羧甲基壳聚糖-溶菌酶纳米凝胶稳定无定形磷酸钙促进脱矿牙釉质再矿化

目的:制备羧甲基壳聚糖(CMC)-溶菌酶(LYZ)凝胶,稳定无定形磷酸钙(ACP)进而促进脱矿牙釉质再矿化。方法:首先制备CMC/LYZ-ACP纳米凝胶,利用透射电镜(TEM)观察凝胶的形貌,X射线能谱元素成像分析技术(EDX-Mapping)进行关键元素的定量及分布的分析。然后将纳米凝胶涂抹于酸蚀的牙釉质表面,利用扫描电镜(SEM)、纳米压痕实验(nano-idention)对脱矿牙釉质再矿化效果进行评估,并与人工唾液组进行对照。结果:CMC/LYZ-ACP纳米凝胶为粒径约50~300 nm的致密的球形颗粒。扫描电镜下可见脱矿后的釉质表面有新的晶体形成,与对照组相比,实验组的硬度及弹性模量更接近正常牙釉质。结论:CMC/LYZ-ACP纳米凝胶可以用于脱矿牙釉质的再矿化,属于新型的仿生再矿化材料。     

仿生矿化纳米磷酸钙对牙本质小管封闭性能的评价

目的 制备仿生矿化的纳米磷酸钙,并探讨其对牙本质小管的封闭性能。方法 采用DMEM仿生矿化策略制备无定形磷酸钙材料(DMEM based amorphous calcium phosphate,DACP),运用透射电子显微镜(TEM)、傅里叶变换红外光谱扫描(FTIR)等检测观察其理化表征。选择口腔上皮角质形成细胞(HOK)和牙髓细胞(DPC)分别与材料共培养24 h后,CCK-8法评估材料的生物相容性。收集完整无龋的牙齿制备牙本质片,用DACP材料悬液均匀涂抹牙本质片,设置阳性对照NovaMin组和空白对照组,分别处理1、7 d后扫描电子显微镜(SEM)评估牙本质片的表面和截面封闭效果。结果 TEM显示DACP为均匀球形无定形纳米颗粒,随矿化时间的延长粒径有所增加。CCK-8结果显示HOK和DPC在25、50、100、200 μg/mL DACP下细胞活力均较好,提示材料有较好的生物相容性。牙本质片被处理1 d后DACP组牙本质小管大部分封闭;被处理7 d后DACP组牙本质小管表面呈现完全封闭的状态,且牙本质片截面可见DACP可渗入小管内。结论 运用DMEM仿生矿化策略制备的纳米磷酸钙具有较好的生物相容性和牙本质小管封闭作用,有望成为一种新的脱敏材料。     

聚酰胺－胺诱导牙本质表面矿物沉积的体外实验

目的:探讨3.0代聚酰胺-胺(3.0PAMAM)在牙本质表面诱导生成的矿化物封堵牙本质小管的效果。方法:选取16颗健康正畸牙,制备16个脱矿牙本质样本,按随机数字表法随机选择7个样本作为对照组,7个作为实验组,余2个样本不做任何处理作为脱矿牙本质组。对照组用去离子水处理,实验组用3.0 PAMAM处理之后将各组样本同时浸入人工唾液2、4周后,通过SEM观察每组牙本质小管的微观形貌,X射线能谱仪(EDS)检测牙本质表面沉积物的钙、磷元素含量,并采用两独立样本t检验分析比较4周后2组样本的Ca/P值。结果:SEM观察显示实验组牙本质样本矿化程度随矿化时间延长,表面矿化物逐渐形成,处理4周后完全覆盖所有的牙本质小管口。对照组样本表面矿化物较少,牙本质小管口仍然开放。EDS结果显示沉积物Ca/P值实验组(1.49±0.16)高于对照组(1.18±0.20)(P<0.05)。结论:3.0代聚酰胺-胺对敏感牙本质有一定的生物矿化及封闭作用,在治疗牙本质敏感方面存在潜在价值。     

牙本质玷污层特性对自粘接树脂水门汀粘接强度的影响

目的 评价牙本质表面玷污层的特性对自粘接型树脂水门汀粘接强度和耐久性的影响。方法 将48颗新鲜无龋的人第三恒磨牙暴露出牙本质表面,分别用标准粒径（105~125 μm）金刚砂车针（A组）和标准粒径+细粒径（25 μm）金刚砂车针进行研磨（B组）。研磨后的牙齿分别与Clearfil SA Cement（CSA）和Multilink Speed（MS）两种自粘接型复合树脂水门汀粘接,制成微拉伸试件,试件分别在水中存储24 h和2年,进行微拉伸强度测试,断裂后的试件使用体视显微镜观察粘接界面并记录断裂模式。采用扫描电子显微镜（SEM）观察研磨后的牙本质表面及牙本质-树脂粘接界面。结果 A组SEM观察到研磨后牙本质表面粗糙,玷污层较厚,牙本质小管口未完全栓塞;B组牙本质表面粗糙程度降低,牙本质小管口完全栓塞,玷污层变薄。CSA和MS的B组初期粘接强度显著低于A组（P<0.05）;CSA和MS的粘接强度在水储存2年后出现显著降低（P<0.05）,CSA的B组粘接强度显著低于A组（P<0.05）,而MS的A组与B组间的粘接强度无明显差异（P>0.05）。结论 牙本质表面玷污层特点及自粘接型树脂水门汀类型都会对粘接强度及耐久性产生影响。     

氯化钠溶液对牙本质再矿化作用的影响

目的:探讨氯化钠溶液对脱矿牙本质再矿化晶体结构和Ca、P含量的影响。方法:制备20个脱矿人牙牙本质片,分成实验组和对照组,实验组用0.5 mol/L氯化钠溶液浸泡,对照组用去离子水浸泡,然后再矿化,通过X-衍射仪和X-荧光光谱仪观测比较再矿化后两组晶体结构和Ca、P含量的变化。结果:氯化钠溶液浸泡与去离子水浸泡的脱矿牙本质片相比较,再矿化后生成的晶体晶胞参数a轴缩短(P<0.01),c轴无明显变化(P>0.05),晶体结晶度增加。磨片上生成Ca、P含量显著增多(P<0.01)。结论:0.5 mol/L氯化钠溶液可以提高脱矿牙本质再矿化的效果,生成的晶体晶格更稳定。     

10-MDP-钙盐形成对牙本质粘接成绩影响的评价

目的　分析10-MDP-钙盐形成对牙本质粘接成绩的影响。方法　采用酸蚀冲洗粘接模式，根据牙本质表面的处理方式和选择粘接剂的不同将牙齿随机分为以下4组（n=5）进行处理，制作牙本质/树脂粘接试件：①对照组，直接使用全酸蚀粘接剂Single bond 2(SB2)处理后粘接；②10-MDP组，使用SB2处理进行粘接前，牙本质表面以含有磷酸酯单体10-MDP的自配底涂剂预处理；③CHX组，使用SB2处理进行粘接前，先以氯己定（CHX）预处理牙本质表面;④SBU组，使用包含10-MDP的通用型粘接剂Single bond universal(SBU)处理后进行粘接。通过微拉伸测试（μTBS）测试粘接强度，以X射线衍射(XRD)、原位酶谱测试表征自配10-MDP底涂剂和两种牙本质粘接剂处理的牙本质表面，分析10-MDP-钙盐形成对牙本质粘接成绩的影响。结果　微拉伸结果显示，不同处理方式的粘接试件在24 h水储后没有表现出明显的统计学差异(P>0.1)；经过6个月的水储后，与10-MDP组和SBU组相比，对照组的微拉伸强度显著降低(P<0.05)，而CHX组的微拉伸强度没有明显变化(P>0.05)。XRD结果显示,在10-MDP组和SBU组均检测到10-MDP-钙盐形成的特征性峰，表明有10-MDP-钙盐的形成。原位酶谱结果显示，10-MDP组与SBU组之间混合层荧光强度没有明显区别，但均明显高于对照组，CHX组荧光强度低于10-MDP组与SBU组。结论　10-MDP-钙盐的形成能够保护暴露的胶原纤维不接触到MMPs而免于水解，从而增强牙本质/树脂的粘接成绩。     

不同能量密度Nd:YAG激光照射对牙本质粘接强度的影响

目的:研究不同能量密度下Nd:YAG激光照射对牙本质粘接强度的影响。方法:36颗无龋第三磨牙去除冠方牙釉质,随机分为3组:对照组低能量密度激光照射组(1 W,85 J/cm²)和高能量密度激光照射组(4 W, 350 J/cm²)。每组牙再随机分为两个亚组,分别使用全酸蚀(Single Bond 2)或自酸蚀粘接剂(G-Bond)进行粘接以及树脂修复。进行微拉伸粘接强度测试,扫描电镜观察牙本质表面形貌及粘接界面纳米渗漏情况。激光扫描共聚焦荧光显微镜下观察粘接界面树脂突形态及数量。结果:全酸蚀粘接中,低密度激光照射对粘接强度无影响,高密度激光照射后粘接强度相比对照组降低(P<0.05);自酸蚀粘接中,低密度激光照射后粘接强度比对照组显著下降(P<0.05),高密度激光照射对粘接强度无影响。低密度激光照射不增加粘接界面纳米渗漏,高密度激光照射后样本纳米渗漏相比对照组均显著增加(P<0.05)。结论:低能量密度的激光照射后使用全酸蚀粘接系统粘接效果较好;高能量密度的激光照射后使用自酸蚀粘接系统效果较好。     

牙本质磷蛋白对牙本质再矿化的影响

目的　探讨牙本质磷蛋白 (dentinphosphoprotein ,DPP)与脱矿牙本质再矿化的关系。方法　 (1 )用氯化钠提取脱矿牙本质中的易溶性DPP并鉴定。 (2 )用氯化钠去除和未去除易溶性DPP的脱矿人牙根牙本质磨片 ,经再矿化后通过原子吸收光谱、扫描电镜和显微放射照相的观测比较两组再矿化程度。结果　 (1 )证明了 1mol/L氯化钠可以提取脱矿牙本质中的易溶性DPP ;(2 )去除和未去除易溶性DPP的磨片组相比再矿化液的钙离子浓度显著减少 (P <0 0 1 ) ;磨片上生成较多量的矿物质沉积 ;显微射线照片平均吸光度值显著降低 (P <0 0 1 )。结论　易溶性DPP对脱矿牙本质再矿化有明显的抑制作用 ,在根面龋的再矿化中去除易溶性DPP能提高其再矿化的潜能。     

龋影响牙本质折射系数变化的体外研究

目的:利用光学相干断层成像技术(OCT)分析龋影响牙本质折射系数变化。方法:选取4颗无龋坏和15颗颌面牙本质龋下颌第三磨牙。垂直牙冠长轴制备厚度为300~500 μm的10个无龋和15个龋影响牙本质切片,分别纳入对照和研究组。使用micro-CT和自建OCT扫描切片并重建其三维数字模型。应用基于改良canny边界提取技术的光程通路法分析无龋和龋影响牙本质切片折射系数;通过对比牙本质切片和参考体(K₂HPO₄液)的X线灰度值,计算龋影响牙本质矿化密度。结果:由参考中心点到釉牙本质界,无龋牙本质折射系数先增大而后减小,均值为1.578;龋影响牙本质折射系数无明显变化,均值为1.507,两者间存在显著差异(P<0.001)。龋影响牙本质折射系数和矿化密度间存在显著正相关趋势(P<0.001)。结论:龋引起牙本质折射系数发生改变。矿化密度是导致牙本质折射系数下降的重要因素。     

聚酰胺-胺型树枝状分子对牙本质小管的封闭作用

目的 研究聚酰胺-胺型树枝状分子(polyamidoamine dendrimer,PAMAM)封闭牙本质小管的效果,为牙本质敏感的治疗提供实验依据.方法 选取7颗健康第三磨牙制备28个牙本质薄片,按随机数字表分为A、B、C、D、E、F、G7组,G组为空白对照组不作处理,A～E组经脱矿后置于含PAMAM的0.25％戊二醛水溶液中4℃24h,然后A～E组分别在再矿化液中矿化0、6、12、18和24h,F组脱矿后直接于再矿化液中矿化24h.用场发射扫描电子显微镜(field emission scanning electron microscope,FE-SEM)、X射线衍射(X-ray diffraction,XRD)和能量色散X射线分光计(energy dispersive X-ray spectrometer,EDXS)观察检测.结果 FE-SEM可见各组牙本质样本矿化程度不同,随矿化时间延长,样本表面矿化物逐渐形成,直至完全覆盖样本表面,矿化物可封闭牙本质小管达一定深度.矿化物经EDS和XRD检测证实为羟基磷灰石晶体.结论 PAMAM具有良好的牙本质小管封闭作用,在牙本质敏感的治疗方面有一定的潜在应用价值.     

Biomimetic remineralization of artificial caries dentin lesion using Ca/P-PILP

ObjectiveTo assess the ultrastructural change of demineralized dentin collagen during calcium phosphate polymer-induced liquid precursor (Ca/P-PILP) mediated remineralization process and to evaluate the biomimetic remineralization potential of high concentration Ca/P-PILP at demineralized artificial caries dentin lesion, additionally to investigate the bond interfacial integrity as well as the bonding strength of the biomimetic remineralized artificial caries dentin lesion.MethodsDemineralized dentin collagen of 5 μm thick was biomimetically remineralized with low, medium concentration Ca/P-PILP for 10 days and high concentration Ca/P-PILP for 10, 15, 20 days. Artificial caries dentin lesion at a thickness of 150 ± 50 μm was biomimetically remineralized with high concentration Ca/P-PILP for 20 days. The biomimetic remineralization of demineralized dentin collagen was observed by scanning electron microscopy (SEM). The biomimetic remineralization intensity and depth of artificial caries dentin lesion was assessed by Electron Probe Micro Analyzer (EPMA). The bonding interfacial integrity between remineralized artificial caries dentin and composite resin was observed by Swept-source optical coherence tomography (SS-OCT) and the bonding strength of remineralized artificial caries dentin was evaluated by micro-tensile bond strength analysis (μTBS).ResultsSolely PAA-PASP solution and solely saturated Ca/P solution can’t achieve dentin collagen remineralization. Increased concentration of Ca/P-PILP and prolonged remineralization time can enhance the biomimetic remineralization intensity of demineralized dentin collagen. After treating with high concentration Ca/P-PILP, a 150 ± 50 μm thick layer of demineralized artificial caries dentin lesion was not fully remineralized, and the biomimetic remineralization intensity reached up to 88.0%. Furthermore, a better bonding interfacial integrity with less microgap and increased bond strength at both baseline level and aging level were observed when artificial caries dentin lesion was biomimetically remineralized with high concentration Ca/P-PILP.SignificanceBiomimetic remineralization of demineralized caries dentin lesion promotes its clinical properties for resin composited adhesive restoration.     

单瓶型通用粘接剂在牙本质粘接中的应用评价

［摘要］ 目的 评价2种单瓶型通用粘接剂在自酸蚀模式下应用与牙本质的粘接强度以及纳米渗漏情况。方法 制作40枚牙本质样本,分别使用Singlebond Universal和All-Bond Universal 2种单瓶型通用粘接剂在自酸蚀模式下处理牙本质表面,与复合树脂粘接制作粘接试件。各组粘接试件一半于24 h水储后（未老化）切割成细条,测试微拉伸粘接强度,另一半经受10 000次冷热循环后（老化）测试微拉伸粘接强度。数据以单因素方差分析和Tukey多重比较进行检验分析。各组代表性试件处理后以扫描电镜观察粘接界面,检测纳米渗漏情况。结果 不论是否经过老化,2种粘接剂组均获得了较高的粘接强度值,但扫描电镜均能发现纳米渗漏存在。结论 两种单瓶型通用粘接剂在自酸蚀模式下应用均能提供较好的粘接性能,但无法避免纳米渗漏的发生。     

氯已定预处理对两步法自酸蚀粘接剂牙本质粘接界面稳定性的影响

目的：探讨氯已定预处理对两步法自酸蚀粘接剂的牙本质粘接界面稳定性的影响.方法：40颗离体人磨牙沿垂直于牙长轴的方向切割,暴露冠中部牙本质作为粘接面,牙本质试件随机分为两组,一组在粘接处理前涂布0.2％氯已定为实验组,一组无预处理为对照组,两组经两步法自酸蚀粘接剂SE Bond处理后,堆积复合树脂制备成粘接试件.每组随机抽取2个试件借助微拉曼光谱仪分析粘接剂的双键转化率,剩余的18个试件随机分为两个亚组,分别于即刻和冷热循环5000次后检测微拉伸粘接强度和界面的纳米渗漏情况.结果：0.2％氯已定预处理对SE Bond的树脂双键转化率无显著性影响（P＞0.05）.即刻测试时,对照组和实验组间的微拉伸粘接强度和纳米渗漏差异无统计学意义（PP ＞0.05）.冷热循环老化处理后,实验组的微拉伸粘接强度显著高于对照组,纳米渗漏程度显著低于对照组（P＜0.05）.结论：0.2％氯已定预处理不会干扰SE Bond的树脂聚合,且可提高其与牙本质粘接界面的稳定性.     

Novel bioactive adhesive containing dimethylaminohexadecyl methacrylate and calcium phosphate nanoparticles to inhibit metalloproteinases and nanoleakage with three months of aging in artificial saliva

ObjectivesThe objectives of this study were to: (1) develop a multifunctional adhesive via dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP); and (2) investigate its ability to provide metalloproteinases (MMPs) deactivation and remineralization for long-term dentin bonding durability.MethodsDMAHDM and NACP were incorporated into Adper? Single Bond 2 Adhesive (SB2) at mass fractions of 5% and 20%, respectively. Degree of conversion and contact angle were measured. Endogenous MMP activity of the demineralized dentin beams, Masson’s trichrome staining, nano-indentation, microtensile bond strength and interfacial nanoleakage analyses were investigated after 24 h and 3 months of storage aging in artificial saliva.ResultsAdding DMAHDM and NACP did not compromise the degree of conversion and contact angle of SB2 (p > 0.05). DMAHDM and NACP incorporation reduced the endogenous MMP activity by 53 %, facilitated remineralization, and increased the Young’s modulus of hybrid layer by 49 % after 3 months of aging in artificial saliva, compared to control. For SB2 Control, the dentin bond strength decreased by 38 %, with greater nanoleakage expression, after 3 months of aging (p < 0.05). However, DMAHDM+NACP group showed no loss in bond strength, with much less nanoleakage, after 3 months of aging (p > 0.05).SignificanceDMAHDM+NACP adhesive greatly reduced MMP-degradation activity in demineralized dentin, induced remineralization at adhesive-dentin interface, and maintained the dentin bond strength after aging, without adversely affecting polymerization and dentin wettability. This new adhesive has great potential to help eliminate secondary caries, prevent hybrid layer degradation, and increase the resin-dentin bond longevity.     

Effects of ozone and sodium hypochlorite on caries-like lesions in dentin

The hypothesis that ozone promotes remineralization of dentinal lesions was tested in vitro. Artificial caries-like lesions in dentin were treated with ozone gas, with another potent oxidizer (sodium hypochlorite, NaOCl, 10%) or with water. The specimens were then remineralized and subsequently demineralized again. Mineral content was assessed by transverse microradiography. NaOCl-treated samples showed damaged surface and, after being remineralized, demineralized significantly more than water- or ozone-treated groups. No difference was found between ozone and water groups. The exposure to ozone had thus no effect on remineralization and subsequent demineralization of remineralized dentinal lesions.     

Acid-susceptibility of lesions in bovine enamel after remineralization at different pH values and in the presence of different fluoride concentrations.

Artificial caries lesions were created in sound bovine enamel slices demineralized at pH 5.0. The lesions were then remineralized at either pH 5.5 or pH 6.8 in solutions containing either 1.5, 15, or 50 mumol/L fluoride. The remineralized slices were then demineralized at pH 5.0 for investigation of acid-susceptibility by means of quantitative microradiography. The results indicated that fluoride, incorporated during the preceding remineralization, had a retarding effect on the demineralization after remineralization, and that for the lowest concentration of fluoride in the remineralizing solution, the inhibitory influence of fluoride depended on the pH of the remineralization solutions used.     

Chlorhexidine-loaded poly (amido amine) dendrimer and a dental adhesive containing amorphous calcium phosphate nanofillers for enhancing bonding durability

ObjectiveA novel method of combining chlorhexidine (CHX) loaded poly (amido amine) (PAMAM) dendrimers with a dental adhesive containing amorphous calcium phosphate (ACP) nanofillers are proposed for etch-and-rinse bonding system to enhance resin-dentin bonding durability.MethodsThe CHX-loaded PAMAM and ACP nanofillers were synthesized and characterized. Their effects on the cytotoxicity were tested by MTT assay. Micro-tensile bond strength (μTBS) before and after thermomechanical challenges were used to evaluate the bonding durability. Anti-matrix metalloproteinase (MMPs) property was examined using in-situ zymography. A double-fluorescence technique was used to examine interfacial permeability after bonding. Dentin remineralization in Ca/P lacking solution was observed under scanning electron microscopy.ResultsCompared with a 0.2 wt% CHX solution, the PAMAM loaded CHX had less cytotoxicity, while the in situ zymography showed it could still inhibit MMPs activity within the hybrid layer after released from PAMAM. The application of the novel method maintained the μTBS better than the control group after thermomechanical challenges, and it did not negatively affect water permeability of the bonding interfaces. CHX-loaded PAMAM regulated the calcium (Ca) and phosphate (P) ions provided by the ACP-containing adhesives to remineralize the demineralized dentin surfaces without initial Ca/P in the environment.SignificanceThe novel method can reduce the cytotoxicity of CHX, inhibit MMPs activities, maintain μTBS, and induce dentin remineralization, which are crucial factors for enhancing bonding durability.     

Effect of smear layer characteristics on dentin bonding durability of HEMA-free and HEMA-containing one-step self-etch adhesives

The purpose of this study was to evaluate the effect of smear layer characteristics on the dentin bonding durability of HEMA-free and HEMA-containing one-step self-etch adhesives. Xeno V (XV; HEMA-free), G BOND PLUS (GB; HEMA-free) and Clearfil S(3 )Bond (S(3); HEMA-containing), were applied to dentin surfaces prepared with either #180- or #600-grit SiC paper according to manufacturers' instructions. Bond strengths to dentin were determined using μTBS test after 24-hour, 6-month, and 1-year water storage. In addition, nanoleakage evaluation was performed using an SEM. The smear layer characteristics affected water-tree nanoleakage formation in the adhesive layers of XV and GB, which contributed to a reduction in μTBS after 6-month water storage, while the characteristics did not affect the μTBS of S(3). However, regardless of the smear layer characteristics, 1-year water storage significantly reduced the μTBS of all the adhesives and was associated with an increase in failures at the adhesive-composite interface.     

Impact of silanization of different bioactive glasses in simplified adhesives on degree of conversion,dentin bonding and collagen remineralization

ObjectiveTo analyze simplified adhesive containing pure or silanized bioglass 45S5 (with calcium) or Sr-45S5 (strontium-substituted) fillers applied on dentin and to evaluate the microtensile bond strength (µTBS), interface nanoleakage, degree of conversion of adhesive, collagen degradation and remineralization.MethodsAmbar Universal adhesive (FGM) was doped with 10 wt% bioactive glasses to form following groups: Control (no bioglass), 45S5 (conventional bioglass 45S5), Sr-45S5 (Sr-substituted bioglass 45S5), Sil-45S5 (silanized bioglass 45S5) and Sil-Sr-45S5 (silanized bioglass Sr-45S5). Adhesives were applied after dentin acid-etching using phosphoric acid at extracted human molars. Resin-dentin sticks were obtained and tested for µTBS, nanoleakage at 24 h or 6 months. Degree of conversion was measured using micro-Raman spectroscopy. Dentin remineralization was assessed by FTIR after 6-month storage in PBS. Hydroxyproline (HYP) release was surveyed by UV-Vis spectroscopy. Statistical analysis was performed using ANOVA and Tukey’s test (p < 0.05).ResultsRegarding µTBS, Sr-45S5 and 45S5 presented higher and stable results (p > 0.05). Control (p = 0.018) and Sil-Sr-45S5 (p < 0.001) showed µTBS reduction after 6-month aging. Sil-Sr-45S5 showed higher HYP release than that obtained in the 45S5 group. Sil-45S5 showed mineral deposition and increase in µTBS (p = 0.028) after 6-months. All experimental adhesives exhibited higher degree of conversion compared to Control group, except for 45S5. All adhesives created gap-free interfaces, with very low silver impregnation, except for Sil-Sr-45S5.SignificanceThe incorporation of silanized 45S5 bioglass into the universal adhesive was advantageous in terms of dentin remineralization, bonding performance and adhesive polymerization. Conversely, Sil-Sr-45S5 compromised the µTBS, interface nanoleakage and had a negative impact on HYP outcomes.     

Formulation of nano-graphene doped with nano silver modified dentin bonding agents with enhanced interfacial stability and antibiofilm properties

ObjectiveThe aim of this study was to synthesize and characterize reduced nano graphene oxide (RGO) and graphene nanoplatelets (GNPs) doped with silver nanoparticles (nAg) and to prepare an experimental dentin adhesive modified with RGO/nAg and GNP/nAg nanofillers for studying various biological and mechanical properties after bonding to tooth dentin.MethodsNanoparticles were characterized for their morphology and chemical structure using electron microscopy and infrared spectroscopy. Experimental dentin adhesive was modified using two weight percentage (0.25% and 0.5%) of RGO/nAg and GNP/nAg to study its degree of conversion (DC), antimicrobial potential, and cytotoxicity. The effect and significance of these modified bonding agents on resin-dentin bonded interface were investigated by evaluating interfacial nanoleakage, micropermeability, nanodynamic mechanical analysis, micro-tensile bond strength (µTBS), and four-point bending strength (BS),ResultsBoth 0.25% and 0.5% GNP/nAg graphene-modified adhesives showed comparable DC values to the commercial and experimental adhesive (range: 42–46%). The bacterial viability of the groups 0.25% and 0.5% GNP-Ag remained very low under 25% compared to RGO/nAg groups with low cytotoxicity profiles (cell viability>85%). Resin-bonded dentin interface created with GNP/nAg showed homogenous, well-defined hybrid layer and regularly formed long resin tags devoid of any microporosity as evidenced by SEM and confocal microscopy. The lowest nanoleakage and highest bending strength and µTBS was recorded for 0.25% GNP/nAg after 12 months of ageing. A significantly increased nanoelasticity was seen for all experimental groups except for control groups.SignificanceThe addition of 0.25% GNP/nAg showed optimized anti-biofilm properties without affecting the standard adhesion characteristics.