Evaluation of rebonding strengths of leucite and lithium disilicate veneers debonded with an Er:YAG laser.

Resin cements create a high bond between the tooth and ceramic surfaces, thus making it impossible to remove the restoration in one piece. The aims of this study were to evaluate (i) the efficiency of an Er:YAG laser for debonding, and (ii) the changes in the rebonding strength values of all-ceramic veneers, which were removed after laser application. A tooth reduction of 120 extracted human maxillary central incisors was made to provide two different bonding surfaces (60 enamel and 60 dentin). Sixty leucite and 60 lithium disilicate discs (1-mm thickness, 5-mm diameter) were cemented to prepared surfaces with a dual-cure resin cement. Each group was divided into two subgroups (n = 15): control and laser-irradiated. Er:YAG laser (2940 nm) was applied for 9 s at 3 W power (10 Hz, 300 mJ) with 100 µs pulse duration. Shear bond strength (SBS) test was made with a universal testing machine. After the tested laser-irradiated specimens had been rebonded, the SBS test was performed again and rebonding strengths were measured. The statistical evaluations were performed by using repeated measures one-way ANOVA and post hoc Bonferroni tests (p < 0.05). Significant differences were found between the control and laser-irradiated groups (p < 0.001). While the required SBS values for control groups were between 30.04 and 24.66 MPa, the values for laser-irradiated groups were between 6.60 and 4.09 MPa. There was no significant difference between the control and rebonded groups. Er:YAG laser-irradiation is an effective method for removing all-ceramic restorations without affecting the rebonding strength.

Comparative study of the effect of Er:YAG and Er:Cr;YSGG lasers on porcelain: etching for the bonding of orthodontic brackets.

This study investigated the effect of Er:YAG (smart 2940 Dplus, DEKA, Italy) and Er:CrYSGG (Waterlase iPlus, Biolase, USA) lasers on the shear bond strength (SBS) between the orthodontic brackets and dental porcelain in comparison with conventional acid etching with 9% hydrofluoric acid (HF, Ultradent, USA). A total of 60 specimens of maxillary incisor crown were prepared and randomly assigned to five groups; each group was subjected to a different porcelain surface conditioning: (1) etching with the 9% HF for 2 min; (2) etching with the 9% HF for 2 min followed by irradiation with the Er:CrYSGG laser (3-W power, 10-Hz frequency for 10 s); (3) etching with the 9% HF for 2 min followed by irradiation with the Er:YAG laser (3-W power, 10-Hz frequency for 10 s); (4) Irradiation with the Er:CrYSGG laser (3-W power, 10-Hz frequency for 10 s without acid etching) and (5) irradiation with the Er:YAG laser (3-W power,10-Hz frequency for 10 s without acid etching). After using Transbond XT primer and Transbond XT adhesive, the metal brackets (Dentaurum, Germany equilibrium 2, optimal design) bonded to the conditioned porcelain surface. Subsequently, the specimens were thermocycled for 5000 cycles and then debonded using the Universal Testing Machine (Zwick). In each group, one specimen was not bonded to brackets to allow further examination with electron microscopy. After debonding, the specimens were examined by stereomicroscope to determine their adhesive remnant index (ARI). The average SBS [Mean (SD)] values in the five groups were as follows: HF (32.58 ± 9.21 MPa), Er:CrYSGG + HF (27.81 ± 7.66 MPa), Er:YAG + HF (23.08 ± 9.55 MPa), Er:CrYSGG (14.11 ± 9.35 MPa), and Er:YAG (6.30 ± 3.09 MPa). A statistically significant difference in SBS existed between the first three groups and the two laser groups (df = 4, F = 18.555, p < 0.001). Evaluation of ARI values showed that bond failures in the first three groups were mostly of cohesive and mixed types, but in the laser groups, they were mostly adhesive. Chi-square was not significant between groups (p = 0.219). The Er:YAG laser with the stated specifications is not a suitable alternative to HF etching. In the case of Er:CrYSGG laser, although the conditioning outcome met the bond strength requirement for orthodontic brackets (that is, 6-8 MPa). Therefore, the bond strength must be further improved by fine-tuning the irradiation details.

Scanning electron microscope comparative surface evaluation of glazed-lithium disilicate ceramics under different irradiation settings of Nd:YAG and Er:YAG lasers.

OBJECTIVE: To evaluate the surface of glazed lithium disilicate dental ceramics after irradiation under different irradiation settings of Nd:YAG and Er:YAG lasers using a scanning electron microscope (SEM). MATERIALS AND METHODS: Three glazed-press lithium disilicate ceramic discs were treated with HF, Er:YAG, and Nd:YAG, respectively. The laser-setting variables tested were laser mode, repetition rate (Hz), power (W), time of exposure (seconds), and laser energy (mJ). Sixteen different variable settings were tested for each laser type, and all the samples were analyzed by SEM at 500× and 1000× magnification. RESULTS: Surface analysis of the HF-treated sample showed a typical surface texture with a homogenously rough pattern and exposed ceramic crystals. Er:YAG showed no effect on the surface under any irradiation setting. The surface of Nd:YAG-irradiated samples showed cracking, melting, and resolidifying of the ceramic glaze. These changes became more pronounced as the power increased. At the highest power setting (2.25 W), craters on the surface with large areas of melted or resolidified glaze surrounded by globules were visible. However, there was little to no exposure of ceramic crystals or visible regular surface roughening. CONCLUSIONS: Neither Er:YAG nor Nd:YAG dental lasers exhibited adequate surface modification for bonding of orthodontic brackets on glazed lithium disilicate ceramics compared with the control treated with 9.5% HF.

Shear bond, wettability and AFM evaluations on CO2 laser-irradiated CAD/CAM ceramic surfaces.

The purpose of this study is to determine the CO2 laser irradiation in comparison with sandblasting (Sb), hydrofluoric acid (Hf) and silane coupling agent (Si) on shear bond strength (SBS), roughness (Rg) and wettability (Wt) of resin cement to CAD/CAM ceramics. Sixty (CAD/CAM) ceramic discs were prepared and distributed into six different groups: group A, control lithium disilicate (Li); group B, control zirconia (Zr); group C, Li: CO2/HF/Si; group D, Li: HF/Si; group E, Zr: CO2/Sb/Si; group F, Zr: Sb/Si. Result showed significant difference between irradiated and non-irradiated in terms of shear bond strength for zirconia ceramics (p value = 0.014). Moreover, partial surface wettability for irradiated and non-irradiated ceramics. Irradiated surface demonstrated more rough surface in lithium disilicate than zirconia ceramics. CO2 irradiation could increase shear bond strength, surface roughness and wettability for both CAD/CAM ceramics.

Effect of Ti:sapphire laser on shear bond strength of orthodontic brackets to ceramic surfaces.

BACKGROUND AND OBJECTIVES: With increasing demand for orthodontic treatments in adults, orthodontists continue to debate the optimal way to prepare ceramic surfaces for bonding. This study evaluated the effects of a Ti:sapphire laser on the shear bond strength (SBS) of orthodontic brackets bonded to two ceramic surfaces (feldspathic and IPS Empress e-Max) and the results were compared with those using two other lasers (Er:YAG and Nd:YAG) and 'conventional' techniques, i.e., sandblasting (50 µm) and hydrofluoric (HF) acid. MATERIALS AND METHODS: In total, 150 ceramic discs were prepared and divided into two groups. In each group, the following five subgroups were prepared: Ti:sapphire laser, Nd:YAG laser, Er:YAG laser, sandblasting, and HF acid. Mandibular incisor brackets were bonded using a light-cured adhesive. The samples were stored in distilled water for 24 hours at 37°C and then thermocycled. Extra samples were prepared and examined using scanning electron microscopy (SEM). SBS testing was performed and failure modes were classified. ANOVA and Tukey's HSD tests were used to compare SBS among the five subgroups (P < 0.05). RESULTS: Feldspathic and IPS Empress e-Max ceramics had similar SBS values. The Ti:sapphire femtosecond laser (16.76 ± 1.37 MPa) produced the highest mean bond strength, followed by sandblasting (12.79 ± 1.42 MPa) and HF acid (11.28 ± 1.26 MPa). The Er:YAG (5.43 ± 1.21 MPa) and Nd:YAG laser (5.36 ± 1.04 MPa) groups were similar and had the lowest SBS values. More homogeneous and regular surfaces were observed in the ablation pattern with the Ti:sapphire laser than with the other treatments by SEM analysis. CONCLUSIONS: Within the limitations of this in vitro study, Ti:sapphire laser- treated surfaces had the highest SBS values. Therefore, this technique may be useful for the pretreatment of ceramic surfaces as an alternative to 'conventional' techniques.

Effect of engraving speeds of CO2 laser irradiation on In-Ceram Alumina roughness: a pilot study.

OBJECTIVES: The aim of the study was to determine the effect of CO2 laser on surface roughness of In-Ceram-Alumina-ceramic. MATERIALS AND METHODS: Four aluminum-oxide ceramic disc specimens were prepared of In-Ceram Alumina. Discs received CO2 laser irradiation with different engraving speeds (100, 400, 600 and 800 mm/min) as a surface treatment. The roughness of the surfaces was measured on digital elevation models reconstructed from stereoscopic images acquired by scanning-electron-microscope. Surface roughness data were analyzed with One-Way-Analysis-of-Variance at a significance level of p<0.05. RESULTS: There was no significant difference between the roughness values (p=0.82). Due to higher laser durations, partial melting signs were observed on the surfaces. Tearing, smearing and swelling occurred on melted surfaces. Swelling accompanying melting increased the surface roughness, while laser power was fixed and different laser engraving speeds were applied. CONCLUSION: Although different laser irradiation speeds did not affect the roughness of ceramic surfaces, swelling was observed which led to changes on surfaces.

CO2 Laser Glazing Treatment of a Veneering Porcelain: Effects on Porosity, Translucency, and Mechanical Properties.

This work tested CO2 laser as a glazing agent and investigated the effects of irradiation on the porosity, translucency, and mechanical properties of veneering porcelain. Sixty discs (diameter 3.5 × 2.0 mm) of veneering porcelain for Y-TZP frameworks (VM9, VITA Zahnfabrik) were sintered and had one of their faces mirror polished. The specimens were divided into six groups (n=10/group) according to surface treatment, as follows: no treatment-control; auto-glaze in furnace following manufacturer's instructions (G); and CO2 laser (45 or 50 W/cm(2)) applied for four or five minutes (L45/4, L45/5, L50/4, L50/5). Optical microscopy (Shimadzu, 100×) was conducted and the images were analyzed with Image J software for the determination of the following porosity parameters: area fraction, average size, and Feret diameter. The translucency parameter studied was masking ability, determined by color difference (ΔE) over black and white backgrounds (CM3370d, Konica Minolta). Microhardness and fracture toughness (indentation fracture) were measured with a Vickers indenter (HMV, Shimadzu). Contact atomic force microscopy (AFM) (50 × 50 µm(2), Nanoscope IIIA, Veeco) was performed at the center of one sample from each group, except in the case of L45/5. With regard to porosity and translucency parameters, auto-glazed and laser-irradiated specimens presented statistical similarity. The area fraction of the surface pores ranged between 2.4% and 5.4% for irradiated specimens. Group L50/5 presented higher microhardness when compared to the G group. The higher (1.1) and lower (0.8) values for fracture toughness (MPa.m(1/2)) were found in laser-irradiated groups (L50/4 and L45/4, respectively). AFM performed after laser treatment revealed changes in porcelain surface profile at a submicrometric scale, with the presence of elongated peaks and deep valleys.

Effectiveness of silica-lasing method on the bond strength of composite resin repair to Ni-Cr alloy.

PURPOSE: The aim of this study was to evaluate the effectiveness of silica-lasing method for improving the composite resin repair of metal ceramic restorations. MATERIALS AND METHODS: Sixty Ni-Cr cylindrical specimens were fabricated. The bonding surface of all specimens was airborne-particle abraded using 50 µm aluminum oxide particles. Specimens were divided into six groups that received the following surface treatments: group 1-airborne-particle abrasion alone (AA); group 2-Nd:YAG laser irradiation (LA); group 3-silica coating (Si-CO); group 4-silica-lasing (metal surface was coated with slurry of opaque porcelain and irradiated by Nd:YAG laser) (Si-LA); group 5-silica-lasing plus etching with HF acid (Si-LA-HF); group 6-CoJet sand lased (CJ-LA). Composite resin was applied on metal surfaces. Specimens were thermocycled and tested in shear mode in a universal testing machine. The shear bond strength values were analyzed using ANOVA and Tukey's tests (α = 0.05). The mode of failure was determined, and two specimens in each group were examined by scanning electron microscopy and wavelength dispersive X-ray spectroscopy. RESULTS: Si-CO showed significantly higher shear bond strength in comparison to other groups (p < 0.001). The shear bond strength values of the LA group were significantly higher than those of the AA group (p < 0.05). No significant difference was found among lased groups (LA, Si-LA, Si-LA-HF, CJ-LA; p > 0.05). The failure mode was 100% adhesive for AA, Si-LA, Si-LA-HF, and CJ-LA. LA and Si-CO groups showed 37.5% and 87.5% cohesive failure, respectively. CONCLUSION: Silica coating of Ni-Cr alloy resulted in higher shear bond strength than those of other surface treatments.

Quantification of the amount of blue light passing through monolithic zirconia with respect to thickness and polymerization conditions.

STATEMENT OF PROBLEM: Dual-polymerized luting composite resin cements would benefit from enhanced irradiance transmitted through a ceramic restoration. A quantification of the amount of transmitted light through translucent zirconia is lacking. PURPOSE: The purpose of this study was to evaluate the amount of light (360 to 540 nm) passing through translucent and conventional zirconia and a glass ceramic with respect to material thickness and different polymerizing modes. MATERIAL AND METHODS: Six translucent and a conventional zirconia (negative control) and a glass ceramic (positive control) were considered. Ten specimens of each material and thickness (.5, 1, 1.5, 2, 2.5, 3 mm) were fabricated (n=480). Zirconia materials were sintered according to manufacturers' instructions. The irradiance passing the different ceramics and thicknesses was measured with a violet-blue LED polymerizing unit in 3 polymerizing modes (plasma, high, and standard power mode) with a USB4000 Spectrometer. The polymerizing unit was placed directly on the specimen's surface. Data were analyzed with one and multivariate analysis and the Pearson correlation analysis (α=.05). RESULTS: In all materials, the translucency and its rate decreased exponentially according to the specimen thickness. The highest influence on the measured irradiance passing through translucent zirconia was exerted by ceramic thickness (P<.05, partial eta squared [ηP²]=.998), closely followed by polymerizing mode (ηP²=.973), while the effect of the material (P=.03, ηP²=.06) and mean grain size (P=.029, ηP²=.027) was significant but low. CONCLUSIONS: Zirconia was less translucent than the glass ceramic, but the translucency decreased more slowly with material thickness, thus approaching the translucency of glass ceramics at a specimen thicknesses of 2.5 to 3 mm.

Do surface treatments affect the optical properties of ceramic veneers?

STATEMENT OF PROBLEM: Surface treatments may affect the optical properties of ceramic veneers before cementation. PURPOSE: The purpose of this study was to evaluate whether various surface treatments affect the optical properties of different types of ceramic veneers. MATERIAL AND METHODS: Disk-shaped ceramic veneers (N=280) were prepared from the IPS e.max Press, e.max CAD, Empress Esthetic, e.max Ceram, and Inline ceramic systems with 0.5-mm and 1.0-mm thicknesses. The ceramics were divided into 4 groups: no surface treatments; etched with hydrofluoric acid; airborne-particle abraded with 30-µm Al2O3; and irradiated with erbium:yttrium-aluminum-garnet laser. A translucent shade of resin was chosen for cementation. Color parameters were examined with a colorimeter. Statistical analyses were done with 3-way ANOVA and the Bonferroni test (P=.05). RESULTS: Significant interactions were noted between the surface treatments, ceramic type, and thickness for ΔE values (P=.01), and no significant interactions were noted for L* (P=.773), a* (P=.984), and b* (P=.998). The greatest color change occurred after airborne-particle abrasion with 0.5-mm-thick e.max Press (2.9 ΔE). Significant differences in ΔE values were found among the hydrofluoric acid, airborne-particle abrasion, and laser groups for 0.5-mm-thick ceramics, except IPS Inline, and among the hydrofluoric acid, airborne-particle abrasion, and laser groups for 1.0-mm-thick ceramics, except Empress Esthetic ceramics. CONCLUSIONS: The color change of the ceramics increased after the surface treatments, particularly as the ceramics became thinner.

Influence of ceramic thickness and type on micromechanical properties of light-cured adhesive bonding agents.

OBJECTIVE: The aim of this study was to evaluate the micromechanical properties of different adhesive bonding agents when polymerized through ceramics. MATERIALS AND METHODS: Sixty sound extracted human third molars were selected and the crowns were sectioned perpendicular to the long axis in order to obtain dentin slices to be bonded with one of the following adhesives: Syntac/Heliobond (Ivoclar-Vivadent) or Adper-Scotchbond-1XT (3M-ESPE). The adhesives were cured by using a LED-unit (Bluephase®, Ivoclar Vivadent) with three different curing times (10 s, 20 s and 30 s) under two ceramics (IPS-e.max-Press, Ivoclar-Vivadent; IPS-Empress®CAD, Ivoclar-Vivadent) of different thicknesses (0 mm, 0.75 mm, 2 mm). Thirty groups were included, each containing 60 measurements. Micromechanical properties (Hardness, HV; indentation modulus, E; and creep, Cr) of the adhesives were measured with an automatic microhardness indenter (Fisherscope H100C, Germany). Data were statistically analyzed by using one-way ANOVA and Tukey's post-hoc test, as well as a multivariate analysis to test the influence of the study parameters (SPSS 18.0). RESULTS: Significant differences were observed between the micromechanical properties of the adhesives (p < 0.05). The ceramic type showed the highest effect on HV (Partial-eta squared (η(2)) = 0.109) of the tested adhesives, while E (η(2) = 0.275) and Cr (η(2) = 0.194) were stronger influenced by the adhesive type. Ceramic thickness showed no effect on the E and Cr of the adhesives. CONCLUSIONS: The adhesive bonding agents used in this study performed well by curing through different thicknesses of ceramics. The micromechanical properties of the adhesives were determined by the adhesive type and were less influenced by ceramic type and curing time.

Effect of ultraviolet aging on translucency of resin-cemented ceramic veneers: an in vitro study.

PURPOSE: The aim of this in vitro study was to evaluate the translucency of ceramic veneers cemented with light- or dual-cured resin cements after accelerated aging. MATERIALS AND METHODS: A total of 392 specimens were made of shade A1 with 0.5- and 1.0-mm thickness. Light-cured RelyX Veneer and dual-cured Maxcem Elite and Variolink II resin cements were applied on the porcelain discs with a thickness of 0.1 mm. Translucency parameter (TP) values of the ceramic veneers after cementation and UV aging test were evaluated. Statistical analyses were done with ANOVA and Tukey's tests and paired sample t-test (p < 0.05). RESULTS: All the resin cements affected the TP values of 0.5-mm-thick ceramic, while RelyX Veneer Tr (TP = 11.15; p = 0.608), Variolink II Tr (TP = 10.98; p = 0.55), and Maxcem Clear (TP = 11.81; p = 0.702) did not affect the translucency of 1-mm-thick ceramics (TP = 11.38). The aging process affected TP values of both ceramics and cemented ceramics, as the TP values decreased after aging. Among the TP values of opaque shade resin cements, there were significant differences between the "ceramic," "ceramic + RelyX Veneer WO," "ceramic + Variolink II WO," and "ceramic + Maxcem WO" variables for both 0.5 and 1 mm thicknesses (p < 0.05). There were no significant differences between "ceramic," "ceramic + RelyX Veneer Tr," "ceramic + Variolink II Tr," and "ceramic + Maxcem Clear" variables at 0.5 mm thickness, and there were no significant differences between "ceramic," "ceramic + RelyX Veneer Tr," and "ceramic + Variolink II Tr" variables after aging (p > 0.05). CONCLUSIONS: The TP of the same color of resin cements varied related to the type or brand. Aging caused both the ceramics and cemented ceramics to become more opaque.

Effect of various surface treatments on the bond strength of porcelain repair.

This study evaluated the effect of surface treatments on the repair strength of composite resin on a feldspathic ceramic. Ninety ceramic specimens were divided into six groups. In the experimental groups, 4% hydrofluoric acid etching, Er:YAG laser irradiation, CO2 laser irradiation, airborne-particle abrasion, and silica coating were used as surface treatments. After the application of a porcelain repair kit, composite resin was placed on the treated surfaces. After a shear bond strength test, data were statistically analyzed (α = .05). Surface treatments increased the repair bond strength values (P < .05). Airborne particle abrasion and silica coating were found to be the most effective. CO2 laser showed higher repair strength values than Er:YAG laser.

Shear bond strength of orthodontic brackets bonded to porcelain following etching with Er:YAG laser versus hydrofluoric acid.

AIM: The purpose of the present study was to evaluate the shear bond strength of orthodontic brackets bonded to porcelain following etching with erbium-doped yttrium aluminum garnet (Er:YAG) laser compared with 9.6% hydrofluoric acid (HF). METHODS: A total of 100 porcelain disk samples were divided into four groups, and after removing their glazed layer, the first group was etched with 9.6% HF, and the other three groups were etched with Er:YAG lasers of 1.6, 2, and 3.2 W, respectively. After application of silane on the disk surfaces, central incisor brackets were bonded with composite on the disks. The disks were mounted on an acrylic stand for measuring the shear bond strengths. The shear bond strengths were measured by a testing machine. RESULTS: The mean shear bond strength in the laser group with power of 1.6 W (7.88 MPa) was more than that of the HF (7.4MPa), 2-W power (7.52 MPa), and 3.2-W power (7.45 MPa) groups, but this difference was not statistically significant. Examination with an electron microscope showed different patterns of etching by HF and laser. Also, etching by laser and HF had not resulted in cracks on the porcelain surface. CONCLUSION: Er:YAG laser can be a suitable method for bonding of orthodontic brackets to porcelain surfaces.

Comparative study of shade matching performance of dental students under natural daylight and daylight lamp conditions.

BACKGROUND: As visual shade matching is subject to light source variables, this study was conducted to compare shade matching performance of dental students under two lighting conditions, ie, natural daylight and a commercially available daylight lamp. MATERIALS AND METHODS: Two sets of porcelain discs were prepared. The first set consisted of eight porcelain discs of shades A2, A3, A3.5, B2, B3, C2, C3, and D3 of the Vitapan Classical Shade Guide system. The second set consisted of three porcelain discs of shade A2, B2, and C2, having exactly similar L*a*b* values to those of the corresponding shade discs in the first set. Forty dental students were asked to find the closest match for the shades A2, B2, and C2 in the second set from the first set under natural daylight and daylight lamp conditions. The average ΔE between the presented and selected shade was calculated for each participant under the two lighting conditions. The significance was statistically assessed using a paired t test. RESULTS: The average ΔE between presented and selected shade for individual participants under natural daylight ranged from 0 to 4.84, with a mean of 2.24, while those under daylight lamp conditions ranged from 0 to 3.68, with a mean of 1.14. The difference was statistically significant, with P < 0.0001. CONCLUSION: Daylight lamp conditions significantly improved the shade matching performance of dental students.

CO2 laser conditioning of porcelain surfaces for bonding metal orthodontic brackets.

Bonding to porcelain remains to be a challenge in orthodontic treatments. The objective of this study was to evaluate the effect of CO2 laser conditioning of porcelain surfaces on shear bond strength (SBS) of orthodontic brackets. Eighty feldspathic porcelain specimens were divided into four groups of 20. In each group, half of the porcelain surfaces were deglazed, while the others remained glazed. The specimens in groups 1 to 3 were treated with a fractional CO2 laser for 10 s using 10 mJ of energy, frequency of 200 Hz and powers of 10 W (group 1), 15 W (group 2) and 20 W (group 3). In group 4, a 9.6 % hydrofluoric (HF) acid gel was used for 2 min. A silane coupling agent was applied before bracket bonding, and the SBS was measured with a universal testing machine after 24 h. Deglazing caused significant increase in SBS of laser treated porcelain surfaces (p < 0.05), but had no significant effect on SBS when HF acid was used for etching (p = 0.137). ANOVA revealed no significant difference in SBS values of the study groups when glazed surfaces were compared (p = 0.269). However, a significant between group difference was found among the deglazed specimens (p < 0.001). Tukey test revealed that the bond strengths of 10 W and 15 W laser groups were significantly higher than that of the HF acid group (p < 0.05). Laser conditioning with a fractional CO2 laser can be recommended as a suitable alternative to hydrofluoric acid for deglazed feldspathic porcelain.

Comparison of the effects of surface treatments on roughness of two ceramic systems.

OBJECTIVE: The aim of this study was to evaluate the effects of different surface treatments on the surface roughness of lithium disilicate-based core (IPS Empress 2, shade 210, Ivoclar Vivadent, Schaan, Liechtenstein) and feldspathic ceramics (Vita VM9, VITA Zahnfabrik H. Rauter GmbH & Co. KG, Bad Säckingen, Germany). BACKGROUND DATA: Er:YAG laser irradiation is expected to be an alternative surface treatment, thus enhances surface roughness of procelains and produces morphological changes. METHODS: Fifty lithium disilicate-based core ceramic discs and 50 feldspathic ceramic discs were prepared (diameter, 10 mm; thickness, 1 mm) according to the manufacturers' instructions. All-ceramic discs were polished to standardize, and surface roughness of the discs was evaluated before treatment and serving as controls. Both of two ceramic groups were divided into five groups (n=10), and the following treatments were applied: (1) sandblasting with aluminum oxide (Al(2)O(3); Group SB); (2) Al(2)O(3)+Er:YAG laser (Group SB-L); (3) Er:YAG laser irradiation (distance, 1 mm; 500 mJ; 20 Hz; 10W; manually, contact handpiece [R 14]) (Group L); (4) 5% hydrofluoric acid etching (Group HF); and (5) Er:YAG laser +5% hydrofluoric acid (Group HF-L). Surface roughness was evaluated by profilometry, and specimens were then examined with atomic force microscopy. RESULTS: Data were analyzed by Wilcoxon signed rank, Mann-Whitney U, and Kruskal-Wallis tests (α=0.05). The Wilcoxon signed rank test results indicated that surface roughness after sandblasting was significantly different from the surface roughness after laser irradiation and acid etching (p<0.001). Mann-Whitney U and Kruskal-Wallis test results indicated that groups SB and SB-L had significantly higher mean roughness values (p<0.05) than those in the other groups. CONCLUSIONS: Groups SB and SB-L had rougher surfaces than the groups subjected to the other surface treatment methods. There was no significant difference in surface roughness between the HF acid etching, Er:YAG laser irradiation, and HF and Er:YAG (p<0 .05).

Effect of different surface treatments on roughness of IPS Empress 2 ceramic.

The aim of this study was to evaluate the influence of different surface treatments (air abrasion, acid etching, laser irradiation) on the surface roughness of a lithium-disilicate-based core ceramic. A total of 40 discs of lithium disilicate-based core ceramic (IPS Empress 2; Ivoclar Vivadent, Schaan, Liechtenstein) were prepared (10 mm in diameter and 1 mm in thickness) according to the manufacturer's instructions. Specimens were divided into four groups (n = 10), and the following treatments were applied: air abrasion with alumina particles (50 µm), acid etching with 5% hydrofluoric acid, Nd:YAG laser irradiation (1 mm distance, 100 mJ, 20 Hz, 2 W) and Er:YAG laser irradiation (1 mm distance, 500 mJ, 20 Hz, 10 W). Following determination of surface roughness (R(a)) by profilometry, specimens were examined with atomic force microscopy. The data were analysed by one-way analysis of variance (ANOVA) and Tukey HSD test (α = 0.05). One-way ANOVA indicated that surface roughness following air abrasion was significantly different from the surface roughness following laser irradiation and acid etching (P < 0.001). The Tukey HSD test indicated that the air abrasion group had a significantly higher mean value of roughness (P < 0.05) than the other groups. No significant difference was found between the acid etching and laser irradiation (both Er:YAG and Nd:YAG) groups (P > 0.05). Air abrasion increased surface roughness of lithium disilicate-based core ceramic surfaces more effectively than acid-etching and laser irradiation.

An analysis of the shear strength of the bond between enamel and porcelain laminate veneers with different etching systems: acid and Er,Cr:YSGG laser separately and combined.

Conditioning of the enamel surface is now an accepted and widely applied technique used to improve retention in porcelain laminate veneer restorations. The aim of this study was to evaluate strength of the bond between porcelain laminate veneers and tooth surfaces etched with acid and laser, separately and together. The teeth studied comprised 60 incisors extracted for periodontal reasons. These were divided into four groups according to etching method: group 1, acid etching alone; group 2, acid etching followed by laser etching; group 3, laser etching followed by acid etching; group 4, laser etching alone. The teeth were etched with 37% phosphoric acid and a Er,Cr:YSGG laser system. In addition, 60 IPS Empress II cylindrical blocks 2 mm in height and 5 mm in diameter were also prepared for the etched tooth surface. These blocks were bonded to the teeth with dual cured resin cement and shear tests were then performed. After the shear tests, Scanning electron microscopy images of the tooth surfaces were obtained at a magnification of ×3,800. Etching with acid alone yielded the highest mean value of bond shear strength (15.4±3.8 MPa), while laser etching followed by acid etching gave the lowest mean value (11.5±4.6 MPa). The mean values of the bond shear strength for acid etching followed by laser etching and laser etching alone were 13.8±3.9 MPa and 12.8±4.6 MPa, respectively. Statistical analysis revealed no significant differences between the groups. The results suggest that laser etching is easy to apply and less time-consuming. They further suggest that the order in which the acid and laser are applied in combined treatments is important.

Carbon dioxide laser application enhances the effect of silane primer on the shear bond strength between porcelain and composite resin.

The purpose of this study was to evaluate the effect of carbon dioxide laser irradiation on the performance of silane coupling agent as an adhesion promoter. The carbon dioxide laser used in this study was Opelaser 03S II, which irradiated the silane coupling agent applied on the adhesive surface of porcelain. Before and after thermal cycling, shear bond strength was measured using a universal testing machine. Without primer treatment, most of the specimens failed adhesively before reaching the end of the thermal cycling period. For the specimens irradiated with carbon dioxide laser after primer treatment, their shear bond strengths before and after thermal cycling were higher than those treated with primer only -with a significantly pronounced difference between these two groups especially after thermal cycling. Therefore, a combined surface treatment which involved silane application followed by laser treatment was feasible and efficacious for chairside porcelain repair.