The study of UV light to improve the biocompatibility of titanium

• Main Authors: Chang-SyunWu, 吳政勳
• Other Authors: Tzer-Min Lee
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/3jhq7t

碩士 === 國立成功大學 === 口腔醫學研究所 === 102 === SUMMARY For tooth implantation, the specially designed titanium dental implant is embedded into the alveolar bone of the missing tooth to closely connect with the jawbone, which generates the anchoring effect. Nevertheless, if the implant is placed in air for a long time or with inappropriate storage method, it will age biologically with time, and osseointegration will lessen, resulting in the risk of implant loosing. Consequently, with utilization of UV-titanium dioxide photocatalytic reaction, this research has raised the titanium surface for re-activation, called photofunctionalization. Additionally, bioactivity performance of four specimens— Polish, SLA, MAO, and ATO— in four conditions—atmosphere, vacuum, oxygen, and vapor—have been explored. The four specimens have further been soaked in SBF to analyze their calcium-phosphate compound precipitation outcomes. It is found that under vapor condition, the content of amphoteric hydroxyl group in Polish, SLA, and MAO has increased significantly. That is to say, the experimental results have verified that the specimens with different structures in specific photocatalytic environment generate great amount of amphoteric hydroxyl group with high activity, which is beneficial for overcoming the activation energy barriers in nucleation and growth. INTRODUCTION Dental implantation refers to implanting a specially designed titanium artificial tooth root into the alveolar bone of the missing tooth surgically to closely connect and anchor the jawbone. With this dental technology, the patient can not only speak normally as he or she used to do, but also regain the appearance and quality of a healthy tooth. However, if the implant is exposed to the air too long or stored in an inappropriate way; due to biological aging, the implant itself might lower the osseointegration extent, and causes the implant to loosen. Therefore, in the year of 2008, some scholars researched that UV- titanium dioxide photocatalytic reaction used to enable titanium surfaces to enhance the influence of cell adhesion, cell proliferation, and osseointegration in order to make the aged surface active again, which is called photofunctionalization. Unfortunately, when facing certain conditions, most scholars merely discuss the influence of specimen with different surface treatments under atmospheric photocatalytic reaction, but rarely mention the growth and declination of the amphoteric hydroxyl group content. Under this context, this research explores the biological activities of the four different specimen, including Polish, SLA (sandblasted, large-grit, acid-etched), MAO (micro arc oxidation), ATO (anodic titanium oxide) under four conditions involving atmosphere, vacuum, oxygen, and vapor. These four specimens have been soaked in SBF (simulated body fluid) to analyze its calcium-phosphate compound precipitation scenarios. The super oxygen ion (‧O2 －) and‧OH－generated by photocatalytic reaction have shown high resolving power. The highly active substances finally trigger great amount of Ti-OH functional groups to be created by surfaces. And, with this synergistic effect, the calcium-phosphate compound nucleus are provided excellent high energy heterogeneous nucleation sites and growth-driving force. Using Polish, SLA, and MAO specimens under vapor conditions, amphoteric hydroxyl group content shows the tendency of significant increase. Moreover, SLA has also been soaked in SBF for 7 days, causing calcium-phosphate compound to separate out the most obviously at the spinal area bumps and empty cavity where the internal has etched back. The results of the experiment prove that the specimens with different structures under specific photocatalytic environment may create many highly active amphoteric hydroxyl, which is also beneficial to overcome the active energy barrier in nucleation and growth. MATERIALS AND METHODS The experimental material was commercial pure titanium grade 2 F67 cp Ti, and the experiment flow is shown in Fig. 3-1. The Control Group was pure titanium without UV light treatment, while the Contrast Group was UV-vacuum, UV-O2, and UV-H2O proceeded reaction in self-made stainless steel chamber, as shown in Fig. 3-2. In process of photocatalytic experiment, according to Beer's law, the intensity of UV transmission light declined exponentially with the increase of the optical path length. Therefore, in order to achieve good photocatalytic effect, the specimens were placed in parallel to the direction of UV light tubes, and on the same plane of the incident light source, so that the optimal illuminance could be obtained. After the experiment, the specimens were soaked in SBF for 1, 3, and 7 days to complete coating for the subsequent analysis. FE-SEM was used to observe the shape of the specimens’ surfaces, and EDS to determine the elements the specimens contained and conduct semi-quantitative analysis. On the other hand, XRD was exerted to analyze the phase composition, while XPS to analyze the chemical state and valence number of the compound. Finally, we observed the surface energy change by contact angle. RESULTS AND DISCUSSION From Table 4.1, we can learn that the contact angle of all the specimens after UV light treatment is smaller than 100, signifying superhydrophilicity. Besides, in XPS analysis of high resolution O 1s spectra, the content of amphoteric hydroxyl group is higher in the specimens of Polish, SLA, and MAO, and such functional group has provided good nucleation site to induce apatite precipitation. As in high resolution C 1s spectra, from Fig. 4-15 to Fig. 4-18, it is learned that C 1s peak tends to decline with regard to Polish, MAO, and ATO under the vacuum condition. From Fig. 4-24 to Fig. 4-27, the morphology of calcium-phosphate compound precipitation phase change, the apatite is precipitated as heterogeneous nucleation site by means of Ti-OH functional group; and, with even higher multiplying factor, the precipitated apatite is represented as ball-shape, proving it is consistent with our proposed hypothesis. Moreover, in Fig. 4-25, the apatite precipitated in SLA group is the densest—agglomeration even took place, and the precipitated particle size on the ridge and in the internal etch-back holes is the biggest. CONCLUSION 1.This thesis primarily articulates the application of UV photocatalytic reaction in specific environments as Vacuum, O2, and H2O. Particularly, for Polish, SLA, and MAO specimens, H2O is the best condition that can foster the apatite to be precipitated. 2.Under such synergistic effect, when surfaces with different structures are connected with Ti-OH functional group, the high surface energy helps overcome the activation energy barriers in nucleation. Also, it serves as a good heterogeneous nucleation site, and the energy it releases can re-assist the sites with low energy to continue to nucleate. 3.Among the shapes with the fixed volume, the area of the sphere is the smallest. The precipitated apatite is a globe, which has the least total surface energy.