Evaluation of the surface roughness in dental ceramics submitted to different finishing and polishing methods

Influence of Surface Type with Coffee Immersion on Surface Topography and Optical and Mechanical Properties of Selected Ceramic Materials

BACKGROUND The aim of this study was to assess and compare the effect of surface type (glazed or polished) with coffee immersion and aging on surface topography (Ra), optical properties (TP, OP), and mechanical properties (fracture forces and modes) of zirconia-reinforced lithium silicate (Vita Suprinity), hybrid polymer-infiltrated-feldspathic ceramic network material (Vita Enamic), and leucite-containing feldspathic glass (Vitablocs® Mark II) made by computer-aided design and computer-aided manufactured (CAD/CAM) ceramic materials. MATERIAL AND METHODS Fifty-four specimens were assembled out of the above 3 CAD/CAMs ceramic materials. Each group was divided into glazed or polished surfaces, having 9 specimens of every type and stained in coffee for 15 days. Ra and color of specimens in the form of TP and OP were recorded before and after immersion in staining material. Fracture forces and modes were analyzed after the 90-day aging. Data were analyzed using ANOVA, then post hoc analysis and Bonferroni tests. RESULTS Our study found significant differences in Ra, TP, and Op before and after coffee immersion between glazed and polished specimens, with higher values in the polished surfaces among the 3 ceramic materials. The highest values of fracture resistance were noted in Vita Suprinity, and Vita Enamic had the lowest values, without significant differences among groups. CONCLUSIONS Most of the TP and OP values were in acceptable clinical range, and Vita Suprinity had superior TP than the other groups. Reparable fracture types were observed in Vita Suprinity, whereas semi-reparable and non-reparable were predominant in other groups.

The Effect of Smoking and Brushing on the Color Stability and Stainability of Different CAD/CAM Restorative Materials

This study aimed to investigate and compare the color stability and stainability of computer-aided design/computer-aided manufacturing (CAD/CAM) restorative materials in their glazed (G) and polished (P) state when exposed to cigarette smoke, as well as after brushing. Three CAD/CAM restorative materials were investigated: lithium disilicate CAD (LD), zirconia (Zr), and Telio PMMA CAD (PMMA), according to their surface finishing and assignment to cigarette smoking exposure or soaking in the saliva (control) group. The color change (∆E) was calculated before and after the intervention performed for all specimens, using the L*a*b values to quantitatively assess the shade differences. Statistical analysis was performed using one-way repeated measures ANOVA and Bonferroni multiple comparison analysis (α = 0.05). The surface finishing did not influence the materials’ stainability. Color change was noted after smoking, LD and Zr-G and Zr-P had a comparable color change (p > 0.05), while PMMA presented lower ∆E values (p < 0.05). After brushing, all specimens had a significant color change that was high for LD-G and LD-P, and Zr-G, compared with Zr-P and PMMA (p < 0.05). In conclusion, the exposure to cigarette smoke showed that LD, Zr, and PMMA are all susceptible to staining, but brushing decreases surface staining.

An In vitro Evaluation to Compare the Surface Roughness of Glazed, Reglazed and Chair Side Polished Surfaces of Dental Porcelain

Aim:

The aim of this study was to evaluate the effect of glazing, reglazing, and chairside polishing on the surface roughness of dental porcelain.

Materials and Methods:

A total of 50 discs of feldspathic porcelain were fabricated using a metal mold of dimension 10 mm × 2 mm. Based on the surface treatment, the samples were divided into five groups. Group A – Glazed (control), Group B – Abraded and reglazed, Group C – Abraded and polished with porcelain adjustment kit (Shofu Dental Corp. PN 0301 Classic Plastic HP Kit, Shofu Inc., Kyoto, Japan), Group D – Abraded and polished with diamond polishing paste (Shofu Dental Corp. PN 0558 DirectDia, Shofu Inc., Kyoto, Japan), Group E-Abraded and polished with the combination of porcelain adjustment kit followed by diamond polishing paste. The surface roughness (Ra) values (μm) were evaluated by a profilometer (Mitutoyo Surftest SJ-310, Tokyo, Japan). The data obtained were statistically analyzed using one-way ANOVA and post hoc Tukey's test.

Results:

The mean surface roughness (Ra) of Groups A, B, C, D, and E was 0.567 ± 0.078 μm, 0.433 ± 0.059 μm, 0.882 ± 0.126 μm, 2.361 ± 0.195 μm, and 0.438 ± 0.043 μm, respectively. The samples of Group D (Polished with polishing paste alone) had the highest surface roughness (Ra value). Whereas the samples of Group B and E had similar surface roughness (Ra) value. Differences between Groups A, B, and E were statistically insignificant (P > 0.05).

Conclusion:

After adjustment of ceramic restorations in dental clinics, diamond polishing paste, when used after porcelain adjustment kit, could provide the marked finish equal to glazed or reglazed surface.

Effect of Printing Parameters on Dimensional Error and Surface Roughness Obtained in Direct Ink Writing (DIW) Processes

Prostheses made from ceramic materials have the advantages of producing little debris and having good durability, compared with those made from metal and plastic. For example, hip prostheses require a porous external area that allows their fixation by means of osseointegration and a solid internal area that will be in contact with the femoral head. The manufacturing of complex ceramic shapes, by means of machining processes, for example, is complicated and can lead to breakage of the parts because of their fragility. The direct ink writing (DIW) process allows the printing of ceramic pastes into complex shapes that achieve their final strength after a heat treatment operation. This paper studies both the dimensional error and surface finish of porous zirconia prismatic parts prior to sintering. The variables considered are infill, layer height, printing speed, extrusion multiplier and bed temperature. The responses are the dimensional error of the lateral walls of the samples and an areal roughness parameter, the arithmetical mean height, Sa. Mathematical models are found for each response, and multiobjective optimization is carried out by means of the desirability function. The dimensional error depends mainly on the interaction between layer height and infill, while the roughness on the interaction between infill and printing speed. Thus, infill is an important factor for both responses. In the future, the behavior of compact printed parts will be addressed.

Effect of Thermocycling, Surface Treatments and Microstructure on the Optical Properties and Roughness of CAD-CAM and Heat-Pressed Glass Ceramics

Dental ceramic restorations are widely spread nowadays due to their aesthetics and biocompatibility. In time, the colour and structure of these ceramic materials can be altered by aging processes. How does artificial aging affect the optical and surface roughness of ceramics? This study aims to assess the effect of thermocycling, surface treatments and microstructure upon translucency, opalescence and surface roughness on CAD-CAM and heat-pressed glass-ceramic. Forty-eight samples (1.5 mm thickness) were fabricated from six types of A2 MT ceramic: heat-pressed and milled glass-ceramic (feldspathic, lithium disilicate and zirconia reinforced lithium silicate). The samples were obtained respecting the manufacturer’s instructions. The resulted surfaces (n = 96) were half glazed and half polished. The samples were subjected to thermocycling (10,000 cycles) and roughness values (Ra and Rz), colour coordinates (L*, a*, b*) and microstructural analyses were assessed before and after thermocycling. Translucency (TP) and opalescence (OP) were calculated. Values were statistically analysed using ANOVA test (one way). TP and OP values were significantly different between heat-pressed and milled ceramics before and also after thermocycling (p < 0.001). Surface treatments (glazing and polishing) had a significant effect on TP and OP and surface roughness (p < 0.05). The heat-pressed and milled zirconia reinforced lithium silicate glass-ceramic experienced a loss in TP and OP. Ra and Rz increased for the glazed samples, TP and OP decreased for all the samples after thermocycling. Microstructural analyse revealed that glazed surfaces were more affected by the thermocycling and especially for the zirconia reinforced lithium silicate ceramic. Optical properties and surface roughness of the chosen ceramic materials were affected by thermocycling, surface treatments and microstructural differences. The least affected of the ceramics was the lithium disilicate ceramic heat-pressed polished and glazed.

Two-body wear behavior of human enamel versus monolithic zirconia, lithium disilicate, ceramometal and composite resin

PURPOSE

To investigate and compare the surface roughness (SR), weight and height of monolithic zirconia (MZ), ceramometal (CM), lithium disilicate glass ceramic (LD), composite resin (CR), and their antagonistic human teeth enamel.

MATERIALS AND METHODS

32 disc shaped specimens for the four test materials (n=8) and 32 premolars were prepared and randomly divided. SR, weight and height of the materials and the antagonist enamel were recorded before and after subjecting the specimens to 240,000 wear-cycles (49 N/0.8 Hz/5℃/50℃). SR, height, weight, and digital microscopic qualitative evaluation were measured.

RESULTS

CM (0.23 + 0.08 µm) and LD (0.68 + 0.16 µm) exhibited the least and highest mean difference in the SR, respectively. ANOVA revealed significance (P=.001) between the materials for the SR. Paired T-Test showed significance (P<.05) for the pre- and post-SR for all the materials. For the antagonistic enamel, no significance (P=.987) was found between the groups. However, the pre- and post-SR values of all the enamel groups were significant (P<.05). Wear cycles had significant effect on enamel weight loss against all the materials (P<.05). CR and MZ showed the lowest and highest height loss of 0.14 mm and 0.46 mm, respectively.

CONCLUSION

MZ and CM are more resistant to SR against the enamel than LD and CR. Enamel worn against test materials showed similar SR. Significant variations in SR values for the tested materials (MZ, LD, CM, and CR) against the enamel were found. Wear simulation significantly affected the enamel weight loss against all the materials, and enamel antagonist against MZ and CM showed more height loss.

Effect of different polishing methods on surface roughness of provisional prosthetic materials

Purpose:

To evaluate the surface roughness of bis-acrylic and acrylic resins submitted to different methods of polishing.

Materials and Methods:

Fifty samples of each provisional restorative material (Structur 2, Protemp 4, Duralay, and Dencrilay) were fabricated (10 mm × 2 mm) and divided into five groups (n = 10): (1) positive control group – polyester strip; (2) negative control – unpolished; (3) abrasive tips (Exa-Technique-Edenta); (4) goat hair brush and diamond polishing paste; and (5) silicone tips (Enhance). Each material was mixed and polymerized according to manufacturer's instructions. The parameter evaluated was the arithmetic mean of the surface roughness (Ra) determined using the rugosimeter SJ 301 (Mitutoyo, Japan). The data were analyzed with two-way analysis of variance (post hoc Tukey's test) (P < 0.05).

Results:

The lowest surface roughness values (0,22–0,90 μm) were observed in the Group 4 – goat hair brush and diamond paste, while the highest values (1,17–1,44 μm) were found in the Group 5 – silicone tips (enhance), with statistically significant differences between them, except for Dencrilay acrylic resin. There was statistically significant difference between bis-acrylic and acrylic resins in the Groups 1, 2, and 4.

Conclusions:

Within the limitations of this study, it was concluded that the most effective polishing system was the goat hair brush with diamond paste for both bis-acrylic and acrylic resins. The bis-acrylic resins exhibited significantly smoother surfaces than the acrylic resins.

The Effect of Different Polishing Methods and Storage Media on Discoloration of Resin Composites

STATEMENT OF PROBLEM

Accumulation of plaque and staining due to a rough surface, and penetration of colourant agents from food and beverages in to the resin composite results in an incomplete polymerization. There is a little information on the effect of finishing and polishing techniques on the discoloration of nanohybrid and microhybrid composites when exposed to staining solutions.

OBJECTIVES

To determine the degree of surface staining of nanohybrid and microhybrid composites after polishing and immersion in distilled water and two commonly used staining solutions.

MATERIALS AND METHODS

A nanohybrid (Ice; SDI) and microhybrid (Gradis direct; GC) composites were used. Disc-shaped specimens were prepared and treated with either a matrix finish or polished using Sof-Lex discs (3M/ ESPE) and Enhance point (Dentsply). After 24 h immersion in distilled water at 37°C the specimens were polished and colour coefficients (CIE L* a* b*) was measured by a spectrophotometer. All specimens were immersed in 37°C distilled water in an incubator for 7 days and colour coefficients were measured again. The colour change (ΔE) was calculated using the following formula: ΔE = [(Δa)²+(Δb)²+(ΔL)²] ^1/2. The data were analyzed using three-way ANOVA, one-way ANOVA/Tukey HSD and Student's t-test.

RESULTS

There was a significant interaction between resin composites, polishing systems and staining solutions (p < 0. 05). ANOVA and Tukey's tests showed that Ice had a significantly lesser colour change than Gradia direct and matrix finish revealed the smoothest surface followed by Sof-Lex discs and Enhance point. Distilled water and cola caused no perceptible colour change (ΔE < 3.3). The effect of surface polish on staining was statistically significant (p < 0 .05).

CONCLUSIONS

Sof-Lex discs in comparison to Enhance point stimulated greater staining resistance for both composites. The nanohybrid exhibited less colour change than microhybrid composite. Coffee was the only storage media that induced a perceptible colour change (ΔE > 3.3) compared to cola and distilled water.