CATEGORY AUSTRALASIAN DENTIST103 CLINICAL zirconia, PMMA, hybrid composite, fiber glass) or multiple materials (Co-Cr metalceramic, titanium-composite, titaniumzirconia, polymer-composite…), the weight will differ. The higher the density of the restorative material, the heavier the patient’s mandibular prosthesis. The following table shows the densities (g/cm³) of the most commonly used materials for implant rehabilitations: X Co-Cr: 8.90 g/cm3 + dense X Zr: 5.68 g/cm3 X Titanium: 4.32g/cm3 X Ceramic: 2.50 g/cm3 X Composite: 2.00 g/cm3 X Carbon Fiber: 1.75g/cm3 X Acetal resin: 1,42 g/cm3 X PEEK: 1.32 g/cm3 X PMMA: 1.18 g/cm3 X PMMA + Graphene: 1,16 g/cm3 – dense As we can see, there is a significant difference between PMMA (a “provisional” material) and zirconia (a “definitive” material). Zirconia is over four times denser than PMMA. This means a prosthesis made of zirconia weighs nearly five times more than the same prosthesis made of PMMA. For the same patient, the prosthesis volume is identical regardless of the material used. (See Figure 2) What does the literature say about the advantages of upper zirconia rehabilitations? Biocompatible, aesthetic, hard, resistant, does not wear the antagonist… 8,9,10 Is there literature discussing the performance of monolithic zirconia upper rehabilitations considering different types of antagonists?8,11,12 They say: Rehabilitations where the antagonist is another monolithic zirconia restoration show problems such as fractures, titanium abutment decementation, or chipping of ceramic coverage. In contrast, if the antagonist is a resin (classic hybrid) or composite/hybrid composite, the upper rehabilitation remains in better condition for longer, with fewer structural issues. Why? Kinetic Energy: as the prosthesis weight increases (zirconia) and the patient’s mandibular closure speed remains the same, kinetic energy increases, impact increases, and problems increase. If the mass (weight) increases at the same closure speed, the impact and energy transmitted to the prosthesis and implants also increase. Clinical implication: If we need to rehabilitate an edentulous upper arch and have decided to use a full monolithic zirconia arch or with ceramic coverage, we must carefully consider the antagonist. If the lower arch is edentulous, do not create another implant-supported zirconia prosthesis. Instead, use slightly less rigid and less hard materials, such as composites or hybrid composites. This will help maintain both rehabilitations for a longer time. X REFERENCES: 1. Jemt T, Lekholm U, Adell R. Osseointegrated implants in the treatment of partially edentulous patients: a preliminary study on 876 consecutively placed fixtures. Int J Oral Maxillofac Implants 1989;4(3):211-217. 2. Le M, Papia E, Larsson C. The clinical success of tooth- and implant-supported zirconia-based fixed dental prostheses. A systematic review. J Oral Rehabil 2015 Jun;42(6):467-480. 3. Tuna SH, Pekmez NO, Keyf F, Canli F. The electrochemical properties of four dental casting suprastructure alloys coupled with titanium implants. J Appl Oral Sci 2009;17(5):467-475. 4. Deany IL. Recent advances in ceramics for dentistry. Crit Rev Oral Biol Med 1996;7(2):134143. 5. Geramizadeh M, Katoozian H, Amid R, Kadkhodazadeh M. Static, Dynamic, and Fatigue Finite Element Analysis of Dental Implants with Different Thread Designs. J Long Term Eff Med Implants 2016;26(4):347-355. 6. Rovira-Lastra b, Flores-Orozco EI, AyusoMontero R, Peraire M, Martinez-Gomis J. Peripheral, funcional and postural asymmetries related to the preferred chewing side in adults with natural dentition. J Oral Rehabilitation. 2016 43;279-285 7. Peck CC. Biomechanics of occlusion – implications for oral rehabilitation. J Oral Rehabilitation 2016 43; 205-214 8. Gonzalez J, Triplett RG. Complications and Clinical Considerations of the ImplantRetained Zirconia Complete-Arch Prosthesis with Various Opposing Dentitions. The International journal of oral and maxillofacial implants 2017 Jul 01,;32(4):864-869. 9. Barootchi S, Askar H, Ravidà A, GargalloAlbiol J, Travan S, Wang HL. Long-term Clinical Outcomes and Cost-Effectiveness of Full-Arch Implant-Supported Zirconia-Based and Metal-Acrylic Fixed Dental Prostheses: A Retrospective Analysis. Int J Oral Maxillofac Implants. 2020 Mar/Apr;35(2):395-405. 10. Cinquini C, Alfonsi F, Marchio V, Gallo F, Zingari F, Bolzoni AR, Romeggio S, Barone A. The Use of Zirconia for Implant-Supported Fixed Complete Dental Prostheses: A Narrative Review. Dent J (Basel. 2023 Jun 1;11(6):144. 11. Vozzo LM, Azevedo L, Campos Fernandes J, Fonseca P, Araújo F, Teixeira W, Oliveira Fernandes G, Correia A. The success and complications of complete-arch implantsupported fixed monolithic zirconia restorations: A systematic review. Prosthesis. 2023. 5(2), 425-436; 12. Carames J, Marques D, Malta Barbosa J, Moreira A, Crispim P, Chen A. Full-arch implant-supported rehabilitations: A prospective study comparing porcelainveneered zirconia to monolithic zirconia. Clin. Oral. Implant. Res. 2019 30, 68-78 Zr 1: 19.1gr PMMA 1: 4.4 gr Zr 2: 41.2 gr PMMA 2: 8.5 gr Figure 2: Two examples of prosthesis weight depending on whether it is PMMA or zirconia.
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