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Beijing Da Xue Xue Bao Yi Xue Ban. 2023 Aug 18; 55(4): 721–728.
Published online 2023 May 10. Chinese. doi: 10.19723/j.issn.1671-167X.2023.04.025
PMCID: PMC10398783

Language: Chinese | English

表面处理对氧化钇和氧化镁稳定的氧化锆种植体晶相及断裂强度的影响

Effects of surface treatment on the phase and fracture strength of yttria- and magnesia-stabilized zirconia implants

丁 茜

北京大学口腔医学院·口腔医院修复科, 国家口腔医学中心, 国家口腔疾病临床医学研究中心, 口腔生物材料和数字诊疗装备国家工程研究中心, 口腔数字医学北京市重点实验室, 北京 100081, Department of Proshodontics, Peking University School and Hospital of Stomatology & National Center for Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices & Beijing Key Laboratory of Digital Stomatology, Beijing 100081, China

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李 文锦

北京大学口腔医学院·口腔医院修复科, 国家口腔医学中心, 国家口腔疾病临床医学研究中心, 口腔生物材料和数字诊疗装备国家工程研究中心, 口腔数字医学北京市重点实验室, 北京 100081, Department of Proshodontics, Peking University School and Hospital of Stomatology & National Center for Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices & Beijing Key Laboratory of Digital Stomatology, Beijing 100081, China

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孙 丰博

清华大学材料学院, 北京 100084, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China

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谷 景华

北京航空航天大学材料科学与工程学院, 北京 100191, School of Materials Science and Engineering, Beihang University, Beijing 100191, China

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林 元华

清华大学材料学院, 北京 100084, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China

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张 磊

北京大学口腔医学院·口腔医院修复科, 国家口腔医学中心, 国家口腔疾病临床医学研究中心, 口腔生物材料和数字诊疗装备国家工程研究中心, 口腔数字医学北京市重点实验室, 北京 100081, Department of Proshodontics, Peking University School and Hospital of Stomatology & National Center for Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices & Beijing Key Laboratory of Digital Stomatology, Beijing 100081, China 北京大学口腔医学院·口腔医院修复科, 国家口腔医学中心, 国家口腔疾病临床医学研究中心, 口腔生物材料和数字诊疗装备国家工程研究中心, 口腔数字医学北京市重点实验室, 北京 100081, Department of Proshodontics, Peking University School and Hospital of Stomatology & National Center for Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices & Beijing Key Laboratory of Digital Stomatology, Beijing 100081, China 清华大学材料学院, 北京 100084, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China 北京航空航天大学材料科学与工程学院, 北京 100191, School of Materials Science and Engineering, Beihang University, Beijing 100191, China x ± s Values with different superscript letters(a, b, c, d) are significantly different ( P < 0.01). Abbreviations as in Table 1 .Y-TZP8.560.017  Control827.3±101.6 a Sandblasting1 162.9±116.5 b Sandblasting and acid etching867.2±171.0 a Mg-PSZ21.680.002  Control458.4±48.7 c Sandblasting294.1±3.3 d Sandblasting and acid etching331.3±26.4 d

3. 讨论

本研究利用氧化镁代替氧化钇来稳定t-ZrO 2 ,通过CAD/CAM加工了Y-TZP和Mg-PSZ两种材料的ZrO 2 试件和种植体。运用喷砂、喷砂加酸蚀的方法进行表面粗化处理,均显著增加了ZrO 2 种植体的表面粗糙度,但对Y-TZP和Mg-PSZ两种材料的ZrO 2 表面晶相结构和种植体断裂强度产生了不同的影响。

3.1. 不同表面处理方法对ZrO 2 表面显微形貌和粗糙度的作用

种植体的表面显微形貌和粗糙度是影响种植体骨结合的关键因素。本研究通过喷砂及喷砂加氢氟酸酸蚀两种表面处理方法均获得了适合于骨结合的中度粗糙(Ra值1~2 μm [ 7 - 8 ] )ZrO 2 表面。微米尺度的表面粗糙结构可显著增加ZrO 2 种植体的表面粗糙度,并增加种植体与骨接触的表面积和骨生长进入种植体表面的机械锁结力,从而促进骨结合 [ 9 ] 。另一方面,通过酸蚀等方法获得的纳米尺度(1~100 nm)表面粗糙结构则可为细胞提供仿生环境,通过增加细胞外基质蛋白吸附、调节细胞表面信号传递而影响细胞在种植体表面的黏附、增殖与分化,促进骨结合 [ 8 , 10 ]

氢氟酸酸蚀法是既往研究报道中运用较多的ZrO 2 酸蚀方法。既往报道表明,5%和9.5%的低浓度氢氟酸溶液对ZrO 2 的表面粗化作用并不明显 [ 11 - 12 ] ,而高浓度(40%)的氢氟酸溶液能够得到较为理想的表面粗化效果 [ 13 - 14 ] 。与既往研究相似,本研究采用喷砂加40%氢氟酸酸蚀的表面处理方法,在Y-TZP种植体表面形成了同时具有微米尺度和纳米尺度的表面显微结构,相比之下,Mg-PSZ种植体表面的孔隙大小、分布欠均匀。

3.2. 表面处理对ZrO 2 晶相结构的影响

由于水分子也是引发ZrO 2 发生晶相转变的因素,即低温老化效应 [ 15 ] ,本研究中为与氢氟酸溶液处理一致,对照组试件采用蒸馏水浸泡1 h,故其表面亦存在少量的m-ZrO 2

X射线衍射图谱( 图 5 )显示,与Y-TZP相比,Mg-PSZ材料t相波峰的半高宽均较小,说明镁元素的掺入使Mg-PSZ的晶粒直径大于Y-TZP [ 16 - 17 ] ,与扫描电镜图像观察的一致。图谱中,表面处理造成Y-TZP材料t相波峰半高宽发生明显变化,主要原因是喷砂使Y-TZP材料表面的晶粒结构变得混乱,晶面间距差异增大,故波峰半高宽增大且不对称。喷砂加酸蚀后Y-TZP表面的m-ZrO 2 百分数较喷砂表面有降低,可能与喷砂后表面能量变高、容易被腐蚀、表面部分m-ZrO 2 被氢氟酸腐蚀脱落有关,也可能与酸蚀造成的相变深度较大,未被X射线衍射检测到有关。

本研究结果显示,Mg-PSZ喷砂及喷砂加酸蚀后无明显相变的原因之一可能是氧化镁的掺入导致材料晶粒结构发生改变,氧化镁对t-ZrO 2 的稳定作用比氧化钇更强,较不容易发生相变。Roy等 [ 18 ] 的研究证实,Mg-PSZ材料在模拟老化后单斜相百分数无显著变化,而同样条件下Y-TZP的单斜相百分数则显著升高。另外,结合失重试验结果及试件表面和横断面扫描电镜图像可见,烧结后Mg-PSZ材料的晶粒直径增大,产生大量孔隙,导致材料的致密性下降,结合强度较低,故而容易剥脱,喷砂的机械力量直接造成了表层材料的剥脱和缺损,因此难以检测到相变以及波峰半高宽的变化。

3.3. 表面处理对ZrO 2 种植体断裂强度的影响机制

氧化钇、氧化镁等稳定剂虽有在室温下维持t-ZrO 2 的作用,但在水分子、温度、压力(如喷砂、打磨)等外界因素影响下t-ZrO 2 仍易转变为m-ZrO 2 [ 15 , 19 ] 。本研究中Y-TZP种植体出现喷砂后断裂强度升高,喷砂加酸蚀后下降的现象。结合物相分析的结果可知,Y-TZP喷砂后部分t-ZrO 2 转变为m-ZrO 2 ,相变会伴随3%~4%的体积膨胀,进而在微裂纹扩展尖端产生压应力,减缓裂纹尖端的应力集中,阻碍裂纹扩展,使ZrO 2 的断裂韧性显著提高,称为应力诱导相变增韧。此外,喷砂处理本身能够在种植体表面形成压应力层,在一定程度上能够阻止裂纹的形成,并减缓表面缺陷转化为裂纹源 [ 20 - 21 ] ,因此,Y-TZP种植体喷砂后断裂强度显著升高。

有研究显示CAD/CAM切削加工过程及表面处理均可增加ZrO 2 的表面缺陷,导致ZrO 2 试件的弯曲强度或疲劳强度显著下降 [ 22 ] 。Egilmez等 [ 23 ] 发现喷砂后ZrO 2 试件弯曲强度增加,而酸蚀处理后弯曲强度显著下降。结合本研究结果可见,喷砂加酸蚀组Y-TZP种植体相变深度大于喷砂组,内部的微裂纹产生较多,因此其断裂强度下降。由此可见ZrO 2 的t-m相变一方面可增加ZrO 2 的疲劳强度或弯曲强度,但相变若持续进展,伴随的体积膨胀可造成大量微裂纹的产生,随裂纹向内部扩展,从而对强度产生不利的影响 [ 24 - 25 ] 。Sanon等 [ 26 ] 认为,t-m相变在单斜晶相层产生压应力,单斜相与四方相的交界面产生拉应力从而产生微裂纹,相变对ZrO 2 强度的影响取决于单斜晶相层中残余压应力的聚集和微裂纹产生之间的相互作用。

本研究中,Mg-PSZ种植体喷砂、喷砂加酸蚀后断裂强度下降,可能的原因为烧结后Mg-PSZ材料内部气孔较多,失重试验结果说明喷砂的机械力量直接造成了表层材料的剥脱和缺损,增加了表面缺陷,导致断裂强度下降。酸蚀处理在一定程度上使喷砂形成的表面缺陷变得平缓,因而断裂强度有一定升高,但仍低于对照组。因此,对于Mg-PSZ种植体而言,表面处理未造成明显相变,表面缺陷占主导作用,导致喷砂、喷砂加酸蚀后断裂强度下降。但因本研究中Mg-PSZ材料为自行制备,制备工艺有待进一步优化,表面处理对优化工艺后Mg-PSZ种植体晶相及断裂强度的影响仍有待探索。

3.4. 临床应用前景及局限性

本研究中的ZrO 2 种植体运用CAD/CAM技术在国内加工制作,并通过加入碱土金属氧化物(氧化镁)代替稀土金属氧化物(氧化钇)作为稳定剂,能够更好地稳定t-ZrO 2 ,减少晶相转变,同时降低了成本。通过进一步改进加工流程和提升材料强度,若能实现早期临床转化,则有望率先开发价格低廉的ZrO 2 种植系统。

本研究的局限性在于,Mg-PSZ材料的加工过程不够完善,晶粒结构较为紊乱,内部缺陷、气孔明显较多,导致Mg-PSZ种植体内部致密性不及Y-TZP种植体,因此断裂强度低于Y-TZP种植体。其原因可能与烧结温度过高有关,导致Mg-PSZ的晶粒尺寸明显增大、分布不均匀且粉体之间气孔变大、变多,从而出现硬团聚现象,导致内部缺陷的产生,力学性能下降 [ 27 ] 。后续研究将探索更合适的烧结温度和控温程序,提高Mg-PSZ的致密度,减小内部缺陷 [ 28 ] 。同时,Mg-PSZ粉体粒径也有待优化,需进一步减小颗粒直径,提升均匀性,以最大限度地降低冷等静压的成坯压力,改善坯体的密度和强度。此外,本研究种植体静力试验的样本量较少,改进加工条件后应增加样本量并进行疲劳试验,明确表面处理对两种材料的ZrO 2 种植体疲劳强度的影响。

综上,喷砂或喷砂加酸蚀处理均可获得中度粗糙的Y-TZP和Mg-PSZ表面。表面喷砂处理能够提高Y-TZP种植体断裂强度,喷砂加酸蚀处理后的断裂强度较喷砂有所下降。对于本研究中制备的Mg-PSZ种植体,表面喷砂和喷砂加酸蚀处理均会降低其断裂强度。

Funding Statement

国家自然科学基金(81671026)、北京市自然科学基金(7192233)、首都卫生发展科研专项(首发2020-2-4104)、北京大学口腔医学院青年科研基金(PKUSS20190110)

Funding Statement

Supported by the National Natural Science Foundation of China (81671026), the Beijing Natural Science Foundation (7192233), the Capital Health Development Research Special Fund (2020-2-4104), and the PKU School of Stomatology for Talented Young Investigators (PKUSS20190110)

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