Efficacy of root-end filling techniques using premixed putty type bioceramic cements: an ex vivo study.

OBJECTIVES: Currently, premixed putty-type bioceramic cements (PPBCs) have become popular materials for root-end fillings. This study investigated three root-end filling techniques using PPBCs and calcium silicate-based sealers including EDTA pretreatment. MATERIALS AND METHODS: Ninety root segments were prepared and standardized with an artificial fin and lateral canal, and assigned to three groups (n = 30). Root-end fillings were placed using BC-RRM Putty alone (Group PA), injection of BC sealer followed by BC-RRM Putty (Lid Technique: Group LT) or BC-RRM Putty with BC sealer coating (Deep putty packing technique: Group DP). Half of each group was pretreated with 17% EDTA. The radiographic images of the specimens were assessed by five graders and push-out bond strength tests were conducted. The data were analyzed with a general linear model including two-way ANOVA and chi-square test at a significance level of 5%. RESULTS: DP approach demonstrated significantly higher bond strength than LT (P < 0.05). However, there was no statistically significant difference in bond strength between PA and either DP or LT. EDTA pretreatment had no significant effect on push-out bond strength. Radiographically, for the main canal, PA and DP scored significantly higher than LT. In the fin, PA scored significantly higher than others (P < 0.05). CONCLUSION: Our study highlights variations in root-end filling techniques. Injecting a bulk of bioceramic sealer before the placement of PPBCs may reduce bond strength and radiopacity. The application of PPBCs alone or in the deep putty technique demonstrates potential for favorable outcomes. EDTA pretreatment did not enhance bond-strength. CLINICAL RELEVANCE: Careful selection and application of bioceramic materials and techniques in root-end fillings may influence the outcome of endodontic root-end surgery. When PPBCs and calcium silicate-based sealers are used together for root-end fillings, sealer followed by deep putty application may offer improved bond strength and radiographic fill compared to the lid technique.

Cerebral Coenurosis of a Long-Tailed Goral, Naemorhedus caudatus, in Korea.

We intended to describe a case of cerebral coenurosis in a long-tailed goral, Naemorhedus caudatus, from Hwacheon-gun, Gangwon-do (Province), in the Korea. The goral, a 10-year-old male, was suffering from neurological symptoms, such as turning the circle to one side without lifting the head straight, and died at 30 days after admission to the wildlife medical rescue center in Chuncheon-si, Gangwon-do. A fluid-filled cyst was detected in the left cerebral hemisphere by computed tomography and magnetic resonance imaging. The cyst removed from the deceased goral was transparent, about 3×3 cm in size, contained a clear fluid and approximately 320 protoscolices invaginating from the internal germinal layer. The protoscolex had 4 suckers and a rostellum with 28 hooklets arranged in 2 rows. By the present study, a case of cerebral coenurosis was first confirmed in a long-tailed goral, N. caudatus, from Gangwon-do, in Korea. The residents frequently exposed in the sylvatic environment should be careful the accidental infections of zoonotic metacestode of Taenia multiceps, Coenurus cerebralis, in Korea.

When to install the endodontic post? First visit with root canal filling versus a separate second visit for post-restoration: A randomized controlled trial.

BACKGROUND: The vibrations created by post-space preparation during the first visit for endodontic treatment could have a significant effect on the intensity of post-operative pain than that association with post-space preparation at the second appointment. OBJECTIVE: The aim of this study was to evaluate the effect of vibrations generated during post-installation, on post-operative pain in endodontically treated teeth. METHODS: One hundred patients with asymptomatic teeth requiring primary root canal treatment and post-installation were enrolled in this study. Fifty patients underwent endodontic treatment with post-installation at the first visit (group 1), while the remaining 50 patients underwent post-installation at the second visit (group 2). The intensity of post-operative pain in both groups was evaluated 1, 2, 3 days and 1 week after the first visit using the visual analogue scale. The time required to achieve complete pain relief for each patient was also recorded. The patients' age, sex, tooth type, size of the periapical lesion and time required for complete post-operative pain relief for each tooth were recorded. RESULTS: The pain intensity score was significantly higher in group 1 than group 2 (P < .05). No significant differences were observed in parameters such as sex, tooth type, jaw and size of the periapical lesion (P > .05), whereas age had a significant effect on the post-operative pain scores (P < .05). CONCLUSION: Vibrations occurring during post-installation on the same visit as that of root canal filling may increase the post-operative pain.

Treatment of peri-invagination lesion and vitality preservation in an immature type III dens invaginatus: a case report.

BACKGROUND: To report a case of type III dens invaginatus associated with peri-invagination periodontitis in an immature permanent mandibular central incisor with open apex, in which only the invagination area was treated and vitality was preserved. CASE PRESENTATION: A 9-year-old boy was referred complaining of pain in the mandibular left central incisor. After radiographic examination, an invagination into the pulp chamber of the tooth associated with periapical radiolucency was detected. Endodontic access was performed and the orifice was identified under a dental operating microscope. The invagination area was chemo-mechanically cleaned. After 1 week, the invagination was obturated with mineral trioxide aggregate. During the 2-year follow up period, the tooth was asymptomatic. Radiographic examination revealed significant progression of periapical healing and root development in the main root canal of the tooth. CONCLUSION: Non-surgical root canal treatment of the invagination may preserve pulp vitality, and continuous root development of the tooth.

The interaction of Hemin and Sestrin2 modulates oxidative stress and colon tumor growth.

Several large epidemiological and animal studies demonstrate a direct correlation between dietary heme iron intake and/or systemic iron levels and cancer risk in several cancers including colorectal cancer (CRC). However, the precise mechanisms for how heme iron contributes to CRC and how cancer cells respond to heme iron-induced stress are still unclear. Previously we have shown that one of the stress-inducible proteins, Sestrin2 (SESN2), is a novel tumor suppressor in colon by limiting endoplasmic reticulum stress and mammalian target of rapamycin complex 1 (mTORC1) signaling and tumor growth. But the relationship between heme iron and SESN2, especially in the context of colon carcinogenesis, was not investigated previously. Here, we found that hemin dose-dependently increased SESN2 expression in an oxidative stress and nuclear factor (erythroid-derived 2)-like 2 (NFE2L2, NRF2)-dependent manner. Since SESN2 overexpression reduced hemin-induced oxidative stress, SESN2 could be an important target of NRF2 exerting antioxidant function. Indeed, expression of several oxidative stress responsive proteins such as NRF2 and its target genes was reduced by SESN2. Although we formerly reported that SESN2 expression was reduced after p53 mutation in colon tumors, mouse colon tumors, which have intact p53 and NRF2, induced SESN2 expression in response to iron stimulus. Although SESN2 overexpression decreased murine colon tumor cell growth both in vitro and in vivo, it rendered colon cancer cells more resistant to hemin-induced apoptosis and therefore promoted tumor growth during hemin treatment. Taken together, although SESN2 generally suppresses tumorigenesis, it can produce tumor-promoting role in iron-rich environment by suppressing oxidative stress-associated cancer cell death.

Evaluation of the efficacy of ivermectin against Theileria orientalis infection in grazing cattle.

BACKGROUND: Raising cattle on pastures is known to be beneficial for animal welfare and cost reduction. However, grazing is associated with the risk of contracting tick-borne diseases, such as theileriosis. Here, the efficacy of ivermectin against these diseases and associated clinical symptoms were evaluated. RESULTS: A total of 68 cattle from a grazing cattle farm were selected and divided into two groups: the control group (17 cattle) with no preventive treatment and the ivermectin-treated group (51 cattle) in which cattle were treated with pour-on ivermectin prior to grazing. The infection rates of Theileria orientalis and the red blood cell (RBC) profile (e.g., RBC count, hematocrit value, and hemoglobin concentration) were compared in the spring (before grazing) and summer (during grazing) between the two groups. Based on PCR amplification of the major piroplasm surface protein (MPSP) gene, 12 cattle were positive for T. orientalis infection. Phylogenetic analysis revealed that the isolates identified in this study consisted of three MPSP types (1, 2, and 7). The T. orientalis infection rate in the control group during grazing was 3-fold higher than that in the ivermectin-treated group. Moreover, differences in RBC parameters during grazing were greater in the control group than in the ivermectin-treated group. In particular, the hematocrit value was significantly reduced in the control group. CONCLUSIONS: The results of this study demonstrated that ivermectin had protective effects against T. orientalis infection and RBC hemolysis in grazing cattle.

Clinical and microbiologic investigation of an expedited peri-implantitis dog model: an animal study.

BACKGROUND: Animal studies are pivotal in allowing experimentation to identify efficacious treatment protocols for resolution of peri-implantitis. The purpose of this investigation was to characterize an expedited dog peri-implantitis model clinically, radiographically, and microbiologically. METHODS: Eight hound dogs underwent extractions (week 0) and implant (3.3 × 8.5 mm) placement with simultaneous surgical defect creation and ligature placement for induction of peri-implantitis (week 10). Ligatures were replaced at 6 weeks (week 16) and removed after 9 weeks (week 19) when supporting bone loss involved approximately 50% of the peri-implant bone. Microbial samples from the defects and healthy control implant sites collected at week 19 were analyzed utilizing a microarray. Clinical measures of inflammation were obtained and radiographic bone loss was measured from periapical radiographs. Radiographic depth and width measurements of bony defect were repeated at weeks 10 (baseline), 16, and 19. Canonical analysis of principal coordinates was used to visualize overall differences in microbial abundance between peri-implantitis and healthy implants. RESULTS: This accelerated disease protocol led to intrabony defect creation with a mean depth and width of 4.3 mm and 3.5 mm, respectively after 9 weeks of ligature placement. Microbial identification revealed 59 total bacteria in peri-implant sites, 21 of which were only present in peri-implant sites as compared to healthy controls. Overall microbial beta diversity (microbial between-sample compositional diversity) differed between peri-implantitis and healthy implants (p = 0.009). CONCLUSIONS: Within the limitations of this study, this protocol led to expedited generation of peri-implant defects with a microbial profile indicative of a shift to disease and defect patterns conducive to regenerative treatment. However, the possibility of potential spontaneous resolution of lesions due to the lack of a chronicity interval as compared to chronic disease models need to be further clarified and considered during preclinical peri-implantitis model selection.

Identification of zoonotic Giardia duodenalis in Korean native calves with normal feces.

Giardia duodenalis is an important zoonotic protozoan parasite that infects humans and other animals. This study was conducted to investigate the prevalence and molecular characterization of G. duodenalis infection in the feces of normal and diarrheic pre-weaned calves aged 1-60 days. Fecal samples were collected from 90 Korean native calves in 7 different regions in the central region of the Republic of Korea (ROK). Of the 90 fecal samples, 9 (10%, 9/90) were positive for G. duodenalis by PCR using the ß-giardin gene. Phylogenetic analysis identified G. duodenalis assemblages A and E in the farms examined and G. duodenalis with both assemblage A and E was detected in one farm. Assemblage A was detected in calves with normal feces, while assemblage E was frequently identified in calves with diarrhea. This is the first report of the identification of assemblage A in pre-weaned calves with normal feces in the ROK. These results suggest that G. duodenalis infection is closely associated with calf age and management systems including overcrowding, age-mixed grouping, and hygiene. Thus, giardiasis in calves is an important disease because of its zoonotic significance and should be screened in young animals. Further studies are necessary to elucidate the transmission routes of zoonotic G. duodenalis assemblages.

Morphological and Molecular Characterization of Toxocara tanuki (Nematoda: Ascaridae) from Korean Raccoon Dog, Nyctereutes procyonoides koreensis.

Present study was performed to describe the morphological and molecular characterization of Toxocara tanuki (Nematoda: Ascaridae) from Korean raccoon dog, Nyctereutes procyonoides koreensis, naturally infected in the Republic of Korea (Korea). Juvenile and adult worms of T. tanuki were recovered in 5 out of 10 raccoon dogs examined and the larval worms were detected in 15 out of 20 muscle samples (75%). Small lateral alae were observed on the cranial end of the body in male and female adults and 2 long spicules (3.0-3.5 mm) were characteristically observed in the posterior end of males. In SEM observation, 18 pairs of proximal precloacal, a precloacal median, a postcloacal median and 5 pairs of postcloacal papillae were uniquely revealed in the posterior portion of males, but the proximal papillae were not shown in the lateral ends of females. Molecular analysis on the 18S rRNA partial DNA sequences was revealed the same finding in both samples, adult worms and muscle larvae, which are closely related to T. tanuki. In conclusion, it was confirmed for the first time that T. tanuki is indigenously distributed, the Korean raccoon dog is acted as the natural definitive host of this nematode in Korea and the morphological characteristics of T. tanuki were shown in specific structure for single postcloacal median papilla in male.

Epidemiological Survey on Eimeria spp. Associated with Diarrhea in Pre-weaned Native Korean Calves.

Bovine coccidiosis is one of the most important parasitic diseases affecting calf productivity. Here, we investi- gated the prevalence of Eimeria spp. in pre-weaned native Korean calves and determined the correlation between diar- rhea and Eimeria spp. Fecal samples were collected from individual calves (288 normal and 191 diarrheic) in 6 different farms. Of the 479 samples, Eimeria oocysts were detected in 124 calves (25.9%). Five Eimeria spp. were identified; E. zuernii (18.8%) was the most prevalent, followed by E. auburnensis (12.5%), E. bovis (7.5%), E. subspherica (5.8%), and E. bukidnonensis (1.0%). A significant correlation was observed between diarrhea and mixed infection with more than 2 Eimeria spp. (odds ratio [OR]=2.21; 95% confidence interval [CI]: 1.09-4.49; P=0.03) compared to single infection (OR = 1.29; 95% CI: 0.77-2.15; P = 0.33). Of the 5 Eimeria spp. identified, E. subspherica (95% CI: 1.24-5.61; P = 0.01) and E. bukidnonensis (95% CI: 825.08-1,134.25; P = 0.00) strongly increased the risk of diarrhea by 2.64-fold and 967.39-fold, respectively, compared to other species. Moreover, mixed infection with E. auburnensis and E. bukidnonensis was significantly associated with diarrhea (OR = 2,388.48; 95% CI: 1,009.71-5,650.00; P < 0.00) in pre-weaned native Korean calves. This is the first report to demonstrate the importance of E. bukidnonensis associated with diarrhea in pre-weaned native Korean calves. Further epidemiological studies should investigate the prevalence of E. bukidnonensis and the association between E. bukidnonensis and diarrhea.

Molecular Identification of Sarcocystis grueneri in Wild Korean Water Deer (Hydropotes inermis argyropus).

The cysts of Sarcocystis grueneri were detected and characterized from the cardiac muscles of the Korean water deer (Hydropotes inermis argyropus). Of the 38 heart muscle samples examined by light microscopy, 10 were found infected with the cysts of Sarcocystis sp. The cysts appeared oval to spherical shape and measured 110-380 µm in length and 90-170 µm in width. A phylogenetic tree of the 18S rRNA sequences (1.5 kb) revealed a close relationship of the infected cysts to genus Sarcocystis. The 18S rRNA sequence of the infected cysts showed 100% identity to S. grueneri and 97% to S. capracanis. Here, we first report the S. grueneri infections in the Korean water deer.

Detection and Identification of Sarcocystis cruzi (Protozoa: Apicomplexa) by Molecular and Ultrastructural Studies in Naturally Infected Korean Cattle (Bos taurus coreanae) from Daejeon, Korea.

To survey the prevalence of Sarcocystis infections, 210 heart samples were collected from Korean native cattle (Bos taurus coreanae) at an abattoir in Daejeon Metropolitan City, Republic of Korea. Sarcocysts were detected form 31 specimens (14.8%) and identified as Sarcocystis cruzi via transmission electron microscopy. The wall of S. cruzi has flattened protrusions that did not contain fibrils or microfilaments. The protrusions arose irregularly from the base, contained a fine granular substance, lacked internal microfilaments, and measured approximately 0.21-1.25 µm in length and 0.05-0.07 µm in width. Sequence analysis revealed 99.5% homology to S. cruzi. This is the first report on the prevalence of S. cruzi in native cattle from the Republic of Korea.

Genetic characterization of Theileria orientalis from cattle in the Republic of Korea.

Theileria orientalis is the causative agent of benign theileriosis, which is distributed mainly in Asian countries, and causes serious economic losses in the livestock industry. The present study was performed to investigate the epidemiology of T. orientalis infections in cattle in the Republic of Korea (ROK) and to characterize the genetic diversity of T. orientalis based on the major piroplasm surface protein (MPSP) genes. In 2015, between July and August, blood samples were collected from 138 asymptomatic cattle in four different geographical regions (Hoengseong, Jeongeup, Namwon, and Jeju island) in the ROK. In total, 57 blood samples (41.3 %, 57/138) were positive for T. orientalis based on PCR amplification of the MPSP gene. A high prevalence of T. orientalis infection was observed in Jeju island, whereas the infection rate was relatively low in Jeongeup. Phylogenetic analysis showed that isolates identified in this study belonged to four MPSP genotypes, specifically types 1, 2, 3, and 7. The distribution of the four genotypes varied considerably among the four regions; types 1, 2, and 3 were detected in Jeju island, whereas types 1 and 7 were found in Namwon, types 1 and 2 in Jeongeup, and type 2 in Hoengseong. To our knowledge, this is the first report on the identification of type 7 T. orientalis in cattle in the ROK. These results suggest that the MPSP genotypes detected in this study showed genetic diversity related to geographical location. Our findings revealed that the T. orientalis infection rate was relatively high, indicating that T. orientalis infection is closely associated with grazing. Of the four MPSP genotypes, the prevalence of the most pathogenic type 2 was relatively high in the ROK. Therefore, further studies should focus on the development of an effective monitoring and prevention program for T. orientalis.

Hematological Changes Associated with Theileria orientalis Infection in Korean Indigenous Cattle.

Tick-borne pathogens can cause serious problems in grazing cattle. However, little information is available on tick-mediated diseases in cattle grazing on mountains. Thus, this study aimed to understand the potential problems related to tick-borne diseases in grazing cattle through the investigation of prevalent tick-transmitted infections, and their associated hematological changes, in terms of season and grazing type in Korean indigenous cattle (=Hanwoo). Hanwoo cattle from 3 regions of the Republic of Korea (=Korea) were either maintained indoors or placed on grassy mountains from spring to fall of 2014 and 2015. Cattle that grazed in mountainous areas showed a greater prevalence of tick-borne infections with an increased Theileria orientalis infection rate (54.7%) compared to that in non-grazing cattle (16.3%) (P<0.001). Accordingly, the red blood cell (RBC) count and hematocrit (HCT) values of grazing cattle were significantly lower than those of non-grazing cattle throughout the season (P<0.05). Moreover, RBC, hemoglobin (Hb), and HCT of T. orientalis-positive group were significantly lower than those of T. orientalis-negative group (P<0.05). T. orientalis is a widespread tick-borne pathogen in Korea. Grazing of cattle in mountainous areas is closely associated with an increase in T. orientalis infection (RR=3.4, P<0.001), and with consequent decreases in RBC count and HCT. Thus, these findings suggest that the Hanwoo cattle in mountainous areas of Korea are at a high risk of infection by T. orientalis, which can lead to hematological alterations. This study highlights the necessity of preventive strategies that target T. orientalis infection.

Identification of bovine viral diarrhea virus infection in Saanen goats in the Republic of Korea.

Bovine viral diarrhea virus (BVDV) is one of the most important viral pathogens of livestock and causes substantial economic losses to the livestock industry worldwide. BVDV is not necessarily species specific and is known to infect domesticated and wild ruminants. In the present study, BVDV infection was identified in two Saanen goats from one farm, and two different viral subtypes were found, BVDV-1a and BVDV-2a. Each isolate was closely related to cattle isolates identified in the Republic of Korea. The two sequences obtained in this study were not consistent with border disease virus (BDV). The incidence of BVDV in this farm apparently occurred in the absence of contact with cattle and may be associated with grazing. This study demonstrates that BVDV infection may be possible to transmit among goats without exposure to cattle. Therefore, this result indicates that Saanen goats may act as natural reservoirs for BVDV. This is the first report of BVDV-1a infection in a Saanen goat.

Outcome of nonsurgical retreatment and endodontic microsurgery: a meta-analysis.

OBJECTIVES: The purpose of this study was to evaluate and compare the clinical and radiographic outcomes of nonsurgical endodontic retreatment and endodontic microsurgery by a meta-analysis. MATERIALS AND METHODS: Electronic databases including PubMed, Embase, Medline, and The Cochrane Library were searched, and the references of related articles were manually searched to identify all the clinical studies that evaluated the clinical and radiographic outcomes after retreatment or microsurgery. The first and second screening processes were conducted by three reviewers independently. The final studies were selected after strict application of the inclusion and exclusion criteria. The random effects meta-analysis model with the DerSimonian-Laird pooling method was performed. The weighted pooled success rates and 95 % confidence interval estimates of the outcome were calculated. Additionally, the effects of the follow-up period and study quality were investigated by a subgroup analysis. RESULTS: Endodontic microsurgery and nonsurgical retreatment have stable outcomes presenting 92 and 80 % of overall pooled success rates, respectively. The microsurgery group had a significantly higher success rate than the retreatment group. When the data were organized and analyzed according to their follow-up periods, a significantly higher success rate was found for the microsurgery group in the short-term follow-up (less than 4 years), whereas no significant difference was observed in the long-term follow-up (more than 4 years). CONCLUSIONS: Endodontic microsurgery was confirmed as a reliable treatment option with favorable initial healing and a predictable outcome. CLINICAL RELEVANCE: Clinicians may consider the microsurgery as an effective way of retreatment as well as nonsurgical retreatment depending on the clinical situations.

First record of Cosmocephalus obvelatus (Acuariidae) in common gulls (Larus canus) from Gangneung, Korea.

A nematode species belonging to the genus Cosmocephalus was collected from the stomach of 2 common gulls, Larus canus. The common gulls were found dead on the seaside of Gangneung City, the Republic of Korea. The worms were identified and classified by light (LM) and scanning electron microscopy (SEM) on the basis of important taxonomic characters. The nematodes were characterized by a body length 9.1-9.3 mm (males) and 15.5-15.9 mm (females) and cordons recurrent in anterior direction and anastomosing laterally at about the level of anterior quarter of the buccal cavity. The salient bicuspid deirids were located on the posterior to the cordons. Lateral alae were well-developed, extending from the level just posterior of deirids to the level about middle of the body. LM and SEM observations identified the worms as C. obvelatus. This is the first reported case of C. obvelatus infection in common gulls in Korea.

A Horsehair Worm, Gordius sp. (Nematomorpha: Gordiida), Passed in a Canine Feces.

Nematomorpha, horsehair or Gordian worms, include about 300 freshwater species in 22 genera (Gordiida) and 5 marine species in 1 marine genus (Nectonema). They are parasitic in arthropods during their juvenile stage. In the present study, the used gordian worm was found in the feces of a dog (5-month old, male) in July 2014. Following the worm analysis using light and scanning electron microscopes, the morphological classification was re-evaluated with molecular analysis. The worm was determined to be a male worm having a bi-lobed tail and had male gonads in cross sections. It was identified as Gordius sp. (Nematomorpha: Gordiidae) based on the characteristic morphologies of cross sections and areole on the cuticle. DNA analysis on 18S rRNA partial sequence arrangements was also carried out, and the gordiid worm was assumed to be close to the genus Gordius based on a phylogenic tree analysis.

Identifying non-elliptical entity mentions in a coordinated NP with ellipses.

Named entities in the biomedical domain are often written using a Noun Phrase (NP) along with a coordinating conjunction such as 'and' and 'or'. In addition, repeated words among named entity mentions are frequently omitted. It is often difficult to identify named entities. Although various Named Entity Recognition (NER) methods have tried to solve this problem, these methods can only deal with relatively simple elliptical patterns in coordinated NPs. We propose a new NER method for identifying non-elliptical entity mentions with simple or complex ellipses using linguistic rules and an entity mention dictionary. The GENIA and CRAFT corpora were used to evaluate the performance of the proposed system. The GENIA corpus was used to evaluate the performance of the system according to the quality of the dictionary. The GENIA corpus comprises 3434 non-elliptical entity mentions in 1585 coordinated NPs with ellipses. The system achieves 92.11% precision, 95.20% recall, and 93.63% F-score in identification of non-elliptical entity mentions in coordinated NPs. The accuracy of the system in resolving simple and complex ellipses is 94.54% and 91.95%, respectively. The CRAFT corpus was used to evaluate the performance of the system under realistic conditions. The system achieved 78.47% precision, 67.10% recall, and 72.34% F-score in coordinated NPs. The performance evaluations of the system show that it efficiently solves the problem caused by ellipses, and improves NER performance. The algorithm is implemented in PHP and the code can be downloaded from https://code.google.com/p/medtextmining/.

Retreatment Strategies for Cases Containing Calcium Silicate-Based Root Canal Sealers: A Comprehensive Review.

This review explores the field of retreatment strategies for cases filled with calcium silicate-based root canal sealers. Since the introduction of calcium silicate-based materials in dentistry, calcium silicate-based root canal sealers have become popular among dentists because of their biocompatibility, bioactivity, and sealing ability. Therefore, effective retreatment strategies are indispensable. This article aims to identify the challenges associated with the removal of calcium silicate-based sealers themselves and removal of gutta-percha with the sealers during retreatment, evaluate current techniques and materials, and provide future directions for research in this field. Regarding the strategies of removal of root canal sealers, calcium silicate-based sealers are still relatively new materials for clinicians compared with traditional sealers such as epoxy- or eugenol-based sealers. First, no clinically established solvents have been reported. Second, calcium silicate-based sealers are currently utilized by clinicians in either the cold sealer-based technique or the warm vertical condensation technique. Third, the setting process of calcium silicate-based sealers generates byproducts, primarily calcium hydroxide and secondarily hydroxyapatite, that could interact with dentine. Lastly, there is a lack of clinical studies evaluating the efficacy of retreatment protocols for teeth filled with calcium silicate-based sealers. Therefore, it is important to investigate the chemo-mechanical properties of calcium silicate-based sealers themselves and their reactions to solvents and/or mechanical instruments and identify the interfacial properties of calcium silicate-based sealers with respect to dentine and gutta-percha. In addition, researchers in the clinical field need to actively gather and report data on retreatments of teeth filled with calcium silicate-based sealers.