Leading clinicians present research observations on Bone Level Implant

At two of implant dentistry's most prestigious scientific congresses, the 16th Annual Scientific Meeting of the European Association for Osseointegration (EAO) in Barcelona and the 93rd Annual Meeting of the American Academy of Periodontology (AAP) in Washington, D.C., 11 internationally renowned clinicians and researchers presented the latest findings in an extensive research program assessing the Straumann® Bone Level Implant, the new generation bone level implant that Straumann has launched in Europe, North America, Australia and New Zealand.

Scientific pedigree with well documented design elements

According to the company, the Straumann Bone Level Implant combines new and innovative concepts with well-documented design elements such as the unique SLActive surface. Backed by a wealth of completed clinical and pre-clinical studies, together with a large ongoing clinical program, this is one of the best investigated implant surfaces on the market.^1-15 Another scientifically proven and well-documented design element is the implant thread, which comes from Straumann's Tapered Effect Implant. Launched in 2002, this has been documented in several large studies, including multicenter trials, which have shown the implant's outstanding success and survival rates in clinically challenging situations.^16-20

To test the overall design and performance of the new bone level implant, a preclinical and clinical research program was put together by Straumann in close collaboration with internationally renowned experts.

Biomechanical/property tests

The program started with a range of exacting biomechanical tests, the outcomes of which were presented by Dr Stephen Chen²¹ at the EAO and Dr Frank Higginbottom²² at the AAP.

Precision conical connection

As the microgap between an implant and the abutment is an important element in bone control design, the connection was subjected to rigorous examination. The results demonstrated the very high manufacturing precision of the conical connection, which is used in preference to a flat-top design in order to achieve a tighter seal against bacteria and to minimize micromovements. Scanning electron microscopy showed the microgap to be just 0.6 ± 0.3μm.

Biomechanical stability

Extensive mechanical testing was performed to assess ultimate strength and to simulate the effects of prolonged and intense chewing under extreme conditions (fatigue strength). The results show that both the fatigue and ultimate strength of all Straumann Bone Level Implants (diameters of 3.3mm, 4.1mm and 4.8mm) are well above the average of tested competitors. In fact, Straumann Bone Level Implants showed higher ultimate and fatigue strengths than larger diameter implants made by leading competitors.²³

Preclinical studies

The preclinical program was summarized by Dr Stephen Chen at the EAO and Prof. David Cochran²⁴ together with Prof. Guiseppe Cardaropoli²⁵ at the AAP. The latest results of the various studies show excellent and predictable bone preservation with the Straumann Bone Level Implant.

Crestal bone preservation²⁶

The aim of the first preclinical trial, which was conducted by Prof. Cochran's group and Dr Ronald Jung,²⁷ was to evaluate radiographically and histologically the crestal bone changes around the Straumann Bone Level Implant placed either submerged or non-submerged at three different levels relative to the bone crest (1mm above, 1mm below, and level with bone crest). In total 60 implants were placed.

Excellent and predictable bone preservation was reported 6 months after implant loading. Radiography revealed no or only very little bone loss (between zero and 0.5mm relative to the implant-abutment connection in each case). Remarkably, 75% of the implants placed 1mm above bone crest showed positive bone gain after 6 months. Histological specimens were prepared after six months and show excellent osseointegration, confirming the results from the x-ray examinations.²⁸

At the AAP, Professor Cochran noted: "The Bone Level Implant incorporates an abutment diameter that is smaller than the implant diameter and fits inside the implant with a conical connection. On the outside of the implant is the highly osteoconductive SLActive surface. Our pre-clinical study evaluated the reaction of the crestal bone to the implant placed at different levels in relationship to the bone margin. Impressively the bone after 6 months of loading was located in some instances on the bevel of the implant. Additionally, the epithelium and the connective tissue in these cases were located on the abutment surface. This is a remarkable finding and one I have never seen before when the implant configuration includes implant and abutment diameters that are matched resulting in a butt joint connection".

Inter-proximal bone preserved

The aim of a second preclinical study²⁹ to investigate the bone and soft tissue changes at two adjacent implants that were set either 3 or 4mm apart from each other. The study, which involved 72 implants, recorded a mean radiographic bone gain of 0.2 ± 0.6mm in the 3mm interproximal distance group (a situation in which crestal bone is difficult to maintain). In the 4mm inter-proximal distance group, the mean radiographic bone gain was 0.2 ± 0.3mm. The results thus revealed only minimal bone changes and no statistically significant differences between the 3mm and 4mm groups. The radiographic results have been confirmed by histology and micro CT data. Further investigations are underway to evaluate what happens when the distance between the implants is reduced further to 2mm.

Clinical studies

Following the promising pre-clinical results, a broad clinical program was started including a prospective pilot study, a multicenter study and a non-interventional field trial. To date, some 1500 implants have been clinically documented in over 800 patients by more than 130 centres around the world.

Pilot clinical study

The pilot study³⁰ was conducted to assess the performance, bone level preservation and aesthetic outcome of the new implant in single-tooth gaps in the upper front region of the mouth. Data from the study were presented at the EAO by Prof. Urs Belser.³¹ In total, 20 patients were treated and have been followed for a minimum of 12 months after loading of the implant. Straumann Bone Level Implant was shown to offer predictable osseointegration and crestal bone preservation. Three implants showed a change in bone level of more than 0.3 mm, and only one implant demonstrated slight (approximately 0.9 mm) bone loss at 6 months. However, the situation in this particular case had improved at 12 months. No soft tissue complications (such as gingival recession) have been reported, i.e. stable periimplant soft tissues have been observed.

Controlled clinical study

A randomized, controlled clinical study is also underway and was presented in Barcelona by the principal investigator Prof. Christoph Hämmerle.³² It compares submucosal with transmucosal placement of Straumann Bone Level Implants in single tooth gaps. Interproximal bone levels, soft tissue parameters and the influence of the healing protocol on aesthetic outcomes are also being evaluated.

The study involves 134 patients in 12 centres in 7 countries. To date, more than 110 implants have been placed, with one loss reported. No adverse events and no major complications have been reported. As the study is still ongoing, the results will become available in due course. However, the feedback from study centres so far is very positive.

Non-interventional clinical study

A non-interventional study³³ was set up to document the success and survival rates of Straumann Bone Level implants in everyday practice in all approved indications for up to 3 years after implant placement. 'Non-interventional' means that clinicians are free to include all indications and apply their preferred treatment approach with minimal intervention by the study organizer. The patient-dentist interaction is therefore not influenced by protocol or other interventions. As a result, the study provides a realistic picture of actual patient pools and treatment protocols. It also provides insight into how the implant is used and how it performs in clinical situations, with the intention of validating the data from controlled trials.

Professor Juan Blanco-Carrion³⁴ presented data from this study at the EAO. To date, 118 international centres have placed and documented more than 1370 implants in 729 patients. Of these, just 5 implant losses have been reported, indicating a very high success rate. Over 440 implants have been observed for more than 6 months, the timeframe in which early implant failure in general is most likely to occur. Up to now, no major adverse events or complications have been reported. Overall, the data show that clinicians perceive the new implant as an excellent solution for a wide range of indications.

Summary

In general, the investigators have highlighted the following attributes:

• Reliability: the implant respects all 5 key biological principles and is thus designed to optimize crestal bone preservation (Bone Control Design™). Scientific data on the Straumann Bone Level Implant confirm the positive effect of this concept;
• Ease of handling: here a number of features were noted: ,or example the fact that the CrossFit™ connection gives the restorative doctor confidence that the abutment has seated correctly, and the fact that the same instrument kit can be used. The latter benefit translates into time savings for the practice staff with regard to cleaning and sorting; and
• Increased versatility and flexibility of the new implant line extension: the Straumann Dental Implant system now offers the dental professional unmatched flexibility, as all Straumann's implants use one instrument kit and the same procedures.

Confidence at every level

The combination of its design features, together with the current body of scientific and clinical data, provides dental professionals with a completely new level of confidence at bone level. This will be further strengthened through the addition of new data as the ongoing clinical program progresses.

Straumann is the only company that offers a full range of tissue- and bonelevel implant options combined with state-of-the-art CAD/CAM prosthetics and regenerative solutions.

References

1. de Wild M. Superhydrophilic SLActive implants. Straumann document 151.527/d and 151.527/e.
2. Schwarz F, Sculean A, Wieland M, Horn N, Nuesry E, Bube C, Becker J. Effects of hydrophilicity and microtopography on titanium implant surfaces on supragingival plaque biofilm formation. A pilot study. Mund Kiefer Gesichschir 2007; (Epub ahead of print).
3. Rausch-Fan X, Qu Z, Wieland M, Matejka M, Schedle A. Differentiation and cytokine synthesis of human alveolar osteoblasts compared to osteoblast-like cells (MG63) in response to titanium surfaces. Dent Mater 2007; Epub ahead of print..
4. Qu Z, Rausch-Fan X, Wieland M, Matejka M, Schedle A. The initial attachment and subsequent behavior regulation of osteoblasts by dental implant surface modification. J Biomed Mater Res A 2007; 82: 658-668.
5. Schwarz F, Herten M, Sager M, Wieland M, Dard M, Becker J. Bone regeneration in dehiscence-type defects at chemically modified (SLActive) and conventional SLA titanium implants: a pilot study in dogs. J Clin Periodontol 2007; 34: 78-86.
6. Schwarz F, Herten M, Sager M, Wieland M, Dard M, Becker J. Histological and immunohistochemical analysis of initial and early osseous integration at chemically modified and conventional SLA titanium implants: preliminary results of a pilot study in dogs. Clin Oral Implants Res 2007; 18: 481-488.
7. Schwarz F, Herten M, Sager M, Wieland M, Dard M, Becker J. Histological and immunohistochemical analysis of initial and early subepithelial connective tissue attachment at chemically modified and conventional SLA titanium implants. A pilot study in dogs. Clin Oral Investig 2007; 11: 245-255.
8. Zhao G, Schwartz Z, Wieland M, Rupp F, Geis-Gerstorfer J, Cochran D, Boyan B. High surface energy enhances cell response to titanium substrate microstructure. J Biomed Mater Res A 2005; 74: 49-58.
9. Buser D, Broggini N, Wieland M, Schenk R, Denzer A, Cochran D, Hoffmann B, Lussi A, Steinemann S. Enhanced bone apposition to a chemically modified SLA titanium surface. J Dent Res 2004; 83: 529-533.
10. Ferguson S, Broggini N, Wieland M, de Wild M, Rupp F, Geis-Gerstorfer J, Cochran D, Buser D. Biomechanical evaluation of the interfacial strength of a chemically modified sandblasted and acid-etched titanium surface. J Biomed Mater Res A 2006; 78: 291-197.
11. Rupp F, Scheideler L, Olshanka N, de Wild M, Wieland M, Geis-Gerstorfer J. Enhancing surface free energy and hydrophilicity through chemical modification of microstructured titanium implant surfaces. J Biomed Mater Res A 2006; 76: 323-334.
12. Scheideler L, Rupp F, Wieland M, Geis-Gerstorfer J. Storage conditions of titanium implants influence molecular and cellular interactions. 83rd International Session and Exhibition of the International Association for Dental Research, Baltimore, MD, USA, 9-12 March 2005; Poster #870.
13. Bornstein M, Valderrama P, Jones A, Wilson T, Seibl R, Cochran D. Bone apposition around two different sand-blasted and acid-etched titanium implant surfaces. A histomorphometric study in canine mandibles. Clin Oral Implants Res 2007 (In press).
14. Oates T, Valderrama P, Bischof M, Nedir R, Jones A, Simpson J, Toutenburg H, Cochran D. Enhanced implant stability with a chemically modified SLA surface: a randomized pilot study. Int J Oral Maxillofac Implants 2007 (In press).
15. Zöllner A, Ganeles J, Korostoff J, Guerra F, Krafft T, Brägger U. Immediate and early nonocclusal loading of Straumann implants with a chemically modified surface (SLActive) in the posterior mandible and maxilla: interim results from a prospective multicenter randomized controlled study. Clin Oral Implants Res 2007 (In press).
16. Akkacaoglu M, Uysal S, Tekdemir I, Akca K, Cehreli M. Implant design and intraosseous stability of immediately placed implants: a human cadaver study. Clin Oral Implants Res 2005; 16: 202-209
17. Fugazzotto P. Implant placement at the time of maxillary molar extraction: technique and report of preliminary results of 83 sites. J Periodontol 2006; 77: 302-309
18. Chiapasco M, Ferrini F, Casentini P, Accardi S, Zaniboni M. Dental implants placed in expanded narrow edentulous ridges with the Extension Crest device. A 1-3-year multicenter follow-up study. Clin Oral Implants Res 2006; 17: 265-272
19. Ferrigno N, Laureti M. Surgical advances with ITI TE implants placement in conjunction with split crest technique. 18-months results of an ongoing prospective study. Clin Oral Implants Res 2005; 16: 147-155
20. Lang N, Tonetti M, Suvan J, Bernard J-P, Botticelli D, Fourmousis I, Hallund M, Jung R, Salvi G, Shafer D, Weber H-P on behalf of European Research Group on Periodontology (ERGOPerio). Immediate implant placement with transmucosal healing in areas of aesthetic priority. A multicentre randomized –controlled clinical trial I. Surgical outcomes. Clin Oral Implants Res 2007; 18: 188-196.
21. Stephen Chen is a specialist periodontist in private practice in Melbourne, Australia. He is a Senior Fellow at the School of Dentistry, University of Melbourne. He is Chairman of the Australasian Section of the International Team for Implantology (ITI) and of the ITI Education Core Committee.
22. Frank Higginbottom is Clinical Associate Professor, Dept. of Oral and Maxiollofacial Surgery and Pharmacology, Restorative Sciences and Graduate Prosthodontics, Baylor College of Dentistry, USA. He is also Clinical Associate Professor, Dept. of Periodontics, University of Texas.
23. Summarized in STARGET 2007/4 pp. 24-25.
24. David Cochran is Prof. of Periodontics at the Uni. of Texas Health Science Center.
25. Guiseppe Cardaropoli is a Professor at the Dept. of Periodontology and Implant Dentistry, New York University, NY, USA.
26. Jung R, Jones AA Higginbottom FL Wilson T, Schoolfield J, Buser D, Hämmerle C, Cochran D. The influence of non-matching implant and abutment diameters on radiographic crestal bone levels. J Periodontol 2007 (In press).
27. Ronald Jung is Vice Chairman of the Dept. of Fixed & Removable Prosthodontics and Dental Material Sciences at the University of Zurich.
28. Cochran D, Jung R, Higginbottom F, Jones A, Wieland M. Platform shifting and the reality of crestal bone. American Academy of Periodontology 93rd Annual Meeting, Washington DC, USA, 27-30 Oct. 2007.
29. Giuseppe Cardaropoli, San-Choon Cho, Mitch Bloom, Nick Elian, Michel Dard, Dennis Tarnow. Bone Response Between Platform Switched Implants Placed With an Inter-Implant Distance of 4 and 3 mm: An Experimental Study in Minipigs. AAP Research Forum, 28 Oct. 2007.
30. Principal investigator: Prof. Daniel Buser, Chairman of the Dept. of Oral Surgery and Stomatology at the University of Bern, Switzerland.
31. Urs Belser is Chairman of the Dept. of Fixed Prosthodontics and Occlusion at the University of Geneva, and Fellow of the International Team for Implantology (ITI).
32. Christoph Hämmerle is Chairman of the Clinic for Fixed and Removable Prosthodontics and Dental Material Science, University of Zurich, Switzerland.
33. Principal investigator: Prof. Frank Higginbottom
34. Juan Blanco is an Associate Professor of the Dept. of Stomatology, University of Santiago de Compostela, Spain and has a private practice for periodontology and implantology. He is President of the Spanish Society of Periodontology and invited Professor of the Master Program for Periodontology at the University Complutense, Madrid.