Hardness and Density of Conventional and Monolithic Zirconia after Sintering

ORIGINAL ARTICLE
Genc Rukiqi, Kujtim Shala, Teuta Pustina, Fisnik Aliaj, Erik Musliu, Mirjet Lushaj

 
For citation: Rukiqi G, Shala K, Pustina T, Aliaj F, Musliu E, Lushaj M. Hardness and Density of Conventional and Monolithic Zirconia after Sintering. International Journal of Biomedicine. 2024;14(3):503-509. doi:10.21103/Article14(3)_OA19
 
Originally published September 6, 2024

Abstract: 

Background: Zirconia (zirconium dioxide, ZrO2) has optimum properties for dental use. Its main advantages include biocompatibility, biomechanical stability, and high fracture resistance. This in vitro study aimed to determine and compare the hardness and density of conventional and monolithic zirconium after the laboratory sintering process.
Methods and Results: This experimental-comparative study was carried out on processed samples of zirconia blocks, determining their mechanical properties and comparing them between different zirconia materials. Conventional zirconia blocks (from Dentsply Sirona Cercon HT and Orodent Zirconia HT) and monolithic zirconium blocks (from Dentsply Sirona Cercon ML and Orodent Zirconia Thor) were processed to produce 80 molar crowns. Samples were divided into two groups: Sirona[S]–Orodent[O]/Conventional [C] group (n=40) and Sirona[S]–Orodent[O]/Monolithic [M] group (n=40). Sirona samples were divided into Sirona-Conventional (SC) subgroup (n=20) and Sirona-Monolithic (SM) subgroup (n=20); Orodent samples were divided into Orodent-Conventional (OC) subgroup (n=20) and Orodent-Monolithic (OM) subgroup (n=20). Samples were formed with an occlusal thickness of 2mm and were sintered at 1450 °C for 2 hours. Hardness expressed in Vickers Hardness Number (VHN) was performed using a microhardness tester (Model HV-1000DT), and density determination (g/cm3) was performed with a pycnometer. The results showed no significant differences (P=0.137) between the Sirona manufacturer's SC and SM subgroups. The subgroups of the Orodent manufacturer showed statistically significant differences: the OM subgroup had a higher hardness value than the OS subgroup (1654.95±140.731 VHN versus 1526.45±149.011 VHN, P=0.008). Among the four studied subgroups, the highest hardness was in the OM subgroup (1654.95±140.731 VHN) compared to the SC subgroup (1595.55±147.790 VHN), OC subgroup (1526.45±149.011 VHN), and SM subgroup (1525.95±142.081 VHN) (P=0.016). Density in the subgroups SC, OC, SM, and OM was 6.246 g/cm3, 6.081g/cm3, 6.217 g/cm3, and 6.187 g/cm3, respectively, without statistically significant differences (P>0.05).
Conclusion: The findings highlight the suitability of both zirconia materials from Dentsply Sirona and Orodent manufacturers for dental restorations, with Orodent monolithic zirconia offering potential advantages in terms of hardness.

Keywords: 
conventional zirconia • density • hardness • monolithic zirconia • sintering
References: 
  1. Bona AD, Pecho OE, Alessandretti R. Zirconia as a Dental Biomaterial. Materials (Basel). 2015 Aug 4;8(8):4978-4991. doi: 10.3390/ma8084978. PMID: 28793485; PMCID: PMC5455532.
  2. Yang L, Chen B, Meng H, Zhang H, He F, Xie H, Chen C. Bond durability when applying phosphate ester monomer-containing primers vs. self-adhesive resin cements to zirconia: Evaluation after different aging conditions. J Prosthodont Res. 2020 Apr;64(2):193-201. doi: 10.1016/j.jpor.2019.06.008. Epub 2019 Nov 2. PMID: 31690540.
  3. Rashid H. The effect of surface roughness on ceramics used in dentistry: A review of literature. Eur J Dent. 2014 Oct;8(4):571-579. doi: 10.4103/1305-7456.143646. PMID: 25512743; PMCID: PMC4253118.
  4. Chacun D, Lafon A, Courtois N, Reveron H, Chevalier J, Margossian P, Alves A, Gritsch K, Grosgogeat B. Histologic and histomorphometric evaluation of new zirconia-based ceramic dental implants: A preclinical study in dogs. Dent Mater. 2021 Sep;37(9):1377-1389. doi: 10.1016/j.dental.2021.06.010. Epub 2021 Jul 5. PMID: 34238605.
  5. Almohammed SN, Alshorman B, Abu-Naba’a LA. Mechanical properties of five esthetic ceramic materials used for monolithic restorations: A comparative in vitro study. Ceramics.2023;6(2). doi: 10.3390/ceramics6020061.
  6. Della Bonna A. Bonding to ceramics: Scientific evidences for clinical dentistry. UK: Scion Publishing, 2009.
  7. Nistor L, Grădinaru M, Rîcă R, Mărășescu P, Stan M, Manolea H, Ionescu A, Moraru I. Zirconia Use in Dentistry - Manufacturing and Properties. Curr Health Sci J. 2019 Jan-Mar;45(1):28-35. doi: 10.12865/CHSJ.45.01.03. Epub 2019 Mar 31. PMID: 31297259; PMCID: PMC6592671.
  8. Alammar, A., & Blatz, M. B. The resin bond to high-translucent zirconia- Alammar A, Blatz MB. The resin bond to high-translucent zirconia-A systematic review. J Esthet Restor Dent. 2022 Jan;34(1):117-135. doi: 10.1111/jerd.12876. Epub 2022 Jan 24. PMID: 35072329.
  9. Kim HK. Optical and Mechanical Properties of Highly Translucent Dental Zirconia. Materials (Basel). 2020 Jul 31;13(15):3395. doi: 10.3390/ma13153395. PMID: 32751942; PMCID: PMC7435650.
  10. Lerner H, Nagy K, Pranno N, Zarone F, Admakin O, Mangano F. Trueness and precision of 3D-printed versus milled monolithic zirconia crowns: An in vitro study. J Dent. 2021 Oct;113:103792. doi: 10.1016/j.jdent.2021.103792. Epub 2021 Sep 2. PMID: 34481929.
  11. Nakamura K, Harada A, Inagaki R, Kanno T, Niwano Y, Milleding P, Örtengren U. Fracture resistance of monolithic zirconia molar crowns with reduced thickness. Acta Odontol Scand. 2015;73(8):602-8. doi: 10.3109/00016357.2015.1007479. Epub 2015 Jan 30. PMID: 25635734.
  12. Bruhnke M, Awwad Y, Müller WD, Beuer F, Schmidt F. Mechanical Properties of New Generations of Monolithic, Multi-Layered Zirconia. Materials (Basel). 2022 Dec 28;16(1):276. doi: 10.3390/ma16010276. PMID: 36614613; PMCID: PMC9822212.
  13.  Øilo M, Kvam K, Tibballs JE, Gjerdet NR. Clinically relevant fracture testing of all-ceramic crowns. Dent Mater. 2013 Aug;29(8):815-23. doi: 10.1016/j.dental.2013.04.026. Epub 2013 Jun 6. PMID: 23746750.
  14. Ispas A, Iosif L, Murariu-Măgureanu C, Craciun A, Constantiniuc M. Zirconia in dental medicine: A brief overview of its properties and processing techniques. Human and Veterinary Medicine. 2021;13(1):33–39.
  15. Caglar I, Ates SM, Yesil Duymus Z. The effect of various polishing systems on surface roughness and phase transformation of monolithic zirconia. J Adv Prosthodont. 2018 Apr;10(2):132-137. doi: 10.4047/jap.2018.10.2.132. Epub 2018 Apr 18. PMID: 29713434; PMCID: PMC5917105.
  16. Edwards Rezende CE, Sanches Borges AF, Macedo RM, Rubo JH, Griggs JA. Dimensional changes from the sintering process and fit of Y-TZP copings: Micro-CT analysis. Dent Mater. 2017 Nov;33(11):e405-e413. doi: 10.1016/j.dental.2017.08.191. Epub 2017 Sep 19. PMID: 28939084.
  17. Kim MJ, Ahn JS, Kim JH, Kim HY, Kim WC. Effects of the sintering conditions of dental zirconia ceramics on the grain size and translucency. J Adv Prosthodont. 2013 May;5(2):161-6. doi: 10.4047/jap.2013.5.2.161. Epub 2013 May 30. PMID: 23755342; PMCID: PMC3675289.
  18. Luthardt RG, Holzhüter M, Sandkuhl O, Herold V, Schnapp JD, Kuhlisch E, Walter M. Reliability and properties of ground Y-TZP-zirconia ceramics. J Dent Res. 2002 Jul;81(7):487-91. doi: 10.1177/154405910208100711. PMID: 12161462..
  19. Jang GW, Kım HS, Choe HC, Son MK. Fracture strength and mechanism of dental ceramic crown with zirconia thickness. Procedia Eng. 2011;10:1556–60. doi: 10.1016/j.proeng.2011.04.260.
  20. Stawarczyk B, Ozcan M, Hallmann L, Ender A, Mehl A, Hämmerlet CH. The effect of zirconia sintering temperature on flexural strength, grain size, and contrast ratio. Clin Oral Investig. 2013 Jan;17(1):269-74. doi: 10.1007/s00784-012-0692-6. Epub 2012 Feb 23. PMID: 22358379.
  21. Öztürk C, Can G. Effect of sintering parameters on the mechanical properties of monolithic zirconia. J Dent Res Dent Clin Dent Prospects. 2019 Fall;13(4):247-252. doi: 10.15171/joddd.2019.038. PMID: 32190207; PMCID: PMC7072090.
  22. Poole SF, Rocha Pereira GK, Moris ICM, Marques AG, Ribeiro RF,  Gomes EA. Physical properties of conventional and monolithic yttria-zirconia materials after low-temperature degradation. Ceram Int. 2019; 45(16), 21038–21043. doi: 10.1016/j.ceramint.2019.07.012.
  23. Candido LM, Miotto LN, Fais L, Cesar PF, Pinelli L. Mechanical and Surface Properties of Monolithic Zirconia. Oper Dent. 2018 May/Jun;43(3):E119-E128. doi: 10.2341/17-019-L. PMID: 29676981.
  24. Amat NF, Muchtar A, Amril MS, Ghazali MJ, Yahaya N. Effect of sintering temperature on the aging resistance and mechanical properties of monolithic zirconia. Journal of Materials Research and Technology; 2019:8(1):1092–1101. doi: 10.1016/j.jmrt.2018.07.017.
  25. Kondo T, Muta H, Kurosaki K, Kargl F, Yamaji A, Furuya M, Ohishi Y. Density and viscosity of liquid ZrO2 measured by aerodynamic levitation technique. Heliyon. 2019 Jul 22;5(7):e02049. doi: 10.1016/j.heliyon.2019.e02049. PMID: 31372532; PMCID: PMC6658727.PMC6658727.
  26. Al-Azzawi AKJK,  Al Jorani LEA, Fouad RI. Evaluation of the effect of different glazing brands on hardness of monolithic zirconia fabricated by CAD/CAM technique. Tikrit Journal for Dental Sciences. 2023;11(1):57-68
  27. Hashim AR, Mansoor N S. Effect of Different Surface Treatments on Surface Roughness and Vickers Micro-Hardness of Feldspathic Porcelain: An In Vitro Study. Mustansiria Dental Journal. 2024;17(1):36–50. doi: 10.32828/mdj.v17i1.1014
  28. Vagkopoulou T, Koutayas SO, Koidis P, Strub JR. Zirconia in dentistry: Part 1. Discovering the nature of an upcoming bioceramic. Eur J Esthet Dent. 2009 Summer;4(2):130-51. PMID: 19655651.
  29. Roy ME, Whiteside LA, Katerberg BJ, Steiger JA. Phase transformation, roughness, and microhardness of artificially aged yttria- and magnesia-stabilized zirconia femoral heads. J Biomed Mater Res A. 2007 Dec 15;83(4):1096-1102. doi: 10.1002/jbm.a.31438. PMID: 17584902.
  30. Kawai Y, Uo M, Wang Y, Kono S, Ohnuki S, Watari F. Phase transformation of zirconia ceramics by hydrothermal degradation. Dent Mater J. 2011;30(3):286-92. doi: 10.4012/dmj.2010-175. Epub 2011 May 20. PMID: 21597215.
  31. Catledge SA, Cook M, Vohra YK, Santos EM, McClenny MD, David Moore K. Surface crystalline phases and nanoindentation hardness of explanted zirconia femoral heads. J Mater Sci Mater Med. 2003 Oct;14(10):863-7. doi: 10.1023/a:1025678525474. PMID: 15348523.
  32. Ximinis E, Dionysopoulos D, Papadopoulos C, Tournavitis A, Konstantinidis A, Naka O. Effect of tooth brushing simulation on the surface properties of various resin-matrix computer-aided design/computer-aided manufacturing ceramics. J Esthet Restor Dent. 2023 Sep;35(6):937-946. doi: 10.1111/jerd.13043. Epub 2023 Apr 13. PMID: 37052301.
  33. Lee JH, Kim SH, Han JS, Yeo IL, Yoon HI. Optical and Surface Properties of Monolithic Zirconia after Simulated Toothbrushing. Materials (Basel). 2019 Apr 10;12(7):1158. doi: 10.3390/ma12071158. PMID: 30974750; PMCID: PMC6480371.
  34. Candido L, Fais LM, Pinelli L. Surface roughness and hardness of yttria stabilized zirconia (Y-TZP) after 10 years of simulated brushing. Rev Odontol UNESP. 2014. 43(6):379-383. doi: 10.1590/1807-2577.1049
  35. Shetty SK, Varghese FM, Zahid M, Dandekeri S, Feroz F. Effect of Different Sintering Cycles on the Surface Hardness of Full Contour Monolithic Zirconia – An In Vitro Comparative Study. J Evolution Med Dent Sci. 2021;10(28):2089–2093. doi: 10.14260/jemds/2021/427.

Download Article
Received May 19, 2024.
Accepted August 29, 2024.
©2024 International Medical Research and Development Corporation.