Electrochemical Properties of Nickel-Titanium Rotary Endodontic Instruments.

INTRODUCTION: Nickel-titanium rotary endodontic files have been commercially available for decades, but more recent innovations have introduced heat-treated and surface-treated files. This study investigated the corrosion properties of various nickel-titanium files in normal saline and sodium hypochlorite (NaOCl). METHODS: Ten different file brands of size 40 with a 0.04 taper were subjected to electrochemical testing in 0.9% NaCl (saline) and 5.25% NaOCl at room temperature. The Open Circuit Potential (OCP) was observed for 1 hour followed by a cyclic polarization test from -300 to 700 mV and back to -300 mV (vs OCP). Nonparametric ANOVA and a pairwise comparison (P < .05) were used for statistical analysis of the OCP at 1 hour and the corrosion current (Icorr) obtained via the cyclic polarization test. RESULTS: Significant differences (P < .05) were found between files with respect to OCP and Icorr in both solutions. Nine files exhibited significantly greater (P < .05) Icorrs in NaOCl than in saline. Conversely, pitting corrosion was observed in the saline solution but not NaOCl. Weak and/or moderate correlations existed between OCP and Icorr measures in the 2 solutions. CONCLUSION: Significant differences in electrochemical properties were observed among the 10 brands of files. Overall, there was not a clear trend between conventional, heat-treated, or surface-treated files among OCP or Icorr in either solution.

Effectiveness of different cleaning measures on the bonding of resin cement to saliva-contaminated or blood-contaminated zirconia.

OBJECTIVE: To investigate the effectiveness of different cleaning measures on the bonding of resin cement to saliva- or blood-contaminated zirconia. METHODS: One hundred and forty-one specimens (10 × 10 × 1.5 mm3) were fabricated from KATANATM zirconia blocks and contaminated with human saliva or sheep blood. Six cleaning measures were examined: water-rinse, H3PO4, 5.25% NaOCl, ZirCleanTM, Ivoclean and KATANATM Cleaner. Tensile bond strength was evaluated for 13 groups (N=10): six cleaning measures against two contaminations (12 experimental groups) and one uncontaminated control group. Scanning electron microscopy was used to observe the control and water-rinsed specimen surfaces. X-ray photoelectron spectroscopy (XPS) was conducted to identify carbon (C1s), nitrogen (N1s), phosphorous (P2p) and zirconium (Zr3d) peaks, from which the elemental ratios C/Zr, N/Zr and P/Zr were calculated. RESULTS: Although water-rinsing removed most of the contaminants from the zirconia surface, bond strength of resin cement was significantly lower compared with the control. Phosphoric acid was ineffective and NaOCl was less reliable in restoring bond strength. The three commercial cleaners (ZirCleanTM, Ivoclean, KATANATM Cleaner) out-performed the other cleaning measures and restored the bond strength of resin cement to zirconia except for the use of ZircleanTM on blood-contaminated surfaces. N/Zr decreased for all cleaned specimens and P/Zr ratio increased for phosphoric acid and KATANATM Cleaner groups. Differences in elemental ratios could indicate different cleaning mechanisms for the zirconia cleaners. CONCLUSION: All three commercial zirconia cleaners are effective in decontaminating saliva-contaminated or blood-contaminated zirconia and increasing the bond strength of resin cement to contaminated zirconia. CLINICAL SIGNIFICANCE: The use of water, phosphoric acid or concentrated sodium hypochorite for cleaning saliva- or blood-contaminated dental zirconia is not recommended. ZirCleanTM works well on decontamination of saliva-contaminated zirconia. Ivoclean or KATANATM Cleaner are useful for decontamination of both saliva- and blood-contaminated zirconia during the intraoral try-in stage to recover the original bond strength of cementation.

Association between the History of Traumatic Brain Injury and Rates of Dental Treatment, Endodontic Therapy, and Caries Risk: A Records-Based Study.

INTRODUCTION: Traumatic Brain Injury (TBI) is a prevalent health issue in the US and even more prevalent amongst members of the armed forces. The purpose of this project was to evaluate the association between history of TBI and rates of dental treatment performed, endodontic therapy, and high caries risk. METHODS: This was a retrospective medical and dental records study. The first 100 of a chosen dental hygienist's patients in 2016 who were seen for dental prophylaxis appointments were chosen as subjects. Armed Forces Health Longitudinal Technology Application (AHLTA) and Corporate Dental System (CDS) records were used to gather information on these subjects including rank, age, gender, duty status, tobacco use, history of TBI, total number of dental procedures, total Dental Weighted Value (DWV), number of endodontic procedures, endodontic DWV, high caries risk categorization, total days dental fitness class 1, and total days dental fitness class 3. From these subjects, a "TBI group" and a "Non-TBI group" were formed. T-Test analyses were performed to compare these groups to each other in categories of total number of dental procedures, total DWV, total days dental fitness class 1, and total days class 3. Relative risks ratio analysis was used to compare these groups in terms of high caries risk categorization. RESULTS: Eight out of 100 subjects had a history of TBI. All TBI events were mild. Six subjects had 1 event, 1 had 2 events, and 1 had 4 events. The TBI group had a statistically higher mean number of dental procedures (P=0.00000025) and mean total DWV (P=0.0000062) compared to the non-TBI group. No subjects from the TBI group had an endodontic procedure. The TBI group had lower mean days in dental fitness class 1 and more mean days in dental fitness class 3, but the results were not statistically significant. The TBI group had lower high caries risk categorization rates than the non-TBI group, but the results were not statistically significant. CONCLUSIONS: Patients with a history of TBI had a significantly higher number of dental procedures performed and DWV generated compared to patients without a history of TBI.

In vitro evaluation of efficacy of two endodontic sonic-powered irrigant agitation systems in killing single-species intracanal biofilms.

OBJECTIVE: To evaluate the efficacy of two sonic-powered irrigation systems, EDDY and EndoActivator, in killing intracanal biofilms. METHODS: Eighty-three instrumented, autoclaved single-rooted human premolars were inoculated with Enterococcus faecalis (ATCC-29212) for 21 days to generate mature, single-species biofilms. The teeth were devided into four groups: irrigation with saline (N = 11); irrigation with 2% NaOCl without agitation (N = 24); irrigation with 2% NaOCl with agitation by the EndoActivaor (N = 24); irrigation with 2% NaOCl with agitation by the EDDY (N = 24). Colony-forming unit (CFU) counts and XTT assay were used to evaluate bacterial load. Additional teeth were split into root-halves for fluorescence staining to examine the percentages of live/dead bacteria in the dentinal tubules present in different canal locations (coronal, mid-root and apical portions). RESULTS: Agitation of 2% NaOCl by EDDY or EndoActivator reduced bacteria load more proficiently than the use of 2%NaOCl without agitation (p < 0.05). No significant difference was detected between the two sonic-powered irrigant agitation systems (p > 0.05). Confocal laser scanning microscopy indicated that both devices had better intratubular bacteria killing efficacy than the use of 2% NaOCl only in all parts of the canal space (p < 0.05), with no significant difference detected between EDDY and EndoActivator (p > 0.05). Elimination of intracanal and intratubular bacteria were less efficient in the apical portion of the canal space for all experimental groups. CONCLUSION: The two sonic-powered irrigant activation systems demonstrated comparable intracanal bacteria reduction efficacy when 2% NaOCl was used for disinfecting E. faecalis biofilms in single-rooted teeth. CLINICAL SIGNIFICANCE: With the use of 2% NaOCl as irrigant, the EDDY and EndoActivator sonic-powered irrigant agitation systems have improved and equivalent intracanal bacteria reduction efficacy but are incapable of completely killing all bacteria that resided within the dentinal tubules of root canals.

Effects of pre-mixed hydraulic calcium silicate putties on osteogenic differentiation of human dental pulp stem cells in vitro.

OBJECTIVES: An experimental tricalcium silicate and dicalcium silicate-containing endodontic putty has been designed to overcome the issue of reduced shelf life after exposure to atmospheric moisture during repeated opening of the container for clinical retrieval. The present study examined the effects of this experimental hydraulic putty on the mineralogenic characteristics of osteogenic lineage-committed human dental pulp stem cells (hDPSCs), by comparing the cellular responses with a commercially available putty (EndoSequence BC RRM Putty). METHODS: The osteogenic potential of hDPSCs that had been exposed to the putties was examined using quantitative reverse-transcription polymerase chain reaction for osteogenic gene expressions and western blot for osteogenic protein expressions. Alkaline phosphatase activity assay and alizarin red S staining were performed to detect changes in production of the intracellular enzyme and extracellular matrix mineralization respectively. RESULTS: Osteogenic differentiation of the hDPSCs was significantly enhanced after exposure to the pre-mixed hydraulic putties, with no significant difference between these two examined putties. CONCLUSIONS: The experimental hydraulic tricalcium silicate putty enhances osteogenic differentiation of hDPSCs to the same extent as a commercially available tricalcium silicate putty. CLINICAL SIGNIFICANCE: The experimental hydraulic putty appears to be an alternative to the commercial putty when used for applications involving the regeneration of bone in endodontics. Animal models are required for validating its potential in enhancing osteogenesis in vivo.

Manoeuvrability and biocompatibility of endodontic tricalcium silicate-based putties.

OBJECTIVES: The present study evaluated the indentation depth, storage modulus and biocompatibility of an experimental endodontic putty designed for endodontic perforation repair and direct pulp-capping (NeoPutty). The results were compared with the properties associated with the commercially available EndoSequence BC RRM Putty (ES Putty). METHODS: Indentation depth was measured by a profilometer following indentation with the 1/4 lb Gilmore needle. Elastic modulus was evaluated using a strain-controlled rheometer. The effects of eluents derived from these two putties were examined on the viability and proliferation of human dental pulp stem cells (hDPSCs) and human periodontal ligament fibroblasts (hPDLFs), before (1 st testing cycle) and after complete setting (2nd testing cycle). RESULTS: The ES Putty became more difficult to ident and acquired a larger storage modulus after exposure to atmospheric moisture. Biocompatibility results indicated that both putties were relatively more cytotoxic than the bioinert Teflon negative control, but much less cytotoxic than the zinc oxide-eugenol cement negative control. NeoPutty was less cytotoxic than ES putty in the 1st testing cycle, particularly with hDPSCs. Both putties exhibited more favourable cytotoxicity profiles after complete setting. CONCLUSIONS: NeoPutty has a better window of maneuverability after exposure to atmospheric moisture. From an in vitro cytotoxicity perspective, the NeoPutty may be considered more biocompatible than ES putty. CLINICAL SIGNIFICANCE: The experimental NeoPutty is biocompatible and is capable of reducing the frustration of shortened shelf life when jar-stored endodontic putties are exposed to atmospheric moisture during repeated opening of the lid for clinical retrieval.

Heat Generation Changes with Electrically Heated Pluggers after Multiple Autoclave Cycles at Different Operating Temperatures.

INTRODUCTION: Electrically heated pluggers are the most commonly used instruments during warm obturation techniques. This study aimed to evaluate the effect of sterilization and operating temperature settings on the heat generation of pluggers of various taper sizes. METHODS: Fifty pluggers were sterilized at 132°C for 25 minutes for a total of 150 cycles. One group (Autoclave200) consisted of 25 pluggers tested at an operating temperature setting of 200°C, whereas another group (Autoclave400) consisted of 25 pluggers tested at 400°C. The heat generation at their tip surface was measured with T-type thermocouples at 0, 50, 100, and 150 autoclave cycles. An unpaired t test was used to compare the time it took the pluggers to reach 60°C and the mean maximum temperature change. RESULTS: After 50 autoclave cycles, all of the 0.04 taper pluggers in Autoclave200 failed to reach 60°C. After 100 autoclave cycles, one of the 0.10 taper pluggers in Autoclave200 did not reach 60°C, and after 150 autoclave cycles, one of the 0.04 taper pluggers failed to generate any heat. The mean increase in the time to reach 60°C ranged from 1071-4004 milliseconds and 510-2074 milliseconds for Autoclave200 and Autoclave400, respectively. The mean maximum temperature change decreased by 13-29°C and 24-116°C for Autoclave200 and Autoclave400, respectively. CONCLUSIONS: After multiple autoclave cycles and higher operating temperature use, the electrically heated pluggers transferred less heat to the tip surface, potentially making them less effective.

Comparison of the use of d-enantiomeric and l-enantiomeric antimicrobial peptides incorporated in a calcium-chelating irrigant against Enterococcus faecalis root canal wall biofilms.

OBJECTIVES: To compare the anti-biofilm efficacy of two antimicrobial peptides (AMPs), 1018 and DJK-5, in disrupting canal wall biofilms in the isthmus, canal and dentinal tubules of single-rooted maxillary premolars. METHODS: Enterococcus faecalis single-species biofilms were formed in-situ in the root canal system of the premolars (n = 91). Confocal laser scanning microscopy, bacterial sampling, colony-forming unit counting, XTT assay, lactate dehydrogenase assay and phenol-sulphuric acid method were used to identify the anti-biofilm efficacy of both AMPs and their influence on bacterial metabolic activity. RESULTS: Both AMPs disrupted in-situ E. faecalis biofilms and altered their metabolic activity. At 20 µg/mL, the d-enantiomeric AMP DJK-5 killed 55.5 %, 57.3 % and 55.8 % of biofilm bacteria in the isthmus, canal and dentinal tubules, respectively, in 1 min. In contrast, the l-enantiomeric AMP 1018 only eradicated 25.6 %, 25.5 % and 27.5 % of biofilm bacteria in the isthmus, canal and dentinal tubules, respectively, within the same time. Anti-biofilm efficacy of the root canal irrigants tested were in the order: 6 % NaOCl > 20 µg/mL DJK-5 > 10 µg/mL DJK-5 > 20 µg/mL 1018 > 10 µg/mL 1018 > 0.9 % NaCl. CONCLUSIONS: The present results are confirmatory of previous studies, in that d-enantiomeric AMPs exhibit more potent antibacterial properties than l-enantiomeric AMPs against E. faecalis biofilms within the canal space. Nevertheless, the potency of both AMPs are concentration-dependent. Incorporation of these agents into EDTA, a non-antibacterial calcium-chelating irrigant for removal of the inorganic component of the canal space debris, does not reduce the efficacy of either AMP. CLINICAL SIGNIFICANCE: The present study provides the proof of concept that incorporation of an antimicrobial peptide into a calcium-chelating root canal irrigant enhances the disinfection of intratubular single-species biofilms during smear layer and smear plug removal.

Effect of a Benzalkonium Chloride Surfactant-Sodium Hypochlorite Combination on Elimination of Enterococcus faecalis.

INTRODUCTION: The purpose of this investigation was to determine the effect of a sodium hypochlorite-surfactant combination on the removal of Enterococcus faecalis from infected teeth. METHODS: Sixty-four extracted human single canal anterior teeth were prepared with rotary instrumentation and sterilized. Teeth were divided into 4 groups, N = 16. Three experimental groups were inoculated with E. faecalis and cultured for 21 days before use: positive control group, no irrigation; NaOCl group, irrigated with 5 mL 6% NaOCl; and NaOCl/BAK group, irrigated with 5 mL 6% NaOCl/0.008% benzalkonium chloride (BAK). The negative control group received medium only and no inoculate. Paper point sampling of the canals was obtained before irrigation (S1) for all 4 groups and for 2 groups after irrigation (S2) to determine remaining colony-forming units. After sampling, all teeth were split in half and evaluated for bacterial viability colony-forming units and penetration of dentinal tubules by using fluorescent vital dye staining and confocal laser scanning microscopy. RESULTS: Comparison of pre-irrigation and post-irrigation paper point samples from the 2 irrigated groups showed a significant reduction in bacterial canal load (P < .001, Kruskal-Wallis), with a significantly lower load in the NaOCl/BAK group than in the NaOCl group (P = .001, Mann-Whitney U test); 68.8% of the NaOCl/BAK samples gave no recoverable counts. In contrast, no significant difference between these groups was found for counts recovered from dentin. Confocal laser scanning microscopy showed no differences in tubule penetration. CONCLUSIONS: The addition of BAK to NaOCl significantly reduced the number of remaining bacteria within the canal after irrigation compared with NaOCl alone.

The effectiveness of endodontic solvents to remove endodontic sealers.

Dental emergencies negatively affect troop readiness, especially during combat. Endodontic retreatment, when required, is especially challenging when the removal of endodontic sealer is required. In this study, we investigated the effectiveness of synthetic endodontic solvents to remove endodontic sealers. Fifty capillary tubes (2.7 mm ID×22 mm L), each filled to 15 mm with either Roth 801, AH Plus, MetaSEAL, or gutta-percha, were stored at 75% humidity for 14 days at 37°C. Ten capillary tubes containing each sealer were treated with either chloroform, xylene, EndoSolv R, EndoSolv E, or no solvent, and then penetrated with D3 ProTaper Universal Retreatment file on the same day. The time for the file to penetrate the length of each sealer was recorded, and the data statistically analyzed. Roth 801 failed to set and was not tested. The file took 3.4±0.1, 4.8±0.3, 5.7±0.4, 4.5±0.2, and 10.6±1.0 seconds (mean±SD) to penetrate gutta-percha using chloroform, xylene, EndoSolv R, EndoSolv E, or no solvent, respectively, and was performed by one endodontic resident at one sitting. The time for penetration of gutta-percha with any solvent was significantly faster (p≤0.05) than for AH Plus or MetaSEAL.The time for AH Plus ranged from 23.1±1.0 to 81.5±4.5 seconds. The time for MetaSEAL ranged from 97.2±6.1 to >180 seconds. EndoSolv E was the most effective solvent for AH Plus. It took significantly more time to remove MetaSEAL than AH Plus, regardless of the solvent used. Our study indicated that the use of the proper endodontic solvent makes complete removal of a sealer much more effective during retreatment.

Evaluation of a new filing system's ability to maintain canal morphology.

INTRODUCTION: The manufacturer of the Hyflex CM endodontic files claims the files remain centered within the canal, and if unwound during treatment, they will regain their original shape after sterilization. The purpose of this study was to evaluate and compare the canal centering ability of the Hyflex CM and the ProFile ISO filing systems after repeated uses in simulated canals, followed by autoclaving. METHODS: Sixty acrylic blocks with a canal curvature of 45° were stained with methylene blue, photographed, and divided into 2 groups, H (Hyflex CM) and P (ProFile ISO). The groups were further subdivided into 3 subgroups: H1, H2, H3; P1, P2, P3 (n = 10). Groups H1 and P1 were instrumented to 40 (.04) with the respective file system. Used files were autoclaved for 26 minutes at 126°C. After sterilization, the files were used to instrument groups H2 and P2. The same sterilization and instrumentation procedure was repeated for groups H3 and P3. Post-instrumentation digital images were taken and superimposed over the pre-instrumentation images. Changes in the location of the center of the canal at predetermined reference points were recorded and compared within subgroups and between filing systems. RESULTS: Statistical differences in intergroup and intragroup transportation measures were analyzed by using the Kruskal-Wallis analysis of variance of ranks with the Bonferroni post hoc test. There was a difference between Hyflex CM and ProFile ISO groups, although it was not statistically significant. Intragroup differences for both Hyflex CM and ProFile ISO groups were not significant (P < .05). CONCLUSIONS: The Hyflex CM and ProFile ISO files equally maintained the original canal's morphology after 2 sterilization cycles.

Regaining apical patency after obturation with gutta-percha and a sealer containing mineral trioxide aggregate.

INTRODUCTION: MTA Fillapex (Angelus Solucoes Odontologicas, Londrina PR, Brazil) was introduced as a mineral trioxide aggregate (MTA)-based sealer used for endodontic obturation. There is a lack of research that evaluates the ability of different solvents to soften MTA-based sealers during retreatment. This study tested the ability of 4 commonly used endodontic solvents to soften gutta-percha and MTA Fillapex to allow for the re-establishment of apical patency. METHODS: Eighty-six extracted maxillary anterior teeth were instrumented to the working length to a size 45 (.04 taper size). Teeth were divided into 2 groups (n = 43 for each group). MTA Fillapex was placed into all canals. Group 1 was obturated with gutta-percha to the working length, and group 2 was obturated 2 mm short of the working length to ensure the apical 2 mm was filled with sealer only. Both groups were divided into 4 subgroups (n = 10). The remaining teeth served as the control group. Each subgroup was exposed to 1 of the following solvents: chloroform, Endosolv R (Septodont, Saint-Maur, France), Endosolv E (Septodont), or eucalyptol. RESULTS: Patency was re-established in 100% of the teeth in groups 1 and 2 when tested with chloroform or Endosolv E, 80% of the teeth in group 1 and 90% in group 2 when tested with eucalyptol, and 10% of the teeth in group 1 and 50% in group 2 tested when with Endosolv R. The chi-square test indicated there was a statistical difference between Endosolv R and the other tested solvents for both groups. CONCLUSIONS: Chloroform, Endosolv E, and Eucalyptol soften GP and MTA Fillapex sufficiently to aid in re-establishing apical patency during endodontic retreatment.

Canal and isthmus debridement efficacy of the VPro EndoSafe negative-pressure irrigation technique.

INTRODUCTION: This study compared canal and isthmus debridement efficacies between side-vented needle irrigation (SNI) and the VPro EndoSafe (VPro) negative-pressure device (Vista Dental, Racine, WI) in mesial roots of mandibular first molars with narrow isthmuses in a closed-canal design. METHODS: Twenty teeth with narrow isthmuses were selected using micro-computed tomography scanning. Collagen solution was reconstituted with 1% NH(4)OH to simulate debris and injected into canals via vacuum. Canals were instrumented to size 40/.04. Final irrigation was performed with 17% EDTA and 6% NaOCl using SNI with a 30-G needle or the VPro system. Roots were demineralized, and Masson trichrome-stained sections were prepared at 1.2 to 3.2 mm from the anatomic apex for a total of 6 canal levels. Debris-filled areas within the canals and isthmuses were measured using ImageJ software (National Institutes of Health, Bethesda, MD) and statistically analyzed using repeated-measures analysis. RESULTS: There was no significant difference between techniques and debridement efficacy among the 6 levels within the canal (P = .108). The debridement efficacy at 1.6 mm differed significantly from that at 3.2 mm. VPro had significantly more debris at isthmus levels 2.0 and 2.4 mm than SNI (P = .009). A significant difference was observed between the canal and the isthmus (P < .001). Neither VPro nor SNI removed debris completely from the apical third or isthmus. CONCLUSIONS: VPro EndoSafe did not differ significantly from SNI in the overall debridement efficacy in the apical third of mesial roots of mandibular first molars.

Canal and isthmus debridement efficacy using a sonic irrigation technique in a closed-canal system.

INTRODUCTION: This in vitro study compared debridement efficacies of a sonic irrigation technique (Vibringe; Cavex Holland BV, Haarlem, The Netherlands) with side-vented needle irrigation (SNI) in the mesiobuccal root of maxillary first molars. METHODS: Twenty roots with narrow isthmuses (≤ 1/4 canal diameter) were selected using micro-computed tomography scanning. Collagen solution was injected into canals/isthmuses and reconstituted with NH(4)OH to simulate canal debris. Each root was sealed apically and embedded in polyvinyl siloxane simulating a closed-canal system. Canals were instrumented to size 40/.04 taper 1 mm short of the anatomic apex. The final irrigation was performed with the Vibringe or SNI. Roots were demineralized, sectioned at 6 levels (1.2-3.2 mm) from the anatomic apex, and stained using Masson trichrome stain. The areas occupied by canals and isthmus and the debris-containing areas were statistically analyzed with repeated-measures analyses using "irrigation technique" as the between factor and "canal level" as the within factor (α = 0.05). RESULTS: Canals had significantly more debris at 1.2 and 1.6 mm (P < .001), but there was no overall difference between the 2 techniques (P = .561). Significant differences were found between the Vibringe and SNI at 2.4, 2.8, and 3.2 mm (P < .05). There was no significant difference in the remaining debris in the isthmus for SNI at all (P > .05). Considerably more debris remained at 1.2 and 2.0 mm for the Vibringe (P < .05). A significant difference was observed between the canal and the isthmus (P < .001). CONCLUSIONS: There is no difference between the Vibringe and SNI in their overall debridement efficacy in apical one third of the mesiobuccal root of maxillary first molars.

Inhibition of endogenous dentin matrix metalloproteinases by ethylenediaminetetraacetic acid.

INTRODUCTION: Endogenous dentin matrix metalloproteinases (MMPs) contribute to extracellular collagen matrix degradation in hybrid layers after adhesive dentin bonding procedures. Endodontic irrigants, including chlorhexidine and ethylenediaminetetraacetic acid (EDTA), might help protect the hybrid layer from this process. The objective of the present study was to determine the exposure time necessary for EDTA to inactivate endogenous MMP activity in human dentin. METHODS: Dentin beams (2 × 1 × 3 mm) were prepared from mid-coronal dentin of extracted third molars. The beams were demineralized in 10 wt% phosphoric acid, which also activated endogenous MMPs, and were divided into 4 experimental groups on the basis of exposure time to 17% EDTA (0, 1, 2, or 5 minutes). A generic colorimetric MMP assay measured MMP activity via absorbance at 412 nm. Data were evaluated by Kruskal-Wallis analysis of variance, followed by Dunn pair-wise comparisons at α = 0.05. RESULTS: All exposure times resulted in significant inhibition (P < .001) compared with unexposed controls. Specifically, percent inhibition for 1-, 2-, and 5-minute exposure times was 55.1% ± 21.5%, 72.8% ± 11.7%, and 74.7% ± 19.7%, respectively. CONCLUSIONS: Seventeen percent EDTA significantly inhibits endogenous MMP activity of human dentin within 1-2 minutes. This might minimize hybrid layer degradation after resin bonding procedures in the root canal space.

An in vitro evaluation of the growth of human periodontal ligament fibroblasts after exposure to a 4-META-containing methacrylate-based endodontic sealer.

INTRODUCTION: In this study we evaluated the cytotoxic effects of MetaSEAL, a 4-META-containing meth-acrylate-based endodontic sealer, on human periodontal ligament (HPDL) fibroblasts. There are a limited number of studies on the cytotoxic effects of MetaSEAL, and there are no studies on the cytotoxic effects of MetaSEAL on cells it might come into contact with in vivo. METHODS: MetaSEAL concentrations of 25, 50, 100, 200, 400, and 800 µg/mL were exposed to HPDL fibroblast cultures and evaluated at 1, 3, 7, 14, and 21 days. Controls included untreated cells and cells treated with ethanol, the vehicle for MetaSEAL suspension. Crystal violet staining in 24-well plates and the fluorescence-based CyQUANT Cell Proliferation Assay in 96-well plates assessed fibroblast viability. RESULTS: Significant cytotoxicity against HPDL growth by MetaSEAL was both time- and concentration-dependent. At day 1 there were no significant cytotoxic effects, whereas by day 3, 800 µg/mL concentration, by day 7, 200, 400, and 800 µg/mL concentrations, and by day 14, 50, 100, 200, 400, and 800 µg/mL concentrations were significantly cytotoxic. By day 21, all concentrations were significantly cytotoxic. These findings were confirmed by both the crystal violet and CyQUANT assays. CONCLUSIONS: MetaSEAL endodontic sealer has increasing HPDL cytotoxicity with both concentration and time exposure.

Histologic evaluation of canal and isthmus debridement efficacies of two different irrigant delivery techniques in a closed system.

INTRODUCTION: This study compared canal and isthmus debridement efficacies between side-vented needle irrigation (SNI) and continuous ultrasonic irrigation (CUI) in the mesial root of mandibular first molars with narrow isthmuses using a closed-canal design. METHODS: Micro-computed tomography scanning was used to select 20 teeth, each containing a narrow isthmus. Each root was sealed at the apex; embedded in polyvinylsiloxane to simulate a closed-canal system; and instrumented to size 40, 0.04 taper. Final irrigation was performed with either SNI or CUI (N = 10). Masson trichrome-stained sections were prepared from demineralized roots at 10 canal levels between 1.0 and 2.8 mm from the anatomic apex. The areas and debris occupied by the canals and isthmus were measured using ImageJ software (National Institutes of Health, Bethesda, MD) and statistically analyzed using repeated-measures analysis. RESULTS: Overall, a significant difference was identified between SNI and CUI in the amount of debris remaining in the isthmus (P = .006) but not in the canal (P = .940). There was significantly more debris in the most apical three canal levels (1.0-1.4 mm) regardless of the irrigation technique (P < .001). The isthmus harbored significantly less debris in the CUI group between isthmus levels 1.0 to 2.2 mm when compared with SNI (P < .001 and P = .029). Neither technique removes debris completely from the canal or isthmuses. CONCLUSIONS: Compared with SNI, CUI removes significantly more debris from narrow isthmuses of mandibular mesial roots.

Effects of different exposure times and concentrations of sodium hypochlorite/ethylenediaminetetraacetic acid on the structural integrity of mineralized dentin.

INTRODUCTION: This study tested the null hypothesis that there is no difference between the use of 1.3% NaOCl/17% ethylenediaminetetraacetic acid (EDTA) and 5.25% NaOCl/17% EDTA irrigation regimens on the collagen degradation and flexural strength reduction in mineralized dentin. METHODS: Dentin powder and mineralized dentin sections were immersed in 1.3% or 5.25% NaOCl for 10-240 minutes and then rinsed with 17% EDTA as the final irrigant for 2 minutes. Untreated mineralized dentin powder/sections served as controls in the respective experiments. Dentin powders were examined by using Fourier transform infrared (FT-IR) spectroscopy to analyze their relative subsurface intact collagen content with the apatite/collagen ratio. Hydrated dentin sections were subjected to 3-point flexure under water for determining their flexural strengths. RESULTS: Collagen degradation was significantly increased and the flexural strength of mineralized dentin was significantly reduced after the use of 5.25% NaOCl as the initial irrigant for more than 1 hour (P < .05). Conversely, changes were insignificant when 1.3% NaOCl was used as the initial irrigant for up to 4 hours (Kruskal-Wallis analysis of variance, n = 10, P < .05). CONCLUSIONS: The null hypothesis was rejected. The deleterious effects attributed to the use of NaOCl on dentin are concentration-dependent and time-dependent and are not associated with the demineralization caused by the use of EDTA as the final active irrigant.

Radiographic interpretation of experimental lesions in radicular tooth structure of human maxillary anterior teeth.

External resorption is often first detected radiographically. Early detection can lead to timely intervention and improvement of treatment outcome. The purpose of this study was to determine the minimal radicular defect size in maxillary anterior teeth that is radiographically detectable. Six teeth were selected in a cadaver maxilla (#6-11) and extracted. The teeth were then replanted in the maxilla, and three horizontally angled radiographs (0 degrees , 30 degrees from the mesial, and 30 degrees from the distal) were exposed as a baseline. Then, a sequence of tooth removal, placement of a 0.1-mm deep defect in the interproximal and midroot surface, tooth replantation, and radiograph exposure was begun and repeated eight times. Each time the defect depth was increased by 0.1 mm. Ten clinicians interpreted the subsequent radiographs to determine if they visualized a defect on each tooth and the location of the defect. The evaluators' ability to detect experimental lesions according to the depth of the defect was shown to be statistically significant for both tooth type and location of the radicular defect (analysis of variance, p < 0.05). The average size of defect needed for radiographic visualization was as follows: central incisor (0.28 mm on the interproximal [IP] and 0.74 mm on the midroot [MR] [palatal], lateral incisor (0.39 mm on the IP and 0.55 mm on the MR); and canine [0.45 mm on the IP and 0.71 mm on the MR). Based on the results of this study, the minimal defect size detected was 0.28 mm to 0.74 mm depending on defect location and tooth selected.