Evaluation of the surface roughness and morphologic features of Y-TZP ceramics after different surface treatments

Influence of Different Surface Treatments on the Bond Strength of Yttria-Stabilized Tetragonal Zirconia Ceramic

Objective: This in vitro study evaluates the shear bond strength (SBS) of yttria-stabilized tetragonal zirconia (Y-TZP) and resin cement after different surface treatments. Materials and methods: Forty-eight ceramic cubes were divided into four groups (n = 12): G1 (control) sandblasting with Al2O3; G2-sandblasting with silica-coated Al2O3 (Rocatec); G3-Rocatec + CO2 laser; and G4-CO2 laser + Rocatec. A metallic primer was applied to the pretreated ceramic. A rubber ring was adapted on the central area, and then, the resin cement was inserted into the matrix and photoactivated. The samples were evaluated regarding surface roughness (Ra), SBS, failure type, and qualitatively with scanning electron microscopy (SEM). The data were analyzed by one-way analysis of variance followed by Tukey's test (p < 0.05). Results: The mean values of Ra (μm) were as follows: G1-4.52a, G2-4.24a,b, G3-4.10a,b, and G4-2.90b and the mean values of SBS (MPa) were as follows: G1-7.84a , G2-4.41b , G3-4.61b and G4-6.14a,b. SEM analyses showed superficial irregularities for all groups, being more prominent for G1. The presence of silica deposits was observed for G2, G3, and G4, but in the last two groups there were some linear areas, promoted by the fusion of silica, due to the thermomechanical action of the CO2 laser. Conclusions: The surface treatment with CO2 laser + Rocatec, using one MDP-based cement, can be an alternative protocol for the adhesion cementation of Y-TZP ceramic since it was as effective as the conventional pretreatment with aluminum oxide sandblasting.

Comparison of retention of monolithic zirconia crowns with alumina airborne-particle abraded and nonabraded intaglio using three different cements: A clinical simulation

STATEMENT OF PROBLEM

The necessity of roughening the intaglio surface of zirconia crowns to achieve adequate retention is unclear.

PURPOSE

The purpose of this clinical simulation study was to evaluate the retention of airborne-particle-abraded and nonabraded monolithic zirconia crowns using 3 different cement types.

MATERIAL AND METHODS

Extracted human molars were used and prepared with a 10-degree taper. Impressions were made of the prepared teeth with a polyvinyl siloxane (PVS) material, and dies were made with Type 4 gypsum. Each die was scanned with a NobelProcera 1G Scanner, and the standard tessellation language (STL) files were transferred electronically to the Nobel Biocare production site, where a bar was added virtually on top of each crown and parameters were set for milling. Seventy-two Procera zirconia crowns were generated, of which half were airborne-particle abraded on the intaglio surface with 50-µm alumina particles at 400 to 500 kPa for 15 seconds. The other 36 received no intaglio treatment other than cleaning. Both groups of 36 crowns were divided into 3 subgroups of 12 specimens. The area of each preparation was calculated using a computer-aided design software program. The specimens were distributed to attain similar mean surface areas among the cementation groups. The crowns were cemented onto the specimen with a controlled force of 196 N. The 3 cements used were self-adhesive, modified resin RelyX Unicem Aplicap, resin-modified glass ionomer RelyX Luting, and a composite resin, Panavia F2.0 with ED Primer A & B. All specimens were thermocycled (5 °C to 55 °C) for 5000 cycles and then removed axially with a universal testing machine (Instron Model 5585H) at a crosshead speed of 0.5 mm/min. The removal force was recorded, and stress of dislodgement was calculated for each crown. A 2-way analysis of variance was used for statistical analyses. The type of failure was analyzed with the chi-squared test of association for independent samples (α=.05 for all tests).

RESULTS

The mean dislodging force for crowns with airborne-particle abraded intaglio was 5.4 MPa, which was statistically greater than the mean of 3.2 MPa for nonabraded specimens (P<.001). No significant differences related to the dislodging stresses were detected among the 3 cements (P=.109). The mode of failure was similar whether abraded or not, with 50% of specimens retaining cement in the crown after separation.

CONCLUSIONS

Alumina airborne-particle abrasion of the intaglio of zirconia to create surface roughness is beneficial in retaining the crowns, regardless of the cement type. The nonabraded crowns demonstrated significantly lower retentive stress with crown removal. The principal mode of failure was similar whether the zirconia intaglio was airborne-particle abraded or not. The most common mode of failure (>50% of specimens) was at least three-fourths of the cement remaining within the crown.

The Use of Warm Air for Solvent Evaporation in Adhesive Dentistry: A Meta-Analysis of In Vitro Studies

Any excess solvent from dental adhesive systems must be eliminated prior to material photopolymerization. For this purpose, numerous approaches have been proposed, including the use of a warm air stream. This study aimed to investigate the effect of different temperatures of warm air blowing used for solvent evaporation on the bond strength of resin-based materials to dental and nondental substrates. Two different reviewers screened the literature in diverse electronic databases. In vitro studies recording the effect of warm air blowing to evaporate solvents of adhesive systems on the bond strength of resin-based materials to direct and indirect substrates were included. A total of 6626 articles were retrieved from all databases. From this, 28 articles were included in the qualitative analysis, and 27 remained for the quantitative analysis. The results of the meta-analysis for etch-and-rinse adhesives revealed that the use of warm air for solvent evaporation was statistically significantly higher (p = 0.005). For self-etch adhesives and silane-based materials, this effect was observed too (p < 0.001). The use of a warm air stream for solvent evaporation enhanced the bonding performance of alcohol-/water-based adhesive systems for dentin. This effect seems to be similar when a silane coupling agent is submitted to a heat treatment before the cementation of a glass-based ceramic.

Repair bond strength of different CAD-CAM ceramics after various surface treatments combined with laser irradiation

The aim of this study was to evaluate the effect of different surface treatments combined with laser irradiation on the shear bond strength of different CAD-CAM ceramics to composite resin. A total of hundred forty-seven ceramic specimens with thicknesses of 2.5 mm were prepared from three different CAD-CAM ceramics (an yttrium oxide partially stabilized tetragonal zirconia polycrystal (Y-TZP); a zirconia-reinforced lithium silicate glass ceramic (ZLS); and a lithium disilicate-strengthened lithium aluminosilicate glass ceramic (LD-LAS)) and subjected to seven groups of treatment (n = 7): (1) control (no treatment), (2) Er:YAG laser irradiation, (3) Nd:YAG laser irradiation, (4) etching with hydrofluoric acid (HFA), (5) Er:YAG + HFA, (6) Nd:YAG + HFA, and (7) sandblasting. After surface treatment procedures, a ceramic primer (Clearfil Ceramic Primer Plus, Kuraray, Japan) was applied to the ceramics. Bonding agent (Single Bond Universal Adhesive, 3 M ESPE, USA) was then applied, and the composite resin (Estelite Sigma Quick, Kuraray, Japan) was layered on the ceramic surfaces. The shear bond strength test was performed using a universal testing machine at a load of 0.5 mm/min. Data were analyzed by 2-way analysis of variance (ANOVA), and the Bonferroni correction was used for pairwise comparisons (α = 0.05). Compared to the bond strength of the control group, irradiation by Er:YAG and Nd:YAG lasers alone improved the bond strength of the composite resin to the Y-TZP (P < 0.001) but did not change the bond strength of composite resin to the ZLS and LD-LAS (P > 0.05). Compared to the bond strength of the control group, etching with HFA alone increased the bond strength of the composite resin to the ZLS and LD-LAS (P < 0.001) but did not affect the bond strength of the composite resin to the Y-TZP (P > 0.05). The highest bond strength of ZLS was obtained using HFA + Er:YAG, and the highest bond strength for LD-LAS was obtained using HFA + Nd:YAG. It was concluded that Er:YAG and Nd:YAG laser treatments presented the highest repair bond strength between the composite resin and Y-TZP ceramics. Er:YAG and Nd:YAG laser treatments in conjuction with HFA presented the highest repair bond strength between the composite resin and the glassy ceramics, ZLS, and LD + LAS.

Surface roughness and characteristics of CAD/CAM zirconia and glass ceramics after combined treatment procedures

BACKGROUND

The roughening of the inner surface of a fixed ceramic restoration is an important factor for the bonding process. The aim of this study is to investigate the effect of combined surface treatments (acid etching, air-abrasion and Er: YAG Laser) on surface roughness of CAD/CAM fabricated zirconia (ZrO₂) and lithium-disilicate glass ceramics (LDS).

METHODS

Sixty ZrO₂ (Ceramill Zi) and LDS (IPS e.max CAD) specimens, (5 mm in width, 5 mm in length and 1.5 mm in height) were fabricated using CAD/CAM and sintered according to the manufacturer's instructions. All specimens subjected to three surface treatment combinations; etching with 4% hydrofluoric acide (HF), airborne-particle abrasion with 110-μm alumina (Al₂O₃) (AP) and Er:YAG laser (Er:YAG) (Group A-HF + AP; Group B-Er:YAG + AP, and Group C-Er:YAG + HF). Perthometer was used to measure the surface roughness of the specimens before and after the tretments.

RESULTS

Group A presented the highest Ra (LDS 0.81 ± 0.27 and ZrO₂ 0.67 ± 0.21 after treatment) and Group C the lowest (LDS 0.45 ± 0.13 and ZrO₂ 0.26 ± 0.07, after treatment). Compared with before treatment, the Ra were significantly different only in Group A both ZrO₂ and LDS after treatment (p < 0.05). Qualitative SEM images suggested the surface topography of the ZrO₂ was smoother than the LDS. Less surface changes were observed in the Er:YAG combined procedures than HF + AP.

CONCLUSIONS

HF + AP was significantly succesful in modifying the ceramic surface. Er:YAG did not sufficiently promote the surface topography, even if combined with any other treatments. Overall, surface tretments on ZrO₂ not easier than LDS.

Effect of surface treatment, ferrule height, and luting agent type on pull-out bond strength of monolithic zirconia endocrowns

PURPOSE

To evaluate the effect of different surface treatments, ferrule heights, and luting agents on the pull-out bond strength (PBS) of computer-aided design/computer-aided manufacturing (CAD-CAM) monolithic endocrowns.

METHODS

After endodontic treatment and preparation for two endocrown designs (ferrule height 0 mm or 2 mm), CAD-CAM monolithic zirconia endocrowns were fabricated for 80 mandibular molars. Each endocrown design group was then divided on the basis of surface treatment into two groups: half were air-abraded and half were air-abraded/laser-irradiated. Then, all treated groups were further divided into two subgroups (n = 10) and cemented to teeth with either a 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing resin luting agent (Panavia SA) or a combination of MDP-containing primer and MDP-free resin luting agent (Monobond Plus/Multilink Automix). PBS was measured with a universal test machine after simulated chewing and thermocycling. Three-way ANOVA and the post-hoc Bonferroni test were used for statistical analysis.

RESULTS

PBS was significantly associated with type of surface treatment, type of luting agent, and ferrule height. Air-abraded/laser-irradiated endocrowns with a 2-mm ferrule that were cemented with Monobond Plus/Multilink Automix had the highest PBS (P < 0.05).

CONCLUSION

Surface treatment with air abrasion/laser irradiation, presence of a ferrule, and priming with an MDP-containing primer increased the PBS of monolithic zirconia endocrowns.

Effect of Helium Plasma Exposure on Wettability and Shear Bond Strength between the Zirconia Core and Feldspathic Veneering Ceramic: An In Vitro Study

Introduction. The present study aimed to evaluate the effect of helium plasma treatment on the wettability of zirconia surface and on the shear bond strength between the dental zirconia core and feldspathic veneering ceramic. Methods. 128 zirconia specimens were prepared, polished, and then divided into four groups: control, Zr, FC, and Zr/FC. In Zr and Zr/FC groups, the zirconia blocks were treated by helium plasma for 60 s. In FC and Zr/FC, the feldspathic ceramic powder received 60 s of plasma treatment. Then, the feldspathic powder was applied on the zirconia blocks. Half of the specimens in each group were sintered in a tube furnace, and the contact angle between the zirconia core and feldspathic ceramic was measured at different time intervals. The other half were sintered in a ceramic furnace and then subjected to thermocycling. The shear bond strength was measured using a universal testing machine. The failure mode was assessed using a stereomicroscope. Data were analyzed by one-way ANOVA test, and the statistical significance was considered less than 0.05. Results. There was no significant difference in the mean contact angle and the shear bond strength values of the experimental groups ( $P>0.05$ ). The mean contact angle decreased significantly in all groups over time ( $P<0.001$ ). The modes of failure were predominantly mixed in all groups. Conclusion. The helium plasma applied on either dental zirconia core or feldspathic ceramic powder could not improve the zirconia surface wettability and the shear bond strength between the two ceramics.

Color Changes Associated with Sandblasting, Hydrofluoric Acid Etching, and Er:YAG Laser Irradiation of Milled Feldspathic Porcelain Laminate Veneers

OBJECTIVES

To evaluate color changes in milled feldspathic porcelain laminate veneers following hydrofluoric acid etching (HFA), sandblasting (SB), or Er:YAG laser irradiation (LI).

METHODS AND MATERIALS

Disc-shaped specimens (thickness=1 mm, diameter=8 mm) were milled from feldspathic porcelain blocks (n=40). Glazed specimens were randomly assigned to four subgroups (n=10 each) according to surface treatment: negative control, HFA, SB, and LI. A layer of translucent, light-cured resin cement (thickness=0.1 mm) was then applied following silanization. The color was characterized by the L*, a*, and b* uniform color space (CIE) using a reflection spectrophotometer. CIEDE2000 (ΔE00) was calculated to determine the color difference between each surface treatment and negative control groups. Data were statistically analyzed using analysis of variance (ANOVA), Kruskal-Wallis, and Dunn-Bonferroni post hoc tests.

RESULTS

There were no significant differences in CIEL* and CIEb* coordinates between negative control and all surface treatment groups (p≥0.108). The SB group demonstrated significantly lower mean CIEa* (higher greenish hue) compared to other groups (p≤0.003). HFA exhibited significantly higher CIEa* (closer to red) when compared to LI (p=0.039). LI induced the smallest overall color change compared to negative control (ΔE00=1.43 [1.07]). However, the differences in ΔE00 values were not statistically significant (p=0.648).

CONCLUSIONS

The tested surface treatments did not affect the lightness or the yellowness of the 1-mm-thick milled feldspathic porcelain veneers. However, sandblasting resulted in a significant increase in the greenish hue. The Er:YAG laser resulted in the closest ΔE00 (1.43) to the 50:50% perceptibility threshold (ΔE00=1.2).

The effect of surface treatment and thermocycling on the shear bond strength of orthodontic brackets to the Y-TZP zirconia ceramics: A systematic review

INTRODUCTION

Various surface pre-treatment methods have been adapted to optimize the bonding between the zirconia ceramics and the orthodontic brackets.

OBJECTIVE

This review is aimed at systematically analyzing the relevant data available in the literature, to find out the most effective and durable bonding protocol.

METHODS

Database search was conducted in PubMed, Scopus, and ScienceDirect, during September 2020. The review was conducted according to the PRISMA guidelines.

RESULTS

Based on the inclusion criteria, 19 articles were selected for qualitative analysis. Meta-analysis could not be performed due to the heterogeneity of the methodology among the studies. Most of the studies scored medium risk of bias. Compared to the untreated surface, surface pretreatments like sandblasting and lasers were advantageous. Primers and universal adhesive were mostly used as an adjunct to the mechanical pretreatment of the zirconia surface. In most studies, thermocycling seemed to lower the shear bond strength (SBS) of the orthodontic brackets.

CONCLUSION

Based on this qualitative review, surface pretreatments with lasers and sandblasting can be suggested to optimize the bracket bond strength. To clarify this finding, meta-analysis is anticipated. Hence, high heterogeneity of the included studies demands standardization of the methodology.

The Use of Lasers in Dental Materials: A Review

Lasers have been well integrated in clinical dentistry for the last two decades, providing clinical alternatives in the management of both soft and hard tissues with an expanding use in the field of dental materials. One of their main advantages is that they can deliver very low to very high concentrated power at an exact point on any substrate by all possible means. The aim of this review is to thoroughly analyze the use of lasers in the processing of dental materials and to enlighten the new trends in laser technology focused on dental material management. New approaches for the elaboration of dental materials that require high energy levels and delicate processing, such as metals, ceramics, and resins are provided, while time consuming laboratory procedures, such as cutting restorative materials, welding, and sintering are facilitated. In addition, surface characteristics of titanium alloys and high strength ceramics can be altered. Finally, the potential of lasers to increase the adhesion of zirconia ceramics to different substrates has been tested for all laser devices, including a new ultrafast generation of lasers.

Effects of Different Laser Treatments on Some Properties of the Zirconia-Porcelain Interface

Introduction: This study was performed to compare the effect of Fractional CO₂ laser or Q switched Nd:YAG laser of surface treatment on the shear bond strength of zirconia-porcelain interface. Methods: Fractional CO₂ laser at 30 W, 2 ms, time interval 1 ms, distance between spots 0.3 mm, and number of scans is (4) or Q switched Nd:YAG laser at 30 J/mm² and 10 Hz were used to assess the shear bond strength of zirconia to porcelain. Pre-sintered zirconia specimens were divided into three groups (n = 10) according to the surface treatment technique used: (a) untreated (Control) group; (b) CO₂ group; (c) Nd:YAG group. All samples were then sintered and veneered with porcelain according to the manufacturer's instructions. Surface morphology was examined using a light microscope, the surface roughness test was done by the atomic force microscope (AFM), and the shear bond strength (SBS) test was done by a universal testing machine. After debonding following shear bond test, zirconia surfaces were examined under a light microscope to determine their fracture mode. Results: The Results of this study showed that the lowest SBS was recorded in the control group, and the highest SBS recorded in the Fractional CO₂ group, followed by the Q switched Nd:YAG laser group, as well as an increase in surface roughness and change in the morphology and mode of failure in the experimental groups. Conclusion: This study shows that Fractional CO₂ laser and Q switched Nd:YAG laser treatments significantly increase the bond strength than untreated zirconia.

Effects of laser modalities on shear bond strengths of composite superstructure to zirconia and PEEK infrastructures: an in vitro study

In the last decade, demand for metal-free esthetic restorations has grown considerably due to the development of materials to fulfill the need for an esthetic prosthesis. We examined the effects of erbium-doped yttrium aluminum garnet (Er:YAG), neodymium-doped yttrium aluminum garnet (Nd:YAG), and potassium titanyl phosphate (KTP) laser applications on the shear bond strength (SBS) of nanohybrid composite superstructures to zirconia and PEEK infrastructures. Zirconia and PEEK specimens were prepared with CAD/CAM technology in accordance with ISO 11405 standards. The disc-shaped samples were randomly separated into four groups (n = 8) according to applied laser type: no treatment and Er:YAG, Nd:YAG, and KTP lasers. Nanohybrid composite resin was applied as a veneering material to each infrastructure. After surface treatment of infrastructures by the lasers, the SBS test was carried out to determine the bonding of infrastructures, which were also examined with a stereomicroscope. The SBS were significantly higher in the PEEK specimens treated with the studied lasers. Nd:YAG laser was the most effective method, followed by Er:YAG laser and KTP laser. The lowest SBS value was obtained in the no-treatment group. Stereomicroscopically, the studied lasers produced different irregularities on the infrastructures. PEEK as a framework provides meaningfully higher bonding strength to composite resins compared to zirconia. Nd:YAG, Er:YAG, and KTP, in descending order, are efficacious in increasing the attachment of studied structures.

[Adhesion of dental cements to zirconia restorations (part 1)]

The analysis of modern scientific data on traditional and adhesive fixation of zirconia restorations, adhesion of various cements to zirconium dioxide, methods of surface preparation of ceramic restorations is presented. Micromechanical methods of preparation for cementation of the surface of a zirconia dental prosthesis are discussed in Part 1.

Nanosecond pulsed fiber laser irradiation for enhanced zirconia crown adhesion: Morphological, chemical, thermal and mechanical analysis

The increasing demand for aesthetics, together with advancements in technology, have contributed to the rise in popularity of all-ceramic restorations. In the last two decades, the continuous progression in ceramic materials science for dental applications has permitted the fabrication of high-strength materials. Amongst these, zirconia-based ceramics have improved in terms of fracture resistance and long-term viability in comparison with other silica-based materials. Unfortunately, while bonding of resin cement-silica ceramics can be strengthened through creation of a porous surface by applying hydrofluoric acid (5%-9.5%) and a subsequent silane coupling agent, the glass-free polycrystalline microstructure of zirconia ceramics does not allow such a reaction. The aim of the present in vitro study was to observe the effect of 1070 nm fiber nanosecond pulse laser irradiation on zirconia samples through morphological analysis (profilometry, SEM), thermal recording with Fiber Bragg Gratings (FBGs), elemental composition analysis (EDX) and bond strength testing (mechanical tests) in order to evaluate the possible advantages of this kind of treatment on zirconia surfaces, as well as to show the potential side effects and changes in chemical composition. Despite laser irradiation with a 1070 nm wavelength fiber laser and correct process parameters demonstrating suitable outcomes in terms of improved surface roughness and minimal thermal damage, comparison between irradiated and unirradiated samples did not exhibit statistically significant differences in terms of bonding strength.

Effect of Air-Abraded Versus Laser-Fused Fluorapatite Glass-Ceramics on Shear Bond Strength of Repair Materials to Zirconia

Zirconia repair could be a feasible alternative option to total replacement in fractured zirconia-based restorations. Maximising the bond strength by enriching zirconia with fluorapatite glass-ceramics (FGC) powder has been addressed and compared to other surface treatments. Besides resin composite, other repair materials have been proposed and compared. Zirconia blocks received different surface treatments (A-sandblasting with tribochemical silica-coated alumina (CoJet). B-sandblasting with FGC powder (FGC), C-fluorapatite glass-ceramic coat+ neodymium-doped yttrium aluminum garnet laser irradiation (FGC + Nd: YAG), and D-no surface treatment). The surface roughness, topography, and crystallinity were investigated by a profilometer, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses, respectively. For each surface treatment, three repair materials (feldspathic porcelain, lithium disilicate, and resin composite) were bonded to zirconia with 10, Methacryloyloxydecyl dihydrogen phosphate (MDP)-Monobond Plus/ Multilink Automix. Bonded specimens were thermocycled for 10,000 cycles and tested for shear bond strength (SBS) at a speed of 1 mm/min, followed by the analysis of the mode of failure. FGC + Nd: YAG laser group reported the highest surface roughness and monoclinic content compared to CoJet, FGC, and control groups. The highest mean SBS was found in FGC-blasted zirconia, followed by FGC + Nd: YAG laser and CoJet treated groups. However, the lowest SBS was found in control groups regardless of the repair material. Sandblasting zirconia with FGC powder increased SBS of resin to zirconia with lower monoclinic phase transformation compared to FGC + Nd: YAG or CoJet groups.

Effect of Nd:YAG Laser with/without Graphite Coating on Bonding of Lithium Disilicate Glass-Ceramic to Human Dentin

This study evaluated the effect of different surface treatments on the tensile bond strength between lithium disilicate glass-ceramics, resin cement, and dentin. Fifty truncated cone-shape glass-ceramics were divided into five groups (n = 10): G1, control: 10% hydrofluoric acid (HF); G2, Nd:YAG laser + silane; G3, Sil + Nd:YAG laser; G4, graphite + Nd:YAG laser + Sil; and G5, graphite + Sil + Nd:YAG laser. Fifty human third-molars were cut to cylindrical shape and polished to standardize the bonding surfaces. The glass-ceramic specimens were bonded to dentin with a dual-cured resin cement and stored in distilled water for 24 h at 37ºC. Tensile testing was performed on a universal testing machine (10 Kgf load cell at 1 mm/min) until failure. The bond strength values (mean ± SD) in MPa were G1 (9.4 ± 2.3), G2 (9.7 ± 2.0), G3 (6.7 ± 1.9), G4 (4.6 ± 1.1), and G5 (1.2 ± 0.3). Nd:YAG laser and HF improve the bond strength between lithium disilicate glass-ceramics, resin cement, and dentin. The application of a graphite layer prior to Nd:YAG laser irradiation negatively affects this bonding and presented inferior results.

Effect of silica coating and laser treatment on the flexural strength, surface characteristics, and bond strength of a dental zirconia

This study investigated the effect of irradiation with an erbium-doped yttrium aluminium garnet (Er:YAG) laser and coating with silica on the surface characteristics, bond strength, and flexural strength of dental zirconia. Three hundred and forty-three standard zirconia specimens were created, and 49 were assigned to each of seven surface treatment groups: (i) no treatment; Er:YAG laser (80 mJ/2 Hz) with pulse widths of 50 μs (ii), 100 μs (iii), 300 μs (iv), or 600 μs (v); or tribochemical silica coating at the partially sintered stage (vi) or after sintering was complete (vii). All specimens were sintered after the surface treatments, except for the group in which specimens were sintered before treatment. The study outcomes were roughness, surface loss, microshear bond strength (μSBS), and biaxial flexural strength (BFS). Mean roughness and surface loss values were significantly higher in specimens from irradiated groups than in those from silica-coated groups. Regarding μSBS, after aging, specimens from all experimental groups presented very low and similar μSBS values, irrespective of the surface treatment. Silica coating after sintering yielded the highest BFS (1149.5 ± 167.6 MPa), while coating partially sintered specimens with silica resulted a BFS (826.9 ± 60.9 MPa) similar to that of the untreated control group (794.9 ± 101.7 MPa). Laser treatments, irrespective of pulse width used, significantly decreased the BFS. In the group treated with laser at 300 μs pulse width, specimens exhibited the lowest BFS value (514.1 ± 71.5 MPa). Adhesion to zirconia was not stable after aging, regardless of the surface treatment implemented.

Laser Treatment of Fiber Post and Final Push-Out Bond Strength: A Systematic Review and Meta-Analysis

Purpose: This review article tries to answer this question: "What are the effects of laser surface treatment of fiber posts (FPs), compared with other surface roughening methods, on bond strength of cemented FPs?" Methods: Search was carried out in six electronic databases by focusing on defined key words. Related titles and abstracts, up to March 2019, were collected, read, and selected for quality assessments. A total of 2408 articles were included in the study at the initial stage of the searching phase. Results: Finally, seven studies were recognized to be reliable to be reviewed and meta data analysis in the study. All the studies were in vitro with a total of 340 samples. None of the Er:YAG (-0.27, 95% CI: -2.29 to 1.76; p = 0.79) and Er,Cr:YSGG (-0.04, 95% CI: -1.43 to 1.35; p = 0.95) treated samples showed any significant overall mean differences in final push-out bond strength (PBS) compared with the control groups. Conclusions: Laser pretreatment of FP surfaces might not be effective in providing high PBS. FP surface are susceptible to damage of high-level laser irradiation and might show decreased bond strength.

Retention and Clinical Performance of Zirconia Crowns: A Comprehensive Review

Zirconia has been used for rehabilitation of edentulous spaces approximately for a decade, and there have been several reports regarding the clinical performance and retention of zirconia crowns. Outstanding mechanical properties, biocompatibility, and excellent aesthetics make zirconia-based crowns as a popular crown among the current all-ceramic crowns in restorative dentistry. However, restoration with a zirconia crown is a challenging treatment. The goal of this study was to assess the current literature to summarize the studies reporting the effective risk factors on retention of zirconia crowns to provide clinicians with a useful point of view in the decision-making process for use of these restorations. Literature based-search was performed to find related articles until August 2020 using EMBASE, Google Scholar, and MEDLINE. Search terms used were “zirconia restorations properties,” “zirconia crowns clinical performance,” “zirconia crown survival,” “biological complications,” and “zirconia crown retention.” Results were limited to papers available in English. The references of all related literature were also searched for further citations. Overall, although clinical long-term and follow-up studies are a vital requirement to conclude that zirconia has great reliability, it seems that zirconia crown restorations are both well tolerated and sufficiently resistant.

Mechanical properties of glass-fibre-reinforced composite posts after laser irradiation with different energy densities

The aim of the present study was to evaluate the effect of the surface treatments on flexural strengths and flexural modulus of glass-fibre-reinforced composite (GFRC) posts. Sixty-three posts were randomly divided into 9 groups (n = 7), and various surface treatments were performed. The control group was left untreated. Other groups were treated with 9% hydrofluoric acid, sandblasting with 120 µm Al₂ O₃ particles and Er,Cr:YSGG laser irradiation with different powers (1 W, 2 W, 3 W, 4 W, 5 W and 6 W). The samples were subjected to 3-point bending test, and data were calculated. Statistical analysis was performed. The flexural strengths of fibre posts treated with sandblasting, hydrofluoric acid, 1 W and 2 W laser were statistically similar with control group (P > 0.01). However, the flexural strength of fibre posts treated with 3 W, 4 W, 5 W and 6 W laser was statistically lower than control group (P < 0.01). High laser irradiations cause melting on the post surface and breaks in fibrils.

Oxygen Plasma Improved Shear Strength of Bonding between Zirconia and Composite Resin

Improving the strength of the bonding of zirconia to composite resins remains a challenge in dental restorations. The purpose of this study was to evaluate the shear strength of the bonding of zirconia to composite resins, thereby verifying the hypothesis that as the power of the non-thermal oxygen plasma increases, the bonding strength of the plasma-treated zirconia is increased. The effects of the oxygen plasma power (100, 200, and 400 W) on the surface structure, chemical composition, and hydrophilicity of the zirconia and the strength of the bonding between zirconia and composite resin were investigated. As a result, after different plasma power treatments, the surface structure and phase composition of zirconia were not different from those of zirconia without treatment. However, the oxygen plasma treatment not only reduced carbon adsorption but also greatly increased the hydrophilicity of the zirconia surface. More importantly, the strength of the bonding between the plasma-treated zirconia and composite resin was significantly higher than that in the corresponding control group without plasma treatment. Regardless of whether the zirconia was pristine or sandblasted, the higher the plasma power, the greater the bond strength obtained. The conclusion is that the oxygen plasma treatment of zirconia can effectively improve the strength of the bonding between the zirconia and composite resin without damaging the microstructure and phase composition of the zirconia.

Effect of Surface Treatment With Er:YAG and CO2 Lasers on Shear Bond Strength of Polyether Ether Ketone to Composite Resin Veneers

Introduction: Polyether ether ketone (PEEK) has low surface energy and high resistance to chemical surface treatments. Therefore, different surface treatments such as laser conditioning should be investigated. There is a gap of information regarding the efficacy of laser irradiation in the surface treatment of PEEK, and the efficacy of several laser types needs to be evaluated for this purpose. This study aimed to assess the effect of surface treatment with erbium-doped yttrium aluminum garnet (Er:YAG) and carbon dioxide (CO2) lasers on shear bond strength (SBS) of PEEK to composite resin veneers. Methods: In this experimental study, 60 rectangular-shaped PEEK samples (7 x 7 x 2 mm) were used. The samples were mounted in auto-polymerizing acrylic resin in such a way that only one surface measuring 7x7 mm remained exposed. The samples were then randomly divided into 3 groups (n=20) of control, Er:YAG laser surface treatment (Power=1.5 W, energy density=119.42 J/cm² , irradiation time=20 s) and CO2 laser surface treatment (Power=4 W, energy density=159.22 J/cm² , irradiation time=50 s). The bonding agent and PEEK opaque were applied on the surface of samples and they were veneered with a composite resin using a hollow plastic cylinder with an internal diameter of 4 mm. The SBS was then measured and the data were analyzed using one-way ANOVA, Tukey HSD test and Dunnett's test at 0.05 level of significance. Results: The SBS of the 3 groups was significantly different (P<0.001). The Tukey HSD test revealed that the Er:YAG laser had higher SBS than the CO2 laser group (P<0.001). The Dunnett's test showed that both Er:YAG and CO2 laser groups yielded higher SBS than the control group (P<0.001). Conclusion: The Er:YAG and CO2 laser treatments can increase the SBS of PEEK to composite resin veneers, although the Er:YAG laser seems to be more effective for this purpose.

Does the application of surface treatments in different sintering stages affect flexural strength and optical properties of zirconia?

OBJECTIVE

To investigate the influence of surface treatments conducted in presintering and postsintering stages on flexural strength and optical properties of zirconia.

MATERIALS AND METHODS

Specimens were milled from partially sintered zirconia blocks in different geometries and divided into three main groups as presintered, postsintered, and control groups. Test groups were further divided into three subgroups (n = 10) according to the surface treatments conducted (grinding, Er,Cr:YSGG laser irradiation, air-borne particle abrasion [APA]). Four-point flexural strength (σ) test and Weibull analysis were conducted. Color differences (ΔE₀₀ ) and translucency parameter (TP_ab ) were calculated with a spectrophotometer. Surfaces of specimens were scrutinized under FESEM. Data were statistically analyzed.

RESULTS

Postsintered groups exhibited higher σ values (P < .05). Within all groups, highest and lowest σ values were detected at postsintered and presintered APA groups, respectively (P < .05). All ΔE₀₀ values were above the perceptibility threshold (ΔE₀₀  > 0.8). Higher TP_ab values were obtained and deeper scratches were observed in presintered groups.

CONCLUSIONS

Surface treatments performed at postsintering stage had a favorable effect on the flexural strength of all specimens. Surface treatments performed before sintering increased translucency and caused higher ΔE₀₀ values.

CLINICAL SIGNIFICANCE

Surface treatments performed at different sintering stages can alter mechanical and optical properties of zirconia.

Repair bond strength of composite resin to zirconia restorations after different thermal cycles

PURPOSE

This in vitro study investigated the repair bond strength of the zirconia ceramic after different aging conditions.

MATERIALS AND METHODS

In order to imitate the failure modes of veneered zirconia restorations, veneer ceramic, zirconia, and veneer ceramic-zirconia specimens were prepared and were divided into 4 subgroups as: control (37℃ distilled water for 24 hours ) and 3000, 6000, 12000 thermal cycling groups (n=15). Then, specimens were bonded to composite resin using a porcelain repair kit according to the manufacturer recommendation. The repair bond strength (RBS) test was performed using a universal testing machine (0.5 mm/min). Failure types were analyzed under a stereomicroscope. Two-way ANOVA and Bonferroni test were used for statistical analysis.

RESULTS

The RBS values of zirconia specimens were statistically significant and higher than veneer ceramic and veneer ceramic-zirconia specimens in control, 3000 and 6000 thermal cycling groups (P<.05). When 12000 thermal cycles were applied, the highest value was found in zirconia specimens but there was no statistically significant difference between veneer ceramic and veneer ceramic-zirconia specimens (P>.05). Veneer ceramic specimens exhibited cohesive failure types, zirconia specimens exhibited adhesive failure types, and veneer ceramic-zirconia specimens exhibited predominately mixed failure types.

CONCLUSION

Thermal cycling can adversely affect RBS of composite resin bınded to level of fractured zirconia ceramics.

Shear Bond Strength Between Zirconia and Veneer Ceramic: Effect of Thermocycling and Laser Treatment

Objective: The purpose of this study is to investigate the effect of various presintering and sintered surface treatments and thermocycling on the bond strength between zirconia and veneer ceramics. Background data: Bond stability between zirconia and veneer ceramic is a major concern, and only limited evidence about its longevity is currently available. Moreover, no study has yet evaluated the influence of thermocycling on the bond strength of veneer ceramic to zirconia after Er,Cr:YSGG laser irradiation at different pulse durations and sandblasting. Materials and methods: In this study, 220 nonsintered zirconia specimens were prepared with CAD/CAM and randomly divided into 2 groups; half of the specimens in each group were stored in water for 1 week, and the other half were thermocycled (5000 cycles) between baths of 5°C and 55°C. Specimens were then divided into five subgroups based on the following surface treatments: control (untreated surface), sandblasting (120 μm Al₂O₃), and Er,Cr: YSGG laser irradiations (3 W-8 Hz, 3 W-15 Hz, and 3 W-20 Hz, MGG 6 laser tip, for 20 sec, distance of 10 mm, water/airflow of 55% and 65%). Morphological assessment was done using atomic force microscopy and scanning electron microscopy, and phase transformation was assessed by X-ray diffractometry. All specimens were then veneered with veneering ceramic, and bond strength test using a universal testing device at a 1 mm/min crosshead speed. Data were evaluated by Kruskal-Wallis variance analysis and the Mann-Whitney U test. Results: There was no significant difference in the bonding strength values among the (p > 0.05). Thermocycling reduced the bond strength, but it was not significant (p > 0.05), except for the presintering 20 Hz group (p < 0.02). Conclusions: Application of thermocycling to sintered zirconia specimens may be detrimental to the shear bond strength of zirconia ceramics. Treating the zirconia surface after sintering is not recommended, due to the decrease in bond strength.

Effect of laser irradiation on push-out bond strength of dental fiber posts to composite resin core buildups: A systematic review and meta-analysis

BACKGROUND

The bonding of fiber posts (FPs) to composite resin core buildups is a challenge due to limited penetration of resin to the polymeric matrix of FPs. This review article tries to answer this question: "What are the effects of laser surface treatment of FPs, compared to other surface roughening methods, on push-out bond strength (PBS) of FPs bonded to composite resin core buildups?"

METHODS

Searches were run in seven electronic databases with a focus on proper key words. Related titles and abstracts, up to February 2019, were screened, selected, read and subjected to quality assessments.

RESULTS

After the initial search, a total of 2635 articles were included in the study. Finally, 6 studies were reliable enough in methodology to be included. All the studies were in vitro with a total of 359 samples. Er:YAG (-0.05, 95% CI: -2.96 to 2.86; P = 0.97) and Er,Cr:YSGG (0.84, 95% CI: -0.12 to 1.81; P = 0.08) treated samples showed no significant overall mean differences in final PBS compared to the control groups. Moreover, pretreatment with Er,Cr:YSGG laser and sandblasting with 50 μm alumina showed an overall mean difference of -0.42 for PBS (95% CI: -1.23 to 0.39) with no significant differences.

CONCLUSIONS

Laser irradiation of FPs seems to provide no significant increase in PBS values of FPs bonded to composite resin core buildups. Effects of surface treatment of FPs with laser irradiation and sandblasting with 50 μm alumina might be similar in increasing the final PBS, either.

The impact of laser scanning on zirconia coating and shear bond strength using veneer ceramic material

Laser scanning is one of the methods that can be used for surface treatments of zirconia. Application of the laser to the surface of zirconia has diverse effects, depending on the type of laser. A carbon dioxide (CO₂) laser has high irradiation power and can alter the surface properties. This study investigated the surface coating of zirconia as a core material that subsequently coated with a veneering ceramic (v-c) material. This study compared laser scanning and conventional sintering processes. Various properties including surface topography, interface evaluation, phase transformation, elemental compositions, failure mode patterns, and contact angle were examined through X-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyses. Results were confirmed that the bond strength between the v-c and the substrate recorded through laser scanning was higher than that determined through conventional sintering.

Effect of Simplified Bonding on Shear Bond Strength between Ceramic Brackets and Dental Zirconia

The aim of this study was to evaluate the long term stability of shear bond strength (SBS) when 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) containing universal adhesive was used in the ceramic bracket bonding on dental zirconia. Twenty human maxillary incisors were collected. The ceramic bracket was bonded on the buccal enamel surface after the acid-etching and orthodontic primer application (Group CON). Sixty zirconia specimens were sintered, sandblasted and divided into three experimental groups; group CP—ceramic primer followed by an orthodontic primer; group U—universal adhesive; group CU—ceramic primer followed by a universal adhesive. For each specimen, the bracket was bonded onto the treated surface with composite resin (Transbond XT, 3M ESPE). The SBS tested before (CON0, CP0, U0, CU0) and after the artificial aging (CON1, CP1, U1, CU1). The data were statistically analyzed with the Kruskal–Wallis test at a significance level of 0.05. The mean SBS of CON0, CP0, U0 and CU0 were within the clinically acceptable range without significant differences. After the aging process, SBS decreased in all groups. Among the aged groups, CP1 showed the highest SBS. Based on the results, when bonding ceramic brackets to a dental zirconia surface, we can conclude that ceramic primer used with an orthodontic primer, rather than using a universal adhesive, is recommended.

Evaluation of zirconia surface roughness after aluminum oxide airborne-particle abrasion and the erbium-YAG, neodymium-doped YAG, or CO2 lasers: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Veneer chipping and crown decementation are the most frequent failures in restorations using zirconia as an infrastructure. Increasing the roughness of the zirconia surface has been suggested to address this problem.

PURPOSE

The purpose of this systematic review and meta-analysis was to evaluate yttria-stabilized tetragonal zirconia polycrystal surface roughness, produced with aluminum oxide airborne-particle abrasion and the erbium yttrium aluminum garnet (YAG), neodymium-doped YAG, or CO₂ lasers.

MATERIAL AND METHODS

This study was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. The review identified relevant studies through December 2017 with no limit on the publication year in the search databases: Web of Science, Scopus, and MEDLINE via PubMed. The selected studies were submitted to a risk of bias assessment. The means and standard deviations of roughness were evaluated for the meta-analysis using Review Manager software.

RESULTS

The 17 studies that met all inclusion criteria presented a medium risk of bias. All the treatment methods tested were able to create a roughness on the yttria-stabilized tetragonal zirconia polycrystal surface. The I² test values presented a high heterogeneity among the studies.

CONCLUSIONS

The presintered specimens submitted to airborne-particle abrasion had higher surface roughness compared with abrasion after the sintering process. Irradiation with the neodymium-doped YAG and CO₂ lasers was destructive to the zirconia surfaces. The erbium laser used with lower energy intensity appears to be a promising method for surface treatment.

Effects of laser treatments on surface roughness of zirconium oxide ceramics

BACKGROUND

The aim of this study was to analyze the surface roughness of yttrium stabilized tetragonal polycrystalline zirconia (Y-TZP) ceramics after different laser treatments (CO_2, ER: YAG).

METHODS

5x5x2 mm rectangular prisms of forty eight Y-TZP (Zirkonzahn) ceramic specimens were prepared. In order to standardize surfaces, 600-, 1200- grid silicon carbide papers were used to gradually ground wet on 300 rpm grinding machine for 10 s. Eight groups (n = 6) were randomly formed from the specimens of each ceramic as control (GroupC), sandblasted (GroupS), two different CO₂ laser treatments (Group3W: 3 W and 382 w/cal, Group4W: 4 W and 509w/cal) and four different Er: YAG laser treatments (Group150SP: 150 mJ and 10-Hz with 100μS; Group150SSP: 150 mJ and 10-Hz with 300μS; Group300SP: 300 mJ and 10-Hz with 100μS; Group300SSP: 300 mJ and 10-Hz with 300μS). A profilometer was used to conduct surface roughness measurements (Ra). Surface morphologies of the specimens were evaluated under SEM after laser treatment.

RESULTS

To analyze the data one-way ANOVA and to compare the mean values Tukey HSD tests (α = .05) were used. One - way ANOVA results showed that Group S had the highest Ra value and Group150 SP had the lowest. After sandblasting group the highest value was seen in Group4W. There were no statistically significant differences among Group C, Group3W, Group150SSP, Group300SP, and Group300SSP.

CONCLUSIONS

The study showed that surface roughness of zirconium oxide ceramics was increased with CO2 laser.

Qualitative evaluation of hybrid layer formation using Er:YAG laser in QSP mode for tooth cavity preparations

The purpose of this study was to evaluate the thickness and qualitative characteristics of the hybrid layer after two cavity preparation methods, using Er:YAG laser in QSP mode and conventional carbide burs. Additionally, two different adhesive techniques were investigated using etch-and-rinse and self-etch adhesive systems. Sixty sound human third molars were used and were randomly divided into four groups (n = 15). In the first two groups, large (4 mm length, 3 mm wide, and 3 mm deep) class I cavities were prepared using Er:YAG laser (2.94 μm) in QSP mode, while in the other two groups, the cavities were prepared using carbide burs. After cavity preparations, two different adhesive techniques with GLUMA® 2 Bond (etch-and-rinse) and Clearfil™ Universal Bond Quick (self-etch) were applied. For the qualitative evaluation of the formed hybrid layer, photomicrographs were taken using SEM, and elemental semi-quantitative analysis was performed using EDS to confirm the extent of the hybrid layer. One-way ANOVA was applied to verify the existence of statistically significant differences, followed by Tukey test for post hoc comparisons (Bonferroni corrected), and the level of significance was set at a = 0.05. The laser-treated groups exhibited higher hybrid layer thickness than bur-treated groups (p < 0.001). Between the laser-treated groups, etch-and-rinse technique presented higher hybrid layer thickness than self-etch technique (p < 0.001), while between the bur-treated groups, no significant differences were detected (p = 0.366). Er:YAG laser cavity preparations in QSP mode may be advantageous for adhesion of composite restorations, but more data are necessary to confirm its clinical effectiveness.

Effect of high-power-laser with and without graphite coating on bonding of resin cement to lithium disilicate ceramic

The present study evaluated the effect of different high-power-laser surface treatments on the bond strength between resin cement and disilicate ceramic. Lithium disilicate ceramic specimens with truncated cones shape were prepared and divided into 5 groups: HF (hydrofluoric acid-etching), Er:YAG laser + HF, Graphite + Er:YAG laser + HF, Nd:YAG laser + HF, and Graphite + Nd:YAG laser + HF. The treated ceramic surfaces were characterized with scanning electron microscopy and surface roughness measurement. Hourglasses-shaped ceramic- resin bond specimens were prepared, thermomechanically cycled and stressed to failure under tension. The results showed that for both the factors "laser" and "graphite", statistically significant differences were observed (p < 0.05). Multiple-comparison tests performed on the "laser" factor were in the order: Er:YAG > Nd:YAG (p < 0.05), and on the "graphite" factor were in the order: graphite coating < without coating (p < 0.05). The Dunnett test showed that Er:YAG + HF had significantly higher tensile strength (p = 0.00). Higher surface roughness was achieved after Er:YAG laser treatment. Thus Er:YAG laser treatment produces higher bond strength to resin cement than other surface treatment protocols. Surface-coating with graphite does not improve bonding of the laser-treated lithium disilicate ceramic to resin cement.

Effect of MDP-Based Silane and Different Surface Conditioner Methods on Bonding of Resin Cements to Zirconium Framework

PURPOSE

To determine the shear bond strength (SBS) between zirconium framework and resin cements after different surface conditioner methods and after application of 10-methacryloyloxydecyl dihydrogen phosphate (MDP) based silane and a bonding agent mix.

MATERIALS AND METHODS

128 disc-shaped zirconium-oxide specimens were prepared. Specimens were placed in autopolymerizing acrylic resin. The bonding surface of specimens was smoothed consecutively with 600-, 800-, and 1200-grit silicon carbide papers under water cooling. Eight groups were prepared: CJ, Co-Jet; N, Nd-YAG laser; E, Er-YAG laser; NS, Nd-YAG laser + silane; ES, Er-YAG laser + silane; CJB, Co-Jet + bonding agent; NSB, Nd-YAG laser + silane + bonding agent; ESB, Er-YAG laser + silane + bonding agent. SEM analysis was performed under 2000× magnification. Dual- and self-cured resin cements were bonded to specimens, and shear force was applied. Data were analyzed with one-way ANOVA and Tukey's multiple comparison test (p < 0.05).

RESULTS

The SBS values differed from each other among the groups. While the CJB group showed the highest values, the N group showed the lowest. The treatment with MDP-based silane and bonding agent mix increased SBS values of each cement belonging to each group. SB values of dual-cure resin cement were higher than those of self-cure resin cements.

CONCLUSION

Different surface conditioner methods exhibit an important effect on the SBS of resin cements to zirconium. The application of MDP-based silane and bonding agent mix enhanced SB values.

Evaluation of Different Types of Lasers in Surface Conditioning of Porcelains: A Review Article

To achieve proper bond strength for porcelains, adequate surface roughness is essential, which is traditionally gained by sandblasting or acid etching with hydrofluoric (HF) acid. Nowadays with the development of laser systems, serious efforts were made to apply this new instrument for surface etching of porcelains due to easy usage, safety, and more efficiency. There are different kinds of lasers and porcelains, so choosing the ones which will be good match for each other is crucial. Besides that, changing the irradiation setting can be beneficial as well. This article reviewed 33 related studies and summarized results of etching accomplished by Nd:YAG, Er:YAG, Er,Cr:YSGG and CO2 lasers on different types of porcelains considering different laser settings and evaluation methods to bring a comprehensive insight.

The effect of subpressure on the bond strength of resin to zirconia ceramic

Objective

This study was conducted to investigate the effect of subpressure on the bond strength of resin to zirconia ceramic. The subpressure would create a pressure gradient which could clean out the bubbles in the adhesives or bonding interface.

Methods

Twenty-eight pre-sintered zirconia discs were fabricated. Half of them were polished (group P, n = 14), and the rest were sandblasted (group S, n = 14). After sintered,the surface roughness of the zirconia discs was measured. Then, they were randomly divided into two subgroups (n = 7). The groups were named as follows: PC: P + no additional treatments; PP: P + 0.04 MPa after application of adhesives; SC: S + no additional treatments; and SP: S + 0.04 MPa after application of adhesives. Resin columns were bonded to the zirconia specimens to determine shear bond strength (SBS). The bonding interfaces were observed and the fracture modes were evaluated. Statistical analysis was performed on all data.

Results

The surface roughness of group S was significantly higher than that of group P (P<0.05). The SBS values were PC = 13.48 ± 0.7 MPa, PP = 15.22 ± 0.8 MPa, SC = 17.23 ± 0.7 MPa and SP = 21.68 ± 1.4 MPa. There were significant differences among the groups (P<0.05). Scanning electron microscopy (SEM) results showed that the adhesives of group SP and PP were closer and denser to the zirconia ceramic than that of group PC and SC. The proportion of the mixed fracture mode significantly increased after adding subpressure (P< 0.05).

Conclusion

Subpressure can improve the shear bond strength of resin to zirconia ceramics and increase micro-infiltration between the adhesives and the zirconia ceramics, especially on the rough surfaces.

The effect of Er:YAG laser irradiation on the bond stability of self-etch adhesives at different dentin depths

The aim of this study was to evaluate the effect of Er:YAG laser irradiation on the micro-shear bond strength of self-etch adhesives to the superficial dentin and the deep dentin before and after thermocycling. Superficial dentin and deep dentin surfaces were prepared by flattening of the occlusal surfaces of extracted human third molars. The deep or superficial dentin specimens were randomized into three groups according to the following surface treatments: group I (control group), group II (Er:YAG laser; 1.2 W), and group III (Er:YAG laser; 0.5 W). Clearfil SE Bond or Clearfil S³ Bond was applied to each group’s dentin surfaces. After construction of the composite blocks on the dentin surface, the micro-shear bond testing of each adhesive was performed at 24 h or after 15,000 thermal cycles. The data were analyzed using a univariate analysis of variance and Tukey’s test (p < 0.05). Laser irradiation in superficial dentin did not significantly affect bond strength after thermocycling (p > 0.05). However, deep-dentin specimens irradiated with laser showed significantly higher bond strengths than did control specimens after thermocycling (p < 0.05). Thermocycling led to significant deterioration in the bond strengths of all deep-dentin groups. The stable bond strength after thermocycling was measured for all of the superficial-dentin groups. No significant difference was found between the 0.5 and 1.2 W output power settings. In conclusion, the effect of laser irradiation on the bond strength of self-etch adhesives may be altered by the dentin depth. Regardless of the applied surface treatment, deep dentin showed significant bond degradation.

Surface treatment comparison by application of diamond bur and Er,Cr:YSGG at different powers: morphological and mechanical evaluation

Purpose: This study evaluated the micro-tensile bond strength of new and previous composite resin restorations after surface treatment with diamond bur and Er,Cr:YSGG laser at different power settings (2,3 and 4 W). Materials and methods: Micro-hybride composite resin was inserted in metallic mold 5 ×5 ×15 mm and cured for 40 sec according to manufacturer's instruction.12 blocks were made. The bonded surfaces of the 12 blocks so obtained were subsequently ground using Silicon Carbide papers 1200 grit, for 15 seconds under running water. Then the samples randomly were divided into 4 groups: (G1) Bur-treated, (G2) Er,Cr:YSGG laser with power of 2 W and energy of 100 mJ, (G3) Er,Cr:YSGG laser with power of 3 W and energy of 150 mJ, (G4) Er,Cr:YSGG laser with power of 4 W and energy of 200 mJ. One sample of each group was analyzed by SEM while, after cutting the blocks to 1 mm² of area samples, the others samples were mechanically tested by Universal testing machine with the speed of 0.5 mm per minute till fracture point. Data were analysed using One-Way ANOVA and Tukey Test. Results: T-test showed no significantly differences between G2 and G4(P=0.064) while G3 demonstrated significant differences than G2 (P=0.001) and G4(P=0.000) and also between samples treated with bur (G1) and G2 (P=0.242) ,G3 (P=0.000) ,G4 (P=0.829); G1 didn't significantly differ to G2 and G4(P>0.05), while G1 and G3(P<0.05). Conclusion: On surface treatment of repaired composite, samples treated by laser at 3W power showed better condition of micro-tensile bond strength.

Effect of electrical discharge machining on dental Y-TZP ceramic-resin bonding

PURPOSE

The study determined (i) the effects of electrical discharge machining (EDM) on the shear-bond strength (SBS) of the bond between luting resin and zirconia ceramic and (ii) zirconia ceramic's flexural strength with the three-point bending (TPB) test.

METHODS

Sixty 4.8mm×4.8mm×3.2mm zirconia specimens were fabricated and divided into four groups (n=15): SBG: sandblasted+silane, TSCG: tribochemical silica coated+silane, LTG: Er:YAG laser treated+silane, EDMG: EDM+silane. The specimens were then bonded to a composite block with a dual-cure resin cement and thermal cycled (6000 times) prior to SBS testing. The SBS tests were performed in a universal testing machine. The SBS values were statistically analyzed using ANOVA and Tukey's test. To determine flexural strength, sixty zirconia specimens were prepared and assigned to the same groups (n=15) mentioned earlier. After surface treatment TPB tests were performed in a universal testing machine (ISO 6872). The flexural strength values were statistically analyzed using ANOVA and Tukey's test (α=0.05).

RESULTS

The bond strengths for the four test groups (mean±SD; MPa) were as follows: SBG (Control), 12.73±3.41, TSCG, 14.99±3.14, LTG, 7.93±2.07, EDMG, 17.05±2.71. The bond strength of the EDMG was significantly higher than those of the SBG and LTG (p<0.01). The average flexural strength values for the groups SBG (Control), TSCG, LTG and EDMG were 809.47, 800.47, 679.19 and 695.71MPa, respectively (p>0.05).

CONCLUSIONS

The EDM process improved the SBS. In addition, there was no significant adverse effect of EDM on the flexural strength of zirconia.

Effect of Different Surface Treatments on the Bond Strength of Lithium Disilicate Ceramic to the Zirconia Core

OBJECTIVE

The aim of this study was to evaluate the effect of different surface treatments [sandblasting, Erbium:Yttrium-Aluminium-Garnet (Er:YAG), and femtosecond lasers] on the shear bond strength (SBS) of the CAD-on technique.

BACKGROUND DATA

Although demand for all-ceramic restorations has increased, chipping remains one of the major problems for zirconia-based restorations.

MATERIALS AND METHODS

Forty yttrium-stabilized tetragonal zirconia polycrystalline (Y-TZP) zirconia plates (IPS e.max ZirCAD, Ivoclar Vivadent) were cut, sintered (12.4 × 11.4 × 3 mm) and divided into four groups according to the surface treatments (n = 10): a control group with no surface treatment (Group C), sandblasting with 50 μm Al2O3 (Group S), Er:YAG laser irradiation (Group E), and femtosecond laser irradiation (Group F). Also, 40 cylindrical (5 mm diameter, 2 mm height) lithium disilicate (IPS e.max CAD) veneer ceramics were cut and fused to all zirconia cores by a glass-fusion ceramic and crystallized according to the CAD-on technique. Specimens were subjected to shear force using a universal testing machine. The load was applied at a crosshead speed of 0.5 mm/min until failure. Mean SBS (MPa) were analyzed with one way ANOVA (p < 0.05). The failed specimens were examined under a stereomicroscope at ×20 to classify the mode of failure.

RESULTS

The highest SBS was observed in Group F (36 ± 3.31 MPa), followed by Group S (33.03 ± 5.05 MPa), and Group C (32.52 ± 10.15 MPa). The lowest SBS was observed in Group E (31.02 ± 4.96 MPa), but no significant differences were found between the control and surface treated groups (p = 0.377). All the specimens showed a mixed type of failure.

CONCLUSIONS

Femtosecond laser application increased the bond strength between zirconia-veneer specimens. However, the novel CAD-on technique with no surface treatment also showed high bonding strength. Thus, this technique could prevent ceramic chipping without additional surface treatments.

The Effect of Sandblasting, Er:YAG Laser, and Heat Treatment on the Mechanical Properties of Different Zirconia Cores

OBJECTIVE

The purpose of this study was to evaluate the effect of surface and heat treatments on the mechanical properties and phase transformation of yttria-stabilized tetragonal zirconia (Y-TZP) materials.

BACKGROUND DATA

Zirconia is exposed to several treatments during dental application process. Knowing the effect of applied treatments on zirconia is essential for clinical success.

MATERIAL AND METHODS

Forty disk specimens of Zirkonzahn (Z) and DC-Zirkon (DC) materials were fabricated. The specimens were randomly divided into four groups according to surface [control, sandblasting, Erbium: Yttrium Aluminum Garnet (Er:YAG) laser irradiation] and heat (firing) treatments. The surface roughness (Ra, μm) was measured using a surface profilometer. The relative amount of the transformed monoclinic (m) phase was analyzed by X-ray diffractometry (XRD). Biaxial flexural strength was tested using piston-on-three-ball technique. The data were analyzed with the Kruskal-Wallis H test with Bonferroni correction, and the Mann-Whitney U test was used for pairwise comparisons.

RESULTS

There were no significant differences in surface roughness among the treated groups (p > 0.05), whereas sandblasting showed higher surface roughness than other treatments for both materials. Scanning electron microscopic (SEM) analyses revealed changes in surface morphology after surface treatments, especially in laser groups with the formation of cracks, and in sandblasting groups with the formation of microretentive grooves. The greatest amount of the monoclinic phase was measured after sandblasting (8.13%) for Z and (19.8%) for DC. The monoclinic phase reverted to the tetragonal phase after heat treatment. Heat treatment groups showed significantly lower flexural strength than other treatments (p < 0.05).

CONCLUSIONS

Heat and surface treatments influenced the mechanical properties of zirconia ceramic. The biaxial flexural strength and crystalline phase of materials decreased after heat treatments.

Veneer Ceramic to Y-TZP Bonding: Comparison of Different Surface Treatments

PURPOSE

The purpose of this study was to evaluate the effects of various surface-treatment techniques for enhancing the bond strength between veneering ceramic and yttria-stabilized tetragonal zirconia polycrystals (Y-TZP).

MATERIALS AND METHODS

Pre-sintered Y-TZP specimens were divided into eight groups (n = 10) according to the surface-treatment technique used: (a) untreated (control); (b) air abrasion with aluminum oxide particles; (c) erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation at different energy intensities (1 to 6 W). All specimens were then sintered and veneered with veneering ceramic according to the manufacturer's instructions. The obtained zirconia-ceramic specimens were immersed in 37°C distilled water for 24 hours before a shear bond strength test using a universal testing device at a 1 mm/min crosshead speed. The average values were calculated. After debonding, the Y-TZP surfaces were examined under a stereomicroscope to determine their fracture pattern, and the surface topography was evaluated with scanning electron microscopy after surface treatments.

RESULTS

The bond strength ranged from 13.24 to 20.54 MPa. All surface treatments increased the bond strength between the veneering ceramic and Y-TZP; however, the value for the 6 W irradiation group was significantly different from the values for other groups (p ˂ 0.05).

CONCLUSIONS

The present study's findings showed that higher energy densities were needed for the laser irradiation to improve the bond strength between the veneering ceramic and zirconia.

CLINICAL IMPLICATION

Y-TZP is commonly used as a core material in fixed restorations. The bond strength between zirconia and the veneering ceramic can be affected by various surface treatments.

Evaluation of roughness, wettability, and morphology of an yttria-stabilized tetragonal zirconia polycrystal ceramic after different airborne-particle abrasion protocols

STATEMENT OF PROBLEM

Airborne-particle abrasion is an effective method of roughening a zirconia surface and promoting micromechanical interlocks with luting cements. However, the effect of different airborne-particle abrasion protocols on the micromechanical retention mechanism has been poorly investigated.

PURPOSE

The purpose of the study was to evaluate the effect of airborne-particle abrasion protocols on the surface roughness, wettability, and morphology of an yttria-stabilized tetragonal zirconia polycrystal ceramic.

MATERIAL AND METHODS

A total of 140 zirconia specimens (14 × 14 × 1.4 mm) were made from Lava and divided into 7 groups. Their surfaces were treated as follows (n = 20): as-sintered (control); airborne-particle abraded with 50-μm Al2O3 particles; 120-μm Al2O3 particles; 250-μm Al2O3 particles; 30-μm silica-coated Al2O3 particles (Rocatec Soft); 110-μm silica-coated Al2O3 particles (Rocatec Plus); and 120-μm Al2O3 particles followed by Rocatec Plus. The surface roughness (Ra) and wettability analyses were performed on the same specimens of each group. The test liquid used for the wettability analysis was the silane RelyX Ceramic Primer. Two additional specimens (6.0 × 6.0 × 1.0 mm) per group were prepared to evaluate the surface morphology with scanning electron microscopy. The roughness (Ra) data were analyzed by 1-way ANOVA and the Dunnett C test (α = .05), and the wettability data with 1-way ANOVA (α = .05). The Spearman correlation analysis was applied to test for a possible correlation between roughness and wettability.

RESULTS

The control group (0.35 μm) exhibited the lowest mean roughness value (Ra), which was followed by Rocatec Soft (0.40 μm), 50-μm Al2O3 particles (0.52 μm), Rocatec Plus (0.69 μm), 120-μm Al2O3 particles (0.80 μm)/120-μm Al2O3 particles + Rocatec Plus (0.79 μm), and 250-μm Al2O3 particles (1.13 μm). No significant difference was found among the groups concerning wettability. No correlation (rs = -0.09; P = .27) was found between the 2 dependent variables. The scanning electron microscopy analysis indicated that the different airborne-particle abrasion protocols produced differences in the morphologic patterns.

CONCLUSIONS

Although roughness and morphology of the zirconia surface varied according to the airborne-particle abrasion protocol, no close relationship was found between them. The roughness increase seemed to have followed the size of the particles.

Bond strength of resin cement to CO2 and Er:YAG laser-treated zirconia ceramic

Objectives

It is difficult to achieve adhesion between resin cement and zirconia ceramics using routine surface preparation methods. The aim of this study was to evaluate the effects of CO₂ and Er:YAG laser treatment on the bond strength of resin cement to zirconia ceramics.

Materials and Methods

In this in-vitro study 45 zirconia disks (6 mm in diameter and 2 mm in thickness) were assigned to 3 groups (n = 15). In control group (CNT) no laser treatment was used. In groups COL and EYL, CO₂ and Er:YAG lasers were used for pretreatment of zirconia surface, respectively. Composite resin disks were cemented on zirconia disk using dual-curing resin cement. Shear bond strength tests were performed at a crosshead speed of 0.5 mm/min after 24 hr distilled water storage. Data were analyzed by one-way ANOVA and post hoc Tukey's HSD tests.

Results

The means and standard deviations of shear bond strength values in the EYL, COL and CNT groups were 8.65 ± 1.75, 12.12 ± 3.02, and 5.97 ± 1.14 MPa, respectively. Data showed that application of CO₂ and Er:YAG lasers resulted in a significant higher shear bond strength of resin cement to zirconia ceramics (p < 0.0001). The highest bond strength was recorded in the COL group (p < 0.0001). In the CNT group all the failures were adhesive. However, in the laser groups, 80% of the failures were of the adhesive type.

Conclusions

Pretreatment of zirconia ceramic via CO₂ and Er:YAG laser improves the bond strength of resin cement to zirconia ceramic, with higher bond strength values in the CO₂ laser treated samples.