Assessment of root canal morphology of maxillary and mandibular second molars in the Iranian population using CBCT.

BACKGROUND: Inability to efficiently clean all root canals due to the complex anatomy of the root canal system is a common cause of endodontic treatment failure. OBJECTIVES: This study aimed to assess the root canal morphology of the maxillary and mandibular second molars using cone-beam computed tomography (CBCT). MATERIAL AND METHODS: This descriptive study evaluated 502 CBCT scans taken in the years 2014-2017. The number of roots and canals, type of canals according to the Vertucci classification, presence of maxillary second molars with 2 palatal roots, and C­shaped canals in the maxillary and mandibular second molars were evaluated on CBCT scans separately by a radiologist and 2 endodontists. The data was analyzed using SPSS via descriptive statistics, Fisher's exact test, the independent samples t-test, and the χ2 test. All the analyses were performed with a confidence level of 95%. RESULTS: The majority of the palatal, mesiobuccal and distobuccal roots of the maxillary second molars had 1 single canal of Vertucci type I; 21.5% of the mesiobuccal roots had a second mesiobuccal canal (p = 0.05). CONCLUSIONS: Two-rooted mandibular second molars and 3-rooted maxillary second molars were the most common in our study population. Cone-beam computed tomography as a non-invasive and highly accurate imaging modality is efficacious for the detection of additional roots and C­shaped canals.

Effect of Nd:YAG and Diode Lasers on Apical Seal of Root Canals Filled with AH Plus and Mineral Trioxide Aggregate-Based Sealers.

OBJECTIVES: Laser irradiation, as an adjunct to root canal preparation, may increase the success rate of endodontic treatments. This study aimed to assess the effect of neodymium-doped yttrium aluminum garnet (Nd:YAG) and diode lasers on the apical seal of the root canals filled with AH Plus® and mineral trioxide aggregate (MTA)-based sealers. MATERIALS AND METHODS: This in-vitro experimental study was conducted on 96 single-rooted, single-canal extracted human teeth with closed apices. The root canals were prepared by using ProTaper® rotary instruments and were randomly divided into six groups (n=16): 940-nm diode laser and AH Plus® sealer (group 1), Nd:YAG laser and AH Plus® sealer (group 2), AH Plus® sealer (group 3), 940-nm diode laser and MTA-based sealer (group 4), Nd:YAG laser and MTA-based sealer (group 5), MTA-based sealer (group 6), as well as positive and negative control groups. A bacterial leakage model was used for microleakage assessment. Qualitative assessment was done by using a scanning electron microscope (SEM). Data were analyzed by two-way analysis of variance (ANOVA) at the significance level of 0.05. RESULTS: There were statistically significant differences between the experimental and control groups (P=0.002). The laser-treated groups showed a lower apical microleakage compared to the non-laser-treated groups, although the difference was not statistically significant (P>0.05). No significant differences were noted between the two lasers in terms of the apical microleakage, irrespective of the type of sealer (P>0.05). CONCLUSIONS: Laser irradiation, as an adjunct to root canal preparation, has no significant effect on the level of apical microleakage.

The Effect of Canal Preparation with Four Different Rotary Systems on Formation of Dentinal Cracks: An In Vitro Evaluation.

INTRODUCTION: Endodontic rotary systems may result in dentinal cracks. They may propagate to vertical root fracture that compromises the outcome of endodontic treatment. This study aimed to compare Neolix and Reciproc (single-file systems), Mtwo and ProTaper (conventional rotary systems) in terms of dentinal crack formation in root canal walls. METHODS AND MATERIALS: This in vitro study was conducted on 110 extracted human single-rooted teeth. The teeth were randomly divided into four experimental groups (n=25) for root canal preparation with Neolix, Reciproc, Mtwo and ProTaper systems and two control groups (n=5). The first control group underwent root canal instrumentation with hand files while the second control group received no preparation and was only irrigated. After instrumentation, root canals were horizontally sectioned at 3, 6 and 9 mm from the apex and inspected under a stereomicroscope under 12× magnification for detection of cracks. The data were analyzed using Chi-square, GEE test and Bonferroni tests (P<0.05). RESULTS: No crack was found in the control groups. All rotary systems caused dentinal cracks. ProTaper, Reciproc, Mtwo and Neolix caused cracks in 92%, 80%, 68% and 48% of samples. ProTaper caused significantly more cracks than Neolix and Mtwo (P<0.05). No significant differences were noted between other groups (P>0.05). CONCLUSION: All rotary systems cause dentinal cracks and it is significantly different in apical, middle and coronal third of the root. Neolix appears to be a suitable alternative to other rotary systems since use of this single-file system saves time and cost and minimizes trauma to dentinal walls.

Antibacterial Efficacy of Calcium Hydroxide and Chlorhexidine Mixture for Treatment of Teeth with Primary Endodontic Lesions: A Randomized Clinical Trial.

INTRODUCTION: This study compared the root canal microbial count of necrotic teeth after irrigation with 6% sodium hypochlorite (NaOCl) (single session treatment) and two-session root canal treatment with two-week application of calcium hydroxide (CH) mixed with 0.2% chlorhexidine (CHX) as intracanal medicament. METHODS AND MATERIALS: In this randomized clinical trial, single-rooted necrotic teeth were divided into two groups. Root canal was irrigated with 2 mL of 6% NaOCl in one group, and a mixture of 0.2% CHX and CH powder as an intracanal medicament for two weeks, in the other group. Root canal samples were obtained before and after the intervention and number of colony forming units (CFUs) was counted in each phase. RESULTS: The reduction of Enterococcus faecalis CFU was not significantly different between the two groups (P=0.233) but the CFU of aerobic and anaerobic bacteria was significantly lower in CH+CHX group (P<0.001). CONCLUSION: Two-week application of CH+CHX caused significant reduced the aerobic, anaerobic and E. faecalis colony counts. Thus, it may be beneficial to carry out primary root canal treatment of necrotic teeth with endodontic lesions in two sessions with intracanal medicaments to achieve predictable results.

Cone-Beam Computed Tomography Study Of Crown Dilaceration With a Talon Cusp in an Unerupted Permanent Maxillary Tooth.

This article describes a rare case of crown dilaceration with a talon cusp in an unerupted permanent maxillary central incisor. Our patient was a 7-year-old boy with a history of trauma to his primary maxillary teeth (#51 and 52), at 3 years of age complaining of failure of eruption of tooth #11. Periapical radiography showed incomplete formation of tooth root #11 and more superior position of tooth bud #11 relative to tooth bud #12. A cone-beam computed tomography was ordered, which revealed crown dilaceration with a talon cusp in tooth bud #11. The patient was scheduled for follow-up at 6 months.

Cytotoxic effect of a new endodontic cement and mineral trioxide aggregate on L929 line culture.

INTRODUCTION: The aim of this study was to compare the cytotoxicity of Mineral Trioxide Aggregate (MTA) and a New Endodontic Cement (NEC) on L929 mouse fibroblasts. MATERIALS AND METHODS: Different dilutions (Neat, 1/2, 1/10, 1/100) of fresh and set materials placed adjacent flasks of L929 in DMEM medium. Cellular viability was assessed using MTT assay in three time intervals (24, 48, and 72 h after mixing). Differences in mean cell viability values between materials were assessed by using the One-way ANOVA and Bonferoni post-test. Optical microscopic analysis of morphology of the untreated control and the cement-treated cell cultures were carried out in all experimental periods. RESULTS: It was indicated that there was not a significant difference in cytotoxicity among the materials of test and between them and the control group. However, there was a statistically significant difference between different time intervals within each group (P< 0.05) and between different concentration of test materials (P<0.05). In all samples, set materials showed better viability than fresh ones. CONCLUSION: According to results of this study, NEC and MTA have similar cytotoxic effect on L929 cell culture.