Effect of Different Nd:YAG Laser Power Outputs on Bond Strength of Resin Cement to Zirconia in Comparison to Sandblasting

Effects of Nd: YAG LASER irradiation and O2 plasma on the adhesive performance of poly-ether-ether-ketone (PEEK)

PURPOSE

To evaluate the effects of neodymium-doped yttrium aluminum garnet (Nd: YAG) LASER irradiation and oxygen (O2) plasma on the adhesive performance of polyether ether ketone (PEEK) and resin adhesive.

METHODS

Nd: YAG LASERs of varying powers and O2 plasma for different durations were used to modify PEEK. A total of 168 PEEK specimens were randomly divided into seven groups (n = 24/group): (A) Control group: untreated PEEK, (B) L0.75 group: PEEK modified with 0.75 W Nd: YAG LASER, (C) L1 group: PEEK modified with 1.0 W Nd: YAG LASER, (D) L1.25 group: PEEK modified with 1.25 W Nd: YAG LASER, (E) P15 group: PEEK modified with 15 min of O2 plasma, (F) P25 group: PEEK modified with 25 min of O2 plasma, and (G) P35 group: PEEK modified with 35 min of O2 plasma. The surface characteristics of the materials were comprehensively analyzed using a scanning electron microscope (SEM), profilometer, energy-dispersive spectrometer (EDS), and contact angle tester. The adhesive specimens were bonded with Variolink N resin adhesive in all groups and each group was further divided into two subgroups (n = 12/group): (a) water storage for 56 h at 37 °C and (b) thermal cycling 5000 times. Shear bond strength (SBS) was tested using a universal testing machine, and the fracture modes were observed using an automated chemiluminescence analysis system to assess the effects of Nd: YAG LASER and O2 plasma on the bond strength of PEEK to resin adhesive.

RESULTS

Both Nd: YAG LASER and O2 plasma treatments altered the surface characteristics of PEEK and significantly increased the SBS between PEEK and Variolink N resin adhesive. The L0.75 group (Nd: YAG LASER) and the P35 group (O2 plasma) achieved the highest SBS, respectively. Furthermore, the SBS of the L0.75 group was higher than that of the P35 group. Following thermal cycling, SBS values decreased compared to the water storage subgroups. The fracture modes of the specimens in each group were predominantly interfacial and mixed, with no cohesive fractures observed.

CONCLUSIONS

Nd: YAG LASER irradiation and O2 plasma treatments can improve the SBS between PEEK and resin adhesive, with the 0.75 W Nd: YAG LASER being the preferred treatment method.

Biaxial flexural strength and Weibull characteristics of a resin ceramic material after thermal-cycling

PURPOSE

The purpose of this in vitro study was to compare the flexural strength and Weibull characteristics of 3 different resin-ceramic materials with a zirconia-reinforced lithium silicate material after thermal-cycling.

MATERIAL AND METHODS

Four different computer-aided design and computer-aided manufacturing restorative materials (Vita Enamic, Lava Ultimate, Crystal Ultra, and Vita Suprinity) were tested. A total of 40 Ø12×1.2-mm disks were prepared and divided into 4 groups (n = 10). Their flexural strength was evaluated after 5000 thermal-cycles with a 4-point biaxial flexure test using a universal testing machine. The Weibull modulus and probability of failure were also determined from the biaxial flexural strength data. Data were analyzed with one-way ANOVA and the Tukey pairwise comparison test (α = 0.05).

RESULTS

Significant differences were found among the materials in terms of biaxial flexural strength (p < 0.05). Vita Suprinity had the highest mean ±standard deviation flexural strength (289.1 ± 15.1 MPa), and Vita Enamic had the lowest (100.0 ± 3.2 MPa). The highest Weibull modulus was calculated for Crystal Ultra, followed by Vita Enamic, Lava Ultimate, and Vita Suprinity.

CONCLUSION

Vita Suprinity had the highest flexural strength when compared with the other materials tested. Crystal Ultra had the highest flexural strength among the resin-ceramic materials. The highest Weibull modulus was calculated for Crystal Ultra and the lowest for Vita Suprinity.

The removal of three kinds of occlusal veneers by Er: Yag laser

OBJECTIVES

This study aimed to remove occlusal veneers of varied thicknesses and compositions by Er:Yag laser in vitro and analyze the interfacial microstructure between veneers and tooth that irradiated by laser, by which experimental evidence could be provided to support the non-invasive removal of occlusal veneerby laser.

METHODS

Fresh mandibular premolars extracted for orthodontic requirements were collected for tooth preparation. Three kinds of ceramic materials (Vita Suprinity, Vita Mark Ⅱ, and Upcera Hyramic) were selected to fabricate occlusal veneer with different thicknesses (1.0, 1.5, and 2.0 mm). One week later, Er:Yag laser (2.5 W and 3.5 W) was used to irradiate and remove the occlusal veneer and recorded the timespan. After the removal operation, the micro-morphologies of samples were examined by scanning electron microscope.

RESULTS

Upcera Hyramic veneer failed to be removed (>20 min); the operation span at 2.5 W, Vita Suprinity (96.0 s±16.0 s) was longer than Vita MarkⅡ(84.5 s±19.5 s) in the 1.0 mm group (P<0.05), and Vita Suprinity (246.5 s±13.5 s) was longer than Vita MarkⅡ(170.0 s±14.0 s) in the 1.5 mm group (P<0.05). At 3.5 W, Vita Suprinity (381.0 s±24.0 s) was longer than Vita MarkⅡ(341.5 s±26.5 s) in the 2.0 mm group.

CONCLUSIONS

Increasing laser power could shorten the operation span and facilitate the removal of occlusal veneers with the same thickness and composition. The occlusal veneer was sustained when insufficient laser power was applied. With the same laser power and ceramic thickness, laser penetration could interfere with the integral of the ceramic structure when the laser interacted with the bonding layer. With the same ceramic composition and laser power, the operation span and laser power increased with the thickness of the occlusal veneer. However, the laser was incapable of removing occlusal resin veneer directly.

Shear Bond Strength of Two Repair Systems to Zirconia Ceramic by Different Surface Treatments

Introduction: Intraoral repair has been suggested as a treatment option to repair the chipping or fracture of veneered zirconia; the success of the procedure is mainly determined by the bonding between zirconia and composite resin. The present study aimed to investigate and compare the shear bond strength (SBS) of two intraoral repair systems to zirconia ceramic treated with a laser or air-abrasion surface modification. Methods: Ninety tube-shaped samples (diameter of 10 mm and height of 4 mm) were divided into three main groups: Group I (zirconia 100%, n=30); Group II (veneer ceramic 100% n=30); Group III (zirconia with a veneer ceramic n=30). Each main group was subdivided into two subgroups (n=15): Subgroup A: samples repaired with Ceramic Repair N; Subgroup B: samples repaired with the Cimara Repair System. The subgroup samples were further subdivided based on the treated surface (n=5 samples): Control (no surface modification), Er,Cr:YSGG laser surface modification, and air-abrasion surface modification. The SBS was employed using a universal testing machine. The mode of failure was observed using a stereomicroscope. Results: Significant differences were observed in the mean SBS values between the different surface modifications (P˂0.05). Tukey's post hoc test showed that the air-abrasion surface modification of the veneer ceramic repaired with the Ceramic repair N system had the highest mean value (13.74 MPa) among the different groups, while no surface modification of zirconia repaired with the Cimara repair system had the lowest mean value (2.84 MPa). The control group (no surface modification) had the lowest mean value among all the treated groups. Conclusion: The SBS is surface modification-dependent, and higher SBS is obtained by air-abrasion than Er, Cr:YSGG laser surface modifications with the selected parameters. The Ceramic repair N system had significantly higher SBS for all surface-treated substrates than the Cimara repair system.

Is the Er:YAG laser affect the surface characteristics and bond strength of Y-TZP?

This study evaluated the surface characteristics and bond strength of Y-TZP treated with Er:YAG laser at different focal distances. 120 Y-TZP blocks were divided into five groups (n=24), according to the surface treatment: no treatment (C-); sandblasting with silica-coated aluminum oxide particles (C+); and Er:YAG laser application at focal distances of 1mm (Er:YAG-1), 4mm (Er:YAG-4), and 7mm (Er:YAG-7). Surface characteristics were analyzed using Vickers microhardness, confocal laser microscope, scanning electron microscopy (SEM), and X-ray diffractometer (XRD). For the bond strength test, 100 Y-TZP blocks were subdivided into two subgroups (n=10), according to the resin cement used: with (MDP+) or without 10-methacryloyloxydecyl dihydrogen phosphate (MDP-). The Vickers microhardness and surface roughness were analyzed by one-way ANOVA and bond strength by two-way ANOVA and Tukey's test for both (α=0.05). Vickers microhardness differences were not observed between the groups (p>0.05); C+ showed higher surface roughness values. SEM images showed micromorphological differences between the groups. The XRD data detected tetragonal crystals for C- and, for the other groups, tetragonal and monoclinic peaks. For bond strength, no statistically difference significance were observed among the cements with or without MDP (p>0.05) but showed significant difference between the surface treatments (C+ > C- = Er:YAG1 > Er:YAG4 = Er:YAG7) (p<0.05). Suggested that the Er:YAG laser cannot replace conventional treatment with aluminum oxide particles and the presence of MDP in the resin cement had no influence on the bond strength.

Evaluation of Micro-Shear Bond Strength of Four Different CAD-CAM Polymer-Infiltrated Ceramic Materials after Thermocycling

PURPOSE

To evaluate the bond strength of three monolithic hybrid ceramics/resin nanoceramics and a zirconia-reinforced lithium silicate to resin cement after thermocycling.

MATERIALS AND METHODS

Using four materials, including Vita Enamic (VITA Zahnfabrik), Lava Ultimate (3M ESPE), Crystal Ultra (Digital Dental), and Vita Suprinity (VITA Zahnfabrik), 64 specimens were prepared with dimensions of 4mm×3mm×1.5mm. Vita Suprinity samples were sintered at 840°C for 8 min. After polishing and cleaning all the samples in each group (n = 16), they were subjected to their recommended surface treatment: 10% hydrofluoric acid for Vita Enamic (60s) and Vita Suprinity (20s); air abrasion of Lava Ultimate and Crystal Ultra with 50μ Al₂ O₃ particles. Then, tygon tubes were filled with dual cure resin cement (Panavia F2.0), cured and then subjected to thermal cycling (2000 cycles; 5-55°C). The micro-shear bond strength was measured using micro-tensile testing machine. The data were analyzed using Welch and Games-Howell tests (α = 0.05). The mode of failure was also evaluated using a stereomicroscope.

RESULTS

The highest and the lowest mean micro-shear bond strength belonged to the Crystal Ultra (7.71 ±1.54 MPa) and Vita Suprinity (4.73 ±1.87 MPa) groups, respectively. The differences between groups were significant and Crystal Ultra had higher bond strength in comparison to all three materials (p<.05).

CONCLUSION

Hybrid ceramics showed higher bond strength to resin cements in comparison to resin nanoceramics and zirconia-reinforced lithium silicate materials. This article is protected by copyright. All rights reserved.

Impact of Sandblasting on Morphology, Structure and Conductivity of Zirconia Dental Ceramics Material

Over the last decade, zirconia (ZrO₂)-based ceramic materials have become more applicable to modern dental medicine due to the sustained development of diverse computer-aided design/computer-aided manufacturing (CAD/CAM) systems. However, before the cementation and clinical application, the freshly prepared zirconia material (e.g., crowns) has to be processed by sandblasting in the dental laboratory. In this work, the impact of the sandblasting on the zirconia is monitored as changes in morphology (i.e., grains and cracks), and the presence of impurities might result in a poor adhesive bonding with cement. The sandblasting is conducted by using Al₂O₃ powder (25, 50, 110 and 125 µm) under various amounts of air-abrasion pressure (0.1, 0.2, 0.4 and 0.6 MPa). There has been much interest in both the determination of the impact of the sandblasting on the zirconia phase transformations and conductivity. Morphology changes are observed by using Scanning Electron Microscope (SEM), the conductivity is measured by Impedance Spectroscopy (IS), and the phase transformation is observed by using Powder X-Ray Diffraction (PXRD). The results imply that even the application of the lowest amount of air-abrasion pressure and the smallest Al₂O₃ powder size yields a morphology change, a phase transformation and a material contamination.