Michael Thorwarth

Comparative analysis of osseointegration of titanium implants with acid-etched surfaces and different biomolecular coatings

OBJECTIVES An increasing trend toward implantation in complex cases, as well as early loading, is beginning to emerge in dental implantology. Long-term stability of the inserted implants greatly depends on the osseointegration process. Although there are numerous current research efforts aimed at functionalizing implant surfaces, no single factor has proved to be beneficial for osseointegration. The aim of the present study was to investigate whether a combination coating of collagen I and different cytokines enhances osseointegration. STUDY DESIGN Commercially available titanium implants (Semados S; Bego Implant Systems, Bremen, Germany) were coated with collagen I and either 1 μg or 10 μg of bone morphogenic protein 2, vascular endothelial growth factor 165, basic fibroblast growth factor 2, or a combination of all 3 factors by using the biodot method. Experimental implants (1 pure titanium, 1 collagen I coated and 8 different cytokine coatings) were inserted in the frontal skulls of 9 domestic pigs (10 implants in each animal). Implants were retrieved 2, 4, and 8 weeks after surgery. Samples were subjected to microradiography and immunohistochemistry for collagen I and osteocalcin. RESULTS Implant coating with collagen I significantly increased collagen I (P = .028) and osteocalcin (P = .037) expression at the 2-week follow-up and osteocalcin expression (P = .042) as well as the bone implant contact (P = .049) at the 4-week follow-up compared with pure titanium. Additional cytokine coating had no significant effect compared with the collagen I coating. CONCLUSIONS It can be concluded that collagen I coating enhances osseointegration. However, additional growth factor application has no further beneficial effects.

Interdisciplinary treatment and ophthalmological findings in Parry-Romberg syndrome.

Parry-Romberg syndrome is a rare pathologic process, characterized by progressive hemifacial atrophy. A case of Parry-Romberg syndrome with ocular involvement is reported. A 27-year-old male patient with Parry-Romberg syndrome was interdisciplinary investigated and treated. For reconstruction of hemifacial soft tissues a free vascular parascapular graft was performed. Opthalmological findings included an evident enophthalmos and an eyelid lag with keratopathy and epiphora. Furthermore pupillary disturbances and endothelial precipitates were detectable. Complete fundus examination showed a unilateral optic disc swelling, central vitreous opacities and peripheral pigmentary disturbances. In the presented case of Parry-Romberg syndrome a rare association to ophthalmological involvement could be found. Beside the enophthalmos and eyelid alterations, also a panuveitis with papillitis should be treated by steroid therapy.

Riesenzellgranulom und Osteitis fibrosa cystica bei Hyperparathyreoidismus

Zu ossären Läsionen des Kiefers mit ähnlichem histologischen Bild gehören das zentrale Riesenzellgranulom und braune Tumoren bei Hyperparathyreoidismus. Da auch der radiologische Befund dieser Erkrankungen nahezu identische Merkmale aufweist, ist die differenzialdiagnostische Abgrenzung schwierig. Liegen zusätzlich maligne Grunderkrankungen vor, ist die Abgrenzung von ossären Metastasen ein zusätzliches Problem. Es wird über zwei Patienten mit osteolytischen Läsionen der Maxilla berichtet. In beiden Fällen lag eine maligne Grunderkrankung (Prostatakarzinom, Mammakarzinom) vor, die Zuweisung erfolgte jeweils wegen des Verdachts auf ossäre Metastasierung. Klinisch fanden sich identische Befunde. Die Biopsie zeigte riesenzellhaltige Läsionen des Knochens, wodurch die zunächst vermutete Metastasierung ausgeschlossen werden konnte. Bei einem der Patienten war im Labor der massiv erhöhte Parathormonspiegel auffällig. Aufgrund der raschen Größenprogression wurde initial eine chirurgische Therapie durchgeführt. Im Rahmen der weitergehenden Diagnostik konnte bei diesem Patienten ein Adenom der Nebenschilddrüsen festgestellt werden. Eine kausale Therapie wurde eingeleitet. Die beiden geschilderte Fälle demonstrieren die Schwierigkeiten bei der Differenzialdiagnostik der Riesenzellläsionen des Kiefers. Eine exakte Diagnostik ist für die Einleitung einer adäquaten Therapie jedoch unumgänglich. Die einzelnen Krankheitsbilder werden hier im Zusammenhang mit den notwendigen diagnostischen und therapeutischen Maßnahmen gegenübergestellt. Giant cell lesions of the bone present similar histological features. The differential diagnosis comprises central giant cell granuloma, giant cell tumor of bone, and osteitis fibrosa cystica (brown tumor) in combination with hyperparathyroidism. Since these lesions may mimic metastatic bone disease in patients with a history of cancer, a malignant process has to be considered. Since the treatment and prognosis of these entities—benign versus malignant osteolytic bone processes—differ greatly, definitive differential diagnosis is of utmost importance. Two patients presenting with osteolytic lesions of the maxilla are reported here. In both cases a history of cancer (breast and prostate) suggested bone spreading of these malignant tumors. The clinical and histological findings were similar in both patients. One lesion was diagnosed as central giant cell granuloma, the other was found to be brown tumour in osteitis fibrosa cystica as an initial manifestation of hyperparathyroidism. The presented cases demonstrate the difficulties in establishing the correct diagnosis of patients found to have osteolytic lesions of the jawbones which is critical for the appropriate management of these patients. The article discusses the different entities of osteolytic lesions of the jawbones and the necessary diagnostic and therapeutic approach.

Transgenic overexpression of VEGF164 enhances topical neoangiogenesis without detectable local or systemic side effects.

Various routes of administration have been used for delivering angiogenic genes to ischemic regions. A previous, preliminary study proved the feasibility of in vivo neoangiogenesis stimulation by ex vivo vascular endothelial growth factor (VEGF)-transduced fibroblasts. Taking this into account our aim was to validate therapeutical efficacy of this approach and to investigate potential side effects.Allogenous collagen membranes were implanted at the groin in 30 Wistar rats. Either untransfected, GFP- or VEGF-transfected fibroblasts were injected at the implantation site at the time of surgery. Biopsies were obtained from the membranes, surrounding connective tissue, brain, lung, liver and blood at days 7 and 14 post operation. Samples were investigated for distribution of GFP-positive cells, VEGF-expression, and vessel architecture.Transgenic fibroblasts remained at the site of injection and showed no trafficking into blood or organs. VEGF-overexpression was detectable and resulted in enhanced neovascularization of the membranes. Vessel pathologies were neither detectable in the membrane nor the surrounding tissue.

Combined treatment protocol for temporomandibular joint ankylosis: an observation on a clinical problem.

Various techniques have been defined for the treatment of temporomandibular joint ankylosis. However, in some cases, they are unsuccessful, resulting in continuing pain and limitation in interincisal distance after surgery. This report describes the case of a 32-year-old woman who has been experiencing temporomandibular joint ankylosis for a period of 8 years. Several surgical procedures failed. A treatment approach combining auricular cartilage interposition arthroplasty with postsurgical functional treatment using a spring activator is presented. Using this approach, pain settled and maximal interincisal distance was raised from 22 to 35 mm after 4 months and remained stable for further 10 months.

Experimentelle Untersuchung zur Oberflächenaktivierung von Implantaten durch liposomale Vektoren—eine Pilotstudie

BACKGROUND Surface coating with mitogenic or morphogenic proteins can improve the healing of bone adjacent to implants and increase the bone-implant interface. Clinical surveys have shown liposome-mediated gene transfer to be a promising and safe new therapeutic method. The aim of our study was to evaluate an experimental model of new approaches for topical treatment of the implant surface and of periimplant defects by using DNA liposomes encoding for BMP-2 (bone morphogenetic protein). MATERIAL AND METHODS A total of 27 implants (3.5 x 14 mm) were placed in critically sized defects of the frontal skull bone of adult pigs (n=3). The bottom of the implant was placed in the base of the defect which guaranteed primary stability, whereas the superior part of the implant (10 mm) represented an implant in a defect area. Liposomes containing DNA encoding for BMP-2 and GFP (green fluorescence protein) were used. In a first trial GFP-DNA liposomes on a collagen matrix were directly applied to the periimplant defect. In a second stage, the surface of the implants was encoded with BMP-2 DNA liposomes. Subsequently, these implants were inserted in the manner described. The resulting bone samples were prepared for immunohistochemical staining. Staining for GFP was performed in the area of the defect and for BMP-2 on the bone-implant interface. RESULTS Immunohistochemical staining on day 3 postoperatively revealed an increased GFP expression in the periimplant defect. Therefore, the effectiveness of the liposomal vector was verified for the chosen animal model. On the surface of the implants encoded with BMP-2 DNA liposomes an increased BMP-2 expression was found. Thus, the liposomal vector system was validated also for BMP-2 DNA transfer in the chosen animal model. Further, the established system allows a sustainable and delayed release of BMP-2 in the area of the bone-implant interface. CONCLUSIONS As a result of the study we were able to collect data concerning the influence of implant surface conditioning on the bone-implant interface and on therapeutically relevant options for the treatment of periimplant defects. These approaches are currently being evaluated in a long-term study.

Experimentelle Untersuchung zur Oberflchenaktivierung von Implantaten durch liposomale Vektoren?eine Pilotstudie@@@Experimental pilot study on surface activation of implants with liposomal vectors

BACKGROUND Surface coating with mitogenic or morphogenic proteins can improve the healing of bone adjacent to implants and increase the bone-implant interface. Clinical surveys have shown liposome-mediated gene transfer to be a promising and safe new therapeutic method. The aim of our study was to evaluate an experimental model of new approaches for topical treatment of the implant surface and of periimplant defects by using DNA liposomes encoding for BMP-2 (bone morphogenetic protein). MATERIAL AND METHODS A total of 27 implants (3.5 x 14 mm) were placed in critically sized defects of the frontal skull bone of adult pigs (n=3). The bottom of the implant was placed in the base of the defect which guaranteed primary stability, whereas the superior part of the implant (10 mm) represented an implant in a defect area. Liposomes containing DNA encoding for BMP-2 and GFP (green fluorescence protein) were used. In a first trial GFP-DNA liposomes on a collagen matrix were directly applied to the periimplant defect. In a second stage, the surface of the implants was encoded with BMP-2 DNA liposomes. Subsequently, these implants were inserted in the manner described. The resulting bone samples were prepared for immunohistochemical staining. Staining for GFP was performed in the area of the defect and for BMP-2 on the bone-implant interface. RESULTS Immunohistochemical staining on day 3 postoperatively revealed an increased GFP expression in the periimplant defect. Therefore, the effectiveness of the liposomal vector was verified for the chosen animal model. On the surface of the implants encoded with BMP-2 DNA liposomes an increased BMP-2 expression was found. Thus, the liposomal vector system was validated also for BMP-2 DNA transfer in the chosen animal model. Further, the established system allows a sustainable and delayed release of BMP-2 in the area of the bone-implant interface. CONCLUSIONS As a result of the study we were able to collect data concerning the influence of implant surface conditioning on the bone-implant interface and on therapeutically relevant options for the treatment of periimplant defects. These approaches are currently being evaluated in a long-term study.