[Growth stimulation of human osteoblast-like cells by thrombocyte concentrates in vitro]. / Wachstumsstimulation von humanen osteoblastenähnlichen Zellen durch Thrombozytenkonzentrate in vitro.

AIM OF THE STUDY: Thrombocytes contain different growth factors. Their potential use for increasing bone regeneration is currently under discussion. Basic data about the biologic effect of platelet concentrates (platelet-rich plasma, PRP) are still lacking. This study analyzes the in vitro effect of PRP on the proliferation rate of human osteoblast-like cells (OLC). MATERIAL AND METHOD: Human OLC were stimulated with thrombocytes in different dilutions (0-1,700,000 thrombocytes/microliter). Three days later a WST test (Roche Diagnostics) was performed to measure the mitochondrial syntheses and cellular proliferation rate. RESULTS: The proliferation rate of the OLC was (concentration-dependent) increased up to a certain plateau by adding thrombocytes. Further stimulation led to a slight decrease in the proliferation rate. The statistical analysis of the extinction measurements showed significant differences in the cell proliferation rates between mostly all thrombocyte concentration groups (p < 0.0001). Moreover, a statistically significant difference was evaluated for the time-dependent change in extinction (0-5 h) (p < 0.0001). CONCLUSION: This study shows that the proliferation rate of human OLC can be stimulated in vitro by concentration-dependent platelet concentrates. This in vitro result supports the currently discussed assumption that the clinical use of PRP might increase bone regeneration.

[IMZ-TwinPlus bone implant system--4 years clinical experience]. / Das IMZ-TwinPlus-Schraubenimplantat-System--4 Jahre klinische Erfahrung.

AIM OF THE STUDY: For more than twenty years the IMZ-system has been in clinical use, since 1995 modified as IMZ-TwinPlus. The aim of this prospective clinical trial was to analyse the success of the latter implant system, which is an automatically threading cylindrical titanium screw with a deep structured surface (Fa. FRIATEC AG, Mannheim, BRD). Investigated parameters were the peri-implant situation of the soft tissues, the bone loss and the rate of implant failure after a maximum period of 4.5 years of clinical use. MATERIAL AND METHODS: From 1995-2000 sixty-eight patients were provided with a total of 278 IMZ TwinPlus screw implants for various indications (mainly alveolar ridge atrophy). 191 implants were inserted without any, 35 implants with a loco-regional and another 52 implants after comprehensive reconstructive osteoplastic surgery. 38 patients with 155 implants were re-examined using a standardised protocol to evaluate peri-implant hard- and soft tissue situation as well as the patient's subjective assessment of the treatment. RESULTS: With a maximum of 54 months the mean observation period was 30 months. The implant failure rate has risen to 6% so far (n = 18 in 12 patients). Two patients bearing 7 implants have passed away. One patient with 4 implants was lost to follow up. 249 implants were still under function at examination, thus the in situ rate was 91%. The Kaplan-Meier survival rate after 54 months proved 91%. DISCUSSION: To our knowledge there are at present no other data published on the survival rate of the IMZ TwinPlus implant system. The results of this study evaluate a survival rate similar to the classical IMZ cylinder implant and other implant systems for the analysed observation period. CONCLUSIONS: After a maximum observation period of 4.5 years the IMZ TwinPlus implant system showed results in the range of other well-established implant systems. Designed to resist rotation of the superstructure the IMZ TwinPlus screw implant widens the range of indications in comparison to the classical IMZ cylinder implant system.

[Cytokeratin expression in botryoid odontogenic cyst. A rare differential keratocyst and ameloblastoma diagnosis]. / Zytokeratinexpression der botryoiden odontogenen Zyste. Eine seltene Differentialdiagnose zu Keratozyste und Ameloblastom.

The botryoid odontogenic cyst (BOC) is considered a rare multilocular variant of the lateral periodontal cyst. The origin of the BOC can be seen in aberrant odontogenic tissue. The BOC is found especially in the premolar region of the mandible, as well as in the frontal region of the maxilla of patients aged between 60 and 70 years. Most of the 11 published articles of BOC have shown high rates of recurrence. Histopathologically the BOC is marked by multilocular cysts lined by a thin, nonkeratinized epithelium. Clusters of glycogen-rich epithelial cells may be noted in nodular thickenings of the cyst lining. For the clinician, the differentiation of the BOC from the keratocyst and ameloblastoma is relevant. One case of a large BOC (65-year-old male, BOC regio 33-45, diameter 5 cm, radiographically and histologically multilocular) is presented with a review of the literature, including the therapeutic management, and the possible diagnostic criteria are discussed. The immunohistochemically determined expression of cytokeratin (CK) 13 implicates the histogenetic origin of the BOC from the squamous epithelium of the oral cavity and excludes the origin from the small salivary glands. The expression of CK 19 and the lack of expression of p53, as well as the higher proliferation rate of the basal epithelial cell layer by the BOC, may be useful for distinction between the keratocyst.

[Determining the size of the specific surface of bone substitutes with gas adsorption]. / Bestimmung der Grösse der spezifischen Oberfläche von Knochenersatzmaterialien mittels Gasadsorption.

The surface area and the microporosity of bone regeneration materials influence their chemical and biological properties. Therefore, the size of the specific surface area and the distribution of the pore diameters (pores < 1 micron) of bone regeneration materials were analyzed within this study. The analyzed hydroxyapatites were of synthetic, bovine, and phytotroph origin. The tricalcium phosphates and the bioglasses included only synthetic materials. The gas adsorption of each specimen was analyzed using a volumetric N2/Kr system (ASAP 2010, Micromeritics). Additionally, for materials with a specific surface area (> 2 m2/g) the pore size distribution was evaluated by the BJH-method. Two of the materials evaluated astonishingly large dimensions of the specific surface area (BioOss 79.7 m2/g, Algipore new 14.6 m2/g). A medium surface area was found for Algipore old (4.9 m2/g) and Interpore200 (2.64 m2/g). All other included materials showed only small sizes of the specific surface area (Ceros80 1.8 m2/g, Ceros82 1.31 m2/g, Cerasorb 1.2 m2/g, Biobase 0.7 m2/g, Endobone 0.7 m2/g, Perioglas 0.6 m2/g, Allotropat50 0.23 m2/g, Biogran 0.2 m2/g). The materials with large and medium sizes of the specific surface area evaluated the following pore diameters: BioOss 2-50 nm, Algipore new 2-100 nm, Algipore old 5-50 nm, Interpore200 2-100 nm. Pore sizes less than 2 nm were not found in relevant numbers. The materials BioOss, old and new Algipore, and Interpore200 contain a large interconnecting mesopore system (diameter < 1 micron). For the materials Biobase, Endobone, Perioglas, Allotropat 50, and Biogran this cannot be assumed. The materials Ceros80, Ceros82, and Cerasorb evaluated a specific surface area between those and might include only a small part of these interconnecting pores. An influence of the interconnecting porosity and the different sizes of the specific surface areas on the biological behavior of the bone regeneration materials can be suggested.

[Roentgen spectrometry comparison of currently available bone substitutes]. / Röntgenspektrometrischer Vergleich der aktuell verfügbaren Knochenersatzmaterialien.

INTRODUCTION: The crystalline structure of hydroxyapatite (HA) and tricalciumphosphate (TCP) used as bone regeneration materials affects their physical and probably also their biological properties. Varying velocities of the HA solution process seem to be correlated to different results in powder diffraction analysis (RDX) [1], a validated, routine procedure in minerology [2, 6] to analyse crystallized materials. As far we know there are no comparative RDX analyses for the TCP materials in clinical use. GOALS: The dimension and quality of the crystallization of several bone regeneration materials are analysed by RDX. MATERIAL AND METHODS: The materials analysed were divided in different groups: hydroxyapatite, tricalciumphosphate and bioglass. The materials are characterized by the specific intensity curve measurements. RESULTS: The HA products, with the exception of Algipore, seem to be monophasic. Ceros80 and Endobone were the only ones which seem to be totally crystallized. The TCP products Biobase and Cerasorb are nearly monophasic, whereas Ceros82 seems to contain a mixture of 30% HA and 70% beta-TCP. All TCPs show a high crystallization. The bioglasses did--as suspected--not show crystalline structures. DISCUSSION: There are many possible causes for inhomogeneous crystallization of the investigated materials, as they are composites of different foreign ions, extremely small crystals or abnormal (deficient) apatites. How this affects the biological behaviour is not known. SUMMARY: We found differences between the examined materials; how this affects the biological behaviour is unknown. Further investigations are necessary to correlate the characteristics of the materials to the clinical outcome.