The Effect of Bevel on Fracture Resistance of GIC Restorations in Primary Molars: In Vitro Study Rôle du Biseau dans la Résistance à la Fracture des Restaurations aux Ciments Verres-Ionomères des Molaires Temporaires : Étude In Vitro

Background: Glass ionomer cements (GICs) are commonly used for restorations in primary molars due to their adhesive, hydrophilic, and bioactive properties. However, their low mechanical resistance may limit their use in proximal cavities. Recent advancements in GICs, such as the high viscosity GIC EQUIA Forte®, have improved their mechanical properties. The effect of a Cavo superficial bevel on the mechanical strength of GIC restorations has been previously studied. Objectives: To investigate the effect of a Cavo superficial bevel on fracture resistance and the type of fracture (adhesive, cohesive, or catastrophic) in EQUIA Forte® GIC restorations in primary molars. Methods: 56 standardized proximal cavities were created on 51 temporary molars. The cavities were randomly divided into two groups: group I without a Cavo superficial bevel (n=28) and group II with a 45° Cavo superficial bevel (n=28). The cavities were restored with EQUIA Forte®. The samples were subjected to thermocycling and artificial aging, then, an axial speed loading of 1 mm/min was applied until fracture. Fracture toughness was recorded, and the type of fracture was observed under an optical microscope. A Mann-Whitney U test was used to compare the average fracture resistance between the groups. All tests were two-tailed and the level of significance was set at 5%. Results: The average fracture resistance for group I was (237.57 ± 139.97 N) and for group II was (294.89 ± 171.07 N). There was no statistically significant difference in fracture resistance between the two groups (p\u3e0.05). Mixed fractures were observed in all samples, with adhesive fractures only present in group I and cohesive fractures only present in group II. Conclusion: The Cavo superficial bevel does not significantly affect the fracture resistance of GIC restorations in primary molars. However, the bevel design may prevent adhesive and catastrophic fractures. Contexte : Les ciments verres-Ionomères (CVI) sont couramment utilisés pour les restaurations des molaires temporaires grâce à leurs propriétés adhésives, hydrophiles et bioactives. Cependant, leur faible résistance mécanique limite leur utilisation dans les cavités proximales. Avec les récents progrès de cette classe de matériaux, un CVI à haute viscosité a été introduit : EQUIA Forte®, visant à améliorer leurs propriétés mécaniques. Le rôle du biseau cavo-superficiel sur la résistance mécanique des restaurations au CVI a déjà été étudié. Objectifs : Tester le rôle du biseau dans l’amélioration de la résistance à la fracture et d’étudier la nature du trait de fracture adhésif, cohésif, ou catastrophique des restaurations aux CVI EQUIA Forte® des molaires temporaires. Méthodes : 56 cavités proximales standardisées ont été réalisées sur 51 molaires temporaires. Ces cavités ont été divisées aléatoirement en deux groupes : groupe I sans biseau cavo-superficiel (n=28) et groupe II avec biseau cavo-superficiel de 45° (n=28). Les cavités ont été restaurées par EQUIA Forte®. Les échantillons ont été soumis à un thermocyclage et à un vieillissement artificiel, puis une vitesse axiale de chargement de 1 mm/min a été appliquée jusqu\u27à la fracture. La résistance à la fracture a été enregistrée et le type de fracture a été observé au microscope optique. Le test de Mann-Whitney U a été utilisé pour comparer la résistance moyenne à la fracture entre les groupes. Tous les tests étaient bilatéraux et le niveau de signification a été fixé à 5 %. Résultats : La résistance moyenne à la fracture pour le groupe I était de (237,57 ± 139,97 N) et pour le groupe II était de (294,89 ± 171,07 N). Il n\u27y avait pas de différence statistiquement significative en termes de résistance à la fracture entre les deux groupes (p \u3e 0,05). Cependant, des fractures mixtes ont été observées dans tous les échantillons, les fractures adhésives étant uniquement présentes dans le groupe I et les fractures cohésives présentes uniquement dans le groupe II. Conclusion : Le biseau cavo-superficiel n\u27influence pas de manière significative la résistance à la fracture des restaurations CVI des molaires temporaires. Cependant, il s’est avéré que la conception du biseau empêche les fractures adhésives et catastrophiques d’avoir lieu. Mots clés : Biseau, CVI, Classe II, Molaires Temporaires, Restauration, Type de fractur

Evaluation of Two Shaping Systems and Two Ultrasonic Irrigation Devices in Removing Root Canal Filling Material from Mesial Roots of Mandibular Molars: A Micro CT Study

We assessed the efficiency of two shaping file systems and two passive ultrasonic irrigation (PUI) devices for removing filling material during retreatment. The mesial canals from 44 extracted mandibular molars were prepared and obturated. The teeth were randomly divided into two groups, and then one group was retreated with Reciproc R25 (VDW, Munich, Germany) (n = 44) and the other group was retreated with 2Shape (TS, Micro Mega, Besançon, France) (n = 44). A micro-computed tomography (CT) scan was taken before and after the retreatment to assess the volume of the filling material remnants. The teeth were then randomly divided into four groups to test two different PUI devices: Irrisafe (Satelec Acteon Group, Merignac, France) and Endo Ultra (Vista Dental Products, Racine, WI, USA). The teeth in Group A were retreated with 2Shape to test the Endo Ultra (n = 22) device, the teeth in Group B were retreated with 2Shape in order to test the Irrisafe (n = 22) device, the teeth in Group C were retreated with Reciproc to test the Endo Ultra (n = 22) device, and Group D was retreated with Reciproc to test the Irrisafe (n = 22) device. A third micro-CT scan was taken after the retreatment to test the PUIs. The percentage of Gutta-Percha (GP) and sealer removed was 94.75% for TS2 (p < 0.001) and 89.3% for R25 (p < 0.001). The PUI significantly enhanced the removal of the filling material by 0.76% for Group A (p < 0.001), 1.47% for Group B (p < 0.001), 2.61% for Group C (p < 0.001), and by 1.66% for Group D (p < 0.001). 2Shape was more effective at removing the GP and sealer during retreatment (p = 0.018). The supplementary approach with PUI significantly improved filling material removal, with no statistical difference between the four groups (p = 0.106)

Effectiveness of the REvision System and Sonic Irrigation in the Removal of Root Canal Filling Material from Oval Canals: An In Vitro Study

This study aimed to evaluate the effectiveness of the Endostar REvision system (Poldent, Warsaw, Poland) in the removal of filling materials from oval root canals using sonic irrigation as an additional cleaning method. Thirty human-extracted mandibular premolars with oval canals were prepared using the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland) up to instrument F1 (20/.07), and then filled by the continuous wave vertical compaction technique using pulp canal sealer EWT (Sybron Dental Specialties, Orange, CA, USA). The teeth were randomly divided into two groups (n = 15) according to the instrumentation system and the additional cleaning method, as follows: REvision (30/.08, 25/.06) with EQ-S sonic activation (Meta Biomed, Chungcheongbuk-do, Korea), REvision (30/.08, 25/.06) without additional activation. All specimens were sectioned longitudinally at 3 and 7 mm from the apex, and analyzed using digital microscopy (KEYENCE, Osaka, Japan) to measure the total area of the residual obturation materials, followed by SEM analysis. The data on the percentage of remaining filling material were analyzed by Kruskal–Wallis one-way Analysis of Variance on ranks. None of the retreatment protocols completely removed the filling material from the root canals (p > 0.05); the retreatment technique using sonic activation showed statistically less residual filling materials than the retreatment technique using irrigants without activation at the coronal third (p 0.05). The REvision system showed promising results in the removal of filling materials from oval canal

The Influence of Brushing Motion on the Cutting Efficiency of Two Heat-Treated Endodontic Files: An In-Vitro Micro Computed Tomography Study

Background: To assess the cutting efficiency of two heat-treated endodontic files with a brushing motion in oval-shaped canals. Methods: A total of 10 intact lower molars with a single oval distal canal were selected and randomly divided into two groups according to the system used for shaping: 2Shape and Hyflex CM. The instrumentation was performed in two parts: a first shaping according to the manufacturer’s instructions and final shaping using 5 brushing motions on the distal, lingual, and buccal walls, avoiding the danger zones. Micro computed tomography (micro-CT) scans before and after the brushing motion were superimposed at all three levels: coronal, middle, and apical. Canal changes in buccolingual (ΔBL) and mesiodistal (ΔMD) dimensions were measured. Data were statistically analyzed by repeated-measures analyses of variance and the student t-test (p < 0.05). Results: For ΔMD, no significant difference emerged between the 2Shape and Hyflex CM in the apical and coronal thirds. However, the cutting efficiency was significantly greater with the 2Shape in the middle third (p < 0.05). Regarding ΔBL, no statistically significant difference was detected between 2Shape and Hyflex CM comparing the anatomical thirds, while 2Shape had a significant higher cutting efficiency considering the total BL diameter (p < 0.05). Conclusions: Under the limits of a vitro study, the shaping procedure with 2Shape and brushing motion was more efficient than the Hyflex CM in the midroot levels in terms of ΔMD, and in total canal space for ΔBL. Both files ensured an effective mechanical preparation

The Contribution of Various In Vitro Methodologies to Comprehending the Filling Ability of Root Canal Pastes in Primary Teeth

A void-free obturation during root canal treatment on primary teeth is currently very difficult to attain. In this study, the pulpectomy filling abilities of Bio-C Pulpecto (Angelus, Basil, Londrina, Paraná, Brazil) and of zinc oxide eugenol, or "ZOE" (DenPro, Prevest, New York, NY, USA), were compared using several in vitro techniques. Therefore, 30 primary anterior teeth were used in the present in vitro study. Analysis of variance (ANOVA), including a multiple comparison procedure (Holm-Sidak method, Dunn's Method, or Tukey test), was used. On micro-CT, Bio-C Pulpecto exhibited higher void percentages than did ZOE (10.3 ± 3.8%, and 3.5 ± 1.3%), respectively (p < 0.05). With digital microscopy, higher total void percentages were found in the BC (13.2 ± 26.7%) group compared to the ZOE (2.7 ± 2.8%) group (p < 0.05). With the CLSM, mean tubular penetration depths were higher for Bio-C Pulpecto than for ZOE in all canal thirds (p < 0.05). SEM images demonstrated no tags into dentinal tubules in either group throughout the three thirds. Moreover, higher statistically significant flowability was found for Bio-C (2.657 ± 0.06 mm) compared to ZOE (1.8 ± 0.13 mm) (p < 0.05). The findings of this study indicate that neither ZOE nor Bio-C Pulpecto appears to meet the criteria for an ideal root canal filling paste for primary teeth. This study laid the groundwork for future research by determining how micro-CT, digital microscopy, SEM, and CLSM contribute to our understanding of the filling process of primary teeth. More thorough research on the mechanism of root canal obturation on primary teeth is required to achieve a long-term successful root canal therapy in young children