Effect of femtosecond laser induced surface patterns on the flexural strength of monolithic zirconia.

To investigate how patterns generated by femtosecond (fs) laser and femtosecond laser power affect the surface roughness (Ra) and biaxial flexural strength (BFS) of monolithic zirconia. Eighty disk-shaped zirconia specimens were divided into eight subgroups (n = 10): Control (C), airborne-particle abrasion (APA), 400 mW fs laser (spiral [SP(400)], square [SQ(400)], circular [CI(400)]), and 700 mW fs laser ([SP(700)], [SQ(700)], [CI(700)]). Ra values were calculated by using a surface profilometer. One additional specimen per group was analyzed with scanning electron microscopy and x-ray diffractometry. BFS values were obtained by using the piston-on-3-ball test. One-way ANOVA and either Tukey's HSD (BFS) or Tamhane's T2 (Ra) tests were used to evaluate data (α = 0.05). Regardless of the pattern and power, fs laser groups had higher Ra than C and APA, while SP groups had lower Ra than CI and SQ groups (p ≤ 0.004). For each pattern, Ra increased with higher laser power (p < 0.001), while the laser power did not affect the BFS (p ≥ 0.793). CI and SQ groups had lower BFS than the other groups (p ≤ 0.040), whereas SP groups had similar BFS to C and APA (p ≥ 0.430). Fs laser microstructuring with spiral surface pattern increased the Ra without jeopardizing the BFS of zirconia. Thus, this treatment might be an option to roughen tested zirconia.

Effect of the thickness of CAD-CAM materials on the shear bond strength of light-polymerized resin cement.

This study aimed to investigate the effect of the thickness of computer aided design-computer aided manufacturing (CAD-CAM) restorative materials on the bond strength of light-polymerized resin cement. Ninety specimens were prepared from three different CAD-CAM materials (a leucite-based glass-ceramic [Empress CAD], a polymer-infiltrated ceramic network [Vita Enamic], and a zirconia-reinforced lithium silicate glass-ceramic [Vita Suprinity]) in different thicknesses (1, 2, and 3 mm). One surface of each specimen was treated by using a single-step self-etching ceramic primer (Monobond Etch & Prime). Light-polymerized resin cement was bonded to treated surfaces by exposure to a light-emitting diode curing unit from the untreated side of the samples. Shear bond strength (SBS) between the ceramic and the resin cement was measured by using a universal testing machine. The leucite-based glass-ceramic had higher SBS values than the other materials at each thickness. For each material, 1 mm-thick specimens had the highest SBS values. The difference between the SBS values of 2 mm- and 3 mm-thick polymer-infiltrated ceramic network was nonsignificant, whereas the SBS values of 2 mm-thick leucite-based glass-ceramic and the zirconia-reinforced lithium silicate glass-ceramic were significantly higher than those of the corresponding 3 mm-thick specimens. The choice of the material and its thickness may be highly important for clinical success when light-polymerized resin cements are used for cementation.

Marginal gap and fracture resistance of implant-supported 3D-printed definitive composite crowns: An in vitro study.

OBJECTIVES: To compare the marginal gap and fracture resistance of implant-supported 3-dimensional (3D) printed definitive composite crowns with those fabricated by using 3 different millable materials. MATERIAL AND METHODS: A prefabricated abutment was digitized by using a laboratory scanner (E4 Lab Scanner) and a complete-coverage maxillary first premolar crown was designed (Dental Designer). Forty crowns were fabricated either by 3D printing (Saremco Print Crowntec, SP) or milling (Brilliant Crios, BC; Vita Enamic, VE; Cerasmart 270, CS) (n = 10). Baseline marginal gap values were evaluated by measuring 60 predetermined points on an abutment (15 points for each side) with a stereomicroscope at ×40 magnification. Marginal gap values were reevaluated after adhesive cementation. Load-to-fracture test was performed by using a universal testing machine. Two-way analysis of variance (ANOVA) was used to evaluate the effect of material type and cementation on marginal gap values. While Tukey HSD tests were used to compare the materials' marginal gap values before and after cementation, the effect of cementation on marginal gap values within each material was analyzed by using paired samples t-tests. Fracture resistance data were analyzed by using 1-way ANOVA (α=0.05). RESULTS: Material type and cementation significantly affected marginal gap values (P < .001). Regardless of cementation, SP had the lowest marginal gap values (P < .001), while the differences among milled crowns were nonsignificant (P ≥ .14). Cementation significantly increased the marginal gap values (P < .001). Material type did not affect fracture resistance values (F = 1.589, P = .209). CONCLUSION: Implant-supported 3D-printed composite crowns showed higher marginal adaptation compared with the milled crowns before and after cementation. In addition, all crowns endured similar forces before fracture.

Combined application of femtosecond laser and air-abrasion protocols to monolithic zirconia at different sintering stages: Effects on surface roughness and resin bond strength.

This study aimed to investigate the effects of femtosecond laser (Fs) and/or air-abrasion protocols on surface roughness (Ra) of zirconia and resin bond strength. Eighty zirconia samples were randomly divided into eight subgroups according to surface treatment protocols: Control (C), Air-abrasion before sintering (ABS), Air-abrasion after sintering (AAS), Air-abrasion before and after sintering (ABS + AAS), Fs laser before sintering (FBS), Fs laser before sintering + air-abrasion after sintering (FBS + AAS), Fs laser after sintering (FAS), and Fs laser after sintering + air-abrasion after sintering (FAS + AAS). Measurements of Ra values were obtained using a surface profilometer. Surface morphological properties were evaluated with scanning electron microscopy (SEM), and crystallographic changes were examined by X-Ray diffractometry (XRD). Self-adhesive resin cement was bonded to zirconia samples, and shear bond strength (SBS) tests were performed. The data were statistically analyzed by one-way ANOVA, followed by Tamhane tests. The control group displayed the lowest Ra and SBS values among all groups. The highest Ra and SBS values were found in the FBS and FBS + AAS groups. Air-abrasion applied before sintering significantly increased the Ra of specimens. FAS, FAS + AAS, and ABS + AAS groups exhibited higher SBS values than AAS and ABS (p < .05). Air-abrasion applied after Fs laser did not produce any significant change in the Ra and SBS compared to Fs laser alone (p > .05). Femtosecond laser application may be a promising method to enhance the surface roughness of zirconia and improve resin bond strength. Air-abrasion at pre- and post-sintered stages may also be a viable surface treatment option.

Effect of air-abrasion at pre- and/or post-sintered stage and hydrothermal aging on surface roughness, phase transformation, and flexural strength of multilayered monolithic zirconia.

This study aimed to evaluate the effect of air-abrasion/sintering order and autoclave aging on the surface roughness (Ra), phase transformation, and biaxial flexural strength (BFS) of monolithic zirconia. A total of 104 monolithic zirconia specimens (Katana ML) were divided into eight groups according to airborne-particle abrasion protocols and hydrothermal aging: control (non-aged: C-, aged: C+), air-abrasion before sintering (BS-, BS+), air-abrasion after sintering (AS-, AS+), and air-abrasion before and after sintering (BAS-, BAS+). A steam autoclave was used for accelerated aging, and Ra values were measured with a surface profilometer. All specimens were analyzed by X-ray diffraction to determine any phase transformation on the zirconia surface. BFS was measured by using the piston-on-three-balls method. Scanning electron microscopy and atomic force microscopy were performed on one specimen per group. BS and BAS groups showed higher Ra values compared with groups C and AS. The aging process significantly increased the monoclinic phase content of all specimens. Lower monoclinic levels were found in AS+ and BAS+ compared with other aged groups. The AS groups exhibited higher flexural strength values relative to control groups, whereas BS groups exhibited significantly lower flexural strength values (p < .05). There was no reduction in flexural strength by using the BAS protocol. Air-abrasion of zirconia at the pre-sintered stage only is not recommended in clinical use because of the remarkable decrease in flexural strength.

Effect of prolonged application of single-step self-etching primer and hydrofluoric acid on the surface roughness and shear bond strength of CAD/CAM materials.

This in vitro study aimed to assess the influence of different concentrations and durations of hydrofluoric acid (HF) and Monobond Etch & Prime (MEP) etching on the surface roughness (Ra ) of different CAD/CAM materials and on the shear bond strength (SBS) of a self-adhesive resin bonded to the materials. Seventy specimens of hybrid ceramic, leucite-based glass-ceramic, lithium disilicate glass-ceramic, and zirconia-reinforced lithium silicate glass-ceramic were prepared and divided into seven groups according to the surface treatments: Control (C); MEP etching for 60 (MEP60 ) and 120 (MEP120 ) s; 5% HF etching for 60 (HF-5%60 ) and 120 (HF-5%120 ) s; 9.5% HF etching for 60 (HF-9.5%60 ) and 120 (HF-9.5%120 ) s. The Ra was measured using a 3D profilometer. All groups were treated with a universal primer except for the C, MEP60 , and MEP120 groups. A self-adhesive resin cement was bonded to all specimens, and the bond strengths were measured using a universal testing machine. All surface treatments increased both Ra and SBS values compared to the control in each material. Neither the duration of surface treatments nor the HF acid concentrations had a statistically significant effect on SBS. Within the limitations of this experimental study, it can be concluded that Monobond Etch & Prime may be a preferable method to achieve high bond strength values.

Effect of Combined Surface Treatments on Surface Roughness and Resin Bond Strength to Y-TZP Ceramic and Nickel-Chromium Metal Alloy.

Objective: This study compared the effects of different surface treatments on the surface roughness (Ra), and shear bond strength (SBS) of resin cement to yttria-stabilized tetragonal zirconia (Y-TZP) ceramic and nickel-chromium (Ni-Cr) base metal alloy, respectively. Materials and methods: Thirty disk-shaped specimens (3 mm height and 10 mm diameter) of each material (Y-TZP and Ni-Cr) were prepared. Both zirconia and metal specimens were randomly assigned to three equal groups, according to the surface treatments (n = 10): sandblasting, sandblasting + Er:YAG laser, and sandblasting + Nd:YAG laser. Resin cement cylinders (4 mm diameter and 3 mm thickness) were placed on each specimen. The SBS tests were performed at a 1 mm per minute crosshead speed through a knife-edge rod after 5000 thermal cycles. The Ra (µm) of the specimens was measured using a profilometer and evaluated topographically by atomic force microscopy and scanning electron microscopy. Analysis of variance, followed by Tukey's honestly significant difference, in addition to the Kruskal-Wallis test, followed by the Mann-Whitney U test, were used for statistical analysis (α = 0.05). Results: Combined sandblasting and laser treatment of the metal groups led to statistically higher Ra values than sandblasting alone (p < 0.05). For Y-TZP, there were no significant differences between the Ra values of the subgroups (p > 0.05). The SBS of the sandblasted metal group was significantly higher than the other two laser-irradiated groups, whereas the SBS of sandblasted zirconia was only significantly higher than the Nd:YAG laser-irradiated group (p < 0.05). Conclusions: Combined laser and sandblasting surface treatments resulted in rougher surfaces than sandblasting alone, especially for the metal specimens. Sandblasting, alone, improved the SBS of resin cement in both metal and zirconia, compared with the laser and sandblasting treatments, combined.

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 (Ra) 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, Ra 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 Ra 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.

Novel ceramic primer vs. conventional treatment methods: Effects on roughness and bond strength of all-ceramic restorations.

PURPOSE: To compare the influence of various surface treatments on the shear bond strength and surface roughness of lithium disilicate glass-ceramics. METHODS: 60 lithium disilicate ceramic samples were prepared according to the manufacturers' instructions and were divided into six groups according to the surface treatment:Control (C), 5% HF etching for 20 and 60 seconds (E20, E60), Monobond Etch & Prime etching (MEP), Nd:YAG (ND) and Er:YAG (ER) laser irradiation. All groups were treated with a universal primer except group MEP. A self-adhesive resin cement was bonded to all groups. The shear bond strengths of the specimens were measured using a universal testing machine while surface roughness was measured using a profilometer. RESULTS: Kruskal-Wallis and Mann-Whitney U tests revealed significant differences (P< 0.05). The shear bond strength of group E60 was higher than the other groups while surface roughness of groups MEP and ER were highest. CLINICAL SIGNIFICANCE: Monobond Etch & Prime might be a useful method in order to obtain adequate bond strength values.

A different wax sculpture technique for implant-retained auricular prosthesis.

Replacement of missing ears is a challenging task in which extensive array of materials and techniques have been employed. This article describes a different and simplified procedure for fabricating auricular prostheses very similar to the intact left ear of the patient. A 65-year-old male patient was referred to the Department of Prosthodontics with the loss of the right ear. In this case, the impression was made using hydrocolloid material (alginate) from the both defected and the opposite side. After hardening of the stone casts, a custom-made transparent splint plate was designed for the left auricular side. The splint was reversed and a cast model of the right auricular side was obtained as pouring the dental stone into transparent orthodontic splint. After getting the impression from cast model, conventional wax pattern and try on process was done. Finally, silicone elastomer was polymerized and the retention of the prosthesis acquired with the magnetic attachments. The technique described is economical, conventional, and time-saving. Furthermore, the prosthesis imitates the patient's intact auricular tissue.