Effects of Bond Primers on Bending Strength and Bonding of Glass Fibers in Fiber‐Embedded Maxillofacial Silicone Prostheses

Purpose: To evaluate the effect of three commonly used bond primers on the bending strength of glass fibers and their bond strength to maxillofacial silicone elastomer after 360 hours of accelerated daylight aging. Materials and Methods: Eighty specimens were fabricated by embedding resin‐impregnated fiber bundles (1.5‐mm diameter, 20‐mm long) into maxillofacial silicone elastomer M511 (Cosmesil). Twenty fiber bundles served as control and did not receive surface treatment with primers, whereas the remaining 60 fibers were treated with three primers (n = 20): G611 (Principality Medical), A‐304 (Factor II), and A‐330‐Gold (Factor II). Forty specimens were dry stored at room temperature (23 ± 1°C) for 24 hours, and the remaining specimens were aged using an environmental chamber under accelerated exposure to artificial daylight for 360 hours. The aging cycle included continuous exposure to quartz‐filtered visible daylight (irradiance 760 W/m²) under an alternating weathering cycle (wet for 18 minutes, dry for 102 minutes). Pull‐out tests were performed to evaluate bond strength between fiber bundles and silicone using a universal testing machine at 1 mm/min crosshead speed. A 3‐point bending test was performed to evaluate the bending strength of the fiber bundles. One‐way Analysis of Variance (ANOVA), Bonferroni post hoc test, and an independent t‐test were carried out to detect statistical significances (p < 0.05). Results: Mean (SD) values of maximum pull‐out forces (N) before aging for groups: no primer, G611, A‐304, A‐330‐G were: 13.63 (7.45), 20.44 (2.99), 22.06 (6.69), and 57.91 (10.15), respectively. All primers increased bond strength in comparison to control specimens (p < 0.05). Primer A‐330‐G showed the greatest increase among all primers (p < 0.05); however, bonding degraded after aging (p < 0.05), and pull‐out forces were 13.58 (2.61), 6.17 (2.89), 6.95 (2.61), and 11.72 (3.03). Maximum bending strengths of fiber bundles at baseline increased after treatment with primers and light aging in comparison with control specimens (p < 0.05), and were in the range of 917.72 to 1095.25 and 1124.06 to 1596.68 MPa at both baseline and after 360 hours aging (p < 0.05). Conclusions: The use of A‐330‐G primer in conjunction with silicone Cosmesil M511 produced the greatest bond strength for silicone‐glass fiber surfaces at baseline; however, bond strength was significantly degraded after accelerated daylight aging. Treatment with primer and accelerated daylight aging increased bending strength of glass fibers.     

Effects of Accelerated Artificial Daylight Aging on Bending Strength and Bonding of Glass Fibers in Fiber‐Embedded Maxillofacial Silicone Prostheses

Purpose: The purpose of this study was to test the effect of different periods of accelerated artificial daylight aging on bond strength of glass fiber bundles embedded into maxillofacial silicone elastomer and on bending strength of the glass fiber bundles. Methods and Materials: Forty specimens were fabricated by embedding resin‐impregnated fiber bundles (1.5‐mm diameter, 20‐mm long) into maxillofacial silicone elastomer. Specimens were randomly allocated into four groups, and each group was subjected to different periods of accelerated daylight aging as follows (in hours); 0, 200, 400, and 600. The aging cycle included continuous exposure to quartz‐filtered visible daylight (irradiance 760 W/m²) under an alternating weathering cycle (wet for 18 minutes, dry for 102 minutes). Pull‐out tests were performed to evaluate bond strength between fiber bundles and silicone using a universal testing machine at 1 mm/min crosshead speed. Also a three‐point bending test was performed to evaluate bending strength of the fiber bundles. One‐way ANOVA and Bonferroni post hoc tests were carried out to detect statistical significance (p < 0.05). Results: Mean (SD) values of maximum pull‐out forces (in N) for groups 1 to 4 were: 13.63 (7.45), 19.67 (1.37), 13.58 (2.61), and 10.37 (2.52). Group 2 exhibited the highest pull‐out force that was statistically significant when compared to the other groups. Maximum bending strengths of fiber bundles were in the range of 917.72 MPa to 1124.06 MPa. Bending strength significantly increased after 200 and 400 hours of aging only. Conclusions: After 200 hours of exposure to artificial daylight and moisture conditions, bond strength between glass fibers and heat‐cured silicones is optimal, and the bending strength of the glass fiber bundles is enhanced.     

Biomechanical properties of nano-TiO2 addition to a medical silicone elastomer: The effect of artificial ageing

Objectives

The aim of this study was to evaluate the effect of TiO₂ nanoparticles on the mechanical and anti-ageing properties of a medical silicone elastomer and to assess the biocompatibility of this novel combination.

Methods

TiO₂ (P25, Degussa, Germany) nanoparticles were mixed with the silicone elastomer (MDX4-4210, Dow Corning, USA) at 2%, 4%, and 6% (w/w) using silicone fluid as diluent (Q7-9180, Dow Corning, USA). Blank silicone elastomer served as the control material. The physical properties and biocompatibility of the composites were examined. The tensile strength was tested for 0% and 6% (w/w) before and after artificial ageing. SEM analysis was performed.

Results

TiO₂ nanoparticles improved the tensile strength and Shore A hardness of the silicone elastomer (P < 0.05). However, a decrease in the elongation at break and tear strength was found for the 6% (w/w) composite (P < 0.05). All the ageing methods had no effect on the tensile strength of the 6% (w/w) composite (P > 0.05), but thermal ageing significantly decreased the tensile strength of the control group (P < 0.05). Cellular viability assays indicated that the composite exhibited biocompatibility.

Conclusions

We obtained a promising restorative material which yields favourable physical and anti-ageing properties and is biocompatible in our in vitro cellular studies.     

Effect of Extraoral Aging Conditions on Mechanical Properties of Maxillofacial Silicone Elastomer

Purpose: The purpose of this study was to investigate the effect of extraoral human and environmental conditions on the mechanical properties (tensile strength and modulus, elongation, tear strength hardness) of maxillofacial silicone elastomer. Materials and Methods: Specimens were fabricated using TechSil‐S25 silicone elastomer (Technovent Ltd, Leeds, UK). Eight groups were prepared (21 specimens in each group; eight tensile, eight tear, five hardness) and conditioned differently as follows (groups 1 through 8): Dry storage for 24 hours; dry storage in dark for 6 months; storage in simulated sebum solution for 6 months; storage in simulated acidic perspiration for 6 months; accelerated artificial daylight aging under controlled moisture for 360 hours; outdoor weathering for 6 months; storage in antimicrobial silicone‐cleaning solution for 30 hours; and mixed conditioning of sebum storage and light aging for 360 hours. The conditioning period selected simulated a prosthesis being in service for up to 12 months. Tensile and tear test specimens were fabricated and tested according to the International Standards Organization (ISO) standards no. 37 and 34, respectively. Shore A hardness test specimens were fabricated and tested according to the American Standards for Testing and Materials (ASTM) D 2240. Data were analyzed with one‐way ANOVA, Bonferroni, and Dunnett's T3 post hoc tests (p < 0.05). Weibull analysis was also used for tensile strength and tear strength. Results: Statistically significant differences were evident among all properties tested. Mixed conditioning of simulated sebum storage under accelerated artificial daylight aging significantly degraded mechanical properties of the silicone (p < 0.05). Conclusions: Mechanical properties of maxillofacial elastomers are adversely affected by human and environmental factors. Mixed aging of storage in simulated sebum under accelerated daylight aging was the most degrading regime. Clinical significance: Accelerated aging of silicone specimens in simulated sebum under artificial daylight for 12 months of simulated clinical service greatly affected functional properties of silicone elastomer; however, in real practice, the effect is modest, since sebum concentration is lower, and daylight is less concentrated.     

赝复硅橡胶经rHBD3浸泡消毒后机械性能变化的研究

目的研究赝复硅橡胶材料在重组人β防御素-3（rHBD3）溶液中浸泡消毒2个月后,拉伸强度、扯断伸长率、邵氏硬度、撕裂强度和重量的变化。方法将制作好的赝复硅橡胶试件分别浸泡在pH5和pH7.5的rHBD3溶液中2个月后,在万能材料试验机上,按ASTM D412标准测量扯断强度、扯断伸长率;按ASTM D624标准测量撕裂强度;利用邵氏A硬度计,按ASTM2240标准测量邵氏A硬度。硅胶试件浸泡5d、15d、30d和60d后,在电子天平上称重。结果 A-2186硅橡胶浸泡在pH5 rHBD溶液中机械性能的改变大于在pH7.5碱性环境中的改变。在酸性环境中浸泡前后,A-2186的拉伸强度变化为5.8~6.3Mpa;扯断伸长率430%~412%;邵氏硬度36.3~41.1。撕裂强度浸泡前后没有明显的变化;吸水率的变化为0.01%~0.36%。结论赝复硅橡胶浸泡在酸性rHBD3溶液中机械性能改变比浸泡在碱性溶液中大,但并不影响临床的使用。     

Effect of adding silver nanoparticle on physical and mechanical properties of maxillofacial silicone elastomer material-an in-vitro study

PurposeThe purpose of this study was to evaluate the impact of silver nanoparticle incorporation into maxillofacial silicone material on its hardness, tear strength and color stability.MethodsA total of 180 silicone specimens were fabricated according to the specification of American society for material and testing (ASTM) No. D142 and No. D624. The control samples were fabricated without silver nanoparticles and test samples were fabricate with 20 ppm concentration of silver nanoparticles. For outdoor weathering specimens were placed in a metal cage, which was suspended from the roof for a period of one month. Digital shore A hardness tests (Yuzuki, DIN 53505, ASTM D2240) was used to measure hardness, for tear strength the specimen was placed in the jaws of the universal testing machine (Lloyd instruments, LR 50 K) and stretched at a rate of 500 ram/rain, for color stability Spectrophotometer had been employed and the data recorded in the CIE L*a*b* system. The independent sample's “t” test was used to test significant differences.ResultsThe mean difference for hardness between control and test group was 0.54 and t value was 2.08 and (p < 0.05).tear strength 0.66 and “t” value was 0.93 and (p < 0.05) and for color stability it was -0.02 and t value was -0.92 and (p < 0.05).ConclusionThe present study findings suggest that addition of silver nanoparticles at 20 ppm concentration decreased the hardness of Teksil 25(S25) silicone elastomer, and it did not affect tear strength and color stability.     

3种偶联剂对铸造纯钛与硬质复合树脂结合强度的影响

目的 研究3种偶联剂对铸造纯钛试件与硬质复合树脂结合强度的影响。方法 用牙科铸钛的方法制作40个直径8 mm、高3 mm的圆盘状纯钛试件,与树脂粘接面用碳化硅砂纸在流水下打磨、Al2O3喷砂、4%氢氟酸（HF）酸蚀。试件随机分为4组,每组10个。对照组（A组）、硅烷偶联剂组（B组）、Alloy Primer组（C组）、Metal photo primer组（D组）。然后在试件表面均匀涂布硬质复合树脂,检测其与纯钛试件的剪切强度,并进行统计学分析,同时对断裂面进行扫描电镜（SEM）观察。结果 A、B、C、D组剪切强度分别为（9.773±0.67）、（11.463±0.82）、（14.224±0.75）、（13.157±0.73） MPa。A组与B、C、D组的剪切强度相比差异有统计学意义（P<0.01）,B组与C、D组的剪切强度相比差异有统计学意义（P<0.01）,C组与D组的剪切强度相比差异无统计学意义（P>0.05）。结论 KH-570硅烷偶联剂、Alloy Primer 偶联剂、Metal photo primer偶联剂可以显著提高钛与硬质复合树脂的结合强度,KH-570硅烷偶联剂处理组的结合强度低于Alloy Primer偶联剂组和Metal photo primer偶联剂组。     

Physical properties of maxillofacial elastomers under conditions of accelerated aging

The stability of the physical properties of various commercially available maxillofacial prosthetic materials was evaluated with the use of an accelerated aging chamber. The tensile strength, maximum percent elongation, shear strength, tear energy, and Shore A hardness were determined before and after accelerated aging. Results indicate that silicone 44210, a RTV rubber, is a promising elastomer for maxillofacial application.     

Push-out Bond Strength of RealSeal SE and AH Plus after Using Different Irrigation Solutions

Introduction

The aim of this investigation was to evaluate the influence of different endodontic irrigants (sodium hypochlorite [NaOCl], chlorhexidine [CHX], and EDTA) on the push-out bond strength of the obturation materials RealSeal SE (SybronEndo, Orange, CA) and AH Plus (Dentsply International Inc, York, PA).

Methods

Two hundred human root canals were prepared and divided into 2 groups according to the filling material (RealSeal SE vs AH Plus). Each group was subdivided into 5 groups according to the irrigation protocol (0.9% saline [control], 3% NaOCl, 3% NaOCl with saline, 17% EDTA, and 2% CHX). After obturation, roots were sliced into 1-mm discs for push-out assessment. Compressive loading was performed using an universal testing machine at a speed of 0.5 mm/min. Two-way analysis of variance and the Kruskal-Wallis test were performed for pair-wise comparisons to assess the differences between the experimental groups.

Results

AH Plus exhibited a significantly higher bond strength than RealSeal SE (mean = 2.53 and 1.53 MPa, respectively; P < .05), except with saline alone (P > .05). Within the AH Plus groups, no significant differences existed between the irrigants and saline alone (P > .05). The bond strength of RealSeal SE with saline alone or with NaOCl and saline did not differ from that of AH Plus with saline alone (P > .05). However, the push-out bond strength of RealSeal SE decreased by approximately half (P < .05 compared with RealSeal SE with saline alone) after rinsing with NaOCl alone, EDTA, or CHX.

Conclusions

The bond strength of RealSeal SE is highly influenced by the irrigant used.     

Effects of different irrigating solutions and disinfection methods on push-out bond strengths of fiber posts

Objective. The aim of this study was to evaluate the effects of various irrigating solutions and photoactivated disinfection (PAD) on the push-out bond strengths of fiber posts to root dentin. Materials and methods. Thirty-two human teeth were divided into eight groups, as follows: (1) irrigation with physiologic saline (control), (2) NaOCl irrigation, (3) chlorhexidine (CHX) irrigation, (4) ethanol (EtOH) irrigation, (5) NaOCl followed by 17% EDTA irrigation, (6) NaOCl-EDTA supplemented with CHX irrigation, (7) NaOCl-EDTA supplemented with EtOH irrigation and (8) NaOCl-EDTA irrigation supplemented with PAD. After the posts were cemented, the roots were transversally sectioned to obtain four slices (1 mm thick) (n = 16). Push-out tests were conducted by applying a load at 0.5 mm/min, types of fracture failures were recorded and data were analyzed with one-way ANOVA and Tukey post-hoc tests (p = 0.05). Results. Push-out bond strength was significantly affected by the type of irrigating solution and the disinfection protocol (p < 0.05). The bond strength of the EtOH, NaOCl and NaOCl-EDTA-CHX irrigated groups was significantly higher than that of the other groups. The highest bond strength was observed in the EtOH irrigated group and the lowest was the NaOCl-EDTA irrigated group. Conclusions. Irrigation with NaOCl and EDTA combined caused lower bond strength than observed in the control group. However, supplementing this combination with CHX improved the post-dentin bond strengths; supplementing with PAD did not.     

Adhesion of Epiphany self-etch sealer to dentin treated with intracanal irrigating solutions

Introduction

This in vitro study assessed the adhesion of Epiphany self-etch (SE) root canal sealer to dentin treated with different irrigation regimens.

Methods

Flat dentin surfaces were obtained from human third molar teeth; smear layer was created on each sample. Five groups of 10 samples each were conditioned with one of the following regimens: (1) deionized water for 10 minutes; (2) 5% sodium hypochlorite (NaOCl) for 10 minutes; (3) 5% NaOCl for 10 minutes and then 10% sodium ascorbate (Na-Ascr) for 10 minutes; (4) 5% NaOCl for 10 minutes and then 2% chlorhexidine (CHX) for 5 minutes; or (5) 5% NaOCl for 10 minutes and then 10% Na-Ascr for 10 minutes, followed by 2% CHX for 5 minutes. The conditioned dentin surfaces were dried with absorbent paper points. The Epiphany SE sealer was placed on each dentin surface with the use of hollow stainless steel tubes with specific diameter and height. The samples were stored in 100% humidity at 37°C for 7 days and then tested for shear bond strength in a universal testing machine.

Results

Shear bond strength data were analyzed by one-way analysis of variance and Tukey post hoc tests (P < .05). There were statistically significant differences among the groups.

Conclusions

NaOCl decreased the bond strength of Epiphany SE sealer to dentin, whereas the use of Na-Ascr reversed this negative effect of NaOCl. CHX had neither negative nor positive influence on the bond strength.     

Repair of temporary fixed dental prostheses using a flowable resin composite: Effect of material,bonding, and aging

ObjectivesAssessment of the effect of aging and bonding on the reparability of different temporary crown and bridge materials using a flowable resin composite.MethodsThe materials used included two bis-acryl and two polymethylmethacrylate materials. The materials were aged either dry, in distilled water, or in a 75% ethanol/water solution. Each group was divided into three subgroups (n = 6) according to the bonding method: application of a universal adhesive, application of a universal primer followed by a universal adhesive, or no bonding. Materials were repaired with a light-cure flowable resin composite; then, they were subjected to thermocycling and tested by shear bond strength. The data were analysed using three-way ANOVA, one-way ANOVA, and Tukey post hoc tests (α = 0.05).ResultsThe shear bond strength was significantly higher for bis-acryl compared to polymethylmethacrylate materials (p < 0.001). In terms of aging conditions, shear bond strength was in the order of 75% ethanol/water solution < dry < water. The application of bonding agents significantly increased the shear bond strength of polymethylmethacrylate-based materials (p < 0.001). The difference between water and dry storage was insignificant (p = 0.558); however, storage in a 75% ethanol/water solution showed significantly lower values compared to both dry and water storage in most of experimental groups (p < 0.001). Polymethylmethacrylate-based materials mainly demonstrated adhesive failure, while bis-acryl materials predominantly showed cohesive failure.ConclusionThe bond strength of a light-cure flowable resin composite is significantly higher with bis-acryl compared to that with polymethylmethacrylate-based substrates. Aging in water does not have a significant effect; however, the 75% ethanol/water solution tends to negatively affect repairability. The application of different bonding agents positively affects the repair strength, especially for polymethylmethacrylate-based substrates.     

Influence of Chlorhexidine Application Time on the Bond Strength between Fiber Posts and Dentin

Introduction

The aim of this study was to investigate the effects of chlorhexidine (CHX) application time on the bond strength and durability of the adhesion of fiber posts relined with resin composite to the root dentin.

Methods

Eighty bovine incisor roots were divided into 4 groups after root preparation: control group (irrigation with physiological solution) and experimental groups, CHX for 30 seconds, CHX for 60 seconds, and CHX for 120 seconds. Fiber posts relined with resin composite were cemented with RelyX ARC. The Scotchbond Multi-Purpose total-etching adhesive system was used in half of the samples of each group, and the Clearfil SE Bond self-etching adhesive system was used in the other half. The samples were randomly divided into 2 subgroups, 24 hours of storage and 12 months of storage. All roots were sectioned transversely, and push-out tests were performed. Bond strength means were analyzed by analysis of variance and Tukey test (α = 0.05). Failure mode was determined by examining specimen's surfaces under scanning electron microscope, and its distribution was evaluated by using χ² test (α = 0.05).

Results

CHX pretreatment resulted in homogeneous bond strength values at 24 hours and 12 months of storage, irrespective of the CHX application time and adhesive system (P < .05). A significant bond strength decrease was noticed after 12 months of storage when irrigation was performed with physiological solution in the control groups (P > .05). Significant differences were observed for fracture patterns (P < .001).

Conclusions

The use of CHX pretreatment could preserve the bond strength of the fiber post relined with resin composite to root dentin for 12 months, irrespective of the CHX application time and adhesive system used.     

树脂表面粗糙度对丙烯酸树脂与硅橡胶粘接强度的影响

高并不利于提高丙烯酸树脂与硅橡胶间的粘接力,用较小粗糙度的600目砂纸打磨丙烯酸树脂表面可提高丙烯酸树脂与硅橡胶间的粘接强度.     

添加纳米聚膦腈对聚氨酯材料力学强度的影响

目的 研究添加纳米聚膦腈对聚氨酯材料力学强度的影响。方法 将3种实验组材料（纯聚氨酯材料（PU）、含1%纳米聚膦腈的聚氨酯材料（1% PSZ-PU）、含5%纳米聚膦腈的聚氨酯材料（5% PSZ-PU））以及对照组自固化型硅橡胶软衬材料,分别经历0次、1 000次、3 000次冷热循环后测试其拉伸强度和撕裂强度,并进行统计学分析。结果 冷热循环0次、1 000次、3 000次后3种聚氨酯复合材料拉伸强度依次为：PU组32.85 MPa、23.09 MPa和24.36 MPa;1% PSZ-PU组34.98 MPa、25.33 MPa和25.52 MPa;5% PSZ-PU组32.29 MPa、28.22 MPa和26.10 MPa。撕裂强度依次为：PU组40.64 kN/m、37.96 kN/m和40.69 kN/m;1% PSZ-PU组40.87 kN/m、41.01 kN/m和40.63 kN/m;5% PSZ-PU组42.73 kN/m、43.28 kN/m和41.59 kN/m,它们均大于对照组硅橡胶材料的拉伸强度和撕裂强度,其中实验组材料组间比较时,除循环1 000次后,5% PZS-PU和1% PZS-PU的拉伸强度差异具有统计学意义（P<0.05）外,其他循环次数中3组实验组材料组间的拉伸强度和撕裂强度的差异均无统计学意义（P>0.05）。结论 3组聚氨酯复合材料的拉伸强度和撕裂强度均高于对照组硅橡胶类软衬材料,5%以内的聚膦腈纳米球添加剂量未对聚氨酯的拉伸强度和撕裂强度产生明显的增强作用。     

树脂表面机械处理方式对硅橡胶与丙烯酸树脂粘结强度的影响

目的：比较不同树脂表面机械处理方式对硅橡胶与丙烯酸树脂粘结强度的影响。方法：按丙烯酸树脂处理方式不同分为9组,7组为砂纸打磨组,分别采用80目,240目,400目,600目,800目,1000目,1500目砂纸流水下均匀打磨,1组为抛光组,1组为喷砂组。各组处理后涂底涂剂,与硅橡胶粘结,测试其抗剪切强度,观察其破坏方式。测试每组部分试片的粗糙度。结果：抗剪切强度基本上与处理表面的粗糙度呈负相关,喷砂组的抗剪切强度最高,达2．46MPa。结论：树脂表面机械处理方式不同会对硅橡胶与丙烯酸树脂粘结强度产生影响,其中以喷砂方式处理可以获得最高的抗剪切强度。     

Cyclic fatigue vs static loading for shear bond strength test of lithium disilicate and dentin substrates: A comparison of resin cement viscosities

ObjectiveTo explore the effect of resin cement viscosities on the shear bond strength under static and fatigue load of lithium disilicate and dentin substrates.MethodsBonded tri-layer samples (lithium disilicate ceramic cylinder, resin cement, and substrate – ceramic or dentin) was performed considering 2 factors (n = 15): “resin cement viscosity” (high, HV; or low, LV) and “loading mode” (static, s-SBS; or fatigue shear bond strength, f-SBS). The specimens were subjected to s-SBS (1 mm/min, 1 kN load cell) and f-SBS (cyclic fatigue, initial load: 10 N; step-size: 5 N; 10,000 cycles/step; underwater). Failure mode, topography, and finite element analysis (FEA) were performed.ResultsThe resin cement viscosity did not influence the s-SBS and f-SBS of lithium disilicate substrate; however, it affected the bond strength to dentin, with HV presenting the worst fatigue behavior (f-SBS = 6.89 MPa). Cyclic loading in shear testing induced a notorious detrimental effect with a relevant decrease (16–56 %) in bond strength and survival rates, except for dentin substrate and LV. Most failures were adhesive. A distinct pattern comparing the disilicate and dentin was identified and FEA demonstrated that there was a stress concentration on the top of the cement layer.SignificanceCyclic fatigue loading in shear testing has detrimental effects on the adhesive behavior and survival probabilities of bonded lithium disilicate sets, regardless of resin cement viscosity. In contrast, resin cement viscosity affects the bond strength and the survival rates of dentin substrate submitted to cyclic loading mode, in which a low viscosity results in better performance.     

A new technique for incorporation of TiO2 nanotubes on a pre-sintered Y-TZP and its effect on bond strength as compared to conventional air-borne particle abrasion and silicatization TiO2 nanotubes application on pre-sintered Y-TZP

ObjectiveThis study evaluated the microshear bond strength of a resin cement to Y-TZP after different methods of TiO₂ nanotubes (nTiO₂) incorporation on pre-sintered Y-TZP surfaces.MethodsnTiO₂ were synthesized and incorporated on Y-TZP slices as follows (n = 15): 1) nTiO₂ mixed with isopropyl alcohol/manual application (MAl); 2) nTiO₂ mixed with acetone/manual application (MAc); 3) nTiO₂ mixed with isopropyl alcohol/high-pressure vacuum application (HPVAl); 4) nTiO₂ mixed with acetone/high-pressure vacuum application (HPVAc). As controls, surfaces were sandblasted with Al₂O₃ (OX) or Rocatec silicatization (ROC). All ceramics were sintered after nTiO₂ incorporation. Surface treatments of OX and ROC were made after sintering. Surfaces were characterized by confocal laser microscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Resin composite cylinders (1.40 mm diameter and 1 mm height) were cemented with a resin cement, stored in water at 37 °C for 24 h and thermocycled for 10 000 cycles before microshear bond strength evaluation. Data were analyzed with one-way ANOVA and Games-Howell (α = 0.05), and fracture analysis was performed using a stereomicroscope.ResultsEDS confirmed the presence of TiO₂ on treated Y-TZP. The confocal analysis showed higher roughness for HPVAc and OX. There were significant differences between surface treatments (p < 0.001). HPVAl (22.96 ± 10.3), OX (34.16 ± 7.9) and ROC (27.71 ± 9.4) showed higher microshear bond strengths and were statistically similar (p > 0.05). MAC showed intermediary values, and HPVAc and MAl presented decreased bond strength, with a high percentage of premature debonding.ConclusionHigh-pressure vacuum application of nTiO₂ mixed with isopropyl alcohol was able to produce bond strength values compared to conventional air abrasion and Rocatec silicatization.SignificanceThe infiltration of TiO₂ nanostructures on the pre-sintered Y-TZP is an interesting approach that can improve bond strength without the need of sandblasting methods.     

负载氯己定的埃洛石纳米管对牙本质粘结强度的影响

目的: 探讨将负载氯己定的埃洛石纳米管掺入全酸蚀粘接剂ONE-STEP及自酸蚀粘接剂XENO Ⅴ后对牙本质粘结强度的影响。方法: 将120颗离体牙分为10组,根据粘接剂XE、OS以及掺入负载氯己定（chlorhexidine,CHX）的埃洛石纳米管（halloysite nanotube,HNT）质量体积比5%、10%、15%分组, 分别为XE对照组（A1组）、XE实验对照组（A2组）、5%CHX/HNT-XE组（A3组）、10%CHX/HNT-XE组（A4组）、15%CHX/HNT-XE组（A5组）、OS对照组（B1组）、OS实验对照组（B2组）、5%CHX/HNT-OS组（B3组）、10%CHX/HNT-OS组（B4组）和15%CHX/HNT-OS组（B5组）。树脂充填24 h后,测试拉伸剪切强度（tensile shear strength,TSS）值。电镜扫描,观察粘结界面嵌合层的形态。采用SPSS 19.0软件包对同一粘接剂各组以单因素方差分析TSS值,不同粘接剂及不同质量比各组以双因素方差分析TSS值。结果: 自酸蚀XE多组中,5%CHX/HNT组的TSS值最高;全酸蚀OS组中,10%CHX/HNT组的TSS值最高（P<0.05）。不同品牌粘接剂对TSS无显著影响,而CHX/HNT质量体积比对TSS有显著影响。结论: 将适合浓度的CHX/HNT掺入自酸蚀粘接剂XENO Ⅴ和全酸蚀粘接剂ONE-STEP中,可增加牙本质粘结强度。     

Evaluation of a novel primer containing isocyanate group on dentin bonding durability

ObjectivesTo evaluate the benefits of a novel dentin-bonding primer, namely, isocyanate-terminated urethane methacrylate precursor (UMP), which can form covalent bonds with demineralized dentin collagen.MethodsThe synthesized and purified UMP monomer was characterized and tested its effects on the degree of conversion (DC) and wettability of an acetone-based dental adhesive. Then UMP primers of different concentrations were formulated and used to prepare adhesive specimens, which were compared with solvent-treated groups. Primer-treated specimens with and without aging were also compared. To evaluate the bonding interface, microtensile strength tests, nano-indentation tests and nanoleakage- eavaluation were performed using a field-emission scanning electron microscope and nano-indenter. Data were analyzed using SPSS 20.0 software with significance set at α = 0.05 using one-way analysis of variance (ANOVA) and two-way ANOVA to characterize the effects of the primer.ResultsTreatment with the UMP primer promoted the DC and wettability of the adhesive on the demineralized dentin surface (P < 0.05); it also increased the bond strength of the aged dentin bonding interface (P < 0.05). Nanoleakage was reduced; the bonding interface became more stable, and the continuity and strength of the hybrid layer improved (P < 0.05) following UMP treatment. The application of 5 mM UMP as a primer for dentin bonding could lead to a stable bonding interface and long-lasting bonding effects.SignificanceThe use of 5 mM UMP primer developed in this study could improve dentin bonding durability and has excellent clinical application prospects.