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Masaharu Nakagawa Last modified date:2019.07.11

Associate Professor / Department of Biomaterials, Faculty of Dental Science
Department of Dental Science
Faculty of Dental Science


Graduate School
Undergraduate School


E-Mail
Phone
092-642-6331
Fax
092-642-6331
Academic Degree
Doctor of Philosophy (Dental Science)
Field of Specialization
Dental materials, Biomaterials
Outline Activities
"Surface modification of titanium implant with quick osteointegration"
Titanium is used as implant materials widely in a medical department, a field of dentistry to have superior biocompatibility. After implantation, as for the titanium implant, early osseointegration, strong osseointegration are demanded from a bone. Therefore many surface reforming methods are studied and get the high success rate. However, it is fear to lead to failure of implant operation because it needs several months for osseointegration and external force at present. In our laboratory, I developed the treatment method (Calcium chloride hydro-thermal-treatment) that strong osseointegration was provided at a speed that several times was fast in comparison with a past surface treatment method. As a result, I can get strong osseointegration from an early stage of implantation, and the period of the operation is shortened, and it is expected that failure by the initial external force (slight movement) to occur after implant decreases remarkably.

"The influence on person of titanium implant wearing with the fluoride component toothpaste. Development of the dental titanium alloy having and high corrosion resistance"
In dentistry, fluoride containing the tooth embrocations, a mouth wash and the toothpaste for the caries prevention positively. Fluorine of 1,000ppm is included in a commercial toothpaste. For an intake of existence of the plaque and the acid drinking water, other causes, titanium may corrode when titanium were insertion in the oral cavity. When such a condition continues for many years, minute corrosion progresses and becomes the cause that cavity and surface roughness weather are produced on the titanium surface. Traces of the corrosion were really confirmed to an oral titanium implant removed from the the oral cavity. Because cleaning becomes difficult, and it is thought that it is a risk to cause periimplantitis when the titanium surface becomes the rough surface, it is thought that it is desirable as possible for a person of wearing of the titanium implant to use the toothpaste which does not contain fluoride.
 
"Effect of Fluoride Concentration and pH on Corrosion Behavior of Titanium for Dental Use"
Titanium is used as a metal for biocompatible materials such as the dental implant or restorations because of an excellent chemical stability. However, the corrosion of Ti in prophylactic fluoride-containing environment comes into a problem. To clarify the effect of fluoride concentration and pH on the corrosion behavior of Ti, anodic polarization tests and immersion tests were carried out in NaF solution of various concentrations and pH values. The concentrations of dissolved Ti in the test solutions were analyzed by inductively coupled plasma mass spectroscopy. There were obvious limits of fluoride concentration and the pH value at which the corrosion behavior of Ti changed. The corrosion of Ti in the solution containing fluoride depended on the concentration of hydrofluoric acid (HF). When the HF concentration in the solution was higher than about 30 ppm, the passivation film of the Ti was destroyed. The results of this study revealed a relation between fluoride concentrations and pH values at which corrosion of Ti took place and provided information whether Ti is corroded or not, if the fluoride concentration and pH value are known in the concerned environment.
"Effect of Fluoride and Dissolved Oxygen Concentrations on the Corrosion Behavior of Pure Titanium and Titanium Alloys", Dental Materials Journal, Vol.21, 83-92, 2002 won a prize for dental engineering meeting article in Japan in 2002.

"Computer simulation of the corrosion behavior of the dental alloy"
We built a metal crystal model in a computer consisting of the Au, Ag, Cu, Pd which were the base component of the dental noble metal alloy. We devised the model that considered the surface rearrangement phenomenon of the noble metal element which remained behind in the alloy surface without desolving interatomic interactivity as well as the standard electrode electric potential of each atom for probability when each atom eluted it by corrosion and simulated the corrosion behavior. As a result, in all such as the density profile of each element, the dynamic polarization behavior alloy composition dependence, polarization voltage dependency and the surface around after polarizing it quantity of elution by potentiostatic polarization test, the result of the simulation reproduced laboratory findings well.
Research
Research Interests
  • Research on osteo-conduction giving of titanium implant by ozon calcium treatment.
    keyword : Titanium, implant, osteocondictive, surface modification, ozon tretament
    2010.03~2014.03"Surface modification of titanium implant with quick osteointegration" As it has outstanding corrosion resistance and biocompatibility, Ti is widely applied in orthopedics and dentistry as a replacement material for hard tissue. When Ti for mouth implants is embedded in the jawbone, bone is formed at the perimeter and bonding to bone occurs, but it usually takes 1-2 months for bone to form and the implant to become fixed. Therefore, during this period, it is important not to apply unnecessary force to the implant and to beware of infection. Even after osteointegration, if a strong force acts on the implant, separation may occur in the part bonded to bone and worsen the prognosis. In order to improve this, it is necessary that the implant bonds with the bone quickly, and that the bond is firm. In this study, in order to generate a quick bone-like apatite, the surface modification method of titanium is developed..
  • Development of osteoconductive titanium and titanium alloys implants with high bone bonding strength.
    keyword : Titanium, implant, apatite, osteocondictive, surface modification
    2005.04"Surface modification of titanium implant with quick osteointegration" As it has outstanding corrosion resistance and biocompatibility, Ti is widely applied in orthopedics and dentistry as a replacement material for hard tissue. When Ti for mouth implants is embedded in the jawbone, bone is formed at the perimeter and bonding to bone occurs, but it usually takes 1-2 months for bone to form and the implant to become fixed. Therefore, during this period, it is important not to apply unnecessary force to the implant and to beware of infection. Even after osteointegration, if a strong force acts on the implant, separation may occur in the part bonded to bone and worsen the prognosis. In order to improve this, it is necessary that the implant bonds with the bone quickly, and that the bond is firm. In this study, in order to generate a quick bone-like apatite, the surface modification method of titanium is developed..
  • Development of dental titanium alloy with high-corrosion resistance
    keyword : titanium, titanium alloys, corrosion, fluoride, dental titanium, implant
    1999.01"Development of high corrosion resistance titanium alloys in fluoride-containing environment" The effects of dissolved-oxygen concentration and fluoride concentration on the corrosion behaviors of commercial pure titanium, Ti-6Al-4V and Ti-6Al-7Nb alloys and experimentally produced Ti-0.2Pd and Ti-0.5Pt alloys were examined using the corrosion potential measurements. The amount of dissolved Ti was analyzed by inductively coupled plasma mass spectroscopy. A decrease in the dissolved-oxygen concentration tended to reduce the corrosion resistance of Ti and Ti alloys. If there was no fluoride, however, corrosion did not occur. Under low dissolved-oxygen conditions, the corrosion of pure Ti and Ti-6Al-4V and Ti-6Al-7Nb alloys might easily take place in the presence of small amounts of fluoride. They were corroded by half or less of the fluoride concentrations in commercial dentifrices. The Ti-0.2Pd and Ti-0.5Pt alloys did not corrode more, even under the low dissolved-oxygen conditions and a fluoride-containing environment, than pure Ti and Ti-6Al-4V and Ti-6Al-7Nb alloys. These alloys are expected to be useful as new Ti alloys with high corrosion resistance in dental use..
  • The effect of the fluorine concentration, the pH, and concentration of dissolved oxygen on the corrosion behavior of titanium and titanium alloy.
    keyword : titanium, titanium alloy, corrosion, floride, dessolved oxygen, dentifrice
    1999.01"Effect of Fluoride Concentration and pH on Corrosion Behavior of Titanium for Dental Use" Titanium is used as a metal for biocompatible materials such as the dental implant or restorations because of an excellent chemical stability. However, the corrosion of Ti in prophylactic fluoride-containing environment comes into a problem. To clarify the effect of fluoride concentration and pH on the corrosion behavior of Ti, anodic polarization tests and immersion tests were carried out in NaF solution of various concentrations and pH values. The concentrations of dissolved Ti in the test solutions were analyzed by inductively coupled plasma mass spectroscopy. There were obvious limits of fluoride concentration and the pH value at which the corrosion behavior of Ti changed. The corrosion of Ti in the solution containing fluoride depended on the concentration of hydrofluoric acid (HF). When the HF concentration in the solution was higher than about 30 ppm, the passivation film of the Ti was destroyed. The results of this study revealed a relation between fluoride concentrations and pH values at which corrosion of Ti took place and provided information whether Ti is corroded or not, if the fluoride concentration and pH value are known in the concerned environment..
  • Development of carbonate apatite block and porous ceramics bone-filling material as bone substitute material
    keyword : apatite, carbonate apatite, bone substitute material
    2002.01~2013.03"Development of the carbonate apatite as a hard tissue substitution materials and a porosity ceramic bone filler" The carbonate apatite attracts attention as a biomechanical material which is excellent in bone absorption property. Generally, although sintering gives strength and form, there is evil of a part of carbonate leaves during sintering. Then, in this study, the method of creating a hardening product, without sintering is developed. Moreover, a porosity sintering product is created from calcium phosphate powder (hydroxyapatite, alpha-TCP, etc.), and the porosity ceramic bone filler with osteoconductivity is developed..
Academic Activities
Reports
1. Problem of Corrosion with Fluoride of the Titanium Implants: Precommendation from Basic Research.
Papers
1. Le Thi Bang, Giichiro Kawachi, Masaharu Nakagawa, Melvin Munar, Kunio Ishikawa, Radzali Othman, The use of poly (ε-caprolactone) to enhance the mechanical strength of porous Si-substituted carbonate apatite, Journal of Applied Polymer Scince, 10.1002/app.39164, 130, 426-433, 2013.03, Poly(e-caprolactone) (PCL)/silicon-substituted carbonate apatite (Si-CO3Ap) composite derived from the interconnected
porous Si-CO3Ap reinforced with molten PCL was prepared. PCL was used to improve the mechanical properties of a porous apatite
by a simple polymer infiltration method, in which the molten PCL was deposited through the interconnected channel of porous
Si-CO3Ap. The PCL covered and penetrated into the pores of the Si-CO3Ap to form an excellent physical interaction with Si-CO3Ap
leading to a significant increase in diametral tensile strength from 0.23 MPa to a maximum of 2.04 MPa. The Si-CO3Ap/PCL composite
has a porosity of about 50–60% and an interconnected porous structure, with pore sizes of 50–150 lm which are necessary for
bone tissue formation. These results could pave the way for producing a porous, structured biocomposite which could be used for
bone replacement..
2. Xingling Shi, Masaharu Nakagawa, Lingli Xu, Alireza Valanezhad, Preparation of Magnesium Containing Bioactive TiO2 Ceramic Layer on Titanium by Hydrothermal Treatment, Advances in Bioceramics and Porous Ceramics, 10.1002/9781118217504, 5, 85-89, 2013.03, [URL], Surface modification on titanium was carried out in order to improve its bioactivity. Pure titanium was hydrothermally treated in distilled water and 0.1 M MgCl2 solutions at 200C for 24 h. Surface morphology, roughness, wettability and chemical composition were characterized before and after treatment. Bovine serum albumin was used as model to study protein adsorption. MC3T3-E1 cells were cultured and initial cell attachment, morphology, proliferation were evaluated. After hydrothermal treatment, nano-sized precipitations were observed and samples showed superhydrophilicity. Magnesium (Mg) was immobilized into titanium surface by hydrothermal treatment.
Protein adsorption was significantly increased on Mgcontaining samples. Cell attachment was improved and cell spreading was enhanced on Mg-containing samples compared with untreated or those treated in distilled water.
Increased early cellular attachment on the MgTi surface resulted in subsequent increase of number of proliferated cells. Hydrothermal treatment in MgCl2 solution was expected to be an effective method to fabricate titanium implant with good bioactivity..
3. Xingling Shi, Masaharu Nakagawa, Giichiro Kawachi, Lingli Xu, Kunio Ishikawa, Surface modification of titanium by hydrothermal treatment in Mg-containing solution and early osteoblast responses, J Mater Sci: Mater Med, 10.1007/s10856-012-4596-4, 23, 1281-1290, 2012.03, [URL], Surface modification on titanium was carried out in order to improve its bioactivity. Pure titanium was hydrothermally treated in distilled water and 0.1 M MgCl2 solutions at 200C for 24 h. Surface morphology, roughness, wettability and chemical composition were characterized before and after treatment. Bovine serum albumin was used as model to study protein adsorption. MC3T3-E1 cells were cultured and initial cell attachment, morphology, proliferation were evaluated. After hydrothermal treatment, nano-sized precipitations were observed and samples showed superhydrophilicity. Magnesium (Mg) was immobilized into titanium surface by hydrothermal treatment.
Protein adsorption was significantly increased on Mgcontaining samples. Cell attachment was improved and cell spreading was enhanced on Mg-containing samples compared with untreated or those treated in distilled water.
Increased early cellular attachment on the MgTi surface resulted in subsequent increase of number of proliferated cells. Hydrothermal treatment in MgCl2 solution was expected to be an effective method to fabricate titanium implant with good bioactivity..
4. Masaharu Nakagawa and Jyunichi Yamazoe, Effect of CaCl2 hydrothermal treatment on the bone bond strength and osteoconductivity of Ti–0.5Pt and Ti–6Al–4V–0.5Pt alloy implants, Journal of Materials Science: Materials in Medicine, 10.1007/s10856-009-3799-9, 20, 11, 2295-2303 , 2009.11.
5. Yoshinari Matono, Masaharu Nakagawa, Kunio Ishikawa, Yoshihiro Terada, Effect of Corrosion Behavior of Pure Titanium and Titanium Alloy on Fluoride Addition in Acidic Environment by Streptococcus mutans, Prosthodont Research & Practice, Vol.7, p34-39, 2008.01.
6. J. Yamazoe, M. Nakagawa, Y Matono, A. Takeuchi, K. Ishikawa, The Development of Ti Alloys for Dental Implant with High Corrosion Resistance and Mechanical Strength, Dental Materials Journal, Vol. 26(2), 260-267, 2007.03.
7. Matono, Y., Nakagawa, M., Matsuya, S., Ishikawa, K., Terada, Y., Corrosion Behavior of Pure Titanium and Titanium Alloys in Various Concentration Acidulated Phosphate Fluorides (APF) Solutions, Dental Materials Journal, Vol. 25, No.1, 104-112, 2006.03.
8. Nakagawa, M., Zhang, L., Udoh, K., Matsuya, S., Ishikawa, K., Effects of hydrothermal treatment with CaCl2 solution on surface property and cell response of titanium implants, J Mater Sci, Materials in Medicine, 10.1007/s10856-005-4753-0, 16, 11, 985-991, vol.16, No.11, p985-991, 2005.11.
9. Nakagawa, M., Matono, Y., Matsuya, S., Udoh, K., Ishikawa, K., The effect of pt and pd alloying additions on the corrosion behavior of titanium in fluoride-containing environments, Biomaterials, 10.1016/j.biomaterials.2004.07.022, 26, 15, 2239-2246, 26(15), p2239-2246, 2005.06.
10. Melvin L. Munar, Koichi Udoh, Masaharu Nakagawa, Shigeki Matsuya, Kunio Ishikawa, Masamichi Ohishi, Effects of Sintering Temperature on the Physical Properties of a-Tricalcium Phosphate Foam Aimed for Bone Defect Substitute, Archives of BioCeramics Research, vol.3、pp200-205, 2003.11.
11. Zhang Lei, Masaharu Nakagawa, Koich Udoh, Shigeki Matsuya, Kunio Ishikawa, Effect of surface modifications on the bioactivity of titanium for dental implants, Archives of BioCeramics Research, vol.3、pp158-163, 2003.11.
12. Yoshinari Matono, Masaharu Nakagawa, Koich Udoh, Shigeki Matsuya, Kunio Ishikawa, Yoshihiro Terada, Changes in corrosion behavior and surface conditions of titanium and Ti alloys for dental use, Archives of BioCeramics Research, vol.3、pp254-258, 2003.11.
Presentations
1. Problem of the corrosion with fluoride of the Ti implant
Proposal from fundamental researches
.
2. Fibroblasts Attachment to CaCl2 Hydrothermally Treated Titanium Implant.
3. Fabrication of bioactive polyethylen terephthalate (PET) substrates by ozone-calcium treatment.
4. Surface modification of polyethylene terephthalate (PET) substrates for biomedical application by ozone-calcium chloride treatment.
5. Surface modification of PET substrates with ozone-calcium treatment.
6. Studies on Improving Osteoconductivity of Titanium by Hydrothermal Treatment.
Awards
  • Preperation of carbonate apatite monolith from bardened vaterite-gypsum by hydrothermal treatment in sodium phosphate.
  • Corrosion behavior of titanium and titanium alloys in simulated oral environment.
  • Fabrication of carbonated apatite monolith by treatment of calcium carbonate in phosphate solutions.
  • Effect of Fluoride and Dissolved Oxygen Concentrations on the Corrosion Behavior of Pure Titanium and Titanium Alloys.
Educational
Educational Activities
It takes charge of the lecture and practice of dental materials science and engineering in faculty education.
Direction of research and experiment of graduate students in graduate school education.
It takes charge of the lecture of bionics at the graduate school education.
Other Educational Activities
  • 2019.05.
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Social
Professional and Outreach Activities
I was doing a joint research concerning the cellular adhesion of calcium modification titanium with Department of Biomaterials Science, Baylor College of Dentistry, USA. .