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.

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.

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.