Advances in Science and Technology Vol. 49

Abstract: In the treatment based on Guided Bone Regeneration method (GBR), membranes are necessary to cover bone defects and prevent the invasion of surrounding soft tissues. In spite of the potential usefulness of GBR method, no appropriate materials for the membrane have been developed and this method is not utilized frequently in common clinical practice. Here we developed materials such as a composite of β-tricalcium phosphate (β-TCP) and copolymer of L-lactide, glycolide and ε-caplolactone (PLGC), and designed the novel GBR membranes with ideal mechanical properties. The materials had good biocompatibility, and the membrane had sufficient strength although their thickness was as thin as 200 μm. The membranes were applied to large bone defects created in canine mandibular bones, and significant enhancement in bone regeneration was demonstrated.

Abstract: This Study is based on the search and selection of suitable bioceramic materials as bone substitute in cases where the osseous tissue is lost. A total of 42 pieces were used divided in 3 groups: 14 of Alumina (Al2O3), 14 of Zirconia (ZrO2) and 14 of Zircon (ZrSiO4). The bioceramic materials were inserted on 21 adult dogs divided in 3 groups of 7 animals, implanted on both sides of the jaw. The main objective of this work is to evaluate the ceramic-bone interface. The results obtained were verified through clinical, radiographic and histological exams at the 40th day of the postoperatory time. A fibrous capsule was found in 36% of the cases where ZrO2 was inserted in contraposition with the Al2O3 and the ZrSiO4 where the bone formation was verified in 100 % and 92 % respectively.

Abstract: A key feature in the understanding of the mechanisms of integration of implant materials is a deepened in-sight of the elemental and molecular composition of the interface zone between the implant and tissue. To analyze the interface at the ultrastructural level, transmission electron microscopy (TEM) is needed. However, techniques to fabricate thin foils for TEM are difficult and time consuming. By using focused ion beam microscopy (FIB) for site-specific preparation of TEM-samples, intact interfaces between bioceramics and calcified tissue can be prepared. The site-specific accuracy of the technique is about 1 mm. By using a dual-beam FIB, which is a combined scanning electron and focused ion beam microscope, the sample can be imaged with both electrons and ions (generating both secondary electrons and ions). Results from interface studies between Ca-aluminate based orthopaedic cement, dental materials, HA-coated Ti-implants and bone are presented. The interfaces were imaged in scanning-TEM and bright field mode, the crystal structures were determined using electron diffraction and elemental composition analyzed with energy dispersive spectroscopy. The technique fulfils a demand to correlate the surface properties of bioceramic implants with the structure and composition of preserved interfaces with tissues.

Abstract: To develop a better surface conformation of titanium dental implants, we examined the in vitro biocompatibility of a thin natural apatite (NA) film deposited by laser ablation. Thin (2000-Å) hydroxyapatite (HA) and NA films were deposited on titanium discs using an ArF excimer laser operating at a repletion rate of 10 Hz and annealed by heating at 360°C for 1 h. Energy dispersive analysis of the NA film revealed peaks of Na and Mg in addition Ca and P. X-ray diffraction showed that crystalline HA was present in the HA and NA films. Primary mouse osteoblast grew faster and had higher alkaline phosphatase activity when grown in NA films than on HA films or a bare titanium surface. In addition, osteocalsin production by these cells was higher on HA and NA than bare titanium, but there was no significant difference between cells grown on HA and NA. Thus surface modification with NA film may contribute to successful osteoblast function and differentiation at titanium interface.

Abstract: The conventional concept of dental implants completely lacks odontology. Therefore, the dental implant system is quite different from the gompholic mammalian tooth system. Developmental research on artificial dental roots of the mammalian gompholic system has been carried out by the author successfully for the first time in the world from the viewpoint of odontology. Characteristics of the mammalian tooth system are gompholic and heterodontia with tribosphenic tritubercular molars. The meaning of heterodontia in morphology, i.e., several variations in crown and root shapes in different sites of mammalian jawbones are optimal shapes according to the different tooth functions, i.e., sphenic incisors and canines, and tribosphenic-tritubercular molars. For the optimal shapes of teeth adapted to their functions, the gompholic joint system is inevitable, i.e., fibrous articulation with cementoblasts, ligaments with capillaries, and the alveolar bone proper (socket bone). From this viewpoint, the author has developed artificial dental roots of the heterodontia gompholic system. Integrated research on animal experiments, biomechanical research as well as clinical research, have been carried out. It has been proved by microanalyses, microscopy, and scanning electromicroscopy (SEM) that cementoblasts, the cementum, periodontal ligaments, and the alveolar bone proper (socket bone), develop around artificial roots.