树脂基覆膜材料对牙根面保护作用的耐久性

田洪琰，于 鹏，袁重阳，张 娓，仇越秀，李德慧，梁新杰，王晓燕△

(1. 北京大学口腔医学院·口腔医院,牙体牙髓科 口腔数字化医疗技术和材料国家工程实验室 口腔数字医学北京市重点实验室，北京 100081； 2. 北京安泰生物医用材料有限公司，北京 100094)



·论著·

树脂基覆膜材料对牙根面保护作用的耐久性

田洪琰1，于 鹏1，袁重阳1，张 娓2，仇越秀2，李德慧2，梁新杰2，王晓燕1△

(1. 北京大学口腔医学院·口腔医院,牙体牙髓科 口腔数字化医疗技术和材料国家工程实验室 口腔数字医学北京市重点实验室，北京 100081； 2. 北京安泰生物医用材料有限公司，北京 100094)

目的：比较树脂基覆膜材料和一步法自酸蚀粘接剂对牙根面保护作用的耐久性。方法：制备人离体后牙牙根试样和牙本质盘试样，表面分别使用PRG Barrier Coat (PRG)和一步法自酸蚀粘接剂Clearfil S3Bond (CS3)处理，去离子水中静置24 h备用。对牙根和牙本质盘试样分别进行:(1)水老化及抗酸脱矿实验：人离体牙牙根试样水老化处理14 d后，在脱矿缓冲液(pH 4.5)中脱矿4 d，扫描电子显微镜观察横断面；(2)牙刷磨损实验：对已覆盖PRG和CS3后的人离体后牙牙本质盘表面进行牙刷磨损，表面粗糙度仪测量磨损深度(Ry, μm), One-Way ANVOA法进行统计分析。结果：PRG和CS3覆膜厚度分别为(47.1±27.3) μm和(5.7±2.1) μm，水老化实验后二者覆膜形态无明显改变，下方牙本质无脱矿。PRG和CS3的磨损深度随牙刷磨损次数增加而加深，PRG组磨损深度小于CS3组(P<0.05)。结论：PRG水老化实验后抗酸蚀脱矿作用和CS3相似，耐牙刷磨损性能优于CS3。

牙根龋；覆膜材料；水老化；耐磨损

随着公众口腔保健意识逐渐增强，老年人牙齿存留数目更多、时间更长,但是生理性增龄、牙周疾病以及创伤性刷牙习惯，导致龈退缩发生率上升，带来牙本质敏感、楔状缺损等问题，增加了老年人剩余牙列患根面龋的风险[1]。2008年第3次全国口腔健康流行病学调查结果显示, 我国65～74岁老年人根面龋患病率为63.6%。

利用树脂基覆膜材料(resin-based coating material, RCM)覆盖并预防早期根面龋，具有微创、高效的特点，逐渐受到临床医生的青睐。根面RCM技术发展于一步法自酸蚀粘接技术[2]，在暴露牙根表面形成薄膜物理屏障，能抵抗牙根表面酸蚀脱矿[3]，并抑制生物膜附着形成[4]，封闭牙本质小管改善牙本质敏感[5]。近年来，新型根面RCM中加入了氟化物成分，加强其防龋作用[6],另外，有研究报告一步法自酸蚀粘接剂操作简便，与牙本质粘接形成混合层，可抑制牙根脱矿[7]。

牙根面覆盖保护作用与RCM材料耐久性密切相关。新型RCM与一步法自酸蚀粘接剂覆盖根面后的耐久性尚未见报道。本研究旨在比较含表面预反应玻璃离子填料(surface pre-reacted glass-ionomer filler，S-PRG filler)的RCM和一步法自酸蚀粘接剂的耐水老化抗脱矿及耐牙刷磨损性能，为根面防护临床策略和新产品研发提供实验依据。

1 材料和方法

1.1 材料

选用树脂基覆膜材料PRG Barrier Coat(PRG)和一步法自酸蚀粘接剂Clearfil S3Bond(CS3)的详细成分及使用方法见表1。

表1 材料组成Table 1 Materials used in this study

Bis-MPEPP, 2,2-bis[(4-methacryloxy polyethoxy) phenyl] propane; Bis-GMA, bisphenol A-bisglycidyl methacrylate; HEMA, 2-hydroxyethyl methacrylate; TEGDMA, triethyleneglycol dimethacrylate; 10-MDP, 10-methacryloyloxydecyl dihydrogen phosphate; S-PRG, surface pre-reacted glass-ionomer.

1.2 覆膜材料的形态学观察

选择3个月内因正畸减数拔除的前磨牙或智齿，用刮治器机械去除软组织和根面牙骨质，抛光后于釉牙骨质界下0.5 mm处双层抗酸指甲油开窗3 mm×3 mm[6]，开窗区以PRG和CS3处理，去离子水中静置24 h后备用。PRG的使用方法：向胶囊内滴入1滴液剂，用毛刷充分混匀10 s，涂布于牙本质表面，静置3 s，光照10 s。CS3的使用方法：摇匀后用小毛刷蘸满粘接剂在牙本质表面涂布20 s，0.1 MPa吹干10 s，光照10 s 。PRG组和CS3组各取8个样本进行观察，每个样本自开窗区中心沿预制沟劈开，扫描电子显微镜(scanning electron microscope,SEM)下观察覆膜形态并测量厚度,每个样本在中心点测1次，在距开窗边缘100 μm处测2次，取均值后进行统计。未使用任何材料的空白根面作为对照组(C组，图1)。

1.3 水老化及抗酸脱矿实验

将1.2小节中制备的牙根样本，根据使用材料和是否水老化(W)分为6组：空白组(对照，C-D)，空白-W组(C-W)，PRG-D组，PRG-W组，CS3-D组，CS3-W组，每组3个样本。将C-W、PRG-W和CS3-W 3组进行水老化处理：单个样本分别置于含45 mL去离子水的离心管中，26 ℃，14 d，期间更换一次去离子水。然后将所有6组样本置入10 mL pH 4.5的脱矿缓冲液[6]，每24 h更换，4 d后样本开窗区横断面用S-4300/4800 SEM(日本Hitachi公司)进行观察。

1.4 牙刷磨损实验

选择3个月内因正畸减数拔除的前磨牙或智齿，制备1.5 mm厚牙本质盘后抛光并冲洗[8]。根据使用材料分为空白组、PRG组和CS3组，每组再根据牙刷磨损次数分为6个组(100、200、300、500、700、1 500 次)， 共18组，每组8个样本。将样本置于自制牙刷磨损机内进行实验[8]，样本表面开窗2 mm×10 mm，铝箔保护边缘，牙刷头压力300 g，频率100 r/min，振幅30 mm，往复式磨损模式。牙刷为中等硬度刷毛(广东三笑公司)， 磨损浆料为去离子水与牙膏(美国高露洁公司)2 g ∶1 g混合物，每组更换。牙刷磨损深度用SJ-400便携式表面粗糙度仪(日本Mitutoyo公司)测量，记录Ry值[9]。每个样本测4次，取均值，使用SPSS 20.0 进行数据统计，单因素方差分析(One-Way ANVOA)，检验标准α=0.05；若方差齐，采用LSD法检验，若方差不齐，则用Dunnett T3 法进行检验。SEM观察磨损后样本的表面形态。

C, control group; PRG, PRG group; CS3, CS3 group. C-1/C-2, PRG-1/PRG-2, CS3-1/CS3-2, before demineralization. 1&2 mean magnifica-tion ×1 000 and ×5 000, respectively. C-D, PRG-D, CS3-D, at pH 4.5 for 4 d (×5 000); C-W, PRG-W, CS3-W, at pH 4.5 for 4 d after 14 d water aging (×5000). D means dentin, PRG means PRG Barrier Coat, CS3 means Clearfil S Bond. Hollow arrows show demineralized dentin tubules; black arrows indicate fillers in PRG; white arrows demonstrate a thin film coating of CS3.
图1 根面保护材料抗酸蚀脱矿的扫描电子显微镜观察
Figure 1 Scanning electron microscope (SEM) of root dentin with coating materials after demineralization

2 结果

2.1 水老化后抗酸蚀脱矿作用(图1)

空白组(C组)开窗区牙本质脱矿凹陷，高倍镜下牙根牙本质小管口大部分开放，小管较细弯，管径约为1～1.5 μm，空白组脱矿后，牙本质小管管口扩大，管径增宽，管壁粗糙不平，管间牙本质厚度变薄，C-W组与空白组相似。

PRG在牙根表面形成连续致密薄膜，厚度为(47.1±27.3) μm，与牙本质结合紧密，界面没有气泡、孔隙等缺陷，PRG组即刻脱矿后覆膜与下方牙本质形态无变化。PRG-W组水老化及脱矿后，覆膜与牙本质结合紧密，下方牙本质无脱矿。

CS3在牙根表面形成连续薄膜，厚度为(5.7±2.1) μm，与牙本质结合紧密，界面无气泡、孔隙等缺陷，CS3组即刻脱矿后覆膜与下方牙本质形态没有任何变化。CS3-W组水老化及脱矿后，覆膜形态无明显变化，与牙本质结合紧密，下方牙本质无脱矿。

2.2 耐牙刷磨损性能

空白牙本质、PRG和CS3的磨损深度均随着牙刷磨损次数的增加而加深(图2)。磨损700次以前，空白组磨损深度最小，CS3组磨损深度最大(P<0.05)；700次之后，磨损深度由大到小依次为CS3组>空白组>PRG组(P<0.01)。空白组、PRG组和CS3组磨损后的表面形态见图3,磨损500次时,空白组的磨损区表面少量不规则划痕，PRG组的磨损区可见显著划痕，少量小而深的孔隙，牙本质无暴露，CS3组的磨损区可见明显划痕，出现裂纹、碎裂和缺损，缺损处可见牙本质暴露。磨损700次时，空白组的磨损区表面划痕密度增加，PRG组的磨损区除划痕外出现大量孔隙，表面基本完整，牙本质无暴露,CS3组的磨损区可见大量牙本质暴露并有划痕存在，表面有极少的CS3残余。磨损1 500次时，空白组的磨损区划痕增宽连成一片，与未磨损区分界处有明显台阶形成，PRG组的磨损区覆膜依然存在，表面出现裂纹、碎裂，牙本质无暴露，CS3组的磨损区CS3完全被磨除，牙本质完全暴露并有大量划痕，与未磨损区分界处形成台阶。

图2 根面保护材料的牙刷磨损深度
Figure 2 Depths of wear of coating materials by brushing cycles

3 讨论

本研究结果显示，新型RCM与自酸蚀粘接剂在牙根面形成的覆膜形态不同，这与二者成分不同密切相关。PRG提高了疏水性树脂单体含量，并且增加了S-PRG填料颗粒，使得材料黏稠度增加。在成膜厚度上，PRG显著厚于CS3。CS3在光固化前需要强气流吹干水分和溶剂，易延展形成薄膜，但是难以保持一定的厚度。有学者提出，在实际操作中，可通过二次涂布适当增加自酸蚀粘接剂覆膜厚度[10]。

PRG和CS3主要通过在牙本质表面覆盖成膜，并封闭牙本质小管，从而隔绝外界物理、化学等有害刺激。PRG与CS3均与牙本质结合紧密，单体渗透进入牙本质形成混合层，有学者研究报告这一结构具有抗酸蚀脱矿的作用[11]。封闭膜的稳定性是提供持久根面保护的关键，然而，一步法自酸蚀粘接剂中亲水性单体成分含量较高，具有一定的吸水性，水可渗透并破坏粘接界面，难以维持长期抗酸蚀脱矿作用[3, 12]。本研究结果显示，自酸蚀粘接剂CS3和新型树脂基覆膜材料PRG水老化14 d后，抗酸脱矿能力与水老化前相似，均可以预防下方牙本质脱矿,其长期耐水老化抗酸脱矿性能仍需进一步研究。

a, control group (dentin); b, PRG group, c, CS3 group. a1, b1, c1, after 500 cycles of brush; a2, b2, c2, after 700 cycles; a3, b3, c3, after 1 500 cycles. N, non-brush area; A, toothbrush abrasion area. White arrows show the strokes of toothbrush wear; black hollow arrows show the pits on PRG surface; white hollow arrows show residual CS3 on dentin surface; black arrows indicate the cracks and defects of materials, and triangle, the visible uncoated dentin.

图3 根面保护材料牙刷磨损后的表面形态SEM观察
Figure 3 SEM of the dentin with coating materials after toothbrush abrasion

树脂基覆膜材料加入填料和功能性单体，除了增加成膜厚度，还提高了覆膜的耐牙刷磨损性能，延长了覆膜材料的根面保护作用寿命。Gando等[13]报道，树脂基覆膜材料添加了3D-SR单体和玻璃离子填料，可经受50 000次牙刷磨损，抗磨损性能显著提高。在临床实际情况中，牙列一年所受到牙刷磨损约为10 000次[14-15]。本研究观察到PRG的耐磨性优于CS3，根据磨损曲线推算，当前实验条件下PRG可经受12 500次以上牙刷磨损，相当于临床条件下1年以上磨损量的水平。本研究还显示，PRG和CS3的磨损模式不同，扫描电镜下体现不同的表面形态。总的来讲，CS3本身填料少，树脂基质强度不如牙本质，所以磨损深度最大；700次磨损之后CS3几乎完全磨除，磨损表面形态与空白组类似。PRG在700次磨损之前，接受磨损的部分主要为较软的树脂基质部分，前期磨损模式与CS3类似；在700次之后，PRG基质磨除一层后暴露硬度高的S-PRG填料颗粒，高出周围基质的填料颗粒受磨损作用从材料表面脱出而形成大量孔隙，但覆膜整体磨损速率减慢了，因此PRG磨损深度显著小于CS3和牙本质，扫描电镜表面形态观察也符合这一点。PRG中的S-PRG填料还能释放氟、锶、硼、钠等离子，兼具氟释放及再补充氟的功能，并能减少生物膜黏附[16-18]。有研究证明，PRG能抑制釉质龋进展，并有较好的长期抗牙本质龋效果[19-21]。

综上所述，树脂基覆膜材料PRG Barrier Coat对牙根面的保护作用具有一定的耐久性，能为暴露根面提供一定防护作用，其实际临床应用效果需要进一步研究。

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(2015-04-25收稿)

(本文编辑：王 蕾)

Durability of protective effect of resin-based coating material on root surface

TIAN Hong-yan1, YU Peng1, YUAN Chong-yang1, ZHANG Wei2, QIU Yue-xiu2, LI De-hui2, LIANG Xin-jie2, WANG Xiao-yan1△

(1. Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing 100081, China；2. AT&M Biomaterial Co., Ltd， Beijing 100094, China)

Objective： To compare the durability of resin-based root-surface coating material and all-in-one self-etching adhesive on root surfaceinvitro. Methods: Human extracted premolars or molars with intact roots were selected. The cementum was removed using a periodontal scaler to expose root dentin.The root surface was coated with an acid-resistant nail varnish, leaving a window of 3 mm×3 mm on the exposed dentin.The window was covered with either PRG Barrier Coat (PRG) or Clearfil S3Bond (CS3). After water aging for 14 d, specimens were immersed in acid buffer at pH 4.5 for 4 d and the demineralization buffer was changed every 24 h. Then the specimen was split longitudinally through the center of the ‘window’ and the cross-sectional surface was observed with scanning electron microscope (SEM). After fixed and dehydrated, the prepared samples were coated with platinum. The coating material, root dentin and the interface was observed by scanning electron microscope (SEM). The thickness of the coating material was measured on the SEM images. Regarding toothbrush wear test, coronal dentindisks were prepared and covered with PRG and CS3, respectively. After storage in water for 24 h, the specimen was subjected to the toothbrush wear tester for 100, 200, 300, 500, 700, 1 500 brushing cycles. A slurry of fluoride toothpaste (1 ∶2 ratio of toothpaste and deionized water by weight) was used and the brushing load was 300 N. The surface microstructure of remaining coating material was analyzed using SEM. The wear depths were determined by a profilometer. Statistical analysis was performed with SPSS 20.0 by one-way ANOVA. The level of significance was at 0.05. Results: Application of PRG Barrier Coat produced a coating layer of (47.1±27.3) μm, while CS3 presented a thin film of (5.7±2.1) μm in thickness. The exposed dentin was hermetically sealed and no obvious gap was observed at the interface in both PRG and CS3 groups. There was no dentin demineralization observed in both groups after water aging. The wear depths of PRG and CS3 increased along with the numbers of brushing cycles. PRG wore at a significant lower pace than CS3 did (P<0.05). Conclusion: PRG coating resin had similar performances as CS3 on protecting root dentin from demineralization after water aging. What’s more, PRG demonstrated a higher toothbrush wear resistance than CS3. We concluded that PRG Barrier Coat contained S-PRG filler may be an effective coating material for protecting exposed root from both chemical and mechanical challenges. Further studies should be carried out to evaluate the long-term reliability of the rootsurface coating materials under the clinical setting.

Root caries; Coating material; Water aging; Wear resistance

北京市科学技术委员会计划项目(Z14110000514016)资助Supported by Beijing Municipal Science & Technology Commission Project (Z14110000514016)

时间：2016-9-5 15：56：36

http://www.cnki.net/kcms/detail/11.4691.R.20160905.1556.048.html

R781.33

A

1671-167X(2016)05-0889-05

10.3969/j.issn.1671-167X.2016.05.026

△ Corresponding author’s email, wangxiaoyan@pkuss.bjmu.edu.cn