Silicon Nitride Dental Implants

Dental implants are another biomedical application where ceramics are making significant inroads. With the success SINTX has had with the development of the Micro-composite ceramic (MC2) silicon nitride material for spinal implants, the company is looking to broaden the application of this unique material to other medical device applications. A key area of focus for the MC2 material is for dental implants.

Silicon Nitride material has the characteristics that may be beneficial for use in dental implants

  • Biocompatibility per ISO 10993-01
  • Promote bone growth
  • Strength
  • Toughness
  • Hypoallergenic
  • Corrosion resistant
  • Non-conductive (electrical)
  • Antibacterial
  • Esthetic
  • Metal-ion Free

Dental implant material opportunity

While titanium is the “gold standard” for the fabrication of dental implants, ceramics (particularly zirconia) are making inroads. Ceramic implants are metal-free eliminating allergy concerns for patients.Silicon Nitride has been thoroughly tested to ISO 10993-01 standards1 and has been shown to be highly biocompatible. As with all ceramics, Silicon Nitride is metal free and has no corrosion, no galvanism effect, no metallic taste, no electronic disturbances. Osman and Swain compared compare titanium vs. zirconia for this application2 and concluded zirconia has many positive features but zirconia material is prone to cracking. Silicon nitride exhibits very high toughness for a ceramic.

Biomaterials that may resist bacterial colonization may offer a competitive solution in the dental implant market3. Silicon nitride material has been demonstrated in invitro experiments and animal studies to be effective against a wide variety of bacteria4,5 including P. Gingivalis6, the bacteria implicated in gingivitis. The antibacterial properties of Silicon Nitride material are most likely related to favorable surface properties such as hydrophilicity, a net negative surface charge, and the fact that Si3N4 produces silicic acid and ammonia via hydrolysis upon exposure to water7,16. It is hypothesized that interfacial production of silicic acid and ammonia promotes local osteogenesis and leads to bacterial lysis7,12.

Silicon nitride material has the ability to turn on bone-forming cells (osteoblasts) and suppress bone resorbing cells. A change to manufacturing of the material resulted in a near-200% increase in bone formation by cells exposed to silicon nitride8. This finding could have implications and may speed up bone healing, bone fusion, and implant integration into the skeleton9. Several other studies have demonstrated enhanced bone formation in invitro and in animal models10-15. These favorable results demonstrating anti-bacterial and bony ongrowth support the application and use of Si3N4 as a dental implant material.

  • SINTX has published extensive research regarding osseointegration of silicon nitride5, and superior bone healing17.
  • A 2016 paper showed that Silicon Nitride induces bacteriolysis in oral bacterial pathogens6.
  • The company has funded the investigation of silicon nitride dental implants at the Kyoto Prefectural University of Medicine, UCLA, and University of Rochester. Posters of some of this work were presented at AADR 201719 and AADR 201820.

SINTX Prototype Dental Implants


Figure 1. Silicon nitride dental implant prototypes underwent 5 million cycle dynamic loading test (per ISO 14801:2016) and met the requirements.

Figure 2. Silicon Nitride is typically a dark-colored material, but can be manufactured to be white for improved aesthetics.



Figure 3. Several different coating technologies have been developed and are transitioning from the laboratory to production.21

Several different coating technologies have been developed and are transitioning from the laboratory to production. These technologies can confer the beneficial effects of silicon nitride onto metal components, such as titanium.

Conclusion

Silicon nitride may be an ideal material for dental implants. SINTX is continuing research and development and now looking to commercialize this technology. To learn more about dental implants a great resource is the American Academy of Implant Dentistry. https://www.aaid-implant.org/dental-implants/types-of-implants-and-techniques/

References

1. Internal data on file at SINTX.

2. R. Osman and M. Swain, “A Critical Review of Dental Implant Materials with an Emphasis on Titanium versus Zirconia,” Materials (Basel)., 8 [3] 932–958 (2015).

3. Z. Badran, X. Strullou, F.J. Hughes, A. Soueidan, A. Hoornaert, and M. Ide, “Silicon Nitride (Si3N4) Implants: The Future of Dental Implantology?,” J. Oral Implantol., 43 [3] 240–244 (2017).

4. T.J. Webster, A.A. Patel, M.N. Rahaman, and B.S. Bal, “Anti-Infective and Osteointegration Properties of Silicon Nitride, Poly (Ether Ether Ketone), and Titanium Implants,” Acta Biomater., 8 [12] 4447–4454 (2012).

5. Sethi, et al. “Reduced Bacteria Colonization and Increased Bone Formation on Si3N4 Spinal Implants: An Evaluation of Bacterial Colonization on Existing Implant Materials” Presented in part as a poster at the Congress of Neurological Surgeons Annual Meeting, October 1-6, 2011, Washington, D.C.

6. G. Pezzotti, R.M. Bock, B.J. McEntire, E. Jones, M. Boffelli, W. Zhu, G. Baggio, F. Boschetto, et al., “Silicon Nitride Bioceramics Induce Chemically Driven Lysis in Porphyromonas Gingivalis,” Langmuir, 32 [12] 3024–3035 (2016).

7. R.M. Bock, B.J. McEntire, B.S. Bal, M.N. Rahaman, M. Boffelli, and G. Pezzotti, “Surface Modulation of Silicon Nitride Ceramics for Orthopaedic Applications,” Acta Biomater., 26 318–330 (2015).

8. G. Pezzotti, B.J. McEntire, R. Bock, M. Boffelli, W. Zhu, E. Vitale, L. Puppulin, T. Adachi, et al., “Silicon Nitride: A Synthetic Mineral for Vertebrate Biology,” Sci. Rep., 6 31717 (2016).

9. T.J. Webster, G.A. Skidmore, and R. Lakshminarayanan, “Increased Bone Attachment to Silicon Nitride (Si3N4) Materials Used in Interbody Fusion Cages (IBF) Compared to Polyetheretherketone (PEEK) and Titanium (Ti) Materials - An In vivo Study;” pp. 1–5 in Proc. 2012 Annu. Meet. Orthopeaedic Soc. 2012.

10. G. Pezzotti, B.J. McEntire, R.M. Bock, W. Zhu, F. Boschetto, A. Rondinella, E. Marin, Y. Marunaka, et al., “In Situ Spectroscopic Screening of Osteosarcoma Living Cells on Stoichiometry-Modulated Silicon Nitride Bioceramic Surfaces,” ACS Biomater. Sci. Eng., 2 [7] 1121–1134 (2016).

11. G. Pezzotti, E. Marin, T. Adachi, A. Rondinella, F. Boschetto, W.-L. Zhu, N. Sugano, R.M. Bock, et al., “Bioactive Silicon Nitride: A New Therapeutic Material for Osteoarthropathy,” Sci. Rep., 7 44848 (2017).9. G. Pezzotti, N. Oba, W. Zhu, E. Marin, A. Rondinella, F. Boschetto, B.J. McEntire, K. Yamamoto, et al., “Human Osteoblasts Grow Transitional Si/N Apatite in Quickly Osteointegrated Si3N4 Cervical Insert,” Acta Biomater., 64 411–420 (2017).

12. G. Pezzotti, R.M. Bock, T. Adachi, A. Rondinella, F. Boschetto, W. Zhu, E. Marin, B. McEntire, et al., “Silicon Nitride Surface Chemistry: A Potent Regulator of Mesenchymal Progenitor Cell Activity in Bone Formation,” Appl. Mater. Today, 9 82–95 (2017).

13. C.C. Guedes e Silva, B. Konig, M.J. Carbonari, M. Yoshimoto, S. Allegrini, and J.C. Bressiani, “Tissue Response Around Silicon Nitride Implants in Rabbits,” J. Biomed. Mater. Res., 84A 337–343 (2008).

14. C.C. Guedes e Silva, B. König, M.J. Carbonari, M. Yoshimoto, S. Allegrini, and J.C. Bressiani, “Bone Growth Around Silicon Nitride Implants—An Evaluation by Scanning Electron Microscopy,” Mater. Charact., 59 1339–1341 (2008).

15. M. Ishikawa, K.L.D.M. Bentley, B.J. McEntire, B.S. Bal, E.M. Schwarz, C. Xie, and E. Avenue, “Surface Topography of Silicon Nitride Affects Antimicrobial and Osseointegrative Properties of Tibial Implants in a Murine Model,” J. Biomed. Mater. Res. A, 105 [12] 3413–3421 (2017).

16. G. Pezzotti, “Silicon Nitride: A Bioceramic with a Gift”, ACS Appl. Mater. Interfaces 2019 Jul 31;11(30):26619-26636.

17. G. Pezzotti et al. “Bioactive Silicon Nitride: A New Therapeutic Material for Osteoarthropathy”, Sci. Rep., 7 44848

18. R.F.M.R. Kersten, G. Wu, B. Pouran, A.J. van der Veen, H.H. Weinans, A. de Gast, F.C. Öner, and S.M. van Gaalen, “Comparison of Polyetheretherketone versus Silicon Nitride Intervertebral Spinal Spacers in a Caprine Model,” J. Biomed. Mater. Res. Part B Appl. Biomater., 1–12 (2018).

19. Tetsuya Adachi, Toshiro Yamamoto, Bryan J. McEntire, B. Sonny Bal, Osam Mazda, Narisato Kanamura, and Giuseppe Pezzotti, “Application of Silicon Nitride Ceramics Stimulate Bone Regeneration in Dental Implants,” Poster #3783, 95th General Session and Exhibition of the IADR, San Francisco, CA, USA, (March 2017).

20. Tetsuya Adachi, Satoshi Horiguchi, Alfredo Rondinella, Francesco Boschetto, Elia Marin, Toshiro Yamamoto, Bryan McEntire, Osam Mazda, Narisato Kanamura, and Narisato Kanamura, “Osteoinductive Potential of Silicon Nitride Ceramics Versus Mesenchymal Stem Cells,” Poster 0658, 47th Annual Meeting of the AADR, Fort Lauderdale, FL, USA (Mar. 22, 2018).

21. G. Pezzotti, E. Marin, M. Zanocco, F. Boschetto, W. Zhu, B.J. McEntire, B.S. Bal, T. Adachi, et al., “Osteogenic Enhancement of Zirconia-Toughened Alumina with Silicon Nitride and Bioglass®,” Ceramics, 2 554–567 (2019).