Making the right choice of bone substitute

Straumann BoneCeramic is a fully synthetic bone substitute consisting of 60% hydroxyapatite (HA) and 40% tri-calcium phosphate (TCP) in a homogeneous mix. The morphology and composition of BoneCeramic were developed in order to enable progressive replacement by autologous bone. The TCP component confers a capacity for absorption while the hydroxyapatite prevents too rapid remodelling, thus supporting the restoration and preservation of bone volume during the healing process. Dr Andres Stricker reports in this interview on his years of experience with Straumann BoneCeramic, which he has been using since it came on the market.

Q. Dr Stricker, in your opinion, what is the most important criterion for the use of a bone substitute?
A. The material must meet the demands made of a scientifically and clinically grounded substitute. It has to be osteoconductive – that is, it must function as a guide – so that it guarantees stable bone volume, not just in the short term but also long term. The bone cells must be able to quickly open up and then penetrate the material. Finally, the substitute should be replaced, or rather substituted, long-term by the growth of newly formed bone. For the practitioner, ease of handling during use is also important. 

Q. When did you start to use Straumann BoneCeramic, and what led you to decide precisely on this bone substitute?
A. We have been using the material regularly and continuously since April 2005, though with restraint initially while we awaited our first results. However, the indications were soon being steadily extended. The decision on a bone substitute was a long-term development, which led away from autologous bone exclusively toward substitutes. This was because the intraoral donor areas are limited in a few indications and we could not expect our patients always to agree to a bone graft from the iliac crest region. The aim was to build up and preserve volume with as little patient morbidity as possible. However, a precondition was that at least equally good clinical results would be obtained. And these conditions are met by Straumann’s fully synthetic BoneCeramic.

Q. For what indications do you use Straumann BoneCeramic?
A. The initial indication was external sinus lift, initially in a simultaneous but then in a two-stage procedure. BoneCeramic is currently used also for internal sinus lift, lateral augmentation, bone splitting and for augmentation of extraction sockets, that is, all the bone augmentation measures where the dimensions of the bone site are too small to provide stable fixation around implants so that long-term preservation of the structures can be achieved.

Q. How acceptable is the use of a bone substitute to the patients?
A. I can say that the patients are positive about it without exception, particularly because of the convincing clinical results. When advising patients, there is much less need for discussion as the term ‘fully synthetic’ is clearly defined. In contrast, there is certainly a need for further explanation in the case of other materials, whether substances containing protein, bovine or equine.

Q. Straumann BoneCeramic is a homogeneous biphasic calcium phosphate with absorptive properties. In your experience, has this property played an important part in the material and, if so, in which indications?
A. Straumann BoneCeramic can be described as gradually absorbable. Our histology results have shown that the material is not yet completely replaced after four and six months respectively but some of it was still present. However, obvious bone apposition around the particles is visible. The biphasic structure is an advantage here as the bone cells can grow in and the material is then replaced gradually. In this way, volume preservation is ensured since too rapid absorption would lead to collapse and thus to loss of the augmentation material.

In the aesthetic region, we observed very nice shaping of the hard tissue and thus of the overlying soft tissue. This property is certainly of relevance in certain cases. It is important that bone integration takes place and that the material is accepted well by the bone and maintains its volume. Any residual particles which are integrated but not yet substituted may form an absorption barrier, which keeps the aesthetic result stable in both the short and long term.

Q. What is your experience with regard to preservation of bone volume?
A. The preservation of bone volume is characterised by stability, particularly in the case of the numerous lateral augmentations that we have performed, stable shaping around the peri-implant tissue is apparent up to now. In a few patients, we have also demonstrated this by means of 3D iCAT tomography.

Q. How does Straumann BoneCeramic behave in the demanding anterior region?

A. In the aesthetic region, loss of tissue is particularly serious so preservation of structure must be guaranteed. We have often combined Straumann BoneCeramic with an absorbable membrane and autologous bone in a layered procedure. Bone chips from drilling or from shaving the adjacent region are laid on the sometimes very widely denuded implant surface using out modified Miller files. The second layer consists of Straumann BoneCeramic moistened with blood and held in place with the absorbable membrane. If it were simply applied without the membrane, the risk would be too great that the particulate material would slide off into the vestibulum so that ossification around the implant would fail. Since stable hard tissue is followed by stable soft tissue shaping, we can speak of very good aesthetic results at least up to the present time.

Q. So you also combine autologous bone with bone substitute. What are your criteria for deciding to use autologous bone?

A. We like combining autologous bone with asubstitute. However, we follow the philosophy of layering rather than mixing. In sinus lift, the materials are not mixed but instead the bone chips are taken from the tubercle region to the implant surface in order to ensure bone integration there. The remainder of the sinus volume is then filled up with Straumann BoneCeramic 500-1,000. If the patient does not want any of their own bone to be taken or the bone donor sites are too small, we use bone substitute exclusively. The consequence of this is that the augmentation material healing period is prolonged by two months.

Q. When you use a two-stage surgical procedure, how do you establish the right time for implantation when bone has been augmented beforehand with Straumann BoneCeramic?
A. In two-stage procedures, where augmentation has been carried out exclusively with BoneCeramic, we wait for six months. This is the average time, based on experience. The results are confirmed by our biopsies. A further six months following implantation, the prosthetic restoration is then carried out by our referring colleague. This time can be reduced from six to four months if particles of autologous bone from the bone mill and from the retromolar region are added.

Q. What is your experience with regard to secondary stability when bone is augmented with Straumann BoneCeramic?
A. The decision on simultaneous or secondary implantation with sinus lift is influenced by the residual bone content and the design of the implant to be inserted. If the implant can be anchored in the remaining bone with primary stability, we attempt simultaneous implantation in the patient’s interest. The patient thus has to have only one surgical procedure and at the same time benefits from a faster overall rehabilitation time. This procedure must not be employed at the expense of clinical safety but it is supported by clinical experience: with over 300 sinus lift procedures performed with BoneCeramic with an average healing period of  five months, we have been able to achieve an implant survival rate of 99.5% up to the present time with Straumann implants.

Q. Your overall summing up so far of Straumann BoneCeramic?
A. Our aim is always to rehabilitate the patient as fast as possible with as few procedures as possible, with the least morbidity and with long-term functional and aesthetic results. We have now used BoneCeramic just over 1,000 times and it has become an extremely valuable aid when augmentation measures are called for. Because of its fully synthetic components, constant volume and very high success rate, it has become a standard here.

References
L Cordaro, Dieter D Bosshardt, Piermario Palattella,Walter Rao, Giuseppe Serino, Matteo Chiapasco (2008). Maxillary sinus grafting with Bio-Oss® or Straumann® Bone Ceramic: histomorphometric results from arandomized controlled multicenter clinical trial. Clin Oral Impl Res 19; 796–803
Z Artzi, Miron Weinreb, Guy Carmeli, Rony Lev Dor, Michel Dard, Carlos ENemcovsk (2008). Histomorphometric assessment of bone formation in sinus augmentation utilizing a combination of autogenous and hydroxyapatite/biphasic tricalcium phosphate graft materials at 6 and 9 months in humans. Clin Oral Impl Res 19: 686-692
G-G K Zafiropoulos, O Hoffmann, A Kasaj, B Willershausen, O Weiss, TE Van Dyke (2007). Treatment of intrabony defects using guided tissue regeneration and autogenous spongiosa alone or combined with hydroxyapatite/beta tricalcium phosphate bone substitute or bovine-derived xenograft. Periodontol 78: 2216-2225
SJ Froum, SS Wallace, SC Cho, N Elian, DP Tarnow (2008). Histomorphometric comparison of a biphasic bone ceramic to anorganic bovine bone for sinus augmentation: 6- to 8-month postsurgical assessment of vital bone formation. A pilot study. Int J Periodontics Restorative Dent 28: 273-281
Schwarz F, M Herten, D Ferrari, M Wieland, L Schmitz, E Engelhardt, J Becker (2007). Guided bone regeneration at dehiscence-type defects using biphasic hydroxylapatite +beta tricalcium phosphate (BoneCeramic®) or a collagen-coated natural bone mineral (BioOss Collagen®): an immunohistochemical study in dogs. Int Jour of Oral & Maxillofacial Surgery 36: 1198-1206
Jensen SS, Yeo A, Dard M, Hunziker E,Schenk R, Buser. Evaluation of anovel biphasic calcium phosphate in standardized bone defect. Clin Oral Impl Res 2007; 18: 752-760

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