Higher Shear Bond Strength Values Research Articles

Effect of Surface Treatments on the Color Change and Shear Bond Strength of Porcelain Laminate Veneer

Effect of Surface Treatments on the Color Change and Shear Bond Strength of Porcelain Laminate Veneer Aim of the study: the purpose of this Invitro study to evaluate the effect of surface treatments on the color change and shear bond strength of lithium disilicate glass ceramic veneers. Materials & Methods: Twenty square samples with dimensions (8x8x2) and another twenty samples with smaller dimensions (4x4x2) were cut from five IPS e-max CAD blocks of shade A3. The discs were divided into two groups: 1) Half of the small and large blocks were subjected to hydrofluoric acid (HF); 2) the other half was subjected to Co2 laser irradiation. The conditioned samples were subdivided according to the bonding agent: A) Silane application for 60 seconds; B) Single bond universal light cured for 10 seconds. Each small sample was cemented on the top of a large sample using Rely-x veneer cement with translucent shade. The color change was measured using spectrophotometer. The shear bond strength was tested using a universal testing machine. Results: HF resulted in higher bond shear bond strength and ΔE than Co2 laser. Single bond universal resulted in higher shear bond strength values than silane. Conclusion: HF followed by either single bond universal or silane could be the best surface treatment for e-max CAD ceramic. However, Co2 laser could be a promising alternative surface treatment.

Shear Bond Strength of Composite Repair Material to Ceramo-metallic and zirconium Restorations Using A New Adhesive System

Introduction: success of ceramic repair system is dependent on integrity of bond between ceramic and resin composite. Aim: evaluate shear bond strength (SBS) of composite repair material to ceramo-metallic and zirconium restorations using new adhesive system after thermocycling. Materials and methods: 28 square specimens of metal , zirconia , veneering porcelain for metal (VMK95) and veneering porcelain for zirconia (VM9) were prepared (1 x 1 x 0.5 cm) and divided into 4 groups: 1)metal (M) group , 2)zirconia (Z) group , 3)veneering porcelain for metal (VPM) group , 4)veneering porcelain for zirconia(VPZ) group). Then M and Z groups were sandblasted while VPM and VPZ groups were subjected to HF acid. Single bond universal adhesive were applied to exposed surface of all groups then repair composite material was built up incrementally over center of exposed surface using cylindrical teflon mold ( 3 x 5 mm), stored for 7 days in distilled water followed by 1000 thermocycles then SBS was tested. Results: Highest SBS value between composite repair material and M group followed by Z group and composite repair material then VPM group and composite repair material then VPZ group and composite repair material. Conclusions: Sandblasting and application of single bond universal adhesive containing MDP can be recommended for repair metal and zirconium surfaces with composite material. HF acid etching and application of single bond universal adhesive containing MDP can be recommended for repair VPM and VPZ with composite repair material. Keywords: single bond universal adhesive, veneering porcelain, zirconia

Evaluation of Effectiveness of Self-Adhesive Composites for Amalgam Repair with or Without Alloy Primer, in Terms of Shear Bond Strength

Purpose: The purpose of the present research was to evaluate the effectiveness of self-adhesive composites in amalgam repair as time-saving alternatives to universal bonding-universal composite materials, with or without the usage of Alloy Primer in terms of shear bond strength. Materials and Methods: Forty-two disc-shaped amalgam samples were prepared by condensing into 6×2 mm holes in acrylic resin blocks, sandblasted with 50 μm Al2O3 and randomly divided into 6 groups according to repair material [Constic (Group C), Fusio Liquid Dentin (Group FLD), Universal bonding+Universal composite (Group Control), Alloy Primer+Constic (Group APC), Alloy Primer+Fusio Liquid Dentin (Group APFLD), Alloy Primer+Universal bonding+Universal composite (Group APControl)]. After shear bond strength test, the fracture modes were determined under a digital microscope. Statistical analysis was performed using one-way analysis of variance and Tukey's post hoc test. Results: The highest shear bond strength values were obtained for Fusio Liquid Dentin, among the three repair materials when Alloy Primer was not applied (p<0.05). Usage of Alloy Primer increased shear bond strength values of the investigated repair materials to amalgam, except Fusio Liquid Dentin. Conclusion: Within the limitations of the present research, it can be concluded that; the investigated self-adhesive composite materials could be time-saving alternatives to the Universal bonding+Universal composite for the purpose of amalgam repair, in terms of shear bond strength. The clinicians could prefer Fusio Liquid Dentin self-adhesive composite material without Alloy Primer application for the purpose of amalgam repair in non-cooperative patients.

Dissimilar sintered calcium phosphate dental inserts as dentine substitutes: Shear bond strength to restorative materials.

The application of sintered calcium phosphate dental inserts in the central part of tooth cavities can reduce amount of embedded dental composite and polymerization shrinkage of final dental fillings. The aim of this study was to analyze comparatively physico-chemical and mechanical properties of dental inserts and shear bond strength (SBS) between three dissimilar hydroxyapatite-based dental inserts and different restorative materials, after application of different clinical protocols. Starting from two different hydroxyapatite nano powders and nanostructured stabilized zirconia (YSZ), monophasic two-step sintered dense HAp inserts (TSSHAp), biphasic single-step sintered controlled porous inserts (HAp/TCp), and single-step sintered reinforced HAp/YSZ inserts were processed and characterized. Obvious differences in the microstructure of inserts surface were visualized after etching with 37% phosphoric acid. Fracture toughness of sintered inserts was ranged between 1.01 and 1.85 MPam1/2 (maximum value in the case of HAp/YSZ), while hardness values were in the range of 3.71-5.22 GPa (maximum value in the case of TSSHAp). Acid etching before application improved SBS between inserts and Maxcem compared to direct cement application. TSSHAp and HAP/TCp inserts showed comparable and relatively high SBS values, certainly higher compared to HAp/YSZ inserts. Slightly higher SBS values were measured in the case of TSSHAp insert group, and the highest mean SBS value of 18.51 MPa was determined between TSSHAp inserts and Filtek Z250_SBU following the "self-etch" protocol.

Effect of mechanical alteration of enamel surface on shear bond strength of different bonding techniques

Aim:This study was conducted to evaluate the effect of mechanical alteration of enamel surface on shear bond strength in different bonding techniques.Materials and Methods:Seventy samples were fabricated and randomly divided into three groups: Group A (n = 30) – prepared enamel surfaces, Group B (n = 30) – unprepared enamel surfaces, and Group C (n = 10) – prepared enamel surfaces + etch and rinse which served as a control group. Group A and Group B were further divided into three subgroups (n = 10), sub-Group A1, B1 (nanohybrid composite + self-etch), sub-Group A2, B2 (self-adhering composite), and A3, B3 (self-adhering composite + self-etch). Teflon ring molds were used to make composite resin cylinders with the specific bonding protocol of each group. Shear bond strength testing was conducted, and data were analyzed.Results:Mean shear bond strength values were as follows: C> A1> A3>A2>B1> B3> B2.Conclusions:Prepared enamel surfaces resulted in higher shear bond strength values as compared to unprepared enamel surfaces. Prior application of self-etch agent resulted in higher shear bond strength values of self-adhering composite in prepared and unprepared enamel surfaces.

Bond strength of locator housing attached to denture base resin secured with different retaining materials

The type of housing retaining material may affect the bond strength of the housing to denture base resin. The aim of this in vitro study was to evaluate the bond strength of locator housing attached to polymethyl methacrylate (PMMA) denture base resin secured with different retaining materials. In this in vitro study Forty-four PMMA blocks (10 mm × 15 mm × 15 mm) were prepared with a central cylindrical canal inside to allow the insertion of locator housings. The prepared specimens were then randomly divided into four groups (n = 11). Each group received one of the following retaining materials for housing insertion: Auto-polymerized acrylic resin (APAR), auto-polymerized composite resin (Quick up), application of alloy primer on titanium housing plus Quick up (AL-Quick), and heat-polymerized acrylic resin (HPAR). The specimens were thermocycled 5000 times between 5°C and 55°C, followed by 1000 cycles of vertical insertion separation on the locator abutment. A push-out force was applied on the flat back surface of the housing after which the failure and shear bond strength values were calculated. The data were analyzed using one way-ANOVA and Games-Howell test (α = 0.05). HPAR group had significantly higher shear bond strength values compared to the other groups (P < 0.05). No significant differences were found among the other remaining material groups (P > 0.05). Inserting of locator housing using HPAR resulted in higher bond strength between housing and denture base resin. The application of alloy primer did not improve the bond strength of locator housing which was retained with "Quick up".

Comparative evaluation of shear bond strength of Biodentine, Endocem mineral trioxide aggregate, and TheraCal LC to resin composite using a universal adhesive: An in vitro study

Introduction: The efficacy of the bond between the restorative materials and the pulp capping materials has an important role in the success of vital pulp therapy. Aims and Objective: This study was conducted to investigate and compare the shear bond strength (SBS) of Biodentine, Endocem mineral trioxide aggregate (MTA), and TheraCal LC to resin composite using a universal adhesive at their respective initial setting time and to identify the specific modes of failure using a stereomicroscope at × 25 magnification. Materials and Methods: A total of 60 acrylic blocks were prepared. Each of the blocks were prepared 20 mm high and 12 mm diameter and had a central hole of 2 mm depth and 5 mm diameter. These acrylic blocks were divided into three groups of 20 samples each based on the liner that is condensed into prepared central hole as Group A – Biodentine, Group B – Endocem MTA, and Group C – TheraCal LC. Composite was then bonded to each sample using universal adhesive. SBS analysis was performed at a cross-head speed of 1 mm/min. Observation and Results: Mean SBS of Group B (Endocem MTA) with composite was found to be significantly lower than that of Group A (Biodentine) with composite which was further significantly lower than that of Group C (TheraCal LC) with composite. Conclusion: This present study concludes that the bond strength of resin-based light-curable TheraCal LC showed clinically acceptable and highest SBS values when used with a universal silane containing adhesive.

Shear Bond Strength of Polymeric to Dentin

The purpose of this study was to evaluate the dentin bond strength of restorations made of different polymeric materials with Single Bond Universal Adhensive and etch-and-bond resin cement. Ceromer (ceramage, Shofu), Polymethylmethacrylate (PMMA DISK, Yamahachi), resin nanoceramic (Lava Ultimate, 3M ESPE), and polymer-infiltrated-ceramic-network (Vita Enamic, Vita Zahnfabrik) specimens (n=15/group) were fabricated respectively. Dentin specimens were prepared from extracted third molars stored in distilled water in a refrigerator (4°C). Single Bond Universal Adhensive was applied to the prepared tooth and light cured. Then, specimens were cemented using 3M ESPE RelyXTM Uitimate ClikerTM adhesive resin cement. All cemented specimens were stored in distilled water for 24 h and subjected to shear forces by a universal testing machine. Vita Enamic was found to show the highest shear bond strength values. The shear bond strength of Lava Ultimate was weaker than that of Vita Enamic. But there was no statistical difference between Vita Enamic and Lava Ultimate. Both of them showed significantly higher shear bond strength than the Ceramage and PMMA groups. The lowest values were obtained for PMMA and there was a significant difference between the PMMA and Ceramage groups. The bond strength of the polymeric materials is material dependent. So doctors can use them for patients with different intent.

Bond strength of lithium disilicate after cleaning methods of the remaining hydrofluoric acid.

BackgroundDifferent ceramic surface cleaning methods have been suggested after the acid conditioning. The aim was to evaluate the effect of different protocols used to remove the remaining hydrofluoric acid on the shear bond strength (SBS) between lithium disilicate and resin cement. Material and Methods Forty-four specimens of lithium disilicate (IPS e.max Press) were divided in 4 groups (n=11): group C (control, no treatment); group HF+S (5% hydrofluoric acid + silane); group HF+US+S (5% hydrofluoric acid + ultrasound cleaning + silane); group HF+PH+S (5% hydrofluoric acid + 37% phosphoric acid + silane). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were performed to characterize the surface morphology. The SBS test was performed on the resin/ceramic interface, and the failure mode was characterized. SBS values were submitted to 1-way ANOVA and the Tukey test (α=.05). The relation between surface treatment and failure modes was analyzed using the chi-squared test (α=.05). Results The surface treatment type interfered in the shear strength (p<.001) and higher SBS values were observed for the groups HF+US+S (17.87 MPa) and HF+PH+S (16.37 MPa). The surface treatment did not influence the failure mode (p=.713). No fluorsilicate salts were observed after ultrasound cleaning. Conclusions The utilization of ultrasound cleaning was an effective procedure to remove remaining fluorsilicate salts, promoting the highest SBS values. Key words:Bond strength, ceramics, fluorsilicate, lithium disilicate, resin cement.

Adhesion of PEEK to resin-matrix composites used in dentistry: a short review on surface modification and bond strength

The aim of this work was to perform a scoping review on the PEEK surface modification to establish an effective adhesion to resin-matrix composite for restorative dentistry. A Medline search was performed for related scientific articles published from 1995 up to 2018. PEEK has revealed a low surface energy and a poor wettability that negatively affect the bonding to resin-matrix composites. The increase in roughness by surface modification is the main factor for enhancing mechanical interlocking of PEEK to resin-matrix materials. The highest shear bond strength values of PEEK to resin composites were recorded for gritblasted PEEK modified by sulfuric acid treatment followed by using methacrylate-based adhesives. The combination of ordinary and recent methods for PEEK surface modification has improved PEEK surface for adhesion to resin-matrix materials. Nevertheless, further comparative studies with different adhesive materials and surface treatment are still required.

Effect of repeated laser surface treatments on shear bond strength between zirconia and veneering ceramic

Statement of problemDelamination failure may occur between ceramic frameworks and veneering ceramics, shortening the lifetime of fixed dental prostheses in load-bearing areas. PurposeThe purpose of this in vitro study was to compare the effect of different repeating CO2 laser treatment methods and conventional approaches on the shear bond strength of zirconia frameworks and veneering ceramics. Material and methodsZirconia disks (N=110) were prepared and divided into 5 groups: milling without surface treatment (group M), airborne-particle abrasion (group APA), single laser treatment (group LX1), 2 laser treatments (group LX2), and 3 laser treatments (group LX3). The specimens in the first 2 groups were treated before the framework was coated using the spraying technique. Specimens in the remaining groups were coated with veneering ceramic using the spraying process, and then subjected to laser treatment. Surface roughness and topography, interface properties, phase transformation, shear bond strength, and fracture modes were investigated. Outcomes were analyzed using a profilometer, a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD), a stereomicroscope, and a universal testing machine for mechanical testing. ResultsThe XRD showed that phase transformation from tetragonal to monoclinic occurred after airborne-particle abrasion. This phenomenon was not observed in laser-treated specimens. Groups LX2 and LX3 had the highest surface roughness values, 1.18 ±0.23 μm and 1.21 ±0.22 μm, among all groups, and group LX3 had the highest shear bond strength values for unaged and aged conditions, 32.08 ±2.45 MPa and 31.43 ±2.07 MPa. The mixed-fracture mode was the most common type of fracture observed. ConclusionsThe results indicated that the shear bond strength between the zirconia framework and veneering ceramic was higher after laser surface treatments than after milling alone or after airborne-particle abrasion. Laser treatment methods, particularly LX2 and LX3, could be considered reliable approaches for zirconia surface treatment.

In Vitro Effect of Temperature on Dentin Bond Strength of Universal Adhesive Systems

The aim of this study was to evaluate the shear bond strength (SBS) of two universal adhesives (Universal Single Bond and All Bond Universal) and a two-step self-etch adhesive system (Clearfil SE Bond) to dentine at various temperatures. Materials and Methods: One hundred and twenty dentin specimens were divided randomly to 12 groups, according to adhesive systems (Universal Single Bond and All Bond Universal, Clearfil SE Bond) and temperature ( 4ºC, 20 ºC, 36ºC, 55ºC) used. Dentin specimens were prepared (n :10, adhesives were applied, and composite cylinders were polymerized. Statistical analysis of the SBS data was performed using Two-way analysis of variance (ANOVA) and Tukey’s Honestly Significant Differences post-hoc test. Results: The Clearfil SE Bond was shown to have higher SBS than the universal adhesives at all temperatures; however, there was no statistically significant difference (P&gt;0.05). In both groups, the lowest SBS values were observed in the samples at 4°C while the highest SBS values were observed in the samples at 55°C. In this case, there was a statistically significant difference (P&lt;0.05). Conclusions: The results suggest that the effectiveness of an adhesive may increase if it is preheated at 36°C or above before use instead of being used immediately after removal from the refrigerator or at room temperature.

Influence of photobio-modulation with an Er,Cr: YSGG laser on dentin adhesion bonded with bioactive and resin-modified glass ionomer cement.

One hundred and twenty extracted human molars were allocated in eight groups (n = 15) based on surface conditioning and cement type. Specimens of groups 2 and 6 were conditioned with ECL whereas, groups 3 and 7 were treated with ECL + ethylenediamine tetra acetic acid (EDTA). Specimens in groups 4 and 8 were surface conditioned by ECL + EDTA + Tetric-N-Bond, and groups 1 and 5 were considered as control (non-surface treated). Cement build-ups were performed on the surface-treated dentin with BAC (groups 1-4) and RMGIC (groups 5-8). A universal testing machine was used to measure the SBS and the mode of failure was evaluated using a stereomicroscope. Statistical analysis was performed using an analysis of variance and Tukey's post hoc test, at a significance level of p < 0.001. The highest SBS values were observed in group 8, ECL + EDTA + Tetric-N-Bond + RMGIC (21.54 ± 3.524 MPa) and the lowest SBS values were displayed by group 1, with no surface treatment and BAC application (11.99 ± 0.821 MPa). The majority of failures were found to be mixed in lased dentin-treated dentin surfaces. BAC when bonded to dentin surfaces conditioned with ECL showed lower SBS in comparison to RMGIC. Conditioning of dentin with ECL and a bonding agent (Tetric-N-bond) improved bond strength scores for BAC and RMGIC. Use of EDTA improved bond strength values when bonded to BAC and RMGIC; however, this improvement was not statistically significant.

Effect of Fiber Laser Irradiation on the Shear Bond Strength between Acrylic Resin and Titanium.

Objectives The aim of this study is to investigate the shear bond strength of an acrylic resin to titanium after different surface treatment methods. Material and Methods A total of seventy-two disc-shaped specimens (10 mm × 10 mm × 2 mm) were prepared from titanium alloy. The specimens were randomly allocated to six equal groups: Group S (sandblasting), Group MP (metal primer), Group 10W (fiber laser 10 W), Group 20W (fiber laser 20 W), Group 10WMP (fiber laser 10 W+metal primer), and Group 20WMP (fiber laser 20 W+metal primer). All of the specimens were thermocycled up to 5000 cycles. After thermal cycling, a shear bond strength test was conducted. The shear bond strength data were analyzed with one-way ANOVA and Tukey's post hoc pairwise comparisons (p < 0.05). Results While the highest values were determined in Group MP, the lowest values were observed in Group S. Additionally, Group MP exhibited significantly higher shear bond strength values than any of the other groups (p < 0.05) except Group 10WMP. Similar results were observed between Group MP and Group 10WMP (p > 0.05). The groups in which a metal primer was applied (Group MP, 10WMP, and 20WMP) showed significantly higher values than Group S. The shear bond strength values of Group 10W and Group 20W were similar. Conclusions The application of a metal primer significantly improved the bond strength of acrylic resin to titanium. Fiber laser application may be an alternative method to sandblasting for improving the bond strength of acrylic resin to titanium.

Zirconia Translucency and Cement Systems as Factors Influencing the Zirconia-Titanium and Zirconia-Zirconia Shear Bond Strength.

To evaluate the bonding ability of self-adhesive and dual-cure resin cement systems applied to zirconia materials of different translucency in combination with each other and with titanium. Computer-aided design/computer-assisted manufacture (CAD/CAM) disks of three different zirconia materials (Zenostar MO 0 [medium opacity], MT 0 [medium translucency], and T 1 [translucent], Wieland Dental) were milled and hard sintered in order to obtain cylindrical samples of either 12 mm high × 12 mm diameter (used as a substrate) or 12 mm high × 8 mm diameter (to be bonded to the substrate). CAD/CAM disks of titanium (Starbond Ti4 Disc, S&S Scheftner) were milled in order to obtain a cylinder shape (12 mm high × 8 mm diameter to be bonded to the zirconia substrate). The bonding surfaces were sandblasted with alumina particles (70 μm/2 ATM). Two resin cement systems were tested in this study: a self-adhesive resin cement (SpeedCEM Plus, Ivoclar Vivadent) and a dual-cure resin cement (Variolink Esthetic DC, Ivoclar Vivadent) in combination with a primer (Monobond Plus, Ivoclar Vivadent). The smaller cylinders were bonded to the substrate following the manufacturer's instructions. After 24 hours at 37°C storage, each specimen was subjected to shear bond strength testing in a universal testing machine. The substrate was fixed to the machine, and shear force was applied to the small cylinder close to the bonding interface. Shear bond strength data were statistically analyzed by a three-way analysis of variance (ANOVA) followed by the Tukey test for post hoc comparison (P < .05). No significant differences were found between substrates in the shear bond strength test (P = .078). Variolink Esthetic DC showed a statistically significantly higher bond strength compared with the SpeedCEM Plus (P = .001) with the exception of Zenostar MT substrate (P = .014). The resin cement systems showed high shear bond strength values when zirconia was resin bonded to either titanium or the corresponding zirconia substrate. Different zirconia translucencies did not affect the bond strength. The use of MDP primer and a dual-cure cement showed statistically significantly higher strength compared with the self-adhesive resin cement system with the only exception being the bonding of the translucent zirconia Zenostar MT.

HF etching of CAD/CAM materials: influence of HF concentration and etching time on shear bond strength

BackgroundThe required pretreatment of CAD/CAM ceramic materials before resin composite cement application varies among studies. The aim of the present study was to evaluate the effect of hydrofluoric acid concentration and etching time on the shear bond strength (SBS) of two adhesive and two self-adhesive resin composite cements to different CAD/CAM ceramic materials.MethodsSBS of two adhesive (Panavia V5, Kuraray, [PV5]; Vita Adiva F-Cem, Vita Zahnfabrik, [VAF]) and two self-adhesive (RelyX Unicem 2 Automix, 3 M Espe, [RUN]; Vita Adiva S-Cem, Vita, [VAS]) cements to four different CAD/CAM materials (Vitablocs Mark II, Vita, [VM]; Vita Enamic, Vita, [VE]; e.max CAD, Ivoclar Vivadent, [EC]; Vita Suprinity PC, Vita, [VS]) was measured. The effect of the surface pretreatment by using two different hydrofluoric acid products (HF5% Vita Ceramics Etch, Vita and HF9% buffered, Ultradent Porcelain Etch, Ultradent Products) were assessed at etching times of 0 s, 5 s, 15 s, 30s and 60s for each cement and restorative material combination (n = 10 per group, total n = 1440).ResultsSignificant effects were found for the etching time and cement for all materials with highest shear bond strength for etching times of 60s = 30s = 15 s ≥ 5 s > 0 s and for RUN>PV5 = VAF > VAS (p < 0.05). Etching with HF5% for 5 s to 15 s resulted in higher SBS values, while no differences were observed between HF5% and HF9% buffered when the substrates were etched for 30s to 60s (p < 0.05).ConclusionsWithin the limitations of this study the recommended surface pretreatment of silicate ceramics is HF etching with concentrations of 5% or 9% for 15 s to 60s to achieve highest shear bond strength while the glassy matrix is sufficiently dissolved. The tested resin composite cements can be applied with all tested materials and suggested for clinical application.

Effect of different surface treatments on the repair bond strength of resin composites with titanium

The purpose of this study was to evaluate the effect of different surface treatment combinations on the bonding of composite resins to NiCr and titanium alloys after thermal cycling. Square-shaped specimens (10 mm x 10 mm x 2 mm) were made from NiCr and titanium alloys. The specimens were divided into 6 pretreatment groups (n = 11): (1) machined titanium (control, no treatment); (2) CoJet sand application; (3) grinding with a diamond bur; (4) metal primer application; (5) CoJet sand + metal primer application; and (6) grinding with a diamond bur + metal primer application. The surface roughness of the mechanically treated specimens (control, grinding, CoJet sand) was evaluated. The surface morphology of both metals and elemental composition were examined with SEM and EDS. The composite resin was applied to the specimens. Shear bond strength (SBS) was tested after thermal cycling (5000 cycles, 5 °C to 55 °C). Failure modes were determined. The data were analyzed using the Shapiro-Wilk test, two-way ANOVA and post hoc Fisher’s LSD test (p = .05). For titanium specimens, the grinding + metal primer exhibited higher values than the other groups, and all groups showed higher SBS values than the control group. Combined use of CoJet sand, grinding with a diamond bur, and metal primer application would be useful for enhancing the bond strength of composite resin to titanium. The grinding of the NiCr surface with a diamond bur is the only method that could improve the bond strength of a composite resin compared to the other methods.

The effect of curing lights and modes on dentin bond strength of bulk-fill composites applied in different thickness

To investigate shear bond strength (SBS) to dentin of a conventional and three bulk-fill composites applied in different increment thickness and cured by mono- and multi-wave LED LCUs. Two hundred and fifty-two extracted sound human molars were prepared for SBS test. The teeth were divided into four groups according to the resin composites used. Conventional composite: Tetric N-Ceram (control); high-viscosity bulk-fills: Tetric N-Ceram Bulk Fill, X-tra Fil, and SonicFill. Each group was subdivided (n = 7) according to increment thickness (2, 4, and 6 mm) and cured by standard mode of a mono-wave LED or two different modes (standard and xtra power) of a multi-wave LED. The failure mode was stereomicroscopically determined at 40× magnification. Data were analyzed using Three-way ANOVA and further comparisons were assessed by Bonferroni’s multiple comparison test. There were no significant differences within X-tra fil and Tetric N-Ceram Bulk Fill groups for any of the variables (p > 0.05). A significant decrease in SBS values with increase of layer thickness was observed for SonicFill and control groups. Also, curing mode had a significant effect on both composites at 6 mm thickness and standard mode of multi-wave LED caused the highest SBS value (p ˂ 0.05). Adhesive failure was the most common fracture pattern especially at 6 mm thickness applications. Based on the results of this study, the bulk-fill composites can be safely applied in one-step with 4 mm increments, although the examined composites performed better at 2 mm thickness. The performance of the composites at 6 mm increment may show differences related to the curing lights and modes.

Comparative Effectiveness of Multiple Laser Scanning and Conventional Techniques on Zirconia Shear Bond Strength

This study aimed to compare the impact of different laser scanning with that of conventional methods on zirconia surface treatment through evaluation of shear bond strength (SBS) values. One hundred and thirty-two sintered zirconia cubic-samples were prepared and randomly divided into six study groups: milling control (without surface treatment); grinding; sandblasting; and three-times, four-times, and five-times laser scanning groups. The treatment process for the first three groups was performed before the zirconia coating, while the last three groups were treated after zirconia coating with veneer slurry through a spraying technique. In the current study, the surface roughness Ra, contact angle measurement, phase transformation, topography and interfaces, SBS in unaged and aged conditions, and fracture mode patterns of zirconia cores were investigated. The results were analyzed using laser confocal scanning microscopy, drop analyzer, X-ray diffractometry (XRD), scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS), universal testing machine and stereomicroscope. The results indicated that three-times laser scanned specimens presented higher Ra values than the other studied groups. The minimum contact angle value was detected in the mentioned group, while the control group presented the highest value. The XRD showed phase transformation from tetragonal to monoclinic t–m following grinding and sandblasting. However, the laser scanned specimens and the control group preserved the structural integrity of the zirconia core, presenting the tetragonal phase only. The highest SBS values were recorded in specimens treated with three-times laser scanning in the unaged and aged conditions. A mixed fracture was a common fracture pattern among the studied groups. The results confirmed that SBS could be optimized through three-times laser scanning and it provided better adhesion between zirconia and the veneer ceramic material. Multiple scanning processes of more than three times are not recommended for zirconia surface treatment.

In Vitro Evaluation of Bond Strength between Zirconia Core and CAD/CAM-Produced Veneers.

To evaluate the shear bond strength between various CAD/CAM veneer materials and the zirconia ceramic core. Ninety square prism zirconia specimens (10 specimens per each group, n = 10) in dimensions of 10 × 5 × 5 mm were prepared. Eighty square prism veneering specimens (40 feldspathic ceramic [Cerec Bloc] and 40 lithium disilicate [IPS e.max CAD]) in dimensions of 3 × 3 × 1 mm were connected to zirconia specimens. Conventional layering was applied to the remaining zirconia specimens as control group (n = 10). CAD/CAM-produced veneers were connected to the zirconia specimens using fusion porcelain or resin cement. One of following treatments were applied to the cemented specimens: no surface treatment, HF etching of the veneering material, or HF acid etching of the veneer in combination with the application of a glaze layer to the zirconia surface. Following the veneering procedures, a shear bond strength test was performed at a speed of 1 mm/min using a universal testing machine. Univariate ANOVA (α = 0.05) was performed for statistical analyses of the obtained data. Statistically significant differences were not found among the materials (F = 0.176, p = 0.656), while statistically significant differences were found amongst the veneering procedures (F = 57.921, p < 0.001). Statistical differences were observed between the groups (F = 13.766, p < 0.001). The highest shear bond strength values were observed in IPS e.max CAD specimens connected to zirconia with low fusion porcelain (27.11 ± 7.7 MPa), and the lowest values were observed in IPS e.max CAD specimens connected to zirconia with resin cement without surface treatment (9.82 ± 2.8 MPa). The application of fusion porcelain with IPS e.max CAD (p = 0.967) and Cerec Blocs (p = 1.00) showed statistically similar results to those with conventional layering. The application of fusion porcelain to bond zirconia and digitally produced veneering material can serve as an alternative veneering method to the conventional layering method by accelerating and facilitating clinical and laboratory stages.