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The key to increasing light transmission in materials such as zirconia, then, is to reduce the crystalline grain size, thereby reducing birefringent light scattering and increasing transmission. Restorative Ceramic Materials of Today There are primarily three different types of esthetic dental ceramic materials used today for crown & bridge restorations: glassy phase porcelains used in veneering, glassceramics such as lithium disilicate, and ceramics such as zirconia and alumina. Glassy Phase Porcelains Materials comprised of mainly glassy silica in the amorphous solid state (glassy matrix) make up the majority of the dental ceramics used today. Glassy phase veneering porcelains and pressable ceramics over substructures typically consist of glassy matrix feldspathic material with a leucite crystal phase. Typically, feldspathic leucite-reinforced glassy materials consist mainly of an amorphous silica phase (approximately 70 weight percent amorphous silica). The glassy phase veneering porcelains have been used for more than 30 years, and have become the benchmark for esthetics in dental restorations. These are typically used as the esthetic layer over substructures. Their low flexural strength and fracture toughness limit their indication to veneering layers, inlays and onlays (Fig. 1). However, glassy phase porcelains have the most esthetic optical properties in terms of simulating the optical transmission and color of natural dentition, due largely to the fact that these materials have the highest optical transmission when compared to other restorative ceramic materials (Fig. 8). Glass Ceramics Lithium disilicate glass-ceramics are approximately 30 weight percent amorphous silica and 70 weight percent crystalline lithium disilicate crystals, as shown via scanning electron microscopy (Fig. 9). These glass-ceramics are typically used for pressable all-ceramic crowns and monolithic ceramic CAD/CAM crown restorations. The optical transmission and resulting esthetics of shaded lithium disilicate are currently the benchmark for esthetic monolithic CAD/CAM ceramic crowns (Fig. 8). However, the flexural strength and fracture toughness limit their indication to single crown restorations (Fig. 1). Ceramics Zirconia and alumina dental ceramic materials are typically comprised of a nearly 100 weight percent crystalline phase, as shown via scanning electron microscopy (Fig. 10). These ceramics have been used in dentistry for the last 15 years due to their high flexural strength and fracture toughness (Fig. 1). The indications for partially stabilized tetragonal zirconia range from single crown restorations to full-arch frameworks, due to the material’s unique blend of strength and color when compared to other crystalline dental ceramics. The limitation to date has been that zirconia tends to have a higher opacity, which would seem to contraindicate use in the esthetic zone. Nevertheless, recent advances in zirconia ceramic processing technology have resulted in highly popular monolithic crown & bridge products, prescribed for use primarily in the posterior tooth region, and strides have been made to improve the material’s esthetic qualities. BruxZir Solid Zirconia, for example, which undergoes a unique, colloidal processing technique (patent pending), has been shown to exhibit improved optical transmission compared to zirconia that has undergone conventional processing such as cold isostatic pressing (CIP) (Figs. 11, 12). The Future of Zirconia Restorations Ongoing advances in zirconia processing technology are resulting in dramatically improved zirconia esthetics, which in turn has caused a paradigm shift in CAD/CAM all-ceramic crown & bridge restoration materials and technology. Figure 9: Lithium disilicate SEM image Figure 8: Optical transmission of common dental ceramics, 1.25 mm thick Figure 10: BruxZir Solid Zirconia SEM image 54 – www.inclusivemagazine.com –
The intrinsic physical limit for toothlike optical transmission of tetragonal zirconia is currently within reach. The theoretical optical transmission limit of tetragonal zirconia is governed by birefringence as a result of grain or crystal size. The optical transmission of tetragonal zirconia is increased exponentially as the sintered grain size is reduced (Fig. 13). 13,14 Toward this end, the research and development team at Glidewell Laboratories is among those known to be leading the effort to develop sub-50 nm crystalline sintered zirconia by developing sub-4 nm crystal zirconia starting powder. As it appears today, crown & bridge restorations with toothlike esthetics created from monolithic tetragonal zirconia are the future of dental restorations. The inherent mechanical strength and reliability of tetragonal zirconia, along with the continued development of more natural, toothlike esthetics, will make monolithic zirconia a dominant choice for the majority of crown & bridge restorations, expanding from the posterior tooth region to crowns, bridges and veneers placed in the anterior esthetic zone. IM References 1. Smith TM, Olejniczak AJ, Reid DJ, Ferrell RJ, Hublin JJ. Modern human molar enamel thickness and enamel-dentine junction shape. Arch Oral Biol. 2006 Nov;51(11):974-95. 2. Hannig M, Hannig C. Nanomaterials in preventive dentistry. Nat Nanotechnol. 2010 Aug;5(8):565-9. 3. Uskokovic V, Bertassoni LE. Nanotechnology in dental sciences: moving towards a finer way of doing dentistry. Materials. 2010;3(3):1674-1691. 4. Gutierrez-Salazar MP, Reyes-Gasga J. Microhardness and chemical composition of human tooth. Mat Res. 2003;6(3):367-73. 5. Marshall GW Jr, Marshall SJ, Kinney JH, Balooch M. The dentin substrate: structure and properties related to bonding. J Dent. 1997 Nov;25(6)441-58. 6. Brodbelt RH, O’Brien WJ, Fan PL, Frazer-Dib JG, Yu R. Translucency of human dental enamel. J Dent Res. 1981 Oct;60(10):1749-53. 7. Xiong F, Chao Y, Zhu Z. Translucency of newly extracted maxillary central incisors at nine locations. J Prosthet Dent. 2008 Jul;100(1):11-7. 8. Anusavice KJ, ed. Phillips’ Science of Dental Materials. 11th ed. St. Louis: WB Saunders; 2003. 9. Craig RG, Powers JM, eds. Restorative Dental Materials. 11th ed. St. Louis: Mosby Inc; 2002. 10. Paravina RD. Color in dentistry: is “everything we know” really so? Inside Dental Assisting. 2010 Jun;6(6) Suppl:10-19. 11. Wangness RK. Electromagnetic Fields. 2nd ed. Canada: John Wiley & Sons; 1986, pg 378. 12. Alaniz JE, Perez-Gutierrez FG, Aguilar G, Garay JE. Optical properties of transparent nanocrystalline yttria stabilized zirconia. Opt Mater. 2009 Nov;32(1):62-8. 13. Krell A, Klimke J, Hutzler T. Transparent compact ceramics: inherent physical issues. Optical Materials. 2009 Jun;31(8):1140-50. 14. Klimke J, Trunec M, Krell A. Transparent tetragonal yttria-stabilized zirconia ceramics: influence of scattering caused by birefringence. J Am Ceram Soc. 2011 Jun;94(6);1850-58. 15. Tsukuma K, Yamashita I, Kusunose T. Transparent 8 mol% Y2O3-ZrO2 (8Y) ceramics. J Am Ceram Soc. 2008 Mar;91(3):813-18. 16. Apetz R, van Bruggen MPB. Transparent alumina: a light-scattering model. J Am Ceram Soc. 2003 Mar;86(3):480-86. 17. Wood DL, Nassau K. Refractive index of cubic zirconia stabilized with yttria. Appl Opt. 1982 Aug 15;21(16):2978-81. 18. Simmons JH, Potter KS. Optical Materials. San Diego: Academic Press; 2000. Figure 11: Optical transmission of colloidal-processed BruxZir Solid Zirconia versus that of zirconia that has undergone cold isostatic pressing (CIP), 1.25 mm thick Figure 12: Optical properties of BruxZir Solid Zirconia, 1.25 mm thick Figure 13: Theoretical optical transmission versus grain size of tetragonal zirconia, 1 mm thick – Understanding Zirconia Crown Esthetics and Optical Properties – 55
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Inclusive® Restorative Driven Impl
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Contents 6 15 From Intraoral Scan t
Page 6 and 7: Contributors ■ Bradley C. Bockhor
Page 8 and 9: From Intraoral Scan to Final Custom
Page 10 and 11: Figure 4: Healing abutments at six
Page 12 and 13: Figure 15: iTero virtual scan (Alig
Page 14 and 15: Figure 25: 4-unit BruxZir Solid Zir
Page 17 and 18: Implant Q&A: An Interview with Dr.
Page 19 and 20: Not only are we maintaining the bon
Page 21: BB: If you go that route — four i
Page 24 and 25: For proper prosthetic function, zir
Page 26 and 27: On the abutment, there were three a
Page 28: Finite element analysis (FEA) provi
Page 31 and 32: Figure 1: Graph depicting usage of
Page 33 and 34: Clinical Delivery The following pro
Page 35: Delivery of a Screw-Retained BruxZi
Page 39 and 40: Figure 1: Preoperative digital trea
Page 41 and 42: Figure 8: Inclusive Mini Implant Im
Page 43 and 44: Figure 16: Wax rim delivered on cas
Page 45 and 46: Figure 26: Articulated model with b
Page 47 and 48: Implant-retained overdentures can o
Page 49 and 50: Figure 2: Sagittal MPR view with ma
Page 52 and 53: Understanding Zirconia Crown Esthet
Page 54 and 55: Spectrophotometry A spectrophotomet
Page 58: Inclusive ® Image Contest: Name Th
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