Oral and Dental Medicine

Permanent URI for this communityhttps://iorep.miuegypt.edu.eg/handle/20.500.13071/5

Browse

Now showing 1 - 3 of 3

Restricted
Evaluation of different oral conditions on the color stability and surface roughness of CAD/CAM hybrid ceramics versus IPS e.max : An In vitro study /
ELSayed, Alaa Hamed,; Supervisor : Lamia sayed Kheiralla, Rana Mahmoud Sherif.
Color matching and long-lasting color stability of dental materials are two of the major factors that influence the success or the failure of any esthetic dental restoration. In addition, the surface texture of a tooth colored restoration has a major effect on plaque accumulation, discoloration, wear and the esthetic appearance. Ideally, for any material to be used, it should fulfill four main criteria; esthetics, strength, accuracy and passive fit. Dental ceramics set ground as the most natural in appearance, texture, color, reflectance, and translucency, where distinguishing them from the natural teeth is sometimes even impossible. Moreover, it was approved that ceramics have optimum biocompatibility to oral tissues and reduced tendency of maintaining bacterial plaque as well as it does not absorb water nor conduct heat. A Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) was introduced to dentistry in the mid-1980s. Several types of CAD/CAM ceramic blocks have been developed for restoration fabrication, including feldspathic ceramic, leucite-reinforced ceramics, lithium disilicate ceramics, and zirconium oxide ceramics. CAD/CAM offer high esthetic demands, short chair side time, and less number of visits. Although dental ceramics are widely used for inlays, onlays, single crown and fixed partial dentures, they still have some disadvantages, such as high cost, the risk of fracture due to their brittleness, high wear to the opposing natural dentation, handling concerns (fragility during trial insertion and cementation) and veneer failure. Therefore, there has been an increasing interest in the use of newly introduced hybrid ceramic blocks to overcome some of dental ceramics drawbacks, due to their optimal resilience, stiffness, and wear characteristics together with their excellent esthetics. Currently, there is no much documentary evidence available regarding the effect of the different oral media on the milled CAD/CAM hybrid ceramic regardless to glass ceramic restorations. Thus, it was worthy to investigate the color stability and surface roughness of a recently introduced CAD/CAM hybrid ceramic (CERASMART) to lithium disilicate (IPS e.max CAD) ceramic under two beverage solutions (coffee – Mirinda orange juice) and a home-bleaching agent.
Restricted
Fatigue Resistance of Custom Made Resin-Ceramic, One-Piece and Two-Piece Implant Abutment/Crown : (In Vitro Study) /
Issa, Fady Alfred Boulos Nakhla,; Supervisor : Hesham Katamish, Tarek Salah.
In recent years, social emphasis on esthetics and general appearance has reached an all-time high focus. Every practitioner is now faced with patients that care more about the appearance of their teeth than the actual treatment plan presented. The increased demand for esthetics by both patients and clinicians has revolutionized the treatment procedures taken in dental practice. High awareness and research was implemented towards conservatism and dental practice is now focusing on minimally invasive techniques in all procedures undertaken. Dental Implants are now the cornerstone for restoration of missing teeth and oral rehabilitation. Showing a 95-97% success rate of single implant-supported restorations.1 Providing favorable biomechanical properties, titanium implants and abutments are the golden standard for implant-supported restorations2. However, this causes an esthetic disadvantage, especially in highly esthetic zones. Titanium abutments cause an unnatural bluish-gray appearance to the surrounding soft tissue, specifically around thin layered gingiva. Therefore a tooth-colored abutment is needed to provide acceptable esthetics. For this reason several types of esthetic all ceramic abutments were introduced, offering a variety of tooth-colored shades and stains to accommodate a metal-free natural and esthetic look. In comparison to titanium abutments, ceramic abutments are more aesthetic with less, yet acceptable strength. 3–5 The introduction of Computer Aided Design/Computed Aided Manufacturing (CAD/CAM) technologies in the 1980s provided access to a standardized manufacturing process. Offering a more predictable, accurate and reproducible restoration with reduced production cost. As a result, a new generation of ceramic and composite materials was introduced to the market, opening the door for various uses and restorative designs to be introduced in dental practice.6 CAD/CAM materials (ceramics & zirconia) were tested and used for various prosthetic restorative modalities, including crown and implant abutments. Due to the brittle nature of ceramics, the abutments were shown to exhibit high stress propagation and concentration on their respective implants and bone specifically in high load areas such as posterior teeth. They also cause abrasion to the opposing dentition. The highly condensed particle nature of zirconia while exhibiting high strength and acceptable mechanical properties, they still provided an esthetic complication due to their dull opaque shade.7,8 Composite resin material, on the other hand, suffer from increased material wear, loss of surface polish, and color instability. Most recently, a new polymer infiltrated hybrid ceramic material has been developed by several companies for CAD/CAM application. Specifically, the VITA Company produced the VITA ENAMIC CAD/CAM blocks. The material is composed of a porous feldspathic ceramic mesh infiltrated by an acrylic polymer network material, providing mechanical properties similar to natural tooth properties. To the best of our knowledge, the hybrid ceramic material was not tested as an implant abutment. The fatigue behavior and the fracture resistance of the material as an implant supported abutment is unknown and was not investigated yet.
Restricted
The Efficacy of Wear a CAD/CAM Hybrid Ceramic Restoration on Color Stability : An In Vitro Study /
Abdou, Alaa Samy Mahmoud ELSayed,; Supervisor : Omaima El Mahallawi, Lomaya Ghanem.
Over the past two decades, the interest and demand for esthetic restorative materials increased for dentists as well as patients. This lead to the popularity of dental ceramics in dentistry, due to their biocompatibility, low plaque accumulation, superior esthetics, color stability, chemical inertness, good compressive strength and abrasion resistance. However, dental ceramics have some major disadvantages including low tensile and flexural strength making the material brittle and subjected to fracture, and being abrasive to the opposing natural dentition due to difference in wear resistance compared to the natural tooth enamel. When a ceramic restoration surface texture is altered by wear, it results in formation of a rough discolored surface that collects debris leading to loss of initial esthetic color and wearing of opposing dentition. Thus the excessive differential wear of teeth and ceramic materials has harmful effects on the biological, functional and esthetic condition of the masticatory system. Therefore the mechanical and the tribological properties of dental restorative materials are considered the uppermost challenges in the dental field in conjugation with the esthetic and artistic demands. Advances in digital impression technology and fabrication processes have led to a dramatic paradigm shift in dentistry and to the universal use of computer-aided design/computer-aided manufacturing (CAD/CAM) in the construction of indirect esthetic dental restorations. Most recent monolithic CAD/CAM blocks improved the physical and chemical properties of dental materials, by producing restorations that are homogenous, dense, porosity free, where complicated anatomies are controlled by the machining process eliminating human error and saving time. The current progresses in technology facilitated the innovation of monolithic CAD/CAM hybrid ceramic restorations, which are mainly composed of ceramic fillers that are enclosed in a polymer matrix. These monolithic blocks are prepared with accurate ceramic-to-resin ratios and evenly distributed ceramic particles. Hybrid ceramics combined the properties of dental ceramics and resin composites in a single restoration. They have the durability, long lasting esthetics, surface gloss and finish retention of dental porcelain along with the ease of handling, improved flexural strength and wear kindness of composite resin material. This research aims to evaluate, the wear efficacy of a CAD/CAM hybrid restoration on color stability.

Browse

Browsing Oral and Dental Medicine by Subject "Bridges (Dentistry)"