Staining and bleaching susceptibility of zirconia-reinforced lithium silicate glass-ceramics with different thicknesses, translucencies, and fabrication methods.

STATEMENT OF PROBLEM: The influence of different thicknesses, translucencies, and fabrication methods on the spectrophotometric and topographical properties of zirconia-reinforced lithium silicate glass-ceramics (ZLSs) for dental restorations remains unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of thicknesses, translucencies, and fabrication methods on the color stability, translucency parameter, opalescence parameter, whiteness stability, transmitted irradiance, light transmittance, opacity, gloss, and roughness of ZLSs exposed to coffee staining and bleaching treatments. MATERIAL AND METHODS: Two pressable ZLSs (VITA AMBRIA, VA and Celtra Press, CP) and 2 machinable ZLSs (VITA Suprinity, VS and Celtra Duo, CD) were examined at high translucency (HT) and low translucency (LT) levels in 2 thicknesses (n=160). The specimens were evaluated at baseline, after coffee staining, and after bleaching. The color stability (ΔE2000), translucency parameter (TP), opalescence parameter (OP), whiteness index (WID), and whiteness stability (ΔWID) were measured with a spectrophotometer. Transmitted irradiance (It), light transmission (T), and opacity (O) were obtained from a light-polymerizing unit and a polymerization light collection device. Roughness stability (ΔSa%) was determined with an optical profilometer, and gloss stability (ΔGU%) was recorded with a gloss meter. Data of ΔCIE2000, ΔWID, ΔSa%, and ΔGU% were analyzed by 4-way ANOVA, and data of the TP, OP, WID, It, T, and O were analyzed by repeated 4-way ANOVA (α=.05). RESULTS: VS-HT exceeded the ΔCIE2000 acceptability threshold after coffee staining and bleaching protocols. Pressable ZLSs exhibited greater color stability than machinable ZLSs. The 1-mm-thick VA, CP, and CD materials exceeded the ΔWID perceptibility threshold after bleaching. The highest TP and OP was displayed by the 1-mm-thick CP after bleaching. ΔGU increased after water storage and decreased after coffee staining and bleaching. ΔSa% significantly increased after bleaching (P<.05). CONCLUSIONS: The color stability and other spectrophotometric properties of ZLSs depended on material thickness. The effects of ZLS fabrication methods and translucency levels on their measured properties were inconsistent. Subjecting 1-mm-thick ZLS materials to acidic media adversely impacted their stainability and surface texture.

Microhardness and Gloss of a New CAD/CAM Hybrid Material Following Accelerated Aging and Coffee Immersion.

PURPOSE: To evaluate and compare the effect of accelerated aging and coffee immersion on the microhardness and gloss of a new computer-aided design and computer-aided manufacturing (CAD/CAM) hybrid material (Crystal Ultra) to those of contemporary restorative materials. MATERIALS AND METHODS: A total of 160 specimens (12 × 14 × 1 mm ± 0.05 mm) were obtained from IPS e.max (IPS), VITA Enamic (VE), Crystal Ultra (CU), Lava Ultimate (LU), and CeraSmart (CS) high-translucency CAD/CAM blocks. The Vickers microhardness and gloss of the specimens were determined after thermocycling and coffee immersion. Data analysis was performed using SPSS (α = .05). RESULTS: IPS and CS specimens exhibited the highest (572.66 ± 11.30) and lowest (61.92 ± 3.91) microhardness, respectively. The highest gloss was observed with IPS specimens (3.31 ± 0.32), and LU specimens showed the lowest gloss (2.33 ± 0.06). A significant difference in gloss was observed between the materials at all measurement intervals (P < .01), except at T0 (P = .43). IPS specimens showed no significant changes in either group at any measurement interval. CONCLUSIONS: The microhardness and gloss of the new CU material were comparable to those of the tested contemporary hybrid restorative materials. Glass-ceramic showed superior hardness and gloss compared to hybrid restorative materials. Accelerated aging with thermocycling and staining significantly affected the microhardness and gloss of all tested CAD/CAM materials.

Trueness, Flexural Strength, and Surface Properties of Various Three-Dimensional (3D) Printed Interim Restorative Materials after Accelerated Aging.

Various 3D printing systems for interim fixed dental restorations are commercially available. This study aimed to evaluate the physical and mechanical properties of 3D printed resins used for interim restorations fabricated using various 3D printing systems and printing angulations after accelerated aging. Three different interim restorative materials were provided and printed using their specific 3D printing systems (A: NextDent; B: Asiga; C: Nova3D), and the testing specimens from each system were printed at two building angles: (1) 0° and (2) 90°. The six groups were A1, A2, B1, B2, C1, and C2, with sixteen specimens per group. Half of the specimens in each group (N = 8) were subjected to accelerated aging, including simulated brushing and thermocycling. Three-point bending, surface roughness, and Vickers microhardness tests were performed. Two-way ANOVA and Fisher's multiple tests were used for statistical analyses. The most accurate systems were found in groups C1 and C2 for length, A1 and B1 for width, and A1 and C1 for height. The specimen trueness only changed after aging for groups B1, B2, and C1. The flexural strength of the A2 group (151 ± 7 MPa) before aging was higher than that of the other groups, and the strength decreased after aging only for groups A1 and A2. The flexural strength, microhardness, and surface roughness of the 3D printed interim resins after aging varied depending on the material, system used, and printing angle.

Colour Parameters and Changes of Tea-Stained Resin Composite Exposed to Whitening Pen (In Vitro Study).

BACKGROUND: One of the crucial factors influencing the longevity of anterior aesthetic dental restorations is the colour stability of resin composites. Bleaching and whitening have become popular methods for enhancing dental aesthetics. Home whitening techniques, such as special pens, are widely available commercially. This in vitro study aimed to determine the efficiency of a whitening pen in removing tea stains from resin composite by measuring colour differences (ΔE00). Additionally, the study aimed to evaluate the variations in colour parameters measured by extra-oral and intra-oral spectrophotometers. METHODS: A total of 45 disc-shaped resin composite specimens were randomly divided into three groups; Group 1: stored in artificial saliva (control), Group 2: stored in artificial saliva followed by a whitening pen application, and Group 3: stored in tea followed by a whitening pen application. Colour measurements were taken three times for each specimen using two spectrophotometers (extra-oral and intra-oral devices); T1: before storage (baseline), T2: after storage in artificial saliva or tea for 6 days; and T3: after one week of whitening pen application in groups 2 and 3. The data were statistically analyzed using one-way ANOVA followed by the Tukey post hoc test (p ≤ 0.05). The independent sample t-test was also employed. The equation of CIEDE2000 (ΔE00) was used to calculate the colour difference between the dry, as-prepared specimens (baseline), and those after storage or bleaching. The colour changes exceeding the acceptability threshold (∆E00 = 1.8) were considered unacceptable. RESULTS: After whitening, the colour of the specimens stored in brewed tea (Group 3) remained unacceptable, as indicated by both the extra-oral and intra-oral spectrophotometers (ΔE00 = 4 and 2.9, respectively). Groups 1 and 2 exhibited lower ΔE00 values than Group 3 (p = 0.01 *). No significant difference was observed between Group 1 (stored in artificial saliva) and Group 2 (stored in artificial saliva and then bleached) (p = 0.3). Significant differences were consistently observed between the data obtained from the extra-oral spectrophotometer and the intra-oral one. CONCLUSIONS: The whitening pen proved ineffective in removing tea stains from resin composites. Although significant differences were found between the values obtained by the two spectrophotometers (extra-oral and intra-oral), both devices confirmed the unacceptable colour of the tea-stained resin composites after whitening.

Release and MMP-9 Inhibition Assessment of Dental Adhesive Modified with EGCG-Encapsulated Halloysite Nanotubes.

Degradation of the collagen fibrils at the dentin-resin interface by the enzymatic activity of matrix metalloproteinases (MMPs) has been known to permit some dental restoration complications, such as microleakage, secondary caries, and, ultimately, restoration failures. This study aimed to evaluate a modified adhesive by adding an MMP inhibitor from green tea extract with and without nanotube encapsulation to sustain the drug release. Epigallocatechin-3-gallate (EGCG) and Halloysite nanotubes (HNTs) were prepared to produce three variant combinations of modified adhesive (EGCG, EGCG-encapsulated HNT, and EGCG-free HNT). The drug loading efficiency and EGCG release over time were evaluated using UV-vis spectrometry. MMP-mediated ß-casein (BCN) cleavage rate assays were used to determine the ability of the EGCG in eluates of the adhesive to inhibit MMP-9 activities. For up to 8 weeks, HNT encapsulation reduced release to a statistically significant level. MMP-mediated ß-casein cleavage rate assays showed a significant decrease for the EGCG groups compared to the non-EGCG adhesive groups. Furthermore, the use of HNT for EGCG encapsulation to modify a dental adhesive helped slow down the rate of EGCG release without impacting its MMP inhibitory capabilities, which may help to maintain the dentin-resin interface's integrity over the long term after dental restoration placement.

Microhardness and gloss of a new CAD-CAM hybrid material following accelerated aging and coffee immersion.

PURPOSE: To evaluate and compare the effect of accelerated aging and coffee immersion on the microhardness and gloss of a new CAD/CAM hybrid material (Crystal Ultra) to those of contemporary restorative materials. MATERIALS AND METHODS: A total of 160 specimens (12 x 14 x 1 mm ± 0.05 mm) were obtained from (IPS e.max [IPS], VITA Enamic [VE], Crystal Ultra [CU], Lava Ultimate [LU], and CeraSmart [CS]) high-translucency CAD/CAM blocks. The Vickers microhardness and gloss of the specimens were determined following thermocycling and coffee immersion. Data analysis was performed using SPSS (α = .05). RESULTS: IPS and CS specimens exhibited the highest (572.66 ± 11.30) and lowest (61.92 ± 3.91) microhardness, respectively. The highest gloss was observed with IPS specimens (3.31 ± 0.32), and LU specimens showed the lowest gloss (2.33 ± 0.06). A significant difference in gloss was observed between the materials at all measurement intervals (P < .01), except at T0 (P = .43). IPS specimens showed no significant changes in either group at any measurement interval. CONCLUSION: The microhardness and gloss of the new CU material were comparable to those of the tested contemporary hybrid restorative materials. Glass-ceramic showed superior hardness and gloss compared to hybrid restorative materials. Accelerated aging by thermocycling and staining significantly affected the microhardness and gloss of all the tested CAD/CAM materials.

Influence of Toothbrush Abrasion and Surface Treatments on Roughness and Gloss of Polymer-Infiltrated Ceramics.

The aim of this study was to compare the surface roughness and gloss of polymer-infiltrated ceramics after simulated in vitro toothbrushing in different storage mediums. Four polymer- infiltrated ceramics were evaluated, Lava ultimate (LU), Vita enamic (EN), Shofu (SH), and Crystal ultra (CU). The control group was a feldspathic ceramic, Vita Mark II (VM). One hundred and twenty specimens (12 × 14 × 2.5 mm) were prepared using a precision saw. For each material (n = 24), the specimens were allocated into two groups, polished and stained. The specimens of each group were stored (for 7 days) in either citric acid (0.2N) or distilled water. Data for surface gloss (ΔE*SCE-SCI) and roughness (Ra) were evaluated before (baseline) and after simulated toothbrushing. For toothbrushing simulation, a toothpaste slurry containing a toothpaste of 100 relative dentin abrasion (RDA) and 0.3 ml distilled water was used for 3650 cycles (7300 strokes) for each specimen. Data were analyzed using t-test and ANOVA. A p-value of ≤ to 0.05 was considered significant. The highest mean value of surface gloss was identified in CU (stained-water) (4.3 (0.47)) (ΔE*) and EN (stained-acid) (4.3 (1.00)) (ΔE*) specimens, whereas the lowest mean value was shown by SH (stained-acid) (2.04 (0.42)) (ΔE*) samples. The highest mean value of surface roughness was observed in SH (0.40 (0.99)) Ra (stained-acid) whereas the lowest in VM (0.13 (0.039)) Ra (polished- water). A significant difference (p < 0.05) was observed in surface roughness and gloss between the materials with simulated toothbrushing, except in VM and LU, respectively. Therefore, it can be concluded that simulated toothbrushing impacts on surface roughness and gloss, irrespective of the storage medium.

Influence of toothbrush abrasion and surface treatments on the color and translucency of resin infiltrated hybrid ceramics.

PURPOSE: The study compared the color change, lightness, and translucency of hybrid resin ceramics exposed to toothbrush abrasion and surface treatment. MATERIALS AND METHODS: Four hybrid ceramics [Lava Ultimate (LU), Vita Enamic (EN), Shofu HC (SH), and Crystal Ultra (CU)] were compared with a glass-ceramic (Vita Mark II) control. One hundred and twenty specimen blocks were prepared using a precision saw machine. Specimens in each material were divided into four subgroups based on the surface treatment (polishing or staining) and a storage medium (water or citric acid). Simulated tooth brushing with a mixture of 100 RDA (radioactive abrasives) with 0.3 ml distilled water was used for 3650 cycles (7300 strokes) for each specimen. Measurements for the color change, lightness, and translucency were measured after toothbrushing using a spectrophotometer. Statistical analysis compared outcomes using paired t-test, ANOVA, and Tukey post hoc test. RESULTS: The maximum color change was identified in SH (stained acid) [1.44 (0.40)], whereas the lowest was identified in EN (polished water) [0.66 (0.16)] material. The maximum and minimum loss of surface translucency was observed in SH (polished water) [12.3 (0.52)] and EN (stained acid) [6.5 (0.55)] specimens, respectively. Lastly, loss of lightness was the highest in VM (polished acid) [69 (0.95)], whereas the lowest was observed in CU (stained water) [56.7 (0.86)]. CONCLUSION: The comparison presented a significant effect of toothbrush abrasion on translucency and lightness of the hybrid resin ceramics. Color change was not significantly influenced irrespective of the storage medium employed. Surface staining demonstrated the preservation and stability of color and optical properties under the influence of toothbrush abrasion and chemical trauma.

In Vitro Evaluation of Translucency and Color Stability of CAD/CAM Polymer-Infiltrated Ceramic Materials after Accelerated Aging.

PURPOSE: To investigate and compare the translucency and color stability of a newly introduced polymer-infiltrated ceramic network (PICN) material (Crystal Ultra) to those of clinically well-established restorative materials. MATERIALS AND METHODS: A total of 80 specimens measuring (12 × 14 × 1 mm ± 0.05 mm) were prepared from five CAD/CAM (IPS e.max (IPS), Lava Ultimate (LU), Cerasmart (CS), Vita Enamic (VE), Crystal Ultra (CU)) high translucency (HT) blocks in A2 or equivalent shades. Specimens were randomly allocated into two groups (A and B) (n = 8), and were subjected to 5,000 thermal-cycles (TC). This was followed by one-week immersion of group A specimens in coffee (staining) solution and group B specimens in distilled water. Following immersion, the specimens from both groups were further subjected to 5,000 TC. A spectrophotometer was used to measure the translucency parameter (TP) and color change (ΔE00 ) of the samples using CIELAB color coordinates at baseline, after 5,000 TC, following immersion, and after further 5,000 TC. Color stability was evaluated using the CIEDE2000 formula. Data were analyzed by non-parametric tests (α = 0.05). RESULTS: The TP values of the CAD/CAM materials ranged from 18.0-22.0. Following the initial TC, the changes in TP values were significant for VE (p = 0.012). Coffee immersion and further TC significantly impacted the TP values of PICN (VE and CU) materials compared to glass- ceramics (IPS), and resin nanoceramic (CS and LU) materials (p = 0.012). The comparison between CAD/CAM materials at different intervals showed a significant difference in the TP values (p < 0.01). The materials showed perceptible color changes following the initial TC except for PICN materials which demonstrated acceptable color changes. The major color difference was noticed for the resin nanoceramic specimens immersed in coffee; LU and CS showed higher color changes (ΔE00 = 2.45 and 2.09, respectively) than VE and CU (ΔE00 < 1.8). CONCLUSIONS: The translucency of the newly introduced Crystal Ultra PICN material was low compared to the resin nanoceramics and lithium disilicate glass-ceramic. The Crystal Ultra material exhibited better color stability compared to resin nanoceramics, but higher color change when compared with Vita Enamic PICN and lithium disilicate glass-ceramic CAD/CAM materials.

Effect of ethanol treatment on mechanical properties of heat-polymerized polymethyl methacrylate denture base polymer.

This laboratory study was assessing the nano-mechanical properties (NMP), surface roughness (Sa), and topographic changes caused by ethanol on the surface of heat-polymerized denture base polymers at different time past dough stage. Specimens of heat polymerizing acrylic resin (Interacryl Hot, Interdent, Celje, Slovenia) of size 10×10×3 mm were prepared, wet ground, and polished for uniform smoothness and treated with ethanol in concentrations of 40, 70, and 99.9% for 30, 60, and 120 s and statistical analysis was done. Some statistical significance for Sa were highest with 120 s exposure to 40% ethanol. NMP were the highest for specimens treated with 99.9% ethanol concentration for 120 s, on specimens prepared 30 min past the dough stage. This study suggested that heat-polymerized denture base polymers are prone for changes by ethanol which alters mechanical properties and surface topography. Dough time influenced the ethanol resistance.

Influence of tooth brushing on adhesion strength of orthodontic brackets bonded to porcelain.

BACKGROUND: Adhesive resin composite, which is used to bond orthodontic bracket to tooth surface is exposed to the influence of wear by tooth brushing and wear may influence loosening of the bracket. OBJECTIVE: The aim of this study was to evaluate in vitro the effect of tooth brushing on the adhesion strength of orthodontic brackets bonded to surface treated porcelain. METHOD: A total of 90 glazed porcelain fused to metal facets (PFM) were randomly assigned into 3 groups according to the surface treatment to be received. Group 1 was conditioned with hydrofluoric acid (HF), group 2 conditioned with grit-blasting (GB) and group 3 conditioned with tribochemical silica coating (RC). The groups were evaluated for surface roughness (Ra) before and after surface treatment. Next, 15 samples from each group were subjected to brushing and remaining 15 samples served as the baseline (n=15). Adhesion strength (shear bond strength)was recorded using a universal testing machine. Data collected were analyzed by ANOVA and Tukey's multiple comparison post hoc analysis. RESULTS: Tooth brushing decreased the bond strength in all groups. The highest adhesion strength (baseline and after brushing) was observed in group 3 (26.8 ± 1.77 MPa and 23.57 ± 1.02 MPa) and the lowest was found in group 1 (9.6 ± 1.5 MPa and 5.87 ± 0.77 MPa). Group 3 specimens exhibited the highest Ra (1.24 ± 0.08). CONCLUSION: It was found that tooth brushing of the exposed adhesive resin composite at the bracket-bonding substrate interface lowers the bonding strength regardless of the surface treatment of the substrate.