| کلیدواژههای انگلیسی مقاله |
Composite Resins, CoreRestore, Shear Strength, Yttria Stabilized Tetragonal Zirconia, IntroductionThere are several methods mentioned in the literature for restoring damaged anterior teeth [ 1,]. Increased demand for esthetic restorations and unpredictable biocompatibility of some metal alloys has attracted attention toward metal-free restorations in recent decades [ 2,] and has turned them to a routine choice in prosthetic treatments [ 3,].Several materials can be used to compensate the missing tooth structure as a core foundation for extra-coronal restorations. The choice of proper material depends on the amount of remaining tooth structure, esthetics, finances, and treatment duration [ 4,]. The non-precious gold alloy (NPG), containing more than 80% copper, first was introduced in 1987. It has optimal physical properties as dental post-cores with simpler preparation and handling compared to nickel-chromium ones [ 5,].In translucent ceramic crown systems, there is concern about the impact of abutment shade beyond the restoration [ 6,]. For high translucent restorations with a thickness less than 1.6mm, the shade of underlying abutment may affect the final esthetic result [ 6,]. The development of tooth colored post-core systems, such as composite resin or ceramic dowel and core restorations, has improved esthetics [ 7,]. Non-metallic post-cores not only provide more esthetic over metallic posts, but also reduce the risk of corrosion and toxicity. Nowadays, many composite resin systems are available specifically designed for core build-up with more fillers, higher strength, and easier manipulation [ 8,- 11,].The bond strength of core foundation and crown plays essential role in success rate of full ceramic restorations [ 12,]. Previous studies about bond strength of zirconia crowns have been concentrated on surface treatments before cementation and use of various adhesive resins [ 13,- 16,]. The use of airborne particle abrasion technique results in improvement of the bond between resin cement and yttria-stabilized tetragonal zirconia polycrystalline ceramics by producing roughness at the zirconia surface. This surface roughness increases the surface wettability and micromechanical retention with luting agents [ 17,].Several methods including use of phosphoric acid ester monomers like 10-methacryloyloxy-decyl-dihydrogen- phosphate, zirconia coupling agent, and organic silane have been suggested to improve zirconia crowns bond strengths [ 18,- 19,]. The phosphate containing monomers behave similar to the silane coupling agents because they allow the copolymerization between the methacrylate group and the monomers of a composite resin system. In addition, they bond with the metal oxides in the substrate with phosphoric acid groups. Carboxylic acid is another monomer, which plays an important role in the bond formation [ 17,]. High amounts of bond strength were reported in the literature when using methacryloyloxy-decyl-dihydrogen-phosphate- containing resin cement (Panavia F 2.0 Kuraray) [ 20,].Bond strength of zirconia crowns to different core materials has been investigated in limited studies [ 4,]. So, the aim of this study was to evaluate shear bond strength (SBS) of zirconia to four different core materials. The null hypothesis of this study was that the core material has no effect on the SBS of zirconia crowns.Materials and Method40 disk samples of multilayer zirconia (Katana Zirconia ML, Kuraray Noritake Dental Inc., Aichi, Japan) were made with 10mm in diameter and 3mm in thickness) using computer-aided design/computer-aided manufacturing technique (CAD/CAM) (Ammangirrbach, Ceramill motion 2, Koblach, Austria). All samples were polished by silicon carbide paper (600 grit matador 991A soflex starcke GmBH&,amp amp Co., Melle, Germany) and then were mounted in acrylic molds (1&,times 2&,times 4.5 cm) by locating them in the same level of acrylic resin surface. Specimens were sandblasted with 50 &,micro m aluminum oxide particles under 3 bar pressure for 15 seconds from a 10mm distance. All samples were cleaned in ultrasonic bath with 96% propanol for 3 min. Subsequently they were divided into four groups according to the core material tested (N=10).In the group 1, composite resin cylinders were built up using plastic cylinder (4mm height &,times 3mm diameter) and were covered with glass slide in order to reach the smooth surface. All the samples were light cured for 40 seconds at power density of 600 MW/cm2 with light-emitting diode light-curing unit. In the group 2, NPG alloy cylinders (4mm height &,times 3mm diameter) were fabricated by cylindrical pattern resin LS molds and casted with NPG alloy by lost wax technique. In the group 3( dentin cylinders), 10 freshly non-carious extracted human third molars were cleaned and disinfected in 0.5% chloramine T solution for 7 days. The roots were cut below the cementoenamel junction using a double-sided diamond disk and cylindrical specimens were obtained using trephine with 3mm inner diameter and 4mm height. In the group 4, zirconia cylinders (4mm height &,times 3mm diameter) were prepared from Katana zirconia blocks using computer-aided design/computer-aided manufacturing technique. All materials and appliances are described in detail in Table 1,.MaterialComposition ManufacturerKatana zirconiaZirconium oxideKuraray Noritake Dental Inc., JapanYttrium oxide |
| نویسندگان مقاله |
Sara Tavakolizadeh |
Dept. of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Mohamad Dehghan |
Dept. of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Rahab Ghoveizi |
Dept. of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Anahita Fayyazi |
Post Graduate Student of Prosthodontics, Dept. of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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