1,720,995 research outputs found
Long-term outcome of non-surgical root canal treatment: a retrospective analysis
No full textThis study investigated the long-term clinical outcome of root canal treatment. 240 root-treated teeth (n = 61 patients) were initially classified on the basis of radiographic presence/absence of initial apical periodontitis (IAP) and clinical data. The final outcome measure was the periapical healing (healed/disease). The outcome at 6-9 months was correlated with the outcome at 10 years following treatment. Prognostic factors for the periapical healing were assessed. Extraction data were recorded. Univariate and multivariate logistic regression analysis was used to identify risk indicators for apical periodontitis (AP) development. Chi-square analysis was performed to evaluate a possible relationship between the 6-9 months outcome and the final outcome related to IAP. Mean observation time was 14 ± 3.7 years. Survival rate was 84.6% and healing rate was 79% (10-19 years). Predictors of outcome (p < .05) were considered statistically significant. Multivariate logistic regression analysis showed that initial pulpal and periapical status and the quality of root canal filling as assessed two-dimensionally were independent predictors of outcome. The 6-9 months evaluation appears to be an indicator for the final outcome of primary root canal treatment both in the presence and in the absence of IAP. An initial radiolucency associated with an unsatisfactory quality and extent of root canal filling significantly diminishes the possibility of achieving long-term radiographic success. For those with uncertain healing at 6-9 months (91%), clinicians should consider the high healing rate when estimating the prognosis and adjust the decision making accordingly
Evaluation of the root filling quality with experimental carrier‐based obturators: a CLSM and FEG‐SEM analysis
Full text linkThis study evaluated tubule penetration of GuttaFlow Bioseal with cold single cone or carrier-based technique, under confocal laser scanning microscopy (CLSM). Twenty straight single-rooted teeth were instrumented with Hyflex CM and divided in two groups (n = 10) according to the obturation method: single cold gutta-percha cones; experimental carrier-based obturators. GuttaFlow Bioseal, labelled with Rhodamine B dye, was used as sealer in both groups. Teeth transversally sectioned were observed under CLSM. Percentage of sealer penetration and integrity of sealer layer perimeter were measured. Surface and microstructural characteristics of obturators and gutta-percha cones were compared by FEG-SEM and EDX analysis. No significant differences were found between groups for each examined parameter. Significant differences (P < 0.05) were reported mainly within groups. Integrity was similar among and within groups. FEG-SEM/EDX analysis of obturators revealed the presence of Ba and Zn. Carrier-based obturation technique associated with GuttaFlow Bioseal does not seem to affect sealer penetration into dentinal tubules
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Metallurgical analysis and fatigue resistance of WaveOne and ProTaper Nickel–Titanium instruments
No full textThe aim of the study was to evaluate cyclic
fatigue resistance of two NiTi instruments and to analyse
their surface, fractographic and matrix morphology under
ESEM/EDS and optical microscopy. WaveOne Primary and
ProTaper Universal F2 brand new instruments were subjected
to fatigue testing in an artificial canal with 5.0 mm
radius and 60 angle of curvature. Seventy-two instruments
were divided into three groups (n = 24), according to the
selected kinematics: WaveOne using reciprocation (A);
ProTaper using reciprocation (B) or rotation (C). Time to
fracture was recorded. Data were analysed with ANOVA
and Tukey test. ESEM/EDS analysis was conducted on new
files to examine surface characteristics and on fractured
fragments to identify the fractographic features. Metallographic
analysis was performed with optical microscope on
new instruments to evaluate alloy properties. Significant
differences were found with Group A, which was statistically
more resistant to cyclic fatigue (P\0.05) than the
other groups. Surface analysis of new instruments showed
both in WaveOne and ProTaper files the presence of deep
milling marks. ESEM fractographic analysis of WaveOne
showed multiple crack origins with an area of fatigue
propagation wider than ProTaper instruments, in which a
single crack origin could be detected. EDS analysis confirmed
the equiatomic NiTi composition. Metallographic
analysis under optical microscope revealed in WaveOne
instruments the presence of nano-crystalline martensitic
grains embedded in austenite matrix, presence which could
not be found in ProTaper files. WaveOne NiTi files revealed
higher resistance to fatigue stress, suggesting extended
working time in clinical applications
HyFlex EDM: innovative electro discharge machined rotary instruments. Fatigue testing, superficial and microstructural characterization
No full textAim To test the fatigue resistance and to evaluate the surface and microstructural alterations of new and in vitro used HyFlex EDM NiTi rotary prototypes.
Methodology Thirty electro discharge machined HyFlex EDM (Colt ene/Whaledent, Switzerland) prototypes, and 20 HyFlex CM (Colt ene/Whaledent, Switzerland) files were subjected to cyclic fatigue test in a standardized 70° artificial metal canal. Results were validated using Mann-Whitney tests (a-level 0.05). Fractographic analysis on broken samples was conducted using environmental scanning electron microscopy (ESEM) imaging. Fifteen new HyFlex EDM prototypes were used for in vitro instrumenta- tion of severely curved root canals of extracted multi-rooted teeth. Surface and microstructural characteristics of files were analyzed by ESEM equipped with energy dispersive x-ray spectrophotometry (EDS) and optical metallographic imaging. The same analysis was conducted on new and used instruments to assess the usage- induced degradation.
Results The cyclic fatigue test revealed an increase of fatigue resistance up to 700% of EDM files compared to CM (P = 0.0001). Fractographic analysis of fatigued EDM instruments disclosed multiple crack origins in correspondence of the cutting edges, with a limited fatigue striation zone and a noteworthy dimpled area. Surface and microstructural characterization of new instruments revealed the typical features of a NiTi ED-Machined alloy with a ‘crater-like’ surface. No fractures were registered during instrumentation of curved canals. Surface and microstructural characterization of used files revealed no wear and no degradation of the size 25, .12 taper and size 25, .08 taper files. The tip segment was confirmed as the most mechanically stressed portion of size 10, .05 taper files. The metallographic inspection on the cross section of brand new HyFlex EDM files showed an homoge- neous martensitic phase. The microstructure appeared uniform from the surface to the bulk, and no microcracks or defect were identified, even at high optical magnification (1000X). Conclusions HyFlex EDM exhibited high values of cyclic fatigue resistance and a safe in vitro use in severely curved canals. Unaltered spark-machined surface and low microstructural degradation are the main features of HyFlex EDM.
Acknowledgements The authors deny any conflict of interest related to this study and would thank Coltene Whaledent for providing the test material
Rehabilitation of anterior upper incisor area with combined therapy Maryland Bridge and Prama Implant: two case reports three
No full textBackground: New implant system with an innovative trasmucosal surface profile morphology (BOPT) have been recently developed.
The transmucosal neck surface is characterized by a controlled passivation treatment and a conical morphology to allow a
biological corrected prosthetic form of ceramic crown.
Aim/Hypothesis: The aim of this clinical cases study was to evaluate the marginal crestal bone loss (MBL) and gingival/periodontal
status of transmucosal implant placed in anterior upper area.
Material and methods: Three healthy subjects with acute active periapical lesion of seriously compromised upper incisor requiring
tooth extraction were consecutively included in the study. After tooth extraction, all patients were rehabilitated with the positioning
of a Maryland bridge to preserve the aesthetic line. Approximately 3 months later a transmucosal zirconium blasted acidetched
titanium (ZirTi) implant (PRAMA, Sweden & Martina, ITALY) was positioned with flapless technique. All implants had
insertion torque of 50–65 N/cm. Each implant was finally loaded after 3 months with a provisional resin crown and a di-silicate
ceramic crown as definitive restoration. Clinical and radiographic follow-up (mucosal profile, periodontal indices and MBL) was
performed 1, 2, 3 months after implant placement and 3 and 6 months after loading.
Results: No gingivitis and other complications were observed. No marginal bone loss was observed around the implants before
and after loading. Adequate and corrected aesthetic crown profile was obtained with a reduced compression of mucosal marginal
tissues.
Conclusions and clinical implications: The combined prosthetic and surgery technique and the use of ZirTi implant system with
BOPT profile showed valid aesthetic and biological profile and allow the placement of the ceramic crown with a corrected emergency
profile that may prevent MBL
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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