Evaluation the stress distribution in root canals by 3D finite element analysis after the materials used in reattaching the vertically root fractured fragments.

The aim was to evaluate the effect of stress distribution on vertical, horizontal, and oblique forces on the tooth model after reattaching the fragments of the maxillary incisor with vertical root fracture (VRF) using different materials, by 3D finite element analysis (FEA). Tooth with a root canal, spongious, and cortical bone models were designed. VRF was modeled on a tooth with 4 different re-attachment models: Group 1: dual-cure cement (DC)+fiber reinforced composite (FRC), Group 2: DC+polyethylene fiber, Group 3: DC+glass fiber, and Group 4:DC. 100 N force was applied in 3 different directions. Maximum principal stresses (σmax) of dentin, and re-attachment materials were evaluated on colored images. The highest σmax values ​​were on the repair materials under vertical forces for Groups 1 and 4, respectively; Groups 2 and 3 showed similarity. The highest σmax values in repair materials under horizontal and oblique forces were observed in Group 3 however the lowest σmax values in repair materials under oblique and horizontal forces were observed in Group 1. The stress values ​​on repair materials gradually increased respectively starting from horizontal to vertical. As the elasticity modulus of the repair materials increased, the stress values ​​on root dentin increased. Through all force directions, except vertical forces, lower stress values were observed with FRC. The fracture resistance was bigger when using solely FRC or dual-cure resin cement in comparison to fiber-supported designs. Adding polyethylene fiber to re-restorations decreased stress values ​​compared to glass fiber addition. Therefore, when adding fibers, polyethylene fiber will be advantageous.

Evaluation of Different Root Canal Obturation Techniques in Internal Root Resorption of Three-Dimensional Printed Teeth Manufactured Using Computer Software.

The objective of this study was to evaluate and compare the filling ability of various root canal obturation techniques on the internal root resorption (IRR) cavities of replicated tooth samples manufactured using computer software and a three-dimensional (3D) printer. Orthographic images and root structures of a healthy upper maxilla central incisor in determined volumes and sizes were drawn as a prototype with the aid of computer software. Using the same software, an IRR defect was also modeled. These two images were then transferred to the AutoDesk Fusion 360 3D modeling program (AutoDesk, San Rafael, CA) for meshing. Afterward, the tooth model was transferred to a 3D modeling and prototyping program (RhinoCeros 3D; Robert McNells & Assoc., New York) and printed on a 3D printer. Eighty replicas with IRR were manufactured and divided into four groups (n = 20 per group) according to the obturating techniques as follows: Group 1: Cold lateral compaction (CLC), Group 2: Core Carrier System (GuttaCore), Group 3: Injectable Cold Filling (GuttaFlow® BioSeal), and Group 4: Continuous Wave Obturation System (Elements Free). After root canal filling, replicas were scanned with a high-resolution micro-computed tomography system (SkyScan 1172; Bruker-microCT, Kontich, Belgium), data regarding voids (unobturated areas) inside the IRR defects were statistically analyzed using nonparametric Kruskal-Wallis tests. A pairwise comparison between the tested groups showed that Groups 3 and 4 had significantly fewer voids compared with Groups 1 and 2 in IRR defects (p < 0.05). Group 1/Group 2 and Group 3/Group 4 had similar results in terms of voids and there were no statistically significant differences (p > 0.05). The injectable cold filling system (GuttaFlow BioSeal) and the injectable continuous wave obturation system (Elements Free) successfully obturated the pathological IRR irregularities when compared with CLC and core carrier (GuttaCore) systems.

Comparison of Walking-Bleaching and Photon-Initiated Photoacoustic Streaming Techniques in Tooth Color Change of Artificially Colored Teeth.

Background and objective: The aim of this study is to compare the bleaching effect of photon-induced photoacoustic streaming (PIPS) using carbamide peroxide or sodium perborate-20% hydrogen peroxide (H2O2) compared with walking-bleaching techniques using sodium perborate-20% H2O2 or carbamide peroxide without PIPS on artificially colored teeth. Materials and methods: Root canal treatments of 85 extracted human maxillary central incisors were completed and artificially stained using sheep's blood. Teeth were randomly grouped into five groups according to the bleaching techniques to be tested: Group 1: walking bleaching with carbamide peroxide; Group 2: walking bleaching with sodium perborate-20% H2O2; Group 3: PIPS+carbamide peroxide; Group 4: PIPS+sodium perborate-20% H2O2; and Group 5: control. Experimental specimens were bleached for 3 weeks. Buccal surfaces of the crowns were used for spectrophotometric measurements, limited with a 7-mm external diameter rounded strip, before bleaching and on days 7, 14, and 21. The total change in color (ΔE*) were analyzed with Welch's ANOVA at a significance level of p = 0.05 and Tamhane post-hoc test was used for multiple comparisons. Results: Starting from the second week, Group 4 showed significantly better bleaching effect compared with the other groups (p < 0.05). The other experimental groups also have bleaching effects, but there was no statistically significant difference between Group 1, Group 2, and Group 3 (p > 0.05). Conclusions: Sodium perborate-20% H2O2 activated with PIPS gave a bleaching effect superior to that of walking-bleaching techniques or PIPS using with carbamide peroxide.

Evaluation of microleakage of root canal fillings irradiated with different output powers of erbium, chromium:yttrium-scandium-gallium-garnet laser.

This study evaluated the root canal seal achieved by irradiation with an erbium, chromium:yttrium-scandium-gallium-garnet laser, and the optimal output power to remove debris and the smear layer were determined. One hundred mandibular premolar teeth were prepared and divided into four groups. Group 1 was not lased but was irrigated with 5 mL of 5.25% NaOCl and 5 mL of 17% ethylenediaminetetraacetic acid. Group 2 was irradiated at a panel setting of 1 W, group 3 at 2 W and group 4 at 2.5 W, with a 50% water level and 48% air-cooling level. Root canals were obturated by cold lateral compaction, and apical microleakage was measured using a fluid filtration model. The remaining debris and smear layer were evaluated via scanning electron microscopy. Statistically significant differences were detected between groups. Irradiation at 1 and 2 W using an erbium, chromium:yttrium-scandium-gallium-garnet laser produced a seal superior to that of the other treatments.

Comparison of root canal transportation induced by three rotary systems with noncutting tips using computed tomography.

OBJECTIVE: The purpose of this study was to compare the shaping ability (apical transportation and straightening) of 3 nickel-titanium rotary instruments (ProTaper Universal, Hero 642 Apical, FlexMaster) with noncutting tips in curved root canals of extracted human teeth using cone beam computed tomography (CBCT). STUDY DESIGN: Sixty mesiobuccal root canals of maxillary molars with curvatures of 25° to 47° were equally divided into 3 groups and embedded in silicone impression material. The root canals were scanned using CBCT (Next Generation i-CAT) and after scanning working length was determined with a hand file to preserve the original curvature. After preparation, teeth were placed into their original positions on the silicone impression material and postinstrumentation scans were performed using the same parameters (4-cm field of view at 0.125-mm voxel). Pre- and postinstrumentation images obtained from root cross-sections located 2, 3, and 4 mm above the apical foramen were compared using Adobe Photoshop software. Transportation was measured by superimposition of final and initial images. Any distance (mm) between prepared and anatomic canal centers was defined as apical transportation. Canal curvatures were measured before and after instrumentation using computed tomography and images were exported to ImageJ software. Differences in the degree and radius of curvature were regarded as straightening. Data were analyzed by ANOVA. RESULTS: Mean transportation values were 0.10 ± 0.03 mm for ProTaper Universal, 0.09 ± 0.03 mm for Hero 642 Apical, and 0.07 ± 0.02 mm for FlexMaster, and the differences were not significant. Mean values for straightening among the groups were not significantly different (P > .05). The performances of all instruments were similar. CONCLUSION: Apical transportation occurred with all the instruments despite their noncutting tips.

Detection of vertical root fractures by using cone beam computed tomography with variable voxel sizes in an in vitro model.

INTRODUCTION: The aim of this study was to compare the diagnostic accuracy of cone beam computed tomography (CBCT) scans with different voxel resolutions in the detection of simulated vertical root fracture (VRF). METHODS: Sixty teeth, 30 with root fractures and 30 without, were examined through i-CAT tomography at 4 different voxel resolutions (0.125, 0.2, 0.3, 0.4 mm). Three observers scored the presence of VRF in all modalities. Sensitivity, specificity, likelihood ratio, and accuracy were calculated for each modality. RESULTS: Chi-square statistical analysis showed no significant difference among the resolutions or observers. However, positive likelihood ratio values of 24.5 for a 0.125-mm voxel, 24.25 for a 0.2-mm voxel, 13.2 for a 0.3-mm voxel, and 13 for a 0.4-mm voxel were found. Accuracy results confirmed the likelihood ratios as 0.97, 0.96, 0.93, and 0.92, respectively. CONCLUSIONS: CBCT scans were reliable in detecting simulated VRF, and a 0.2-mm voxel was the best protocol, considering the lower x-ray exposure and good diagnostic performance.

Diagnosis and treatment of endodontically treated teeth with vertical root fracture: three case reports with two-year follow-up.

INTRODUCTION: Vertical root fracture (VRF) is an important threat to the tooth's prognosis during and after root canal treatment. Often the detection of these fractures occurs years later by using conventional periapical radiographs. However, recent studies have addressed the benefits of computed tomography to diagnose these problems earlier. Accurately diagnosed VRFs have been treated by extraction of teeth, with minimal damage to the periodontal ligament, extraoral bonding of fractured segments with an adhesive resin cement, and intentional replantation of teeth after reconstruction. METHODS: The 3 case reports presented here describe the diagnosis and treatment of vertically fractured teeth that had been previously treated endodontically. Cone-beam computed tomography (CBCT) was used for diagnostic imaging to detect VRFs. Vertically fractured roots were carefully extracted and extraorally treated by using a self-etching dual-cure adhesive resin cement, and intentional replantations were performed after reconstruction. RESULTS: After a mean follow-up period of 2 years, the teeth were asymptomatic. There was no clinical ankylosis, and diagnosis by using CBCT scans showed reduced periapical radiolucency. CONCLUSIONS: Extraoral bonding of fractured segments and intentional replantation of teeth after reconstruction provide an alternative treatment to extraction, especially for anterior teeth. Computed tomography-assisted VRF diagnosis is helpful in detecting fractures; however, higher-resolution tomography units providing better image quality would be a better choice for improved visualization of these fractures.

Detection of vertical root fractures of different thicknesses in endodontically enlarged teeth by cone beam computed tomography versus digital radiography.

INTRODUCTION: This study was performed to compare the accuracy of cone beam computed tomography (CBCT) scans and digital radiography (DR) for detecting simulated vertical root fractures (VRFs) with different thicknesses in extracted human teeth. METHODS: Eighty teeth were endodontically prepared and divided into 4 groups, 3 experimental and 1 control. The teeth in experimental groups were artificially fractured and fixed together with different thicknesses of 0.2 mm (0.2-mm VRF group), 0.4 mm (0.4-mm VRF group), and smaller than 0.2 mm (crack group). Teeth in control group were kept intact. Three observers evaluated the DR and CBCT images in terms of accuracy for VRF detection. RESULTS: No significant differences in detection rate were noted among the observers (P > .5). The overall accuracy for detecting VRFs was significantly higher for CBCT scans compared with DR (P < .001). CBCT scans were more accurate in detecting 0.2-mm VRFs (70%) and 0.4-mm VRFs (90%) as compared with DR (43.3% and 60%, respectively). CONCLUSIONS: The results of this study showed that CBCT scans are effective for detecting VRFs of different thicknesses.

Outcome of root canal treatment using Soft-Core and cold lateral compaction filling techniques: a randomized clinical trial.

AIM: The purpose of this clinical and radiographic investigation was to evaluate the treatment outcomes of endodontically treated teeth obturated with Soft-Core versus cold lateral compaction. METHODS AND MATERIALS: A total of 98 teeth were endodontically prepared using the Quantec LX rotary system with a crown-down pressureless technique and obturated with either Soft-Core or cold lateral compaction. The outcome of treatments were evaluated clinically and radiographically by two blinded evaluators after three years. Statistical analysis was performed using an unpaired t-test and the Mann Whitney test at the level of significance set at 95%. RESULTS: Regardless of the periapical status of the teeth, no statistically significant difference was found between the two obturation techniques (p > 0.05). The Kappa value for the interobserver agreement was 0.73. CONCLUSION: Within the limits of the study, it is concluded the Soft-Core obturation technique did not result in a significantly different treatment outcome when compared with cold lateral compaction after three years. Further investigations should be carried out on the Soft-Core technique. CLINICAL SIGNIFICANCE: Using the Soft-Core system reduced working time, and the difference was found to be statistically different (p = 0.00056) from the working time required for cold lateral compaction. This reduction in canal filling time holds the potential for cost savings for clinicians while maintaining the quality of the clinical outcome.

A practical method for determining pubertal growth spurt.

INTRODUCTION: It is important to evaluate skeletal maturation in orthodontic treatment. Hand-wrist and cervical maturation stages have been shown to be correlated with skeletal growth changes during puberty. The cervical vertebrae have 6 maturation phases, whereas the medial phalange of the third finger has 5 stages; a modified version has 6 stages. The purpose of this study was to determine the correlation of the cervical vertebrae maturation index with the modified medial phalange index. METHODS: Lateral cephalometric and left-hand medial phalange radiographs of 150 males between the ages of 9 and 19 who were referred for orthodontic treatment were examined. RESULTS: The 6 modified medial phalange stages were found to correlate with the 6 cervical vertebral maturation stages. CONCLUSIONS: Because cervical vertebrae stage is a reliable maturation indicator, the medial phalange of the third finger can be used instead to assess a subject's skeletal maturation.