Estudio experimental in vitro de la adhesión entre la cerámica de óxido de circonio y distintos cementos de resina compuesta.

La creciente demanda de tratamientos dentales estéticos y el continuo avance de la investigación ha permitido que en la actualidad podamos recurrir a distintos materiales cerámicos según las necesidades de tratamiento requeridas. Dentro de estos materiales cerámicos encontramos la cerámica de óxido de circonio, la cual presenta numerosas ventajas en cuanto a opacidad, resistencia y biocompatibilidad, pero se desconoce su comportamiento a la hora de unirse a las resinas compuestas, utilizadas estas como material de cementado. OBJETIVOS: Evaluar la fuerza de adhesión entre el óxido de circonio y distintos cementos de resina compuesta mediante un ensayo de cizalla. Estudiar a microscopia electrónica la cerámica de óxido de circonio sin tratar y una vez modificada con diferentes tratamientos de superficie para analizar la alteración producida en la misma. METODOLOGÍA: Se confeccionaron 130 cilindros cerámicos Lava TM. Se realizó un arenado con óxido de aluminio 80 µm o un chorreado con Cojet Sand. Se aplicó silano, agente adhesivo y/o Clearfil Ceramic Primer. Se adhirieron 130 cilindros de cemento de composite, seleccionándose dos de polimerización dual (Variolink II y Panavia F) y dos autopolimerizables (Rely X y Multilink). Se realizó un ensayo de cizalla, un estudio a microscopia óptica para localizar el tipo y la ubicación del fracaso, un estudio a microscopia electrónica (SEM y TEM) y un análisis estadístico utilizando las pruebas de Mann Whitney, Kruskal-Wallis y t student (α=0.05). RESULTADOS: Las dos mejores combinaciones fueron Lava + Arenado + Clearfil SE Bond Primer + Porcelain Activator + Panavia F y Lava + Cojet + Clearfil Ceramic Primer + Variolink II (Grupos 4 y 3 respectivamente). Las peores técnicas fueron Lava + Arenado + Silano + Rely X y Lava + Arenado + Silano + Multilink (Grupos 7 y 10). El fallo adhesivo (separación del cemento de la cerámica) se produce a menor fuerza que el fallo cohesivo (rotura del cemento). Se observó a microscopia electrónica que los tratamientos de superficie practicados modifican la superficie de la cerámica de óxido de circonio, haciéndola más rugosa y retentiva y propiciando que exista una mejor interdigitación entre la cerámica y el cemento. CONCLUSIONES: Los cementos que presentaron mejores valores son los de fraguado dual cuando se asociaron a un arenado o silicatización y un adhesivo que contuviera MDP.INTRODUCTION: The increasing demand for esthetic dental treatments and ongoing advances in research have lead to a situation whereby dentists now have recourse to a range of different ceramic materials, chosen according to the needs of each case. Amongst these, zirconium oxide ceramic offers several advantages in terms of opacity, strength and biocompatibility but when it is joined to composite resins used for bonding its behavior is unknown. OBJECTIVES: To evaluate bond strength between zirconium oxide and different resin composite cements by means of shear testing. To carry out electron microscope examination of zirconium ceramic oxide with an untreated surface and with different surface treatments in order to analyze any alterations produced. MATERIALS AND METHODS: 130 Lava TM ceramic cylinders were fabricated. These were sandblasted with 80µm aluminum oxide or with Cojet Sand. A silane coupling agent, adhesive and/or Clearfil Ceramic Primer were applied. 130 resin composite cement cylinders were bonded, selecting different bond techniques, two with dual polymerization (Variolink II and Panavia F) and two with self-polymerizing cements (Rely X and Multilink). Shear bond testing was carried out, and samples were subjected to optical microscope examination in order to locate and classify the type of bond failure, electron microscope (SEM and TEM) and statistical examination, applying the Mann Whitney, Kruskal-Wallis and student t tests (α=0.05). RESULTS: The two most successful combinations were Lava + Sandblasting + Clearfil SE Bond Primer + Porcelain Activator + Panavia F and Lava + Cojet + Clearfil Ceramic Primer + Variolink II (Groups 4 and 3 respectively). The least successful techniques were Lava + Sandblasting + Silane + Rely X and Lava + Sandblasting + Silane + Multilink (Groups 7 and 10). Bond failure (separation of cement from ceramic) was produced with less shear force than cohesive failure (breakage of the cement material itself). Electron microscope examination observed that surface treatment modified the zirconium oxide ceramic surface, making it rougher and more retentive, producing greater interdigitation between ceramic and cement. CONCLUSIONS: The cements that produced higher bond strength values were those with dual polymerization in combination with either sandblasting or silica coating and an adhesive containing MDP

Bonding to silicate ceramics : conventional technique compared with a simplified technique

Silicate ceramic bonding is carried out by acid-etching with hydrofluoric acid (HF) followed by an application of silane. By replacing HF with ammonium polyfluoride, contained in the same flask as the silane, the number of steps in this clinical procedure, can be reduced, while maintaining bond strength values, and reducing toxicity. A shear bond test was performed to compare the conventional and the simplified surface treatment techniques. Twenty ceramic samples were fabricated from IPS emax CAD® ceramic (Ivoclar Vivadent) and divided into two groups (G1 and G2) (n=10). The conventional technique was applied to G1 samples, and the simplified technique to G2 samples. A resin cement cylinder was bonded to each sample. Afterwards, samples underwent shear bond strength testing in a universal test machine. G1 obtained 26.53±6.33 MPa and G2 23.52±8.41 MPa, without statistically significant differences between the two groups. Monobond Etch Prime appears to obtain equivalent results in terms of bond strength while simplifying the technique. Further investigation is required to corroborate these preliminary findings

Shear bond strength of debonded ceramic restorations re-cemented by means of a cleaning and retreatment protocol

Background: As there is no standard method for re-cementing debonded partial ceramic restorations, the aim of this study was to evaluate the use of a non-invasive thermal protocol for cleaning and retreatment, and to study its influence on shear bond strength. Material and Methods: Twenty ceramic samples (IPS e.max CAD®) were bonded to composite cement cylinders and underwent a shear bond strength test (G1, n=20). A second group was created (G2, n=20), representing debonded restorations. To simulate debonding, the samples were artificially contaminated with composite cement. After debonding, these underwent a thermal protocol to remove remaining adhesive. After rebonding to the composite cement cylinders, samples underwent the shear bond strength test. Results: Median bond strengths for G1 and G2 were 7.28±3.23; 7.06±3.41 MPa, respectively, without significant difference between the groups (p=0.983). Conclusions: Debonded lithium disilicate glass-ceramic restorations should undergo a laboratory cleaning and retreatment protocol before being returned to the clinic for rebonding

Traction test of temporary dental cements

Classic self-curing temporary cements obstruct the translucence of provisional restorations. New dual-cure esthetic temporary cements need investigation and comparison with classic cements to ensure that they are equally retentive and provide adequate translucence. The objective is to analyze by means of traction testing in a in vitro study the retention of five temporary cements. Ten molars were prepared and ten provisional resin restorations were fabricated using CAD-CAM technology (n=10). Five temporary cements were selected: self-curing temporary cements, Dycal (D), Temp Bond (TB), Temp Bond Non Eugenol (TBNE); dual-curing esthetic cements Temp Bond Clear (TBC) and Telio CS link (TE). Each sample underwent traction testing, both with thermocycling (190 cycles at 5-55º) and without thermocycling. TE and TBC obtained the highest traction resistance values. Thermocycling reduced the resistance of all cements except TBC. The dual-cure esthetic cements tested provided optimum outcomes for bonding provisional restorations

Zirconia in fixed prosthesis. A literature review

Statement of problem: Evidence is limited on the efficacy of zirconia-based fixed dental prostheses. Objective: To carry out a literature review of the behavior of zirconium oxide dental restorations. Material and Methods: This literature review searched the Pubmed, Scopus, Medline and Cochrane Library databases using key search words 'zirconium oxide,' 'zirconia,' 'non-metal restorations,' 'ceramic oxides,' 'veneering ceramic,' 'zirconia-based fixed dental prostheses'. Both in vivo and in vitro studies into zirconia-based prosthodontic restoration behavior were included. Results: Clinical studies have revealed a high rate of fracture for porcelain-veneered zirconia-based restorations that varies between 6% and 15% over a 3- to 5-year period, while for ceramo-metallic restorations the fracture rate ranges between 4 and 10% over ten years. These results provoke uncertainty as to the long-term prognosis for this material in the oral medium. The cause of veneering porcelain fractures is unknown but hypothetically they could be associated with bond failure between the veneer material and the zirconia sub-structure

Methodology in specimen fabrication for in vitro dental studies : standardization of extracted tooth preparation

Specimen preparation for in vitro study suffers a general lack of methodological homogeneity, as well as a lack of uniformity in the materials selected for fabricating them. This situation prevents comparisons between studies. When a specimen is not of dental origin it is not possible to study adhesion or bonding techniques realistically. The objective is to design and implement a method of specimen preparation that permits universal standardization for use in in vitro studies. A metal stump of specified dimensions was designed and fabricated by hand. It was scanned, the data digitalized, perfecting and standardizing the dimensions. Ten human molars were adapted to the size and shape of a standard milling block. A Cerec 3D inLab Cerec milling unit was used to prepare the molars to match the digitalized model. Ten specimens with identical dimensions were obtained. CAD-CAM technology allows the preparation of natural extracted teeth to be standardized and could be used to establish a reproducible method that would facilitate comparison between different in vitro studies, and reduce bias arising from variations in sample fabrication

Rapid diagnosis of the geospatial distribution of intertidal macroalgae using large-scale UAVs

Macroalgae have been used as indicators of the health of coastal ecosystems, they function as sinks of CO2 and are essential contributors to primary production. With the increase in anthropogenic activities, it is crucial to assess the impact of such activities on these ecosystems. As traditional surveying techniques, although accurate, are time-consuming and their area coverage is limited, novel techniques are required to monitor the coverage and diversity of intertidal macroalgae. We propose a methodology using the free-source Semi-Automatic Classification Plugin from QGIS to use UAV and multispectral cameras for the spatiotemporal monitoring of intertidal macroalgae. We also compared the performance of six classifiers: Minimum Distance (MD), Maximum Likelihood (ML), Spectral Angle Mapping (SAM), Multi-Layer Perceptron (MLP), Random Forest (RF) and Support Vector Machine (SVM), for three types of macroalgae classification: general, taxonomical groups and species. As proof of concept, an intertidal rocky shore in a marine protected area (NW Spain) was studied for four months. RF and SVM achieved similar results, with both being recommended for the general (OASVM = 97.4±1.7 and OARF = 98.3±1.7) and taxonomical groups (OASVM = 91.6±1.9 and OARF = 89.2±4.5). SVM and ML were found to be more suitable for species classification (OASVM = 77.4±11.4 and OAML = 74.2±9.7). SAM and MLP provided the least performant species classifiers because of the overlap in the macroalgae spectral signatures. The plugin showed limitations when tuning the input parameters of the MLP classifier and did not let to add a validation dataset. Additionally, we present an open-access GIS web application, Alganat 2000 GIS web, to facilitate the monitoring and management of coastal areas. We conclude that the proposed methodology using the SVM or ML classifiers is an effective tool for assessing intertidal macroalgal assemblages. Its easy and rapid implementation is beneficial for researchers who are not very familiar with coding and machine learning frameworks and reduces the time and cost of fieldwork. As future work, we propose the combination of the multispectral bands with topographic and spectral indices and to research the application of deep learning models to the classification of intertidal macroalgaeAgencia Estatal de Investigación | Ref. PRTR-C17.I1Universidade de Vigo/CISU

Monitoring and mapping of intertidal macroalgae using low-cost geospatial automated techniques

The global extent of macroalgae is declining with important consequences on marine biodiversity and ecosystem processes. Tracking the status and trends of macroalgal cover is, therefore, an emerging priority for ocean and coastal management. A remote sensing technique combining UAVs surveys with in situ data acquisition was developed to map intertidal macroalgae from rocky shores in a marine protected area, the Atlantic Islands of Galicia National Park (Illas Cíes, NW Spain). The classifcation by groups (brown and green macroalgae) achieved a good precision. A more precise classifcation would be achieved by focusing on those spectral bands where the highest diferences between species appeared.Peer Reviewe

Influence of bruxism on survival of porcelain laminate veneers

Objectives: This study aims to determine whether bruxism and the use of occlusal splints affect the survival of porcelain laminate veneers in patients treated with this technique. Material and Methods: Restorations were made in 70 patients, including 30 patients with some type of parafunc - tional habit. A total of 323 veneers were placed, 170 in patients with bruxism activity, and the remaining 153 in patients without it. A clinical examination determined the presence or absence of ceramic failure (cracks, frac - tures and debonding) of the restorations; these incidents were analyzed for association with bruxism and the use of splints. Results: Analysis of the ceramic failures showed that of the 13 fractures and 29 debonding that were present in our study, 8 fractures and 22 debonding were related to the presence of bruxism. Conclusions: Porcelain laminate veneers are a predictable treatment option that provides excellent results, rec - ognizing a higher risk of failure in patients with bruxism activity. The use of occlusal splints reduces the risk of fractures