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Analisi in vitro delle proprietà estetiche di un innovativo sistema a base di resine universali: valutazione delle proprietà ottiche, dell'integrazione cromatica e della stabilità del colore dei compositi single-shade
No full textLa scelta del colore di un restauro al fine di ottenere un’estetica ottimale rappresenta una delle maggiori sfide per i clinici in odontoiatria conservativa estetica.
Questa difficoltà è correlata alle specifiche proprietà ottiche dei tessuti duri dentali (smalto e dentina) ed all’interazione che questi hanno con i tessuti circostanti e con la luce. Le proprietà ottiche di smalto e dentina comprendono tinta, croma, valore, traslucenza, opalescenza, opacità.
Le resine composite tradizionali presentano diversi gradi di traslucenza e opacità (compositi smalti, body e dentine) e diverse tinte (A, B, C, D) e cromi (A1, A2, A3, A3.5, A4 ecc). Attualmente, lo stato dell'arte per riprodurre accuratamente l'aspetto di un dente naturale consiste nel selezionare e applicare più strati di masse composite multi-shade in spessori variabili, a seconda dell'area specifica del dente da restaurare.
Questa tecnica di stratificazione del composito permette di ottenere eccellenti risultati estetici ma richiede una certa esperienza clinica e lunghi tempi di realizzazione.
Per cercare di semplificare questo processo decisionale così complesso ed estremamente soggettivo, negli ultimi anni molte aziende hanno prodotto dei compositi cosiddetti universali, cioè resine che con poche masse di colore fossero capaci di includere tutti i colori necessari per riprodurre il dente naturale.
All’interno di questa innovativa categoria di compositi universali sono compresi anche le resine single-shade, ovvero quei materiali compositi dotati di elevata traslucenza e caratterizzati da una particolare tecnologia strutturale in grado, mediante una sola massa, di mimetizzarsi con il dente naturale circostante. L’effetto visivo che si ottiene è definito camaleontico.
Lo scopo principale della presente tesi di dottorato di ricerca è stato quello di valutare l’adattamento dei compositi single-shade al tessuto dentale circostante in termini di corrispondenza di colore e integrazione cromatica.
L’obiettivo secondario è stato quello di valutare il comportamento dei restauri eseguiti mediante compositi single-shade a seguito di sbiancamento professionale del dente restaurato, al fine di valutare se questi compositi fossero in grado di variare il proprio colore per uniformarsi ad un substrato circostante più chiaro.
Ulteriori obbiettivi sono stati quelli di valutare la stabilità cromatica di compositi multi- e single-shade a seguito di immersione in sostanze coloranti.
Sarà poi utile andare a studiare l’integrazione cromatica clinica di questa tipologia di compositi in restauri eseguiti in vivo ed il loro adattamento cromatico con folllow-up più lunghi nel tempo.The shade selection in restorative dentistry is one of the major challenges for clinicians when aiming to obtain restorations with optimal aesthetic results. This difficulty arises from the complex optical properties of enamel and dentin, and their interaction with surrounding tissues and light. The optical properties of dental hard tissues include hue, chroma, value, translucency, opalescence, and opacity.
Traditional composite resins are available in varying degrees of translucency and opacity (enamel, body, and dentin composites) and a range of shades (A, B, C, D) and chromas (A1, A2, A3, A3.5, A4, etc.). Nowadays, the state of the art for accurately reproducing the appearance of a natural tooth consists of selecting and applying multiple layers of these multi-shade different composite masses in varying thicknesses, depending on the specific area of the tooth being restored. While this layering technique can yield excellent aesthetic results, it requires considerable clinical expertise and is often time-consuming.
In recent years, to simplify this subjective process, most manufacturers have introduced so-called universal composites. These resins, with a limited number of shade masses, are designed to replicate all the necessary colors for a natural tooth.
Among this innovative family of universal composites are single-shade resins, which are characterized by high translucency and advanced structural technology. These materials allow a single shade to blend seamlessly with the surrounding natural tooth, creating a "chameleon" effect, also named blending effect.
The primary objective of this PhD thesis was to evaluate color matching and integration capabilities of single-shade composites in relation to surrounding dental tissues. A secondary goal was to assess the behavior of restorations made with single-shade composites following professional tooth bleaching, to determine whether these composites could adapt to match a newly altered substrate color. Additional objectives included the evaluation of color stability of single-shade composites after immersion in staining substances, compared to multi-shade resins.
As a future perspective, it will be valuable to assess the clinical color integration of these composites in restorations performed in vivo and to monitor their color adaptation over longer follow-up periods
Color Match of Single‐Shade Versus Multi‐Shade Resin Composites: A Systematic Review With Meta‐Analysis
Get PDFObjective: To address the following PICOS question: Can single-shade resin composites achieve a color match comparable to multi-shade composites in tooth restoration?
Materials and Methods: A comprehensive search was conducted across multiple electronic databases to identify in vitro and clinical studies evaluating the color match in tooth restoration, in terms of CIELAB (ΔEab) and/or CIEDE2000 (ΔE00) color dif- ferences metrics, using single-shade and multi-shade composites. The risk of bias was assessed using the Quality Assessment Tool For In Vitro Studies (QUIN Tool), while the revised Cochrane Collaboration's tool (RoB 2) was employed for randomized controlled clinical trials (RCTs). Meta-analyses were performed using RevMan to compare ΔEab and ΔE00 values between single- shade and multi-shade composites (p < 0.05).
Results: After initial screening, 15 in vitro studies and 4 RCTs met the inclusion criteria for qualitative synthesis, with 8 in vitro studies selected for quantitative analysis. The majority of in vitro studies were classified as medium risk of bias, while RCTs were ranked as low risk of bias. Meta-analyses performed on in vitro studies revealed that single-shade composites exhibited statis- tically significant higher color differences with the surrounding tooth structure compared to multi-shade composites, for both ΔEab and ΔE00 (p < 0.05). However, RCTs usually reported promising outcomes for single-shade materials.
Conclusions: This systematic review concluded that multi-shade composites provide a more accurate color match between tooth and direct restoration than single-shade materials when evaluated by instrumental analysis in laboratory settings.
Clinical Significance: Multi-shade composites exhibit superior color match properties in laboratory studies. However, single- shade composites are a promising alternative when observed visually in clinical settings
Color match of single-shade restorations after professional dental bleaching: An in vitro study
Get PDFBackground: Restorative dentistry aims to reproduce natural tooth shades through resin composites that must be layered to obtain colors, opacities, and translucencies, and therefore, clinical success is operator skill dependent. Aims: The purpose of this study is to evaluate the color shift of single-shade composite restorations before and after dental bleaching. Materials and methods: Eighty human extracted posterior teeth were restored with four single-shade composites (Omnichroma OM; Clearfil Majesty ES-2 Universal CL; Essentia Universal ES; Venus Diamond One VE) (n = 20 each). Standardized V class cavities were prepared on buccal side. VITA Easyshade V spectrophotometer was used to register VITA color and color coordinates 24 h before (T0), 24 h after (T1), and 1 week after (T2) dental bleaching (Opalescence Boost PF 40%). Color differences (ΔEab) and (ΔWID) were calculated and subjected to statistical analysis. Statistical analysis: Categorical variables were analyzed using Pearson Chi-square, and data from color coordinates were analyzed using one-way analysis of variance and Tukey's multiple comparison test with Bonferroni correction. Paired t-tests were performed to compare continuous measures between groups and treatment time. Results: Instrumental evaluations revealed statistically significant differences between materials (P < 0.05) with lower values for ES and VE samples followed by CL and OM at T0 and T1. At T2, OM and CL ΔEab values decrease getting closer to ES and VE. Conclusion: Single-shade composites seem to match with the surrounding bleached tooth
Effect of bleaching on the color match of single-shade resin composites
Get PDFPurpose: To evaluate the color match of single-shade resin composites before and after bleaching procedures, through instrumental and visual analyses. Methods: Class V cavities were created on the buccal surfaces of 80 extracted human molars, restored with 4 single-shade composites (Omnichroma; Clearfil Majesty ES-2 Universal; Essentia Universal; Venus Diamond One). A spectrophotometer (VITA Easyshade V) was used to evaluate the tooth/resin color match before (T0), and 24 h (T1) and one week (T2) after dental bleaching (Opalescence Boost PF 40%). Color variations (ΔE00) were calculated and statistically analyzed (P < 0.05). Visual analysis was performed before and after tooth bleaching. Results: Spectrophotometric evaluations revealed statistically significant differences between materials at T0, T1, and T2 (P < 0.05). Visual analysis reported excellent and very good grades (0 and 1, respectively), irrespective of the materials and timepoints. Conclusion: Data seem to indicate that single shade composites are able to shift their color when the surrounding tooth undergoes bleaching effects. Single-shade composites seem to achieve a good color match with the surrounding tooth structure, before and after professional bleaching
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Get PDFWe 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
Push-out bond strength and SEM fractographical analysis of hollow fibre posts used with self-adhesive resin cement: a pilot study
Get PDFDetachment is the major cause of failure of endodontic fibre posts. Hollow posts have been recently introduced to overcome such issue. The primary aim of this pilot study was to compare the push-out bond strength of hollow posts and traditional solid posts. Eight round-shaped single-canal premolars extracted for periodontal reason were selected as sample and equally randomized into two groups: (i) traditional solid fibre posts-TECH21xop and ii) hollow fibre posts-TECHOLE. A dual-curing self-adhesive cement (new TECHCEM) was used for posts placement. Six horizontal sections-two from each portion of the root (coronal, middle and apical)-were obtained from each sample root, yielding a total of 24 sections for each group. Push-out test was performed on the sections and bond strength values were compared between groups and within each group. Scanning electron microscope (SEM) fractographical analysis was conducted on each section. Additional SEM and EDX analyses were performed on new samples of both posts, to assess fibres density and distribution, and the chemical composition of the fibres and the matrix. Hollow posts showed a significantly higher push-out bond strength (6.36 +/- 1.22 MPa) than solid posts (3.64 +/- 1.62 MPa). Among the three root portions of the same group, there was no significant difference in bond strength. In both groups, the most frequent type of fracture was a mixed adhesive failure with the cement covering 0 to 50% of the post perimeter. Hollow post fibres appear more similar in size and have a more homogeneous distribution, compared to solid posts. The two post types also have different chemical compositions
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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