Advanced MaterialsVolume 23, Issue 8 p. 975-980 Communication Intrafibrillar Collagen Mineralization Produced by Biomimetic Hierarchical Nanoapatite Assembly Yan Liu, Yan Liu Department of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, ChinaSearch for more papers by this authorNan Li, Nan Li College of Osteopedics & Traumatology, Fujian University of Traditional Chinese Medicine, Fujian, ChinaSearch for more papers by this authorYi-pin Qi, Yi-pin Qi Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, ChinaSearch for more papers by this authorLin Dai, Lin Dai Department of Stomatology, The First Hospital of Wuhan, Wuhan, ChinaSearch for more papers by this authorThomas E. Bryan, Thomas E. Bryan Departments of Oral Biology and Endodontics, School of Dentistry, Medical College of Georgia, Augusta, Georgia, USASearch for more papers by this authorJing Mao, Jing Mao Department of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, ChinaSearch for more papers by this authorDavid H. Pashley, David H. Pashley Departments of Oral Biology and Endodontics, School of Dentistry, Medical College of Georgia, Augusta, Georgia, USASearch for more papers by this authorFranklin R. Tay, Corresponding Author Franklin R. Tay [email protected] Departments of Oral Biology and Endodontics, School of Dentistry, Medical College of Georgia, Augusta, Georgia, USADepartment of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.Search for more papers by this author Yan Liu, Yan Liu Department of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, ChinaSearch for more papers by this authorNan Li, Nan Li College of Osteopedics & Traumatology, Fujian University of Traditional Chinese Medicine, Fujian, ChinaSearch for more papers by this authorYi-pin Qi, Yi-pin Qi Department of Operative Dentistry and Endodontics, Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, ChinaSearch for more papers by this authorLin Dai, Lin Dai Department of Stomatology, The First Hospital of Wuhan, Wuhan, ChinaSearch for more papers by this authorThomas E. Bryan, Thomas E. Bryan Departments of Oral Biology and Endodontics, School of Dentistry, Medical College of Georgia, Augusta, Georgia, USASearch for more papers by this authorJing Mao, Jing Mao Department of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, ChinaSearch for more papers by this authorDavid H. Pashley, David H. Pashley Departments of Oral Biology and Endodontics, School of Dentistry, Medical College of Georgia, Augusta, Georgia, USASearch for more papers by this authorFranklin R. Tay, Corresponding Author Franklin R. Tay [email protected] Departments of Oral Biology and Endodontics, School of Dentistry, Medical College of Georgia, Augusta, Georgia, USADepartment of Stomatology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.Search for more papers by this author First published: 15 December 2010 https://doi.org/10.1002/adma.201003882Citations: 136Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Phosphorous-based templating analogs of extracellular matrix proteins are used as templates in conjunction with polycarboxylic acid-stabilized amorphous calcium phosphate nanoprecursors to create a highly ordered intrafibrillar apatite crystallite assembly within a collagen fibril. The assembly recapitulates the gap and overlap arrangement of collagen molecules. Citing Literature Supporting Information Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Filename Description adma_201003882_sm_suppl.pdf17.5 MB suppl Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume23, Issue8February 22, 2011Pages 975-980 RelatedInformation

Introduction: This study investigated the setting time and micohardness of a premixed calcium phosphate silicate based sealer (EndoSequence BC Sealer; Brasseler USA, Savannah, GA) in the presence of different moisture contents (0-9 wt%). The moisture content that produced the most optimal setting properties was used to prepare set EndoSequence BC Sealer for cytotoxicity comparison with an epoxy resin based sealer (AH Plus; Dentsply Caulk, Milford, DE). Methods: Standardized disks were created with BC Sealer, AH Plus, Pulp Canal Sealer EWT (positive control) (SybronEndo, Orange CA), and Teflon (Small Parts Inc., Miami Lakes, FL; negative control). Disks were placed in Transwell Inserts, providing indirect contact with MC3T3-E1 cells. Succinate dehydrogenase activity of the cells was evaluated over a 6-week period using MTT ((3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Cytotoxicity profiles of BC Sealer and AH Plus were fitted with polynomial regression models. The time for 50% of the cells to survive (T-0.5) was analyzed using the Wald statistic with a two-tailed significance level of 0.05. Results: BC Sealer required at least 168 hours to reach the final setting using the Gilmore needle method, and its microhardeness significantly declined when water was included in the sealer (P = .004). All set sealers exhibited severe cytotoxicity at 24 hours. The cytotoxicity of AH Plus gradually decreased and became non-cytotoxic, whereas BC Sealer remained moderately cytotoxic over the 6-week period. A significant difference (P < .001) was detected between T-0.5 of BC Sealer (5.10 weeks; 95% confidence interval [CI], 4.69-5.42, standard error [SE] = 0.09) and T-0.5 of AK Plus (0.86 weeks; 95% CI, 0.68-1.05; SE = 0.18). Conclusions: Further studies are require I to evaluate the correlation between the length of setting time of BC Sealer and its degree of cytotoxicity. (J Endod 2011;37:673-677)

The in vitro cytotoxicity of five endodontic sealers was measured >8-12 weeks using L929 mouse fibroblasts, osteoblastic cells (ROS) 17/2.8 rat osteoblasts, and MC3T3-E1 mouse osteoblasts. Discs (n = 6) of AH-plus Jet (AHP), two versions of Endo Rez (ER, ERx), Epiphany (EPH), and Pulp Canal Sealer (PCS) were prepared. The sealers and Teflon (Tf, negative control) were placed in direct contact with cells after immersion in phosphate-buffered saline for 1-12 wk. Cellular succinate dehydrogenase (SDH) activity was estimated using the MTT method (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a yellow tetrazole), and activities were normalized to Teflon® controls. The cellular responses to the materials were compared using analysis of variance with Tukey posthoc analyses (α = 0.05). Initially, all sealers suppressed normalized SDH activity of L929 fibroblasts by >90%. After 12 weeks of immersion in saline, AHP exhibited the SDH activity above Tf (120%), followed by ERx (78%), ER (58%), PCS (38%), and EPH (28%), all statistically distinct (p < 0.05). In general, the three cell lines responded similarly to the sealers. However, AHP caused unique responses: ROS cells were significantly (p < 0.05) less sensitive initially, and AHP was severely cytotoxic to MC3T3 cells (<35% of Tf) through 8 weeks. The data suggest that with "aging" in saline, current endodontic sealers decrease in in vitro cytotoxicity at different rates.

AIM To compare canal and isthmus debris debridement efficacies of the manual dynamic irrigation (MDI) and apical negative pressure (ANP) techniques in the mesial root of mandibular first molars with narrow isthmi, using a closed canal design. METHODOLOGY Micro-computed tomography was employed to select 20 teeth, each containing a narrow isthmus. Each root was sealed at the apex with hot glue and embedded in polyvinylsiloxane to simulate a closed canal system. The teeth were submitted to a standardized instrumentation protocol. Final irrigation was performed with either the MDI or the ANP technique using the EndoVac system (N=10). Masson trichrome-stained sections were prepared from completely demineralized roots at 10 canal levels between 1 and 2.8mm of the anatomical apices. Areas occupied by canals and isthmus of each root and debris in the corresponding regions were digitized by the NIH Image J software and statistically analysed using two-way repeated measures anova. RESULTS For the instrumented canals, there were no differences between the two groups (P=0.131) in the area occupied by debris at all canal levels (P=0.343). Conversely, for the isthmus, less debris was found in the ANP group (P<0.001) but no differences were seen in each group with respect to the 10 canal levels (P=0.352). CONCLUSION Neither technique completely removed debris from the isthmus regions. However, the EndoVac system, which encompasses the ANP concept, removed considerably more debris from narrow isthmi in mandibular mesial roots.

Objective: This in vitro study compared the cytotoxicity and osteogenic potential of an experimental calcium silicate based sealer with an epoxy resin based sealer (AH Plus; Dentsply Caulk, Milford, DE) and a zinc oxide eugenol based sealer (Pulp Canal Sealer; SybronEndo, Orange, CA). Methods: Disks prepared from the respective sealer and from Teflon (negative control) were placed in direct contact with a MC3T3-E1 osteogenic cell line at 6 weekly intervals after immersion in a culture medium. Succinic dehydrogenase activities were evaluated using 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Extracts from these sealers after the 6-week immersion period were investigated also by MTT assay. Aged sealers were then switched to an osteogenic medium for examination of the alkaline phosphatase activity and mineralization of extracellular matrices produced by the differentiated cells. Results: All sealers exhibited severe toxicity after 24 hours, after which toxicity decreased gradually over the experimental period except for Pulp Canal Sealer, which remained severely toxic. Toxicity of the extracts derived from the sealers was concentration dependent, with those derived from the experimental sealer being the least cytotoxic at a 1:10 dilution. Minimal alkaline phosphatase activity and no bone formation were seen with Pulp Canal Sealer. The production of alkaline phosphatase was less intense for the experimental sealer at 7 days. However, both AH Plus and the experimental sealer did not inhibit mineralization of the extracellular matrix after 28 days. Conclusion: The experimental calcium silicate based sealer may be regarded as minimally tissue irritating and does not interfere with bone regeneration even when it is inadvertently extruded through the apical constriction. (J Endod 2010;36:1163-1169)

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. (J Endod 2010;36:105-109)

The complex morphologies of mineralised collagen fibrils are regulated through interactions between the collagen matrix and non-collagenous extracellular proteins. In the present study, polyvinylphosphonic acid, a biomimetic analogue of matrix phosphoproteins, was synthesised and confirmed with FTIR and NMR. Biomimetic mineralisation of reconstituted collagen fibrils devoid of natural non-collagenous proteins was demonstrated with TEM using a Portland cement-containing resin composite and a phosphate-containing fluid in the presence of polyacrylic acid as sequestration, and polyvinylphosphonic acid as templating matrix protein analogues. In the presence of these dual biomimetic analogues in the mineralisation medium, intrafibrillar and extrafibrillar mineralisation via bottom-up nanoparticle assembly based on the non-classical crystallisation pathway could be identified. Conversely, only large mineral spheres with no preferred association with collagen fibrils were observed in the absence of biomimetic analogues in the medium. Mineral phases were evident within the collagen fibrils as early as 4 h after the initially-formed amorphous calcium phosphate nanoprecursors were transformed into apatite nanocrystals. Selected area electron diffraction patterns of highly mineralised collagen fibrils were nearly identical to those of natural bone, with apatite crystallites preferentially aligned along the collagen fibril axes.

The latest generation of methacrylate resin–based sealers has eliminated the use of separate self-etching primers by incorporating acidic resin monomers in the sealers to render them self-adhesive to dentin. This study examined the adhesive strengths, interfacial ultrastructure, and tracer penetration of a nonetching (EndoREZ; Ultradent, South Jordan, UT) and two self-adhesive methacrylate resin–based sealers (MetaSEAL; Parkell, Farmington, NY, and RealSeal SE; SybronEndo, Orange, CA) when they were applied to radicular dentin following the manufacturers' recommended use of EDTA as the active final rinse. A modified push-out testing design was used to evaluate the dislodgement of core-free sealers. The mixed sealers were placed in dimensionally identical, artificially created canal spaces prepared in the coronal, middle, and apical thirds of radicular dentin. After setting, each sealer-filled cavity was subjected to compressive loading until failure. Additional specimens were prepared for transmission electron microscopy to examine the ultrastructure and nanoleakage within the sealer-radicular dentin interface. The two self-adhesive sealers MetaSEAL and RealSeal SE exhibited higher push-out strengths than the nonetching sealer EndoREZ when EDTA was used as the active final rinse. All three sealers showed a 1- to 1.5-μm thick zone of partially demineralized dentin, with the EDTA dentin demineralization effect masking the true self-etching potential of MetaSEAL and RealSeal SE. The true self-etching potential of self-adhesive sealers is a clinically important attribute that should be further investigated. Incomplete smear layer removal from the apical third of instrumented canal walls may jeopardize the performance of self-adhesive sealers should they fail to self-etch without the adjunctive use of calcium chelating irrigants.

The cytotoxicity of four methacrylate resin–based sealers was investigated by the 3-(4,5-dimethyl-thiazoyl)-2,5-diphenyl-tetrazolium bromide assay, which measures cell viability by assessing its succinate dehydrogenase activity. The sealers were polymerized in the self-cured mode to simulate the setting condition upon their extrusion into periradicular tissues. Disks were prepared from EndoREZ (Ultradent, South Jordan, UT), RealSeal (SybronEndo, Orange, CA), MetaSEAL (Parkell, Farmington, NY), and RealSeal SE (SybronEndo) together with positive and negative controls. After setting, they were placed in direct contact with rat osteosarcoma (ROS 17/2.8) cells and for 5 succeeding weeks after immersing in simulated body fluid (SBF). All sealers exhibited severe toxicity initially (week 0). EndoREZ and RealSeal remained severely toxic after five cycles of SBF immersion. Toxicity of the two self-etching resin-based sealers MetaSEAL and RealSeal SE decreased gradually over time. Transmission electron microscopy of cells exposed to RealSeal SE showed variable degrees of cell injury that reflect its toxicity status. Cells with intact mitochondria were identifiable after the sealer became noncytotoxic at week 5.