root canal preparation, and canals were filled with a calcium hydroxide-iodoform paste. All teeth were restored with stainless steel crowns. Postoperative radiographs were taken immediately following treatment and at 3-month intervals. Success or failure was assessed based on clinical and radiographic criteria. We found that the success rate of endodontic treatment for primary molars using Ni-Ti instrument for root canal preparation was 95% at the 12-month recall examination. We conclude that with the modified protocol, ProTaper(superscript ®) Ni-Ti rotary files can be safely and efficiently applied for root canal preparation in primary molars.

Urethane dimethacrylate induces cytotoxicity and regulates cyclooxygenase-2, hemeoxygenase and carboxylesterase expression in human dental pulp cells

The toxic effect of urethane dimethacrylate (UDMA), a major dental resin monomer, on human dental pulp is not fully clear. In this study, we investigated the influence of UDMA on the cytotoxicity, cell cycle distribution, apoptosis and related gene expression of dental pulp cells. The role of reactive oxygen species, hemeoxygenase-1 (HO-1) and carboxylesterase (CES) in UDMA cytotoxicity, was evaluated. UDMA induced morphological changes of pulp cells and decreased cell viability by 29-49% at concentrations of 0.1-0.35 mM. UDMA induced G0/G1, G2/M cell cycle arrest and apoptosis. The expression of cdc2, cyclinB1 and cdc25C was inhibited by UDMA. Moreover, UDMA stimulated COX-2, HO-1 and CES2 mRNA expression of pulp cells. The cytotoxicity of UDMA was attenuated by N-acetyl-l-cysteine, catalase and esterase, but was enhanced by Zn-protoporphyrin (HO-1 inhibitor), BNPP (CES inhibitor) and loperamide (CES2 inhibitor). Exposure of UDMA may potentially induce the inflammation and toxicity of dental pulp. These findings are important for understanding the clinical response of human pulp to resin monomers after operative restoration and pulp capping, and also provide clues for improvement of dental materials.

Role of ALK5/Smad2/3 and MEK1/ERK Signaling in Transforming Growth Factor Beta 1–modulated Growth, Collagen Turnover, and Differentiation of Stem Cells from Apical Papilla of Human Tooth

INTRODUCTION Transforming growth factor β1 (TGF-β1) plays an important role in cell proliferation, matrix formation, and odontogenesis. This study investigated the effects of TGF-β1 on stem cells from apical papilla (SCAPs) and its signaling by MEK/ERK and Smad2. METHODS SCAPs were exposed to TGF-β1 with/without pretreatment and coincubation by SB431542 (an ALK5/Smad 2/3 inhibitor) or U0126 (a MEK/ERK inhibitor). Cell growth was examined by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide assay or direct counting of viable cells. Collagen content was determined by using the Sircol collagen assay (Biocolor Ltd, Newtownabbey, Northern Ireland). Cell differentiation was evaluated by measuring alkaline phosphatase (ALP) activity. Smad2 and ERK1/2 phosphorylation was analyzed by Western blotting or PathScan phospho-enzyme-linked immunosorbent assay (Cell Signaling Technology Inc, Danvers, MA). RESULTS TGF-β1 stimulated the growth and collagen content of cultured SCAPs. TGF-β1 stimulated ERK1/2 and Smad2 phosphorylation within 60 minutes of exposure. Pretreatment by U0126 and SB431542 effectively prevented the TGF-β1-induced cell growth and collagen content in SCAPs. TGF-β1 stimulated ALP activity at lower concentrations (0.1-1 ng/mL) but down-regulated ALP at higher concentrations (>5 ng/mL). U0126 prevented 0.5 ng/mL TGF-β1-induced ALP activity but showed little effect on 10 ng/mL TGF-β1-induced decline of ALP in SCAPs. Interestingly, SB431542 attenuated both the stimulatory and inhibitory effects on ALP by TGF-β1. CONCLUSIONS TGF-β1 may affect the proliferation, collagen turnover, and differentiation of SCAPs via differential activation of ALK5/Smad2 and MEK/ERK signaling. These results highlight the future use of TGF-β1 and SCAP for engineering of pulpal regeneration and apexogenesis.

A novel chitosan-γPGA polyelectrolyte complex hydrogel promotes early new bone formation in the alveolar socket following tooth extraction.

A novel chitosan-γPGA polyelectrolyte complex hydrogel (C-PGA) has been developed and proven to be an effective dressing for wound healing. The purpose of this study was to evaluate if C-PGA could promote new bone formation in the alveolar socket following tooth extraction. An animal model was proposed using radiography and histomorphology simultaneously to analyze the symmetrical sections of Wistar rats. The upper incisors of Wistar rats were extracted and the extraction sockets were randomly treated with gelatin sponge, neat chitosan, C-PGA, or received no treatment. The extraction sockets of selected rats from each group were evaluated at 1, 2, 4, or 6 wk post-extraction. The results of radiography and histopathology indicated that the extraction sockets treated with C-PGA exhibited lamellar bone formation (6.5%) as early as 2 wk after the extraction was performed. Moreover, the degree of new bone formation was significantly higher (P < 0.05) in the extraction sockets treated with C-PGA at 6 wk post-extraction than that in the other study groups. In this study, we demonstrated that the proposed animal model involving symmetrical sections and simultaneous radiography and histomorphology evaluation is feasible. We also conclude that the novel C-PGA has great potential for new bone formation in the alveolar socket following tooth extraction.

Dental Anomalies in Two Patients with Incontinentia Pigmenti

Incontinentia pigmenti (IP) is a rare X-linked dominant inherited disorder which has a variety of ectodermal aberrations. Skin hyperpigmentation is the most characteristic feature of IP. However, extracutaneous anomalies involving dentition, hair, eyes, and central nervous system are also found. The dental anomalies reported include peg-shaped or malformed teeth, hypodontia, delayed eruption, and impacted tooth. This report describes the dental anomalies in 2 IP patients who had the characteristic features of skin hyperpigmentation. One was a 13-year-old girl who had slender cone-shaped permanent anterior teeth, hypodontia, and delayed eruption of teeth which are characteristic dental anomalies in an IP patient. The other was a 10-year-old girl who only had 2 tulip-shaped maxillary permanent central incisors with shorter tapering roots but no congenital missing teeth or delayed eruption of teeth. Our findings suggest that IP may present a broad variation of dental anomalies individually. However, the characteristic finding of permanent anterior teeth with a longer crown and a shorter root found in both of our IP patients may be worthy of consideration in the differential diagnosis of IP.

Erosive potential of soft drinks on human enamel: An in vitro study

BACKGROUND/PURPOSE Most soft drinks are acidic in nature. Regular consumption of these drinks may result in dental erosion. The aim of this in vitro study was to evaluate the erosive potential of different soft drinks in Taiwan by a novel multiple erosive method. METHODS Four commercially available soft drinks in Taiwan were selected for this study. The properties of each product were analyzed to measure their pH, titratable acidity, and ion contents. The erosive potential of the soft drinks was measured based on the amount of loss of human enamel surface following its exposure to the soft drinks tested for different periods (20 minutes, 60 minutes, and 180 minutes). The enamel loss was measured using a confocal laser scanning microscope. RESULTS The pH values of the soft drinks were below the critical pH value (5.5) for enamel demineralization, and ranged from 2.42 to 3.46. The drink with ingredients of citric acid and ascorbic acid had the highest titratable acidity (33.96 mmol OH(-)/L to pH 5.5 and 71.9 mmol OH(-)/L to pH 7). Exposure to all the soft drinks resulted in loss of human enamel surface (7.28-34.07 μm for 180-minute exposure). The beverage with the highest calcium content had the lowest erosive potential. CONCLUSION All tested soft drinks were found to be erosive. Soft drinks with high calcium contents have significantly lower erosive potential. Low pH value and high citrate content may cause more surface enamel loss. As the erosive time increased, the titratable acidity to pH 7 may be a predictor of the erosive potential for acidic soft drinks. The erosive potential of the soft drinks may be predicted based on the types of acid content, pH value, titratable acidity, and ion concentration.

Areca Nut Components Affect COX-2, Cyclin B1/cdc25C and Keratin Expression, PGE2 Production in Keratinocyte Is Related to Reactive Oxygen Species, CYP1A1, Src, EGFR and Ras Signaling

Aims Chewing of betel quid (BQ) increases the risk of oral cancer and oral submucous fibrosis (OSF), possibly by BQ-induced toxicity and induction of inflammatory response in oral mucosa. Methods Primary gingival keratinocytes (GK cells) were exposed to areca nut (AN) components with/without inhibitors. Cytotoxicity was measured by 3-(4,5-dimethyl- thiazol- 2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. mRNA and protein expression was evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR) and western blotting. PGE2/PGF2α production was measured by enzyme-linked immunosorbent assays. Results Areca nut extract (ANE) stimulated PGE2/PGF2α production, and upregulated the expression of cyclooxygenase-2 (COX-2), cytochrome P450 1A1 (CYP1A1) and hemeoxygenase-1 (HO-1), but inhibited expression of keratin 5/14, cyclinB1 and cdc25C in GK cells. ANE also activated epidermal growth factor receptor (EGFR), Src and Ras signaling pathways. ANE-induced COX-2, keratin 5, keratin 14 and cdc25C expression as well as PGE2 production were differentially regulated by α–naphthoflavone (a CYP 1A1/1A2 inhibitor), PD153035 (EGFR inhibitor), pp2 (Src inhibitor), and manumycin A (a Ras inhibitor). ANE-induced PGE2 production was suppressed by piper betle leaf (PBL) extract and hydroxychavicol (two major BQ components), dicoumarol (a NAD(P)H:Quinone Oxidoreductase - NQO1 inhibitor) and curcumin. ANE-induced cytotoxicity was inhibited by catalase and enhanced by dicoumarol, suggesting that AN components may contribute to the pathogenesis of OSF and oral cancer via induction of aberrant differentiation, cytotoxicity, COX-2 expression, and PGE2/PGF2αproduction. Conclusions CYP4501A1, reactive oxygen species (ROS), EGFR, Src and Ras signaling pathways could all play a role in ANE-induced pathogenesis of oral cancer. Addition of PBL into BQ and curcumin consumption could inhibit the ANE-induced inflammatory response.

Nanocrystalline calcium sulfate/hydroxyapatite biphasic compound as a TGF-β1/VEGF reservoir for vital pulp therapy

OBJECTIVES Vital pulp therapy aims to treat reversible pulpal injuries via protective dentinogenesis and to preserve more tooth structure. Mineral trioxide aggregate (MTA)-based capping materials demonstrate prolonged setting time increases the risk of pulpal infection during multi-visit treatment. Their non-degradable property occupies pulp space and limits dentin-pulp regeneration. This study reports an inorganic degradable biomaterial that presents a short initial setting time and acts as a growth factor reservoir to promote reparative dentinogenesis. METHODS We synthesize nanocrystalline calcium sulfate hemihydrate (nCS), hydroxyapatite (HAp) and calcium sulfate hemihydrate (CS) as a reservoir to which transforming growth factor-beta 1 (TGF-β1) and vascular endothelial growth factor (VEGF) are added (denoted as nCS/HAp/CS/TGF-β1/VEGF). In vitro biocompatibility and mineralization (the activity and expression of alkaline phosphatase, ALP) were evaluated. Rat animal model was created to test in vivo efficacy. RESULTS Cultured human dental pulp cells (HDPCs) showed that nCS/HAp/CS/TGF-β1/VEGF cement has excellent biocompatibility and the potential to elevate the activity and expression of ALP. The in vivo efficacy (rat animal model) indicates protective dentin by micro-computed tomography (μ-CT) measurements and histological analyses. The 3D μ-CT non-destructive analysis also determines volume changes during pulpotomy, suggesting that the degraded space of the nCS/HAp/CS/TGF-β1/VEGF cement is repaired by the formation of dentin-pulp tissue. SIGNIFICANCE These findings demonstrate that nCS/HAp/CS cement acts as a potent reservoir for the sustained release of growth factors, and that nCS/HAp/CS/TGF-β1/VEGF cement has a high potential to form the reparative dentinogenesis in vivo.