An in vitro study to compare the surface roughness of glazed and chairside polished dental monolithic zirconia using two polishing systems

Evaluation of Surface Roughness of Multilayered Monolithic Zirconia Following Chairside Adjustment with 3 Different Polishing Systems Sterilized for Multiple Cycles: An In Vitro Study

BACKGROUND Chairside grinding, finishing, and polishing are essential for smoothing multilayered monolithic zirconia (MMLZ) restorations. Due to rubber matrix hardening, repeated sterilization of finishing and polishing instruments reduces their abrasive effectiveness. This study aimed to evaluate the effects of sterilization cycles on the effectiveness of 3 commercial polishing kits on the surface roughness of MMLZ crown restorations. MATERIAL AND METHODS One hundred milled, disc-shaped zirconia specimens (10 mm diameter, 3 mm thickness) were divided into 3 groups (n=30) based on the polishing kit used [EVE Diacera, SS White, Ultradent Jiffy]. Each group was further subdivided based on 1, 5, or 10 flash sterilization cycles (n=10). Profilometers measured average surface roughness while objective qualitative analysis was performed by scanning electron microscopy. A one-way ANOVA (Kruskal-Wallis) rank test and a post-hoc Dunn test with Bonferroni correction were used to determine the significance of median values and mean rank scores. The significance threshold for probability 'P' value was set at P≤0.05. RESULTS After 5 autoclaving cycles, the EVE Diacera group had a statistically significant increase in surface roughness (P=0.0009), which decreased somewhat after 10 cycles. The Ultradent Jiffy reduced surface roughness after repeated autoclaving, but SS White did not. Surface roughness did not change across groups after multiple autoclaving cycles, according to post-hoc analysis. CONCLUSIONS MMLZ surface roughness produced by all 3 polishing systems was clinically acceptable after 10 flash sterilization cycles. Ten flash sterilization cycles did not affect the efficiency of any of the polishing systems to produce a smooth surface on the MMLZ specimens.

Polishing of 4Y- and 5Y- zirconia: effects on roughness, color and gloss

OBJECTIVES

To investigate the effects of polishing systems on the roughness, gloss and color of two zirconia materials as a function of the rotational speed and number of polishing movements.

MATERIALS AND METHODS

Specimens (n = 8/group) from 4Y-TZP and 5Y-TZP were milled, diamond grinded and polished. The intraoral polishing varied in the number of polishing steps, the grain size and the matrix. Different number of polishing movements and rotation speed were used. Roughness (ISO25178-2:2021), gloss (ISO2813:2014) and color stability (ISO/CIE 11664-4:2019) were determined.

STATISTICS

Shapiro-Wilk, one-way analysis, Bonferroni, Pearson, variance analysis/intermediate sub-effects (α = 0.05).

RESULTS

Roughness Sa varied between 2.45 ± 0.93 µm and 6.47 ± 0.26 µm (4Y-TZP) and 2.31 ± 0.19 µm and 6.54 ± 0.22 µm (5Y-TZP). Maximum roughness Sz ranged from 32.92 ± 12.59 µm to 99.32 ± 19.87 µm (4Y-TZP) and 31.45 ± 3.02 µm to 90.75 ± 12.59 µm (5Y-TZP). Different gloss from 28.9 ± 4. 23 to 102.39 ± 18.63 GU (4Y-TZP) and 33.19 ± 3.68 to 101.28 ± 10.00 GU (5Y-TZP) was found. ΔE results ranged from 0.39 ± 0.34 to 6.30 ± 1.22 (4Y-TZP) and 0.87 ± 0.71 to 7.50 ± 1.67 (5Y-TZP). Significant (p ≥ 0.095) intermediate sub-effects were found.

CONCLUSIONS

Polishing led to a reduction in roughness, an increase in gloss and a significant change in color. Polishing had a stronger effect on 5Y-TZP.

CLINICAL RELEVANCE

The correct use of the polisher type (stages, binder) and its specific application (rotational speed, movements) can improve roughness, gloss and color variations.

Comparing the effect of two polishing systems on surface roughness of feldspathic, lithium disilicate, and translucent zirconia ceramics after orthodontic bracket debonding: An in vitro study

INTRODUCTION

Debonding of orthodontic brackets on ceramic restorations leave a rough surface which should be efficiently polished. In this study the effect of two diamond polishing systems (DPS), namely Optra Fine® (OF) and Diapol Twist® (DT) on surface roughness (SR) of feldspathic (F), lithium disilicate (LD), and translucent zirconia (TZ) ceramics assessed after bracket debonding.

MATERIALS AND METHODS

Ninety disc-shaped specimens fabricated from F, LD, and TZ ceramics and glazed (Gl). Ten glazed specimens of 3 ceramic types served as control (C) groups (n=30). Other 60 specimens were deglazed, and after specific surface preparation according to ceramic type, upper central incisor brackets were bonded. After debonding, the remaining adhesive composite removed with tungsten carbide bur and specimens randomly assigned into 6 groups. The nine experimental groups defined as: Glazed F specimens (C), Deglazed F specimens polished with DT, Deglazed F specimens polished with OF, Glazed LD specimens (C), Deglazed LD specimens polished with DT, Deglazed LD specimens polished with OF, Glazed TZ specimens (C), Deglazed TZ specimens polished with DT, Deglazed TZ specimens polished with OF. The SR assessed quantitatively by profilometry (Ra and Rz parameter) and qualitatively by scanning electron microscopy (SEM). Quantitative data were statistically analysed using Kolmogorov-Smirnov test, two-way ANOVA and Tukey post-hoc test (α=0.05).

RESULTS

No significant difference found in SR of three glazed ceramic types (P=0.293 for Ra and P=0.473 for Rz). There was no significant difference of Ra between polished and glazed groups (P>0.05). However, difference in Rz was significant (P<0.05), and only TZ specimens could reach to the level of smoothness caused by glazing.

CONCLUSIONS

Both diamond polishing systems can efficiently reduce the surface roughness, despite of ceramic type. Optra Fine® system showed a superior performance than Diapol Twist® without significant difference.

LIMITATIONS

In this study only one brand of each ceramic type was investigated. This study was approved by Ethical Review Committee (IR.IAU.KHUISF.REC.1401.156).

Polishing systems for modern aesthetic dental materials: a narrative review

Objectives To review the current literature surrounding chairside polishing systems for resin composites, zirconia and lithium disilicate restorations.Methods A literature search was undertaken and databases were hand-searched for the most relevant articles.Discussion The current marketplace contains a wide variety of polishing systems, each with different abrasive compounds and number of steps. Current efforts are aimed at reducing the number of steps required for polishing to improve clinical effectiveness. Reduced step systems showed some comparable results to the more traditional multi-step protocols, but the most effective results were achieved with the use of polishing paste as an additional step.Conclusions Based on the current available literature, the use of material-specific polishing systems is effective for chairside polishing of direct and indirect restorative materials. However, it is important to emphasise that, for optimum outcomes, it is essential to follow manufacturers' recommendations for each step, with particular considerations of the handpiece speed, time spent per step and use of adjunct water coolant.

Should finishing, polishing or glazing be performed after grinding YSZ ceramics? A systematic review and meta-analysis

The present systematic review and meta-analysis aimed to assess the characteristics and consequences of post-processing methods after grinding procedures in YSZ ceramics on its surface roughness and flexural strength. The protocol of this review was made prospectively and is available online in the PROSPERO database (link). Literature searches on PubMed/MEDLINE, EMBASE, Lilacs, Web of Science and Scopus were conducted on December 2022 to select in vitro studies written in English, without publishing-date restrictions, that considered surface characteristics and mechanical properties of YSZ ceramics submitted to grinding and subsequent post-processing surface treatments as an attempt to revert the effect induced by grinding. Two authors independently selected the studies, extracted the data and assessed the risk of bias. Mean differences (Rev-Man 5.1, random effects model, α= 0.05) were obtained by comparing flexural strength and surface roughness values of ground surfaces with at least one post-processing surface treatment (global analysis). Subgroup analyses were performed considering the most prevalent categories of post-processing methods. A total of 33 (out of 4032) studies were eligible and included in the analysis. In the global analysis, ground surfaces showed higher flexural strength than when post-processing methodologies were employed (p< 0.0001). The subgroup analysis showed that only polishing was able to enhance the flexural strength after grinding (p= 0.001); however, when other protocols were used, the ground surface was always superior in terms of flexural strength (p< 0.0001). Post-processing techniques in both the global and sub-group analyses were able to reduce the surface roughness after grinding in YSZ ceramics (p< 0.00001). High heterogeneity was found in all the meta-analyses. Concerning the risk of bias analysis, the included studies had mixed scores for the considered factors. In conclusion, in terms of improving flexural strength and restoring surface roughness after grinding, polishing protocols can be considered the best indication as post-processing treatment after YSZ ceramics adjustments/grinding.

Indirect restorative systems-A narrative review

OBJECTIVE

The background and clinical understanding of the properties of currently available indirect restorative systems and fabrication methods is, along with manufacturer and evidence-based literature, an important starting point to guide the clinical selection of materials for tooth and/or implant supported reconstructions. Therefore, this review explores most indirect restorative systems available in the market, especially all-ceramic, along with aspects of manufacturing process, clinical survival rates, and esthetic outcomes.

OVERVIEW

Progressive incorporation of new technologies in the dental field and advancements in materials science have enabled the development/improvement of indirect restorative systems and treatment concepts in oral rehabilitation, resulting in reliable and predictable workflows and successful esthetic and functional outcomes. Indirect restorative systems have evolved from metal ceramics and polymers to glass ceramics, polycrystalline ceramics, and resin-matrix ceramics, aiming to improve not only biological and mechanical properties, but especially the optical properties and esthetic quality of the reconstructions, in attempt to mimic natural teeth.

CONCLUSIONS

Based on several clinical research, materials, and patient-related parameters, a decision tree for the selection of indirect restorative materials was suggested to guide clinicians in the rehabilitation process.

CLINICAL SIGNIFICANCE

The pace of materials development is faster than that of clinical research aimed to support their use. Since no single material provides an ideal solution to every case, professionals must continuously seek information from well designed, long-term clinical trials in order to incorporate or not new materials and technological advancements.

Evaluation of microhardness and water sorption/solubility of dual-cure resin cement through monolithic zirconia in different shades

Aim:

The objective is to evaluate the effect of shades of monolithic zirconia on the microhardness and sorption/solubility of the underlying two dual-cured resin types of cement.

Materials and Methods:

Eighty samples of two dual-cured resin cement discs were polymerized under 60 monolithic zirconia discs in three shades and directly activated resin discs of cement were used as the control group (n = 10). After 24 h storage at 37°C in an incubator, Vickers microhardness and the sorption and solubility were measured.

Statistical Analysis Used:

Two-way ANOVA , one-way ANOVA, Independent t-test, Tukey's honestly significant difference, and Tamhane's T2 tests.

Results:

The mean microhardness of the Variolink N resin cements were significantly higher than Panavia SA ones (P < 0.001). Furthermore, Variolink N cements exhibited lower sorption/solubility than Panavia SA resin cements (both P < 0.05). The ceramic shade had a significant influence on the microhardness of both cements (P < 0.001) but had no significant effect on the sorption/solubility of resin cements (P > 0.05).

Conclusion:

Interposition of monolithic zirconia decreases the microhardness of resin cement especially Panavia SA. In Variolink N, by increasing the chroma saturation of ceramics, the microhardness decreased, however in Panavia SA, it was altered by the shades, but not in a specific pattern. For both cements, there were no statistical differences between the sorption/solubility of samples photo-cured under different shades. There was a reverse correlation between microhardness and water sorption/solubility of both cements.