Wolfram Höland

Development of machineable bioactive glass ceramics for medical uses

Abstract Following a controlled, two-stage phase separation in glasses of the system Na2O/K2OMgOAl2O3SiO2CaOP2O5F, annealing results in both fluorophlogopite and apetite crystallization. The phlogopite mica crystals make the material machineable, whereas the apatite crystals provide for its bioactivity. Animal tests show direct intergrowth with the bone. Bone cells and blood vessels can be found in the immediate neighbourhood of the implant.

Development, structure, properties and application of glass-ceramics for medicine

Abstract Glass-ceramics of the type Bioverit can be used as implants for hard tissue (bones). The structures of four biomaterials of the type Bioverit are discussed: biocompatible machineable glass ceramics with mica crystals; bioactive machineable glass ceramics with mica and apatite crystals; bioactive phosphate glass ceramics with apatite and AlPO4-crystals; and a new composite material. Applications of Bioverit are possible in orthopaedics, head and neck surgery and stomatology.

Control of phase formation processes in glass-ceramics for medicine and technology

Abstract The control of phase separation processes in silicate glasses makes possible the control of nucleation and crystallization of base glasses. Ti(III,IV)-species influence the phase formation in SiO 2 –Al 2 O 3 –MgO glasses to form glass-ceramics based on s- and α-quartz solid solutions. Additions of Na 2 O, K 2 O and F in a specific composition range and heat treatment of the glass result in an new glass-ceramic with curved micas. The structure of these crystals shows a high tetrahedral rotation. Glasses of the SiO 2 –Al 2 O 3 –MgO–Na 2 O–K 2 O–P 2 O 5 –F system show a double phase separation. Apatites and micas grow as a result of controlled in situ crystallization. The material can be machined and has bioactive properties. Phosphate glasses show no glass-in-glass phase separation. However, the high supersaturation is cancelled by a thermal treatment of the glass and a primary crystal is formed. Apatite crystals grow in the primary phase.

Crystallization of SiO2Al2O3MgO gel glasses

Abstract Basic glasses are prepared by chemical polymerization in a sol-gel process. Nucleation and crystallization of these glasses are analyzed in dependence of the composition of the basic glasses and “additions” of TiO 2 and LiO 2 . A comparison of gel glasses with conventionally molten glasses is made. Gel glass-ceramics are prepared as bulk materials and thin coatings.

Characterization of Bone-Glass Ceramic Interface

ABSTRACT Glass ceramics for bone substitution have been developed derived from the Si02-(A1203)-MgO-Na20-K20-(CaO)-(P205) glass forming system. The concentration of the ion content within the biomaterials could be varried in dependence of the indication. The glass ceramics are multiphase materials, they contain a glassy phase and crystalline phases. Machineable and bioreactive glass ceramics, containing apatite and mica-type crystals, show ion exchange reaction with body fluid. The interface reaction with living bone is limited in a depth of less than 15 ¨m. ESMA- and SIMS-investigations demonstrate the ion exchange and surface diffusion of the biomaterial.

Machinable Bioactive Glass-Ceramic

The development of glassy-crystalline materials, the glass-ceramics, showed that materials can be formed which have new properties that any other inorganic material. So called “machinable glass-ceramics” are important for industrial appplications (1,2). These materials consist of a glassy phase and a mica crystal phase. The mica crystal, e.g., the fluorophlogopite (Na,K)Mg3/AlSi3010/F2 is responsible for the excellent machinability. This means that the material is machinable with standard metal-working tools or instruments for the machining of ceramic materials.