Third Of Root Research Articles

A micro-CT analysis of radicular dentine thickness in mandibular first premolars presenting C-shaped root canals: Identification of potential danger zones.

To describe the radicular dentine thickness in mandibular first premolars presenting C-shaped root canals, to identify the canal walls with less thickness as potential danger zones. In addition, to describe the internal and external anatomical characteristics of these teeth and associate them with the dentine thickness. A total of 70 mandibular first premolars presenting C-shaped root canals were examined. Their internal morphology was analysed using Vertucci's and Fan's criteria, and their external morphology was analysed using the ASUDAS score. Besides, the dentine thickness around the root canals was two/three-dimensionally determined at five root planes and quantified in the distal and the mesial aspects. According to Fan's, ASUDAS, and Vertucci's classifications, the most common canal configurations were category C3, grade 3, and type V, respectively. In Vertucci's type III anatomy, the mesial root wall of the lingual canal showed significantly less dentine thickness than the distal wall in the middle plane (p=.031). Similarly, in Vertucci's type V anatomy, significantly less dentine thickness was observed in the mesial root wall of the buccal and lingual canals in the middle plane (p<.001) and the buccal canal in the middle-apical plane (p=.014) than the distal root wall of these canals. In teeth with ASUDAS grade 3 and 4 scores, significantly less dentine thickness was observed in the mesial in comparison with the distal root wall of these canals. These differences were demonstrated in the middle and middle-apical planes (p<.001) of grade 3 teeth and the middle-apical plane (p<.001) of grade 4 teeth. In these root planes, the Ver1-AS3 and VerV-AS3 combinations presented a 4-times greater risk of presenting walls with a critical dentine thickness of 0.6mm (odds ratio [OR]=4, p=.025) than the combinations Ver1-AS2, VerV-AS2, VerV-AS4, and VerIII-AS3. The root canal system configuration of mandibular first premolars with C-shaped canals showed a wide range of anatomical variations. The lowest dentine thickness was located in the mesial wall of the canals in the middle and apical root thirds of Vertucci's type III and V anatomies and in teeth with deep radicular grooves scored as ASUDAS grades 3 and 4. In the middle and middle-apical planes, the presence of the combinations Ver1-AS3 and VerV-AS3 showed a high risk of presenting a critical dentine thickness of 0.6mm. Therefore, these root canal walls with less dentine thickness represent potential instrumentation danger zones in mandibular first premolars with C-shaped canals.

Comparative evaluation of root canal dentin erosion after using different smear layer removing solutions for root canal irrigation by scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDS): An in-vitro study

Objective: To evaluate and compare the effect of different final irrigating solutions (17% EDTA, Smear Clear, QMix and BioPure MTAD) on root canal dentin erosion in the coronal, middle and apical third of root by Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS). Materials and Methods: A total of 105 recently extracted mandibular premolars were taken and decoronated to a standardized root length of 12mm. They were prepared using ProTaper system up to size F3. Initial rinse was done with sodium hypochlorite. After completion of root canal preparation, all root canals were subjected to final irrigation protocol. Group 1 was irrigated with 17% EDTA for 1 min. Group 2 was irrigated with Smear Clear for 1 min. Group 3 was irrigated with QMix for 1 min. Group 4 was irrigated with MTAD for 5 min. Group 5 was irrigated with distilled water. Out of 21 samples in each group, 10 were analysed by SEM and 11 were analysed by EDS. Results: The results of the SEM analysis revealed that the use of 17% EDTA and Smear Clear resulted in significantly more erosion than the use of QMix and MTAD. No statistically significant difference was observed at the coronal, middle and apical thirds in the amount of dentin erosion. The results of EDS analysis revealed that all treatment groups significantly decreased calcium content in comparison to control group. However, no significant difference was observed among EDTA, Smear Clear, Qmix and MTAD in decreasing calcium levels in dentin. Conclusion: BioPure MTAD and QMiX cause negligible dentin erosion and thus can be used as alternative final irrigating solutions after sodium hypochlorite instead of EDTA and Smear Clear.

Location of MMPs in human radicular dentin and the effects of MMPs inhibitor on the bonding stability of fiber posts to radicular dentin

This study explored the location of MMP-2, -3, -8 in human root dentin and the inhibition of EGCG/EGCG-3Me on dentin-originated collagen proteases activities. Also, the study evaluated EGCG/EGCG-3Me modified etch-and-rinse adhesives (Single Bond 2, SB 2) for their bonding stabilities to intraradicular dentin. Immunostaining and liquid chip analysis demonstrated that MMP-2 and MMP-8 are widely distributed in root dentin while MMP-3 shows a higher fluorescence intensity in the middle and apical third of the root. The contents of MMP-2, -3 and -8 varies in different locations of human tooth root and MMP-2 has the highest content than MMP-3 and MMP-8 at each third of teeth root. Both EGCG and EGCG-3Me showed an inhibitory effect on the root dentin-derived MMPs in a concentration dependent manner (P < 0.05) and the inhibitory activity of EGCG-3ME was stronger than that of EGCG at the same concentration (P < 0.05). EGCG and EGCG-3Me were incorporated separately into the adhesive SB 2 at concentrations of 200, and 400 μg/mL respectively. The immediate push-out strength of SB 2 was not compromised by EGCG/EGCG-3Me modification. EGCG/EGCG-3Me modified adhesive had higher push-out strength than SB 2 after thermocycling, showing no correlation with concentration.

Glass fiber posts relining: can composite opacity influence retention to root canal dentin?

This study aimed at evaluating the influence of glass-fiber post (GFP) relining with composites of different opacities on resin cement layer thickness (CLT), bond strength (BS) to root dentin, and resin cement degree of conversion (DC%). Standardized roots of 52 bovine incisors had their canals prepared and were distributed into 4 groups (n = 10 for CLT and BS; n = 3 for DC%) according to the post used: WP3 (Control)-Whitepost DC3; groups DE, EN and TR-Whitepost DC0.5 relined, respectively, with dentin, enamel, and translucent shade composites. After cementation, specimens were sectioned into six 1.0mm-thick discs that were submitted to push-out BS test. CLT and failure pattern were evaluated using a stereomicroscope and DC% by micro-Raman spectroscopy. Data were analyzed by two-way ANOVA and Tukey test (α = 0.05). The control group showed greater CLT than all relined groups (p < 0.05), which did not differ from each other (p > 0.05). Groups relined with low opacity composites (TR; EN) showed the highest BS and DC% means (p < 0.05). BS was not different among root thirds (p > 0.05), while DC% decreased from cervical to apical third (p < 0.05). Adhesive failures between cement and dentin were predominant, except for group DE with frequent mixed failures. It could be concluded that composite opacity did not influence CLT, which was thinner when GFP were relined and that relining GFP with lower opacity composites led to higher BS and DC%.

How the translucency of direct anatomic fiber posts affects the bond strength and microhardness of a self-adhesive luting agent in flared roots.

To evaluate the influence of the composite resin translucency used in direct anatomic fiber posts on the bond strength (BS) and microhardness (VHN) of a luting agent into flared roots. The root canals of 70 single-rooted premolars were endodontically treated and prepared to simulate an oversized root canal. Prior to post cementation, composite resins with varying translucency (high translucent, HT; medium translucent, MT; high opacity, HO) were placed around the fiber posts to create anatomic fiber posts. The attenuation profile (%) of light passing either through the post or through the anatomic posts (n = 8) was obtained prior to the cementing procedures. A positive control group (PC) in which a prefabricated fiber post (PFP) with the diameter compatible with the root canal was cemented and a poorly adapted fiber post (negative control group, NC) were also evaluated. For both tests, the data were subjected to 2-way ANOVA and Bonferroni tests (α = 0.05). A more severe light attenuation through the post at the cervical (P < .001) and medium (P < 0.001) thirds was noted when less translucent composite resin surrounded the anatomic post. HO groups showed lower BS (P = .009) and VHN (P < .001) values than the other groups, regardless of root third. No significant difference in BS values was noted between PC and HT groups. The use of a more translucent composite resin in anatomic fiber posts increased the microhardness and bond strength of a dual polymerization self-adhesive RLA compared to the use of MT and HO composite. A well-adapted PFP showed the highest adhesive and mechanical behavior. Clinicians should choose more translucent composite resins to create direct anatomic fiber posts to be cemented in flared root canals. That choice may allow improved mechanical properties of self-adhesive RLA and higher bond strength to the root canal as a consequence.

Age and experience with dental operating microscope: Do these factors influence on the post space preparation and adhesion of glass fiber posts?

This study evaluated the influence of operator's age and experience with dental operating microscope (DOM) on the cleaning of post space walls and on bond strength of glass fiber posts associated with self-adhesive resin cement. Sixty bovine roots were selected. Root canal preparation was performed and roots were filled using gutta-percha/AH Plus. For post space preparation, specimens were divided into four groups (n=15), according to operator's age and the use of DOM: (1) ≥40 years; (2) ≥40 years with magnification; (3) <40 years; (4) <40 years with magnification. Next, a high-speed bur of the post system and torque-controlled round burs were used for cleaning of post space. Five roots in each group were evaluated for the degree of cleanliness under a stereo microscope using a scoring system. In the remaining 10 specimens from each group, glass fiber posts were cemented with RelyX U200. Two slices (1 ± 0.1 mm) prepared on each root third of all specimens were evaluated by push-out analysis. The scoring system was analyzed using Kruskal-Wallis and push-out data using ANOVA. Significance level was set at 5%. No significant difference was observed in cleaning scores among groups (p > .05). There was no significant difference when comparing the groups and the root thirds (p > .05). The adhesive failure between dentin, cement, and post predominated in all groups. Operator's age and experience with DOM did not influence the cleanliness of root canal walls or the bond strength of glass fiber posts associated with self-adhesive resin cement for post space preparation. RESEARCH HIGHLIGHTS: Although magnification is considered part of Endodontics, little is known about the variables associated. Operator's age and experience with microscope on cleaning of canals and on push-out of posts with self-adhesive resin cement were evaluated.

Odontoblast apoptosis and intratubular mineralization of sclerotic dentin with aging

ObjectivesThe aims of the study were to evaluate the roles of odontoblast apoptosis in the progression of tubular sclerosis of teeth from donors at different ages and assess its correlation to chemical composition and mechanical properties. Design: Healthy human teeth were obtained and divided into young (age ≤ 25, n = 12) and old (age ≥ 60, n = 12) groups. Odontoblasts were counted with standard hematoxylin and eosin staining. Odontoblast apoptosis within dentinal tubules was determined by cleaved caspase‐3 immunostaining. Teeth in each group were evaluated by dynamic nanoindentation and energy-dispersive X-ray spectroscopy (EDS). ResultsThe number of odontoblasts decreased significantly with age. The most prominent change occurred in the apical third of roots. Odontoblastic apoptosis was visualized within dentinal tubules. The apoptosis staining fraction was significantly higher in the outer and inner dentin of old teeth when compared with young teeth (p < 0.05). EDS showed increased calcium content in peritubular dentin but a decrease in the intertubular dentin with increasing age. Scanning based nanoindentation showed that the old intertubular dentin exhibited a significantly higher elastic modulus. ConclusionsOdontoblast apoptosis, starting at the cell extension in dentinal tubules and proceeding from outer to inner dentin, contributes to the stoichiometric Ca/P ratio in peritubular dentin, which is potentially responsible for intratubular mineralization due to an imbalance of calcium and phosphorous ions.

Effect of root perforation repair with mineral aggregate-based cements on the retention of customized fiberglass posts.

The purpose of this study was to investigate whether the root perforation repair with mineral aggregate-based cements affects the retention of customized fiberglass posts to bovine intraradicular dentin. Sixty-four bovine mandibular incisors had their root canals endodontically treated and prepared for fiberglass posts luting. Teeth were randomly distributed into four groups (n = 16), according to the cement used for the perforations repair (MTA HP; calcium aluminate cement-CAC; and CAC + calcium carbonate nanoparticles-nano-CaCO3) and control group (no perforation). The groups were redistributed according to the fiberglass posts luting protocol (n = 8): total-etching (TE) (MTA HP/TE; CAC/TE; CAC + CaCO3/TE and control/TE) and self-etching (SE) (MTA HP/SE; CAC/SE; CAC + CaCO3/SE and control/SE). Roots were sectioned into 1.3mm-thick dentin slices obtaining samples that were submitted to the push-out test in Universal Testing Machine (Instron, Model 4444-0.5mm/min). The fractured samples were analyzed under stereomicroscope and Scanning Electron Microscope (SEM). CAC/TE and CAC/SE groups had significant difference between the cervical and middle thirds (p < 0.05). When the root thirds were not considered, CAC/SE had the lowest bond strength and differed statistically from CAC/TE and CAC + CaCO3/TE groups, which had the highest mean bond strength values (p < 0.05). The root perforations repair did not affect the bond strength of resin cement/customized fiberglass posts to bovine dentin. The increase in bond strength is luting protocol dependent.

Three-dimensional evaluation of mandibular canine impaction characteristics and their relationship with lower incisor root morphometry

To three-dimensionally evaluate the characteristics of mandibular canine impaction with the morphometry of the roots of the lower incisors. Cone-beam computed tomography (CBCT) scans of 35 individuals (18 males and 17 females) with a mean age of 14.37± 10.26 years were evaluated. Forty-three impacted mandibular canines (IMbC) were evaluated. Their location, sector and level of impaction were determined. Likewise, the distances of the canines to the occlusal plane, the angulations with respect to the midline and adjacent lateral incisors, the length of the impacted canines, and of the lower incisors were measured. Finally, the presence of incisor root resorption was determined. Chi-square and Kruskal Wallis tests were employed (P<0.05). The buccal position of the IMbCs was the most predominant (65.1%), and the location below the apical middle third of the lower incisor root was the most frequent (32.6%). No statistical significance was found between root resorption and location, level and impaction sector. Only mild root resorption and impaction sector 5 was significant (66.70%; P<0.001). The proximity of the follicle and crown of the IMbC did not affect the root structure of the lower incisors. 72.1% and 52.2% of mandibular canines did not present contact of the impacted canine or its follicle with the adjacent tooth respectively. Root lengths were similar in the different types of impactions (P>0.05). IMbCs are mostly positioned buccally and below the apical middle third of the root of the lower incisors. Likewise, the proximity of their follicles and crowns does not seem to affect the root structure of the lower incisors, producing minimal and infrequent root resorption. Key words:Mandibular canine impaction, incisor root morphometry, cone-beam CT.

Evaluation of Different Agitation Techniques on Smear Layer Formation and Dentine Erosions- An In Vitro Study.

This study was performed to assess smear layer formation and erosion after final irrigation protocols with metal and non-metal tips in the apical third of root canals. Forty mandibular premolars were instrumented with ProTaper Gold files up to F3 and embedded in a closed silicone flask system. The teeth were subsequently cleaved and 4 sequential indentations (1 to 4 mm from the apical foramen) were prepared on the buccal root canal walls to standardize sites for environmental scanning electron microscopy (ESEM) imaging. The samples were cleaned in an ultrasonic bath and observed under ESEM (controls), reassembled and divided into four groups (n=10 each) and subjected to different final irrigation protocols; XPF Group (XP-endo Finisher) and PUI Group (passive ultrasonic irrigation) with metal tips; EA Group (EndoActivator) and MDA Group (Manual dynamic agitation) with non-metal tips. The smear layer formation and dentine erosion were evaluated using ESEM. The data were analyzed with Kruskal-Wallis test with Bonferroni correction. In comparison to the control groups, XPF group had significantly increased smear layer formation at 1 and 2 mm (P<0.05). PUI group had significantly higher smear layer (P<0.05) formation at 3mm while EA and MDA groups did not present with significantly higher smear layer at all levels. Erosion was significantly higher (P<0.05) in MDA, XPF and PUI groups at all levels when compared to controls while EA group presented with significantly more erosion only at 2 and 3 mm. Final irrigation protocol using EA and MDA with non-metal tips did not result in significant smear layer formation. Dentine erosion was observed after all experimental irrigation protocols. (EEJ-2021-12-194).

Diabetes Mellitus Affects the Microhardness of Root Dentine: An in-vitro Study.

ObjectiveThis study was undertaken to compare microhardness and erosion susceptibility of root dentine in teeth extracted from diabetic and non-diabetic donors after the application of different root canal irrigants.MethodsForty-eight single-rooted premolars with single canals (24 each from diabetic and non-diabetic) were selected, and root canals were shaped by using rotary ProTaper files. Dentine slices of 4 mm were transversely sectioned from the middle root third. Specimens were assigned to four subgroups (n=6) and irrigated for 5 minutes: 1) 2.6% sodium hypochlorite (NaOCl); 2) 17% ethylenediaminetetraacetic acid (EDTA); 3) 2% chlorhexidine (CHX); and 4) normal saline. Surface microhardness was determined at 100- and 500-µm depths from the pulp–dentine interface. Scanning electron microscope (SEM) was used to determine the severity of dentine erosion. Data were analyzed by using two-way ANOVA, Post-hoc Tukey’s, and Chi-square tests (P<0.05).ResultsDiabetes as well as NaOCl and EDTA decreased surface microhardness of dentine significantly (P<0.05). Diabetes had little effect on the erosion susceptibility of dentine (P>0.05).ConclusionRoot canal irrigants can significantly lower the microhardness; specifically, in diabetic patients, and may be a factor affecting the longevity of root canal-treated teeth.

Intratubular penetration ability in the canal perimeter using HiFlow bioceramic sealer with warm obturation techniques and single cone.

BackgroundThe aim of this paper was to evaluate the intratubular penetration percentage in the perimeter of the canals of the calcium silicate-based sealer HiFlow, using three warm obturation techniques, continuous wave (CW) and vertical condensation (VC) with two different types of gutta-percha (conventional (NG) and bioceramic-coated (BG), GuttaCore (GC) and single cone (SC) with BG in different root thirds. Material and Methods180 human teeth with a single root were selected including incisors, canines and premolars were prepared and randomly divided into six groups (n=30). Teeth were filled using a bioceramic sealer TotalFill BC Sealer HiFlow (HiFlow) and two different types of gutta-percha, with CW, VC and GC techniques, the teeth in the control group were filled with SC technique and BG gutta-percha. The teeth were sectioned and evaluated as one-third portions in each case under a confocal laser microscope. The penetration ability in the canal’s perimeter was carried out with the Autocad® programme. Data was analyzed using Levene’s test (p<0,05), ANOVA test (p<0,05), Welch’s comparison test (p<0,05), Games-Howell multiple comparison test (p<0,05), Bonferroni test (p<0,05). ResultsThe percentages relative to penetration was higher in the warm obturation techniques than the SC in all thirds evaluated. Games-Howell test (p<0,05) showed up significant differences in multiple comparisons. There was greater penetration in the perimeter of the canals in the coronal third than in the apical third in all of the techniques. ConclusionsThe warm obturation techniques (CW, VC and GC) generated a greater intratubular penetration percentage in the canal perimeter of the sealer than the single cone in all thirds. Key words:HiFlow, calcium silicate-based sealer, confocal laser microscope, dentinal tubules.

Multiparameter image analysis to evaluate dentinal tubules patency after using different irrigation protocols

Background: Scoring systems have been used to evaluate dentinal tubule patency in several papers; however, these conventional systems are time-consuming and rely primarily on evaluator estimation with a wide range of subjective variations. Objectives: A multiparameter, simple, and objective method is introduced to evaluate the ability of different irrigation protocols for smear layer removal and dentinal tubule patency enhancement. To show the applicability of this method, the effect of different irrigation regimens was evaluated. Methods: Ninety extracted single-rooted teeth were decapitated and shaped with ProTaper to size F4. According to the final irrigation protocol, specimens were divided into three groups: Group 1 (final irrigation of SmearOFF), Group 2 (17% EDTA), and Group 3 (negative control). Groups 1 and 2 were subdivided into two subgroups: Subgroup (A) was activated by an ultrasonic file, whereas samples in Subgroup (B) did not receive any activation. Samples were examined by scanning electron microscopy. Images were analyzed using ImageJ software, and the multiparameter image analysis method (relative total surface area, average size, and the number of opened dentinal tubules) was applied. One-way analysis of variance (ANOVA), followed by Tukey’s post hoc test, was applied to reveal any significant differences (P < 0.05) among groups, activation techniques, and root thirds. Results: Passive ultrasonic activation led to a significant increase in the patency of dentinal tubules especially at the apical third, which was measured and shown by the triple parameter method. Conclusion: Digital image analysis shows potential and advantages for the objective evaluation of dentinal tubules and should replace the traditional subjective scoring system method.

Effect of RaCe, ProTaper, and V-Taper rotary systems on dentinal crack formation during endodontic treatment: An in vitro study.

Background. Prevention of dentinal crack formation is of utmost importance in endodontic treatment. This study aimed to evaluate the effect of RaCe, ProTaper, and V-Taper rotary systems on dentinal crack formation in three root regions during endodontic treatment. Methods. Seventy human mandibular first molars were selected randomly, and their distal roots were used. Ten samples were assigned to the control group, and sixty samples were assigned to three groups (n=20). Each group was prepared with RaCe, ProTaper, or V-Taper rotary files according to the manufacturers’ instructions. A stereomicroscope was used to view cracks at ×40 magnification. Friedman’s, chi-squared, and Kruskal-Wallis tests were used for statistical analysis of data (P < 0.05). Results. A comparison of the three rotary systems did not reveal any significant differences in the number of cracks between the three root thirds evaluated (P > 0.05). A comparison of the number of cracks in the coronal, middle, and apical thirds in each rotary system showed that the number of cracks in the middle third was fewer than that in the two other thirds only in the V-Taper group (P < 0.05), with no significant differences in the ProTaper and RaCe groups between the different root regions (P > 0.05). Conclusion. The application of RaCe, ProTaper, and V-Taper rotary files resulted in a similar rate of crack formation in endodontic treatment. V-Taper files created the minimum number of cracks in the middle third.

Comparison of the efficacy of three different supplementary cleaning protocols in root-filled teeth with a bioceramic sealer after retreatment-a micro-computed tomographic study.

The present study evaluated the efficacy of three different supplementary cleaning protocols on the removal of bioceramic-based root canal filling materials from oval-shaped canals. A total of 36 human mandibular premolars were instrumented and obturated with gutta-percha and iRoot SP using the single-cone technique. Retreatment was performed with ProTaper Universal retreatment files. The samples were randomly divided into the following supplementary cleaning protocols: conventional syringe irrigation (CSI), passive ultrasonic irrigation (PUI), and XP-endo Finisher R (XPR). The samples underwent micro-CT scanning to quantify the amount of residual filling materials after retreatment and after performing the cleaning protocols. The volume of filling material removal was analyzed by one-way analysis of variance and post hoc Bonferroni and Games-Howell tests (P < 0.05). There were significant differences in the amount of root canal filling material removal in every comparison group (P < 0.05). The XPR removed significantly more residual filling materials (P < 0.01) followed by PUI and CSI (P < 0.05). Similar efficacy was found in the total root canal and all root thirds. The additional use of XP-endo Finisher R and passive ultrasonic irrigation effectively removed the bioceramic-obturated root filling materials from the oval-shaped canals. However, none of the techniques completely removed the filling materials. The XP-endo Finisher R and passive ultrasonic irrigation exhibited greater efficacy compared with syringe irrigation in the reduction of residual filling materials after retreatment in root-filled teeth with a bioceramic sealer.

Transmission of 940 nm diode laser to the radicular area during its application as root canal disinfectant.

To measure the transmitted laser power in the coronal, middle and apical root thirds during vertical and horizontal irradiation of laser. 14 mm length whole roots and longitudinal root sections were irradiated using a 940 nm diode laser with 0.5 W in continuous mode for 5 s. A power detector was placed in front of the root apex for the vertical transmitted power measurement and placed laterally to root surface for the horizontal transmission experiment. The transmitted power from the root apex vertically was 53% of the irradiated power, while for the horizontal transmission experiment for the coronal, middle and apical root thirds were 25.6%, 40.4% and 41.3%, respectively. Irradiation of root canals with 940 nm laser power can be transmitted during vertical irradiation in more than 50% of the samples, whereas less transmission happens with horizontal irradiation at apical and middle root third than coronal.

Impact of several NiTi-thermally treated instrumentation systems on biomechanical preparation of curved root canals in extracted mandibular molars.

To evaluate the shaping ability of several heat-treated nickel-titanium systems used to prepare root canals with moderate and severe curvature, in extracted mandibular molars, by micro-computed tomography, considering their variation in kinematics and design. Curved-mesial roots of mandibular molars were randomly selected and assigned into 4 balanced experimental groups (n=10), established by determining homogeneous 3D parameters of volume and surface area: R-Motion (RM) size 30, 0.04 taper (RM; FKG Dentaire), Reciproc Blue (RCB) size 25, 0.08 taper (RCB; VDW GmbH), HyFlex CM (HFX) size 30, 0.04 taper (HFX; Coltène Whaledent) and XP-endo Shaper size (XPS) 30, 0.01 taper (XPS; FKG Dentaire). The volume of irrigation was established at 10ml of 2.5% NaOCl. Throughout the entire root canal preparation procedures, the samples were fixed in a vice submerged in a container with water monitored at 37°C. Dimensional cross-sectional measures of area, perimeter, roundness, major/minor diameters and 3-dimensional (volume, surface area, structure model index - SMI) parameters as well as the smallest dentine thickness along the cervical and middle root thirds were evaluated by micro-CT. Data were analysed using analysis of variance and post hoc Tukey tests (α=5%). Reciproc Blue and XPS had significantly greater mean increases in cross-sectional area measurements, only in the middle third, when compared with RM and HFX (p<.05). RM, RCB and XPS had a similar increase in measurements of length and width of perimeter (p>.05), and HFX had significantly lower mean increases in perimeter values only when compared with XPS (p<.05). RCB and XPS had significantly greater mean increases in volume when compared with RM and HFX (p<.05). RM had a significantly lower difference in SMI after preparation, compared with RCB, HFX and XPS (p<.05). The smallest dentine thickness was observed after the use of RCB (p<.05), in the danger and safety zones. XP-endo Shaper and RM had a shaping ability similar to that of instruments with larger tapers, achieved with less dentine removal in danger and safe zones in curved-mesial canals of extracted molar teeth treated on a laboratory benchtop.

Internal morphology of 101 mandibular canines of a Swiss-German population by means of micro-CT: An ex vivo study

The aim of this study was to investigate the root canal system morphology by means of a root canal configuration (RCC) classification described with a four-digit system, the physiological foramen geometry and accessory canal frequency and morphology, of 101 mandibular canines (MaCa) of a Swiss-German population by means of micro-computed tomography. Micro-CT examination of the MaCa was performed and the obtained images analyzed with a 3D imaging software. In single-rooted MaCas, the most frequently observed RCCs were 1-1-1/1 (74.5%) and 1-1-1/2 (14.3%). Seven other RCCs were less frequently observed with a frequency from 4.1 to 1.0%. One physiological foramen was observed in 80.6% of the MaCas, two in 16.3%, three in 1.0% and four in 2.0%. Accessory and connecting canals were apparent only in the middle and apical root thirds. Two-rooted MaCas occurred less frequently (n = 3). When one physiological foramen was present, the mean size of the narrow and wide diameters were 0.28 mm (± 0.07) and 0.40 mm (± 0.11), while the distance between physiological and anatomical foramen was 0.45 mm (± 0.17). MaCas are predominantly single-rooted teeth with a 1-1-1/1 or 1-1-1/2 RCC. Most MaCas had one physiological foramen with an oval shape.

Impact of Endodontic Kinematics on Stress Distribution During Root Canal Treatment: Analysis of Photoelastic Stress

IntroductionStructural defects created by endodontic treatment are the most common cause of major dental failures. This study analyzed levels of stress produced by endodontic instruments during the root canal treatment by photoelastic analysis of stress. MethodsTwenty-four human premolars were randomly divided into 4 groups (n = 6) according to instrumentation protocol: ProTaper Next (GPT), One Shape (GOS), Wave One Gold (GWO), and TF Adaptive (GTF). The evaluation of the photoelastic model was performed at 4 dental zones: dental-crown region, cervical third of root, middle third of root, and apical third of root. Silicone molds were prepared (2 × 15 mm), and pinjets were used inside the root canals to fixate teeth. Photoelastic resin (2:1 ratio) was poured into the silicone molds to form photoelastic models. A transmission polariscope was used to analyze the positions of interest and recorded with a digital camera. Tardy’s method was used to quantify the fringe order (n) and calculate the maximum stress value (τ) at each selected point. Data were analyzed with two-way analysis of variance, Tukey test (P < .05), fringe descriptive analysis. ResultsAll groups showed a significant increase in the level of stress created during biomechanical preparation of the root canals. In the quantitative analysis, there was no statistically significant difference among the groups (P > .05). In the qualitative analysis, GPT and GTF instruments achieved greater levels of stresses compared with GWO and GOS instruments. At the beginning of instrumentation, stresses were concentrated at the coronary level and the end of instrumentation at the middle and apical root level. ConclusionsAll endodontic systems resulted in accumulation of stress along the dental structure. Stress was found in different concentrations along the tooth and at different levels.

Better Glass-fiber Post Preservation in Teeth with Ferrule When Subjected to Chewing.

To evaluate the influence of ferrule effect and mechanical fatigue aging on glass-fiber post push-out bond strength (PBS) to root-canal dentin at different root thirds of premolars. Thirty-two sound maxillary premolar teeth were collected, and randomly assigned to two experimental groups (n=16): 'Remaining Dentin Ferrule' (RDF) = coronal crown cut 2.0 mm above the cementoenamel junction (CEJ); 'Without Dentin Ferrule' (WDF) = coronal crown cut at the cemento-enamel junction. Teeth were endodontically treated, post spaces were prepared up to 10.0-mm depth from CEJ, and glass-fiber posts were cemented using a dual-cure self-adhesive composite cement. Standardized cores were built using a light-cure composite, upon which tooth cores were prepared using a 1.5-mm taper ogival-end diamond bur. Crowns were handmade using self-cure acrylic resin and cemented using the aforementioned composite cement. Half of the specimens were subjected to 1,200,000 cycles of mechanical fatigue in a chewing simulator (F = 'Fatigue'), while the other half were stored in distilled water at 37°C for 1 week (C = 'Control'). All specimens were horizontally sectioned into 1.0-mm thick slices prior to PBS test; the failure modes were assessed using stereomicroscopy and scanning electron microscopy (SEM). Data were analyzed for each root third using two-way analysis of variance (ANOVA) followed by Tukey HSD post-hoc test; frequency distribution was compared by Chi-square test (α=0.05) and post-hoc comparisons with Bonferroni. The mean PBS in MPa (SD) were = RDF_F = 10.4 (2.9); WDF_F = 6.9 (1.7); RDF_C = 14.5 (2.7); WDF_C = 14.2 (2.9). Similar PBS were found for the root thirds. For all root thirds, significant differences were found for both the factors Dentin Ferrule and Fatigue, and their interaction (p<0.05). The lowest PBS was found for specimens without dentin ferrule subjected to chewing fatigue (p<0.001). Most failures occurred at the composite cement/dentin interface, followed by mixed and composite cement/glass-fiber post interfacial failures. There was a significant increase in mixed failures for the WDF_F group (p<0.001). Absence of 2.0-mm remaining dentin ferrule in premolars resulted in a higher decrease of the glass-fiber posts' PBS to dentin after mechanical fatigue, irrespective of root third.