Bioceramics 23

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Authors: N. Demirkol, Onur Meydanoglu, Hasan Gökçe, F.N. Oktar, E.S. Kayali
Abstract: In this study, microstructures and mechanical properties of sheep hydroxyapatite (SHA) and commercial synthetic hydroxyapatite (CSHA)-MgO composites were investigated. The production of hydroxyapatite (HA) from natural sources is preferred due to economical and time saving reasons. The goal of development of SHA and CSHA based MgO composites is to improve mechanical properties of HA. SHA and CSHA composites were prepared with the addition of different amounts of MgO and sintered at the temperature range of 1000-1300 °C. The physical and mechanical properties were determined by measuring density, compression strength and Vickers microhardness (HV). Structural characterization was carried out with X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies. In all composites, mean density values and mechanical properties increased with increasing sintering temperature. The increase of MgO content in SHA-MgO composites showed better mechanical properties in contrast to CSHA-MgO composites. Although the highest hardness and compression strength values were obtained at the SHA-10wt% MgO composite sintered at 1300°C, higher hardness and compression strength values were achieved with 5 wt% MgO addition at the CSHA-MgO composites when compared to SHA-MgO composites sintered between 1000-1200°C.
Authors: G. Akgungor, Y. Olcer, D. Şen, B. Tunçelli
Abstract: The occlusal design of dental restorations should stay in harmonic relation to the remaining dentition. In CAD/CAM dentistry, the occlusion is generated by the CAD software based on standard morphologies from the dental database. An automated adaptation process of this standard morphology to an individual clinical situation is difficult and leading to manual adaptation of the proposal with design tools. The new biogeneric software of the chairside CAD/CAD system (CEREC) automatically collects optic measurement of the preparation side including mesial and distal neighbor teeth and antagonist teeth to design a restoration with a patient specific occlusal morphology. This clinical report demonstrated a case, which was treated with ceramic onlay designed and milled with CEREC system used in biogeneric design mode. Digital impression of the preparation was taken with the intraoral camera. Buccal scan,technique was used for taking the occlusal record. Preparation and antagonist images were automatically correlated by software and a virtual articulator was created. After trimming the virtual model, preparation margins were outlined with the automatic margin finder option of the software and then the insertion axis of the restoration was determined. The biogeneric restoration proposal was then automatically seated to the virtual model and desired changes were performed with the design tools of the software. The restoration was milled from feldspathic ceramic block.
Authors: G. Akgungor, N. Kilincaslan, D. Şen
Abstract: The single anterior tooth replacement remains a complex aesthetic challenge for clinicians and technicians in prosthetic dentistry. Maxillary central incisors are the key point of an esthetic smile and should exhibit a high degree of symmetry across the midline. Matching the shape and contours to the adjacent central incisor is the crucial factor to achieve an esthetic result. The CEREC system is the first to use chairside CAD/CAM system, which allows the dentist to provide ceramic restorations in a single appointment without time consuming laboratory procedures.This clinical report demonstrates the effective usage of CEREC system with the biogeneric reference design mode for designing and milling of a laminate veneer restoration in one appointment.Digital images of the preparation and bite registration were captured using an intraoral camera and virtual models were created. With the biogeneric reference design mode of CEREC 3.0 software, the image of the contralateral central incisor is mirrored, positioned over the preparation, and then refined. Among a variety of ceramic blocs available for CEREC system, the restoration was milled from feldspathic ceramic block.
Authors: A. Vatali, E. Siarampi, Eleana Kontonasaki, Nikolaos Kantiranis, T. Zorba, N. Vouroutzis, Konstantinos M. Paraskevopoulos, Petros Koidis
Abstract: High strength of Yttria stabilized tetragonal zirconia polycrystal (Y-TZP) zirconia ceramics are sensitive to low temperature degradation (LTD) that leads to exaggerated tetragonal to monoclinic transformation and a surface to depth propagating degradation that diminishes their mechanical properties. In vitro tests for accelerating ageing have been proposed for the prediction of zirconia ceramics clinical performance. The aim of the present work was to investigate the in vitro ageing of a cold isostatic-pressed zirconia ceramic for all ceramic restorations. Bar-shaped specimens milled from a zirconia block (Ivoclar IPS e.max ZirCAD) were sintered to full density, mirror-polished and cut into two equal pieces. One piece was used as control while the other was subsequently aged (steam 134°C / 2 bars / 10 hours). Atomic Force Microscopy (AFM) was used to evaluate the surface profile and the micro-structural features before and after ageing. Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction Analysis (XRD) were used to determine the degree of the m-ZrO2 transformation. Ageing resulted in an increase of the surface roughness, while the formation of monoclinic spots on the surface of the specimens was verified by surface uplifts in the AFM images. The peaks of the m-phase were clearly observed in the FTIR spectra while an average increase of 16% w.t. of the m-ZrO2 phase was recorded by XRD. Although, no sound lifetime predictions can be made from accelerated tests, based on the ISO standard that imposes that the m-phase should not exceed 25% wt after 5h at 134 °C and 2 bar pressure , it can be concluded that the tested ceramic resisted an extreme transformation that could negatively affect its clinical performance.
Authors: Cristian Ratiu, Simona Cavalu, V. Miclaus, C. Ober, I. Ratiu, O. Ponta
Abstract: The materials used for major sinus lift varies from autogenous or allogenous bone, to animal origin (xenograft) bone or synthetic (alloplastic) materials. A combination of bone substitutes, alloplastic graft with allogenic or xenogenic bone seems to give satisfactory results in terms of new bone formation and the long-term implant success rate. On the other hand, using PRP (Platelet Rich Plasma) mixed with bone substitutes seems to enhance graft vascularization and osseous regeneration, as well as faster healing. The novel sinus lift technique with PRGF (Plasma rich in Growth Factors) has demonstrated significant development of new bone, minimizing any complications in the event of Scheneiderian membrane perforation. The present study compares two clinical cases where major sinus lifts were performed using as regenerative material xenograft bone and porous titanium mixed with PRGF.
Authors: Shigeki Hontsu, Nobuhiro Kato, Ei Yamamoto, Hiroaki Nishikawa, Masanobu Kusunoki, Takashi Hayami, Kazushi Yoshikawa
Abstract: Before a tooth erupts, the ameloblasts are lost, which means that the tooth enamel does not regenerate itself after tooth eruption. In the present study, we attempt to regenerate the tooth enamel artificially using a flexible hydroxyapatite (HAp) sheet. First, a HAp film was deposited on a soluble substrate by pulsed laser deposition (PLD) using an ArF excimer laser. Next, the HAp film was collected as a freestanding sheet by dissolving the substrate using a solvent. The HAp sheet was adhered to the extracted human teeth using a calcium phosphate solution. The variation of the crystal structure of the HAp sheet with time was investigated by X-ray diffraction analysis. Furthermore, the variation in the mechanical characteristics with time between the HAp sheet and dental enamel were evaluated using tensile and scratch tests. The results suggest that the HAp sheet became fused to the tooth enamel within approximately one week.
Authors: Funda Yanıkoğlu, Gürol Özyöney, Nuran Özyöney, Dilek Tağtekin, Hesna Öveçoğlu, Mahir Günday
Abstract: For the dental restorations, ceramic materials have increasing popularities because of their biocompatibility and superior esthetics. IPS Empress which is leucite-reinforced glass ceramic is one of the most popular ceramics. IPS Empress II was developed in following years which is stronger than IPS Empress. In the dental applications some problems occur about ceramic restorations. Hence,this study was performed to examine the six-year clinical performance of IPS Empress II ceramic onlay and inlay restorations.
Authors: Mahmoud Azami, Sasan Jalilifiroozinezhad, Masoud Mozafari
Abstract: In this research, a novel biphasic solid solution consisted of Calcium fluoride (CF) and fluorinated-hydroxyapatite (FHAp) was successfully synthesized through a modified precipitation method using buffer solution. The obtained results confirmed the formation of biphasic nanocrystalline powder composed of about 46% CF and 54% (w/w%) FHAp. This product can be considered as an osteoconductive dental filler or implant with the ability of dental carries prevention due to release of fluorine ions. Herein, the usage of buffer solution for this purpose not only can produces biphasic powder but also provides the possibility of establishment of a continuous synthesis method without manual interfere for adjusting pH of the reactor.
Authors: Tomaz Kosmač, A. Kocjan, M. Golobicˇ, P. Jevnikar
Abstract: The aim of this study was to functionalize the surface of Ce-TZP/Al2O3 dental ceramic with a nano-structured alumina coating to improve resin bonding. A total of 40 densely sintered disc-shaped specimens (15.5 + 0.03 mm in diameter and 2.6 + 0.03 mm thick) were produced from commercially available NANOZIR blocks and randomly divided into 2 groups of 20. Half of the discs in each group received an alumina coating that was fabricated by exploiting the hydrolysis of aluminum nitride (AlN) powder. The coating was characterized using scanning electron microscopy (SEM). The shear bond strength of the self-adhesive luting cement G-cem was then studied for the coated and uncoated surfaces before and after thermocycling (TC). The SEM analysis revealed that the application of an alumina coating to Ce-TZP/Al2O3 ceramics created a highly retentive surface for resin penetration. The resin bond strength to the coated groups was significantly higher than to the uncoated groups, both before and after TC (p ≤ 0,05).
Authors: Xanthippi Chatzistavrou, Konstantinos M. Paraskevopoulos, Vehid Salih, Aldo Roberto Boccaccini, Toshihiro Kasuga
Abstract: The aim of this work was to improve a newly developed family of glass-ceramic composite materials by incorporating silver ions in the ceramic structure, thus developing new Ag-doped materials with the ability of showing antibacterial activity for dental applications. Two different sol-gel methodologies were applied for the fabrication of colorless, homogenous and chemically durable materials which can slowly release silver ion for relatively long periods. Both methods led to the successful development of Ag-doped glass-ceramics with silver ions incorporated in the structure that can slowly release in buffer solution, during a period of 45 days. The potential, application of these materials involve the development of bioactive surfaces on dental substrates which can seal the marginal gap creating a bacterial free environment finally supporting the success of dental restorations.

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