• Restorative Dentistry and Endodontics
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• v.46 no.2
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• pp.28.1-28.10
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• 2021

Objectives: This study evaluated the effect of repeated uses and autoclaving in the instrumented area, fracture resistance, and time of instrumentation of thermally treated nickel-titanium reciprocating systems. Materials and Methods: Two hundred simulated canals were instrumented using Reciproc Blue and WaveOne Gold. Each file was used up to 10 times or until fracture. The instrumented area was measured in pre- and post-operative images, using ImageJ software. Kaplan-Meier survival analysis evaluated the number of uses of instruments before fracture. Instrumented area and time of instrumentation were analyzed by Mann-Whitney U test and Kruskal-Wallis. Correlations among the number of uses and instrumented area were measured. The level of statistical significance was set at p < 0.05. Results: Reciproc Blue presented a higher estimated number of uses in comparison with WaveOne Gold (p = 0.026), but autoclaving did not affect the resistance to fracture of instruments (p > 0.05). The instrumented area was different among the evaluated groups (p = 0.039), and the instrumented area along the uses of both tested instruments was reduced. With the time of instrumentation, there was also a significant difference among the evaluated groups; the groups without sterilization cycles were faster, in comparison to those submitted to autoclaving (p = 0.010). Conclusions: Reciproc Blue was more resistant than WaveOne Gold, suffering later fracture. Additionally, the sterilization cycles did not influence the estimated number of uses of thermally treated reciprocating instruments, but the instrumented area of root canals was reduced along with the repeated uses of both instruments.

• Microbiology and Biotechnology Letters
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• v.32 no.2
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• pp.195-198
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• 2004

Molec-ular analysis was performed on the microflora found In the necrotic pulpal tissue collected from 5 infected root canals that were diagnosed as a periapical abscess. 16S rRNA coding gene (rDNA) library construction and sequencing were performed in order to identify the microflora, The 16S rDNA sequences from 278 clones were identified by a comparison with the database sequence in GenBank. Three phylum and 31 species, which were related to the oral microflora, were identified from the 3 samples (No. 87, 105, and 115). Dialister invisus (5.6％), Peptostreptococcus micron (18.3％), and Veillonella sp. (3.3％) were the organism present in all tee samples. Lac-tobacillusfementum (2.8％),Eubacterumsp./E. infirmum (6.7％), Shuttleworthiasatelles (3.9％), Psudorarnihacfer alactoiyticus (13.3％), Bulleidia moorei (2.8％), and Prevotella denticola (1.1％) were found in two samples. Two phylum and low species of environmental microflora were identified from 2 samples (No.95 and 101). The reason for this might be contamination of the samples with dental water. These results showed that molecular analysis could reveal more diverse microflora that are associated with endodontic infections than that revealed by conventional cultural methods. In addition, these results may of for the basic data to epidemiological studies related with endodontic infection.

• Restorative Dentistry and Endodontics
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• v.19 no.1
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• pp.85-96
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• 1994

In this study, 24 curved resin blocks were prepared by one of the following four methods: 1) Conventional technique using K-flexo files 2) Step-back technique using K-flexo files 3) Crown-down technique using K-flexo files 4) Canal Master instrumentation using Canal Master Resin blocks were sectioned, photographed, and evaluated the mean centering ratio and the mean area of dentin removed before and after the instrumentation. The results were as follows : I. the mean centering ratio 1. In the level 1 and level 3, there was no significant difference in the mean centering ratio. 2. In the level 2, Step-back technique showed the worst mean centering ratio among the tested groups(p<0.001) and there was no significant difference between the other three groups. 3. In the level 4, Canal Master instrumentation and Step-back technique showed better mean centering ratio than the other two techniques(p<0.001) and there was no significant difference between the two techniques. II. the mean area of dentin removed 1. In the level l and level 3, there was no significant difference in the mean area of dentin removed. 2. In the level 2, Canal Master instrumentation removed less dentin than the other three techniques(P<0.01). 3. In the level 4, Crown-down technique removed less dentin than the other three techniques(P<0.05).

• Restorative Dentistry and Endodontics
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• v.38 no.1
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• pp.26-30
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• 2013

Objectives: The aim of this study was to investigate the relationship between the apical foramen morphology and the length of merged canal at the apex in type II root canal system. Materials and Methods: This study included intact extracted maxillary and mandibular human premolars (n = 20) with fully formed roots without any visible signs of external resorption. The root segments were obtained by removing the crown 1 mm beneath the cementum-enamel junction (CEJ) using a rotary diamond disk. The distance between the file tip and merged point of joining two canals was defined as Lj. The roots were carefully sectioned at 1 mm from the apex by a slow-speed water-cooled diamond saw. All cross sections were examined under the microscope at ${\times}50$ magnification and photographed to estimate the shape of the apical foramen. The longest and the shortest diameter of apical foramen was measured using ImageJ program (1.44p, National Institutes of Health). Correlation coefficient was calculated to identify the link between Lj and the apical foramen shape by Pearson's correlation. Results: The average value of Lj was 3.74 mm. The average of proportion (P), estimated by dividing the longest diameter into the shortest diameter of the apical foramen, was 3.64. This study showed a significant negative correlation between P and Lj (p < 0.05). Conclusions: As Lj gets longer, the apical foramen becomes more ovally shaped. Likewise, as it gets shorter, the apical foramen becomes more flat shaped.

• Restorative Dentistry and Endodontics
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• v.13 no.1
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• pp.103-111
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• 1988

The purpose of this study was to, examine the sealing ability of the denting bonding agent, when used with gutta percha cone, as a root canal sealer. Seventy two upper and lower extracted human teeth with single root were randomly selected and instrumented in a conventional method with K-file. After instrumentation and dry the canal with paper point, there were divided into three groups and twenty four teeth in each group were filled with the following material; In group I: Scotchbond in combination with gutta percha cone. In group II: AH 26 in combination with gutta percha cone. In group III: Tubli-Seal in combination with gutta percha cone. All specimens were immersed in Indian Ink, decalcified, and cleared. The depth of dye penetration into the canals were evaluated by caliper at the intervals of 1 day, 1 week, 2 weeks. The results were as follows; 1. Depth of dye penetration for all groups increased with time. 2. As to difference in mean dye penetration at time interval of 1 day and 14 days, Scotchbond group exhibited the smallest value as 0.53mm and Tubli-Seal group exhibited the largest value as 0.70mm. 3. There was the difference of dye penetration between each group, but its difference was not significant, statistically.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.71-95
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• 1995

Bacteria have been regarded as a one of major etiologic factors in root canal infections. In endodontic treatment the effective removal of pathogenic microorganisms in the root canal is the key to successful outcome. Bacterial cell wall components may play an important role in the development of pulpal and periapical disease. The purpose of this study was to evaluate the effect of sonic extracts of Streptococcus spp. on cultured L929 cells and to characterize cell wall protein profiles of Streptococcus spp. Streptococcus spp. were isolated from infected root canals and identified with Vitek Systems(Biomeriux, USA). Five streptococci, namely S. sanguis, S. mitis, S uberis, S. mutans (ATCC 10449) and S. faecalis (ATCC 19433) weere enriched in brain heart infusion broth. Cell pellets were sonicated and cell wall extracts were dialyzed and membrane filtered. Prepared cell wall proteins were applied to cultured L929 cell. The cell reaction were evaluated by monitoring DNA synthesis, cell numbers and the change of cell morphology. The total cell wall protein profiles of microorganisms were characterized by sodium dodecyl sulfate polyacrylamide-gel eledruphoresis(SDS-PAGE). DNA synthesis of L929 cells were reduced by the increasing concentration of sonic extracts. DNA synthesis was significantly suppressed in more than $50{\mu}g$/ml of sonic extract conentration in five streptococci. S. nutans (ATCC 10449) showed stronger suppression on DNA synthesis than remaining four streptococci, which had the similar effect on DNA synthesis. Analysis of DNA synthesis measured by [$^3H$]-thymidine uptake was more sensitvie method than cell counting. Sonic extracts affected the microscopic findings of L929 cells. The protein profiles indicated that all five strains shared two major proteins with molecular masses of 70.8 and 57.5 kD respectively. S. uberis and S. mutans shared common minor proteins of which molecular weights were 147.9 and 112.2 kD respectively. However some minor proteins were unique for S. mitis, S. uberis and S. faecalis.

• Restorative Dentistry and Endodontics
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• v.42 no.1
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• pp.54-59
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• 2017

Objectives: The purpose of this study was to compare the antibacterial activity of urushiol against Enterococcus faecalis (E. faecalis) to that of NaOCl. Materials and Methods: The canals of thirty two single rooted human teeth were instrumented with Ni-Ti files (ProTaper Next X1, X2, X3, Dentsply). A pure culture of E. faecalis ATCC 19433 was prepared in sterile brain heart infusion (BHI) broth. The teeth were submerged in the suspension of E. faecalis and were incubated at $37^{\circ}C$ for 7 days to allow biofilm formation. The teeth were randomly divided into three experimental groups according to the irrigant used, and a negative control group where no irrigant was used (n = 8). Group 1 used physiologic normal saline, group 2 used 6% NaOCl, and group 3 used 10 wt% urushiol solution. After canal irrigation, each sample was collected by the sequential placement of 2 sterile paper points (ProTaper NEXT paper points, size X3, Dentsply). Ten-fold serial dilutions on each vials, and 100 µL were cultured on a BHI agar plate for 8 hours, and colony forming unit (CFU) analysis was done. The data were statistically analyzed using Kruskal-Wallis and Mann-whitney U tests. Results: Saline group exhibited no difference in the CFU counts with control group, while NaOCl and urushiol groups showed significantly less CFU counts than saline and control groups (p < 0.05). Conclusions: The result of this study suggests 10% urushiol and 6% NaOCl solution had powerful antibacterial activity against E. faecalis when they were used as root canal irrigants.

• Restorative Dentistry and Endodontics
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• v.49 no.2
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• pp.18.1-18.13
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• 2024

Objectives: This study was conducted to evaluate the mechanical properties of relined and non-relined fiberglass posts when cemented to root canal dentin using a conventional dual-cure resin cement or a self-adhesive resin cement. Materials and Methods: Two types of resin cements were utilized: conventional and self-adhesive. Additionally, 2 cementation protocols were employed, involving relined and non-relined fiberglass posts. In total, 72 bovine incisors were cemented and subjected to push-out bond strength testing (n = 10) followed by failure mode analysis. The cross-sectional microhardness (n = 5) was assessed along the root canal, and interface analyses (n = 3) were conducted using scanning electron microscopy (SEM). Data from the push-out bond strength and cross-sectional microhardness tests were analyzed via 3-way analysis of variance and the Bonferroni post-hoc test (α= 0.05). Results: For non-relined fiberglass posts, conventional resin cement exhibited higher pushout bond strength than self-adhesive cement. Relined fiberglass posts yielded comparable results between the resin cements. Type II failure was the most common failure mode for both resin cements, regardless of cementation protocol. The use of relined fiberglass posts improved the cross-sectional microhardness values for both cements. SEM images revealed voids and bubbles in the incisors with non-relined fiberglass posts. Conclusions: Mechanical properties were impacted by the cementation protocol. Relined fiberglass posts presented the highest push-out bond strength and cross-sectional microhardness values, regardless of the resin cement used (conventional dual-cure or self-adhesive). Conversely, for non-relined fiberglass posts, the conventional dual-cure resin cement yielded superior results to the self-adhesive resin cement.

• Restorative Dentistry and Endodontics
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• v.30 no.5
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• pp.409-422
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• 2005

The aim of this study was to identify the bacteria isolated from acute endodontic lesions by cell culture and 16S rDNA sequencing. The necrotic pulpal tissue was collected from 17 infected root canals, which were diagnosed as being either an acute pulpitis or acute periapical abscess. Samples were collected aseptically from the infected pulpal tissue of the infected root canals using a barbed broach and a paper point. The cut barbed broaches and paper points were transferred to an eppendorf tube containing 500 ul of 1 XPBS. The sample solution was briefly mixed and plated onto a BHI-agar plate containing $5\%$ sheep blood. The agar plates were incubated in a $37^{\circ}C$ anaerobic chamber for 7 days. The bacteria growing on the agar plate were identified by 16S rRNA coding gene (rDNA) cloning and sequencing at the species level. Among the 71 colonies grown on the agar plates, 56 strains survived and were identified. In dental caries involving the root canals, Streptococcus spp. were mainly isolated. Actinomyces, Clostridia, Bacteroides and Fusobacteria were isolated in the periapical lesion without dental caries. Interestingly, two new Actinomyces spp. (ChDC B639 and ChDC B631) were isolated in this study. These results showed that there was diversity among the species in endodontic lesions, This suggests that an endodontic infection is a mixed infection with a polymicrobial etiology. These results may offer the bacterial strains for pathogenesis studies related to an endodontic infection.

• Restorative Dentistry and Endodontics
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• v.34 no.2
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• pp.103-112
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• 2009

The purpose of this study was to compare the effect of curing methods of adhesive resins and resin cements in the root canal. Crown portions of 32 single-rooted mandibular premolars were removed. Routine endodontic treatment was done, and 9 mm deep post spaces were prepared within root canals. No.3 FRC Postec posts (Ivoclar-Vivadent AG, Liechtensteih) were cemented in the post spaces by self-(SC) or light-curing (LC) using two dual-cured adhesives (Adper Scotchbond multi-purpose plus and Exite DSC )and resin cements (RelyX ARC and Variolink II). They were assigned to 4 groups (n=8): R-SC, R-LC, V-SC, V-LC group. After stored in distilled water for 24 hours, each root was transversally sectioned with 1.5 mm thick and made three slices. The specimens were subjected to push-out test in a universal testing machine (EZ Test, Shimadzu Co., Japan) with a crosshead speed of 1 mm/min. The data were analyzed with repeated ANOVA and one-way ANOVA. Also the interface of post-resin cement and resin cement-canal wall of each group was observed under FE-SEM. When fiber posts were cemented into the root canal using total-etch adhesives, the bond strength and adaptation between post and root canal dentin was affected by curing method. Self-cure of adhesives and resin cements showed higher bond strength and closer adaptation than light-cure of them.