Immediate and Delayed Bond Strength of a Multimode Adhesive to Deep Coronal Dentin Following Different Root Canal Irrigation Regimens.

PURPOSE: To investigate the effects of root canal irrigants, dentin surface treatment, and timing of the restoration on the microtensile bond strength (µTBS) of a universal adhesive to deep coronal dentin. MATERIALS AND METHODS: Ninety (90) intact molars were grouped according to the irrigation protocol: group 0 (saline, control group); group 1: 5.25% sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA) followed by 5.25% NaOCl; group 2: 18% etidronic acid (HEDP) + 5.25% NaOCl in a single mixture. Groups 1 and 2 were divided into 2 subgroups (n = = 10) according to the time of restoration: immediate (subgroup A) and after 7 days (subgroup B). Four other groups (n = 10) were created according to the dentin surface pretreatment and received an immediate restoration: group 3: 5.25% NaOCl - 17% EDTA and AH Plus Cleaner; group 4: 5.25% NaOCl - 17% EDTA and 100% ethanol; group 5: 5.25% NaOCl + 18% HEDP and AH Plus Cleaner; group 6: 5.25% NaOCl + 18% HEDP and 100% ethanol. µTBS testing was carried out for each subgroup and interfaces were analyzed through SEM. The µTBS was analyzed with Welch statistics and the post-hoc Games-Howell test for multiple comparisons (p < 0.05). RESULTS: Statistically significant differences were observed between test groups and control groups (p < 0.001), except for group 3 (p = 0.349). No significant differences were recorded between groups 1A (27.5 ± 8.7 MPa), 2A (32.6 ± 14.5 MPa) and 3 (27.3 ± 14.3 MPa). Group 6 (48.6 ± 11.6 MPa) exhibited the highest µTBS among all tested groups. For groups 1 and 2, significantly higher values were recorded for subgroups 1B (39.3 ± 7.6 MPa) and 2B (43.8 ± 8.3 MPa) compared to subgroups 1A (27.5 ± 8.7 MPa) and 2A (32.6 ± 14.5 MPa). CONCLUSION: When using NaOCl as root canal irrigant, it is advisable to delay the placement of a post-endodontic-treatment restoration.

Influence of remaining tooth substance and post-endodontic restoration on fracture strength of endodontically treated maxillary incisors.

The aim is to evaluate the influence of remaining tooth substance and post-endodontic restoration on fracture strength of endodontically treated maxillary incisors. 150 maxillary central incisors were divided into three groups, Group 0, intact teeth; Group 1, removal of distal wall; Group 2, removal of mesial and distal walls, and further into two subgroups A0,A1,A2 and B0,B1,B2 according to post-endodontic restoration (post/no-post), then loaded to fracture. Interactions among variables and intergroup significance were tested with two-way ANOVA and Kruskal Wallis's tests (p≤0.05). Tukey's test was applied for multiple comparisons. Statistically significant differences were found between groups B1-A1, and B2-A2, but they were not found between B0-A0. Intragroup analysis showed statistically significant differences in both groups post/no-post with decreasing dental substance. Fiber post placement causes an increase in fracture strength and a reduction of irreparable fractures in endodontically treated maxillary central incisors that lost at least one wall.

Influence of single post, oval, and multi-post restorative techniques and amount of residual tooth substance on fracture strength of endodontically treated maxillary premolars.

PURPOSE: The aim of this study was to compare the influence of the number of coronal walls and post-endodontic restorations on the mechanical strength of 165 recently extracted endodontically treated maxillary premolars. METHODS: The teeth were divided into 3 control (no post) and 3 test groups according to the number of residual walls. Each test group was divided into subgroups according to the type of post-endodontic restoration (single, oval, and multi-post techniques). Samples were prepared conforming to the assigned subgroup. A universal loading machine applied a load parallel to the longitudinal axis of the teeth, thus simulating physiological occlusion. ANOVA and the Kruskal Wallis test were used for comparisons (P ≤ 0.05), and Tukey's test for multiple comparisons. RESULTS: For intact teeth, significant differences were found among all 3 subgroups, with single post showing the highest values. For 3 residual walls, oval post resulted in significantly lower values than single and multi-post systems. For 2 residual walls, the multi-post technique showed almost twice the resistance of oval post restorations. CONCLUSION: In oval canals the use of a single or multi-post technique increased post-and-core resistance even in intact teeth, whereas oval fiber posts showed no improvements. Multi-post design improved fracture resistance mostly in maxillary premolars lacking both marginal ridges.

A new framework to identify dental emergencies in the COVID-19 era.

In order to reduce the spread of COVID-19 (Coronavirus Disease 2019), it is crucial to take extraordinary prevention and safety measures in dental offices, and to defer all elective and non-urgent procedures. Dental emergencies are defined through oral symptoms but, the systemic and psychological conditions of each patient should be considered. The present short communication proposes a multilevel evaluation (oral, systemic and psychological) and risk assessment score for the management of dental emergencies following the SARS-CoV-2 (severe acute respiratory syndrome coronavirus-2) outbreak. A comprehensive categorization and score scale assessment for dental emergencies allows a better identification of patient's treatment needs and avoids unnecessary contact between dental health care providers and patients during the SARS-CoV-2 pandemic.

Push-out Bond Strength of Fiber Posts Cemented Using New Universal Adhesives on Etched and Nonetched Intraradicular Dentin.

AIM: The aim of this study was to assess if the curing mode and the etching mode could affect the push-out bond strength of different post cementation systems using two universal adhesives. MATERIALS AND METHODS: A total of 100 single-rooted teeth were divided into Prime & Bond Elect (PBE), Prime & Bond Active (PBA), and Prime & Bond XP (PBXP) as a control. The PBE, PBA, and PBXP were used in the self-etch (SE) and etch and rinse (E&R) mode. Post cementation was performed using Core X flow used in dark-cure and in light-cure. Data were analyzed using the one-way ANOVA test and post hoc Bonferroni and Dunnet tests. The Student's t test was performed to find significance between two independent groups. RESULTS: Bond strength was significantly influenced by the adhesive strategies. The PBE and PBA obtained higher values when used in the SE mode (p < 0.001). Light-cured groups obtained significantly higher values (p < 0.001) compared to dark-cured groups. The post space region also had a significant effect on the bond strength; the apical third recorded lower values in all groups (p < 0.001). CONCLUSION: The PBA and PBE universal adhesives obtained higher PBS values when used in the SE mode and followed by the light-curing of resin cement. CLINICAL SIGNIFICANCE: Universal adhesives represent a good alternative to the conventional total-etch adhesive system for fiber post cementation. Since they perform better in SE, they would be recommendable in clinical practice, as they can be used with a simplified technique.

Different Post Placement Strategies for the Restoration of Endodontically Treated Maxillary Premolars with Two Roots: Single Post vs Double Post.

AIM AND OBJECTIVE: The present study compared the fracture strength and failure pattern of endodontically treated, bi-rooted, maxillary premolars with different number of coronal walls and postendodontic restoration (one vs double post). MATERIALS AND METHODS: 105 premolars were divided into 3 groups according to the number of residual walls: control group (intact teeth; n = 15), group 1 (3 residual walls; n = 45), group 2 (2 residual walls; n = 45). Each test group was then divided into 3 subgroups (n = 15 each) according to postendodontic restoration: no post (A), 1 post (B) or 2 posts (C). A load was applied parallel to the longitudinal axis of the teeth, thus simulating physiological occlusion. ANOVA and Tukey's tests were used to detect fracture strength differences among groups, while Chi-square test was used to check differences in fracture pattern. RESULTS: No significant differences were observed between control group (intact teeth) and groups A1 (p = 0.999), B1 (p = 0.997) and C1 (p = 1.000); statistically significant differences were detected between control group and groups A2 (p < 0.001), B2 (p < 0.001) and C2 (p < 0.05). Different post placement techniques were non-significantly associated with fracture pattern in both groups 1 (p = 0.666) and 2 (p = 0.143) while, irrespective of the number of posts, the presence of the post was significantly associated with the fracture pattern in teeth with two residual walls. The double-post technique did not further improve the fracture resistance of hardly damaged endodontically treated maxillary bi-rooted premolars compared to single-post technique. Therefore, the insertion of a single post in the palatal canal could be a safer and more conservative choice. CLINICAL SIGNIFICANCE: The double-post technique did not further improve the fracture resistance of severely structurally compromised endodontically treated maxillary premolars with two roots compared to the single-post technique. Therefore, the safer and less invasive treatment is the placement of a single post in the palatal canal.

Shaping effectiveness and surface topography of reciprocating files after multiple simulated uses.

This in vitro study assessed morphological changes and efficiency of reciprocating files after multiple uses. Sixty standardized Endo Training Blocks and 10 ReciprocR25 files were selected (six blocks for each file). Each file was its own control (before use vs. after each instrumentation). The instruments were used according to the manufacturer's instructions, and scanning electron microscopy was used to observe fatigue cracks, metal strips/metal flash, pitting, fretting, debris, disruption of the cutting edge, and plastic deformations after each instrumentation. The presence of seven wear variables was scored semiquantitatively by viewing micrographs collected before and after use. The prepared areas in resin blocks were calculated and compared by using AutoCAD software. The control group had significantly lower values for all wear variables except fretting and plastic deformation. The presence of fatigue cracks and metal strips/metal flash significantly differed between unused instruments and instruments used four or five times, in all observed sections. The area of instrumented Endo Training Blocks significantly differed in relation to the number of instrument uses. The Reciproc files wore progressively, and repeated use affected their shaping efficiency in simulated canals.

Influence of Access Cavity Preparation and Remaining Tooth Substance on Fracture Strength of Endodontically Treated Teeth.

INTRODUCTION: The purpose of this study was to assess the impact of access cavity preparation and the remaining tooth substance on the fracture strength of endodontically treated teeth. METHODS: One hundred sound mandibular first and second molar teeth were selected and divided into 1 control and 9 test groups (n = 10/group) as follows: control group, intact teeth; group 1, teeth prepared with traditional endodontic access cavity (TEC); group 2, teeth prepared with conservative endodontic access cavity (CEC); group 3, teeth prepared with truss endodontic access cavity (TREC); group 4, TEC + 3 residual walls; group 5, CEC + 3 residual walls; group 6, TREC + 3 residual walls; group 7, TEC + 2 residual walls; group 8, CEC + 2 residual walls; and group 9, TREC + 2 residual walls. After access cavity preparation, all test teeth were endodontically treated and restored. The specimens were then loaded to fracture in a universal loading machine (Triaxial Tester T400 Digital; Controls srl, Cernusco, Italy), and fracture values were recorded in newtons. The data were analyzed with 2-way analysis of variance and Tukey post hoc analysis for multiple comparisons (P < .05). RESULTS: Intact teeth were more resistant to fracture than the teeth in all the test groups. No statistically significant differences were found between the 3 tested access cavities (P > .05). Significant differences were observed between the different number of residual walls (P < .05). CONCLUSIONS: TRECs do not increase the fracture strength of endodontically treated teeth in comparison with CECs and TECs. Moreover, the loss of mesial and distal ridges reduced the fracture strength of teeth significantly.