Efficacy of root-end filling techniques using premixed putty type bioceramic cements: an ex vivo study.

OBJECTIVES: Currently, premixed putty-type bioceramic cements (PPBCs) have become popular materials for root-end fillings. This study investigated three root-end filling techniques using PPBCs and calcium silicate-based sealers including EDTA pretreatment. MATERIALS AND METHODS: Ninety root segments were prepared and standardized with an artificial fin and lateral canal, and assigned to three groups (n = 30). Root-end fillings were placed using BC-RRM Putty alone (Group PA), injection of BC sealer followed by BC-RRM Putty (Lid Technique: Group LT) or BC-RRM Putty with BC sealer coating (Deep putty packing technique: Group DP). Half of each group was pretreated with 17% EDTA. The radiographic images of the specimens were assessed by five graders and push-out bond strength tests were conducted. The data were analyzed with a general linear model including two-way ANOVA and chi-square test at a significance level of 5%. RESULTS: DP approach demonstrated significantly higher bond strength than LT (P < 0.05). However, there was no statistically significant difference in bond strength between PA and either DP or LT. EDTA pretreatment had no significant effect on push-out bond strength. Radiographically, for the main canal, PA and DP scored significantly higher than LT. In the fin, PA scored significantly higher than others (P < 0.05). CONCLUSION: Our study highlights variations in root-end filling techniques. Injecting a bulk of bioceramic sealer before the placement of PPBCs may reduce bond strength and radiopacity. The application of PPBCs alone or in the deep putty technique demonstrates potential for favorable outcomes. EDTA pretreatment did not enhance bond-strength. CLINICAL RELEVANCE: Careful selection and application of bioceramic materials and techniques in root-end fillings may influence the outcome of endodontic root-end surgery. When PPBCs and calcium silicate-based sealers are used together for root-end fillings, sealer followed by deep putty application may offer improved bond strength and radiographic fill compared to the lid technique.

Healing of apical periodontitis through modern endodontic retreatment techniques.

The presence of apical periodontitis in teeth which have undergone initial root canal treatment is largely attributed to bacteria residing in or invading from the apical root canal space. Bacteria-associated apical periodontitis will not heal spontaneously, nor will systemic antibiotics eradicate the infection. Only endodontic retreatment, endodontic surgery, or extraction will control the bacterial etiology. Modern retreatment is an effective means of addressing apical periodontitis. A mandibular premolar with apical periodontitis, apical root resorption, and overfilled gutta percha was retreated with post removal, retrieval of gutta percha from beyond the apex, ultrasonic irrigation and disinfection, and placement of a collagen internal matrix to facilitate a well-controlled MTA apical fill. The magnification and illumination imparted by the operating microscope was integral to achievement of treatment objectives. The patient's symptoms were resolved and complete osseous healing occurred. During treatment planning, clinicians should consider the capability of modern endodontic techniques to overcome technical challenges, often allowing the natural dentition to be preserved and restored to function days after retreatment.

Calcium Silicate-based Sealer Extrusion into the Mandibular Canal: 3 Different Recovery Outcomes-A Report of 3 Cases.

The use of calcium silicate-based sealers (CSSs) is increasing in dentistry as a result of their favorable properties. The inadvertent extrusion of these sealers into the mandibular canal (MC) can result in temporary or permanent neurosensory alterations. Three different recovery outcomes of CSS extrusion into the MC after endodontic treatment of mandibular molars confirmed by cone-beam computed tomographic imaging are described. In Case 1, CSS from the mesiolingual canal of tooth #31 was extruded into the MC during obturation. The patient reported paresthesia. The symptoms of paresthesia were completely resolved by 9 months. In Case 2, CSS from the mesial canals of tooth #30 was extruded into the MC during obturation. A "plasmalike spreading pattern" of the extruded sealer was observed on the radiographs. The patient reported paresthesia and dysesthesia. In addition, the patient complained of hyperalgesia with heat and mechanical allodynia. The symptoms continued to persist during follow-up. At 22 months, the patient still reported persistent paresthesia, hyperalgesia, and mechanical allodynia, affecting the ability to eat. In Case 3, CSS from the distal canal of tooth #31 was extruded into the MC during obturation. The patient did not report any paresthesia or dysesthesia. All 3 patients elected a follow-up approach and monitoring rather than surgical intervention. These cases illustrate the need for the development of guidelines for the management of iatrogenic CSS extrusion into the MC because such an occurrence may result in permanent, temporary, or no neurosensory alterations.

Physicochemical and Biological Properties of AH Plus Bioceramic.

INTRODUCTION: The purpose of this study was to evaluate the physicochemical and biological properties of AH Plus Bioceramic (AHPB; Dentsply Sirona, Charlotte, NC) in comparison to AH Plus (AHP, Dentsply Sirona) and EndoSequence BC Sealer (BC; Brasseler, Savannah, GA). METHODS: The setting time, radiopacity, flow, solubility, calcium ion release, and pH were evaluated following ISO guidelines. Surface characterization and chemical constitution were evaluated by scanning electron microscopy/energy-dispersive X-ray spectroscopy. The antibacterial effect was tested against Enterococcus faecalis. Sealer cytotoxicity was tested using the XTT cell viability assay. Analysis of variance, Tukey, and unpaired t tests were used with a significance level of 5%. RESULTS: The initial setting time of AHPB was shorter than AHP and BC (P ≤ .0001), whereas AHP showed a shorter final setting time (P ≤ .0001). AHPB was more radiopaque than BC (P = .0012) but less radiopaque than AHP (P = .0001). AHPB was more soluble than AHP (P ≤ .0001), whereas no difference was observed between AHPB and BC (P > .05). Immersion in phosphate-buffered saline decreased the solubility of AHPB and BC (P ≤ .005). AHPB calcium ion release was higher than AHP (P ≤ .05) but less than BC (P ≤ .0001). AHPB had the highest flow followed by AHP and BC (P > .05). All sealers were alkaline and able to eradicate E. faecalis. Surface morphology and chemical composition of all sealers changed after immersion in water and phosphate-buffered saline. Cell viability for AHPB and BC was higher than AHP (P ≤ .0001). CONCLUSIONS: AHPB presented adequate properties to be considered a good sealer, however, the high solubility may negatively impact the quality of the obturation.

Differentially Expressed Genes in Dental Pulp Tissues of Individuals With Symptomatic Irreversible Pulpitis With and Without History of COVID-19.

INTRODUCTION: Increased levels of proinflammatory markers have been reported in tissues of individuals with Coronavirus Disease 2019 (COVID-19). We hypothesize that inflamed dental pulp tissues of individuals with previous history of COVID-19 may present a differential inflammatory gene expression profile in comparison with individuals who never had COVID-19. MATERIALS AND METHODS: Dental pulp tissues were collected from 27 individuals referred for endodontic treatment due to symptomatic irreversible pulpitis. Of these, 16 individuals had a history of COVID-19 (6 months to 1 year post infection) and 11 individuals had no previous history of COVID-19 (controls). Total RNA from pulp tissue samples was extracted and subjected to RNA sequencing for comparison of differentially expressed genes (DEGs) among groups. DEGs showing log2(fold change) > 1 or < -1, and P < .05 were considered significantly dysregulated. RESULTS: RNA sequencing identified 1461 genes as differentially expressed among the groups. Of these, 311 were protein coding genes, 252 (81%) that were upregulated and 59 (19%) that were downregulated in the COVID group compared with controls. The top upregulated genes in the COVID group were HSFX1 (4.12-fold change) and LINGO3 (2.06-fold change); significantly downregulated genes were LYZ (-1.52-fold change), CCL15 and IL8 (-1.45-fold change). CONCLUSIONS: Differential gene expression in dental pulp tissues of COVID and non-COVID groups suggests potential contribution of COVID-19 on dysregulating inflammatory gene expression in the inflamed dental pulp.

Treating Nerve Injury after Endodontic Microsurgery Using Laser Photobiomodulation: A Report of 2 Cases.

The purpose of this case report was to inform dentists and dental specialists about a noninvasive, viable treatment option that could aid in the recovery of patients who have experienced iatrogenic nerve injuries. Nerve injury is an inherent risk of many dental procedures and a complication that can negatively impact a patient's quality of life and activities of daily living. Managing neural injuries presents a challenge for clinicians because there are no standard protocols reported in the literature. Although spontaneous healing of these injuries can occur, the duration and degree of healing can vary greatly between individuals. Photobiomodulation (PBM) therapy is used as an adjunct in medicine for functional nerve recovery. Once target tissues are illuminated with a low-level laser during PBM, the light energy is absorbed by the mitochondria causing adenosine triphosphate production, modulation of reactive oxygen species, and the release of nitric oxide. These cellular changes explain why PBM has been shown to aid in cell repair, vasodilation, a reduction in inflammation, accelerated healing, and an improvement in postoperative pain. This case report presents 2 patients with neurosensory alterations after endodontic microsurgery with a significant improvement in their condition after PBM treatment using a 940-nm diode laser.

The effect of endodontic access preparation on the failure load resistance of a 3Y-TZP monolithic zirconia crown.

The effect of endodontic access preparation on the failure load resistance of 3Y-TZP zirconia crowns was accomplished by preparing human molars and luting monolithic zirconia crowns with a self-adhesive resin cement. Besides the intact control, teeth received endodontic access preparations and then grouped (n = 12) into a positive control (no access repair), dentin core replacement only and complete access repair groups. Specimens were axially tested until failure with results of no significant difference between the failure load of intact controls and the complete access repair group. However, the positive control and dentin replacement only groups failed at significantly lower loads. Under the conditions of this study, there was no significant failure load difference between 3Y-TZP monolithic zirconia crowns with repaired endodontic access preparations to that evidenced by an unprepared control. Although this evidence is encouraging, caution is advised and definitive recommendations cannot be made until verified by clinical studies.

Dislodgement pushout resistance of five bioceramic root-end filling materials.

This study evaluated the dislodgement push-out resistance of five bioceramic materials. One hundred single-rooted teeth with one canal had the apical 3 mm and crown resected to create a 14 mm standardized length. The canals were instrumented to an apical size 80 with a 3 mm root-end preparation made with ultrasonic diamonds. The prepared roots were randomly divided into 5 root-end restorative groups (n=20). ProRoot MTA, Biodentine, EndoSequence Root Repair Material, EndoSequence Fast Set Putty, and EndoSequence BC Sealer with each material placed following manufacturer's instructions and stored at 100% humidity for 2 weeks. An apical-to-coronal static testing load with the identified dislodgement force converted into MPa with mean results analyzed with Kruskal-Wallis and Dunn's post hoc tests (α=0.05). ProRoot MTA and Biodentine displayed similar push-out stress resistance and exhibited significantly greater stress resistance than the similar Endosequence materials. However, all materials failed cohesively and were not dislodged from the root canal surface.

Retrievability of Calcium Silicate-based Root Canal Sealers During Retreatment: An Ex Vivo Study.

INTRODUCTION: The retrievability of calcium silicate-based sealers (CSSs) during nonsurgical retreatment has been equivocal. This study compared the retrievability of 3 different CSSs using 1 of 3 different solutions or no solution. METHODS: A total of 130 extracted teeth with a straight canal were decoronated to a standardized root length. The canals were instrumented to 35/.04 and divided into 3 groups (BC: EndoSequence BC sealer; EBC: EdgeBioceramic; NEO: NeoSEALERFlo), and each group was further divided into 4 subgroups (6% sodium hypochlorite; 5% acetic acid; carbonated water; no solution). After sealer placement, each master gutta-percha cone was placed intentionally 2 mm short of the working length (WL) to ensure the apical 2 mm was filled only with sealer. After storage for 21 days at 37°C and 100% humidity, retreatment was performed until apical patency was obtained. The operator was blinded to the CSS and solution used. Data were analyzed using analysis of variance to compare apical patency rates and the mock chair-times. RESULTS: Overall success rates for apical patency in BC, EBC, and NEO were 63.64%, 69.77%, and 100%, respectively. There was significantly higher apical patency rate in NEO than BC and EBC. The chair-time for NEO was significantly shorter than BC (P < .05) and EBC sealer (P < .001). There was no significant difference in the chair-time between BC and EBC sealer groups. CONCLUSION: BC, EBC, and NEO sealers in a straight canal were consistently retrievable when no solution was used. Compared with no solution, the retrievability of BC, EBC, and NEO decreased when solutions were used.

Evaluation of the Physicochemical and Biological Properties of EndoSequence BC Sealer HiFlow.

INTRODUCTION: Understanding the physicochemical and biological properties of endodontic sealers is important for endodontic treatment planning. This study evaluated the properties of EndoSequence BC Sealer HiFlow (BCH; Brasseler USA, Savannah, GA), EndoSequence BC Sealer (BC, Brasseler USA), and AH Plus (AHP; Dentsply DeTrey, Konstanz, Germany). The effect of temperature on the setting time and flow of these sealers was also evaluated. METHODS: The setting time, flow, radiopacity, pH, solubility, and calcium release were investigated following ISO guidelines. The morphology and chemical composition of the sealers were evaluated by scanning electron microscopy and energy-dispersive spectroscopy. The antibacterial activity of sealers was tested against 2 strains of Enterococcus faecalis. Sealer cytotoxicity and the effects on messenger RNA expression of proinflammatory and mineralization genes were also investigated. Data analysis was performed using analysis of variance, Tukey, Kruskal-Wallis, and Dunn multiple comparison tests. P ≤ .05 was considered statistically significant. RESULTS: The setting time and flow rate of all sealers were affected by heat (P ≤ .05). The setting times and solubility of BCH and BC were significantly higher than AHP (P ≤ .0001). The radiopacity of AHP was higher than BCH and BC (P ≤ .0001). All sealers were alkaline and had antibacterial effects. Cell viability was higher for BCH and BC than AHP (P ≤ .0001). No significant differences in messenger RNA expression of proinflammatory and mineralization genes were observed. CONCLUSIONS: Overall, BCH and BC had similar physicochemical and biological properties. The observed high solubility of BCH and BC as well as the high cytotoxicity of AHP might negatively impact the clinical performance of these materials. The application of heat affected the setting time and flow of all sealers.

Root Surface Changes in Endodontically Treated Teeth following Orthodontic Movement.

INTRODUCTION: Orthodontically induced external root resorption has been labeled an unavoidable consequence of orthodontic tooth movement (OTM). The objective of this study was to investigate the change in surface area (mm2) and volume (mm3) of endodontically treated teeth (ETT) compared with contralateral teeth with a vital pulp (VPT) after OTM. METHODS: Seventy-six teeth were included in this retrospective analysis: ETT (n = 38) and VPT (n = 38). All teeth were evaluated using cone-beam computed tomographic imaging at 2 time periods: before OTM (T1) and after OTM (T2). Study teeth were segmented to include all areas contained within the lamina dura and then were converted into a mesh model for data calculation. The surface area (mm2) and volume (mm3) of each tooth were calculated at T1 and T2 based on the number of cubic voxels present within the mesh model. Statistical analysis was performed using a linear mixed-effects model. RESULTS: The average change in surface area after OTM in ETT was 13.01 mm2 and 19.95 mm2 in VPT (P < .05). The average percent change in surface area after OTM in ETT was 2.09% and 3.38% in VPT (P < .05). The average change in volume after OTM in ETT was 22.48 mm3 and 32.44 mm3 in VPT (P < .05). The average percent change in volume after OTM in ETT was 2.62% and 4.10% in VPT (P < .05). CONCLUSIONS: The results from this study suggest that ETT are less susceptible to root resorption after OTM than their vital counterparts.

Vascular Endothelial Growth Factor and/or Nerve Growth Factor Treatment Induces Expression of Dentinogenic, Neuronal, and Healing Markers in Stem Cells of the Apical Papilla.

INTRODUCTION: The goal of regenerative endodontic procedures is to preserve and stimulate stem cells from the apical papilla (SCAPs) to develop the pulp-dentin complex using various growth factors and scaffolds. We hypothesized that the treatment of SCAPs with vascular endothelial growth factor (VEGF) or nerve growth factor (NGF) may impact the expression of osteogenic and dentinogenic markers. METHODS: The optimum concentration of VEGF and NGF on SCAP viability was assessed and introduced to SCAPs for 6-24 hours. SCAPs were also challenged with Escherichia coli lipopolysaccharide (LPS). Messenger RNA (mRNA) expression of DSPP, DMP1, TGFB1, OCN, SP7, and TWIST1 was examined via quantitative reverse transcription polymerase chain reaction. Immunohistochemistry was used to verify protein expression. In addition, total RNA from NGF-treated SCAPs in the presence or absence of LPS was extracted for RNA sequencing. RESULTS: Compared with untreated cells, NGF-treated SCAPs showed markedly higher levels of DSPP, DMP1, and TGFB1 mRNAs (>9-fold change, P < .05), and SCAPs treated with both VEGF and NGF showed a significant increase of DSPP and TGFB1 mRNAs (P < .05). In addition, in LPS-challenged SCAPs, treatment with these growth factors also exhibited increased expression of DSPP, DMP1, and TGFB1 mRNAs, with the most significant change induced by VEGF (P < .05). Immunohistochemistry confirmed increased dentin sialophosphoprotein, dentin matrix acidic phosphoprotein 1, and transforming growth factor beta 1 protein expression in treated SCAPs. RNA sequencing revealed multiple pathways regulated by NGF, including TGF-ß and neurogenic pathways. CONCLUSIONS: VEGF- and NGF-induced dentinogenic/neuronal/healing marker expression in SCAPs indicates the potential value of applying these growth factors in regenerative endodontic procedures.

Evaluating the substantivity of silver diamine fluoride in a dentin model.

OBJECTIVES: The goal of endodontic therapy is to prevent apical periodontitis. This is achieved by biomechanical preparation, microbial control using endodontic irrigants, and complete obturation of the canal space. In order to prevent possible post-obturation complications and for an added antimicrobial effect, substantivity is a desired characteristic of endodontic irrigants. Currently the most commonly used endodontic irrigant that produces an antibacterial substantivity effect is chlorohexidine (CHX). Silver diamine fluoride (SDF) is a topically applied agent for managing dental caries and has shown to stop caries lesion progression. The objective of this study was to compare the antimicrobial substantivity effect of 3.8% SDF against other commonly used endodontic irrigants such as 2% CHX and 6.25% Sodium hypochlorite (NaOCl). MATERIAL AND METHODS: Using a diffusion disc assay we determined the antimicrobial activities of 38%, 3.8%, 0.38%, and 0.038% of SDF against the bacterium Enterococcus faecalis OG1RF. Subsequently, we compared the levels of colonization of E. faecalis by scanning electron microscopy (SEM) at 1.5- and 3-week time intervals on dentin pretreated with 3.8% SDF, 6.25% NaOCl, 2% CHX or sterile phosphate buffered saline (PBS). RESULTS: The diffusion disc assay demonstrated that 38% and 3.8% of SDF inhibited the growth of E. faecalis. Moreover, the substantivity of 3.8% SDF (p < 0.01) was comparable to 2% CHX (p < 0.01) and it is significantly greater than 6.25% of NaOCl compared to the PBS treated samples after 1.5 and 3 weeks of incubation. CONCLUSIONS: In this study, we demonstrate that SDF possesses antimicrobial properties against the opportunistic pathogen E. faecalis. Moreover, using a dentin model we show the substantivity of 3.8% SDF is significantly greater than 6.25% NaOCl, but is comparable to 2% CHX.

pH changes in external root surface cavities after calcium hydroxide is placed at 1, 3 and 5 mm short of the radiographic apex.

The purpose of this study was to test the null hypothesis that there is no difference in the pH on the external apical dentin surface when the canal is completely filled with calcium hydroxide or when it is placed 3 or 5 mm short of the apical foramen in extracted human teeth. The root canals of single-rooted anterior human teeth were cleaned and shaped after decoronation. Cavities about 0.50 mm deep and 1.0 mm wide located at 1, 3 and 5 mm from the radiographic apex were prepared on the external root surface and the teeth were randomly divided into four groups. The roots were filled with calcium hydroxide at 1, 3 and 5 mm from the radiographic apex, and the control group was left empty. pH readings were obtained at intervals over a 28-day study. The roots which were filled within 1 mm of the radiographic apex had the greatest increase in pH in each of the cavities. These results demonstrate that the greatest pH change on the external root surface near the apex is obtained when the canal is more completely filled with calcium hydroxide.

Shear Bond Comparison between 4 Bioceramic Materials and Dual-cure Composite Resin.

INTRODUCTION: Bioceramic materials have shown biologic and physical properties favorable for regenerative treatment. A key to treatment success is an adequate restoration to prevent microleakage; however, research is limited regarding the bond strength between restorative and bioceramic materials used in regenerative procedures. This study compared the bond strength between 4 bioceramic materials and a dual-cure composite resin. METHODS: Eighty wells in Teflon (ePlastics, San Diego, CA) blocks were filled with bioceramic materials representing 4 groups: White ProRoot mineral trioxide aggregate (MTA) (Dentsply Tulsa Dental, Tulsa, OK), Biodentine (Septodont, Saint Maur des Fosses, France), EndoSequence Root Repair Material Fast Set Putty (Brasseler USA, Savannah, GA), and NeoMTA (Avalon Biomed Inc, Houston, TX). After allowing samples to set according to the manufacturers' instructions, exposed surfaces of the bioceramic materials were prepared using ClearFil SE Bond (Kuraray America, Inc., New York, NY) followed by restoration with ClearFil DC Core Plus (Kuraray America, Inc.). To test shear bond strength, each block was secured in a universal testing machine, and the crosshead was advanced at 0.5 mm/min until fracture. Newton peak force was recorded and megapascals calculated followed by data comparison. RESULTS: The mean shear bond strengths between ClearFil DC Core Plus and the bioceramic materials were as follows: White ProRoot MTA, 7.96 MPa; Biodentine, 9.18 MPa; EndoSequence Root Repair Material Fast Set Putty, 4.47 MPa; and NeoMTA, 5.72 MPa. White ProRoot MTA and Biodentine were statistically similar, with a higher stress bond strength than NeoMTA, which had a statistically greater bond strength than EndoSequence Root Repair Material. All these values were lower than typical bond strengths shown for dentin-composite resin bonding. CONCLUSIONS: The choice of which bioceramic material to use in regenerative procedures should be based on factors other than the bond between that material and the overlying coronal resin restoration.

The Effects of Irrigants on the Survival of Human Stem Cells of the Apical Papilla, Including Endocyn.

INTRODUCTION: Endocyn, a pH-neutral solution of hypochlorous acid and hypochlorite has been developed for use as an endodontic irrigant. The purpose of this study was to evaluate the effect of Endocyn on human periodontal ligament (PDL) fibroblasts, rat osteosarcoma cells (UMR-106), and stem cells of the apical papilla (SCAP) compared with other commonly used endodontic irrigants. METHODS: To determine cytotoxicity, cells were exposed to various concentrations of Endocyn, 6% sodium hypochlorite (NaOCl), 17% EDTA, and 2% chlorhexidine for 10 minutes, 1 hour, or 24 hours. Cell survival was measured fluorescently using calcein AM. Endocyn also was tested for its ability to inhibit SCAP proliferation and alkaline phosphatase activity. Finally, SCAP transcript expression was examined via reverse-transcriptase polymerase chain reaction. RESULTS: Endocyn was no more toxic to PDL and UMR cells than water for up to 24 hours. Endocyn concentrations of 50% were toxic to SCAP after 1 hour of exposure. Endocyn concentrations of >20% inhibited SCAP proliferation, whereas concentrations of ≥10% inhibited alkaline phosphatase activity. Exposure of SCAP to 10% Endocyn for 3 days did not alter most transcript expression, but did significantly reduce the expression of alkaline phosphatase, fibromodulin, and osteomodulin. CONCLUSION: Endocyn was significantly less cytotoxic to PDL, UMR-106, and SCAP cells compared with other commonly used endodontic irrigants. High concentrations of Endocyn did inhibit some transcript expression and alkaline phosphatase activity, indicating a potential reduction in the osteogenic potential of stems cells exposed to Endocyn.

Fracture resistance of simulated immature teeth filled with resilon, gutta-percha, or composite.

The purpose of this study was to evaluate the fracture resistance gained by filling root canals of simulated immature teeth with either Resilon, gutta-percha, a self-curing flowable composite resin (BisFil 2B), or a self-curing hybrid composite resin (BisFil II). Seventy-two sheep incisors were divided into six groups of 12 teeth each. Negative controls received no treatment. Teeth in all other groups were prepared until a size 120 LightSpeed LSX instrument could be passed out the apex. After apical placement of a mineral trioxide aggregate (MTA) barrier, the canals were filled with their respective test material to the facial CEJ. The positive control canals were left unfilled. The access openings (including positive controls) were restored with BisFil II. Each root was horizontally fractured through the test material using an Instron. The mean peak loads to fracture were recorded. The hybrid composite resin (BisFil II) was the only material significantly more fracture resistant than positive controls (p < 0.017).

Cyclic fatigue of EndoSequence and K3 rotary files in a dynamic model.

The cyclic fatigue resistance of K3 and EndoSequence files was compared by rotating files against a highly polished surface inclined at 15 degrees to the horizontal. For each brand, files with a 25 tip in .04 and .06 taper and files with a 40 tip in .04 and .06 taper were tested at both 300 and 600 rpm. A 3-mm axial movement simulated a clinical pecking motion at 1 cycle per second. The number of rotations to failure was calculated and analyzed by using analysis of variance and Independent Student's t tests, with results confirmed by nonparametric Mann-Whitney U tests with a Bonferroni correction. At both 300 and 600 rpm, K3 files exhibited statistically significantly more cycles to fracture than their EndoSequence counterparts with the same tip size and taper. Scanning electron microscopy images demonstrated surface features consistent with fracture due to cyclic fatigue. In this model, file design appeared to be the most important determinant of cyclic fatigue resistance.

Effects of pH and mixing agents on the temporal setting of tooth-colored and gray mineral trioxide aggregate.

The purpose of this study was to test the compressive strength of white mineral trioxide aggregate (WMTA) and gray mineral trioxide aggregate (GMTA) when mixed with sterile water or local anesthetic and exposed to an acidic environment. A total of 248 samples of WMTA and GMTA were mixed and placed in phosphate-buffered saline (PBS), at pH 5.0 or 7.4, for a period of 7 or 28 days. When WMTA and GMTA were mixed with local anesthetic, the following were observed: 1) pH 5.0 caused a significant decrease in compressive strength (p<0.0001); 2) WMTA was significantly stronger than GMTA (p<0.0001); and 3) more time in PBS (total 28 days) caused a significant decrease in compressive strength (p<0.001). There were no consistent differences in compressive strength for WMTA or GMTA when mixed with sterile water. Variability of results suggests both types of MTA be mixed with sterile water in acidic and neutral environments.

The anti-microbial effect against enterococcus faecalis and the compressive strength of two types of mineral trioxide aggregate mixed with sterile water or 2% chlorhexidine liquid.

The purpose of this in vitro study was 2-fold: First, to compare the antimicrobial effect of gray and tooth-colored mineral trioxide aggregate (MTA) when mixed with sterile water or 2% chlorhexidine. Second, to compare the compressive strengths of the MTA/chlorhexidine versus MTA/sterile water samples. The antimicrobial effect test was accomplished by placing freshly mixed MTA samples on agar plates inoculated with Enterococcus faecalis and comparing the zones of inhibition at 24 hours. In the compressive strength test, MTA pellets were allowed to set for 72 hours and then compressed to fracture by using an Instron testing machine. Values were recorded and compared. In the antimicrobial effect experiment, the zones of inhibition were significantly larger for samples mixed with 2% chlorhexidine. In the compressive strength study, statistical evaluation showed no significance due to variability. However, data revealed that MTA mixed with sterile water always had higher compressive strengths than MTA mixed with chlorhexidine.