Surface treatment with a fractional CO2 laser enhances shear bond strength of resin cement to zirconia

Evaluation of bond strength of glass and resin-ceramics with laser phototherapy: A systematic review and meta-analysis of in vitro studies

STATEMENT OF PROBLEM

Laser phototherapy has been studied as a surface treatment capable of increasing the adhesion of cement to the ceramic surface. However, the bond strength of glass and resin-ceramics after laser phototherapy is unclear.

PURPOSE

The objective of this systematic review and meta-analysis was to compare the bond strength of glass and resin-ceramics using laser therapy and conventional hydrofluoric acid etching.

MATERIAL AND METHODS

This systematic review and meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and was registered in the Open Science Framework (OSF) for in vitro studies. A population, intervention, control, and outcome (PICO) question was formulated: "Does phototherapy promote better bond strength in glass and resin-ceramics than conventional hydrofluoric acid etching?" A literature search was performed in PubMed/MEDLINE, Embase, Web of Science, Scopus, Cochrane Library, and ProQuest databases up to January 2023. The Joanna Briggs Institute critical assessment guidelines for quasi-experimental studies were used for quality assessment. The meta-analysis was based on the inverse variance (IV) method (α=.05).

RESULTS

A total of 6 in vitro studies published between 2007 and 2019 with a total number of 348 specimens were included for qualitative analysis; 1 study had a positive effect. Five of the studies were included in the meta-analysis, which indicated a significant decrease for feldspathic ceramics that received laser phototherapy and lithium disilicate (P=.002; MD: -2.15; 95% CI: -3.53 to -0.77; I2=89%, P<.01) and (P<.01; MD: -2.13; 95% CI: -2.99 to -1.27; I2=82%, P<.01), respectively.

CONCLUSIONS

Laser irradiation as surface etching of glass ceramics does not produce a bond strength equal to that of conventional hydrofluoric acid etching.

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.

In vitro comparative study between adhesion forces obtained on zirconia ceramic micromechanically treated with femtosecond laser (1027 nm), carbon dioxide laser (10,600 nm), and aluminum-oxide particles

Conventional surface roughening treatments used for silica-based ceramics in order to improve subsequent adhesion become unreliable for zirconia ceramics. Laser conditioning can be a good alternative. The purpose of this in vitro study was to compare conventional (macro) shear bond strength (SBS) values obtained between resin composite and zirconium oxide ceramic samples grouped according to different micromechanical treatments received, and examine differences in surface roughness. One-hundred and fifty disks of sintered zirconia were randomly divided into 5 groups and roughened as follows: (1) Group NOT, no surface treatment; (2) Group APA, abraded with 50-μm aluminum-oxide (Al2O3) particles; (3) Group TBS, abraded with 30-μm aluminum-oxide particles covered with silica; (4) Group CO2, irradiated with a CO2 laser which emitted in continuous wave mode at 3 W of power; and (5) Group FEM, irradiated with a pulsed femtosecond laser, with an incident energy of 10 μJ, a frequency of 1000 Hz, and a fluence of 1.3 kJ/cm2. All surfaces were treated with a MDP-containing adhesive/silane coupling agent mixture upon which were prepared and light polymerized composite resin cylinders. Shear bond strength was measured and samples were observed by scanning electron microscopy (SEM). Statistically significant differences (p < 0.05) were found among all groups, except between CO2 and FEM, which showed the highest adhesion values (15.12 ± 2.35 MPa and 16.03 ± 2.73 MPa). SEM revealed differences in surface patterns. CO2 laser irradiation can be an alternative to sandblasting, although it could also weaken the ceramic. Suitable surface patterns on zirconia ceramics can be obtained with ultrashort pulsed radiation emitted by a pulsed femtosecond laser.

Influence of nonthermal argon plasma on the micro-shear bond strength between resin cement and translucent zirconia

Background

Considering the potential of translucent zirconia for application in esthetic restorations, it is necessary to find effective methods with the least adverse effects to increase its bond strength to resin cement.

Aims

This study aimed to test if different conservative surface treatments and cement types could affect the micro-shear bond strength (μSBS), failure mode, and bonding interface between resin cement and translucent zirconia.

Materials and Methods

In this in vitro experimental study, translucent zirconia blocks were divided into four groups based on the surface treatment they received: no treatment, argon plasma, primer (Pr), and Pr + plasma. Each group was further divided into two subgroups based on the applied cement: PANAVIA F2 and Duo-Link cement. Fourteen cement columns with a diameter of 1 mm were placed on each block (n = 14); all the specimens were immersed in 37°C water for 24 h. Afterward, μSBS was evaluated (P < 0.05), and the mode of failure was determined by a stereomicroscope (×10). The cement-zirconia interface and the surface hydrophilicity (contact angle) were also evaluated.

Statistical Analysis

Two-way analysis of variance (ANOVA) was used to evaluate the effect of surface preparation, cement types, and incubator, simultaneously (P < 0.05). The bond strengths after incubation were analyzed by one-way ANOVA (P < 0.05). Failure mode, contact angle, and cement-zirconia interface were analyzed descriptively.

Results

The highest bond strength was seen in Pr surface treatment for Duo-Link cement; however, this group was not significantly different from Pr and PANAVIA F2 cement and Pr + plasma and Duo-Link cement (P = 0.075) groups. All plasma specimens in the incubator failed prematurely. The mode of failure in all specimens was adhesive. The lowest and highest contact angles were seen in Pr + plasma and the control groups, respectively.

Conclusion

The use of Pr could successfully improve the bond strength of resin cement to translucent zirconia while plasma was not an acceptable and durable substitute.

Surface modification of zirconia or lithium disilicate-reinforced glass ceramic by laser texturing to increase the adhesion of prosthetic surfaces to resin cements: an integrative review

OBJECTIVE

The purpose of this study was to perform an integrative review on laser texturing the inner surface of lithium disilicate-reinforced glass ceramic or zirconia to increase their bond strength to resin-matrix cements.

MATERIALS AND METHOD

A bibliographic review was performed on PubMed using the following search terms: "zirconia" OR "lithium disilicate" AND "laser" AND "surface" OR "roughness" AND "bond strength" AND "luting agent" OR "resin cement." Studies published in English language until March 15, 2023, were selected regarding the purpose of this study.

RESULTS

A total of fifty-six studies were identified althoug thirteen studies were selected. The findings revealed that zirconia surfaces were significantly modified after laser irradiation resulting in macro-scale aligned retentive regions with depth values ranging from 50 to 120 µm. Average roughness values of laser-textured zirconia by Er,Cr:YSGG laser (~ 0.83 µm) were quite similar when compared to grit-blasted zirconia surfaces (~ 0.9 µm) although roughness increased up to 2.4 µm depending on the laser type and parameters. Lithium disilicate-reinforced glass ceramics textured with Er:YAG revealed an average roughness of around 3.5 µm while surfaces textured using Nd:YAG laser revealed an average roughness of 2.69 µm; that was quite similar to the roughness values recorded for etched surfaces (2.64 µm). The shear bond strength (SBS) values of zirconia surfaces textured on Nd:YVO₄ laser irradiation were slightly higher (~ 33.5 MPa) than those recorded for grit-blasted zirconia surfaces (28 MPa). Laser-textured zirconia surfaces on CO₂ laser revealed higher SBS values (18.1 ±0.8 MPa) than those (9.1 ± 0.56 MPa) recorded for untreated zirconia surfaces. On lithium disilicate-reinforced glass ceramics, higher SBS values to resin-matrix cements were recorded for specimens textured with a combination of fractional CO₂ laser irradiation and HF acid etching (~ 22-24 MPa) when compared with grit-blasted specimens (12.2 MPa). Another study revealed SBS values at around 27.5 MPa for Er:YAG-textured lithium disilicate-reinforced glass ceramics to resin-matrix cements.

CONCLUSIONS

The laser irradiation at high power increases the roughness of the inner surface of lithium disilicate-reinforced glass ceramic or zirconia leading to an enhanced bond strength to resin-matrix cements. Thus, the laser type and irradiation parameters can be adjusted to enhance the macro- and micro-scale retention of zirconia and glass ceramic surfaces to resin-matrix cements.

CLINICAL RELEVANCE

Alternative methods for surface modification of lithium disilicate-reinforced glass ceramic and zirconia surfaces have been assessed to provide proper morphological aspects for enhanced adhesion to resin-matrix cements. An increase in the bond strength of glass ceramics or zirconia to resin-matrix cements can improve the long-term performance of cemented prosthetic structures in the oral cavity.

Comparison of the Effectiveness of CO2 and Diode Lasers for Gingival Melanin Depigmentation: A Randomized Clinical Trial

Introduction: Gingival hyperpigmentation is an esthetic concern for some individuals. This study compared the effectiveness of CO2 and diode lasers for gingival depigmentation. Methods: This randomized, split-mouth, clinical trial consisted of 12 patients with the chief complaint of hyperpigmented gingival areas. The upper right and left anterior segments and the mandibular anterior segment were randomly allocated to one of the treatment groups. The segments in group 1 underwent gingival depigmentation with a diode laser (810 nm) at 6 W and pulsed mode, whereas group 2 was ablated with a diode laser at 3 W and continuous mode. The removal of gingival pigments in group 3 was contemplated with a CO2 laser (10600 nm, 3 W, continuous mode). The operation chair time, bleeding during the procedure and post-operative pain were recorded. The gingival color and esthetic appearance were measured before the operation and at 1 week and 6 months later. Results: There was no significant difference in the bleeding scores, pain level, and color alteration values between the groups (P>0.05). The operation chair time was significantly shorter when the diode laser was applied at pulsed mode (P<0.05). The segments treated with the diode laser (pulsed or continuous mode) showed a higher esthetic appearance at the 6-month follow-up compared to those ablated with the CO2 laser (P<0.05). Conclusions: Higher esthetic appearance is expected when using the diode laser for gingival depigmentation compared to the CO2 laser. The application of the diode laser at pulsed mode could be recommended for gingival depigmentation, as it produced pleasing esthetic outcomes at reduced chair time.

The effect of adhesive surface with porcelain sintering and two silane coupling agents on the adhesive properties of zirconia

Background

To explore the effect of adhesive surface with porcelain sintering and different silane coupling agents on adhesive properties of zirconia ceramics.

Methods

Zirconia blocks (n=72) were randomly divided into two large groups (n=36) according to whether the adhesive surface was treated with sintered porcelain: N (no porcelain sintering), P (porcelain sintering). Then, according to different silane coupling agents, each group was randomly divided into three small groups, six small groups in total (n=12): NN (no porcelain sintering and agent), NM (no porcelain sintering + Monobond-S), NC (no porcelain sintering + Clearfil Repair); PN (porcelain sintering + no agent), PM (porcelain sintering + Monobond-S), PC (porcelain sintering + Clearfil Repair). After surface treatment, RelyX Unicem Cement was used to make ceramic-resin bonding specimens. Then, each of the six small groups was randomly divided into two subgroups; shear bond strength (SBS) was tested and bond failure mode was analyzed before and after thermal cycling 5,000 times.

Results

(I) SBS analysis: the SBS values of the P groups were significantly higher than those of the N groups (P<0.05). The groups treated with silane coupling agents showed higher SBS values than the control group (P<0.05), and the PC groups showed the highest SBS values (P<0.05). The SBS of each group was significantly decreased after thermal cycling (P<0.05). (II) The microcharacteristics under scanning electron microscopy and energy spectrum analysis: the ceramic blocks being treated by porcelain sintering showed more roughness than the control group. A large amount of silicon (Si) appeared on the surface of the ceramic blocks after porcelain sintering.

Conclusions

(I) Treating the adhesive surface by porcelain sintering can improve the bonding strength between zirconia and RelyX Unicem Cement, and the effect was better in conjunction with silane coupling agent. (II) The two kinds of silane coupling agent (Monobond-S, Clearfil Repair) can improve the bonding strength between zirconia and resin cement. The effect of Clearfil Repair is better than that of Monobond-S. (III) Thermal cycling had a significant adverse effect on SBS between zirconia and RelyX Unicem Cement. Clearfil Repair is helpful in improving the durability of zirconia bonding strength.

Effect of laser irradiation on bond strength between zirconia and resin cement or veneer ceramic: A systematic review and meta-analysis

Aim:

This systematic review with meta-analysis aimed to evaluate the effect of the laser treatment on bond strength between Y-TZP and the resin cement or with the veneering ceramic, and the effect on the alteration of the Y-TZP surface roughness.

Settings and Design:

Systematic review and meta analysis following PROSPERO guidelines.

Materials and Methods:

A comprehensive review was performed up to September 2020 on four databases (PubMed/MEDLINE, Embase, Scopus, and Cochrane Library), using the combination of keywords: “laser AND zirconia AND surface treatment AND bond strength”.

Statistical Analysis Used:

The meta-analysis was based on the Mantel–Haenszel and inverse variance methods. The continuous outcome was evaluated by mean difference and the corresponding 95% confidence intervals.

Results:

A total of 37 studies were identified for the inclusion of data, with only in vitro studies. The types of laser reported in the studies were: Er:YAG, Nd:YAG, Er,Cr:YSGG, CO2, Femtosecond, and Yb lasers. A random-effect model found statistically significant differences between lasers and control groups of Y-TZP (P < 0.00001; MD: 3.08; 95% CI: 2.58 to 3.58). Only the bond strength with the Er:YAG laser did not present statistical difference (P = 0.51; MD: 0.22; 95% CI: −0.44–0.88). In another analysis, a random-effect model found a statistically significant difference between the laser and control groups on surface roughness (P < 0.00001; MD: 0.96; 95% CI: 0.86 to 1.06).

Conclusions:

Laser irradiation is capable to improve the Y-TZP surface roughness and the bond strength of zirconia with resin cement and veneering ceramics. However, there is a lack of laser protocol for the zirconia surface, a fact that makes a simple and direct comparison difficult.

Effect of different laser treatments on the shear bond strength of zirconia ceramic to resin cement

BACKGROUND

Several techniques such as sand blast, silicoating, and laser irradiation have been introduced for reliable bond between zirconia and resin cement. This study aimed to assess and compare the effect of three types of lasers on the shear bond strength (SBS) of zirconia to resin cement.

MATERIALS AND METHODS

In this in vitro study, 55 zirconia disks (6 mm diameter × 3 mm thickness) were randomly divided into five groups: control (1), sandblast (2), carbon dioxide (CO₂) (3), erbium-doped yttrium aluminum garnet (Er: YAG) (4), and neodymium-doped yttrium aluminum garnet (Nd: YAG) (5) laser irradiation. The surface morphology of one specimen from each group was evaluated by a scanning electron microscope. Zirconia disks were cemented to composite using Panavia F2. SBS test was performed at a crosshead speed of 1 mm/min after 24 h storage in distilled water and thermocycling. The data were analyzed by one-way analysis of variance and post hoc Tukey's HSD tests (α = 0.05).

RESULTS

The mean SBS values of the groups such as sandblast, Er: YAG, Nd: YAG, and CO₂ lasers and control were 6.64 MPa, 6.63 MPa, 4.98 MPa, 4.39 MPa, and 2.32 MPa, respectively. No significant difference was observed between sandblast and Er: YAG laser and between Nd: YAG and CO₂ lasers.

CONCLUSION

All lasers increased SBS values of zirconia to resin cement in comparison to the untreated surface. Er: YAG laser was the most effective laser treatment on the bond strength equal to that of sandblast.

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.

Evaluation of Efficacy of Various Surface Conditioning Methods on the Repair Bond Strength of Composite to Different Fracture Types of Zirconia Ceramics

The aim of this study was to investigate the effects of different surface treatment methods on shear bond strength between composite resin and different levels of zirconia ceramic. Laser surface-conditioning procedures have been reported as effective method to increase repair bond strength of composite to zirconia ceramics. Detailed information of effects of Er,Cr:YSGG laser treatment with different pulse rates on the zirconia ceramics is lacking in the literature. 120 disc-shaped specimens were prepared including zirconia, veneering ceramic, and 50% veneering ceramic-50% zirconia surfaces. Four different surface treatments were applied to the specimens. These were grinding with diamond bur, sandblasting, and short and long pulse rates of Er,Cr:YSGG laser irradiation. An intraoral ceramic repair kit was used to repair specimens, and shear bond strength was performed on the composite resin to each specimen. The highest mean bond strength was seen in the veneering ceramic surface that was ground using a diamond bur, and the lowest mean bond strength value was observed in the same surface that was treated with long pulse laser irradiation. The sandblasting with alumina particles exhibited lower mean repairing bond strength among the rest of used methods in this study for the group which contained half of the veneering ceramic and half of the zirconia. Sandblasting and Er,Cr:YSGG laser using surface treatment procedures obtained appropriate bond strength for the group that included 50% veneering ceramic-50% zirconia, because of no significant differences observed among the applied surface conditioning methods in this group.

Effect of Nd:YAG, Er,Cr:YSGG Laser Irradiation, and Adjunctive Photodynamic Therapy on Push-Out Bond Strength of Zirconia Posts to Radicular Dentin

This study is aimed at assessing the influence of Nd:YAG, Er,Cr:YSGG laser irradiation, and adjunctive photodynamic therapy (aPDT) on the bond strength of zirconia posts to radicular dentin. Eighty extracted anterior teeth were randomly categorized into 4 groups (n = 20) based on varying laser irradiation treatments, i.e., conventional cleaning and shaping (CCS), Nd:YAG, Er,Cr:YSGG, and aPDT group, respectively. Using a cutting machine, the samples were prepared for push-out bond strength analysis; 4 sections (2 on each apical and cervical) of around 1 mm thickness were sectioned for all roots at a right angle to the long axis of the post. After making the space for the post, they were incorporated into the root system and were subjected to different laser treatments. The universal testing machine was utilized to assess the push-out bond strength, which had a defined 1 mm/minute crosshead speed until the failure was encountered. Specimens in the aPDT group (8.20 ± 2.14 MPa) demonstrated the highest mean push-out bond strength, whereas the lowest was shown by samples in the CCS group (7.08 ± 1.11 MPa). According to the independent t-test, the mean push-out bond strength scores of the cervical segments were higher as compared to the apical segments in research groups (p < 0.05). Overall, the adhesive type was the most frequently encountered failure mode in all of the experimental groups, with the least number of failures observed in aPDT treated teeth samples. In conclusion, the push-out bond strength to radicular dentin was not much influenced by Nd:YAG, Er,Cr:YSGG laser, and aPDT in comparison with CCS. Although statistically not significant, however, the application of aPDT provided better outcomes as compared to other research groups.

Debonding of Leucite-reinforced Glass-ceramic Veneers Using Er, Cr:YSGG Laser Device: Optimizing Speed with Thermal Safety

CLINICAL RELEVANCE

Removing laminate veneers on anterior teeth by using an Er,Cr:YSGG dental laser can be completed faster than previously reported while maintaining thermal safety.

SUMMARY

Laser surface texturing of zirconia-based ceramics for dental applications: A review

Laser surface texturing is widely explored for modifying the surface topography of various materials and thereby tuning their optical, tribological, biological, and other surface properties. In dentistry, improved osseointegration has been observed with laser textured titanium dental implants in clinical trials. Due to several limitations of titanium materials, dental implants made of zirconia-based ceramics are now considered as one of the best alternatives. Laser surface texturing of zirconia dental implants is therefore attracting increasing attention. However, due to the brittle nature of zirconia, as well as the metastable tetragonal ZrO₂ phase, laser texturing in the case of zirconia is more challenging than in the case of titanium. Understanding these challenges requires different fields of expertise, including laser engineering, materials science, and dentistry. Even though much progress was made within each field of expertise, a comprehensive analysis of all the related factors is still missing. This review paper provides thus an overview of the common challenges and current status on the use of lasers for surface texturing of zirconia-based ceramics for dental applications, including texturing of zirconia implants for improving osseointegration, texturing of zirconia abutments for reducing peri-implant inflammation, and texturing of zirconia restorations for improving restoration retention by bonding.

Influence of Er,Cr:YSGG Laser Irradiation on the Push-Out Bond Strength of Zirconia and Glass Fiber Posts with Radicular Dentin

Objective

This in vitro study was designed to evaluate the influence of an Er,Cr:YSGG laser on the bond strength of zirconia and glass fiber posts with root dentin.

Materials and methods

Ninety extracted single-rooted human teeth were randomized into 6 groups (n = 15/group) on the basis of different posts (zirconia/glass fiber) and Er,Cr:YSGG laser tips (axial and radial). Specimens were prepared for push-out testing with the help of a cutting machine; six slices (2 on each cervical, middle, and apical) of approximately 1 mm thickness were sectioned for all roots on a plane perpendicular to the long axis of the post. All specimens were placed into a universal testing machine with a defined 0.5 mm/min crosshead speed until the maximum failure load was obtained.

Results

The highest mean push-out bond strength of the glass fiber and zirconia groups was achieved with laser treatment. The highest push-out bond strength was achieved with the axial fiber tip (7.63 ± 1.22 MPa), and the lowest was achieved with a radial fiber tip of the glass fiber group (6.98 ± 0.96 MPa). ANOVA showed a statistically significant difference between the groups (p = 0.041). The mean push-out bond strength was found to be higher with an axial fiber tip for both cervical and apical segments in the glass fiber and zirconia groups (p < 0.05). The independent t-test resulted in the overall highest mean push-out bond strength in the apical segments (p = 0.026).

Conclusion

Within the limits of the present in vitro research study, an enhancement in the push-out bond strength of resin cement, mainly in the cervical region of the root canal, was achieved after irradiation with an Er,Cr:YSGG laser using an axial fiber tip.

Effect of airborne particle abrasion and sintering order on the surface roughness and shear bond strength between Y-TZP ceramic and resin cement

This study examined the surface roughness (R_a) and shear bond strength (SBS) of Yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic after airborne particle abrasion at different pressures and particle sizes, pre- and post-sintering. Ninety specimens, prepared from Y-TZP ceramic blocks (Vita In-Ceram YZ, Vita Zahnfabrik), were divided into nine subgroups: control, and 50 and 110 µm Al₂O₃ airborne particle abrasion at 3 and 4 bar pressure, before and after sintering, respectively. According to the sintering order, before and after surface treatments, R_a values were measured using a profilometer. SBS to Y-TZP was assessed after thermocycling, using self-adhesive resin cement (Rely X U200, 3M ESPE). Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) were performed on one specimen per group. All surface-treated samples were rougher than the controls. ABS50-4 (50 µm Al₂O₃ airborne particle abrasion at 4 bar pressure before sintering), ABS110-3, and ABS110-4 showed the highest R_a values, among all cohorts. The controls displayed lower SBS values than the treated groups (p<0.05), which had statistically similar results to each other. Airborne particle abrasion of pre-sintered Y-TZP, followed by sintering, increased the tetragonal structure contents.

The Effect of Fractional CO2 Laser Irradiation on Shear Bond Strength of Resin Cement to Feldspathic Porcelain

Introduction: This study investigated the effect of fractional CO2 laser on shear bond strength (SBS) of resin cement to feldspathic porcelain. Methods: Sixty blocks of unglazed feldspathic porcelain were randomly divided into 5 groups of 12 by treatment. Group 1 and 2 underwent etching with 9.6% hydrofluoric acid (HF) and air abrasion with alumina particles, respectively. In groups 3 and 4, a fractional CO2 laser was applied for 10 seconds using 20 W/10 mJ (group 3) or 15 W/20 mJ (group 4). The specimens in group 5 were first treated by fractional CO2 laser (15 W/20 mJ) and then etched by HF acid. After silane application, a resin cement (Clearfil SA) was poured into plastic molds over the porcelain surface and light cured. SBS was assessed by a universal testing machine and the type of bond failure was determined. Results: Analysis of variance (ANOVA) indicated a significant difference in SBS among the study groups (P<0.001). Pairwise comparison demonstrated that the application of fractional CO2 laser followed by HF acid yielded SBS that was significantly greater than that of the other groups (P<0.05). The SBS of both laser groups (groups 3 and 4) were comparable to each other and significantly lower than the other groups (P<0.05). No significant difference was found in the distribution of failure modes among the groups (P=0.522) Conclusion: The application of fractional CO2 laser followed by HF acid treatment can improve SBS of resin cement to feldspathic porcelain and could be recommended when demanding extra retention.

In vitro shear bond strength between fluorinated zirconia ceramic and resin cements

PURPOSE

The purpose of this study was to evaluate the efficiency of a gas-phase fluorination method under different fluorination periods through using two resin cements.

MATERIALS AND METHODS

84 zirconia specimens in dimensions of 5 mm × 5 mm × 2 mm were prepared and surface treated with 50 µm aluminum oxide particles or gas phase fluorination for 2 min, 5 min, or 10 min. One specimen in each group was surface analyzed under scanning electron microscope. The remaining specimens were bonded to composite cylinders in dimensions of 2 mm diameter and 3 mm high with Panavia SA Plus or Variolink N. Then, the specimens were stored in 37℃ distilled water for 24 hours and shear bond strength test was applied at a speed of 1 mm/min.

RESULTS

The highest shear bond strength values were observed in the samples fluorinated for 5 minutes and cemented with Panavia SA Plus. Variolink N did not elicit any statistical differences between surface treatments. Panavia SA Plus resin cement and Variolink N resin cements featured statistically significant difference in shear bond strength values only in the case of 5 minutes of fluorination treatment.

CONCLUSION

According to the results of this study, application of 5 minutes of fluorination with 10-methacryloyloxydecyl dihydrogen phosphate monomer (MDP) containing Panavia SA Plus resin cement increased the resin bond strength of zirconia. Fluorination of the zirconia surface using conventional resin cement, Variolink N, did not lead to an increase in bond strength.

CO2 laser dentin surface treatment most effectively increased ceramic shear bond strength

BACKGROUND AND AIMS

The purpose of this study is to determine the effect of CO2 laser irradiation in comparison with sandblasting (Sb), hydrofluoric acid (Hf) and silane coupling agent (Si) on shear bond strength (SBS) of resin cement to CAD/CAM ceramics bonded to dentin.

MATERIAL AND METHODS

Forty-eight (CAD/CAM) ceramic discs were prepared and grouped by material, i.e. lithium disilicate (Emax CAD) and zirconia ceramic (Emax ZirCAD), distributed into four different groups: group A, lithium disilicate (Li) CO2/HF/Si; group B, Li: HF/Si; group C, zirconia (Zr) CO2/Sb/Si; group D, Zr: Sb/Si.

RESULTS

It was shown significant difference between irradiated and non-irradiated groups in terms of shear bond strength for zirconia ceramics (p value = 0.039).

CONCLUSION

CO2 laser irradiation increases shear bond strength for both CAD/CAM ceramics bonded to dentin.

The effects of lasers on bond strength to ceramic materials: A systematic review and meta-analysis

Lasers have recently been introduced as an alternative means of conditioning dental ceramic surfaces in order to enhance their adhesive strength to cements and other materials. The present systematic review and meta-analysis aimed to review and quantitatively analyze the available literature in order to determine which bond protocols and laser types are the most effective.

A search was conducted in the Pubmed, Embase and Scopus databases for papers published up to April 2017. PRISMA guidelines for systematic review and meta-analysis were followed.

Fifty-two papers were eligible for inclusion in the review. Twenty-five studies were synthesized quantitatively. Lasers were found to increase bond strength of ceramic surfaces to resin cements and composites when compared with control specimens (p-value < 0.01), whereas no significant differences were found in comparison with air-particle abraded surfaces.

High variability can be observed in adhesion values between different analyses, pointing to a need to standardize study protocols and to determine the optimal parameters for each laser type.

The effect of surface treatment with a fractional carbon dioxide laser on shear bond strength of resin cement to a lithium disilicate-based ceramic

BACKGROUND

This study investigated the impact of different surface treatments, including fractional carbon dioxide (CO₂) laser on shear bond strength (SBS) of resin cement to lithium disilicate ceramic.

MATERIALS AND METHODS

In this in vitro study, 72 blocks of IPS e.max CAD ceramic were randomly divided into six groups in terms of treatment (n = 12). Group 1 underwent etching with 9.6% hydrofluoric (HF) acid, whereas group 2 was subjected to air abrasion with aluminum oxide particles. Groups 3 and 4 were treated with a fractional CO₂ laser for 10 s using 10 W/14 mJ (group 3) or 20 W/10 mJ (group 4). In groups 5 and 6, the CO₂ laser was applied similar to that in groups 3 and 4, respectively; then, the specimens were etched by HF acid. After silane application, luting cement was bonded to the specimens. The SBS was assessed with a universal testing machine, and the type of bond failure was determined. Data were analyzed by ANOVA, Duncan, and Fisher's exact tests.

RESULTS

Surface conditioning with fractional CO₂ laser alone resulted in significantly lower SBS than HF acid treatment (P < 0.05). Bond strengths of the specimens treated with a combination of laser irradiation and acid etching were significantly greater than all the other groups (P < 0.05). No significant difference was found in the distribution of failure modes among the groups (P = 0.337).

CONCLUSION

The combination of fractional CO₂ laser irradiation and HF acid etching could be recommended when extra retention is required for lithium disilicate-based restorations, whereas laser treatment alone cannot produce sufficient SBS.