Although benefiting from an unprecedented technological evolution, contemporary endodontics is still characterized by the recurrence of retreatments, due to the need to solve quite frequent incidents, accidents, or even failures of primary endodontic treatment. This survey aims to assess both the etiology and the prevention methods of one of the most troublesome endodontic iatrogenies: instrument separation during root canal shaping. The multifactorial nature of this occurrence entails identifying and taking into account all the causal and contributing factors. Their significant number and the possible involvement of any of them, starting with the complexity and variability of the root canals and ending with the technical specifications concerning the nickel-titanium rotary instrumentation system being used, highlight the necessity to develop valid guidelines to avert the occurring of such an upsetting situation.

This study aims to determine whether the design of resin posts reinforced with glass fiber (FRC) and Reporfost (Angelus, Londrina, PR, Brazil) significantly improves the fracture resistance of endodontically treated teeth restored through this method.A batch of 30 maxillary monoradicular teeth (15 central incisors, 15 canines) were treated endodontically by step-back technique (apical enlargement 40-K file) sealed with Sealapex (Kerr Corporation, Orange, US) and gutta-percha by lateral condensation, cold. They were divided into two equal groups, prepared for cementing the FRC posts. The Exacto posts (Angelus, Londrina, PR, Brazil) in group 1 and the Reforpost posts (Angelus; Londrina; PR, Brazil) were cemented with dual cure resin cement Breeze Self-Adhesive Resin Cement (Pentron Clinical, Orange, US). Fracture resistance testing was performed on the crown-apical axial direction, using the Hounsfield / Tinius Olsen H1-KS, PA, USA mechanical testing apparatus. The behavior of each tooth-post assembly was recorded as a graph. The statistical analysis was done using one way ANOVA (α=0.05). The differences between the Exacto post group and the Reforpost post group are not statistically significant (p = 0.466). The maximum force recorded was 970 N and the minimum 186N. The mean force at which the fracture occurred was approximately 500N for both groups. The strain test showed that modifying the Reforpost post design did not improve the fracture resistance parameters of the tooth-post assembly through increasing the surface friction or maintaining adhesion to the walls of the root dentin.

Canal filling must be well adapted to the walls of the root canal to prevent bacterial infiltration. Endodontic seals play an essential role in ensuring tightness, without which the canal filling would suffer infiltrations. This study aimed to evaluate the areas occupied by the two components of the canal filling, as well as the sealer/gutta-percha ratio in the root canals of the maxillary central incisors after their filling using the cold lateral condensation technique with gutta-percha. Thirty extracted upper central incisors were rotatably prepared with ProTaper Universal up to F3 and sealed using the cold lateral condensation technique with gutta-percha. After setting the sealer, the roots of the teeth were sectioned perpendicularly to 1 (L1), 3 (L3), 6 (L6), and 8 (L8) mm from the apex. The surface of the sections was analyzed with a Leica EZ4D stereomicroscope and photographed at two magnification orders: 10x and 25x. The areas corresponding to the gutta-percha, sealer, gaps, and root canal were expressed in pixels using the ImageJ software, version 1.50i. The difference in the representation of sealer areas, gutta-percha and voids was statistically significantly different for all four sections analyzed. The best adaptation of the canal obturation was observed in L1 and L3. The gutta-percha area was statistically significantly higher than that of the sealer for the L1, L3, and L6 levels, while the sealer/gutta-percha ratio recorded the lowest value at the L3 level (0, 30) and the highest at its L8 (0.70) level, without registering statistically significant differences regarding the area at the four analyzed levels. The voids were mostly absent or recorded a minimal percentage area (<1%). Cold lateral condensation of gutta-percha has led to a good adaptation of gutta-percha to the root canal wall, with a small amount of sealer, especially to the sections made at 3 mm from the apex. Given the limitations of this study, we noted that the voids were few – observed in the 6 and 8 mm sections – and were negligible in many cases.

(1) Background: What is the effect of 16% and 40% concentration bleaching agents on dental structures in healthy patients compared to predialysis patients? (2) Methods: Forty teeth were included in the study (20 from healthy patients and 20 from predialysis patients). Each group was randomly divided into another two subgroups (n-10), depending on the bleaching agent concentration (16% and 40% gels). Color parameters were registered before and after the whitening process using a spectrophotometer. To determine enamel ultramicroscopic modifications, SEM and AFM analysis were performed before and after bleaching. (3) Results: An increasing trend was identified in the average values of ∆E and ∆L within the groups of predialysis teeth between teeth whitened with 40% concentration gel and those whitened with 16% concentration gel, while for the enamel samples from healthy patients the trend was reversed. The average values for roughness in the case of the two bleaching agents in healthy and predialysis teeth presented statistically significant differences (p < 0.05). (4) Conclusions: The effects of bleaching agents are less significant on teeth from predialysis compared to healthy patients. A direct link exists in terms of the clinical effect between the concentration of the whitening gel and color modifications.

This study aims to analyze the performance of rotary root canal preparation, conducted by beginner operators (students). After acquiring the necessary skills involved in applying endodontic preparation techniques on extracted teeth, all students from a cohort learned to use ProTaper Universal files (Dentsply Maillefer). The preclinical training had several stages. Experience 1: instrumentation on extracted single-root teeth; Experience 2: instrumentation on EndoTraining blocks (Dentsply Maillefer); Experience 3: instrumentation on EndoTraining blocks (Dia Dent Group International); Experience 4: Instrumentation on extracted multiradicular teeth. Preparation was done according to the manufacturer’s instructions, the initial file is Sx, followed by S1, S2, F1, F2 and the last file is F3. A batch of 50 teeth (E1, E2, E3, E4) was randomly selected to evaluate the onset of the rotary preparation of young operators. Two independent evaluators analyzed the array radiologically by stereomicroscope evaluation (E1, E4) and photo-analysis of the resulting Endo Training blocks (E2, E3). The success rate was 80% for E1, 72% for E2, 64% for E3 and 76% for E4 (p<0.05). The following were considered a failure: ledge formation and apical transportation in 10.66%, over instrumentation in 6.66%, zipping in 3.33%, and instrument fracture in 4% of cases. Endodontic instrumentation techniques require training to acquire the necessary skills. Rotary root canal instrumentation techniques used almost exclusively in modern endodontics require adequate preclinical training.