One-step polishing systems may be successfully used for polishing nanocomposites.
Surface treatment procedures such as grinding and polishing are needed to provide the ceramic dental restorative materials with proper fitting and occlusion. The treated surfaces are customarily glazed to improve the strength and smoothness. Though smoothness and wetting of the dental surfaces are important to minimize bacterial plaque retention, influence of the surface treatment and glazing procedures on the final surface roughness and its correlation to wettability are overlooked.In this work, effect of various treatment (diamond fraising, stoning, sanding and aluminum oxide and rubber polishing) and glazing (auto and overglazing) techniques on the final roughness and the resulting wettability of dental ceramic surfaces were investigated using scanning electron microscopy (SEM) observations and atomic force microscopy (AFM) scans, 75 scans per sample. The surfaces were characterized and assigned an average roughness measure, R a . The wettability of the same surfaces was evaluated using micro-contact angle measurements (25 micro-bubbles placed on a grid on each surface) to correlate the final surface roughness and wettability.The results show that overglazing prevails over surface irregularities from different treatment procedures and provides homegeneously smooth surfaces with mean R a < 10 nm. It also produces uniformly wetted surfaces with low contact angles around 20 • . The autoglazed surfaces are less smooth (mean R a around 50 nm) and displays sporadic topographic irregularities. They display larger and less uniform contact angles ranging between 35 • and 50 • . The results suggest that overglazing should be preferred after surface treatment to obtain a smooth and well-wetted dental ceramic surface.
The effect of inter-particle interactions on the slurry properties and the final surface roughness of the dental ceramic restoratives was investigated. A commercial dental ceramic powder, IPS Empress 2 veneer, was used as the raw material.The magnitudes of the particle-particle interactions were computed by the DLVO theory for the ceramic slurries of different electrolyte solutions (0.1 M, 0.25 M, 0.5 M, 0.75 M, 1 M NaCl and CaCl 2 ). As expected, the energies of particle-particle interactions were influenced significantly by the presence of electrolytes. These computations demonstrated that addition of electrolytes leads to a progressive depression of the repulsive double layer forces. The absence of these forces should inevitably lead to agglomeration caused by the ever-present van der Waals forces.The rheological measurements carried out using the slurries with same solution properties supported the findings of the DLVO computations. It was found that dental ceramic slurries showed a Newtonian behavior in the absence of electrolytes, which is indicative of little or no agglomeration in the slurry. On the other hand, the same slurries displayed a non-Newtonian, shear thinning behavior in the presence of electrolytes which can be attributed to agglomeration or gelation.Roughness of the ceramic surfaces produced from these slurries was studied by SEM analysis and profilometer measurements. Contact angle studies were also carried out on the same surfaces. It was observed that the surface became rougher initially with electrolyte addition to a maximum, most probably due to formation of isolated agglomerates due to a reduction of the repulsive double layer forces. After reaching a maximum, surface roughness decreased to a much lower value with further increase in electrolyte concentration. This was most probably caused by the formation of a relatively homogeneous, gel-like structure within the extensively agglomerated slurry due to a complete collapse of the double layer.
The purpose of this study is to determine the effect of animation technique on academic achievement of students in the "Human and Environment" unit lectured as part of the Science and Technology course of the seventh grade in primary education. The sample of the study consists of 58 students attending to the 7th grade of Erzurum MEB Yildizkent IMKB primary school under two different classes during the 2011-2012 academic year. While the lectures in the class designated as the animation group were given with animation technique, in the class designated as the control group Powerpoint presentations was utilized along with the traditional teaching methods. According to the findings, it was determined that animation technique is more effective than traditional teaching methods in terms of enhancing students' achievement. It was also determined in the study that, the Powerpoint presentations used together with the traditional teaching methods provided to the control group significantly help the students to increase their academic achievement.
Objectives This clinical report describes a relatively simple but esthetic, non-invasive and functional prosthodontic treatment option for a patient with missing tooth. Methods A patient with a missing maxillary left canine was non-invasively treated with a fiber reinforced composite (FRC) bridgework with an all ceramic (Empress II, Ivoclar Vivadent, Schaan, Liech-tenstein) pontic design, using laboratory technique. Results The restoration has served the patient for 2 year, seemingly without discomfort, and it has not required any maintenance. The patient has kept up with his oral hygiene. Conclusions Although additional clinical experience is necessary, fiber-reinforced composite materials can be used in combination with a lithium disilicate ceramic material in fixed partial dentures.
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