Impact of Gluma Desensitizer on the tensile strength of zirconia crowns bonded to dentin: an in vitro study

This study tested the impact of Gluma Desensitizer on the tensile strength of zirconia crowns bonded to dentin. Human teeth were prepared and randomly divided into six groups (N = 144, n = 24 per group). For each tooth, a zirconia crown was manufactured. The zirconia crowns were cemented with: (1) Panavia21 (PAN), (2) Panavia21 combined with Gluma Desensitizer (PAN-G), (3) RelyX Unicem (RXU), (4) RelyX Unicem combined with Gluma Desensitizer (RXU-G), (5) G-Cem (GCM) and (6) G-Cem combined with Gluma Desensitizer (GCM-G). The initial tensile strength was measured in half (n = 12) of each group and the other half (n = 12) subjected to a chewing machine (1.2 Mio, 49 N, 5°C/50°C). The cemented crowns were pulled in a Universal Testing Machine (1 mm/min, Zwick Z010) until failure occurred and tensile strength was calculated. Data were analyzed with one-way and two-way ANOVA followed by a post hoc Scheffé test, t test and Kaplan–Meier analysis with a Breslow–Gehan analysis test (α = 0.05). After the chewing simulation, the self-adhesive resin cements combined with Gluma Desensitizer showed significantly higher tensile strength (RXU-G, 12.8 ± 4.3 MPa; GCM-G, 13.4 ± 6.2 MPa) than PAN (7.3 ± 1.7 MPa) and PAN-G (0.9 ± 0.6). Within the groups, PAN, PAN-G and RXU resulted in significantly lower values when compared to the initial tensile strength; the values of all other test groups were stable. In this study, self-adhesive resin cements combined with Gluma Desensitizer reached better long-term stability compared to PAN and PAN-G after chewing simulation.     

Effect of thermal cycling on the bond strength of self-adhesive cements to fiber posts

The aim of this study was to assess the push-out bond strengths of self-adhesive resin cements to epoxy resin-based fiber posts after challenging by thermocycling. Thirty-six single-rooted premolars were endodontically treated, and the post-spaces were drilled to receive RelyX Fiber posts #1. Three self-adhesive resin cements (RelyX Unicem, G-Cem, and Breeze) were used for luting fiber posts. The bonded specimens were either stored for 1 month in a moist field (37°C) or submitted to thermocycling (5,000 times) prior to push-out test. The maximum force required to dislodge the post via an apical-coronal direction was recorded (megapascal). The data were statistically analyzed with two-way ANOVA and Tukey tests (p < 0.05). The factors "luting cement" and "thermocycling" significantly influenced bond strengths. The initial push-out values of RelyX Unicem and Breeze were higher than those of G-Cem. After thermocycling, the bond strength of G-Cem increased and no differences were found between groups. RelyX Unicem and Breeze bond strengths were not affected by the thermal challenge. Thermal cycling and cement type differently influence the bond strengths of self-adhesive resin cements. Self-adhesive cements can represent an option for luting fiber posts into root canal.     

Marginal adaptation of three self-adhesive resin cements vs. a well-tried adhesive luting agent

This in vitro study compared the marginal adaptation of three self-adhesive composite cements with the clinically well-tried dentin adhesive system Panavia F 2.0. A total of 32 Empress 2 all-ceramic MOD-inlays (eight in each group) were luted using the self-adhesive composite cements Maxcem, Multilink Sprint, and RelyX Unicem Clicker; Panavia F 2.0 served as a clinically well-tried control. Each luted inlay underwent long-term water storage of 90 days as well as additional mechanical and thermal loading to simulate oral service. Marginal integrity was evaluated in both dentin and enamel finishing lines using scanning electron microscopy (SEM) and dye penetration tests. Dye penetration was lowest for Panavia followed by RelyX Unicem. Maxcem and Multilink showed a considerable dye penetration of up to 60%. After aging, SEM analysis revealed a reduction of “perfect margin” areas for Multilink Sprint and RelyX Unicem in enamel and for Maxcem and Multilink in dentin. Compared with the well-tried system Panavia—which was assumed as the golden standard of adhesive luting systems—only the self-adhesive luting agent RelyX Unicem showed similar results of marginal adaptation after long-term water storage.     

Nd: YAG激光对3种树脂水门汀与牙本质粘接强度的影响

目的观察Nd: YAG激光照射前后树脂水门汀-牙本质粘接界面的微观形貌特征,评价Nd: YAG激光对3种树脂水门汀与牙本质间粘接强度的影响。方法选择人离体前磨牙30颗,分为颊、舌两部分,将试件随机分为激光组和对照组。激光组以0.8 W、10 Hz脉冲Nd: YAG激光作用于牙本质表面25 s,联合3种树脂水门汀RelyX ARC、Panavia F和RelyX Unicem充填;对照组直接使用树脂水门汀充填。然后测试剪切强度,在根管显微镜下观察断裂模式并分类。另选人离体前磨牙6颗,按照标准的牙本质粘接面预备后,使用Nd: YAG激光照射3颗牙牙本质表面,并联合充填不同的树脂水门汀,用扫描电镜观察Nd: YAG激光照射前后树脂水门汀-牙本质界面的微观形貌变化。结果
激光照射可以提高自酸蚀树脂水门汀Panavia F和自粘接树脂水门汀RelyX Unicem与牙本质之间的剪切强度（P＜0.05）。激光会降低全酸蚀树脂水门汀RelyX ARC与牙本质间的剪切强度（P＜0.05）。根管显微镜下观察可见：试件断裂大部分发生在树脂水门汀-牙本质界面。扫描电镜观察可见：Nd: YAG激光照射后,全酸蚀亚组和自酸蚀亚组的混合层变薄、树脂突变短且少;自粘接亚组变化不明显,未见树脂突。结论Nd: YAG激光照射后,可提高Panavia F和RelyX Unicem与牙本质的剪切强度,建议临床联合应用。     

A study of self-adhesive resin cements for bonding to silver-palladium-copper-gold alloy -- effect of including primer components in cement base

This study investigated the efficacies of adhesive resin cements (Clearfil SA Luting, Maxcem, G-CEM, RelyX Unicem Clicker, Vitremer Paste) for bonding to Ag-Pd-Cu-Au alloy not surface-pretreated with metal primer. For control, Panavia F 2.0 -developed for use with a proprietary metal primer, Alloy Primer- was tested with and without metal primer application. Pairs of alloy disks (10.0 and 8.0 mm in diameters, 3.0 mm thickness) were air-abraded with alumina and bonded with one of the cements. Shear bond strengths (SBSs) were measured before and after 50,000 times of thermocycling. Among Maxcem, RelyX Unicem Clicker and the control, there were no statistical differences in SBS before and after thermocycling. After thermocycling, Clearfil SA Luting exhibited the highest SBS among all the cements. Results showed that Clearfil SA Luting, Maxcem, and RelyX Unicem Clicker were efficacious for bonding to Ag-Pd-Cu-Au alloy after air abrasion surface treatment for the latter.     

3种树脂水门汀对CAD/CAM全瓷-牙本质剪切强度的比较

目的:评价3种树脂水门汀对CAD/CAM全瓷-牙本质剪切强度的影响。方法:选取新鲜拔除的人磨牙30颗,制备牙本质黏结面,随机分为3组(n=10),分别选用全酸蚀树脂水门汀RelyX ARC、自酸蚀树脂水门汀Clearfil DCBond和自黏结树脂水门汀RelyX Unicem对CAD/CAM硅酸锂玻璃全瓷进行黏结,测试3种树脂水门汀对CAD/CAM全瓷-牙本质的剪切强度,并通过立体显微镜观察牙本质的黏结界面。采用SPSS11.0软件包对数据进行统计学分析。结果:RelyX ARC组的剪切强度为(15.90±6.15)MPa,Clearfil DC Bond组的剪切强度为(14.41±5.07)MPa,而RelyXUnicem组的剪切强度为(23.29±7.39)MPa,与前2组相比有显著性差异(P<0.05)。立体显微镜观察显示,3组黏结断面均位于牙本质与树脂水门汀之间。结论:自酸蚀树脂水门汀及自黏结树脂水门汀与CAD/CAM硅酸锂玻璃陶瓷修复体的黏结强度不低于传统全酸蚀树脂水门汀,且临床操作简便,为临床全瓷黏结提供了更多便利与选择。     

Shear bond strength of resin cements to human dentin.

OBJECTIVES: The objectives of this in vitro study were (1) to assess the bond strength of the universal cement RelyX Unicem to dentin and to compare it with three conventional resin cements, (2) to test the influence of aging on their bonding capacity and (3) to test the influence of the operator on bonding quality by performing the same test in two different centers. METHODS: 160 third molars, divided into 80 for tests at the University of Zurich (Z) and 80 for tests at the University of Berne (B), were assigned to 2 x 8 subgroups of 10 teeth each. The specimens were prepared with the corresponding bonding agents and acrylic rods were luted either with RelyX Unicem (U), RelyX ARC (A), Multilink (M) or Panavia 21 (P). All specimens were stored in water for 24h (W) and half of the specimens were subjected to 1500 cycles of thermocycling (5 degrees C and 55 degrees C) (T). Bond strength was measured by means of a shear test. RESULTS: After water storage RelyX Unicem exhibited lowest bond strength (UWZ: 9.2+/-1.6 MPa, UWB: 9.9+/-1.2 MPa, AWZ: 15.3+/-6.0 MPa, AWB: 12.2+/-4.3 MPa, MWZ: 15.6+/-3.3 MPa, MWB: 12.4 MPa+/-2.4, PWZ: 13.4+/-2.9 MPa, PWB: 14.9+/-2.6 MPa). Thermocycling affected the bonding performance of all four cements. However, bond strength of RelyX Unicem was least influenced by thermocycling (UTZ: 9.4+/-2.9 MPa, UTB: 8.6+/-1.3 MPa, ATZ: 11.4+/-6.3 MPa, ATB: 13.3+/-3.7 MPa, MTZ: 15.4+/-3.1 MPa, MTB: 10.3+/-2.4 MPa, PTZ: 11.1+/-2.8 MPa, PTB: 11.3+/-2.8 MPa). SIGNIFICANCE: Although the bond strength of RelyX Unicem to dentin was lower in comparison to RelyX ARC, Multilink and Panavia 21, its bond strength was less sensitive to variations in handling and aging.     

Microleakage of various cementing agents for full cast crowns.

OBJECTIVES: To evaluate microleakage and marginal gaps in full cast crown restorations bonded with six different types of cementing agents. METHODS: Sixty non-carious human premolars and molars were prepared in a standardized manner for full cast crown restorations. The mesial and distal margins were located in dentin, while the vestibular and palatal/lingual margins were located in enamel. Crowns were made from a high-gold alloy using a standardized technique. The specimens were randomized to six groups of cementing agents: one zinc-phosphate cement (Harvard cement), one conventional glass-ionomer cement (Fuji I), one resin-modified glass-ionomer cement (Fuji Plus), two standard resin cements (RelyX ARC, Panavia F), and one self-adhesive universal resin cement (RelyX Unicem). After 4 weeks of storage in distilled water at 37 degrees C, the specimens were subjected to 5000 thermocycles ranging from 5 to 55 degrees C. Then, they were placed in a silver nitrate solution, embedded in resin blocks, and vertically cut in buccolingual and mesiodistal direction. Subsequently, the objects were evaluated for microleakage and marginal gap using a high-resolution digital microscope camera. RESULTS: A number of inter-group differences were statistically significant. RelyX Unicem showed the smallest degree of microleakage both in enamel and in dentin. Panavia F und RelyX Unicem were associated with significantly larger marginal gaps than all other cementing agents. No association was observed between microleakage and marginal gap other than a weak direct correlation when using Harvard cement on enamel. SIGNIFICANCE: The cementing agents investigated revealed different sealing abilities. These differences were not associated with specific types of materials.     

Bond strength and interfacial micromorphology of etch-and-rinse and self-adhesive resin cements to dentin

Purpose: To evaluate the microtensile bond strength and interfacial micromorphology of indirect composite restorations to dentin using three commercial resin cements after 24 hours and 30 days of water storage. Materials and Methods: The medium dentin of third human molars was exposed (N = 30, n = 10 per group). Three commercial resin cements were used to cement indirect resin composite restorations to dentin: the auto‐cured C&B Cement/All Bond 2, the dual‐cured RelyX ARC/Adper Single Bond 2, and the self‐adhesive dual‐cured RelyX Unicem. Teeth were sectioned after water storage at 37°C (24 hours and 30 days) to obtain beams with a bonded area of 0.8 mm². The specimens were tested in a universal testing machine at a 0.5 mm/min crosshead speed. Scanning electron microscopic fractographic and interfacial micromorphology analyses were performed. Data were analyzed using two‐way ANOVA and Tukey′s test (α= 0.05). Results: Mean bond strength (MPa) after 24 hours: C&B Cement 19.5 ± 3.8, RelyX ARC 40.8 ± 9.4, RelyX Unicem 31.3 ± 7.4; after 30 days: C&B Cement 24.5 ± 5.1, RelyX ARC 44.2 ± 8.5, RelyX Unicem 28.3 ± 7.1. The mean bond strengths of both dual‐cure cements were significantly higher than that obtained with C&B Cement after 24 hours. A significant increase in the bond strength of C&B Cement was verified after 30 days, reaching values statistically equivalent to those produced by RelyX Unicem and RelyX ARC. The self‐adhesive cement preserved the same level of bond strength after 30 days. Fractographic analysis revealed a prevalence of cohesive fractures in the hybrid layer for C&B Cement, mixed (cohesive in the cement, hybrid layer, and adhesive) for RelyX ARC, and cohesive in the cement for RelyX Unicem. No distinguishable hybrid layer or resin tags were observed in the interaction of RelyX Unicem with dentin. Conclusions: The particular interaction of each cement with dentin results in specific bond strength and failure patterns that varied among groups in both evaluation times. Even though the self‐adhesive cement tested exhibited no authentic hybrid layer, it was able to promote reliable adhesion with the underlying dentin.     

The effect of surface preparation and luting agent on bond strength to a zirconium-based ceramic

OBJECTIVES: To investigate the bond strength of modern "self-adhesive" resin cements to a zirconium-based dental ceramic following different surface preparations and storage conditions. METHODS: The surface of zirconium-based ceramic discs (12 x 2 mm) were either left untreated, prepared using alumina grit-blasting or tribochemical treatment. Resin composite cylinders were bonded to ceramic specimens using Panavia-F, RelyX Unicem or Maxcem resin cements. The shear bond strength of specimens (n = 10) was tested "dry," following 24-hour water immersion or a thermocycling regime. RESULTS: For each surface preparation, a significant reduction in bond strength following 24-hour water immersion and thermocycling compared to "dry" storage conditions was identified for both Panavia-F and Maxcem. However, Unicem specimens exhibited statistically similar SBS values for tribochemically-treated specimens stored dry following 24-hour water immersion or thermocycling (11.7 +/- 1.3, 14.1 +/- 6.3 and 11.7 +/- 4.9 MPa, respectively) (p > 0.05). No significant differences in bond strength were identified for Panavia-F or Unicem specimens for any surface preparation following the thermocycling regime (p > 0.05). In contrast, for each surface preparation following thermocycling (p < 0.001), Maxcem exhibited a significant decrease in SBS compared with Panavia-F and Unicem specimens. CONCLUSIONS: The pre-treatment of a zirconium-based ceramic surface with grit-blasting and tribochemical treatment improves the bond strength of resin cements. Following "wet" storage conditions, Panavia-F and Unicem demonstrated superior bond strength compared with Maxcem. Differences in ceramic surface preparation and the chemistry of resin cements will affect the nature of the bonding mechanism and durability of the adhesive layer.     

Shear bond strength of composite resin cements to lithium disilicate ceramics

The aim of this study was to evaluate the shear bond strength of different commercial composite resin cement systems to lithium disilicate all-ceramic substrate. Five adhesive resin cement systems Panavia 21 and Panavia F (Kuraray), Variolink 2 (Ivoclar-Vivadent), RelyX Unicem Applicap and RelyX ARC (3M ESPE) were used on all-ceramic (IPS Empress 2; Ivoclar-Vivadent) substrate. Shear bond strength of adhesive resin cement to substrate was tested after thermocycling, or without thermocycling (n = 10). Substrate surfaces of the specimen after loading were SEM microscopically examined. The highest bond strengths in water stored conditions were obtained with RelyX ARC (28.7 +/-3.9 MPa), while in thermocycled conditions the highest bonding values were obtained with Variolink 2 (23.2 +/- 7.5 MPa). The lowest values in both water stored (5.8 +/- 4.0 MPa) and thermocycled (2.4 +/- 2.9 MPa) conditions were obtained with Panavia 21. Shear bond strengths appeared to be affected significantly by thermocycling (anova, P < 0.05). It was concluded that there were significant differences between the bond strengths of adhesive resin cements to lithium disilicate substrate.     

Limited decalcification/diffusion of self-adhesive cements into dentin

Resin cement diffusion into dentin may differ as a function of the pre-treatment regimen. Since self-adhesive cements do not require substrate pre-treatment for luting, penetration of and interaction with the underlying dentin are questioned. We hypothesized that differences in the resin cement diffusion into dentin may exist among current commercial adhesive cements. Composite cylinders were luted on mid-coronal dentinal surfaces by an etch-and-rinse cement (Calibra), a self-etching system (Panavia F 2.0), and 4 self-adhesive cements (Multilink Sprint, Rely X Unicem, G-Cem, Bis-Cem). Dentin/cement interfacial characteristics were analyzed by a staining technique (Masson's trichrome) and by scanning electron microscopy. Conventional acid etching resulted in partially infiltrated adhesive interfaces differing from those achieved with the application of self-etching primer. No hybrid layer and/or resin tag formation was detectable at the interfaces bonded with self-adhesive cements. Limited decalcification/infiltration was observed for self-adhesive cements into the underlying dentin. Self-adhesive cements were not able to demineralize/dissolve the smear layer completely.     

Bond strength of self-adhesive resin cements to different treated indirect composites

Objectives

The objective of this study was to determine microtensile bond strength (μTBS) to dentin of three self-adhesive and a total-etch resin cements used for luting different treated indirect composites.

Materials and methods

Composite overlays (Filtek Z250) were prepared. Their intaglio surfaces were ground with 600-grit SiC papers and randomly assigned to three different surface treatments: no treatment, silane application (RelyX Ceramic Primer), and silane agent followed by a bonding agent (Adper Scotchbond 1 XT). The composite overlays were luted to flat dentin surfaces of extracted human third molars using the following self-adhesive resin cements: RelyX Unicem, Maxcem Elite and G-Cem, and a total-etch resin cement, RelyX ARC. The bonded assemblies were stored in water (24 h, 37 °C) and subsequently prepared for μTBS testing. Beams of approximately 1 mm² were tested in tension at 1 mm/min in a universal tester (Instron 3345). Data were analyzed by two-way ANOVA and Student–Newman–Keuls tests (α?=?0.05).

Results

A significant influence of the resin cement used was detected. Composite surface treatment and the interaction between the resin cement applied and surface treatment did not affect μTBS.

Conclusions

Surface treatment of indirect resin composite did not improve the μTBS results of dentin/composite overlay complex. Self-adhesive resin cements tested obtained lower μTBS than the total-etch resin cement RelyX ARC. Specimens luted with Maxcem Elite exhibited the highest percentage of pretesting failures.

Clinical relevance

Surface treatment of indirect resin composite with silane or silane followed by a bonding agent did not affect bond strength to dentin.     

Evaluation of the adhesion of fiber posts to intraradicular dentin

The interfacial strength and ultrastructure of a total-etch, self-etch and self-adhesive resin cement used to lute endodontic glass fiber posts (FRC Postec, Ivoclar-Vivadent) was assessed with the "thin-slice" push-out test and transmission electron microscopy (TEM). The tested adhesive cements were Variolink II (Ivoclar-Vivadent), Panavia 21 (Kuraray Co) and RelyX Unicem (3M ESPE). In each group, seven posted roots were used for push-out tests and two were processed for TEM observations. The interfacial strength achieved by Variolink II (10.18 +/- 2.89 MPa) was significantly higher than Panavia (5.04 +/- 2.81 MPa) and RelyX Unicem (5.01 +/- 2.63 MPa), which were comparable to each other. TEM micrographs of the interface between Variolink II and intraradicular dentin revealed that the smear layer was totally removed and an 8-10 micron thick hybrid layer was formed. In the other group specimens, the smear layer was not completely dissolved and smear plugs were retained. Gaps were present between the hybridized complex and the adhesive layer in the Panavia 21 specimens and between the smear layer and underlying root dentin in the RelyX Unicem specimens. Interfacial strengths and microscopic findings were in agreement and indicated that the bonding potential of the total-etch resin cement was greater. The acidic-resin monomers responsible for substrate conditioning in Panavia 21 and RelyX Unicem appeared unable to effectively remove the thick smear layer created on root dentin during post space preparation.     

酸蚀对自黏结树脂水门汀与牙本质黏结强度的影响

目的:评价酸蚀预处理对自黏结树脂水门汀Unicem、G-Cem、Clearfil SA Cement、BisCem与牙本质微拉伸黏结强度的影响。方法:选用人无龋离体第三恒磨牙32颗,用低速切片机将选用磨牙冠1/4处沿垂直于牙体长轴方向切开,暴露牙本质。实验组在牙本质表面涂布37%磷酸,冲洗、吹干,对照组不做处理。然后将各组与直径为5 mm、高为4 mm的树脂块分别用 Unicem、G-Cem、Clearfil SA Cement、BisCem进行黏结。水浴24 h后,用低速切片机将样本切割成约1 mm×1 mm×8 mm条状,再进行微拉伸测试,并通过扫描电镜观察黏结界面。采用SPSS16.0软件包对数据进行统计学分析。结果:Unicem组（12.9±3.2） MPa、G-Cem组（11.7±2.6） MPa及Clearfil SA Cement组（10.9±2.3） MPa与牙本质的微拉伸黏结强度显著高于BisCem组（6.8±2.4） MPa（P<0.05）。酸蚀预处理后,Unicem组（9.2±2.5） MPa、G-Cem组（6.1±2.3） MPa及Clearfil SA Cement组（4.8±1.7） MPa黏结强度显著降低（P<0.05）,而BisCem组（7.1±2.9） MPa黏结强度无显著差异。结论:牙本质的表面酸蚀预处理降低了自黏结树脂水门汀G-Cem、Clearfil SA Cement及Unicem 的牙本质黏结强度,但对BisCem的牙本质黏结强度无显著影响。     

Bonding of resin composite luting cements to zirconium oxide by two air-particle abrasion methods

OBJECTIVE: This study evaluated the shear bond strength of two resin composite luting cements to zirconium oxide ceramic substrate using two air-particle abrasion methods. METHODS: Two resin composite cements, RelyX Unicem (3M ESPE) and Panavia F (Kuraray), each with an acidic composition, were used in combination with a zirconium oxide (DCS Dental AG) substrate containing Al2O3 and SiO2 (Rocatec system, 3M ESPE) and two air-particle abrasion methods. The shear bond strength of the resin composite cement to the substrate was tested after the samples were either water-stored for one week or thermocycled following 24 hours of water storage. RESULTS: The RelyX Unicem resin composite cement specimens with the Rocatec treatment (20.9 +/- 4.6 Mpa and 20.1 +/- 4.2 MPa, respectively, n = 12) demonstrated the highest shear bond strength. Alternatively, the lowest values were obtained for the Panavia F resin cement samples, with Al2O3 air-particle abrasion in both storage conditions, water storage for one week (17.7 +/- 8.9MPa) or thermocycling after 24 hours of water storage (16.3 +/- 4.9 MPa). Neither storage condition or particle abrasion system significantly affected shear bond strengths (ANOVA, p > 0.05). CONCLUSION: It was concluded that two different surface conditioning methods and storage conditions did not significantly affect the bonding properties of Panavia F and RelyX Unicem resin composite luting cements to Zirconia.     

In vitro comparative bond strength of contemporary self-adhesive resin cements to zirconium oxide ceramic with and without air-particle abrasion

This study compared shear bond strengths of six self-adhesive resin cements to zirconium oxide ceramic with and without air-particle abrasion. One hundred twenty zirconia samples were air-abraded (group SB; n = 60) or left untreated (group NO). Composite cylinders were bonded to the zirconia samples with either BisCem (BC), Maxcem (MC), G-Cem (GC), RelyX Unicem Clicker (RUC), RelyX Unicem Applicator (RUA), or Clearfil SA Cement (CSA). Shear bond strength was tested after thermocycling, and data were analyzed with analysis of variance and Holm–Sidak pairwise comparisons. Without abrasion, RUA (8.0 MPa), GC (7.9 MPa), and CSA (7.6 MPa) revealed significantly higher bond strengths than the other cements. Air-particle abrasion increased bond strengths for all test cements (p < 0.001). GC (22.4 MPa) and CSA (18.4 MPa) revealed the highest bond strengths in group SB. Bond strengths of self-adhesive resin cements to zirconia were increased by air-particle abrasion. Cements containing adhesive monomers (MDP/4-META) were superior to other compositions.     

Microleakage of IPS empress 2 inlay restorations luted with self-adhesive resin cements

OBJECTIVE : To assess the microleakage of three self-adhesive and one etch-and-rinse resin cements when luting IPS Empress 2 (Ivoclar Vivadent, Liechtenstein) all-ceramic inlay restorations to the prepared cavities in extracted human molars. METHODS : The cylindrical Class V cavities were prepared on the buccal surfaces of 40 extracted human third molars using diamond burs. The IPS Empress 2 ceramic inlays were placed with Multilink Sprint (Ivoclar Vivadent), RelyX Unicem (3M ESPE, USA), G-Cem (GC, Japan), or Variolink II (Ivoclar Vivadent) as the control group. After storage in distilled water at 37°C for 24 hours, samples were subjected to 1000 thermal cycles between baths of 5°C and 55°C, with a dwell time of 30 seconds. The microleakage scores were examined on the occlusal and gingival margins at 30× magnification after each sample was stained with 0.5% basic fuchsin and sectioned into three parts using a thin diamond blade (Isomet, Buehler, USA) (n=40). The extent of microleakage on both occlusal and gingival margins of the restorations was scored and recorded. The microleakage data were analyzed using Kruskall-Wallis and Mann-Whitney U-tests. RESULTS : Statistically significant differences were observed between the groups in both margins according to the Kruskall-Wallis and Mann-Whitney U-tests (p<0.05). Microleakage scores on the occlusal margins were Variolink II < RelyX Unicem < G-Cem = Multilink Sprint. Microleakage scores on the gingival margins are Variolink II = RelyX Unicem < G-Cem < Multilink Sprint. CONCLUSION : Self-adhesive resin cements displayed higher microleakage scores on the occlusal margins, whereas on the gingival margins RelyX Unicem showed comparable microleakage results with the control samples.     

Bond durability of composite luting agents to ceramic when exposed to long-term thermocycling

PURPOSE: This study evaluated the effect of thermocycling on the microtensile bond strength of four adhesive luting agents to GN-I CAD-CAM ceramic. The hypothesis tested was that thermocycling did not affect bonding effectiveness, irrespective of the luting agents used. MATERIALS AND METHODS: Ceramic specimens of two different sizes (6x8x3 mm; 13x8x4 nm) were fabricated from GN-I CAD-CAM ceramic blocks (GC) using a low-speed diamond saw. Two different sized porcelain discs were bonded with one of the four composite luting agents (Linkmax [LM], Panavia [PN], RelyX Unicem [UN] and Variolink II [VL]) according to the manufacturer's instructions. The specimens were stored for 24 hours in distilled water at 37 degrees C and subjected to 0; 10,000; 20,000 and 40,000 thermocycles prior to microTBS testing. Two-way analysis of variance was used to test the influence of luting cement, thermocycling and interaction between both (p < 0.05). The Tukey HSD test determined statistical differences in microTBS for each luting composite between the different thermocycling conditions (p < 0.05). The mode of failure was determined at a magnification of 50x using a stereomicroscope (Wild M5A). RESULTS: Two-way ANOVA revealed that microtensile bond strength was affected by the luting cement, thermocycling and a combination of both. No difference in bond strength between Linkmax, Panavia F and Variolink II was noticed after 24 hours of water storage (LM: 47.6 MPa; PN: 41 MPa; VL: 36 MPa). RelyX Unicem scored significantly lower than Linkmax and Panavia F (UN: 24.2 MPa). The influence of thermocycling on bond strength was different for the four luting cements. Using Variolink II, the bond strength remained stable after 40,000 thermocycles (43.6 MPa). Linkmax showed a significant decrease in bond strength after 10,000 (26 MPa) and 40,000 thermocycles (14.8 MPa). Panavia F and RelyX Unicem were the most negatively influenced, as all specimens failed prior to testing (pre-testing failures) when the specimens were thermocycled 10,000 and 20,000 times or longer, respectively. Regarding the failure mode, there was a correlation between bond strength and type of failure. Initially, a combination of adhesive and mixed adhesive-cohesive failures was noticed. The percentage of adhesive failures increased, together with a decrease in bond strength. CONCLUSION: It was concluded that there were significant differences among the four resin composite cements in terms of their bonding effectiveness to CAD-CAM ceramic after thermocycling. The varying degrees of bonding effectiveness of these adhesive luting agents highlight the need for material specifications.