Papers by Keyword: Resorption

Abstract: Dental implant failure started with a resorption on alveolar crest. Resorption occurred if the stress is greater than the strength threshold (ultimate strength). Bones carrying mechanical loads adapt their strength to the load applied on it by bone modelling or remodelling; by apposition or destruction depends on internal stress level distributed on the bones. This research was conducted using FEM on a CBCT image of model which were implanted and converted into computerized 3D finite element digital model. The model was given material properties, fixed support, and being simulated on occlusal loads of 87 N and friction loads of 29 N for 0,7 seconds.Maximum princip al loads on alveolar bone of implant model was 41 Mpa and still below the ultimate strength (69 MPa). Based on the stress level above, it may be concluded that alveolar bone on implant model has good resistance towards resorption.

Abstract: The high-tech method of creating anticorrosion calcium phosphate coating on the magnesium alloy MA8 (MgMnCe) has been developed. As was demonstrated by the volumetry method the sealing of the layer formed on the surface of Mg alloy using plasma electrolytic oxidation by superdispersed polytetrafluoroethylene substantially reduced the rate of the corrosion process. Here, the surface of the calcium phosphate layer containing hydroxyapatite (Ca/P = 1.61) remains biologically active. Studies of architectonics of the surface of innate immune cells have been performed in vitro.

Abstract: The purpose of this study was to analyze the histological, histochemical and radiological findings gained from pre-clinical in vitro and in vivo tests and from implantation of ß-tricalcium phosphate PORESORB^®-TCP (P). (P) is a bioactive, resorbable, inorganic, crystalline, non-metallic material with osseoconductive properties intended for replacement of bone tissue. The (P) granules (size 1-2mm) were implanted into the tibia of dogs for 3 and 6 months. The formation of 53% and 72% of new bone was observed after 3 and 6 months respectively.Material (P) sized 0.3-0.6 mm was used to fill in the periodontal defect and also as a carrier of growth proteins. During the study period, no undesired response to the material used was observed. The values of the plaque index showed standard hygienic conditions – the values of PlI were 0.72, 0.65 and 0.62 before treatment and 6 and 12 months after treatment, respectively.A total of 72 two-stage sinus lifts were performed in 54 patients. The autologous bone was harvested from the mandibular ramus and mixed with the (P) material sized 1-2 mm. The materials were used in a proportion ranging between 1: 1 and 1: 3. The residual allograft area was 16.21 ± 8.78 %. The connective tissue was 44.16 ± 5.85 %.This has been a retrospective review of the healing of bone defects, due to benign tumours or tumour-like lesions, using (P) material sized 1.3 mm, 0.7 mm (0.6-2 mm) as bone graft substitutes. 87 patients with bone defects (average volume 15 cm³; interval 0.4 – 144 cm³) were included. Defects with a volume up to 4 cm³ had the same successful rate of healing both for autologous bone grafts and (P). (P) sized 1.3 mm; 0.7 mm (0.6-2 mm) was successfully used in defects with volume up to 4 cm³. However, it is evident that the ratio of the size of the defect and the size of the applied granule must be kept near to 10/1 for successful treatment.

Abstract: Calcium sulfate/tri-calcium phosphate (CaSO₄/TCP) composite bone fillers were fabricated through molding method. Their structure and properties were characterized by infrared spectroscope, scanning electronic spectroscope, x-ray diffraction and degradation test. The results show that TCP crystals were attached to the CaSO₄ crystals and prevented the growing of sulfate crystals. So their size is shorter than that of CaSO₄ crystals prepared from pure CaSO₄ semihydrate, and some even had defect. The resorption rate of CaSO₄ bone fillers was decreased when TCP was incorporated.

Abstract: Calcium sulfate/hydroxyapatie (CaSO4/HA) composite bone fillers were fabricated through molding method. Their structure and properties were characterized by infrared spectroscope, scanning electronic spectroscope, x-ray diffraction and degradation test. The results show that HA crystals were attached to the CaSO4 crystals and prevented the growing of sulfate crystals. So their size is shorter than that of CaSO4 crystals prepared from pure CaSO4 semihydrate, and some even had defect. The resorption rate of CaSO4 bone fillers was decreased when HA was incorporated.

Abstract: A new biphasic calcium phosphate ceramic material Hydros™ has been developed. The main attractive feature of BCP ceramic is their ability to form a strong direct bond with the host bone resulting in a strong interface. Currently, granules are more and more used in moldable, injectable bone substitutes. However, the biological behaviour of the particles can be influenced not only by chemical composition and crystallinity, but also by several parameters as microporosity and nano-micro sized particles. The aim of the study was to assess, in animal experiment, the role played by an Hydrated Putty Bioceramics (Hydros™), based on specific combination of hydrophilic micro and macrosized BCP particles, to obtain high osteogenic Injectable Bone Substitute. No sign of clinical rejection was noticed. In muscular area, no fibrous encapsulation was observed, degradation of the smaller particles is observed by macrophages and giant cells. At 12 weeks, more of 75% of BCP was resorbed. The biocompatibility and safety in human orthopaedic applications (tibial plateau fracture) has been demonstrated.

Abstract: Due to the lack of macroporosity in current available Calcium Phosphate cement used in osteoarticular surgery, Micro and Macroporous Biphasic CaP Cement (MCPC™) was developed. The MCPC™ concept was the association of a settable and a fast resorbable matrix and a sieved fraction of microporous biphasic calcium phosphate (BCP) granules, recognized for the high osteoconductive and osteogenic properties. During the resorption of the matrix, a porous structure is created and the osteoconductive effect of the granules promotes the bone ingrowth. A goat preclinical study was realized to evaluate the efficacy of MCPC™ for C3 and C4 vertebral body filling defects during 6 months. Bone remodelling was evidenced demonstrating bone ingrowth at the expense of the cement and surrounding the residual BCP granules. Bone trabeculae were observed coming from the spongious bone to the implant site. Human vertebral body filling cases demonstrated the biocompatibility and the safety of MCPC™ for bone reconstruction. Results of this study demonstrated the importance of special combination of calcium phosphate granules in the MCPC™ to provide macroporosity and scaffolding for newly formed bone.

Abstract: In this study the degradation behaviour of pure hydroxyapatite (HA), pure tricalcium phosphate (β-TCP) and four biphasic calcium phosphate ceramics was studied to gain information about the influence of the phase composition on this property with the aim to tailor individually adapted bone substitute materials. The chemical dissolution of each ceramic composition was measured by its release of calcium ions into a buffered solution. With decreasing HA content in the ceramics the degradation rate increased. Cell experiments were carried out with stimulated osteoclast-like RAW 264.7 cells. Using biochemical, genetic and microscopic analysis, the differentiation of the cells on the ceramic samples was studied. The monocytic precursor cells differentiated into osteoclast-like cells on all ceramics. The strongest cell differentiation into osteoclast-like cells was found on ceramics with HA/β-TCP ratios of 80/20, 60/40 and 40/60. Cells on these ceramics had many nuclei and the largest cell size. As a result of resorption, lacunas were found on all ceramics except β-TCP. All these experimental results proved the influence of the phase composition on degradation and resorption of calcium phosphate ceramics. Biphasic calcium phosphate ceramics with HA/β-TCP ratios of 80/20 and 60/40 exhibited the most promising properties to serve as synthetic bone substitute materials because for integration in the physiological bone remodeling process the implanted bone substitute materials should have optimized dissolution and resorption properties.

Abstract: Various bioactive calcium phosphates such as hydroxyapatite (HA) and carbonate apatite (CA) bone substitutes have been studied because of the biocompatibility and osteoconductivity when implanted into bone defects. In this study, the interaction between bioceramics and osteoclast-like cell using the cell-line such a RAW264 was examined for the investigation of the important factors of the osteoclastic responses. From the results, the possibility of effectiveness by surface geometry and chemical property means solubility was suggested. Moreover, it was considerable that the CA induced much stronger responses to osteoclast-like cells than the HA.

Abstract: Injectable resorbable bone cements for bone void fillings are gaining in interest. The materials resorb in vivo with loss of void filling capacity and strength as a consequence. The objective with this study is to qualitative determining the dissolution behaviour for a calcium sulphate and a calcium phosphate cement as function of storage time in different storage medium and correlate to their strength development. Experiments were performed on a calcium phosphate based cement, Norian SRS, and a calcium sulphate based cement, MIIG X3. In the resorbtion study, the materials dissolution at different pH (3, 5 and 7) was compared over a period of 11 weeks. The materials compressive and biaxial flexural strength was measured after aging in phosphate buffer saline for up to 12 weeks. The proposed qualitative method to study dissolution behaviour of injectable biomaterials as function of time and medium were evaluated and proved to be useful. Both materials were dissolved after 3 weeks of storage in pH 3. MIIG X3 dissolved faster than Norian SRS at pH 5. At pH 7 both materials were stable over the test period of 11 weeks. For both materials the strength decreases with storage time. Norian had a higher compressive strength than MIIG X3 for the first week, after the first week the compressive strength was similar for the two materials. MIIG X3 showed a higher flexural strength than Norian during the full test period.