Quality of root canal fillings using three gutta-percha obturation techniques

published_or_final_versio

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Root Canal Instrumentation - Influence of File Design

Theme: Emerging Trends for Endodontic Excellenc

The effect of elastic modulus of posts on coronal restorations

Session - Endondontics Bonding and LeakageObjectives: Root canal posts with modulus of elasticity similar to dentine have been advocated to restore severely broken-down anterior teeth. It is unknown if the inherent flexibility of these posts could affect the maintenance of marginal integrity of the final restoration under mastigatory loads. The objective of this study was to examine the leakage pattern of full-coverage restorations retained with either metallic or fiber-reinforced resin post after simulated occlusal loading. Methods: 36 maxillary central incisors were root canal-treated, and restored with a post-and-core supported crown with 1.5mm ferrule. The experimental group (n=12) was restored with fiber-post (EasyPost Lux), while the comparison group (n=12) was with metallic post (ParaPost); both were subjected to 120,000 cyclic loads up to 70N whilst being immersed in 2% Basic Fuschin. One control group (n = 12, similarly restored with fiber-post) was immersed but not loaded. Transverse serial cross-sections were cut at 1mm intervals from the tooth-core interface towards the apex. Hi-resolution digital photographs were taken for examining the leakage on the buccal, mesial, palatal and distal aspects along the depth of the post. Leakage was scored on a 5-point measuring scale: 0 – no leakage; Dye penetration 1 – luting cement interface; 2 – into superficial half of dentine; 3 – into the inner half of dentine; 4 – into the post space. Results: There was significant difference in the amount of leakage between the two experimental groups with the fiber-post group showing greater amounts of leakage than the control and the ParaPost group (ANOVA, Holm-Sidak pair-wise multiple comparison P < 0.05). Conclusion: Within the limitations of this study, the marginal integrity of the coronal restoration was affected by the modulus of elasticity of the post during repeated stresses. The use of fiber posts in teeth with minimal coronal tooth structure may require further evaluation.The 88th General Session & Exhibition of the International Association of Dental Research (IADR), Barcelona, Spain, 14-17 July 2010. In Journal of Dental Research, 2010, v. 89, Spec. Iss B, abstract no. 397

Electropolishing enhances the resistance of nickel-titanium rotary files to corrosion-fatigue failure in hypochlorite

Introduction: The aim of this study was to examine the fatigue behavior, especially at the low-cycle fatigue (LCF) region, of an experimentally electropolished FlexMaster and a commercial electropolished nickel-titanium (NiTi) instrument (RaCe) in a corrosive environment. Methods: A total of 90 NiTi rotary instruments were subjected to rotational bending at various degrees of curvatures while immersed in 1.2% sodium hypochlorite solution until broken. The maximum surface strain amplitude, calculated from the curvature of the instrument and the diameter of the cross section at break, was plotted against the LCF life. The results were compared with data for a non-electropolished commercial product tested by using the same methodology. Results: The fatigue life of both instruments generally declined with increasing surface strain amplitude; there was a significant difference between the 2 instruments. Comparing the surface-treated FlexMaster with its commercially available non-electropolished counterpart, an improved resistance to fatigue breakage as a result of electropolishing was noted (P < .05). Conclusions: The LCF life of a NiTi instrument rotating with a curvature in a corrosive environment is enhanced by electropolishing. The design, both cross-sectional and longitudinal, appears to have an effect on the fatigue behavior of NiTi rotary instruments. © 2010 American Association of Endodontists.link_to_subscribed_fulltex

Effect Of Root Canal Dimensions, Injection Rate, And Needle Design On The Apical Extrusion Of An Irrigant: An In Vitro Study

Aim: The purpose of this study was to determine the effect of root canal dimensions, type of needle, and injection rate on the apical extrusion of an irrigant in a simulated root canal. Methods: Ten students used two types of 28-gauge needles, to deliver 3 mL irrigant solution into artificial canals prepared in acrylic blocks to a standard size of ISO 25, 30, or 40 (0.06 taper; n = 10). Each block was preweighed to the nearest microgram before and after irrigation once the canal was dried with paper points. This was repeated with a syringe pump at a flow rate of 50, 100, 200 or 300 lL/s with the needle inserted to a standard depth. Results: Significant differences were observed between the side-vented and notched-end needles when the rate of irrigation was higher than 100 lL/s, and when the apical size was below ISO 40 (P < 0.001). The amount of extrusion was more variable and significantly higher when irrigation was performed manually, compared with the syringe pump groups. Conclusions: Injection rates above 100 lL/s increased the risk of extrusion, whereas increasing the apical canal size to ISO 40 reduced the amount of extrusion in all groups. The use of a side-vented needle negates the injectionrate effects

Qualitative research in dental education: an application of stimulated recall in focus groups

Oral Communication Session 1: no. O1-005Best Oral PresentationINTRODUCTION & OBJECTIVES: Qualitative methods are increasingly being adopted in dental education research and evaluation. In particular, focus group interviews are seen to support deeper insights into both student and Faculty perceptions of learning, particularly with regard to curriculum innovations. In this study, stimulated recall methods were applied in student focus group interviews to (a) evaluate a new project’s effectiveness and (b) investigate how the implementation of a blended learning innovation combining face-to-face instruction with an international online learning experience enhanced student learning outcomes. METHOD: Consenting students (n=17) formed two focus groups at project completion in 2009-10 and 2010-11 respectively. Both focus groups (a) responded to semi-structured questions posed by evaluating staff, including a project clinical tutor, and (b) commented on visual stimuli via an interactive whiteboard (IWB). Stimuli used as recall prompts included participants’ digital assignments and online peer forum exchanges. Interviews were transcribed, verified and thematically coded. RESULTS: Stimulated student reflections provided (a) project feedback to improve assignment and forum design; and (b) evidence of deep learning, particularly in the domains of academic/professional excellence, greater understanding of others, and collaboration. CONCLUSION: Stimulated recall methods supported project evaluation and understandings of student learning in a blended environment.The 22nd Annual Scientific Meeting of the South East Asian Association for Dental Education (SEAADE), Singapore, 29-30 October 2011

Micro-push-out bond strengths of an adhesively luted fiber-post subjected to simulated occlusal loads

The 23rd Annual Scientific Meeting of the Faculty of Dentistry, The University of Hong Kong, Hong Kong, 13-15 November 2009