• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    A General Strategy for Efficiently Constructing Multifunctional Cluster Fillers Using a Three-Fluid Nozzle Spray Drying Technique for Dental Restoration

    2022-04-24 03:23:12DanLeiYangDanWangHaoNiuRuiLiWangMeiLiuFeiMinZhangJieXinWangMeiFangZhu
    Engineering 2022年1期

    Dan-Lei Yang, Dan Wang, Hao Niu, Rui-Li Wang, Mei Liu, Fei-Min Zhang, Jie-Xin Wang,*,Mei-Fang Zhu

    a State Key Laboratory of Organic–Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029, China

    b Research Center of the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, Beijing 100029, China

    c State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China

    d Jiangsu Key Laboratory of Oral Diseases, Department of Prosthodontics, Affiliated Hospital of Stomatology, Nanjing Medical University, Nanjing 210029, China

    Keywords:Multifunctional cluster fillers Three-fluid nozzle spray drying Mechanical properties Antibacterial activity Radiopacity Dental resin composites

    ABSTRACT Multifunctional fillers are greatly required for dental resin composites(DRCs).In this work,a spray dryer with a three-fluid nozzle was applied for the first time to construct high-performance complex nanoparticle clusters(CNCs)consisting of different functional nanofillers for dental restoration.The application of a three-fluid nozzle can effectively avoid the aggregation of different nanoparticles with opposite zeta potentials before the spray drying process in order to construct regularly shaped CNCs. For a SiO2–ZrO2 binary system,the SiO2–ZrO2 CNCs constructed using a three-fluid nozzle maintained their excellent mechanical properties ((133.3±4.7)MPa, (8.8±0.5)GPa, (371.1±13.3)MPa, and (64.5±0.7)HV for flexural strength, flexural modulus, compressive strength, and hardness of DRCs, respectively), despite the introduction of ZrO2 nanoparticles, whereas their counterparts constructed using a two-fluid nozzle showed significantly decreased mechanical properties. Furthermore, heat treatment of the SiO2–ZrO2 CNCs significantly improved the mechanical properties and radiopacity of the DRCs.The DRCs containing over 10%mass fraction ZrO2 nanoparticles can meet the requirement for radiopaque fillers.More importantly, this method can be expanded to ternary or quaternary systems. DRCs filled with SiO2–ZrO2–ZnO CNCs with a ratio of 56:10:4 displayed high antibacterial activity(antibacterial ratio>99%)in addition to excellent mechanical properties and radiopacity. Thus, the three-fluid nozzle spray drying technique holds great potential for the efficient construction of multifunctional cluster fillers for DRCs.

    1. Introduction

    The rapid development of nanotechnology is facilitating the exploration and application of nanomaterials in novel tools for a wide variety of applications, such as energy[1],catalysts[2],electronics[3,4],biomedicine[5–7],and the environment[8].In particular, the biomedical applications of nanomaterials have attracted broad attention due to the unique and advantageous properties of such materials. Nowadays, dental cavities are one of the most common oral diseases.Tooth decay results in the formation of cavities in the teeth, and the enamel cannot regenerate once it becomes worn or eroded [9]. Without effective treatment, caries can progress until the teeth are destroyed [10]. Hence, reliable and versatile restoration materials are greatly required.Resin composites have been widely used in recent years for treating dental caries due to their numerous advantages, such as esthetics, biocompatibility, mechanical properties, and operability [11].

    The main components in dental resin composites (DRCs) are organic matrices and inorganic fillers.The organic matrices,which mainly comprise polymerizable monomers and photoinitiators,can be converted from a liquid phase into a highly crosslinked polymer by being exposed to visible light [12]. Different inorganic fillers have various functions,such as enhancing mechanical properties,reducing polymerization shrinkage,altering thermal expansion behavior, and endowing DRCs with remineralization,radiopacity, and antibacterial abilities [13–16]. The type, size,shape,and structure of the inorganic fillers are the decisive factors in establishing the properties of DRCs [17–21].

    The most commonly used inorganic fillers are reinforcing fillers,such as SiO2and glasses,which are essential for nearly all commercial DRCs. These hard and chemically inert fillers are dispersed in organic matrices to provide the necessary structural reinforcement for clinical applications [22]. Although DRCs loaded with reinforcing fillers have been widely used to treat dental caries, secondary caries cannot be avoided at the tooth-restoration interfaces; this is one of the major reasons for restoration failure and results in 50%–70% failed restorations out of all restorations that are placed[23]. Therefore, antibacterial materials, such as fluorides, silver(Ag)-related fillers, and ZnO nanoparticles, have been adopted as co-fillers to give DRCs antibacterial activity [24–26]. Furthermore,dental clinics require DRCs to have radiopacity,which allows dentists to easily differentiate a restoration from a decayed tooth,evaluate voids, identify inappropriate contour in restorations, and diagnose secondary caries around the restorations [27]. Radiopacity can be achieved by incorporating an element with a relatively high atomic weight (e.g., Zr, Sr, or Ba) as the co-filler in DRCs[28]. According to the various requirements for DRCs, fillers with different functions must be embedded into DRCs to achieve multifunctional restorations. However, the direct addition of functional co-fillers may detrimentally affect the mechanical properties of DRCs due to incompatibility between the fillers and resin matrices[26,29,30].

    Aside from filler type,filler structure is a crucial factor in determining the mechanical properties of DRCs [17,31,32]. Recent research has demonstrated that nanoparticle clusters (NCs) have a superior reinforcing effect, and NCs have been applied in commercial DRCs (e.g., Filtek Z350 XT, 3 M ESPE, USA). Several methods, including coupling [33], sintering [34], and solvent evaporation[35],have been used to prepare NCs as fillers for DRCs.However,to the best of our knowledge,few of these processes have been applied to construct NCs with more than one component.

    Spray drying is an efficient and robust particle-production method that has been widely used in industrial processes [36],such as in the food [37], pharmaceutical [38], and chemical[39,40] industries. It enables the continuous and fast production of particles within a reasonable size range. In our previous work,SiO2NCs (SNCs) [41], hydroxyapatite (HAp) NCs [42], and SiO2–ZnO complex NCs (CNCs) [43] were precisely constructed using a spray dryer with a two-fluid nozzle. The DRCs filled with these NCs showed significantly enhanced properties compared with those filled with the nanoparticle counterparts.In particular,DRCs filled with the SiO2–ZnO CNCs displayed enhanced antibacterial activity while maintaining good mechanical properties [43]. However,their lack of radiopacity makes such DRCs unsuitable for clinical applications.

    Our objective in the present work is to provide a general strategy to construct multifunctional fillers for DRCs using a spray dryer with a three-fluid nozzle.The use of a three-fluid nozzle avoids the aggregation of incompatible particles before the spray drying process, which may occur with the use of a traditional two-fluid nozzle due to its single feed line and nozzle[44,45]. In general,threefluid nozzle spray drying has been applied in biomedicines, especially for microencapsulation [46–48]. Herein, we report on the use of the three-fluid nozzle spray drying process for the first time in the construction of multifunctional CNCs. ZrO2and ZnO nanoparticles were adopted as the co-fillers of SiO2nanoparticles in order to realize radiopaque and antibacterial properties in the DRCs. The filling properties of the CNCs constructed by two- and three-fluid nozzles were compared. In addition, a heat treatment process was applied to strengthen the structure of the CNCs. The relationships between the SiO2–ZrO2ratios in the heat-treated CNCs and the properties of the DRCs were investigated. The radiopacity and antibacterial activity of the DRCs filled with SiO2–ZrO2–ZnO CNCs were confirmed. The universality of threefluid nozzle spray drying was also explored.

    2. Experimental section

    2.1. Reagents and materials

    Absolute ethyl alcohol (C2H5OH), tetraethyl orthosilicate(TEOS), ammonium hydroxide (NH3·H2O), sodium hydroxide(NaOH), n-propylamine, and cyclohexane were bought from Beijing Chemical Reagent Co.,Ltd.Zirconium oxychloride octahydrate(ZrOCl2·8H2O), triethylene glycol dimethacrylate (TEGDMA),bisphenol A glycerolate dimethacrylate (Bis-GMA), zinc acetylacetonate, oleic acid, phenylcarbinol, camphorquinone (CQ), and ethyl-4-dimethylaminobenzoate (4-EDMAB) were bought from Shanghai Aladdin Biochemical Technology Co., Ltd. 3-Methacryloxypropyl trimethoxysilane (γ-MPS) was purchased from Alfa Aesar (China) Chemical Co., Ltd.

    2.2. Preparation of inorganic nanodispersions

    The SiO2nanodispersion was obtained according to the St?ber method [49]. First, deionized water (70 mL), NH3·H2O (6.4 mL),and ethanol (190 mL) were mixed and stirred at 60°C in a 1000 mL flask. Then, a mixture containing TEOS (30 mL) and ethanol (190 mL) was poured into the above flask. The reaction lasted for 3 h at 60°C.

    The ZrO2nanodispersion was prepared based on a published work [50]. In brief, 10.473 g of ZrOCl2·8H2O was dissolved in 325 mL of deionized water at room temperature. A total of 190 mL of NaOH aqueous solution(0.125 mol·L-1)was added dropwise into the above ZrOCl2solution under vigorous stirring. The mixture was then stirred at 70°C for 3 h,followed by a dialysis process to thoroughly wash the as-obtained zirconium hydroxide precursor.Finally,the precursor was heat-treated at 170°C for 10 h in a 1 L Teflon-lined stainless-steel autoclave to form the ZrO2nanodispersion.

    The preparation of the ZnO nanodispersion was based on our previous work [43]. First, 5.272 g of zinc acetylacetonate, 2.4 mL of oleic acid,and 120 mL of phenylcarbinol were mixed and stirred at 60°C for 3 h. The mixture was then heat-treated at 150°C for 10 h in a 200 mL Teflon-lined stainless-steel autoclave. The obtained suspension was centrifuged and washed with ethyl alcohol for three times, followed by an ultrasonic treatment (Scientz-IID, Ningbo Scientz Biotechnology Co., Ltd., China) to obtain the ZnO nanodispersion.

    2.3.Construction of CNCs using a spray dryer with a three-fluid nozzle

    The SiO2–ZrO2CNCs were constructed using a spray dryer with a three-fluid nozzle. SiO2and ZrO2nanodispersions with a solid content of 2% in mass fraction were simultaneously pumped into the spray dryer through two different liquid channels in the three-fluid nozzle. The aspirator level, inlet temperature, compressed air flow rate, and total feed rate were set at 100%, 100°C,600 L·h-1, and 0.4 L·h-1, respectively. For comparison, SiO2–ZrO2CNCs and SNCs were also constructed by means of a two-fluid nozzle under the same spray drying conditions.

    In order to prepare the SiO2–ZrO2–ZnO CNCs,first,the SiO2and ZnO nanodispersions(2%in mass fraction)were mixed to obtain a SiO2–ZnO dispersion.Then,the above dispersion and the ZrO2nanodispersion(2%in mass fraction) were respectively pumped into the spray dryer through the three-fluid nozzle.The aspirator level,inlet temperature, compressed air flow rate, and total feed rate were set at 100%, 100°C, 600L·h-1, and 0.4 L·h-1, respectively. Other CNCs including SiO2–ZnO–CaF2CNCs, SiO2–TiO2–CaF2CNCs, SiO2–ZnO–ZrO2–TiO2CNCs, and SiO2–ZnO–TiO2–CaF2CNCs were constructed using the same three-fluid nozzle spray drying process as described above;the distributions of the raw materials in the two channels of the three-fluid nozzle are shown in Table S1 in Appendix A.

    To confirm the influence of heat treatment on the filling properties of the SiO2–ZrO2and SiO2–ZrO2–ZnO CNCs,the CNCs were calcined in a muffle furnace (LH 30/13, Nabertherm, China) at 500°C for 3 h. All the inorganic fillers were coded, as shown in Table 1.

    2.4. Preparation of DRCs

    All the fillers were further silanized before being blended with the resin matrices (Bis-GMA and TEGDMA at a mass ratio of 1:1)and photoinitiators (CQ and 4-EDMAB at a mass ratio of 1:4, 1%in mass fraction of the matrices).The silanization process was done according to our previous work[41].All the components were premixed by hand and then thoroughly blended using a three-roll mixer(TR50M,Trilos Precision Equipment Co.,Ltd.,China).The filler content was fixed at 70% in mass fraction. The well-mixed pastes were filled into different silicone rubber molds with various shapes and photopolymerized by means of light-emitting diode(LED)light curing(SLC-VIII B,430–490 nm,Hangzhou Sifang Medical Apparatus Co., Ltd., China) for 120 s. All specimens were polished with silicon carbide papers before testing.

    2.5. Characterization of CNCs

    A transmission electron microscope (TEM; JEOL-7800, JEOL,Japan) was used to observe the nanoparticles at an accelerating voltage of 120 kV.The surface potentials of the nanoparticles were measured using a particle size and zeta potential analyzer (Nano ZS90, Malvern, UK). The morphology and size of the CNCs could be clearly seen via scanning electron microscopy (SEM; JSM-6701F, JEOL) with a 5 kV operating voltage. The crystal structures of the CNCs were confirmed by means of an X-ray diffractometer(D8 Advance, Bruker Optik GmbH, Germany). The distribution of the silicon (Si), zirconium (Zr), zinc (Zn), and oxygen (O) elements in the CNCs were observed using scanning electron microscopyenergy dispersive X-ray spectrometry (SEM-EDS) at 20 kV.

    2.6. Characterization of resin composites

    2.6.1. Mechanical properties

    According to International Organization for Standardization(ISO) 4049:2009, the flexural strength and modulus of the DRCs were determined by means of a three-point bending test using a universal testing machine (CMT6503, MTS Industrial Systems Co.,Ltd., China). Six specimens (25 mm×2 mm×2 mm) were bent in the machine with a span of 20 mm and crosshead speed of 0.75 mm·min-1, respectively. Compressive strength was also tested by the universal testing machine using cylindrical specimens(φ4 mm×6 mm,n=6)with 0.75 mm·min-1crosshead speed.Vickers microhardness was tested on the cylindrical samples(φ6 mm×4 mm, n=6) using a microhardness tester (HXD-1000TMC/LCD, Shanghai Taiming Optical Instrument Co., Ltd.,China) under a 50 g load for 10 s.

    2.6.2. Degree of conversion

    2.6.3. Radiopacity

    Disc-shaped samples(φ10 mm×1 mm)were prepared for each type of DRC and were irradiated with X-rays (70 kV, 8 mA, 0.1 s),along with a standard aluminum (Al) step-wedge having 12 steps ranging from 0.5 to 6 mm, to obtain radiographs. The optical density of each material in the radiographs was measured using an optical density meter (LS117, Shenzhen Linshang Technology Co.Ltd.,China).The radiopacity of the samples was expressed in terms of equivalent Al thickness (mm).

    2.6.4. Antibacterial activity

    The antibacterial activity of the DRCs was determined through a quantitative analysis based on American Society for Testing and Materials (ASTM) E2180–07(2012). Inoculated molten agar slurry(0.08 mL) containing approximately 106colony-forming units(CFU) of Streptococcus mutans (S. mutans) was pipetted onto the DRCs (φ20 mm×2 mm, n=3) and was then incubated at 37°C for 24 h. The surviving S. mutans after incubation was obtained by the elution of the agar slurry inoculum with Dey/Engley(D/E)neutralizing broth.The serial dilutions were spread on tryptic soy agar,and then incubated for 48 h. Finally, the bacterial colonies were counted and recorded. The S. mutans incubated without DRCs was adopted as a blank sample.The antibacterial ratio of the DRCs was calculated by Eq. (2).

    where a represents the antilog of the geometric mean of the number of bacteria recovered from the incubation period in the blank samples, and b represents the antilog of the geometric mean ofthe number of bacteria recovered from the incubation period in the experimental samples.

    Table 1 Codes of different inorganic fillers.

    2.7. Statistical analysis

    The statistical significance was evaluated with SPSS software using one-way analysis of variance(ANOVA)with Tukey’s test with a 95% confidence interval.

    She took her sons shopping. Clerks gasped14 when her sons made grunting15 sounds. And now, she knew about the other women. Sometimes her husband didn t bother to come home. Her friends quit calling her and Marianne felt a biting loneliness.

    3. Results and discussion

    Fig.1 shows a schematic diagram for the preparation process of SiO2–ZrO2CNCs by means of a spray dryer with a two-fluid nozzle and a three-fluid nozzle,respectively. The raw materials(SiO2and ZrO2nanodispersions) for the spray drying process were transparent, and the nanoparticles were well dispersed in the mediums(Figs.1(a)and (b)).A two-fluid nozzle has only one liquid channel and one gas channel (Fig. 1(d)), whereas a three-fluid nozzle includes two liquid channels (Fig. 1(g)). Therefore, the SiO2and ZrO2nanodispersions had to be mixed before being pumped into the spray dryer through the two-fluid nozzle. However, the zeta potentials of the SiO2(–31 mV) and ZrO2(+47 mV) nanoparticles are opposite. This resulted in severe aggregation of nanoparticles,the formation of an opaque nanodispersion,and even precipitation after both nanodispersions were mixed (Fig. 1(c)). As a result, the SiO2–ZrO2CNCs fabricated by the two-fluid nozzle appeared to have an irregular shape (Fig. 1(e)).

    The use of a three-fluid nozzle can avoid unwanted aggregation before the spray drying process by separating nanodispersions with opposite zeta potentials;in this case,the SiO2and ZrO2nanodispersions were simultaneously and respectively pumped into the spray dryer through different channels of the three-fluid nozzle(Fig. 1(f)). The nanodispersions were instantaneously mixed and immediately atomized into microdroplets by compressed air at the end of the nozzle.Meanwhile,the solvent was evaporated from the droplet surface by a gas stream at 100°C. The SiO2–ZrO2CNCs were thus constructed when the solvent was completely evaporated. Fig. 1(h) displays an SEM image of Si60Zr10-3. The regular shape and closely packed structure (similar to those of the SNCs[41]) demonstrate that the incorporation of ZrO2nanoparticles did not affect the morphology of the NCs.

    The mechanical properties of the DRCs filled with SNCs,Si60Zr10-2, and Si60Zr10-3 are shown in Fig. 2. Compared with the performances of the SNCs-filled DRCs, the flexural strength and compressive strength of the Si60Zr10-2-filled DRCs showed a significant decrease(of 16%and 17%, respectively), which was probably due to the irregular and relatively loose structure of Si60Zr10-2. In contrast, the Si60Zr10-3-filled DRCs exhibited good mechanical properties comparable to those of the SNC-filled DRCs, thus demonstrating that the structure of the CNCs is important for their filling properties, and that the three-fluid nozzle is suitable for spray drying components that are incompatible due to opposite zeta potentials.

    CNCs with different SiO2–ZrO2ratios were further constructed by means of the three-fluid nozzle, and were then heat-treated at 500°C for 3 h to improve their filling properties (labeled as HSi64Zr6-3, H-Si62Zr8-3, H-Si60Zr10-3, and H-Si58Zr12-3), since our previous work [51] demonstrated that the heat treatment process can strengthen the CNC structure. The morphologies of the SiO2–ZrO2CNCs are shown in Fig.3,and the corresponding size distributions are displayed in Fig.S1 in Appendix A.All the CNCs exhibited a regular shape and closely packed structure. Their average sizes increased from 1.20 to 1.89μm as the ZrO2content was increased from 6/70 to 12/70.

    Fig. 4 shows the X-ray diffraction (XRD) patterns of CNCs with different SiO2–ZrO2ratios. The broad diffraction peak at 23° indicates that the SiO2nanoparticles are amorphous,which is specified in Powder Diffraction File (PDF) card No. 29–0085. The diffraction peaks at 28.34°, 31.48°, 40.89°, and 45.51° belong to monoclinicphase ZrO2, according to PDF card No. 80–0966, and the peaks at 30°, 35°, 50.37°, and 60.19° can be ascribed to tetragonal-phase ZrO2(PDF card No. 88–1007). These findings indicate that the ZrO2nanocrystals are a mixture of tetragonal and monoclinic phases [50]. In addition, the peaks of ZrO2became stronger with the increase of ZrO2content. To confirm the distributions of SiO2and ZrO2in the CNCs, the O, Si, and Zr elements in H-Si60Zr10-3 were directly observed using SEM-EDS maps (Fig. 5). Fig. 5(a)clearly shows that all the elements are evenly distributed in HSi60Zr10-3, as is also evidenced by the even and spherical distribution of the Si and Zr elements in Fig. 5(b). These results demonstrate that the CNCs are successfully composed of ZrO2and SiO2nanoparticles with even distributions.

    Fig. 1. Schematic diagrams for the preparation process of SiO2–ZrO2 CNCs using a spray dryer equipped with a two-fluid nozzle or a three-fluid nozzle. (a) TEM image and photograph of the SiO2 nanodispersion; (b) TEM image and photograph of the ZrO2 nanodispersion; (c) TEM image and photograph of the SiO2 and ZrO2 mixture;(d)photograph of the two-fluid nozzle;(e)SEM images of Si60Zr10-2;(f)scheme of SiO2 and ZrO2 nanodispersions in the three-fluid nozzle;(g)photograph of the three-fluid nozzle; (h) SEM images of Si60Zr10-3.

    Fig. 2. (a) Flexural strength, (b) flexural modulus, (c) compressive strength, and (d) hardness of DRCs filled with SNCs, Si60Zr10-2, and Si60Zr10-3, respectively. *: p<0.05 compared with the DRCs filled with SNCs.

    Fig. 3. SEM images of (a) H-Si64Zr6-3, (b) H-Si62Zr8-3, (c) H-Si60Zr10-3, and(d) H-Si58Zr12-3.

    Fig. 4. X-ray diffraction (XRD) patterns of H-Si64Zr6-3, H-Si62Zr8-3, H-Si60Zr10-3,and H-Si58Zr12-3.

    Fig. 6 shows the mechanical properties of the DRCs containing heat-treated CNCs (H-Si60Zr10-3) and untreated CNCs (Si60Zr10-3).The heat treatment process clearly and dramatically enhanced the filling properties of the CNCs,especially in terms of the flexural modulus and hardness of the DRCs, which increased by 18% and 40% compared with those of the DRCs filled with untreated CNCs.The main reason for this increase is that the heat treatment process enhanced the interaction among the nanoparticles, resulting in a more compact structure and a densified framework in the CNCs[46], as evidenced by the fracture surfaces of the DRCs (Fig. 7).The Si60Zr10-3-filled DRCs exhibited a flat surface (Fig. 7(a)), indicating weak resistance to an externally applied force. The CNC structure cannot be clearly seen in Fig.7(a);this demonstrates that the nanoparticles in the untreated CNCs are unstable, which may result in destruction after they are extruded from the three-roll extruder.After the heat treatment process,the H-Si60Zr10-3 exhibited a stronger structure,since many complete H-Si60Zr10-3 can be seen on the cross-section of the DRCs (red circles in Fig. 7(b)). The DRCs displayed a coarse fracture surface with several curved steps,demonstrating the crack deflection caused by the addition of H-Si60Zr10-3 and the higher fracture energy of the DRCs [42]. The conversion degrees showed no significant difference between the heat-treated and untreated CNC-filled DRCs(Fig.S2 in Appendix A).

    Fig. 5. SEM-EDS maps for O, Si, and Zr in H-Si60Zr10-3. (a) Holistic element distributions; (b) element distributions in a single CNC.

    Fig.6. (a)Flexural strength,(b)flexural modulus,(c)compressive strength,and(d)hardness of the DRCs filled with Si60Zr10-3 and H-Si60Zr10-3.*:p<0.05 compared with the DRCs filled with Si60Zr10-3.

    Fig. 7. SEM images of the fracture surfaces of DRCs filled with (a) Si60Zr10-3 and(b) H-Si60Zr10-3.

    Fig. 8 gives the radiographs and radiopacity of DRCs filled with different types of fillers; the corresponding data are listed in Appendix A Table S2.Fig.8(a)shows the radiograph of the Al steps and the DRCs filled with SNCs, Si60Zr10-3, and H-Si60Zr10-3. The optical densities of the Al steps in the radiograph show a linear decline (Fig. 8(c)) with the increased thicknesses, indicating the enhanced radiopacity. The SNC-filled DRC displays the lowest radiopacity, which is only equivalent to a 0.14 mm Al step(Table S2), while the DRCs filled with Si60Zr10-3 and H-Si60Zr10-3 are equivalent to the 0.57 and 1.02 mm Al steps, respectively.These results indicate that the addition of ZrO2nanoparticles significantly improves the radiopacity of the DRCs, and that the heat treatment process for the fillers can further strengthen this property.

    DRCs loaded with H-Si64Zr6-3, H-Si62Zr8-3, H-Si60Zr10-3, and H-Si58Zr12-3 were prepared in order to explore the influence of ZrO2content on the radiopacity (Fig. 8(b)). It became evident that an increase of ZrO2content from 6%to 12%in mass fraction led to a significant increment from 0.36 to 1.3 mm of the radiopacity of the DRCs (Table S2). According to ISO 4049:2009, the radiopacity of DRCs must be equal to or higher than that of the same thickness of Al, which means that the H-Si60Zr10-3-filled DRCs and H-Si58Zr12-3-filled DRCs can meet this standard.

    S.mutans is commonly regarded as the primary pathogenic bacteria of dental caries[52,53].Plaque accumulating at the margin of DRCs may result in secondary caries, and may shorten the service life of the DRCs [54,55]. Therefore, ZnO nanoparticles (Fig. S3 in Appendix A) were introduced into the CNCs by means of a threefluid nozzle spray drying process in order to provide the DRCs with antibacterial activity. Fig. 9 shows SEM images of H-Si56Zr10Zn4-3,along with the corresponding XRD pattern and SEM-EDS maps.H-Si56Zr10Zn4-3 maintains a regular shape (Fig. 9(a)), and all the components are successfully imbedded into the CNCs (Fig. 9(b)).The element distributions of O, Si, Zr, and Zn are even (Figs. 9(c)and (d)), which is due to the good dispersion of the raw materials pumped into the spray dryer.

    Fig.8. (a,b) Radiographs and(c, d)radiopacity data of DRCs filled with different types of fillers.1: SNCs; 2:Si60Zr10-3; 3:H-Si60Zr10-3. A:H-Si64Zr6-3; B: H-Si62Zr8-3;C: HSi60Zr10-3; D: H-Si58Zr12-3. The aluminum steps were used as a reference.

    Fig. 9. (a) SEM images and (b) XRD pattern of H-Si56Zr10Zn4-3; (c, d) SEM-EDS maps for O, Si, Zr, and Zn elements in H-Si56Zr10Zn4-3.

    Fig. 10 shows the properties of the H-Si60Zr10-3-filled and HSi56Zr10Zn4-3-filled DRCs. The flexural properties, compressive strength, and degree of conversion of the H-Si56Zr10Zn4-3-filled DRCs show no significant difference in comparison with those of the H-Si60Zr10-3-filled DRCs, which demonstrates that the introduction of the ZnO nanoparticles did not destroy the advantageous structure of the CNCs. However, the hardness decreases from(64.5±0.7) to (61.7±0.2)HV. This decrease is mainly because the ZnO nanoparticles are not as hard as the SiO2and ZrO2nanoparticles.In addition,the radiopacity of the DRCs slightly increases from 1.02 to 1.08 mm (in terms of equivalent Al thickness).

    To quantitatively analyze the antibacterial activity of the HSi56Zr10Zn4-3-filled DRCs, S. mutans was adopted in this study.Fig.11 shows photographs of surviving S.mutans after being incubated for different times in the blank and experimental groups.For the blank group, the number of live S. mutans significantly increased after being incubated for 24 h (Figs. 11(a) and (b)). The number of S. mutans cultured on the H-Si60Zr10-3-filled DRCs for 24 h showed no significant difference in comparison with those cultured on the blank group,indicating that the composites loaded with the SiO2–ZrO2CNCs have no antibacterial activity.In contrast,the growth of the S.mutans incubated on the H-Si56Zr10Zn4-3-filled DRCs was obviously inhibited (Fig. 11(d)), and the antibacterial ratio exceeded 99.9%. These results demonstrate that HSi56Zr10Zn4-3 has great potential as an antibacterial filler.

    To confirm the universality of three-fluid nozzle spray drying,TiO2(Fig. S4(a) in Appendix A) and CaF2(Fig. S4(b) in Appendix A) nanoparticles—which are also commonly used dental fillers—were adopted as co-fillers of SiO2nanoparticles to construct CNCs.The zeta potentials of CaF2and TiO2nanoparticles are +55.6 and+45.2 mV, which are opposite with that of SiO2nanoparticles.Therefore, it is appropriate to use three-fluid nozzle spray drying.Various CNCs were constructed using three or four kinds of nanoparticles as building blocks, including SiO2–ZnO–CaF2CNCs(Fig. 12(a)), SiO2–TiO2–CaF2CNCs (Fig. 12(b)), SiO2–ZnO–ZrO2–TiO2CNCs (Fig. 12(c)), and SiO2–ZnO–TiO2–CaF2CNCs (Fig.12(d)). The mass ratios of the different nanoparticles are shown in Table S1.All the CNCs exhibited a regular shape,thereby demonstrating that three-fluid nozzle spray drying is a feasible and general strategy for constructing multifunctional fillers for DRCs.

    4. Conclusions

    In this study, multifunctional CNCs were successfully constructed using a spray dryer with a three-fluid nozzle for DRCs.The use of the three-fluid nozzle effectively avoided the unwanted aggregation of different nanoparticles with opposite zeta potentials before the spray drying process, thus achieving regularshaped CNCs with evenly distributed elements. For the SiO2–ZrO2binary system, the mechanical properties of the Si60Zr10-3-filled DRCs were consistent with those of SNC-filled DRCs because the regular CNC structure was maintained. The CNCs were also heat treated to reinforce their structure, thus obtaining better filling properties. Compared with the DRCs filled with untreated CNCs,the heat-treated CNC-filled DRCs exhibited significantly improved mechanical properties, particularly in terms of the flexural modulus(an increase of 18%)and hardness(an increase of 40%).In addition, increasing the ZrO2content and using the heat treatment process for the CNCs resulted in DRCs with significantly enhanced radiopacity.The heat-treated CNC-filled DRCs containing over 10%(in mass fraction) ZrO2nanoparticles meet the requirement for radiopaque fillers. For the SiO2–ZrO2–ZnO ternary system, the antibacterial ratio of the H-Si56Zr10Zn4-3-filled DRCs reached 99.9% while the mechanical properties remained stable. This method can also be extended to other ternary and even quaternary systems. Therefore, this work provides a general strategy to construct high-performance multifunctional cluster fillers for DRCs,especially when simultaneously considering the mechanical performance, radiopacity, and antibacterial activity.

    Fig. 10. (a) Flexural strength, (b) flexural modulus, (c) compressive strength, (d) hardness, (e) degree of conversion, and (f) radiopacity of H-Si60Zr10-3-filled and HSi56Zr10Zn4-3-filled DRCs. *: p<0.05 compared with the DRCs filled with H-Si60Zr10-3.

    Fig. 11. Photographs of surviving S. mutans after being incubated for different times.(a)0 h,blank group;(b) 24 h,blank group;(c)24 h,H-Si60Zr10-3-filled DRCs;(d) 24 h, H-Si56Zr10Zn4-3-filled DRCs.

    Fig.12. SEM images of(a)SiO2–ZnO–CaF2 CNCs,(b)SiO2–TiO2–CaF2 CNCs,(c)SiO2–ZnO–ZrO2–TiO2 CNCs, and (d) SiO2–ZnO–TiO2–CaF2 CNCs constructed by means of the three-fluid nozzle spray drying technique.

    Acknowledgments

    This work was financially supported by the National Key Research and Development Program of China (2016YFA0201701)and the National Natural Science Foundation of China(21878015).

    Compliance with ethics guidelines

    Dan-Lei Yang, Dan Wang, Hao Niu, Rui-Li Wang, Mei Liu,Fei-Min Zhang, Jie-Xin Wang, and Mei-Fang Zhu declare that they have no conflict of interest or financial conflicts to disclose.

    Appendix A. Supplementary data

    Supplementary data to this article can be found online at https://doi.org/10.1016/j.eng.2021.08.001.

    日韩精品有码人妻一区| 日韩在线高清观看一区二区三区| 国产伦理片在线播放av一区| 女人久久www免费人成看片| 色94色欧美一区二区| 看免费成人av毛片| 免费女性裸体啪啪无遮挡网站| 国产福利在线免费观看视频| 一区二区三区精品91| 五月伊人婷婷丁香| 亚洲内射少妇av| 丰满迷人的少妇在线观看| 久久久久久久精品精品| 春色校园在线视频观看| 亚洲av免费高清在线观看| 黄色视频在线播放观看不卡| 久久久国产一区二区| av免费在线看不卡| 久久热在线av| 大片免费播放器 马上看| 国产精品久久久久成人av| 春色校园在线视频观看| 亚洲精品456在线播放app| 久久久久久人妻| 欧美精品高潮呻吟av久久| 秋霞伦理黄片| 精品人妻一区二区三区麻豆| 久久久国产欧美日韩av| 欧美激情国产日韩精品一区| 亚洲欧美一区二区三区黑人 | 精品少妇内射三级| 两个人看的免费小视频| 婷婷色综合www| 99久国产av精品国产电影| av卡一久久| 欧美性感艳星| 日韩伦理黄色片| 波野结衣二区三区在线| 午夜视频国产福利| 国产成人精品一,二区| 久久久久久人人人人人| 51国产日韩欧美| av电影中文网址| 久久国产亚洲av麻豆专区| 久久久久精品久久久久真实原创| 2022亚洲国产成人精品| 成人毛片a级毛片在线播放| 纵有疾风起免费观看全集完整版| 国产熟女欧美一区二区| 18在线观看网站| 日韩不卡一区二区三区视频在线| 看非洲黑人一级黄片| 国产一区亚洲一区在线观看| 午夜福利视频精品| 国产黄色视频一区二区在线观看| 97在线人人人人妻| 欧美人与善性xxx| 最近中文字幕2019免费版| 日韩av不卡免费在线播放| 日本午夜av视频| 大码成人一级视频| 狂野欧美激情性xxxx在线观看| 美女福利国产在线| 丰满饥渴人妻一区二区三| 韩国精品一区二区三区 | 一区二区三区四区激情视频| 97在线视频观看| 亚洲欧美成人精品一区二区| 高清欧美精品videossex| 国产成人免费无遮挡视频| 精品卡一卡二卡四卡免费| 中文字幕av电影在线播放| 咕卡用的链子| 少妇熟女欧美另类| 内地一区二区视频在线| 青春草视频在线免费观看| 80岁老熟妇乱子伦牲交| 性高湖久久久久久久久免费观看| 成人毛片60女人毛片免费| 日韩av在线免费看完整版不卡| 日产精品乱码卡一卡2卡三| 免费观看a级毛片全部| 精品一区二区三区四区五区乱码 | 欧美日韩视频精品一区| 一二三四中文在线观看免费高清| 国产在线一区二区三区精| 免费高清在线观看日韩| 亚洲精品色激情综合| 日韩免费高清中文字幕av| 伊人久久国产一区二区| 亚洲欧美一区二区三区黑人 | 五月天丁香电影| 国产精品麻豆人妻色哟哟久久| 美女脱内裤让男人舔精品视频| 成人国语在线视频| 人妻少妇偷人精品九色| 亚洲,欧美精品.| 1024视频免费在线观看| 成人18禁高潮啪啪吃奶动态图| 亚洲精品成人av观看孕妇| 国产av一区二区精品久久| 国产永久视频网站| 日韩成人av中文字幕在线观看| 国产精品一二三区在线看| 欧美激情国产日韩精品一区| 亚洲美女视频黄频| 亚洲av免费高清在线观看| 天天影视国产精品| 边亲边吃奶的免费视频| 人人澡人人妻人| 亚洲成人一二三区av| 亚洲精品美女久久av网站| 免费观看a级毛片全部| 亚洲色图综合在线观看| 久久人人97超碰香蕉20202| 亚洲人成77777在线视频| av片东京热男人的天堂| 一本久久精品| 两个人免费观看高清视频| 日韩人妻精品一区2区三区| 免费av中文字幕在线| 少妇 在线观看| 亚洲人成网站在线观看播放| 国产黄色免费在线视频| 卡戴珊不雅视频在线播放| 内地一区二区视频在线| 永久免费av网站大全| 日韩av免费高清视频| 国产 精品1| 两个人免费观看高清视频| 2022亚洲国产成人精品| 精品少妇内射三级| 久久这里有精品视频免费| 丝袜人妻中文字幕| 免费观看无遮挡的男女| 欧美精品高潮呻吟av久久| 精品福利永久在线观看| 久久青草综合色| 国产在线一区二区三区精| 精品熟女少妇av免费看| 中文字幕最新亚洲高清| 99热全是精品| 黄色 视频免费看| 99热网站在线观看| 国产一区亚洲一区在线观看| √禁漫天堂资源中文www| 国产成人免费无遮挡视频| 欧美日韩av久久| 九色亚洲精品在线播放| 美国免费a级毛片| 欧美丝袜亚洲另类| 亚洲第一av免费看| 一级爰片在线观看| 亚洲国产日韩一区二区| 欧美xxⅹ黑人| 中文字幕人妻熟女乱码| 一级a做视频免费观看| 日韩免费高清中文字幕av| 欧美 日韩 精品 国产| 国产成人午夜福利电影在线观看| 国产av码专区亚洲av| 成人黄色视频免费在线看| 亚洲内射少妇av| 亚洲国产最新在线播放| 亚洲国产成人一精品久久久| 国产不卡av网站在线观看| 日本-黄色视频高清免费观看| 欧美人与性动交α欧美精品济南到 | 看免费av毛片| 丰满少妇做爰视频| 精品少妇内射三级| 蜜桃在线观看..| 99热国产这里只有精品6| 一级毛片我不卡| 精品一品国产午夜福利视频| 91国产中文字幕| 在线观看美女被高潮喷水网站| 九九爱精品视频在线观看| 午夜免费观看性视频| 国产男女超爽视频在线观看| 亚洲熟女精品中文字幕| 视频中文字幕在线观看| 亚洲精品国产av蜜桃| 国产精品久久久久久久电影| 青春草亚洲视频在线观看| 在线亚洲精品国产二区图片欧美| 熟女电影av网| 久久久久视频综合| 在线观看免费日韩欧美大片| 精品人妻偷拍中文字幕| 伊人久久国产一区二区| 新久久久久国产一级毛片| 久久久国产欧美日韩av| 国产在线一区二区三区精| 国产精品.久久久| 成人手机av| 一本色道久久久久久精品综合| 18禁在线无遮挡免费观看视频| 精品99又大又爽又粗少妇毛片| 高清视频免费观看一区二区| 91午夜精品亚洲一区二区三区| 中文精品一卡2卡3卡4更新| 一区二区三区乱码不卡18| 天天躁夜夜躁狠狠躁躁| 在线天堂中文资源库| 婷婷色综合大香蕉| 日韩中文字幕视频在线看片| 国产av国产精品国产| 国产精品久久久久久久久免| 亚洲,欧美,日韩| 日本av免费视频播放| 精品久久国产蜜桃| 中文乱码字字幕精品一区二区三区| videos熟女内射| 久久久国产精品麻豆| 久久精品国产自在天天线| 人人澡人人妻人| 国产无遮挡羞羞视频在线观看| 欧美激情 高清一区二区三区| 欧美亚洲 丝袜 人妻 在线| 色哟哟·www| 久久久久精品性色| 国产免费又黄又爽又色| 亚洲欧美一区二区三区黑人 | 天天躁夜夜躁狠狠久久av| 免费久久久久久久精品成人欧美视频 | 最近中文字幕高清免费大全6| 女的被弄到高潮叫床怎么办| 国产xxxxx性猛交| 国产av精品麻豆| 免费在线观看黄色视频的| 久久99热这里只频精品6学生| 韩国高清视频一区二区三区| 午夜免费男女啪啪视频观看| 纵有疾风起免费观看全集完整版| 日韩制服骚丝袜av| 少妇猛男粗大的猛烈进出视频| 精品99又大又爽又粗少妇毛片| 国产一区二区三区综合在线观看 | av不卡在线播放| 丝瓜视频免费看黄片| 欧美人与善性xxx| 只有这里有精品99| 大片电影免费在线观看免费| 在线 av 中文字幕| 高清在线视频一区二区三区| 免费观看av网站的网址| 亚洲一级一片aⅴ在线观看| 人人澡人人妻人| 成人二区视频| 久久av网站| 亚洲av成人精品一二三区| 久久精品夜色国产| 满18在线观看网站| 咕卡用的链子| 国产白丝娇喘喷水9色精品| 国产视频首页在线观看| 日本欧美视频一区| 桃花免费在线播放| 中文字幕免费在线视频6| 日韩av不卡免费在线播放| 最后的刺客免费高清国语| 亚洲欧美成人精品一区二区| 午夜激情久久久久久久| 久久精品国产亚洲av天美| 亚洲激情五月婷婷啪啪| 美女国产高潮福利片在线看| 国产av精品麻豆| 人人妻人人添人人爽欧美一区卜| 考比视频在线观看| 国产男女内射视频| 久久国产精品男人的天堂亚洲 | av在线app专区| 国产精品一国产av| 少妇熟女欧美另类| 91午夜精品亚洲一区二区三区| 性色avwww在线观看| 不卡视频在线观看欧美| 久久久久人妻精品一区果冻| 80岁老熟妇乱子伦牲交| 日韩中文字幕视频在线看片| 99久久人妻综合| 欧美亚洲 丝袜 人妻 在线| 五月天丁香电影| 久久女婷五月综合色啪小说| 视频中文字幕在线观看| 国产毛片在线视频| 午夜久久久在线观看| 新久久久久国产一级毛片| 美女主播在线视频| 97精品久久久久久久久久精品| 日本免费在线观看一区| 午夜91福利影院| 欧美日本中文国产一区发布| 观看美女的网站| 少妇被粗大的猛进出69影院 | 欧美成人精品欧美一级黄| 一级,二级,三级黄色视频| 一本大道久久a久久精品| 伦理电影大哥的女人| 国产精品女同一区二区软件| 欧美老熟妇乱子伦牲交| 亚洲欧洲精品一区二区精品久久久 | 久久久国产一区二区| 九九爱精品视频在线观看| 中文欧美无线码| 狂野欧美激情性bbbbbb| 男女下面插进去视频免费观看 | 男女边摸边吃奶| 国产精品熟女久久久久浪| 夫妻性生交免费视频一级片| 免费观看无遮挡的男女| 九草在线视频观看| 日本av手机在线免费观看| 赤兔流量卡办理| 久久久国产一区二区| 日本91视频免费播放| 成人国产麻豆网| 在线观看www视频免费| 纵有疾风起免费观看全集完整版| 中文乱码字字幕精品一区二区三区| 欧美日韩综合久久久久久| 高清不卡的av网站| 少妇高潮的动态图| 午夜福利视频精品| 人人妻人人澡人人爽人人夜夜| 亚洲精品久久午夜乱码| 捣出白浆h1v1| 观看美女的网站| 熟女av电影| 国产激情久久老熟女| 午夜免费鲁丝| 免费少妇av软件| av免费在线看不卡| 丝袜喷水一区| 色吧在线观看| 丁香六月天网| 69精品国产乱码久久久| 人妻系列 视频| 久久免费观看电影| 亚洲精品成人av观看孕妇| av网站免费在线观看视频| 亚洲av免费高清在线观看| 人体艺术视频欧美日本| 一级毛片我不卡| 波野结衣二区三区在线| 99九九在线精品视频| 黄色一级大片看看| 日日爽夜夜爽网站| 九草在线视频观看| 国产成人a∨麻豆精品| 免费大片黄手机在线观看| 9色porny在线观看| 亚洲在久久综合| 青春草亚洲视频在线观看| 久久毛片免费看一区二区三区| 日韩av免费高清视频| 免费少妇av软件| 18禁裸乳无遮挡动漫免费视频| 久久精品国产鲁丝片午夜精品| 搡女人真爽免费视频火全软件| 国产精品久久久久久久久免| 看非洲黑人一级黄片| 久热久热在线精品观看| 69精品国产乱码久久久| 久久久久久人妻| 最新中文字幕久久久久| 久久精品国产亚洲av天美| 免费播放大片免费观看视频在线观看| 18禁观看日本| 精品国产一区二区久久| 天天躁夜夜躁狠狠躁躁| 亚洲色图 男人天堂 中文字幕 | 成人毛片60女人毛片免费| 高清欧美精品videossex| 精品少妇黑人巨大在线播放| 桃花免费在线播放| 美女国产高潮福利片在线看| 黄色配什么色好看| 精品第一国产精品| 夜夜爽夜夜爽视频| 少妇的逼好多水| 精品一品国产午夜福利视频| 国产亚洲最大av| 国产又色又爽无遮挡免| 国产精品女同一区二区软件| 成年人免费黄色播放视频| 国精品久久久久久国模美| www.av在线官网国产| 国产成人免费无遮挡视频| 女人久久www免费人成看片| av在线播放精品| 捣出白浆h1v1| 丝袜美足系列| 肉色欧美久久久久久久蜜桃| 亚洲国产精品成人久久小说| 高清黄色对白视频在线免费看| 亚洲av免费高清在线观看| 亚洲一码二码三码区别大吗| 国产 精品1| 午夜日本视频在线| 亚洲成人一二三区av| 一区在线观看完整版| 久久久久久久大尺度免费视频| 久久精品久久久久久噜噜老黄| 中文字幕制服av| 少妇人妻 视频| 丝瓜视频免费看黄片| 亚洲av男天堂| 国产精品麻豆人妻色哟哟久久| 精品午夜福利在线看| 日韩电影二区| 在线观看国产h片| 熟女av电影| 午夜免费鲁丝| 波野结衣二区三区在线| 久久国内精品自在自线图片| 国产成人精品无人区| 亚洲欧美一区二区三区国产| 黄片无遮挡物在线观看| 男人舔女人的私密视频| 一本—道久久a久久精品蜜桃钙片| 亚洲第一av免费看| 91久久精品国产一区二区三区| 亚洲,欧美精品.| 久久精品久久精品一区二区三区| 国产白丝娇喘喷水9色精品| 日韩欧美精品免费久久| 男女免费视频国产| 九色亚洲精品在线播放| 午夜av观看不卡| 如何舔出高潮| 精品久久久久久电影网| 中文字幕免费在线视频6| 国产一区二区三区av在线| 国产精品国产三级国产专区5o| 国产成人精品无人区| 国产成人精品婷婷| 国产乱人偷精品视频| 亚洲精品久久久久久婷婷小说| 午夜福利影视在线免费观看| 亚洲精华国产精华液的使用体验| 少妇的丰满在线观看| 婷婷色av中文字幕| 日韩一本色道免费dvd| 国产亚洲精品久久久com| 乱人伦中国视频| 欧美精品人与动牲交sv欧美| 热re99久久精品国产66热6| 日韩伦理黄色片| av在线app专区| 大片电影免费在线观看免费| 中国美白少妇内射xxxbb| 国产av国产精品国产| 亚洲成人av在线免费| 老司机影院成人| 这个男人来自地球电影免费观看 | 曰老女人黄片| 久久99精品国语久久久| 国产一级毛片在线| 十分钟在线观看高清视频www| 久久狼人影院| 国产成人av激情在线播放| 久久精品人人爽人人爽视色| 久久国内精品自在自线图片| 丝袜人妻中文字幕| 免费黄网站久久成人精品| 久久久久视频综合| 亚洲欧美成人精品一区二区| 卡戴珊不雅视频在线播放| av.在线天堂| 少妇人妻精品综合一区二区| 欧美bdsm另类| 国产免费一区二区三区四区乱码| 国产欧美亚洲国产| 国内精品宾馆在线| 国产精品偷伦视频观看了| 自线自在国产av| 成人国产av品久久久| 亚洲欧美中文字幕日韩二区| 只有这里有精品99| 亚洲伊人色综图| 国产精品人妻久久久影院| 国产不卡av网站在线观看| 国产av国产精品国产| 你懂的网址亚洲精品在线观看| 一二三四在线观看免费中文在 | 99热全是精品| 亚洲av成人精品一二三区| 国产免费又黄又爽又色| av天堂久久9| 国产精品.久久久| 一本久久精品| 丝袜人妻中文字幕| 久久精品国产亚洲av天美| 久久久国产一区二区| 人妻一区二区av| 精品国产国语对白av| 最近最新中文字幕大全免费视频 | 最新中文字幕久久久久| 成人综合一区亚洲| 亚洲情色 制服丝袜| 女性生殖器流出的白浆| 亚洲国产色片| 91aial.com中文字幕在线观看| 亚洲国产精品国产精品| 日本猛色少妇xxxxx猛交久久| 99re6热这里在线精品视频| 日韩欧美精品免费久久| 18在线观看网站| av国产精品久久久久影院| 夫妻性生交免费视频一级片| 欧美xxxx性猛交bbbb| 日本午夜av视频| 亚洲欧美色中文字幕在线| 精品第一国产精品| 全区人妻精品视频| 韩国高清视频一区二区三区| av福利片在线| 久久久久久人妻| 日韩制服骚丝袜av| 久久人人爽人人片av| 三上悠亚av全集在线观看| 视频在线观看一区二区三区| 亚洲人与动物交配视频| 日韩av不卡免费在线播放| 狂野欧美激情性bbbbbb| 汤姆久久久久久久影院中文字幕| 97精品久久久久久久久久精品| 国产精品国产三级专区第一集| 久热久热在线精品观看| 免费播放大片免费观看视频在线观看| 黑人巨大精品欧美一区二区蜜桃 | 中文乱码字字幕精品一区二区三区| 国产成人精品久久久久久| 国产精品嫩草影院av在线观看| 亚洲av日韩在线播放| 国产精品久久久久久精品电影小说| 日韩人妻精品一区2区三区| 水蜜桃什么品种好| 日本与韩国留学比较| 女的被弄到高潮叫床怎么办| 亚洲美女视频黄频| 成年av动漫网址| 国产极品粉嫩免费观看在线| 日日啪夜夜爽| 日韩大片免费观看网站| 国产免费又黄又爽又色| xxx大片免费视频| 久久狼人影院| 一级片'在线观看视频| 国产又爽黄色视频| 久久久国产一区二区| 免费少妇av软件| 九色成人免费人妻av| 赤兔流量卡办理| 青青草视频在线视频观看| 欧美激情极品国产一区二区三区 | 精品酒店卫生间| 精品卡一卡二卡四卡免费| 99国产综合亚洲精品| 色婷婷久久久亚洲欧美| 一级,二级,三级黄色视频| 黄网站色视频无遮挡免费观看| 亚洲天堂av无毛| 韩国精品一区二区三区 | 丝袜喷水一区| 有码 亚洲区| 中国美白少妇内射xxxbb| 亚洲,一卡二卡三卡| 99国产综合亚洲精品| 在线 av 中文字幕| 2022亚洲国产成人精品| 欧美丝袜亚洲另类| 搡女人真爽免费视频火全软件| 欧美变态另类bdsm刘玥| 国语对白做爰xxxⅹ性视频网站| 国产精品国产三级专区第一集| 久久久a久久爽久久v久久| 两个人看的免费小视频| 免费女性裸体啪啪无遮挡网站| 飞空精品影院首页| 多毛熟女@视频| 美女脱内裤让男人舔精品视频| 免费看av在线观看网站| 亚洲内射少妇av| 欧美最新免费一区二区三区| 激情视频va一区二区三区| 欧美精品国产亚洲| 女人久久www免费人成看片| 九色亚洲精品在线播放| 一级毛片 在线播放| 亚洲性久久影院| 中文乱码字字幕精品一区二区三区| 日韩伦理黄色片| kizo精华| 老司机影院成人| 国产精品秋霞免费鲁丝片| 色5月婷婷丁香| 亚洲国产色片| 久久久久久伊人网av| 久久精品国产亚洲av涩爱| 熟女人妻精品中文字幕| 国产精品秋霞免费鲁丝片| 免费在线观看完整版高清| 中文乱码字字幕精品一区二区三区| 国产麻豆69| 欧美人与善性xxx| 午夜激情av网站| av免费在线看不卡| 九草在线视频观看| 欧美成人午夜精品| 久久久久精品久久久久真实原创| 久久久久久人妻| 亚洲情色 制服丝袜|