Effect of modified NaOCl irrigation solution on bond strength of bioceramic-based root canal sealer to dentin.

INTRODUCTION: Biomechanical shaping and hermetic obturation play an important role in the success of root canal treatment. AIMS AND OBJECTIVES: This study aimed to examine the bonding strength of the bioceramics sealer to the dentin surface with or without core when irrigated with conventional NaOCl, modified NaOCl, EDTA, MTAD and distilled water. Materials and Methods: 120 single-root teeth dissected at the level of enamel-cement junction were grouped according to different irrigation and filling techniques; each group consisted 12 teeth. After final irrigation with NaOCl, modified NaOCl, EDTA, MTAD or distilled water, the samples were filled with bioceramic sealer. Samples with or without core were obtained; then 2 mm-thickness horizontal sections were made in the middle coronal and the middle third of the dentin and subjected to a push-out test. Results: Although bonding strength was the lowest when modified NaOCl was used, the highest bonding strength was reported with NaOCl in the present study. Bond strength values determined in the coronal third were found to be high compared to the middle third, although the difference was not statistically significant. In the groups without core, the resistance of the connection was found to be higher than in the core with a filled root canal (P < 0.05). CONCLUSION: Because the connection value of the bioceramic root canal sealer to the dentin using modified NaOCl was lower,it is recommended not to use the monoblock effect in canal filling in cases anticipated to be problematic. It would be more appropriate to use bioceramic paste without core in cases where a high attachment to dentin is desired.

Effect of retreatment instruments on microcrack formation: a microcomputed tomography study.

INTRODUCTION: The purpose of this study was to compare the occurrence of microcracks in teeth prepared with different retreatment systems using microcomputed tomography (micro-CT). METHODS: Forty-two freshly extracted mandibular premolar teeth were used. The root canals were instrumented with stainless steel K-files to an apical size of 35/.02 using the balanced-force technique and were obturated using the passive compaction technique. The specimens were divided into 3 experimental groups according to retreatment system used (n = 14): ProTaper Universal retreatment (PTUR), Mtwo retreatment (MTR), or D-RaCe retreatment (D-RC) systems. Each specimen was scanned using a high-resolution micro-CT system before instrumentation, after obturation, and after the removal of the filling material. The images were evaluated, and the presence of microcracks was recorded. RESULTS: The PTUR system demonstrated the highest percentage, while MTR and D-RC retreatment systems resulted in similar numbers of microcracks. CONCLUSIONS: Clinicians should be aware that all retreatment systems may cause microcracks.

Apical transportation during removal of root canal filling with different retreatment systems.

INTRODUCTION: This study aimed to compare apical transportation during retreatment using ProTaper Universal retreatment (PTUR), Mtwo R and D-RaCe instruments in curved root canals. METHODS: 36 extracted mandibular molar teeth with curved mesiobuccal roots were selected. The teeth were embedded into acrylic blocks. The blocks were fixed on the experimental setup. After determining the working length (WL), mesiobuccal canals were prepared with ProTaper Universal rotary instruments to size F1 (20/0.06). After the obturation, the teeth were randomly divided into groups; the PTUR files were used as D1 (30/0.09) for coronal third and D2 (25/0.08) at WL. Mtwo R files, R1 (15/0.05) and R2 (25/0.05) were used at WL. D-RaCe files were used as DR1 (30/.10) in cervical third and DR2 (25/0.04) at WL. Image J analysis software was used to measure the apical transportation. Differences between the 3 groups were analyzed with a 1-way ANOVA or Kruskal-Wallis tests. RESULTS: There was no significant difference between groups in the apical transportation in either the mesiodistal (p = 0.166) or buccolingual (p = 0.518) direction. Among the 3 groups, the apical transportation was the greatest in the D-RaCe group. CONCLUSIONS: It can be concluded that all retreatment systems caused a similar level of apical transportation.

Sealing ability of lateral compaction and tapered single cone gutta-percha techniques in root canals prepared with stainless steel and rotary nickel titanium instruments.

OBJECTIVES: The aim of this study was to evaluate the sealing ability of lateral compaction and tapered single cone gutta-percha techniques in root canals prepared with stainless steel and rotary nickel titanium root canal instruments by fluid filtration method. STUDY DESIGN: The root canals were prepared with stainless steel (SS) and nickel titanium (NiTi) instruments. The canals prepared with SS were obturated with lateral compaction technique using .02 tapered cones and the canals prepared with NiTi instruments were obturated with lateral compaction technique using .02 tapered cones or 06 tapered single cones. The amount of leakage was evaluated by fluid filtration model. The results were statistically analyzed with one-way ANOVA. RESULTS: The group prepared with NiTi instruments and filled with lateral compaction technique showed significantly less coronal leakage than the group prepared with SS instruments and filled with lateral compaction technique (p<0.05). There was no statistically difference between apical leakages of groups (p>0.05). CONCLUSIONS: Obturation with lateral compaction of gutta-percha provides a superior coronal seal whilst canal instrumentation with engine-driven NiTi files reduces the extent of microleakage in root canals when compared with stainless steel hand instruments. Tapered single cone technique was comparable with lateral compaction technique because of easier application. Key words:Apical leakage, coronal leakage, lateral compaction technique, single cone technique.