Abstract : Purpose : In this study, using bioactive glass-based cement (Nishika Canal Sealer BG multi), the interface between bioactive glass cements with different paste/powder ratios, which correspond to usage in perforation repair and retrofilling, was analyzed.

 Materials and Methods : Mixtures type 1 and type 2 (the paste/powder ratios of type 1 and 2 were 10 : 0 and 10 : 6.7, respectively) were filled in the cavity of a resin-mold. Three types of specimen with different filling-order of the two mixtures were prepared. Each specimen was cut at the center, and each cross-section was analyzed using a low-vacuum scanning electron microscope and energy-dispersive X-ray spectrometer.

 Results and Discussion : No gaps were observed at the interface of the mixtures in all specimens, suggesting that bioactive glass cements with different paste/powder ratios were integrated.

 Conclusion : Nishika Canal Sealer BG multi may be useful for perforation repair and retrofilling.

Abstract : Purpose : The purpose of this study was to evaluate the flow of root canal sealers including a new tricalcium silicate-based sealer and to verify its compliance to ISO 6876 (2012).

 Materials and Methods : Two kinds of calcium silicate-based sealer (Bio-C^® SEALER, Well-Pulp ST^®), a bioactive glass-based sealer (Canal Sealer BG^®), an epoxy resin sealer (AH plus JET^®) and a zinc oxide eugenol sealer (NISHIKA CANAL SEALER, Control) were prepared. After manipulation of the sealer, 0.05 mL of the material was placed in the center of a glass plate using a graduated disposable syringe (n=10). Another glass plate (20 g) was placed over the sealer, and a 100-g weight was put on the plate and kept there for 10 minutes. After this period, the longest diameter and shortest diameter of the resulting sealer disks were measured using digital calipers, and the mean value was recorded. The data were analyzed statistically by one-way analysis of variance, followed by Tukey-Kramer multiple tests.

 Results and Discussion : Bio-C^® SEALER showed the highest flow, and Canal Sealer BG^® showed the lowest flow in the analysis. In a comparison of flow values among bio-ceramic sealers, Canal Sealer BG^® presented a flow significantly lower than Bio-C^® SEALER and Well-Pulp ST^® (p<0.01). Also, Canal Sealer BG^® presented a flow significantly lower than AH Plus JET^® (p<0.05). Calcium silicate-based endodontic sealers showed higher flow values than any other sealers.

 Conclusion : Flow is an important property for root canal filling and to facilitate obturation. Single-cone techniques rely on a sealer to flow and fill any space between the cone and dentin to provide a tight seal. Premixed ready-to-use calcium silicate-based endodontic sealers presented high flow values within the limitations of this study, and their superior flowability may be beneficial in single-cone root-filling techniques.

Abstract : The smear layer must be removed from the root canal wall, because it affects the residual source of infection and the root canal sealing ability. This study investigated the efficiency of removing the smear layer by using different ultrasonic frequencies with EDTA solution.

 Thirty extracted human permanent teeth with a single straight root canal were used as experimental teeth. All the crowns had been removed 15 mm from the apex. Experimental root canals were enlarged to #40 with NiTi rotary files. The root canals were filled with saline solution during the procedure, and then thoroughly irrigated with 6% NaClO.

 The experimental teeth were randomly divided into three groups to compare the removal effects of the smear layer formed by the root canal enlargement. Group 1 : the root canals were irrigated with 17% EDTA solution (4.0 mL/min) using a syringe ; Group 2 : the root canals were filled with EDTA and ultrasonic vibration at 30,000 Hz was applied ; Group 3 : the root canals were filled with EDTA and ultrasonic vibration at 40,000 Hz was applied. In each group, five teeth were irrigated for 15 seconds and 30 seconds each. After the procedure, EDTA was thoroughly flushed with NaClO. The experimental roots were mesio-distally divided into two pieces for SEM observation of the root canal walls. The root canal walls were divided into three portions, the coronal side, the middle portion, and the apical portion, and the residual condition of the smear layer was scored and evaluated according to Torabinejad et al.’s classification method from the SEM images.

 Thirty seconds of irrigation was better than 15 seconds in Group 1. In Groups 2 and 3, there was almost no difference in the removal effects of the smear layer depending on the application time. In all groups, better removal of the smear layer was observed on the crown and middle portions compared to the apical portion.

 From the results of this study it was concluded that the combined use of EDTA and an ultrasonic device is more effective in removing the smear layer. The removal effect was not affected by the frequency of the ultrasonic device.

Abstract : Purpose : It has been reported that the cause of persistent apical periodontitis is residual infected tissue and debris in uninstrumented areas where chemomechanical root canal preparation is ineffective. When applying a high-frequency current, the current density rises at the tip of the electrode, generating Joule heat. In this case report, high-frequency conduction (HFC) was applied to sterilize and detoxify infectious substances in the extraradicular uninstrumented areas.

 Cases : HFC was performed on two cases in which inflammation of apical periodontal tissue did not disappear despite appropriate chemomechanical root canal preparation. As a result, we observed reduction in bone defects followed by bone regeneration.

 Discussion : Since the inflammation was eliminated by applying HFC to the extraradicular uninstrumented areas such as the external root surface and the inside of the apical lesion, it is considered that the infection in the areas was the cause of the intractability.

 Conclusion : It is suggested that HFC is useful as a minimally invasive nonsurgical endodontic treatment that can approach uninstrumented areas.

Abstract : There are different classifications of external root resorption. As Heithersay GS reported, treatment for invasive cervical resorption becomes difficult once the resorption reaches the apical portion. In the present case report, root resorption that continued from the root area of the lower right canine into the root canal was observed by CBCT. It was diagnosed as invasive resorption accompanying periodontitis. Regular root canal treatment, with rubber-dam and sufficient irrigation followed by obturation, was performed.

 After root canal obturation, a flap was opened under a microscope, followed by curettage of the granulation tissue of the resorption area from the periodontal ligament side. Then, MTA was used to seal the resorption area. At one-year follow-up, there was no tenderness, pus from periodontal pockets or any other symptoms.

 It is considered that the removal of granulation tissue and separation of the root canal from the periodontal pocket with MTA filling is effective for the treatment of invasive resorption.