Guay-Fen Huang

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.

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.

Cyclosporine A induces connective tissue growth factor expression in human gingival fibroblasts: suppression by epigallocatechin-3-gallate.

BACKGROUND/PURPOSE Transforming growth factor-β (TGF-β) plays an important role in the pathogenesis of cyclosporine A (CsA)-induced gingival overgrowth (GO). Connective tissue growth factor (CTGF/CCN2) acts as a cofactor with TGF-β to induce the maximal profibrotic effects of TGF-β. We investigated the effects of CsA on CCN2 expression in human gingival fibroblasts (HGFs) and the potential chemopreventive agent for CsA-induced GO. METHODS Western blot analyses were used to examine the signaling pathways of CsA-induced CCN2 expression in HGFs and whether epigallocatechin-3-gallate (EGCG), curcumin, or lovastatin can inhibit CsA-induced CCN2 expression. RESULTS CsA significantly stimulated CCN2 synthesis in HGFs. This effect can be inhibited by c-Jun NH(2)-terminal kinase (JNK) and Smad3 inhibitors but not by TGF-β neutralizing antibody and TGF-β type I receptor inhibitor. Furthermore, EGCG completely blocked CsA-induced CCN2 expression. CONCLUSION CsA-induced CCN2 protein expression is mediated through JNK and Smad signaling. CsA may contribute to the pathogenesis of GO through upregulation of CCN2 expression in HGFs. EGCG could be an adjuvant for the prevention of CsA-induced GO.

An in vitro study on restoring bond strength of a GIC to saliva contaminated enamel under unrinse condition.

OBJECTIVES This study attempted to find a method of restoring the tensile bond strength of glass ionomer cement (GIC) to saliva contaminated enamel under unrinse condition. METHODS One hundred and thirty human non-carious permanent teeth were divided into two major groups. Either treatment with air drying, acetone, polyacrylic acid, maleic acid, tartaric acid, Scotchbond primer or no treatment at all was applied to both clean and saliva contaminated enamel surfaces prior to GIC placement. Samples were debonded in tension after 7 days of storage in water using a universal testing machine. Statistical analysis was performed using one-way ANOVA, Tukeys studentized range test and Wilcoxons rank sums test to determine the significance of the difference of tensile bond strengths within and between the two major groups. RESULTS Bond strength of GIC to clean enamel was 2.46+/-0.79 MPa while the bond strength of GIC to wet contaminated enamel was significantly reduced to 1.28+/-0.32 MPa (p<0.01). However, the bond strengths were restored when the contaminated enamel surfaces were air-dried (2.19+/-0.38 MPa) or applied with either maleic acid (2.80+/-0.63 MPa) or Scotchbond primer (2.13+/-0.65 MPa) before placing GIC over the enamels. CONCLUSIONS Air drying, or application of maleic acid or Scotchbond primer to the contaminated enamel without rinsing prior to GIC placement can restore the tensile bond strength to a level similar to that of non-contaminated control.

Concomitant hypo-hyperdontia: A rare entity

Background/purpose Concomitant hypo-hyperdontia (CHH) is a rare numeric dental anomaly characterized by congenital missing teeth and supernumerary teeth occurring in the same individual. Due to its rarity and sporadicity, the causes of CHH have been completely unknown. Detailed characterization and presentation of more CHH cases not only strengthen clinical diagnosis and treatment for the patients but facilitate the search for etiological factors of the disorder. Materials and methods From a pedodontic patient population, 21 CHH subjects, with a mean age of 6 years 10 months, were identified and characterized. Dental records and radiographs were scrutinized and analyzed for the distribution and frequencies of involved teeth and concurrent dental anomalies. Through further literature review, 59 CHH cases with supernumeraries in the premaxillary region were retrieved for comparative analyses. Results The boys were affected twice as often as the girls. While most cases were unrelated and sporadic, two sisters and a pair of identical twins from two unrelated families were presented. Of all cases, only one was of syndromic CHH carrying Duchenne muscular dystrophy. Bimaxillay CHH, with anomalies involving two jaws, occurred more than 4 times as often as maxillary CHH. While all supernumeraries were found in premaxillary region, hypodontia frequently involved lateral incisors and premolars of both jaws. Conclusion As genetic contribution to CHH is strongly suggested by its familial occurrence and syndromic cases, environmental factors seem to play certain roles in modifying disease phenotypes. Judicious use of radiographs during early mixed dentition stage enhances clinical diagnosis and treatment of CHH.

Dental Treatment of Patients with Hemophilia A: A Case Report

Hemophilia A is a congenital bleeding disorder caused by deficiency of factor VIII. These patients may experience prolonged bleeding upon trauma or surgical procedures. This case is a 5-year-old boy with severe type of hemophilia A seeking for dental treatment. With pre-operative factor replacement, he received full-mouth dental treatment without any unexpected bleeding episode. After chair-side oral hygiene instruction and dietary counseling, he maintained fair oral hygiene and dental health during 3-month follow-ups. It is shown that with appropriate treatment planning, severe type hemophilic patients can safely receive dental treatment without unfavorable outcomes.

Management of a Traumatic Injured Immature Maxillary Incisor by Cvek Pulpotomy : A Case Report

Cvek pulpotomy is a conservative vital pulp therapy that consists of removing approximately 2 mm inflamed coronal pulp and placing biocompatible material over the underlying pulp tissue. This technique is suitable for treating traumatic injured immature teeth with pulp exposure. This case report presents a 9 year-old boy suffered from complicated crown fracture on tooth #11 two days ago and received Cvek pulpotomy with MTA dressing. Two mm of coronal pulp tissue from the exposure site was surgically removed, followed with normal saline irrigation and 2.5% NaOCl cotton pellets hemostais for 1 minute. Gray MTA was placed over the pulp stump, and GIC was then used for coronal seal. After 28 months follow-up, clinically no symptoms and signs were observed. Periapical x-ray revealed complete root formation, and electric pulp test (EPT) showed positive response.