Zirkonya: Yapısı ve altyapı üretim tekniği

Zirkonya olarak da bilinen zirkonyum dioksit, zirkonyum metalinin kristal yapılı beyaz bir oksitidir ve kimyasal olarak bir metal oksiti, teknolojik olarak ise bir seramiktir. Bu seramik translusent, korozyona dirençli, biyouyumla ve radyoopak bir materyaldir ve diğer dental seramiklere kıyasla daha yüksek kırılma dayanımına sahiptir. Son 10 yılda CAD-CAM teknolojisindeki gelişmeleri takiben, zirkonya seramiğin dental klinik uygulamalar için kullanımı daha popüler hale gelmiştir. Materyal hakkında yapılan çok sayıda çalışma ve birçok üretici firma arasındaki rekabet bu materyalin hızlı bir şekilde gelişmesine yol açmıştır. Modern dental zirkonya; sabit protezler, inlay onlay restorasyonlar, implant dayanakları, post-kor restorasyonlar ve ortodontik braketler gibi çok farklı klinik uygulamalarda kullanım alanı sunmaktadır. Bütün bu seçenekler içinde, zirkonya seramik halen en yaygın olarak seramik veneerli sabit protezler için altyapı materyali şeklinde kullanılmaktadır. Translusentlikle birlikte materyalin yüksek kırılma direnci, bu seramiğin popülaritesinin temel nedenleridir. Ancak bütün bu olumlu estetik ve mekanik özelliklerine rağmen, zirkonya altyapı üretimi teknik hassasiyet gerektiren bir süreçtir ve kısa ve uzun dönemde başarı elde etmek için zirkonya altyapı seramiğinin yapısal bileşimi, sınırlamaları ve uygulama prensipleri iyi bilinmelidir. Bu makalede, zirkonya seramik ile ilgili güncel literatür derlenmiş ve yapısal bileşimi ile altyapı üretim süreci hakkındaki bilgiler özetlenmiştir.

Zirconia: Composition and framework fabrication technique

Zirconium-dioxide, also known as zirconia, is a white crystalline oxide of zirconium metal, which is chemically a metal-oxide and technologically a ceramic. This ceramic is a translucent, corrosion resistant, biocompatible and radiopaque material which has higher fracture strength when compared to other dental ceramics. In the last decade, the use of zirconia ceramic in dental clinical applications became more popular, following the advances in CADCAM technology. Numerous studies about the material and the competition among many manufacturer companies have led to a quick evolution of the material. Contemporary dental zirconia offers a wide variety of clinical applications such as fixed prosthetics, inlayonlay restorations, implant abutments, post-core restorations and orthodontic brackets. Among all these options, the use of zirconia as the framework of ceramic veneered fixed prosthesis is still the most common application area. The superior fracture strength of the material along with the translucency, are the main reasons of the popularity of this ceramic. However, although these favorable esthetic and mechanical properties; zirconia framework fabrication is a technique sensitive process and the structural composition, limitations and application guidelines of zirconia core ceramic should be well-known to achieve short and long term success. In this article, current literature regarding zirconia ceramic was reviewed and knowledge about the structural composition and framework fabrication process was summarized.

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1. Spear FM. The metal-free practice: myth? Reality? Desirable goal? J Esthet Restor Dent 2001;13:5967.
2. Heffernan MJ, Aquilino SA, Diaz-Arnold AM, Haselton DR,Stanford CM, Vargas MA. Relative translucency of six all-ceramic systems. Part 1: core materials. J Prosthet Dent 2002;88:49.
3. Reitemeier B, Hänsel K, Kastner C, Walter MH. Metalceramic failure in noble metal crowns: 7-year results of a prospective clinical trial in private practices. Int J Prosthodont 2006;19:3979.
4. Zarone F, Russo S, Sorrentino R. From porcelain-fused to-metal to zirconia: Clinical and experimental considerations. Dent Mater 2011; 27:83-96
5. Raptis NV, Michalakis KX, Hirayama H. Optical behavior of current ceramic systems. Int J Periodontics Restorative Dent 2006;26:3141.
6. McLean LW, Hughes TH. The reinforcement of dental porcelain with ceramic oxides. Br Dent J 1965;119:251 67.
7. Lughi V, Sergo V. Low temperature degradationaging- of zirconia: a critical review of the relevant aspects in dentistry. Dent Mater 2010;26:80720.
8. ISO standard 13356:2008
9. Ruff O, Ebert F. Refractory ceramics: I. The forms of zirconium dioxide. Z Anorg Allg Chem 1929;180:1941
10. Garvie RC, Nicholson PS. Structure and thermodynamical properties of partially stabilized zirconia in the CaOZrO2 system. J Am Ceram Soc 1972;55:1527.
11. Hannink RHJ, Kelly PM, Muddle BC. Transformation toughening in zirconia-containing ceramics. J Am Ceram Soc 2000;83:46187.
12. Kelly JR, Denry I. Stabilized zirconia as a structural ceramic: an overview. Dent Mater 2008;24:28998.
13. Swab JJ. Low temperature degradation of Y-TZP materials. J Mater Sci 1991;26:670614.
14. Att W, Grigoriadou M, Strub JR. ZrO2 three-unit fixed partial dentures: comparison of failure load before and after exposure to a mastication simulator. J Oral Rehabil 2007;34:28290.
15. Basu B, Vleugels J, Van Der Biest O. Microstructuretoughness-wear relationship of tetragonal zirconia ceramics. J Eur Ceram Soc 2004;24:203140.
16. Lance MJ, Vogel EM, Reith LA, Cannon RW. Low-temperature aging of zirconia ferrules for optical connectors. J Am Ceram Soc 2001;84:27313.
17. Chevalier J. What future for zirconia as a biomaterial? Biomaterials 2006;27:53543.
18. Denry I, Holloway JA. Ceramics for dental applications: A review. Materials 2010;3:351-368
19. Tsukuma K. Mechanical properties and thermal stability of CeO2 containing tetragonal zirconia polycrystals. Am Ceram Soc Bull 1986;65:13869.
20. Heussner K-H, Claussen N. Strengthening of ceria-doped tetragonal zirconia polycrystals by reduction-induced phase transformation. J Am Ceram Soc 1989;72:10446.
21. Sergo V, Schmid C, Meriani S, Evans AG. Mechanically induced darkening of alumina/ceria-stabilized zirconia composites. J Am Ceram Soc 1994;77:29716.
22. Denry I, Kelly R. State of the art of zirconia for dental applications. Dent Mater 2008;24:299307.
23. Suttor D, Hauptmann H, Schnagl R, Frank S. Coloringceramics by way of ionic or complex-containing solutions. US Patent 6,709,694; March 23, 2004
24. Al-Amleh B, Lyons K, Swain M. Clinical trials in zirconia: a systematic review. J Oral Rehabil 2010;37:64152.
25. Guazzato M, Albakry M, Ringer SP, Swain MV. Strength, fracture toughness and microstructure of a selection of all-ceramic materials. Part II. Zirconia-based dental ceramics. Dent Mater 2004;20:44956.
26. Raigrodski AJ. Contemporary materials and technologies for all-ceramic fixed partial dentures: a review of the literature. J Prosthet Dent 2004;92:55762.
27. Tinschert J, Natt G, Mautsch W, Spiekermann H, Anusavice KJ. Marginal fit of alumina-and zirconia-based fixed partial dentures produced by a CAD/CAM system. Oper Dent 2001;26:36774.
28. Luthardt R, Weber A, Rudolph H, Schone C, Quaas S, Walter M. Design and production of dental prosthetic restorations: basic research on dental CAD/CAM technology. Int J Comput Dent 2002;5:16576.
29. Chevalier J, Deville S, Munch E, Jullian R, Lair F. Critical effect of cubic phase on aging in 3mol% yttria-stabilizedzirconia ceramics for hip replacement prosthesis. Biomaterials 2004;25:553945.
30. Matsui K, Horikoshi H, Ohmichi N, Ohgai M, Yoshida H, Ikuara Y. Cubic-formation and grain-growth mechanisms in tetragonal zirconia polycrystal. J Am Ceram Soc 2003;86:14018
31. Sundh A, Sjögren G. Fracture resistance of all-ceramic zirconia bridges with differing phase stabilizers and quality of sintering. Dent Mater 2006;22:77884.
32. Oh WS, Anusavice KJ. Effect of connector design on the fracture resistance of all-ceramic fixed partial dentures. J Prosthet Dent 2002;87:53642.
33. Larsson C, Holm L, Lövgren N, Kokubo Y, Vult von Steyern P. Fracture strength of four-unit Y-TZP FPD cores designed with varying connector diameter. An in-vitro study. J Oral Rehabil 2007;34:7029.
34. Studart AR, Filser F, Kocher P, Luthy H, Gauckler LJ. Cyclic fatigue in water of veneer-framework composites for all-ceramic dental bridges. Dent Mater 2007;23:17785.
35. Komine F, Gerds T, Witkowski S, Strub JR. Influence of framework configuration on the marginal adaptation of zirconium dioxide ceramic anterior four-unit frameworks. Acta Odontol Scand 2005;63:3616.
36. Abduo J, Lyons K, Swain M. Fit of zirconia fixed partial denture: a systematic review. J Oral Rehabil 2010;37:866-76 37. Ruiz L, Readey MJ. Effect of heat-treatment on grain size, phase assemblage, and mechanical properties of 3 mol % Y-TZP. J Am Ceram Soc 1996;79:2331-40
38. Heuer AH, Claussen N, Kriven WM, Ruhle M. Stability of tetragonal ZrO2 particles in ceramic matrices. J Am Ceram Soc 1982;65:64250.
39. Cottom BA, Mayo MJ. Fracture toughness of nanocrystalline ZrO23mol% Y2O3 determined by Vickers indentation. Scr Mater 1996;34:80914.
40. Sailer I, Fehér A, Filser F, Gauckler LJ, Lüthy H, Hämmerle CH. Five-year clinical results of zirconia frameworks for posterior fixed partial dentures. Int J Prosthodont 2007;20:3838.
41. Larsson C, Vult von Steyern P, Sunzel B, Nilner K. Allceramic two- to five-unit implant-supported reconstructions. A randomized, prospective clinical trial. Swed Dent J 2006;30:4553.