Our research projects are closely related to the principles of translational medicine and the clinical practice. In the light of steady development of surgical techniques, we have broadened our focus and are now exploring the feasibility of resorbable osteosynthesis material on bone regeneration. Different clinically relevant models have been applied to assess the bone healing process using various types of biomaterials and dental implants. Another field of interest is computer assisted planning and production of material for skull reconstruction (CAD/CAM). With the help of these innovations, we intend to shorten the time spent in the operation theatre, enhance the bone healing process and optimize the outcome of complex cases.
The interest of our Research Group is focused on translational research. A key topics within the field of bone regeneration are the development of new biomaterials, assessment of the biocompatibility and the influence of the biodegradation on guided bone regeneration.
The indication for a specific bone substitutes material is related to the type and the stage of alveolar-ridge resorption. Vertical bone defects are considered the most demanding for the reconstruction. The feasibility of simultaneous vertical bone augmentation using block grafts (bone ring) and implant placement was established in collaboration with Advance Research Center, The Nippon Dental University School of Life Dentistry at Niigata, Japan. In terms of osseointegration, single-stage implant placement with autogenous bone has been demonstrated as useful to shorten an overall treatment period. Different biomaterials in block form have been developed to avoid the use of the autogenous block bone grafts. The original form of the presently used block grafts substitutes in a critical size defects was well maintained, but the ingrowth of a newly formed bone was neglectable. The evaluation of the bone substitute materials in a ring form used for the vertical augmentation of the alveolar ridges was supported by Grants-in-Aid for Scientific Research (Kakenhi Grant), Japan Society for the Promotion of Science, and is presently underway.
In attempt to achieve a complete regeneration of demanding bone defects, we intended to evaluate a strategy of bone tissue engineering application. In a collaboration with a Prof. Hofstetter Group, bone morphogenic protein 2 (BMP2) was successfully applied onto β-tricalcium phosphate (β-TCP) ceramics to support bone formation in the femoral critical size defects. Administration of alendronate (ALN) caused a reduction in implant turnover, demonstrating the dependence of β-TCP removal on osteoclast activity, rather than on chemical solubility. The International Team for Oral Implantology (ITI), Basel supported the study on the application of ALN in the tooth alveolus, aiming to hinder pronounced bone alterations following tooth extraction. The ALN-treated sockets had preserved more lingual bone areas, while control sockets showed better preservation of the buccal bone areas. ALN treatment resulted in more osteoid formation within the extraction sockets compared with the control. In the next step, the effects of a single concentration will be related to the mode and timing of ALN application.
Another key topic is the evaluation of the mechanism of supraosteal bone formation by mechanical manipulation of periosteum. In the periosteal distraction osteogenesis (PDO), the periosteum is gradually elevated from the original bone surface without performing the osteotomy. Different models and devices were established to identify the regulatory mechanism fundamental to the PDO. A hinge distractor was developed that allows less disruptive elevation of the periosteum. A series of studies indicated that the reciprocal effects between the bone and the periosteum are most important for de novo bone formation induced by PDO. Dr. Saulacic received a SNF grant with the aim of assessing the mechanobiological principles governing hard tissue formation induced by alternated activation and relaxation of periosteum (pumping of periosteum, PP). New bone formation set the foundation for more advanced molecular analysis, performed in collaboration with the Division of Bone Diseases, Department of Internal Medicine Specialties, Geneva University Hospital and Faculty of Medicine, Geneva. A boost release of all osteogenic growth factors in bone was observed in PP group two weeks after periosteal manipulation. The study elucidating different parameters of PP is currently underway, combining molecular approaches and in vivo experimentation.
A series of in vivo experiments initiated to assess the rate of bone formation and resorption of the resorbable synthetic and collagen-based bone substitute materials was supported by Osteology Foundation, Luzern and Geistlich Pharma AG, Wolhusen. Lowering the level of biomimetic hydroxyapatite coating induced higher rate of bone formation concomitant with the higher degradation rate of bicalcium phosphates (BCP). The addition of BCP was beneficial also when used in combination with other, more frequently used biomaterials. These results shell be confirmed in another demanding model of de novo bone formation, beyond the skeletal envelope. In an in vivo study performed in collaboration with the Department of Periodontology, School of Dental Medicine, University of Bern, collagen has been demonstrated as a biocompatible carrier for BCPs. Samples containing collagen showed less residual biomaterial than without collagen, but new bone volume and area was similar for both biomaterials. Collagen based biomaterials were successfully applied in the treatment of periodontal defects. At present, the effects of collagen materials, either alone or in combination with other biomaterial, are investigated before the corresponding clinical studies will be set up.