Min-ck Seo

The effect of mineral trioxide aggregate on odontogenic differentiation in dental pulp stem cells.

INTRODUCTION This study aimed to identify the early genetic changes related to odontogenic differentiation when mineral trioxide aggregate (MTA) is applied to dental pulp stem cells (DPSCs). METHODS Odontogenic-differentiated cells (induced DPSCs) were obtained by culturing DPSCs in odontoinduction medium for 14 days. Thereafter, MTA in Teflon tubes was applied to the induced DPSCs and uninduced cells. Cells exposed to empty tubes were used as negative controls. The total RNA was extracted from the MTA treated and MTA untreated cells 1 and 3 days after tube application and assessed by microarray analysis. The key results were confirmed selectively by reverse-transcription polymerase chain reaction. We also performed a gene set enrichment analysis. RESULTS In microarray analysis, although the expression levels of 460 genes were changed more than 2-fold in MTA-treated, uninduced DPSCs after 1 day, only 39 genes were altered in MTA-treated, induced DPSCs. In the odontoinduction medium-induced, MTA-treated DPCs, the value of correlation was 0.993 on 1 day and 0.986 on 3 day compared with 0.970 on 1 day and 0.975 on 3 day in the uninduced, MTA-treated DPSCs. Gene set enrichment analysis revealed that MTA significantly up-regulated gene sets involved in cell migration, the response to transforming growth factor β1, and the inflammation pathway in the uninduced DPSCs, whereas in the induced DPSCs it only up-regulated genes involved in cell migration after 1 day. CONCLUSIONS This result shows that MTA stimulates the odontogenic differentiation of DPSCs, and the effects of MTA are drastically increased in uninduced pulp cells compared with odontogenic-differentiated cells.

Prevalence and features of distolingual roots in mandibular molars analyzed by cone-beam computed tomography

Purpose This study evaluated the prevalence of distolingual roots in mandibular molars among Koreans, the root canal system associated with distolingual roots, and the concurrent appearance of a distolingual root in the mandibular first molar and a C-shaped canal in the mandibular second molar. Materials and Methods Cone-beam computed tomographic images of 264 patients were screened and examined. Axial sections of 1056 mandibular molars were evaluated to determine the number of roots. The interorifice distances from the distolingual canal to the distobuccal canal were also estimated. Using an image analysis program, the root canal curvature was calculated. Pearsons chi-square test, the paired t-test, one-way analysis of variance, and post-hoc analysis were performed. Results Distolingual roots were observed in 26.1% of the subjects. In cases where a distolingual root was observed in the mandibular molar, a significant difference was observed in the root canal curvature between the buccolingual and mesiodistal orientations. The maximum root canal curvature was most commonly observed in the mesiodistal orientation in the coronal portion, but in the apical portion, maximum root canal curvature was most often observed in the buccolingual orientation. Conclusion The canal curvature of distolingual roots was found to be very complex, with a different direction in each portion. No correlation was found between the presence of a distolingual root in the mandibular first molar and the presence of a C-shaped canal in the mandibular second molar.

Analysis of gene expression during odontogenic differentiation of cultured human dental pulp cells

Objectives We analyzed gene-expression profiles after 14 day odontogenic induction of human dental pulp cells (DPCs) using a DNA microarray and sought candidate genes possibly associated with mineralization. Materials and Methods Induced human dental pulp cells were obtained by culturing DPCs in odontogenic induction medium (OM) for 14 day. Cells exposed to normal culture medium were used as controls. Total RNA was extracted from cells and analyzed by microarray analysis and the key results were confirmed selectively by reverse-transcriptase polymerase chain reaction (RT-PCR). We also performed a gene set enrichment analysis (GSEA) of the microarray data. Results Six hundred and five genes among the 47,320 probes on the BeadChip differed by a factor of more than two-fold in the induced cells. Of these, 217 genes were upregulated, and 388 were down-regulated. GSEA revealed that in the induced cells, genes implicated in Apoptosis and Signaling by wingless MMTV integration (Wnt) were significantly upregulated. Conclusions Genes implicated in Apoptosis and Signaling by Wnt are highly connected to the differentiation of dental pulp cells into odontoblast.

Finite element analysis of maxillary central incisors restored with various post-and-core applications

The purpose of this study was to investigate the effect of rigidity of post core systems on stress distribution by the theoretical technique, finite element stress-analysis method. Three-dimensional finite element models simulating an endodontically treated maxillary central incisor restored with a zirconia ceramic crown were prepared and 1.5 mm ferrule height was provided. Each model contained cortical bone, trabecular bone, periodontal ligament, 4 mm apical root canal filling, and post-and-core. Six combinations of three parallel type post (zirconia ceramic, glass fiber, and stainless steel) and two core (Paracore and Tetric ceram) materials were evaluated, respectively. A 50 N static occlusal load was applied to the palatal surface of the crown with a 60� angle to the long axis of the tooth. The differences in stress transfer characteristics of the models were analyzed. von Mises stresses were chosen for presentation of results and maximum displacement and hydrostatic pressure were also calculated. An increase of the elastic modulus of the post material increased the stress, but shifted the maximum stress location from the dentin surface to the post material. Buccal side of cervical region (junction of core and crown) of the glass fiber post restored tooth was subjected to the highest stress concentration. Maximum von Mises stress in the remaining radicular tooth structure for low elastic modulus resin core (29.21 MPa) was slightly higher than that for high elastic modulus resin core (29.14 MPa) in case of glass fiber post. Maximum displacement of glass fiber post restored tooth was higher than that of zirconia ceramic or stainless steel post restored tooth. [J Kor Acad Cons Dent 34(4):324-332, 2009]

Evaluation of apical canal shapes produced sequentially during instrumentation with stainless steel hand and Ni-Ti rotary instruments using Micro-computed tomography

ABSTRACT Basic ResearchJKACD Volume 36, Number 3, 2011 Apical preparation size and transportation Stainless steel hand file과Ni-Ti rotary file을이용한근관형성시근단부근관형태의순차적변화에대한평가 이우진 1 ∙이정호 1 ∙전경아 2 ∙서민석 3 ∙유연지 1 ∙백승호 1 * 1 서울대학교치과대학치과보존학교실, 2 고려대학교안암의료원치과보존과, 3 한양대학교서울병원 Evaluation of apical canal shapes produced sequentially during instrumentation with stainless steel hand and Ni-Ti rotary instruments using Micro-computed tomography Woo-Jin Lee 1 , Jeong-Ho Lee 1 , Kyung-A Chun 2 , Min-Seock Seo 3 , Yeon-Jee Yoo 1 , Seung-Ho Baek 1 * 1 Department of Conservative Dentistry and Dental Research Institute, College of Dentistry, Seoul National University, 2 Department of Conservative Dentistry, Korea University Anam Hospital, 3 Hanyang University Seoul Hospital, Seoul, Korea Objectives: The purpose of this study was to determine the optimal master a pical file size with minimaltransportation and optimal efficiency in removing infected dentin. We evaluated the transportation of thecanal center and the change in untouched areas after sequential preparation with a #25 to #40 file using 3different instruments: stainless steel K-type (SS K-file) hand file, ProFile and LightSpeed using micro-computed tomography (MCT). Materials and Methods: Thirty extracted human mandibular molars with separated orifices and apical fora-mens on mesial canals were used. Teeth were randomly divided in to three groups: SS K-file, Profile,LightSpeed and the root canals were instrumented using corresponding instruments from #20 to #40. Allteeth were scanned with MCT before and after instrumentation. Cross section images were used to evalu-ate canal transportation and untouched area at 1- , 2- , 3- , a nd 5- mm level from the apex. Data werestatistically analyzed according to ‘repeated nested design’and Mann-Whitney test (p= 0.05).Results: In SS K-file group, canal transportation was significantly increased over #30 instrument. In theProFile group, canal transportation was significantly increased after preparation with the #40 instrumentat the 1- and 2- mm levels. LightSpeed group showed better cent ering ability than ProFile group afterpreparation with the #40 instrument at the 1 and 2 mm levels. Conclusions: SS K-file, Profile, and LightSpeed showed differences in the degree of apical transportationdepending on the size of the master apical file.

Corrigendum: Corrections to the funding. Quantification of the tug-back by measuring the pulling force and micro computed tomographic evaluation

[This corrects the article on p. 273 in vol. 42, PMID: 29142875.].

Root canal volume change and transportation by Vortex Blue, ProTaper Next, and ProTaper Universal in curved root canals

Objectives The aim of this study was to compare root canal volume change and canal transportation by Vortex Blue (VB; Dentsply Tulsa Dental Specialties), ProTaper Next (PTN; Dentsply Maillefer), and ProTaper Universal (PTU; Dentsply Maillefer) nickel-titanium rotary files in curved root canals. Materials and Methods Thirty canals with 20°–45° of curvature from extracted human molars were used. Root canal instrumentation was performed with VB, PTN, and PTU files up to #30.06, X3, and F3, respectively. Changes in root canal volume before and after the instrumentation, and the amount and direction of canal transportation at 1, 3, and 5 mm from the root apex were measured by using micro-computed tomography. Data of canal volume change were statistically analyzed using one-way analysis of variance and Tukey test, while data of amount and direction of transportation were analyzed using Kruskal-Wallis and Mann-Whitney U test. Results There were no significant differences among 3 groups in terms of canal volume change (p > 0.05). For the amount of transportation, PTN showed significantly less transportation than PTU at 3 mm level (p = 0.005). VB files showed no significant difference in canal transportation at all 3 levels with either PTN or PTU files. Also, VB files showed unique inward transportation tendency in the apical area. Conclusions Other than PTN produced less amount of transportation than PTU at 3 mm level, all 3 file systems showed similar level of canal volume change and transportation, and VB file system could prepare the curved canals without significant shaping errors.

Quantification of the tug-back by measuring the pulling force and micro computed tomographic evaluation

Objectives The aims of this study were to quantify tug-back by measuring the pulling force and investigate the correlation of clinical tug-back pulling force with in vitro gutta-percha (GP) cone adaptation score using micro-computed tomography (µCT). Materials and Methods Twenty-eight roots from human single-rooted teeth were divided into 2 groups. In the ProTaper Next (PTN) group, root canals were prepared with PTN, and in the ProFile (PF) group, root canals were prepared using PF (n = 14). The degree of tug-back was scored after selecting taper-matched GP cones. A novel method using a spring balance was designed to quantify the tug-back by measuring the pulling force. The correlation between tug-back scores, pulling force, and percentage of the gutta-percha occupied area (pGPOA) within apical 3 mm was investigated using µCT. The data were analyzed using Pearsons correlation analysis, one-way analysis of variance (ANOVA) and Tukeys test. Results Specimens with a strong tug-back had a mean pulling force of 1.24 N (range, 0.15–1.70 N). This study showed a positive correlation between tug-back score, pulling force, and pGPOA. However, there was no significant difference in these factors between the PTN and PF groups. Regardless of the groups, pGPOA and pulling force were significantly higher in the specimens with a higher tug-back score (p < 0.05). Conclusions The degree of subjective tug-back was a definitive determinant for master cone adaptation in the root canal. The use of the tug-back scoring system and pulling force allows the interpretation of subjective tug-back in a more objective and quantitative manner.

Healing outcomes of root canal treatment for C-shaped mandibular second molars: a retrospective analysis.

Objectives This study aimed to evaluate the healing rate of non-surgical endodontic treatment between C-shaped and non-C-shaped mandibular second molars. Materials and Methods Clinical records and radiological images of patients who had undergone endodontic treatment on mandibular second molars between 2007 and 2014 were screened. The periapical index scoring system was applied to compare healing outcomes. Information about preoperative and postoperative factors as well as the demographic data of the patients was acquired and evaluated using chi-square and multinomial logistic regression tests. Results The total healing rate was 68.4%. Healing rates for the mandibular second molar were 70.9% in C-shaped canals (n = 79) and 66.6% in non-C-shaped ones (n = 117). The difference was not statistically significant. Conclusions The presence of a C-shaped canal in the mandibular second molar did not have a significantly negative effect on healing after treatment. Instead, proper pulpal diagnosis and final restoration were indicated as having significantly greater influence on the healing outcomes of C-shaped and non-C-shaped canals, respectively.