Yasuko Numata

Early Tissue Response to Modified Implant Surfaces Using Back Scattered Imaging

Purpose:It is now well known that implant surface properties affect osseointegration. Grit-blasting with abrasives and coating by plasma are methods to modify implant surfaces. This study aimed to compare the direction of new bone formation associated with three types of surfaces. Materials and Methods:Titanium (Ti) alloy rods grit-blasted with alumina abrasive (Group 1, G1), with apatitic abrasive (Group 2, G2), and with apatitic abrasive and plasma-sprayed with hydroxyapatite (Group 3, G3) were implanted in surgically created defects in tibias of New Zealand white rabbits for 2 and 4 weeks. After sacrifice, the implants and surrounding bones were obtained and analyzed using back scattered imaging. Results:Differences in patterns of bone formation among the groups were observed: originating from the cortical bone towards the implant surface (Type A), surrounding the implant (Type B) and originating from the medullary cavity (Type C). G1 and G3 showed Types A and B while G2 exhibited Types A, B and C. After 4 weeks, greater amount of new bone was observed in G2 group compared with those in G1 and G3 groups. Conclusions:This study demonstrated that patterns of bone formation are influenced by methods of surface modification.

Qualitative and Quantitative Evaluation of Bone and Synthetic Calcium Phosphates Using Raman Spectroscopy

The purpose of this study was to evaluate synthetic calcium phosphates and animal bones using Raman spectroscopy and explore the possibility of its application in characterizing newly formed bone around implants. Synthetic calcium phosphates (monobasic calcium phosphate, dibasic calcium phosphate, tribasic calcium phosphate, fiber apatite, hydroxyapatite and carbonate hydroxyapatite) and animal bones (from pig, cow, rabbit with and without implants) were analyzed in this study. Slight differences in the Raman bands among the 7 types of synthetic calcium phosphate were observed. Furthermore, a 3 cm-1 difference was noted in the bands of the main PO4 3- in rabbit’s bone formed around the implant, compared to the existing bone, suggesting a difference in the molecular structure between the existing and newly formed bones.

Newly Formed Bone around Implanted New Titanium Alloy: Ti-15%Zr-4%Nb-4%Ta

We have developed a new Ti alloy, Ti-15%Zr-4%Nb-4%Ta alloy (Ti-15-4-4) that showed higher biological safety and mechanical properties than the currently used Ti-6%Al-4%V alloy. The purpose of this study is to determine the biological performance of the new alloy. Ti-15-4-4 implants (machined or blasted) were placed in surgically created defects in rabbit femurs. The rabbits were sacrificed after 4, 8, 16, 24 and 48 weeks. Bone mineral density (BMD) and area of newly formed bone around the implants were measured using micro-CT. Results showed that the Ti-15-4-4 alloy is biocompatible and forms new bone around the Ti-15-4-4 implant, regardless of the surface treatment. The BMD and area of newly formed bone around the blasted implant surfaces were significantly greater than those around the machined surfaces. These results indicate that the new Ti-15-4-4 alloy has a potential for use as implants and has the advantage of improved mechanical properties described in earlier studies.

Quantitative Micro-Radiography of New Bones Formed around the Implant Using Parametrics X-Ray

To clarify new bone tissues, radiography with a newly developed tunable wavelength and highly parallel Parametric X-ray, PXR, was applied. Methods: PXR was generated by a LINAC at LEBRA, Nihon University (Hayakawa et al., 2005). X-ray wavelength was tuned from 7 KeV, 0.177 nm, to 16 KeV, 0.0775 nm. Coated or grit-blasted Ti-alloy implants modified with coating or blasting were implanted in surgically created defects in rabbit tibia. Undecalcified polished thin sections were prepared from the implant/bone areas 1 and 4 weeks after implantation. Results: PXR radiography showed a distinct difference between the newly formed bone and the compact bone. Color-mapping of the images showed an increase in the total amount of bone formation with time. Conclusion: Application of LEBRA-PXR, a high-powered, highly monochromatized and highly parallel oriented X-ray allowed easy and accurate radiographic analysis of new bone formation around the implant.