Kihei Kobayashi

Surface analysis of Ti–15Zr–4Nb–4Ta alloy after implantation in rat tibia

A new Ti-15Zr-4Nb4Ta alloy without V was implanted in rat tibiae for 6-48 weeks. The new bone formation surrounding the Ti implant in bone marrow, surface analysis of the Ti alloy after implantation, and metal concentrations in dried bone tissue containing new bone were investigated. New bone was well formed around the Ti-15Zr-4Nb-4Ta alloy implanted in bone marrow. The mean thickness of the new bone increased up to 24 weeks after implantation, and changes in the mean thickness thereafter, up to 48 weeks. were very small. The number of corrosion pits observed in the Ti-6Al-4V extra low interstitial (ELI) alloy surface tended to be slightly more than that of the Ti-5Zr-4Nb-4Ta alloy implant. The concentrations of metal elements in the bone tissue containing the new bone tended to increase slightly more than in bones without the implant.

H2O2-derived free radicals treated fibronectin substratum reduces the bone nodule formation of rat calvarial osteoblast

Fibronectin (FN) is involved in various cellular activities such as adhesion, proliferation and migration as a substratum. Since the metabolic turnover of FN is much slower than other cellular components, it may be affected by the oxygen free radicals produced in the aging process. However, the effect of oxygen free radicals on FN as substratum in bone formation has not been well characterized. The objective of this study was to examine the effect on the bone forming activity of osteoblasts using an oxygen free radical treated FN substratum in vitro (H2O2-Cu2+system). SDS-PAGE, Western blotting and immuno-blotting analysis revealed that FN was degradated and/or modified by H2O2-Cu2+ (.OH) treatment. Bone nodule formation per well was examined for total number, total area and area per nodule, which data were then compared between non-coated and FN-coated, and between FN-coated and .OH treated FN-coated. Bone nodule formation in the FN-coated was significantly greater than in the non-coated. Furthermore, bone nodule formation in .OH treated FN-coated was significantly less than that of FN-coated. These findings suggested that FN plays important roles in osteoblast activity and that FN substratum damaged by the oxygen free radicals produced by the aging process may cause decline of bone nodule formation through inhibition of the proliferation, differentiation and calcification processes.

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.

Investigation on how renewal of complete dentures impact on dietary and nutrient adequacy in edentulous patients

PURPOSE The aim of this study is to investigate changes of diet and nutrient adequacy between complete denture wearers with their existing dentures and those with new dentures. METHODS After obtained their written informed consent 30 patients who visited Nihon University School of Dentistry at Matsudo Affiliated Hospital from March 2004 to November 2005 were asked to record their 3 consecutive days meals and to take a picture of them. Furthermore, foods which they can eat with their dentures were examined the questionnaire developed by Hirai. Referring to the obtained records and pictures, one dietitian interviewed to confirm the exact intakes of meals. In addition, the masticatory ability was calculated using the questionnaire. The nutrient adequacy and masticatory score determined at the time of the first and second survey were examined by repeated-measures ANOVA. A p-value less than 0.05 was considered statistically significant. RESULT The total intake of energy and nutrients was almost over 100% in both the groups. However, no statistically significant difference was obtained. The masticatory score with the existing and new denture were 66.1+/-18.5 and 58.3+/-19.9, respectively. The score increased significantly in the new denture group when compared with that of the existing denture group. CONCLUSION The self-evaluation of the masticatory function improved after the switch from the old to new dentures.

Variation in Composition of Bone Surrounding Implants

Our studies previously demonstrated that new bone formed around implants can be classified into 3 or 4 types based on tissue structure and composition. Results of the present study, using polarized light microscopy, and microscopic Fourier transform infrared spectroscopic imaging (micro-FT-IR) and micro-XRD to examine different areas in the peri-implant new bone, suggest differences in crystallinity (crystal size) between pre-existing bone and peri-implant new bone.

The use of existing denture-satisfaction ratings for a diagnostic test to indicate prognosis with newly delivered complete dentures

PURPOSE The study investigated the relation between subjective satisfaction ratings of existing dentures and outcomes of newly delivered dentures, and the ability of the diagnostic test, using existing ratings, to indicate prognosis with newly delivered dentures. METHODS Consecutive 165 edentulous patients were recruited from November 2001 to August 2006 at a university-affiliated hospital. Dentures were fabricated with an acrylic base with full-balanced occlusion using hard resin artificial teeth by multiple prosthodontists. At the baseline and 3-month after delivery, patients rate their overall, maxillary, and mandibular satisfaction for existing and replaced dentures on a 100-mm visual analogue scale (VAS). The association between baseline ratings and newly delivered dentures was analyzed by regression analysis. The tests performance was measured by constructing a two-by-two table; patients with the following cutoff values on the VAS (overall: <or=31; maxillary: <or=47; mandibular: <or=36) were considered unsatisfied with existing or new dentures. Relative validity of the diagnostic tests was assessed by means of sensitivity, specificity, and likelihood ratios. RESULTS Mandibular dentures showed a significant association between baseline and new dentures (coefficient=0.27, p=0.01). Results of test measures for overall, maxillary, and mandibular existing dentures were 71%, 38%, and 87% (sensitivity); 62%, 66%, and 49% (specificity); and 1.1, 1.9, and 1.7 (positive likelihood), and 0.5, 1.0, and 0.2 (negative likelihood). CONCLUSIONS Test performance indicates that the negative (satisfied) result for mandibular existing dentures may be useful to rule out the unsatisfied patients with new mandibular dentures.

Observation of Newly Formed Bone Around Dental Implants Using Parametric X-ray

The purpose of this study is to determine the potential of the LEBRA-PXR imaging in investigating the details of newly formed bone around the dental implants. Transmission image observation of the undecalcified specimen at the wavelength of 1.771 Å showed clearly the formation of immaturely calcified new bone around the dental implants which could not be observed in the usual CMR nor conventional X-ray imaging apparatus.

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.

Development and Validation of Denture Acceptance Scale (DAS) to Measure an Intention towards Denture Wear

目的: 本研究は, 患者個々の義歯装着の意志を把握することを目指し, 質的検討および小規模調査にて作成された改良型質問票を用いて多施設調査を行い, その信頼性および構成概念妥当性ならびに収束妥当性から, 最終質問票の質問項目を検討することが目的である.方法: 日本大学松戸歯学部付属歯科病院および近隣歯科診療所に来院した318名を対象に, 改良型質問票を用いて多施設調査を行った. 因子分析にて質問項目の構成を, クロンバックのα係数より, 構成概念妥当性および内的信頼性を検討した. 収束妥当性は義歯装着の意志を測る外的基準項目と最終質問票との関連について, それぞれの回答値よりPearson相関係数を算出し検討した.結果: 検討の結果, 最終的に4因子 (第I因子「気持ち」, 第II因子「不快事項」, 第III因子「全身状態」, 第V因子「対人関係」) 37質問項目が構成され, クロンバックのα係数は0.59-0.91となった. 義歯装着の意志と最終質問票との間には, 上顎義歯装着の意志と上下顎局部床義歯装着者 (r=0.30), 下顎義歯装着の意志と片顎義歯 (r=0.28), 上下顎局部床義歯 (r=0.33), 上下顎総義歯装着者 (r=0.30) の回答値との間に有意な関連を示した.結論: 4因子37質問項目よりなる最終質問票は, 妥当な構成概念, 内的信頼性および識別妥当性を有し, 今後の臨床応用の可能性が示された.

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.