Surface treatment of feldspathic porcelain: scanning electron microscopy analysis

Advances in ceramics for tooth repair: From bench to chairside

OBJECTIVES

To give a comprehensive review of advancement in dental ceramics, fabrication methods, and the challenges associated with clinical application.

DATA, SOURCES AND STUDY SELECTION

Researches on chemical composition, biomechanical behaviors, optical properties, bonding strategies and fabrication methods were included. The search of articles was independently conducted by two authors in the PubMed, Scopus, Medline and Web of Science.

CONCLUSIONS

Dental ceramics have shown significant advancements in terms of esthetics and function. However, improving fracture toughness without compromising optical properties remains a challenge. Repairing fractured zirconia or glass-matrix ceramic prostheses with the same material is difficult due to the sintering process. Developing innovative bonding techniques that provide strong and long-lasting bonding strength between ceramics and tooth structures poses a recurring obstacle.

CLINICAL SIGNIFICANCE

Despite the emergence of dental ceramics and fabrication techniques, certain limitations such as susceptibility to brittleness and fracture still exist. Therefore, the current review provided valuable information around the advanced dental ceramics in tooth repair. The laboratory test data and the clinical outcome are also presented in details, aiming to guide clinicians in making informed decisions regarding ceramic restorations.

Resin Cement Residue Removal Techniques: In Vitro Analysis of Marginal Defects and Discoloration Intensity Using Micro-CT and Stereomicroscopy

The objective was to compare marginal defects and evaluate discoloration for adhesively cemented veneers in vitro when using two cement removal techniques. Twenty premolars were prepared with chamfer and borders in enamel. IPS e.max CAD veneers were cemented using Panavia V5 and divided in two groups (n = 10): cement excess removed with a probe after tack-curing for 3–5 s, or cement excess removed with a brush, then completely polymerized. All teeth were stored in alginate gel until micro-CT examination. Scanning was performed twice: directly after cementation and after thermocycling (5000 cycles, between 5 and 55 °C). To analyze discoloration, teeth were colored using 0.5% basic fuchsine and examined under a stereomicroscope. Depth of dye infiltration was scored 0 (no discoloration) to 5 (discoloration along the entire margin). Statistically significant differences of cement defects before thermocycling were reported, where brushing showed more defects than probing (p = 0.0161). After thermocycling, the defects increased for both groups. Extensive discoloration was the most common (55.56%) when removing excess by probing; by brushing, 90% of the specimens exhibited slight discoloration (p = 0.008). Regression analysis showed no relationship between type of defect and degree of discoloration. Removing cement with a brush causes more marginal defects, however less discoloration after thermocycling.

Contemporary Approach to the Porosity of Dental Materials and Methods of Its Measurement

Porosity is an important parameter for characterizing the microstructure of solids that corresponds to the volume of the void space, which may contain fluid or air, over the total volume of the material. Many materials of natural and technically manufactured origin have a large number of voids in their internal structure, relatively small in size, compared to the characteristic dimensions of the body itself. Thus, porosity is an important feature of industrial materials, but also of biological ones. The porous structure affects a number of material properties, such as sorption capacity, as well as mechanical, thermal, and electrical properties. Porosity of materials is an important factor in research on biomaterials. The most popular materials used to rebuild damaged tooth tissues are composites and ceramics, whilst titanium alloys are used in the production of implants that replace the tooth root. Research indicates that the most comprehensive approach to examining such materials should involve an analysis using several complementary methods covering the widest possible range of pore sizes. In addition to the constantly observed increase in the resolution capabilities of devices, the development of computational models and algorithms improving the quality of the measurement signal remains a big challenge.

The Effect of Different Polishing Systems on the Surface Roughness of Nanocomposites: Contact Profilometry and SEM Analyses

The aim of this study was to evaluate the effects of different polishing systems on the surface roughness of different nanocomposite resins using various analysis methods. Three types of nanocomposite resins were investigated in this study: supra-nanohybrid (Estelite Asteria), nanohybrid (GrandioSo), and nanoceramic composite resins (Ceram-X Spheretec One). Forty-eight disc-shaped specimens (4 mm in diameter, 2 mm in thickness) were fabricated using a Teflon mold and divided into four groups according to the different polishing systems (n=12). All specimens were processed with one of the following methods: Mylar strip (control), one-step polishers (Opti1step), two-step polishers (Clearfil TwistDia), or multistep polishers (Sof-Lex XT Pop-on). The surface roughness (Ra, μm) was measured by contact profilometry (Mahr, Marsurf PS1) (n=10) and scanning electron microscopy (SEM) (Thermo Fisher Scientific, Phenom XL) at 400× magnification (n=2). The data were statistically analyzed using Kruskal-Wallis and Bonferroni correction tests (p<0.05). In addition, the surface morphology and elemental content were examined by SEM and energy dispersive x-ray spectroscopy (EDS) analyses. Under SEM evaluation, in terms of the polishing systems, there were no significant differences in the surface roughness for supra-nanohybrid composite resin (p>0.05). The multistep polishers created lower surface roughness than the one-step polishers for nanohybrid and nanoceramic composites. In terms of the composite resins, supra-nanohybrid composite exhibited lower surface roughness than nanohybrid composite for all polishing systems (p<0.05). The SEM observations confirmed the surface roughness measurements related to the surface morphology. One-step and two-step polishers created porosity on the surface of nanohybrid and nanoceramic composites. EDS analysis indicated the elemental composition of the particles in the porous zones was quite close to diamond abrasives and glass fillers.

The Effect of Thermocycling and Surface Treatments on the Surface Roughness and Microhardness of Three Heat-Pressed Ceramics Systems

Dental ceramic restorations are widely used in restorative dentistry. However, these restorations can be affected once cemented in the oral cavity by several factors. How can conventional surface treatments, such as glazing and mechanical polishing, diminish the effects of aging? The purpose of this in vitro study was to evaluate the effect of thermocycling and conventional surface treatments on the surface roughness and microhardness of three types of glass-ceramics by using a profilometer, scanning electron microscopy (SEM), atomic force microscopy (AFM), and a microhardness tester. Three types of ceramic systems (zirconia reinforced lithium silicate glass-ceramic, lithium disilicate glass-ceramic, and feldspathic glass-ceramic) (n = 48) were prepared. The samples were subjected to thermocycling for 10,000 cycles. Surface roughness was evaluated numerically using a profilometer and visually by using SEM and AFM. Microhardness was performed using a microhardness tester. The data were interpreted using the ANOVA test, and the results were correlated using Pearson’s correlation formula (r). Significant differences were found before and after thermocycling for the Ra (p < 0.01) and Rz (p < 0.05) parameters. As well, differences between glazed and polished surfaces were significant before and after thermocycling for surface roughness and microhardness (p < 0.05). A correlation was made between average surface roughness and microhardness (r = −460) and for the maximum surface roughness and microhardness (r = −606). Aging increases the roughness and decreases in time the microhardness. The tested ceramic systems behaved differently to the aging and surface treatments. Surface treatments had a significant impact on the microhardness and surface characteristics. The glazed groups were reported with higher surface roughness and lower microhardness when compared to the polished groups before and after thermocycling. The measuring roughness techniques determine the scale-dependent values for the Ra (Sa) and Rz (Sq) parameters. Thermocycling almost doubled the surface roughness for all the tested samples. Microhardness decreased only for the Celtra glazed samples. Nano-roughness increased the values for Vita and slightly for Emax. Thermocycling had little effect on Emax ceramic and a more significant impact on Celtra Press ceramic.

In Vitro Evaluation of the Effect of Different Surface Treatments of a Hybrid Ceramic on the Microtensile Bond Strength to a Luting Resin Cement

Introduction: The aim of the present study was to investigate the effect of different surface treatments of a hybrid ceramic, Vita Enamic, on the micro-tensile bond strength (µ-TBS) to resin cement. Methods: Ten blocks (3×10×8 mm) were retrieved from the original blocks and divided into 5 groups according to the different surface treatments performed: Groups 1: 35% acid phosphoric for 60 seconds (PA); group 2: Sandblasting with 50 µm Al₂ O₃ particles for 10 seconds (SB); groups 3: 9.5% hydrofluoric acid for 60 seconds (HF), group 4: The Er:YAG laser (2 W, 10 Hz) (ER1), group 5: The Er:YAG laser (3 W, 10 Hz) (ER2). All treated surfaces were salinized and the blocks with similar surface treatments were bonded together using a dual-cured resin cement and light-cured. After 24-hour storage in water, the blocks were cut into beams (1 mm²). Half of the specimens in each group (n=16) were tested immediately and the rest were subjected to thermocycling between 5°C and 55°C for 6000 cycles before the µ-TBS test at a crosshead speed of 0.5 mm/min. The data were analyzed using two-way analysis of variance (ANOVA) and Tukey HSD tests and the significance level was set at 0.05. The failure mode was evaluated by using a stereomicroscope. Results: The µ-TBS was clearly influenced by surface treatment methods (P < 0.001) and thermocycling significantly decreased the bond strength values in all groups (P = 0.007). The highest value (66.07 MPa ± 11.3) was obtained for the HF groups with no thermocycling and the lowest values were observed in the laser groups with no significant difference among different irradiation parameters. Adhesive failure was mainly observed in the PA and SB groups while mixed failure was predominantly shown in the laser and HF groups. Conclusion: This study demonstrated that surface treatment of VE with HF and salinization could improve the bond strength to a dual-cured resin cement, and Er:YAG laser irradiation with the evaluated parameters did not promote the adhesion of the resin cement to VE.

The critical bond strength of orthodontic brackets bonded to dental glass-ceramics

OBJECTIVES

To evaluate the critical bond strength (σ) of ceramic and metal brackets to a lithium disilicate-based glass-ceramic.

MATERIALS AND METHODS

Two hundred and forty ceramic specimens (IPS e-max CAD) were randomly distributed in 12 experimental groups (n = 20). Two ceramic brackets (monocrystalline, BCm; and polycrystalline, BCp) and a metal bracket (BM) were bonded to glass-ceramic specimens after one of the following surface treatments: HF-hydrofluoric acid applied for 60 s; S-silane applied for 3 min; HFS-HF followed by S; and MDP-application of an adhesive containing a phosphate monomer (MDP). All brackets were bonded to the treated glass-ceramic using a resin cement, stored in 37 °C water for 48 h before shear bond strength testing. Optical (OM) and scanning electron (SEM) microscopies were used for fractographic analysis. Data was statistically analyzed using Kruskal-Wallis and Student-Newman-Keuls (α = 0.05).

RESULTS

BCm bonded to glass-ceramic treated with either HFS or HF showed the highest median σ values, respectively, 10.5 MPa and 8.5 MPa. In contrast, the BCp bonded to glass-ceramic treated with MDP showed the lowest median σ value (0.8 MPa), which was not statistically different from other MDP-treated groups.

CONCLUSIONS

The failure mode was governed by the glass-ceramic surface treatment, not by the bracket type. Quantitative (σ values) and qualitative (fracture mode) data suggested a minimum of 5 MPa for brackets bonded to glass-ceramic, which is the lower critical limit bond strength for a comprehensive orthodontic treatment.

CLINICAL RELEVANCE

Bonding brackets to glass-ceramic requires micromechanical retention.

Bond strength between composite repair and polymer-infiltrated ceramic-network material: Effect of different surface treatments

OBJECTIVE

To evaluate the bond strength of a polymer-infiltrated ceramic-network (PICN) material and to composite repair after different surface treatments.

MATERIALS AND METHODS

Eighteen blocks of the PICN material were obtained from CAD/CAM blocks, aged and randomly divided into 2 groups: 5% hydrofluoric acid (HF) or sandblasting with aluminum oxide particles (SAND). For each condition, three treatments were tested: silane (Sil), silane-containing adhesive (Ad), or silane + silane-containing adhesive (SilAd). The treated PICN surfaces were restored with composite resin. The microtensile bond strength test was performed in a universal testing machine, and data (MPa) were compared with two-way Analysis of variance (anova) and Tukey (α = 0.05). Roughness (Ra) and contact angle (CA) were obtained after HF and SAND conditions.

RESULTS

The greatest bond strength values were obtained for the groups Sil and SilAd, for both HF and SAND pretreatments. The Ra values of SAND were statistically greater than HF. The CA generated by the adhesive on SAND surface was lower than HF surface.

CONCLUSIONS

The use of silane improves the bond strength of the composite repair to PICN substrate compared to the single use of silane-containing adhesive. The HF pretreatment is most indicated when the silane-containing adhesive is applied alone.

CLINICAL SIGNIFICANCE

Fractured PICN restorations can be repaired with composite resin, because the surface is treated with hydrofluoric acid or sandblasting followed by the individual use of silane.

Shear bond strength of ceramic brackets bonded to surface-treated feldspathic porcelain after thermocycling

Purpose:

The aim of this study was to evaluate the effect of six different surface conditioning methods on the shear bond strength of ceramic brackets bonded to feldspathic porcelain.

Materials and methods:

A total of 60 feldspathic porcelain disks were fabricated and divided into six subgroups including 10 specimens in each. Specimens were first treated one of the following surface conditioning methods, namely, 37% phosphoric acid (G-H3PO4), 9.4% hydrofluoric acid (G-HF), grinding with diamond burs (G-Grinding), Nd:YAG laser (G-Nd:YAG), Airborne-particle abrasion (G-Abrasion). Specimens were also coated with silane without surface treatment for comparison (G-Untreated). A total of 60 ceramic brackets were bonded to porcelain surfaces with a composite resin and then subjected to thermocycling 2500× between 5°C and 55°C. The shear bond strength test was carried out using a universal testing device at a crosshead speed of 0.5 mm/min. Failure types were classified according to the adhesive remnant index. Analysis of variance and Tukey tests were used for statistical analysis (α = 0.05). Microstructure of untreated and surface-treated specimens was investigated by scanning electron microscopy.

Results:

Using G-Abrasion specimens resulted in the highest shear bond strength value of 8.58 MPa for feldspathic porcelain. However, the other specimens showed lower values: G-Grinding (6.51 MPa), G-Nd:YAG laser (3.37 MPa), G-HF (2.71 MPa), G-H3PO4 (1.17 MPa), and G-Untreated (0.93 MPa).

Conclusion:

Airborne-particle abrasion and grinding can be used as surface treatment techniques on the porcelain surface for a durable bond strength. Hydrofluoric acid and phosphoric acid etching methods were not convenient as surface treatment methods for the feldspathic porcelain.

Microshear bond strength of self-adhesive composite to ceramic after mechanical, chemical and laser surface treatments

Objectives

This study aimed to assess the microshear bond strength of a repairing self-adhesive flowable composite to ceramic after mechanical, chemical and laser treatment of the ceramic surface.

Materials and Methods

Forty zirconia and forty feldspathic ceramic blocks measuring 8 x 8 x 2 mm were fabricated. Feldspathic blocks were divided into four groups of control (1), laser (2780 nm) (2), sandblasting + hydrofluoric (HF) acid + silane (3) and laser (2780 nm) + HF acid + silane (4). Zirconia blocks were also divided into four groups of control (1), laser (2780 nm) (2), sandblasting + Z-Prime Plus (3) and laser (2780 nm) + Z-Prime Plus (4). Vertise Flow composite was bonded to treated ceramic surfaces as a repairing material, then the samples were subjected to 1000 thermal cycles. Repair bond strength was measured by Instron machine and data were analyzed using one-way ANOVA and post hoc test (P < 0.05).

Results

Maximum and minimum bond strength values were observed in zirconia-control (22.57 ± 4.76 MPa) and feldspathic-control (8.65 ± 6.41 MPa) groups, respectively. There was no significant differences between subgroups within the zirconia or feldspathic groups (P > 0.05), however the bond strength of zirconia subgroups was significantly higher than that of feldspathic subgroups.

Conclusion

Vertise Flow provides relatively good bond strength to ceramic even with no surface treatment.

Effect of coarse grinding, overglazing, and 2 polishing systems on the flexural strength, surface roughness, and phase transformation of yttrium-stabilized tetragonal zirconia

STATEMENT OF PROBLEM

Limited information is available for the best polishing systems and methods to obtain minimally abrasive monolithic zirconia surfaces after contouring and occlusal adjustment.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of grinding and polishing procedures on the flexural strength, quality and quantity of surface roughness, topography, and phase transformation of a zirconia-based ceramic system.

MATERIAL AND METHODS

Fifty bar-shaped yttrium-stabilized zirconium oxide specimens (20×4×2 mm) were cut from presintered zirconia blanks. The specimens were wet-polished and divided into 5 groups (n=10): standard polishing without any surface treatment (group SP); grinding with a diamond rotary instrument (group Gr); grinding with a diamond rotary instrument (DRI) and over-glazing (group Gl); grinding with a DRI and polishing with an intraoral zirconia polishing kit in a 2-step procedure (group BP); and grinding with a DRI and polishing with an intraoral polishing kit (group MP). The Ra and Rz surface roughness values (μm) were measured with a profilometer. One specimen of each group was subjected to x-ray diffraction (XRD) to estimate the monoclinic phase and evaluated using scanning electron microscopy (SEM) for surface topography. The 3-point flexural strength of the bars was measured in a universal testing machine at a crosshead speed of 0.5 mm/min. The mean flexural strength (MPa) and surface roughness values were calculated, and the results were analyzed using 1-way ANOVA and Tukey honest significant difference tests (α=.05).

RESULTS

Statistically significant differences were noted among the experimental groups for Ra, Rz (P<.001), and flexural strength values (P<.001). The highest Ra and Rz values were found in group Gr (P<.001) and the lowest in group Gl, which were significantly lower than the values in group Gr (P<.001). The 2 polishing systems (BP and MP) were not significantly different in terms of Ra and Rz values (P=.755 for Ra and P=.319 for Rz). The highest flexural strength was found in group Gr (283.35 ±49.85 MPa) without significant differences from those of MP and BP (P=.958 for BP and P=.404 for MP). The lowest flexural strength was found in Gl, which had no significant differences from those of the control group (P=1.000). In XRD the monoclinic phase was observed in Gr (26%), BP (24%), and MP (23%) groups. However, groups Gl and SP did not have any monoclinic phase. SEM showed deep unidirectional scratches after grinding that were smoothened by glazing and polishing.

CONCLUSIONS

Roughness increased significantly after grinding, but polishing and glazing similarly diminished it. Glazing after grinding significantly decreased the flexural strength values, but polishing did not.

Effect of Two Polishing Systems on Surface Roughness, Topography, and Flexural Strength of a Monolithic Lithium Disilicate Ceramic

PURPOSE

To evaluate the effect of overglazing and two polishing procedures on flexural strength and quality and quantity of surface roughness of a monolithic lithium disilicate ceramic computer-aided design (CAD) after grinding.

MATERIALS AND METHODS

This in vitro study was conducted on 52 partially crystalized bar-shaped specimens (16 × 4 × 1.6 mm) of monolithic lithium disilicate ceramic. The specimens were wet polished with 600-, 800-, and 1200-grit silicon carbide papers for 15 seconds using a grinding/polishing machine at a speed of 300 rpm. Then, the specimens were crystalized and glaze-fired in one step simultaneously and randomly divided into four groups of 13: (I) Glazing group (control); (II) Grinding-glazing group, subjected to grinding with red band finishing diamond bur (46 μm) followed by glazing; (III) Grinding-D+Z group, subjected to grinding and then polishing by coarse, medium, and fine diamond rubber points (D+Z); and (IV) Grinding-OptraFine group, subjected to grinding and then polishing with a two-step diamond rubber polishing system followed by a final polishing step with an OptraFine HP brush and diamond polishing paste. The surface roughness (Ra and Rz) values (μm) were measured by a profilometer, and the mean values were compared using one-way ANOVA and Tamhane's test (post hoc comparison). One specimen of each group was evaluated under a scanning electron microscope (SEM) for surface topography. The three-point flexural strength values of the bars were measured using a universal testing machine at a 0.5 mm/min crosshead speed and recorded. The data were analyzed using one-way ANOVA and Tamhane's test (α = 0.05).

RESULTS

Statistically significant differences were noted among the experimental groups for Ra, Rz (p < 0.0001), and flexural strength values (p < 0.009). The lowest Ra and Rz values were found in the grinding-OptraFine group (0.465 ± 0.153), which were significantly lower than those in glazing (p < 0.03) and grinding-glazing (p < 0.001) groups. The Ra and Rz values were not significantly different between the two polishing systems (p = 0.23 and p = 0.25, respectively). The highest flexural strength was found in the glazing group (283.350 ± 49.854 MPa) without significant differences compared to grinding-glazing (p = 0.98) and grinding-OptraFine groups (p = 0.86). The lowest flexural strength was found in grinding-D+Z group (225.070 ± 17.299), which was significantly different from the value in glazing (p < 0.03) and grinding-glazing (p < 0.04) groups. SEM analysis of polished surfaces revealed regular morphology with some striations.

CONCLUSIONS

The OptraFine system created smoother and more uniform surfaces in terms of quantity (p < 0.03 for Ra, p < 0.01 for Rz) and quality of roughness compared to glazing. The flexural strength of lithium disilicate ceramic after polishing with the OptraFine system was similar to that after glazing (p = 0.86). Despite similar surface roughness after polishing with the two systems, the D+Z system reduced the flexural strength of ceramic (p < 0.03).

Surface topography and bond strengths of feldspathic porcelain prepared using various sandblasting pressures

OBJECTIVE

The purpose of this study was to determine the bond strength of composite resin to feldspathic porcelain and its surface topography after sandblasting at different pressures.

METHODS

In this in vitro study, 68 porcelain disks were fabricated and randomly divided into four groups of 17. The porcelain surface in group 1 was etched with hydrofluoric acid. Groups 2, 3, and 4 were sandblasted at 2, 3 and 4 bars pressure, respectively. Surface topography of seven samples in each of the four groups was examined by a scanning electron microscope (SEM). The remaining 40 samples received the same silane agent, bonding agent, and composite resin and they were then subjected to 5000 thermal cycles and evaluated for shear bond strength. Data were analyzed using one-way anova. The mode of failure was determined using stereomicroscope and SEM.

RESULTS

The highest shear bond strength was seen in group 4. however, statistically significant differences were not seen between the groups (P = 0.780). The most common mode of failure was cohesive in porcelain. The SEM showed different patterns of hydrofluoric acid etching and sandblasting.

CONCLUSION

Increasing the sandblasting pressure increased the surface roughness of feldspathic porcelain but no difference in bond strength occurred.

Nd:YAG Laser to obtain Irregularities on the Inner Surface of Porcelain

AIM

The aim of this study was to evaluate the inner surface of two ceramic systems: IPS Empress II (Ivoclar Vivadent, Germany) and In-Ceram Alumina (Vita Zahnfabrick, Germany) submitted to surface treatments, especially by Nd:YAG laser.

MATERIALS AND METHODS

Fifty samples were prepared in pellet form for each ceramic system according to manufacturers' specifications. The samples were stored at room temperature and then be subjected to surface treatment: without treatment (T0) (control), hydrofluoric acid-etched (T1), hydrofluoric acid-etched associated with the airborne particle-abraded (T2); CoJet system (T3), Nd:YAG laser (T4). The data were performed the statistical analysis by ANOVA and Tukey's test (p < 0.001).

RESULTS

The group control (T0) of the ceramics, the analysis showed the lowest roughness values; for the System Alumina In-Ceram, treatment with hydrofluoric acid (T1), associated with hydrofluoric acid and airborne particle-abraded (T2) and Nd:YAG laser (T4), had no statistically significant difference, whereas for the IPS Empress System II treatment with hydrofluoric acid (T1) and hydrofluoric acid associated with airborne particle-abraded (T2), had no statistically significant difference between the system and also CoJet (T3) and hydrofluoric acid associated with the airborne particle-abraded (T2). Photomicrographs of scanning electron microscopy showed different characteristics to the treatments for each ceramic system.

CONCLUSION

The IPS Empress II had the appearance of favoring the retention when treated with hydrofluoric acid, as well as its association with the airborne particle-abraded. Uncertainty in Alumina, treatment with hydrofluoric acid associated with the airborne particle-abraded and CoJet system and provided a surface with irregularities. With respect to the laser further studies should be performed for parameters that are ideal for your application.

CLINICAL RELEVANCE

The ceramic restorations are attractive due of their excellent esthetics and the ability to stay for long periods. However, the retention of ceramic requires further study.