Ronald Mai

Publications of Ronald Mai

• Biological functionalization of dental implants with collagen and glycosaminoglycans-A comparative study.

  Authors: Bernd Stadlinger, Vera Hintze, Susanne Bierbaum, Stephanie Möller, Matthias C Schulz, Ronald Mai, Eberhard Kuhlisch, Sascha Heinemann, Dieter Scharnweber, Matthias Schnabelrauch, Uwe Eckelt

  Journal of biomedical materials research. Part B, Applied biomaterials. 11/2011;

  Biological implant surface coatings are an emerging technology to increase bone formation. Such an approach is of special interest in anatomical regions like the maxilla. In the present study, weBiological implant surface coatings are an emerging technology to increase bone formation. Such an approach is of special interest in anatomical regions like the maxilla. In the present study, we hypothesized that the coating of titanium implants with components of the organic extracellular matrix increases bone formation and implant stability compared to an uncoated reference. The implants were coated using collagen-I with either two different concentrations of chondroitin sulfate (CS) or two differentially sulfated hyaluronans. Implant coatings were characterized biochemically and with atomic force microscopy. Histomorphometry was used to assess bone-implant contact (BIC) and bone-volume density (BVD) after 4 and 8 weeks of submerged healing in the maxilla of 20 minipigs. Further, implant stability was measured by resonance frequency analysis (RFA). Implants containing the lower CS concentration had significantly more BIC, compared to the uncoated reference at both times of interest. No significant increase was measured from week 4 to 8. Differences in BVD and RFA were statistically not significant. A higher concentration of CS and the application of sulfated hyaluronans showed no comparable increase in BIC. This study demonstrates a positive effect of a specific collagen-glycosaminoglycan combination on early bone formation in vivo. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2011.

• Ultrasound-aided resorbable osteosynthesis of fractures of the mandibular condylar base: an experimental study in sheep.

  Authors: Matthias Schneider, Claudia Seinige, Eckart Pilling, Michael Rasse, Richard Loukota, Bernd Stadlinger, Ronald Mai, Uwe Eckelt

  The British journal of oral & maxillofacial surgery. 11/2011;

  We evaluated the osteosynthesis of condylar fractures using resorbable mini plates and ultrasound-aided insertion of pins clinically and histologically. Stability was greater than that withWe evaluated the osteosynthesis of condylar fractures using resorbable mini plates and ultrasound-aided insertion of pins clinically and histologically. Stability was greater than that with resorbable screws because of the fusion of pin and plate. Long term evaluation showed complete resorption of the polymeric osteosynthesis material.

• Orthodontic tooth movement into jaw regions treated with synthetic bone substitute.

  Authors: Tomasz Gedrange, Tomasz Gredes, Alexander Spassow, Ronald Mai, Sergio Alegrini, Marzena Dominiak, Christiane Kunert-Keil, Friedhelm Heinemann

  Annales Academiae Medicae Stetinensis. 01/2010; 56(2):80-4.

  Orthodontic tooth movement is fraught with risks and complications. Root resorption is the most frequent and important outcome which may arise due to inappropriate force magnitude or tooth movementOrthodontic tooth movement is fraught with risks and complications. Root resorption is the most frequent and important outcome which may arise due to inappropriate force magnitude or tooth movement into dense or altered bone. This study was aimed to demonstrate histologic changes in tooth roots following movement into a jaw region treated with synthetic bone substitute. Another objective was to evaluate the method of experimental tooth movement using an animal model. One mandibular premolar was extracted in each of three pigs (Sus scrofa domesticus). The extraction alveolus was filled with synthetic bone substitute material and a orthodontic appliance was attached for 90 days. The force for tooth movement was in the range of 1-2 N. Subsequently, specimens were collected using segmental osteotomy and were prepared histologically. Unmoved teeth served as controls. Histological analysis showed clear lacuna-like lesions in the root surface area of all specimens. The lesions were largest in the apical area, while the mid-root region was less affected. Due to deformations of the orthodontic tooth moving appliance, the force could not be exactly defined. Therefore, marked resorption lesions of the root surfaces cannot be unequivocally attributed to the synthetic bone substitute. However, the type of lesions on root surfaces permits the assumption that orthodontic tooth movement into areas filled with synthetic bone substitute may be associated with an increased risk of root resorption.

• Surface-conditioned dental implants: an animal study on bone formation.

  Authors: Bernd Stadlinger, Anna Theresa Lode, Uwe Eckelt, Ursula Range, Falko Schlottig, Thomas Hefti, Ronald Mai

  Journal of clinical periodontology. 10/2009;

  Stadlinger B, Lode AT, Eckelt U, Range U, Schlottig F, Hefti T, Mai R. Surface-conditioned dental implants: an animal study on bone formation. J Clin Periodontol 2009. doi:Stadlinger B, Lode AT, Eckelt U, Range U, Schlottig F, Hefti T, Mai R. Surface-conditioned dental implants: an animal study on bone formation. J Clin Periodontol 2009. doi: 10.1111/j.1600-051X.2009.01466.x. Abstract Aim: The aim of this study was to determine whether bone formation around surface-conditioned implants is enhanced compared with non-surface-conditioned sandblasted acid-etched titanium implants. Materials and Methods: One hundred and forty-four implants were placed in the mandible of 18 minipigs. Before placement, implants were either surface conditioned in a solution containing hydroxide ions (conSF) or assigned to controls. Animals were euthanized after 2, 4 and 8 weeks of submerged healing, the 8-week group receiving polyfluorochrome labelling at week 2, 4, 6 and 8. One jaw quadrant per animal was selected for histological and histomorphometrical evaluation of mineralized bone-implant contact (mBIC), osteoid-implant contact (OIC) and bone volume (BV) analysis. Results: Polyfluorochrome labelling showed no general differences in bone dynamics. mBIC showed the most pronounced differences after 2 weeks, reaching 65.5% for conSF compared with 48.1% for controls, p=0.270. Differences levelled out after 4 weeks (67.4% control, 65.7% conSF) and 8 weeks (64.0% control, 70.2% conSF). OIC levels were initially comparable, showing a slower decline for conSF after 4 weeks. BV was higher for conSF at all times. No significant differences could be found. Conclusion: A tendency towards increased mBIC was shown for surface-conditioned implants after short-term healing.

• Prefabricated bony radial forearm flap for secondary mandible reconstruction after radiochemotherapy.

  Authors: Henry Leonhardt, Winnie Pradel, Ronald Mai, Jutta Markwardt, Günter Lauer

  Head & neck. 07/2009;

  BACKGROUND: Primary reconstruction of the mandible is the golden standard of surgical treatment after ablative tumor surgery. Many different microvascular bone grafts are used to reduce wound healingBACKGROUND: Primary reconstruction of the mandible is the golden standard of surgical treatment after ablative tumor surgery. Many different microvascular bone grafts are used to reduce wound healing complications at the severely compromised recipient site. The loss of primary grafts due to radiotherapy or osteoradionecrosis can make secondary mandibular reconstruction necessary. To address this problem, we developed the technique of the prefabrication of a radial forearm flap with cancellous bone. The aims were to establish these techniques into the clinical routine and to create a safe and reliable flap with low donor site morbidity. METHODS: In patients who had undergone ablative tumor surgery radiochemotherapy, and primary reconstruction, prefabricated bony radial forearm flaps (PBRFFs) were applied for secondary reconstruction of the mandible. Cylinders of cancellous bone taken from the iliac crest were implanted in the lower forearm to allow the necessary vascularization. After a healing period of 4 weeks, the PBRFF was elevated and grafted into the mandibular defect. RESULTS: All grafts healed uneventfully. However, 1 case required revision of the venous anastomosis after 2 days. The transplants improved the contour of the lower face enabling a good correction of the facial asymmetry. During the follow-up of up to 4 years, the radiographic controls showed good bony consolidation between the graft and the stumps of the mandible as well as formation of cortical bone around the cancellous bone cylinders. CONCLUSION: These results demonstrate that the PBRFF is a safe and reliable graft which provides alternate solution in which other microvascular bone grafts have already failed. In the future, the iliac bone graft may be replaced with scaffold seeded with stem cells for further reduction of donor site morbidity. Head Neck, 2009.

• Increased bone formation around coated implants.

  Authors: Bernd Stadlinger, Susanne Bierbaum, Silke Grimmer, Matthias C Schulz, Eberhard Kuhlisch, Dieter Scharnweber, Uwe Eckelt, Ronald Mai

  Journal of clinical periodontology. 07/2009;

  Aim: We hypothesized that coating threaded, sandblasted acid-etched titanium implants with collagen and chondroitin sulphate (CS) increases bone formation and implant stability, compared withAim: We hypothesized that coating threaded, sandblasted acid-etched titanium implants with collagen and chondroitin sulphate (CS) increases bone formation and implant stability, compared with uncoated controls. Materials and Methods: Three different implant surface conditions were applied: (1) sandblasted acid-etched (control), (2) collagen/chondroitin sulphate (low-dose - CS1), (3) collagen/chondroitin sulphate (high-dose - CS2). Sixty 9.5 mm experimental implants were placed in the mandible of 20 minipigs. Bone-implant contact (BIC) and relative peri-implant bone-volume density (rBVD - relation to bone-volume density of the host bone) were assessed after 1 and 2 months of submerged healing. Implant stability was measured by resonance frequency analysis (RFA). Results: After 1 month, coated implants had significantly more BIC compared with controls (CS1: 68%, p<0.0001, CS2: 63%, p=0.009, control: 52%). The rBVD was lower for all surface conditions, compared with the hostbone. After 2 months, BIC increased for all surfaces. No significant differences were measured (CS1: 71%, p=0.016, CS2: 68%, p=0.67, control: 63%). The rBVD was increased for coated implants. RFA values were 71-77 at implantation, 67-73 after 1 month and 74-75 after 2 months. Differences in rBVD and RFA were not statistically significant. Conclusions: Data analysis suggests that collagen/CS has a positive influence on bone formation after 1 month of endosseous healing.

• Immunohistochemical Comparison of Markers for Wound Healing on Plastic-Embedded and Frozen Mucosal Tissue.

  Authors: Ronald Mai, Tomasz Gedrange, Henry Leonhardt, Nicole Sievers, Günter Lauer

  Cells, tissues, organs. 11/2008;

  Immunohistologic investigations of wound healing in human oral mucosa require specific cell biological markers as well as consecutive small biopsies. Small specimens are ideally embedded in plasticImmunohistologic investigations of wound healing in human oral mucosa require specific cell biological markers as well as consecutive small biopsies. Small specimens are ideally embedded in plastic (methylmethacrylate, MMA) resin due to their miniature size. This limits the use of antibodies for these markers. In this immunohistochemical study, the distribution of wound healing markers, e.g. cytokeratin (CK), laminin, collagen IV, vimentin, vinculin and fibronectin, were compared between semithin sections of plastic-embedded tissue and frozen sections of mucosal tissue in order to assess their use for future investigations. The antibodies against laminin, collagen IV and CK 1/2/10/11, 5/6, 13, 14, 17, 19 gave comparable staining patterns on cryostat sections of attached mucosa and on semithin sections of MMA-embedded attached mucosa. In the epithelial cell layers, the following distribution of CK immunostaining was observed: The basal cell layer was positive for CK 5/6, CK 14 and CK 19; the intermediate cell layer for CK 13, CK 17 and CK 1/2/10/11, and the superficial cell layer for CK 13 and CK 1/2/10/11. For most of these antibodies, enzyme digestion with 0.1% trypsin was adequate for demasking the antigens, except for anti-CK 14, anti-CK 17 and anti-laminin; predigestion with 0.4% pepsin in 0.01 N HCl gave similar staining results. The antibodies against vimentin, vinculin, fibronectin and CK 4 showed no affinity or a reciprocal reaction on the semithin sections. Therefore, the antibodies against CK 1/2/10/11; 5/6; 13; 14; 17, and 19, as well as the basement proteins laminin and collagen IV are deemed markers suitable on semithin sections of plastic-embedded attached oral mucosa.

• Finite element representation of bone substitute remodelling in the jaw bone.

  Authors: Tomasz Gedrange, Ronald Mai, Jens Weingaertner, Volker Hietschold, Christoph Bourauel, Winnie Pradel, Günter Lauer, Peter Proff

  Biomedizinische Technik. Biomedical engineering. 10/2008;

  Abstract The finite element (FE) method was originally developed on a physical basis for the computation of structure-mechanical problems. Meanwhile, it has been widely applied to medical issues.Abstract The finite element (FE) method was originally developed on a physical basis for the computation of structure-mechanical problems. Meanwhile, it has been widely applied to medical issues. This study sought a suitable method to build a FE model for remodelling processes in osseous defects supplemented with bone substitute material. For this purpose, the second right premolars were extracted from four pig mandibles (Sus scrofa domesticus) and the extraction alveoli were provided with synthetic bone substitute material. After 70 days, a segmented osteotomy of this area was performed for specimen collection. Radiographs of the specimens were taken in defined planes before and after fixation and embedded with Technovit 9100. Fixation-related shrinkage was quantified from the radiographs using reference lines. Computer tomographic (CT) and microCT images of the fixed and embedded specimens were obtained. From these data, a FE model was built. The construction of a FE model is sufficient to represent bone remodelling after supply of bone substitute material. The use of microCT data permits building a clearly more precise model.

• O-phospho-l-serine: a modulator of bone healing in calcium-phosphate cements.

  Authors: Ronald Mai, Romy Lux, Peter Proff, Günter Lauer, Winnie Pradel, Henry Leonhardt, Antje Reinstorf, Michael Gelinsky, Roland Jung, Uwe Eckelt, Tomasz Gedrange, Bernd Stadlinger

  Biomedizinische Technik. Biomedical engineering. 10/2008;

  Abstract Bone substitution materials are seen as an alternative to autogenous bone transplants in the reconstruction of human bone structures. The aim of the present animal study was to evaluate theAbstract Bone substitution materials are seen as an alternative to autogenous bone transplants in the reconstruction of human bone structures. The aim of the present animal study was to evaluate the clinical handling and the conditions of bone healing after the application of a phosphoserine and collagen-I-modified calcium-phosphate cement (Biozement D). The application of phosphoserine is supposed to influence the texture of the extracellular matrix. Standardised bone defects were created in the lower jaw of 10 adult minipigs. These defects were reconstructed with a pasty calcium-phosphate cement mixture. After a healing time of 4 months, the animals were sacrificed. The mandibles of all animals were resected and non-decalcified histological sections of the areas of interest were prepared. The experiment was evaluated by means of qualitative histology and histomorphometry. The hydroxyapatite cement entirely hardened intraoperatively. Modelling and handling of the cement was facile and the margin fit to the host bone was excellent. Histology showed that resorption started in the periphery and proceeded exceptionally fast. The bony substitution, especially in phosphoserine-endowed cements, was very promising. After a healing period of 4 months, phosphoserine cements showed a bone regeneration of nearly two-thirds of the defect sizes. In the applied animal experiment, the newly developed hydroxyapatite collagen-I cement is well suited for bone substitution due to its easy handling, its excellent integration and good resorption characteristics. The addition of phosphoserine is very promising in terms of influencing resorption features and bone regeneration.

• The biomaterial influences the ossification after sinus floor elevation using tissue-engineered bone grafts.

  Authors: Winnie Pradel, Ronald Mai, Gunnar Manolo Hagedorn, Günter Lauer, Sergio Allegrini

  Biomedizinische Technik. Biomedical engineering. 10/2008;

  Abstract Sinus floor elevation is the standard procedure that allows dental implant insertion in the atrophic posterior maxilla. Instead of autogenous bone, tissue-engineered bone grafts can be used,Abstract Sinus floor elevation is the standard procedure that allows dental implant insertion in the atrophic posterior maxilla. Instead of autogenous bone, tissue-engineered bone grafts can be used, but clear comparative clinical studies also assessing the influence of the biomaterial are missing. In six patients, tissue-engineered bone grafts were used in eight sinus floor elevations. After culturing osteoblast-like cells from biopsies of the maxilla, they were seeded on scaffolds made either from demineralised bovine bone matrix (DBBM) or from solvent-dehydrated mineralised bovine bone (SDBB), and grafted. In all patients primary wound healing was without complications, except for one patient in the SDBB group. After 12 months, implant insertion was possible only in the SDBB group; in the DBBM group, fibrous connective tissue was found in an attempt of implant insertion. After 5 months, implant placement was performed in one patient of each group. However, the two implants inserted in the DBBM group were lost after 6 weeks. Histology of the bone cores in the DBBM group at 5 months showed lamellar bone and osteoid, and at 12 months showed fibrous connective tissue. Inflammation and some resorption of the scaffold was found 5 months after SDBB grafting, and after 12 months cancellous bone formation encapsulating SDBB remnants were observed. These preliminary data suggest that the preparation method of the bovine bone matrix, in particular the mineral content, and therefore the mechanical stability may have some influence on the generation of new bone.

• Suitability of differently designed matrix-based implant surface coatings: An animal study on bone formation.

  Authors: Bernd Stadlinger, Eckart Pilling, Matthias Huhle, Evgenij Khavkin, Susanne Bierbaum, Dieter Scharnweber, Eberhard Kuhlisch, Uwe Eckelt, Ronald Mai

  Journal of biomedical materials research. Part B, Applied biomaterials. 06/2008;

  Introduction: The aim of the present study was to assay how bone formation around dental implants is influenced by differently composed collagen matrices and RGD peptide as implant surface coatingsIntroduction: The aim of the present study was to assay how bone formation around dental implants is influenced by differently composed collagen matrices and RGD peptide as implant surface coatings compared to a sandblasted titanium surface. Material and Methods: Five different implant surface coatings were designed: titanium (sandblasted), collagen type I, collagen type I&III, RGD-peptide, and mineralized collagen. Sixty experimental implants of a square-shaped design were inserted into the mandibles of 12 minipigs, 3 months following extraction of the premolar teeth. During the 6-month study period, sequential polyfluorochrome labeling was performed. After sacrifice, bone implant contact (BIC) was evaluated using histologic and histomorphometric methods. Results: New bone formation was observed against all implant surfaces. Polyfluorochrome labeling showed that bone growth started from the host bone in the majority of samples. The highest BIC was measured for collagen I and collagen I/III coated implants; however, significant differences between the coatings could not be found. Conclusion: Osseointegration was achieved for all implant surfaces. Although a statistically significant increase in BIC could not be demonstrated for the experimental coatings after the 6 months study period, there was also no discernible detrimental effect of the coatings in comparison to the uncoated titanium surfaces. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008.

• Effect of biological implant surface coatings on bone formation, applying collagen, proteoglycans, glycosaminoglycans and growth factors.

  Authors: Bernd Stadlinger, Eckart Pilling, Ronald Mai, Susanne Bierbaum, Ricardo Berhardt, Dieter Scharnweber, Uwe Eckelt

  Journal of materials science. Materials in medicine. 04/2008; 19(3):1043-9.

  OBJECTIVES: The aim of the present study was to evaluate six different implant surface coatings with respect to bone formation. Being major structural components of the extracellular matrix,OBJECTIVES: The aim of the present study was to evaluate six different implant surface coatings with respect to bone formation. Being major structural components of the extracellular matrix, collagen, the non-collagenous components decorin/chondroitin sulphate (CS) and the growth factors TGF-beta1/BMP-4 served in different combinations as coatings of experimental titanium implants. MATERIALS AND METHODS: Eight miniature pigs received each six implants in the mandible. The implant design showed two circular recesses along the length axis. Three, four, five and six weeks after implant placement, the animals were sacrificed in groups of two. Bone-implant contact (BIC) was evaluated along the outer implant surface and within the recesses. Bone volume was determined by synchrotron radiation micro computed tomography (SRmicroCT) for one implant of each surface state, 6 weeks after placement. RESULTS: At each week of observation, collagen/CS or collagen/CS/BMP-4 coated implants showed the highest BIC of all surface states. This was statistically significant at week five (p=0.030, p=0.040) and six (p=0.025, p=0.005). SRmicroCT measurements determined the highest bone volume for a collagen/CS coated implant. CONCLUSION: The results indicate that collagen/CS and collagen/CS/BMP-4 lead to a higher degree of bone formation compared to other ECM components.

• Histologic study of incorporation and resorption of a bone cement-collagen composite: an in vivo study in the minipig.

  Authors: Ronald Mai, Antje Reinstorf, Eckart Pilling, Matthias Hlawitschka, Roland Jung, Michael Gelinsky, Matthias Schneider, Richard Loukota, Wolfgang Pompe, Uwe Eckelt, Bernd Stadlinger

  Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics. 04/2008; 105(3):e9-14.

  OBJECTIVE: Calcium phosphates are clinically established as bone defect fillers. They have the capability of osseoconduction and are characterized by a slow resorption process. The present studyOBJECTIVE: Calcium phosphates are clinically established as bone defect fillers. They have the capability of osseoconduction and are characterized by a slow resorption process. The present study evaluated the suitability of a newly developed calcium phosphate cement modified with collagen type I. STUDY DESIGN: The modified cement paste was inserted in differently designed defects of 10 minipigs. Further, an alveolar ridge augmentation was performed, applying the cement paste. The cement hardened in situ during the operation, forming a hydroxyapatite collagen composite. Animals were sacrificed after 1, 3, 6, 12, and 18 months. The tissue integration and resorption process was then evaluated using nondecalcified microsections. All animals were evaluated for histology. RESULTS: The implanted material showed osseoconductive characteristics. Resorption started from the edge of the defect zone, and bone substitution followed rapidly. Twelve months after placement of the cement, complete remodeling was observed. CONCLUSION: It can be concluded that the applied hydroxyapatite-collagen cement composite shows good resorption and bone integration.

• Cryopreserved tissue engineered mucosa.

  Authors: Gabriele Spoerl, Ronald Mai, Edith Klingner, Tomas Gedrange, Günter Lauer

  Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society. 02/2008; 46(4):541-4.

  Single cells suspensions used for grafting in the clinical setting may be reliably cryopreserved by established protocols. However, for tissue engineered constructs which now also get used as graftsSingle cells suspensions used for grafting in the clinical setting may be reliably cryopreserved by established protocols. However, for tissue engineered constructs which now also get used as grafts in the clinic such established protocols and assays which indicate graft viability and their function as graft do not exist. a) The purpose was to develop a cryoprotocol and an animal model to test the efficacy of tissue engineered to act as graft after cryopreservation. b) Therefore, tissue engineered mucosa grafts consisting of keratinocytes and fibroblasts grown in a collagen sponge were cryopreserved and grafted in the nude rat to test its efficacy to function as mucosa graft. At different points after cryopreservation the mucosa was grafted into the nude rats. Healing of grafts was allowed for one or three weeks. c) Sufficient cells survived the cryopreservation allowing for the development of epithelial-fibroblast tissue in the collagen sponge. After three weeks of healing the formation of mucosa tissue was more complete and more collagen sponge had disappeared. d) The nude rat model is suitable to assess the efficacy of tissue engineered mucosa to function as graft after cryopreservation. The formation of human epithelial-fibroblast tissue in vivo has to be interpreted as proof of principle that the approach of cryopreservation of tissue engineered grafts is working.

• Mechanical loading of orthodontic miniscrews - significance and problems: an experimental study.

  Authors: Claudia Reicheneder, Kurt Rottner, Ivan Bokan, Ronald Mai, Günter Lauer, Gerd Richter, Tomasz Gedrange, Peter Proff

  Biomedizinische Technik. Biomedical engineering. 02/2008; 53(5):242-5.

  Abstract Orthodontic miniscrews are exposed to three mechanical loading phases during clinical use: torsional loading upon insertion, flexural loading during anchorage function, and torsional loadingAbstract Orthodontic miniscrews are exposed to three mechanical loading phases during clinical use: torsional loading upon insertion, flexural loading during anchorage function, and torsional loading upon removal. The aim of this study was to simulate clinical loading conditions for different types of orthodontic miniscrews in vitro to quantify the effects of combined torsional and bending stress. Various orthodontic miniscrew systems (Lomas, Dual-top, Aarhus anchorage, Tomas-pin and T.I.T.A.N.-pin) comprising 10 samples each were subjected to the following loading sequences in vitro: a torsional load corresponding to manual insertion with limited torque; and flexural loading at two different insertion depths. For all screw systems with torsional pre-loading (simulating insertion), subsequent flexural loading (simulating anchorage) yielded permanent deformations of approximately 0.15-0.25 mm, depending on the insertion depth. Since EDX analysis revealed comparable elemental compositions for the different screw systems, the differences in mechanical properties are attributed to screw design. Torsional loading during screw insertion may cause premature mechanical weakening and needs to be minimized. Unless fully inserted, screws show pronounced plastic deformation and hence fracture risk under subsequent flexural loading.

• Influence of extracellular matrix coatings on implant stability and osseointegration: an animal study.

  Authors: Bernd Stadlinger, Eckart Pilling, Matthias Huhle, Ronald Mai, Susanne Bierbaum, Ricardo Bernhardt, Dieter Scharnweber, Eberhard Kuhlisch, Ute Hempel, Uwe Eckelt

  Journal of biomedical materials research. Part B, Applied biomaterials. 11/2007; 83(1):222-31.

  Aim of the present study was to test the hypothesis that the application of components of the extracellular matrix such as glycosaminoglycans used as implant surface coatings in combination withAim of the present study was to test the hypothesis that the application of components of the extracellular matrix such as glycosaminoglycans used as implant surface coatings in combination with collagen, with and without growth factor, can lead to enhanced ossification and thus improve implant stability compared with collagen coatings alone. Twenty miniature pigs received 120 experimental titanium implants in the mandible. Three types of surface coatings were created: (1) collagen type I (coll), (2) collagen type I/chondroitin sulphate (coll/CS), (3) collagen type I/chondroitin sulphate/BMP-4 (coll/CS/BMP). Periimplant bone formation was assessed within a defined recess along the length axis of the implant. Bone-implant contact (BIC) and bone volume density (BVD) were determined, using both histomorphometry and synchrotron radiation micro computed tomography (SRmicroCT). To measure implant stability, resonance frequency analysis was applied after implantation and 1, 3, 7, and 22 weeks after placement. BIC was highest for coll/CS coated implants, followed by coll, p = 0.082. Histomorphometric BVD did not significantly change for any coating. SRmicroCT analysis showed an increased BVD for collagen coated implants, compared with the other two surface coatings. Implant stability showed a decrease for all coatings up to the third week. At 22 weeks, all coatings showed an increase in stability without reaching their initial level. Highest stability was reached for coll coated implants, p = 0.051. It was concluded that collagen and coll/CS implant coatings have advantageous characteristics for peri-implant bone formation, compared with the further integration of BMP-4.

• Bone welding--a histological evaluation in the jaw.

  Authors: Ronald Mai, Günter Lauer, Eckart Pilling, Roland Jung, Henry Leonhardt, Peter Proff, Bernd Stadlinger, Winnie Pradel, Uwe Eckelt, Jochen Fanghänel, Tomas Gedrange

  Annals of anatomy = Anatomischer Anzeiger : official organ of the Anatomische Gesellschaft. 02/2007; 189(4):350-5.

  The expansion of biodegradable osteosynthesis systems in clinical application correlates well to the progress in development of new materials as to the improvement of application methods. One ofThe expansion of biodegradable osteosynthesis systems in clinical application correlates well to the progress in development of new materials as to the improvement of application methods. One of those new application methods is the ultrasound-aided insertion of Resorb-X pins. The aim of this study was the histological evaluation of possible thermal damage to bone due to the ultrasound insertion. For this purpose, condylar neck fractures in 12 sheep were produced, repositioned and fixed by Resorb-X plates and pins. The animals were sacrificed in two groups, one after 2 weeks and one after 9 weeks. The bone-pin interlinkage and the structure of the bone were histologically evaluated. After 2 weeks a tight bone-polymer interlinkage was seen. Neither a pronounced foreign body reaction nor an interposition of fibrous tissue at the interface or a thermally induced necrosis was observed. The late phase of wound healing after 9 weeks showed pathomorphological characteristics within the normal range of bone healing. The bone seemed to be free of any alteration caused by process engineering. We conclude that thermal stress caused by ultrasound-aided pin insertion does not lead to cellular reaction in the bone. The fast and easy application of this improved biodegradable osteosynthesis system will bring a clear advantage in clinical use.

• Plate osteosynthesis of the mandibular condyle.

  Authors: Günter Lauer, Dominik Haim, Peter Proff, Gerd Richter, Winnie Pradel, Jochen Fanghänel, Eckhard Pilling, Tomasz Gedrange, Ronald Mai

  Annals of anatomy = Anatomischer Anzeiger : official organ of the Anatomische Gesellschaft. 02/2007; 189(4):412-7.

  The aim of this study is to evaluate and compare the biomechanical stability of various osteosynthesis materials for mandible condylar-process fractures. On 160 porcine mandibles, four differentThe aim of this study is to evaluate and compare the biomechanical stability of various osteosynthesis materials for mandible condylar-process fractures. On 160 porcine mandibles, four different monocortical plating techniques (40 per group) were investigated. Condyles were fractured at a defined location from the incisure to the posterior border. After correct anatomical reduction the fractures were plated, using four different techniques. Osteosynthesis materials used were the delta plate, the trapezoid plate, the dynamic compression plate and double mini-plates. Each group was subjected to linear loading in lateral to medial, medial to lateral, anterior to posterior and posterior to anterior directions by a universal mechanical testing machine TIRAtest 2720. Yield load, yield displacement were measured for the different plates. Statistically significant differences were noted between the fixation groups in all four directions. Rigid internal fixation with double mini plates showed the best stability in all directions except posterior to anterior. In this direction, the delta-plate resisted the highest loads. In the three other directions, the delta plate was second best with data similar to double miniplates but lower in magnitude.

• Regional changes in the masseter muscle of rats after reduction of blood supply.

  Authors: Peter Proff, Jens Weingärtner, Jochen Fanghänel, Marzena Gredes, Ronald Mai, Tomas Gedrange

  Annals of anatomy = Anatomischer Anzeiger : official organ of the Anatomische Gesellschaft. 02/2007; 189(1):59-64.

  The masticatory musculature is an integral functional part of the stomatognathic system and influences craniofacial morphogenesis and morphology. This animal study aimed to investigate theThe masticatory musculature is an integral functional part of the stomatognathic system and influences craniofacial morphogenesis and morphology. This animal study aimed to investigate the morphological consequences of restricted regional blood supply to the m. masseter. A total of 20 adult male Wistar rats (Rattus norvegicus Berkenhout) were divided into an experimental group and a control group comprised of 10 animals respectively and kept under standardized conditions. The experimental group underwent a dextrolateral complete surgical ligation of the a. carotis communis and, after 5 weeks, specimens were taken from the masseters. The muscle samples were analyzed immunohistochemically for fiber distribution and capillary density. Analysis revealed a discrete increase in the proportion of type I fibers with a significant increase of capillary number per area. Although no agreement exists on the alterations occurring in chronically ischemic muscles, it may be assumed that chronic ischemia evokes histomorphological adaptation processes similar to endurance training effects.

• Change of mRNA amount of myosin heavy chain in masseter muscle after orthognathic surgery of patients with malocclusion.

  Authors: Tomas Gedrange, Cordula Büttner, Matthias Schneider, Günter Lauer, Ronald Mai, Ronald Oppitz, Winfried Harzer

  Journal of cranio-maxillo-facial surgery : official publication of the European Association for Cranio-Maxillo-Facial Surgery. 10/2006; 34 Suppl 2:110-5.

  INTRODUCTION: Surgical correction of malocclusion changes the force to moment ratio of masticatory muscles inserting at the mandible caused by shortening, lengthening and rotation of the boneINTRODUCTION: Surgical correction of malocclusion changes the force to moment ratio of masticatory muscles inserting at the mandible caused by shortening, lengthening and rotation of the bone following osteotomy. During muscle adaptation the expression of mRNA for the myosin heavy chain (MyHC) of type I and type II fibres may be changed. MATERIAL AND METHODS: The adaptation of the masseter muscle was investigated at the mRNA level in 10 patients 6 months after orthognathic surgery in the mandible. The competitive polymerase chain reaction (cPCR) is a suitable method for quantification of MyHC mRNA. For application of this minimal invasive method an amount of 35 mg muscle tissue was sufficient. RESULTS: 6 month postoperatively there was a deficiency of about 87% of MyHC mRNA for fibre type I and II in both groups of patients. The deficiency in patients with mesial position of the mandible was higher but not significant different to patients with distal malocclusion. CONCLUSION: Patients should use the postoperative interval for training their masticatory muscles. This improves the stability of treatment result and prevents relapse.