Yoshiko Masuda

Micro-computed Tomographic Comparison of Nickel-Titanium Rotary versus Traditional Instruments in C-Shaped Root Canal System

INTRODUCTION The purpose of this study was to assess the efficacy of instrumentation of C-shaped canals with ProTaper rotary system and traditional instruments by using micro-computed tomography (micro-CT). METHODS Twenty-four mandibular molars with C-shaped canals were selected in pairs and sorted equally into 2 groups, which were assigned for instrumentation by ProTaper rotary system (ProTaper group) or by K-files and Gates-Glidden burs (Hand Instrument group). Three-dimensional images were constructed by micro-CT. The volume of dentin removed, uninstrumented canal area, time taken for instrumentation, and iatrogenic error of instrumentation were investigated. RESULTS Hand Instrument group showed greater amount of volumetric dentin removal and left less uninstrumented canal area than ProTaper group (P < .01). The time needed for instrumentation was shorter for ProTaper group than for Hand Instrument group (P < .05). No instrument breakage occurred in both groups, but more conspicuous procedural errors were detected in Hand Instrument group than for ProTaper group. CONCLUSIONS It was concluded that ProTaper rotary system maintained the canal curvature with speediness and few procedural errors, whereas traditional instrumentation can clean more canal surface.

Effect of glypican-1 gene on the pulp cells during the reparative dentine process

GPC‐1 (glypican‐1) is a cell surface heparan sulfate proteoglycan that acts as a co‐receptor for heparin‐binding growth factors and members of the TGF‐β (transforming growth factor beta‐1) family. The function of cell‐surface proteoglycans in the reparative dentine process has been under investigation. Gpc‐1 was detected with similar frequency as tgf‐β1 in the cDNA library using mRNA from the odontoblast‐like cell‐enriched pulp of rat incisors. The aim of this study was to test our hypothesis that gpc‐1 may be related to reparative dentine formation. We examined the expression of this gene during the reparative dentine process, as well as the effect of gpc‐1 on odontoblast‐like cell differentiation using siRNA (small interfering RNA) to down‐regulate gpc‐1 expression. Immunohistological examination showed that GPC‐1 was expressed in pulp cells entrapped by fibrodentine and odontoblast‐like cells as well as TGF‐β1. The mRNAs for gpc‐1, ‐3 and ‐4, except for gpc‐2, were expressed during odontoblast‐like cell differentiation in pulp cells. The relative levels of gpc‐1 mRNA were increased prior to the differentiation stages and were decreased during the secretory and maturation stages of pulp cells. Down‐regulation of gpc‐1 expression resulted in a 3.9‐fold increase in tgf‐β1 expression in pulp cells and a 0.3‐fold decrease in dspp (dentine sialophosphoprotein) expression compared with control. These results suggested that gpc‐1 and tgfβ‐1 expression are necessary for the onset of differentiation, but should be down‐regulated before other molecules are implicated in the formation of reparative dentine. In conclusion, gpc‐1 expression in odontoblast‐like cells is associated with the early differentiation but not with the formation of reparative dentine.

Basic study of the use of laser on detection of vertical root fracture.

OBJECTIVE Many methods are used to detect vertical root fractures, but most are not adequate for identification of incomplete fractures or cracks. The purpose of this study was to evaluate the effects of three detergents on detection of vertical root fractures by DIAGNOdent with methylene blue (MB) solution. METHODS Vertical incomplete fractures were artificially created on the roots of extracted human teeth, the DIAGNOdent values (D values) recorded in the presence or absence of MB solution, and the effects of detergents on D values examined. The effects of 20% ethanol on enhancing detergent action were also investigated. Statistical analysis was performed using the Mann-Whitney U-test; a value of p<0.01 was considered significant. RESULTS D values increased significantly when MB solution was used with 0.1% or 1.0% polyoxyethylene (10) octylphenyl ether compared to MB solution only. CONCLUSION These findings suggest that 0.1% or 1.0% polyoxyethylene (10) octylphenyl ether could be used as an enhancer for detection of vertical root fractures by DIAGNOdent using MB solution.

Analysis of surface roughness and microleakage of fissure sealants following organic debris removal with Carisolv

OBJECTIVE The objective of the present study was to improve fissure sealing by pre-treatment with Carisolv in order to remove organic debris. The surface morphology and roughness of fissure cavities and the degree of microleakage after Carisolv application were compared with those after bristle brush treatment in vitro. METHODS Fifty extracted human teeth were used in this study. The teeth were randomly divided into two groups of 25 each. Artificial fissures were prepared in all teeth into which artificial organic debris was placed. The debris in 25 teeth of one group was removed using Carisolv applied for 30s and excavation was performed with a dental explorer until the gel was clear. The remaining 25 teeth were then cleaned using bristle brush with prophylaxis paste. Surface roughness was analyzed in five samples from each group by color laser three-dimensional (3D) microscopy and by scanning electron microscopic examination. The remaining samples were filled with sealant and subjected to a microleakage test under thermocycling. Statistical analysis was performed using the Mann-Whitney U-test; a value of p<0.05 was considered significant. RESULTS Morphologically, most of the debris in the fissures was removed by Carisolv treatment, whereas some fissures were not cleaned by bristle brush. Carisolv-treatment with acid-etching resulted in removal of debris-like smear layer leaving enamel prisms open, and 3D laser microscopy demonstrated that the roughness values increased after acid-etching. However, microleakage test of both Carisolv and brush methods showed similar results. CONCLUSIONS Carisolv-treated surfaces especially when subjected to acid-etching might facilitate good adaptation of sealant to enamel, because of an increase in surface roughness and favorable surface characteristics.

The Study of Chitosan-Citrate Solution as a Root Canal Irrigant: A Preliminary Report

Objective: Citric acid has been reported removal of smear layer, low antibacterial property, low cytotoxicity. Although the citric acid alone has few used as a root canal irrigant, citric acid formulation with antibacterial effect such as MTAD and Tetraclean has already produced. However, these formulations tended to produce bacteria resistant to antibiotics such as tetracycline and others. Chitosan have been reported broad spectrum of antibacterial properties, high chelating ability for various metal ions in acidic conditions, biocompatibility and biodegradability. Therefore, we focused on citric acid as a solution to dissolve chitosan. The purpose of this study was to determine whether chitosan-citrate solution shows antibacterial properties against Enterococcus faecalis and removes the smear layer when used as a root canal irrigant. Methods: E. faecalis (4532D) was incubated in brain-heart infusion broth. Chitosan-citrate solution was then added to the bacterial inoculum for 5, 15, 30, and 60 min. Survival rates of E. faecalis were statistically analyzed using one-way repeated measures ANOVA and Tukey test. Extracted teeth were used for this experiment. The middle third of the root was cut longitudinally, and all specimens were immersed in chitosan-citrate solution until an antibacterial effect was obtained. All specimens were examined under scanning electron microscopy. The number of open dentin tubules was determined for evaluation of smear layer removal. One-way repeated measures ANOVA and Tukey test were used for analysis of open dentin tubules. Results: The antibacterial effect of chitosan-citrate solution was achieved at 5 min. Furthermore, chitosan-citrate solution resulted in a significantly greater reduction of the survival rate than 10% citric acid after 5 min of application (p<0.01). The smear layer was also removed after immersion in chitosan-citrate solution for 5 min. Chitosan-citrate solution removed significantly more of the smear layer than 10% citric acid (P<0.05). Conclusion: In conclusion, chitosan-citrate solution showed antibacterial activity and enabled removal of smear layer. As this ability depended on chitosan, it is considered that the action was enhanced by chitosan. Chitosancitrate solution has been indicated as a possible root canal irrigant.

Comparison of apical centring ability between incisal-shifted access and traditional lingual access for maxillary anterior teeth

The aim of this study was to compare the apical centring ability of incisal-shifted access (ISA) with that of traditional lingual access (TLA). Fifteen three-dimensional printed resin models were prepared from the computed tomography data for a human maxillary central incisor and divided into ISA (n = 7), TLA (n = 7) and control (n = 1) groups. After access preparation, these models were shaped to the working length using K-files up to #40, followed by step-back procedures. An apical portion of the model was removed at 0.5 mm coronal to the working length. Microscopic images of each cutting surface were taken to measure the preparation area and the distance of transportation. TLA created a larger preparation area than ISA (P < 0.05). The distance of transportation (mean ± standard deviation) was 0.4 ± 0.1 mm for ISA and 0.7 ± 0.1 mm for TLA (P < 0.05). Access cavity preparation has a significant effect on apical centring ability. ISA is beneficial to maintaining apical configuration.

Evaluation of Root Canal Obturation by Micro-computed Tomography for Endodontic Training in Dental Students

Introduction: The purpose of this study was to evaluate the outcomes of root canal preparation and obturation by third year students who were performing root canal treatment for the first time, with micro-computed tomography (micro-CT) and compare the images taken at the first and second obturations for their training. Methods: Single-rooted straight artificial right maxillary incisors for endodontic training were used for root canal preparation. The canals were obturated with gutta-percha and sealer. Six incisors judged to be well-obturated based on 2-D dental X-ray images were selected for micro-CT scanning. Based on the micro-CT images of the obturation performed for the first time, the areas for improvement were explained to each student individually. Then, root canal preparation and obturation were repeated using a new artificial tooth. The obturated artificial tooth was scanned by micro-CT. Digital three-dimensional (3-D) images were constructed. The volumes of the gaps and voids in the root canal and preparation size were calculated from the cementoenamel junction up to the apex after first and second root canal obturation. Results: After first root canal obturation, mean value of the gaps and voids was reduced. Significant differences were observed between the first time and second time obturation group (p=0.05). The mean value of the preparation size was slightly increased. No significant changes in the preparation size were observed. Conclusions: These results suggested that micro-CT was an effective tool for evaluation of the outcome of endodontic training.

In Vitro Guidance of Dental Pulp Cells by Nd:YAG Laser-Irradiated Endothelial Cells

OBJECTIVE After endothelial cells were ablated by neodymium:yttrium-aluminum-garnet (Nd:YAG) laser irradiation, we investigated the response of pulp cells by examining the expression of transforming growth factor beta-1 (TGF-β1). BACKGROUND DATA The reaction of stimulated blood vessels is related to the initiation of dentinogenesis. After artificial injury of endothelial cells, pulp cells migrate to the site of the injured endothelial cells. MATERIALS AND METHODS Rat aortic endothelial cells were cultured in the lower compartment of the experimental assembly, and a pulsed Nd:YAG laser was used to ablate these cells. Pulp cells were fluorescence labeled and cultured in the upper compartment. After 7-14 days of laser irradiation, total RNA was extracted from the cells in the lower chamber, and RT-PCR was performed to examine the expression of TGF-β1 and osteocalcin mRNA. TGF-β1 was also examined with immunohistochemistry. RESULTS Seven days after laser irradiation, migrating pulp cells that expressed TGF-β1 were observed in the lower compartment, and the expression of TGF-β1 mRNA and osteocalcin mRNA was altered. Without laser irradiation, few migrating pulp cells were observed, and the expression of TGF-β1 mRNA and osteocalcin mRNA was weak. These results suggested that TGF-β1 mRNA expression is detected earlier in pulp cells rather than in endothelial cells following injury to endothelial cells. CONCLUSIONS Using the Nd:YAG laser as an ablative stimulant, this study model was useful for investigating pulp-endothelial cell interactions in reparative dentinogenesis.

Photodynamic Therapy with Pyoktanin Blue and Diode Laser for Elimination ofEnterococcus faecalis

Background/Aim: Enterococcus faecalis is responsible for most cases of endodontic treatment failure. Despite various conventional disinfection methods, root canals are not completely free of microorganisms. Photodynamic therapy (PDT) is a new antimicrobial strategy that involves the use of a non-toxic photosensitizer (PS) and a light source. The aim of this study was to evaluate the antimicrobial effect of PDT using diode laser and pyoktanin blue (PB) and confirm the nontoxicity of PB as a PS. Materials and Methods: Laser irradiation with an output power of 3 W was performed with PB as the PS to a bacterial solution containing E. faecalis. Then, the number of colony-forming units was counted. PB cytotoxicity was also assessed by the MTT assay. Results: E. faecalis counts were reduced after laser irradiation, laser irradiation with PB, or the combination thereof compared to the control, non-irradiation or water. The 50% cytotoxic concentration value for adult human dermal fibroblasts incubated with PB for 1 min was 108 μg/ml. Conclusion: Diode laser irradiation in combination with PB as the PS is efficacious for the elimination of E. faecalis without toxic effects to human dermal fibroblasts. This strategy might be useful for root canal irrigants.

Management of Tooth and Observation of External Root Surface with Extrusion of Calcium Hydroxide-Containing Paste

Introduction: Extrusion of the root canal filling materials is often absorbed and heals, which produces no irreversible changes. However, sometimes it causes the persisting pain and apical radiolucent. This case shows that extrusion of calcium hydroxide [Ca(OH)2] intracanal medicament caused the persistent percussion pain. Methods: This case report describes the patient with extrusion of Ca(OH)2 into the periapical tissue in the mandibular right second premolar. A 48-year-old female presented with persistent occlusal pain. Radiographs revealed a radiolucent lesion in the periapical region of mandibular second premolar. The cone-beam computed tomography scan revealed the non-radiolucency root canal materials around the root apex and periapical radiolucency was present along with considerable external root resorption. After preparation, root canal was filled with gutta-percha cones and root canal sealer, and intentional replantation with apicoectomy was performed. The resected portion of root apex was observed by stereomicroscopy and scanning electron microscopy (SEM). Results: The root surface contacted with Ca(OH)2 paste was observed by stereomicroscopy. SEM observation revealed that the area of the apical foramen was covered with the complex of the extended materials and resorption of apex was observed. At the 1-month recall appointment, the patient presented asymptomatically without tooth mobility. Five months after the surgery, radiograph showed new bone formation around periapical region. The patient had no clinical symptoms of pain. Conclusions: The treatment had been successful, achieving adequate repair with 9 months of follow-up. Appropriate size of the apical foramen was essential for success of the root canal treatment. Extrusion of Ca(OH)2 paste caused persistent occlusal pain and the apical foramen coverage by the materials.