Patient-related predictors of post-operative pain following root canal treatment: A structural model analysis.

AIM: The pathways to post-operative pain are complex and encompass factors that extend beyond the treatment protocol employed. This study aimed to identify patient-related predictors of post-operative pain following root canal treatment. METHODOLOGY: A total of 154 patients received a single-visit root canal treatment for asymptomatic necrotic mandibular molars. Before treatment, dental anxiety, dental fear and sense of coherence (SOC) were measured as predictors for each patient using validated questionnaires. Other measured predictors included gender, age, previous negative experiences at the dental offices and prior root canal treatment. Post-operative pain was assessed using the Numeric Rating Scale at multiple time-points over 30 days. Structural equation analysis was employed to evaluate the direct and indirect effects of patient-related predictors on a theoretical model of post-operative pain. The irrigant solution was also included in the model, as it was the only aspect that varied in the treatment protocol (sodium hypochlorite 2.5% and 8.25%). RESULTS: Dental anxiety (coefficient 0.028; p < .01), dental fear (coefficient 0.007; p = .02) and irrigant solution (coefficient 0.004; p = .03) exerted a direct effect on post-operative pain. SOC exerted an indirect effect on post-operative (coefficient 0.006; p = .01) through dental anxiety and dental fear. Moreover, previous negative experiences (coefficient 0.048; p = .04) exerted an indirect effect on post-operative pain through dental anxiety. CONCLUSIONS: Dental anxiety, dental fear, previous negative experiences and SOC are patient-related predictors of post-operative pain following root canal treatment. These factors should be taken into consideration in clinical practice, as patients with these characteristics may be at an increased risk of experiencing post-operative pain.

Ultrasonic activation of adhesive systems increases bond strength and intratubular penetration of resin cement in root dentin subjected to radiation therapy.

OBJECTIVE: This study aimed to evaluate the effect of ultrasonic activation of etch-and-rinse and self-etch adhesive systems on the bond strength of resin cement to irradiated root dentin. MATERIALS AND METHODS: Eighty human maxillary anterior teeth were distributed into 8 groups (n = 10), according to the type of adhesive system used (etch-and-rinse and self-etch), the ultrasonic activation of the adhesive systems, and the dentin condition (irradiated or non-irradiated - 70 Gy). Endodontic treatment was performed followed by fiberglass post-space preparation. After fiberglass posts' luting, the roots were transversely sectioned on dentin discs and submitted to the push-out bond strength test (0.5 mm/min). The fractured specimens were analyzed under a stereomicroscope and Scanning Electron Microscope (SEM) for failure mode classification. One of the dentin discs was analyzed under SEM to evaluate the characteristics of the adhesive interface. RESULTS: Irradiated specimens had lower bond strength than non-irradiated specimens (P < 0.0001). Ultrasonic activation of both adhesive systems increased the bond strength of the resin cement to irradiated dentin (P < 0.0001). Radiotherapy significantly affected the failure mode in the middle (P = 0.024) and apical thirds (P = 0.032) (adhesive failure). CONCLUSION: Non-irradiated specimens had a more homogeneous adhesive interface. When ultrasonically activated, both adhesive systems showed a greater number of resinous tags, regardless of the dentin condition. CLINICAL RELEVANCE: Ultrasonic activation of adhesive systems is a feasible strategy to enhance fiberglass posts retention in oncological patients.

Assessment of multispecies biofilm growth on root canal dentin under different radiation therapy regimens.

OBJECTIVES: To assess the growth of a multispecies biofilm on root canal dentin under different radiotherapy regimens. MATERIALS AND METHODS: Sixty-three human root dentin cylinders were distributed into six groups. In three groups, no biofilm was formed (n = 3): NoRT) non-irradiated dentin; RT55) 55 Gy; and RT70) 70 Gy. In the other three groups (n = 18), a 21-day multispecies biofilm (Enterococcus faecalis, Streptococcus mutans, and Candida albicans) was formed in the canal: NoRT + Bio) non-irradiated + biofilm; RT55 + Bio) 55 Gy + biofilm; and RT70 + Bio) 70 Gy + biofilm. The biofilm was quantified (CFUs/mL). Biofilm microstructure was assessed under SEM. Microbial penetration into dentinal tubules was assessed under CLSM. For the biofilm biomass and dentin microhardness pre- and after biofilm growth assessments, 45 bovine dentin specimens were distributed into three groups (n = 15): NoRT) non-irradiated + biofilm; RT55 + Bio) 55 Gy + biofilm; and RT70 + Bio) 70 Gy + biofilm. RESULTS: Irradiated specimens (70 Gy) had higher quantity of microorganisms than non-irradiated (p = .010). There was gradual increase in biofilm biomass from non-irradiated to 55 Gy and 70 Gy (p < .001). Irradiated specimens had greater reduction in microhardness after biofilm growth. Irradiated dentin led to the growth of a more complex and irregular biofilm. There was microbial penetration into the dentinal tubules, regardless of the radiation regimen. CONCLUSION: Radiotherapy increased the number of microorganisms and biofilm biomass and reduced dentin microhardness. Microbial penetration into dentinal tubules was noticeable. CLINICAL RELEVANCE: Cumulative and potentially irreversible side effects of radiotherapy affect biofilm growth on root dentin. These changes could compromise the success of endodontic treatment in oncological patients undergoing head and neck radiotherapy.

Evaluation of changes in root canal length and accuracy of the electronic apex locator during different stages of endodontic treatment and retreatment.

This study evaluated changes in the root canal length (RCL) and the accuracy of the electronic apex locator (EAL) during the different stages of endodontic treatment and retreatment. Fifty-six mesial root canals of mandibular molars were selected. The actual root canal length (AL) of the canals was obtained by inserting a size 15 hand file up to the apical foramen, under magnification. The electronic lengths were obtained at the "APEX" mark of Root ZX II, using an alginate model. Both measurements were performed at three different stages of the initial root canal treatment-unflared, flared, and concluded-and at two stages of retreatment, after achieving patency and repreparation. Data were statistically analyzed and the significance level established was 5%. All stages produced a significant reduction in the AL (p < 0.05). The greatest variation was observed between the unflared-flared stages (0.2 mm) and between concluded-patency stages (0.09 mm), with no difference between them (p > 0.05). The accuracy of Root ZX II was negatively affected after achieving patency, presenting statistically significant difference compared to the other stages (p < 0.05). A significant reduction in the RCL was observed along the different stages of endodontic treatment and retreatment. The EAL was accurate to measure the root canals in most stages, except after achieving patency for endodontic retreatment. Determining and monitoring the RCL is an essential step towards a favorable prognosis, since it reduced along the different stages evaluated. Root ZX II was not accurate for endodontic retreatment.

Effectiveness of different supplementary protocols for remaining filling material removal in endodontic reintervention: an integrative review.

The aim of this study was to perform an integrative review to identify the most effective supplementary protocols used after filling material (FM) removal and root canal reinstrumentation, during endodontic reintervention. The literature search was performed on the electronic databases PubMed and Latin American and Caribbean Health Sciences Literature (LILACS), using a combination of specific scientific descriptors. Selection criteria accepted articles published in English, Spanish and Portuguese languages, up to August 2021, involving in vitro and ex vivo studies. After applying the eligibility criteria, 46 articles were included for qualitative analysis. The tool for qualitative analysis of quasi-experimental studies of the Joanna Briggs Institute was used to determine the risk of bias of the included articles. The selected articles provided important data regarding the following supplementary protocols: sonic and ultrasonic activation of the irrigating solution; the use of ultrasonic inserts, XP-endo system instruments, and photon-induced photoacoustic streaming for mechanical debridement; and new devices as GentleWave system, and the self-adjusting file. Overall, all supplementary protocols demonstrated efficacy in removing the remaining FM. The implementation of various supplementary protocols can effectively remove the remaining FM from the root canal walls, although complete removal is not always achieved. However, it was not possible to determine the most effective protocol. Conversely, their association can enhance remaining FM removal. Remaining FM attached to root canal walls hinders proper chemical-mechanical preparation during endodontic reintervention. Supplementary protocols optimize the remaining FM removal, enhancing cleaning and disinfection of root canal.

Do the apical limit and diameter of the instrumentation influence the extrusion of sodium hypochlorite solution? A micro-CT study.

This study evaluated the influence of the apical limit and the diameter of the instrumentation on the extrusion of the irrigating solution. Sixty human lower premolars were distributed into 5 groups according to the apical limit and diameter of the root canal instrumentation (n = 12): (G-140) R40 instrument 1 mm above the tooth length (TL) (Control); (G-150) R50 instrument 1 mm above the TL; (GF25) R25 instrument at the TL; (GF40) R40 instrument at the root canal length and (GF50) R50 instrument at the TL. A space of 33.5 ± 1 mm3 was created for storage of the extruded solution. Omnipaque contrast was added to the NaOCl solution in a 1:2 ratio, totaling 15 mL of solution to allow its visualization when extruded in microcomputed tomography. Final irrigation was performed with a syringe and needle and activated with a passive ultrasonic irrigation (PUI). Three activation cycles were performed. Data were tabulated and statistically analyzed (one-way ANOVA) with a significance level set at 5%. It was observed irrigating solution extrusion after final irrigation in all groups. However, there were no statistically significant differences among experimental groups, regardless of the diameter or apical limit of root canal instrumentation (p > 0.05). The different apical limits and diameters of root canal instrumentation did not influence the volume of extruded irrigating solution using passive ultrasonic irrigation.

Ultrasonic activation of the endodontic sealer enhances its intratubular penetration and bond strength to irradiated root dentin.

To evaluate the effect of ultrasonic activation of the endodontic sealer on its intratubular penetration and bond strength to irradiated root dentin. Forty human teeth were distributed into 4 groups (n = 10), according to the radiation therapy (RT) exposure-70 Gy-and ultrasonic activation (UA) of the endodontic sealer: RT/UA-irradiated teeth and sealer UA; RT/no-UA-irradiated teeth and no sealer UA; no-RT/UA-non-irradiated teeth and sealer UA and no-RT/no-UA-non-irradiated teeth and no sealer UA. Push-out bond strength test was performed in a Universal Testing Machine. Failure modes and adhesive interface were analyzed under Scanning Electron Microscopy. The data were statistically compared (two-way-ANOVA and posthoc Games-Howell test; Fisher's exact test - α = 5%). The different experimental conditions (radiation and UA) and the root third had a significant effect on push-out bond strength, and the interaction of these factors was significant (p < 0.05). UA of the sealer significantly increased its bond strength to both irradiated and non-irradiated dentin (p < 0.05). The irradiated groups mostly presented adhesive-type failure of the sealer (p < 0.01). Regardless of the irradiation, the ultrasonically activated groups showed a more homogeneous adhesive interface, with the presence of sealer tags in greater density and depth. Ultrasonic activation enhanced the intratubular penetration and the bond strength of the endodontic sealer to irradiated dentin. The impact of ultrasonic activation of the endodontic sealer on teeth undergoing radiotherapy is a gap in the scientific literature that needs to be bridged.

Postoperative pain after single-visit root canal treatments in necrotic teeth comparing instruments' kinematics and apical instrumentation limits - a prospective randomized multicenter clinical trial.

OBJECTIVES: This prospective randomized multicenter clinical trial (PRMCT) investigated postoperative pain after single-visit root canal treatments in teeth affected by pulp necrosis (PN), and asymptomatic apical periodontitis (AAP) (with apical radiolucent areas) or normal periradicular tissues (without apical radiolucent areas) comparing different instruments' kinematics and apical instrumentation limits. METHODS: Before chemomechanical preparation, 240 patients/teeth were randomly distributed into four groups (n = 60) according to the instruments' kinematics (rotary or reciprocating) and apical instrumentation limits (with or without intentional foraminal enlargement [IFE]). After that, specimens were submitted to the same irrigation and obturation techniques, and the patients were referred to undergo the definitive restorations. No medication was prescribed, but the patients were instructed to take either paracetamol (750 mg every 6 h for three days) or ibuprofen (600 mg every 6 h for three days) in pain cases. Postoperative pain incidence and levels were assessed at 24-, 48-, and 72 h following treatment completion according to a verbal rating scale (VRS) following a score. The Kolmogorov-Smirnov test was applied to assess the normality of the data. Mann-Whitney U, Chi-square, Friedman's ANOVA, and Friedman's multiple 2 to 2 comparison tests were employed to identify potential significant statistical differences among the variables in the study groups (P < .05). RESULTS: Significant statistical differences were only observed among the groups considering tooth, periradicular status, and the occurrence of overfilling (sealer extrusion) (P < 0.00). Patients with teeth instrumented through rotary kinematics and without IFE experienced lower rates of postoperative pain; however, this difference was relevant only at 24 h (P < 0.05). CONCLUSIONS: Postoperative pain was lower after using a rotary file system (Profile 04) inserted up to the apical constriction (AC). However, this finding was just statistically meaningful at 24 h. TRIAL REGISTRATION: This PRMCT was approved by the Human Research Ethics Committee of the Paranaense University - UNIPAR, Francisco Beltrão, PR, Brazil (CAAE. 46,774,621.6.0000.0109) on 02/09/2021. It was registered at The Brazilian Registry of Clinical Trials - ReBEC (RBR-3r967t) on 01/06/2023, was performed according to the Principles of the Helsinki Declaration and is reported following the Consolidated Standards of Reporting Trials Statement.

Prevalence of postoperative pain after endodontic treatment using low and high concentrations of sodium hypochlorite: a systematic review and meta-analysis.

OBJECTIVES: To determine the prevalence of postoperative pain after endodontic treatment using low (LC) and high (HC) concentrations of sodium hypochlorite (NaOCl). MATERIALS AND METHODS: Six databases and the grey literature were searched to identify randomized clinical trials that evaluated postoperative pain after endodontic treatment using NaOCl. NaOCl concentrations were dichotomized into 'LC' (0.5% to 3%) and 'HC' (≥ 5%) and a proportion meta-analysis was applied to determine the postoperative pain prevalence: overall and according to pain intensity and postoperative time. The prevalence of patients using pain control medication was also determined. A significance level of 5% and a random effect model were applied for data analysis. Between-study heterogeneity was assessed by I2 index. Risk of bias (RoB) was assessed using the Cochrane Risk-of-Bias 2.0 tool. The certainty of evidence was assessed using the GRADE approach. RESULTS: Ten studies were included in the review and eight in the meta-analysis. The overall prevalence of postoperative pain was 45% in LC and 39% in HC. The prevalence of pain in LC and HC after 24 h was 25% and 40%, respectively. After 48 h, the prevalence decreased to 10% in LC and 25% in HC. 'Absent pain' was the most prevalent score. The prevalence of patients who used medication was 9% in LC and 15% in HC. Three studies were classified as 'high RoB', five as 'low RoB', and two as 'some concerns'. The certainty of evidence was very low. CONCLUSIONS: The overall prevalence of postoperative pain after endodontic treatment using LC and HC of NaOCl was 45% and 39%, respectively. CLINICAL RELEVANCE: Postoperative pain is common after endodontic treatment using NaOCl, but tends to decrease over time.

Development and validation of a method for creating incomplete vertical root fracture in extracted teeth.

The present study reported a method for inducing incomplete root fracture in human extracted teeth for the purpose of evaluating the merits of different diagnostic imaging techniques. Thirty-five single-rooted teeth were inspected under magnification and transillumination to exclude previously fractured teeth. Tooth crowns were removed, and the root canals were prepared up to the ProTaper Next X4 (40.06) file. Each root was lined with wax and embedded in a polystyrene resin block. The setup was attached to a universal testing machine for pressing a customized conical wedge (diameter at tip: 0.6 mm; taper: 0.2 mm/mm) into the instrumented canal with a 2 kN load at 5 mm/min. The machine was programmed to stop after a sudden 10% drop in loading force. Each specimen was removed from the resin block and inspected under × 20 magnification and transillumination to identify the fracture characteristics (pattern, surfaces and root-third affected). The gap width of each specimen was measured at different locations along the fracture line. The protocol induced incomplete vertical root fractures in all specimens. Fracture widths were < 100 µm in all specimens (mean gap width: 34.9 µm). The proposed methodology was successful in inducing incomplete vertical root fractures with characteristics that resemble the clinical presentation of these conditions. The method is easy to execute, highly reproducible and helps to minimize bias in laboratory studies that aims to mimic vertical root fractures.

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 1.3 mm-thick dentin slices obtaining samples that were submitted to the push-out test in Universal Testing Machine (Instron, Model 4444-0.5 mm/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.

Does the ultrasonic activation of sealer hinder the root canal retreatment?

OBJECTIVES: To evaluate if the ultrasonic activation of sealer hinders the root canal retreatment. MATERIALS AND METHODS: Thirty mandibular premolars were prepared using the ProTaper Universal system (Dentsply) until the instrument F3 (0.30/0.09). The canals were distributed into 2 groups (n = 15), according to the filling technique: NUact group - sealer without ultrasonic activation + gutta-percha cones and Uact group - sealer with ultrasonic activation + gutta-percha cones. The canals were re-instrumented with Largo burs, followed by the instrument R50 (0.50/0.05) of the Reciproc system. The time required to perform re-instrumentation was recorded (s). The roots were longitudinally cleaved, and the total area of root canal and remaining filling material were quantified (%). The ANOVA test was applied to the data and complemented by Student's t test (P < 0.05). RESULTS: Uact group had higher percentage of remaining filling material than NUact group (P < 0.05). When the root thirds were considered, there was statistically significant difference only for Uact group at the apical third (P < 0.05). There was no difference between groups regarding the time required to perform re-instrumentation (P > 0.05). CONCLUSIONS: Ultrasonic activation of sealer leads to a higher percentage of remaining filling material attached to the root canal walls. However, it did not affect the retreatment time. CLINICAL SIGNIFICANCE: Ultrasonic activation increases sealer penetration into dentinal tubules, improving its resistance to dislodgement. However, there is no scientific evidence to prove if ultrasonic activation of sealer hinders its removal when root canal retreatment is necessary.

Effectiveness of different anesthetic methods for mandibular posterior teeth with symptomatic irreversible pulpitis: a systematic review and meta-analysis.

OBJECTIVE: This systematic review aimed to assess the effectiveness of anesthetic methods for mandibular posterior teeth with symptomatic irreversible pulpitis, comparing to the inferior alveolar nerve block (IANB) by meta-analysis. MATERIALS AND METHODS: Studies were identified from Cochrane Library, Embase, Lilacs, PubMed, Scopus, and Web of Science databases up to May 2021. Randomized clinical trials comparing the anesthetic success rate of IANB and any other alternative anesthetic method were included. The quality of the selected studies was assessed by the Cochrane Risk of Bias 2.0 tool. Meta-analyses using Mantel-Haenszel method and random-effect models were performed to find the pooled estimates of risk ratio (RR) with 95% confidence interval (CI). The quality of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation approach. RESULTS: Twenty-two studies were selected, which included fourteen anesthetic methods. Two studies were classified as high risk of bias, five as uncertain risk and fifteen as low risk. Vazirani-Akinosi nerve block (VANB) [RR = 1.27; p = 0.007; 95% CI, 1.07-1.52; I2 = 0%] and intraosseous injection (IOI) [RR = 1.48; p = 0.04; 95% CI, 1.02-2.15; I2 = 46%] had superior effectiveness compared to IANB, with low certainty of evidence, as well as buccal infiltrations associated with IANB (BI + IANB) [RR = 1.84; p = 0.004; 95% CI, 1.22-2.79; I2 = 52%], with very low certainty. CONCLUSION: Evidence suggests that buccal infiltrations associated with IANB, VANB, and IOI are more effective than IANB at anesthetizing posterior mandibular teeth with symptomatic irreversible pulpitis. CLINICAL SIGNIFICANCE: Alternative primary methods of anesthesia might be indicated for mandibular posterior teeth presenting symptomatic irreversible pulpitis.

Tooth discoloration induced by the different phases of a calcium aluminate cement: One-year assessment.

OBJECTIVES: To assess the discoloration of teeth treated with the different phases of calcium aluminate cement (CAC), in comparison with the conventional CAC and mineral trioxide aggregate (MTA). MATERIALS AND METHODS: Fifty bovine incisors were prepared and filled. Two millimeters of the filling was removed to fabricate a cervical plug with the following cements (n=10): CA(CaO.Al2 O3 ); CA2 (CaO.2Al2 O3 ); C12 A7 (12CaO.7Al2 O3 ); CAC and MTA. The initial color measurement was performed and after 7, 15, 30, 45, 90, 180, and 365 days new color measurements were performed to determine the color (ΔE00 ), lightness (ΔL'), chroma (ΔC'), hue differences (ΔH'), and the whiteness index (WID ). RESULTS: ΔE00 was significant for groups (p = 0.036) and periods (p < 0.05). The greater ΔE00 was observed after 365 days for CAC (12.8). C12 A7 (7.2) had the smallest ΔE00 . ΔL' and ΔC' were significant for groups and periods (p < 0.05). ΔH' was significant for periods (p < 0.05). After 365 days, significant reduction in lightness was observed for all groups. For CA, CA2 , CAC, and MTA groups, the WID values decreased over time (p < 0.05). CONCLUSIONS: The tested cements changed the color behavior of the samples, resulting in greater teeth darkening over time. CLINICAL SIGNIFICANCE: There is no long-term study assessing the discoloration induced by the different phases of CAC.

Comparison of two observational methods, scanning electron and confocal laser scanning microscopies, in the adhesive interface analysis of endodontic sealers to root dentine.

OBJECTIVES: To compare the accuracy of confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) during the analysis of the adhesive interface integrity and intratubular penetration of root canal sealers to radicular dentine. MATERIALS AND METHODS: Twenty roots of human maxillary incisors were prepared and distributed into two groups (n = 10), followed by filling with gutta-percha and Endofill (G1) or AH Plus (G2). After 7 days, roots were sectioned and analyzed under CLSM and SEM. Score systems were used to evaluate the adhesive interface integrity (0-4) and sealer intratubular penetration (0-3). Data were submitted to Wilcoxon-Mann-Whitney and Kendall correlation statistical tests (α = 5%). RESULTS: In the adhesive interface analysis, CLSM was similar (P = 0.157) to SEM for Endofill; however, the results were different for AH Plus (P = 0.029). Intratubular penetration had significant difference between observational methods for both sealers (P < 0.0001). Correlation analysis between SEM and CLSM for adhesive interface was moderate for Endofill and low for AH Plus. Intratubular penetration was low for both sealers. CONCLUSION: SEM and CLSM analysis had similar results when sealers were compared, with a more homogeneous adhesive interface, and greater intratubular penetration for AH Plus. Comparison between observational methods demonstrated low positive correlation for adhesive interface and intratubular penetration analysis. CLINICAL RELEVANCE: A proper interface formed between sealer and dentine is very important for final quality of root canal filling. Observational methods which allow an accurate analysis of this interface must be selected to assess such features.

Bacterial penetration into filled root canals exposed to different pressures and to the oral environment-in vivo analysis.

OBJECTIVES: The study aims to correlate the depth of bacterial penetration into filled root canals with the time of exposure to the oral environment and different pressures. MATERIALS AND METHODS: One-hundred and twenty-two root canals of male Beagle dog teeth were prepared and filled. The root canals were distributed into three groups, according to the pressure applied: (A) no pressure, (B) 30 kPa, and (C) 60 kPa. Then, the root canals were exposed to the oral environment, establishing sub-groups considering the time intervals of exposure: (1) 45 days and (2) 120 days (n = 17). Sub-groups had positive and negative controls (n = 5). The animals were sacrificed, and the specimens were prepared for histological analysis. RESULTS: There was no significant difference in the bacterial penetration among groups A, B, and C at 45 days (P = 0.903) and 120 days (P = 0.211). No statistically significant difference was found (P = 0.608) between the exposure time intervals. Most of the specimens from experimental groups exposed for 120 days presented moderate inflammatory infiltrate. CONCLUSIONS: Pressures of 30 and 60 kPa did not affect sealing ability of root canal filling. The time of exposure did not influence bacterial penetration, which was limited to the first 4 mm of the root canals exposed for 120 days. CLINICAL RELEVANCE: This animal study demonstrated that disinfection of the first millimeters of root canals could be considered before retreatment of their entire length. However, clinical studies in humans should be conducted before validation of this protocol.

Transdentinal cytotoxicity of resin-based luting cements to pulp cells.

OBJECTIVES: The aim of this study was to evaluate the transdentinal cytotoxicity of components released from different resin-based luting cements to cultured MDPC-23 odontoblast-like cells and human dental pulp cells (HDPCs). MATERIALS AND METHODS: Artificial pulp chamber (APC)/dentin disc sets were distributed into four groups according to the materials tested (n = 10), as follows: G1, control (no treatment); G2, resin-modified glass-ionomer cement (RelyX Luting 2); G3, self-adhesive resin cement (RelyX U200); and G4, conventional resin cement (RelyX ARC). The materials were applied to the occlusal surfaces (facing up) of the dentin discs adapted to the APCs. The pulpal surfaces of the discs were maintained in contact with culture medium. Then, an aliquot of 400 µL from the extract (culture medium + resin-based components that diffused through dentin) of each luting cement was applied for 24 h to HDPCs or MDPC-23 cells previously seeded in wells of 24-well plates. Cell viability analysis was performed by the MTT assay (1-way ANOVA/Tukey test; α = 5 %). RESULTS: For MDPC-23 cells, RelyX ARC (G4) and RelyX Luting 2 (G2) caused greater reduction in cell viability compared with the negative control group (P < 0.05). Only the HDPCs exposed to RelyX ARC (G4) extract showed a tendency toward viability decrease (9.3 %); however, the values were statistically similar to those of the control group (G1) (P > 0.05). CONCLUSIONS: In accordance with the safe limits of ISO 10993-5:1999 (E) recommendations, all resin-based luting cements evaluated in this study can be considered as non-toxic to pulp cells. CLINICAL RELEVANCE: Cytotoxicity of resin-based luting cements is material-dependent, and the different protocols for the application of these dental materials to dentin may interfere with their cytotoxicity.

How Does Intentional Apical Foraminal Enlargement Affect the Foramen and Root Canal Morphology?

INTRODUCTION: This study assessed the effect of intentional foraminal enlargement on the foramen and the apical root canal morphology. METHOD: Sixty mesial roots of mandibular molars were scanned by micro-computed tomography. Their apical foramina were photographed with a stereomicroscope before and after preparation. Three groups were formed (n = 20) according to the working length (WL). G-1: foramen - 1 mm; G0: foramen; and G+1: foramen + 1 mm. Each group originated 2 subgroups (n = 10): G-1: Buchanan's patency (size 10 K-type file) and foraminal debridement (sizes 20, 25 and 30 K-type files); G0 and G+1: rotary foraminal enlargement (ProDesign S size 25/.08) or reciprocating foraminal enlargement (R25). The area, perimeter, transportation, and noninstrumented walls of the foramen were evaluated. The root canal transportation and the centering index of preparation at 1, 3 and 5 mm from the foramen were also assessed. Data were compared statistically (α = 5%). RESULTS: The instruments used at the foramen and 1 mm beyond promoted foraminal enlargement and transportation. Regarding NIW, there was no difference between mechanized foraminal enlargements performed at the foramen or 1 mm beyond, similar to the manual foraminal debridement group (P > .05). There was no difference in transportation and centralization at 1-, 3-, and 5-mm apical levels, regardless of the instrumentation systems. CONCLUSION: Mechanical preparation at the foramen, or 1 mm beyond, resulted in foraminal enlargement, transportation and were not able to touch all root canal walls that delimit the foramen.

Comparative Analysis of AH Plus Bond Strength to Root Canal Dentin and Adhesive Interface Quality after Calcium Hydroxide Removal using Different Irrigation Protocols.

INTRODUCTION: To evaluate the push-out bond strength (POBS) of AH Plus sealer to root dentin and the adhesive interface quality after calcium hydroxide (Ca(OH)2) intracanal dressing removal with different final irrigation protocols. METHOD: After root canal instrumentation and irrigation, 40 root canals were filled with Ca(OH)2 and sealed. After 14 days, the specimens were randomly distributed according to the irrigation protocols for Ca(OH)2 removal (n = 10): GH2O (control) - distilled water; GNaOCl - 1% NaOCl; GEDTA - 17% EDTA; GEDTA + NaOCl - 17% EDTA + 1% NaOCl. The root canals were filled with AH Plus sealer and gutta-percha. After 7 days, the roots were sectioned into dentin slices and submitted to POBS test and analysis of the adhesive interface under scanning electron microscope. The POBS data were statistically evaluated (analysis of variance and Tukey test). The Kruskal-Wallis and Mann-Whitney tests were used to analyze the adhesive interface (α = 0.05). RESULTS: GH2O, GNaOCl, and GEDTA + NaOCl had similar POBS values, with higher values on the apical third, in comparison with other thirds (P < .05). A homogeneous and free-of-gaps adhesive interface was observed for GH2O, GNaOCl, and GEDTA + NaOCl, with difference between GH2O and GEDTA (P < .05). GH2O and GEDTA + NaOCl presented higher sealer tags formation (P < .05). CONCLUSION: The final rinse with EDTA for Ca(OH)2 dressing removal had a negative effect on the POBS of the filling material to root dentin. The use of EDTA followed by NaOCl had results similar to the distilled water, providing uniform and free-of-gaps adhesive interface, and a higher number of sealer tags.

Can Heated Distilled Water Effectively Prevent Precipitate Formation between NaOCl and CHX?

Introduction: The present study aimed to investigate the capacity of different irrigation protocols using heated distilled water at 65°C (HDW), in preventing the formation of the brown-orange precipitate observed after the interaction between sodium hypochlorite (NaOCl) and chlorhexidine (CHX). Methods: Forty human canines were selected, prepared, and cleaved in two halves. Images of delimited areas in each root canal thirds were obtained through a stereomicroscope (16x and 40x). After reassembly, the teeth were distributed into four groups (n = 10) according to the final irrigation protocol: G1 (no HDW): EDTA + NaOCl + CHX with conventional irrigation (CI); G2 (HDW + CI): EDTA with passive ultrasonic irrigation (PUI) + NaOCl (PUI) + HDW (CI) + CHX (PUI); G3 (HDW + PUI): EDTA + NaOCl + HDW + CHX with PUI; G4 (HDW + CUI): EDTA (PUI) + NaOCl (PUI) + HDW with continuous ultrasonic irrigation (CUI) + CHX (PUI). After irrigation, the teeth were re-separated and images of the same delimited areas were obtained again. Scores were assigned according to the amount of precipitate observed, comparing the initial and final images. The data were submitted to Kruskal-Wallis, Dunn and Friedman statistical tests (α = 5%). Results: G1(no HDW) showed the highest scores in the analysis between groups (p < 0.001), with a greater amount of precipitate in the cervical and medium thirds (p < 0.001). The thirds of the other experimental groups did not differ from each other (p > 0.05). Conclusion: The intermediate irrigation with heated distilled water at 65°C prevented the formation of brown-orange precipitate, regardless of the use of ultrasonic activation (PUI or CUI).