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 MC2 silicon nitride material for spinal implants, the company is now looking to broaden the application of this unique material to other applications inside the body. A key area of focus for the MC2 material is for dental implants and dental surgery.

Requirements for dental implants are similar, but even more demanding than those for spinal implants. These requirements are:

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

Peri-implantitis resistance

Infections associated with dental implants – Peri-implantitis, can reduce the success rate of dental implants,[1] particularly in patients predisposed to periodontal disease.[2] Dental peri-implantitis, whose prevalence has recently been reported as high as 37% on a per patient basis [3,4], remains a persistent and common postsurgical complication that often requires subsequent treatment or revision.

Biomaterials that resist bacterial colonization may be the solution. SINTX’s silicon nitride (Si3N4) is a non-oxide ceramic with proven efficacy in spinal fusion, excellent osseointegration, and inherent resistance to bacterial biofilm formation. The material is effective against a wide variety of orthopedic bacteria [5-8], and against P. Gingivalis [9], the bacteria implicated in gingivitis. SINTX has conducted research on the use of Si3N4 to evaluate bacteriostatic outcomes for both single- and commensal-strain testing. Accumulation of pathogenic bacteria at the implant site is a major component of its complex etiology.

Antibacterial properties 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 water[10]. It is hypothesized that interfacial production of silicic acid and ammonia promotes local osteogenesis and leads to bacterial lysis.

Dental implant material opportunity

While titanium is the “gold standard” for the fabrication of oral implants, ceramics (particularly zirconia) are making inroads. In a recent review by Osman and Swain, they compare titanium vs. zirconia for this application. [11] While zirconia has many positive features, such as being metal-free for patients with allergic reactions, the material is prone to cracking. Silicon nitride exhibits very high toughness for a ceramic and provides antibacterial properties. In addition to favorable surface properties such as hydrophilicity and a robust net negative charge, Si3N4 produces silicic acid and ammonia via hydrolysis upon exposure to water. [10] It has been hypothesized that interfacial production of silicic acid and ammonia promotes local osteogenesis and bacterial lysis.

Si3N4 monoliths and coatings performed well relative to Ti-alloy and 3Y-ZrO2 in terms of resisting bacterial colonization, enhancing osteogenic activity, and osseointegration. Si3N4 monoliths also exhibited radio translucency using conventional radiography. These favorable results support the application and use of Si3N4 as a dental implant material.

  • SINTX has published extensive research regarding osseointegration of silicon nitride [12], and superior bone healing [13].
  • A 2016 paper showed that Silicon Nitride induces bacteriolysis in oral bacterial pathogens [6].
  • 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 2016 and AADR 2017.

SINTX Dental Implants


Figure 1. Prototype silicon nitride dental implants have successfully completed the 5 million cycle dynamic loading test proscribed in ISO 14801.

SINTX can manufacture monolithic silicon nitride implants or utilize coating technologies to surface functionalize metals, ceramics, and polymers with silicon nitride. Regardless of the approach, the end product will be anti-bacterial with enhanced osseointegration.

SINTX has completed two 510(k) pre-submissions on ceramic dental implants to the U.S. FDA.


Figure 2. Demonstration of ability to adjust color of silicon nitride.

Standard silicon nitride has a dark color but it can be whitened through changes in the process.


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

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 appears to be an ideal material for dental implants particularly in light of the issues associated with periimplantitis. SINTX in 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.

References

1. G.E. Salvi, R. Cosgarea, and A. Sculean, “Prevalence and Mechanisms of Peri-implant Diseases,” J. Dent. Res., 96 [1] 31–37 (2017).

2. F. Sgolastra, A. Petrucci, M. Severino, R. Gatto, and A. Monaco, “Periodontitis, Implant Loss and PeriImplantitis: A Meta-Analysis,” Clin. Oral Implants Res., 26 [4] e8–e16 (2015).

3. B. Al-Nawas, P.W. Kämmerer, T. Morbach, C. Ladwein, J. Wegener, and W. Wagner, “Ten-Year Retrospective Follow-Up Study of the TiOblastTM Dental Implant,” Clin. Implant Dent. Relat. Res., 14 [1] 127–134 (2012).

4. D. Buser, S.F.M. Janner, J.G. Wittneben, U. Brägger, C.A. Ramseier, and G.E. Salvi, “10-Year Survival and Success Rates of 511 Titanium Implants with a Sandblasted and Acid-Etched Surface: A Retrospective Study in 303 Partially Edentulous Patients,” Clin. Implant Dent. Relat. Res., 14 [6] 839–851 (2012).

5. 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).

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. 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).

8. 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).

9. 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).

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

11. 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).

12. 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.

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

14. https://www.aaid-implant.org/dental-implants/types-of-implants-and-techniques/