Precision engineering for clinical predictability
Predictability of clinical outcomes is crucial for both patients and clinicians. This is also why Nobel Biocare invests in science, quality assurance, and clinical evaluation of our innovations. Case in point: the Nobel Biocare N1™ implant system. The neck of the Nobel Biocare N1 Implant has a trioval shape, and thus the implant-abutment connection, unlike other systems in the market, is also trioval. This design was introduced by our research and development team, based on consultation with clinical experts, to bring the best of both worlds together: better sealing and strength of the Nobel Biocare conical connection,1 combined with the ease of use of a self-aligning trilobe connection.
Strength in focus
Together with the Zürich University of Applied Science, Nobel Biocare Biomechanics lab in Zürich tested the trioval conical connection (TCC) concept,2 to ensure its quality and reliability in demanding clinical situations. In these tests, our clinically proven internal conical connection (CC) was selected as the control group, because it shows excellent stability, fatigue performance, and sealing1,3. We evaluated the fatigue strength according to ISO 14801,4 and in two different scenarios simulating:
- Single-unit crown indication (n = 24)
- Wide-span bridges (n = 48)
Long-term chewing was simulated by 2 million cycles of loading in a saline solution. Fatigue limits (FL) and median fatigue limits (MFL) were calculated for all test groups.
The fatigue limit of the trioval conical connection (TCC) was superior in all scenarios: 13% higher compared to CC in the single unit scenario, while in the bridge setup, it outperformed the CC by 17% with two straight implants and by 31% when one implant was angulated.
The median fatigue limits were also significantly higher for the TCC in all experimental setups compared to the CC (p<0.001).
Median fatigue limit of TCC and CC (normalized to CC) under different experimental setups. Median fatigue limits were significantly higher (*) for TCC under all conditions.
Restorative flexibility
N1 Implants can be restored at implant and base levels. At the implant level, the Universal Abutment, Esthetic Abutment, or customized abutment is fixed to the implant using the clinical screw.
The base level restoration applies the “one-abutment one-time concept”, by using the Nobel Biocare N1 Base.5,6 The N1 Base is left in situ throughout the restorative workflow and for the entire lifetime of the restoration. This preserves the epithelial and connective tissue structure and minimizes the number of soft tissue disruptions in the periodontally critical area. In this setting, after seating and lining up with the implant, the N1 Base is tightened to the implant with the clinical screw, to a maximum torque of 20 Ncm, using the Screwdriver N1 Base. The N1 Base in turn can be restored using a Universal Abutment, Esthetic Abutment, or NobelProcera Zirconia N1 Base. All these restorative parts use Prosthetic Screw N1 Base which should be tightened using the Omnigrip Mini Screwdriver, again at the maximum torque of 20 Ncm.
What does a different screw-tightening torque mean?
The N1 clinical and prosthetic screws are both tightened to a maximum torque of 20 Ncm. This innovation allows restorative clinicians to immediately provisionalize the implant as soon as it has reached the final insertion torque of 20 Ncm.
Does a lower screw torque mean higher risk of screw loosening? Not at all. We studied that in our biomechanics lab in Zurich.7
Systems were assembled using tightening torques of 20 Ncm. The implants were clamped at 3 mm below bone level and sinusoidally loaded at 30° angulation in air and at room temperature for 10, 100, 1000, or 10,000 cycles to the maximum load of 100 N, 200 N, and 300 N (ISO 14801 fixture, n=3 per group). Subsequently, samples were disassembled, and the release torques of the prosthetic screws were measured. We also compared the results to the release torques of control samples, which were not subjected to cyclic loading.
Independent of the applied load and the number of cycles, the release torque of the Prosthetic Screw N1 Base remained stable and comparable to that of the control group (18.5±0.4 Ncm), suggesting that screw loosening of the N1 system prosthetic screw is very unlikely in a clinical setting.
Why is screw loosening important? It is a common complication, and while in most cases it requires only retightening of the screw, it can also lead to a catastrophic failure such as screw, abutment or even implant fracture. Using appropriate and precisely engineered materials and tools can significantly mitigate the risk of this complication.
“With N1, Nobel Biocare offers a system that lets me treat almost any indication with a very small number of additional parts. The trioval connection allows an easy and safe positioning of prosthetic elements. Considering the low torque of 20 Ncm even for single-unit restorations, screw loosening has been very rare: I have only seen it twice in 3 years.”
Continuous improvement
Nobel Biocare invests in high-quality research and development for solutions that bring continuous improvement.
Today, the 2-piece N1 abutment (Universal Abutments trioval conical connection (TCC) and N1 Base RP) outperforms the older systems, such as Esthetic Abutment CC and Universal Base External Hex, which have been in clinical use for many years and are proven by various tests and standards,8 to fulfill our mission of continuous improvement, and to increase clinical productivity, while safety and predictability stay the main focus.
Higher fatigue limit of N1 universal abutment and N1 Base (two-piece), and N1 Universal Abutment (one-piece), than the clinically proven Universal Abutment Ex Hex and Esthetic Abutment CC which have been in clinical use since the 2000s
More to explore
For more information, check the Nobel Biocare N1 system webpage.
References
1. Zipprich H, Miatke S, Hmaidouch R, et al. A New Experimental Design for Bacterial Microleakage Investigation at the Implant-Abutment Interface: An In Vitro Study. Int J Oral Maxillofac Implants. 2016;31(1):37-44
2. Velikov S, Fabech J, Heuberger P. Mechanical properties of a novel conical connection. Volume 30, Issue 19 Special Issue: 28th Annual Scientific Meeting of the European Association for Osseointegration, 26‐28 September 2019. Page 216
3. Schmitt CM, Nogueira-Filho G, Tenenbaum HC, et al. Performance of conical abutment (Morse Taper) connection implants: a systematic review. Journal of Biomedical Materials Research. Part A. 2014;102(2):552-574
4. ISO 14801:2016 Dentistry – Implants – Dynamic loading test for endosseous dental implants, https://www.iso.org/standard/61997.html
5. Wang QQ, Dai R, Cao CY, et al. One-time versus repeated abutment connection for platform-switched implant: A systematic review and meta-analysis. PLoS One 2017;12(10):e0186385
6. Tallarico M, Caneva M, Meloni SM, et al. Definitive Abutments Placed at Implant Insertion and Never Removed: Is It an Effective Approach? A Systematic Review and Meta-Analysis of Randomized Controlled Trials. J Oral Maxillofac Surg 2018;76(2):316-24
7. Zemp J, Dobler G, Fabech J, et al. Prosthetic Screw Performance Evaluation of the Nobel Biocare N1 Base. IADR abstract and presentation June 2022
8. Data on file