Long-term stainability of interim prosthetic materials in acidic/staining solutions

Comparison of Various Surface Treatment Procedures on the Roughness and Susceptibility to Staining of Provisional Prosthodontic Materials

Esthetically pleasing temporary prostheses are often necessary for extended periods in a variety of clinical scenarios. Adjustments to the occlusion or margins are commonly needed before cementing the temporary prosthesis. Therefore, it is clinically necessary to repolish the rough surface to avoid biological and esthetic issues associated with rough surfaces. The purpose of this in vitro study was to assess and compare the impact of various polishing protocols on the surface roughness and color stability of three resin materials used for provisional crowns. A total of 150 specimens were fabricated from auto-polymerizing polymethyl methacrylate, bis-acryl composite, and Methyl methacrylate-LC resin using a stainless steel mold. Each material group was divided into five groups (n = 10) based on the applied surface treatment: positive control group (G1): no roughening or surface treatment, Negative control group (G2): acrylic bur-roughened surface without any polishing, the different surface treatment groups of silicon carbide and aluminum oxide stone polishing (G3), diamond-coated rubber twist (G4), and Surface Glaze (G5). An optical profilometer was used to assess the surface roughness of all samples. After undergoing 6000 cycles of thermocycling followed by immersion in a coffee solution for 15 days at 37 °C, color parameters were measured using a spectrophotometer both before and after a storage period to evaluate color differences. A two-way ANOVA test with α = 0.05 significance level was carried out to determine the impacts of both the materials utilized and the polishing protocol. Among the three types of resin examined, the bisacryl group exhibited superior surface quality in positive control groups, while PMMA resin demonstrated higher polishability. The diamond-coated rubber twits resulted in lower Ra values of 0.36 (0.01) µm, 0.52 (0.11) µm, and 0.28 (0.05) µm for PMMA, BAMA, and MMLC resins, respectively. The application of photo-polymerized surface glaze led to a plaque accumulation threshold of 0.2 µm across all resin groups. The greatest mean color change occurred in the negative control group, indicating a propensity for more staining on rougher surfaces. The Bisacryl resin exhibited higher ΔE values, whereas PMMA showed better color stability. The lowest ΔE values were found when the surface glaze was applied to all of the provisional crown resins. Untreated Bisacryl resin exhibited the lowest Ra values, while PMMA resins demonstrated superior surface morphology after polishing. PMMA provisional crown resins showed increased resistance to staining. The use of surface glaze enhanced both smoothness and color stability on the surfaces.

Effect of Dietary Simulating Solvents on the CAD-CAM Provisional Restorative Materials' Microhardness and Color Stability Properties: An in vitro Study

Purpose

This in vitro study investigated the effects of dietary solvents on the microhardness and color stability of CAD/CAM provisional restorations compared to conventional materials.

Methods

Disc-shaped specimens (n=200) were fabricated from self-cured acrylic resin, two 3D-printing resins (FormLabs, NextDent), and a milled material (TelioCAD). Randomization assigned specimens (n=10/group) to immersion solutions: artificial saliva, citric acid, heptane, coffee, and tea. Microhardness and color stability were evaluated. One-way and three-way ANOVA with Tukey's post hoc test analyzed the data.

Results

Dietary solvents significantly reduced the surface microhardness of all tested materials (p<0.05). Unpolished surfaces exhibited greater color changes compared to polished ones (p<0.05) across all materials. Coffee and tea induced the most substantial reductions in hardness and the most significant color alterations (p<0.05), whereas saliva and citric acid had minimal effects.

Conclusion

Milled provisional restorations exhibited superior hardness and color stability. Dietary solvents significantly affected material properties over time, highlighting the importance of material selection for clinical applications.

Effect of milling procedures in CAD-CAM systems on the color changes of CAD-CAM polymethyl methacrylate resin material as interim material

PURPOSE

This study aimed to investigate the effects of new and used burs on CAD-CAM PMMA resin color changes following thermocycling.

MATERIALS AND METHODS

Twenty disk-shaped specimens (10 × 2 mm) were made using a single brand of CAD-CAM polymethyl methacrylate resin (Polident) for the color test. Group N consisted of half of the specimens that were machined using the new tungsten carbide bur set, and Group U consisted of the specimens that were milled using the used bur set (500 machining time). A color test was performed on the specimens both before and after thermocycling. For the statistical analysis, the Kruskal-Wallis and Dunn Pairwise Comparison tests were employed.

RESULTS

The ∆E* value of specimens (2.057) milled with the used bur was higher than those of specimens milled with the new bur (0.340), but this value is within clinically acceptable limits. After thermocycling, specimens milled with the utilized burs had the greatest L* (93.850) and b* (5.000) values. After thermocycling, statistically significant differences were discovered between Group N and Group U as well as between specimens milled with the utilized bur before and after thermocycling.

CONCLUSION

Thermocycling process have an effect on the mean ∆E values of specimens milled with the used carbide bur, but these ∆E* values were not statistically significant.

CLINICAL SIGNIFICANCE

The color and clinical performance of CAD-CAM restorations may be affected by variations in CAD-CAM milling bur properties, particularly those related to their frequent use.

Comparison of fracture strength, surface hardness, and color stain of conventionally fabricated, 3D printed, and CAD-CAM milled interim prosthodontic materials after thermocycling

PURPOSE

The purpose of this in vitro study was to investigate the fracture resistance, surface hardness, and color stain of 3D printed, CAD-CAM milled, and conventional interim materials.

MATERIALS AND METHODS

A total of 80 specimens were fabricated from auto polymerizing polymethyl methacrylate (PMMA), bis-acryl composite resin, CAD-CAM polymethyl methacrylate resin (milled), and 3D printed composite resin (printed) (n = 20). Forty of them were crown-shaped, on which fracture strength test was performed (n = 10). The others were disc-shaped specimens (10 mm × 2 mm) and divided into two groups for surface hardness and color stainability tests before and after thermal cycling in coffee solution (n = 10). Color parameters were measured with a spectrophotometer before and after each storage period, and color differences (CIEDE2000 [DE00]) were calculated. The distribution of variables was measured with the Kolmogorov Smirnov test, and one-way analysis of variance (ANOVA), Tukey HSD, Kruskal-Wallis, Mann-Whitney U tests were used in the analysis of quantitative independent data. Paired sample t-test was used in the analysis of dependent quantitative data (P < .05).

RESULTS

The highest crown fracture resistance values were determined for the 3D printed composite resin (P < .05), and the lowest were observed in the bis-acryl composite resin (P < .05). Before and after thermal cycling, increase in mean hardness values were observed only in 3D printed composite resin (P < .05) and the highest ΔE00 value were observed in PMMA resin for all materials (P < .05).

CONCLUSION

3D printing and CAD-CAM milled interim materials showed better fracture strength. After the coffee thermal cycle, the highest surface hardness value was again found in 3D printing and CAD-CAM milled interim samples and the color change of the bis-acryl resin-based samples and the additive production technique was higher than the PMMA resin and CAD-CAM milled resin samples.

Color and surface stainability of additively and subtractively manufactured interim restorative materials against mouth rinses

STATEMENT OF PROBLEM

Interim restorations are often used along with mouth rinses during the healing period following surgical procedures. However, evidence regarding the color and surface properties of digitally fabricated interim restorations after oral rinsing is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate whether different mouth rinses could affect the color and surface roughness of milled and printed interim restorations after simulated oral rinsing.

MATERIAL AND METHODS

Disk-shaped specimens (Ø15×2 mm; N=180) were fabricated by using conventional (Jet Tooth Shade), milled (Yamahachi PMMA Disk), and printed (NextDent C&B) resin materials. All resin specimens were divided into 3 different groups according to the rinsing material: distilled water, whitening mouth rinse (Listerine Healthy White), and conventional mouth rinse (Listerine Cool Mint). The specimens were further allocated into short- and long-term subgroups, and oral rinsing simulation was performed (n=10). Short-term rinsing simulated the conditions in a usual interim restoration period, and long-term rinsing was performed to evaluate the properties of the interim materials. The color differences (CIEDE2000, ΔE00) between the baseline and each time point were determined by using a spectrophotometer. The surface roughness of the tested specimens was measured by using a confocal laser scanning microscope. Kruskal-Wallis and Friedman tests with nonparametric pairwise comparisons were used to analyze the data (α=.05).

RESULTS

On simulation of a 6-month use of the mouth rinse, the color change in the milled resin did not differ from that in the conventional resin (P>.334), but the printed resin showed a significantly greater color change than the other resins (P<.007). The greatest color change with the printed resin was observed when a conventional mouth rinse was used. However, all color changes were below a perceptible threshold of 1.30. When daily rinsing for 14 years was simulated, all resin groups showed a perceptible color change when conventional mouth rinse was used, and the printed resin showed the greatest median ±interquartile range ΔE00 (2.24 ±0.2). In both short- and long-term simulations, the printed resin rinsed with the conventional mouth rinse showed significantly greater roughness than that rinsed with distilled water (P<.009).

CONCLUSIONS

The printed resin showed higher stainability than the conventional resin, and the color change was greatest with the conventional mouth rinse. However, in 6 months of daily mouth rinse simulation, all the tested resin materials exhibited imperceptible color change and clinically acceptable surface roughness.

Comparison of the color stability and surface roughness of 3-unit provisional fixed partial dentures fabricated by milling, conventional and different 3D printing fabrication techniques

OBJECTIVES

To compare the color stability and surface roughness of 3-unit provisional fixed partial dentures (FPDs) fabricated by milling, conventional, and different 3D printing fabrication techniques.

METHODS

A total sample of 160, 3-unit FPDs were subdivided into four groups; subtractive milled resin (SM), two 3D printed resins (Stereolithography; SLA and Digital Light Processing; DLP) and conventional self-cured polymethyl methacrylate resin (CM). Surface roughness (Ra) was assessed twice; at baseline (Ra1) and after artificial tooth brushing (Ra2). Color of the samples was measured after immersion in four different solutions (cola, coffee, black tea and distilled water) at three time intervals (1, 7 and 30 days). Comparisons of the Ra and the color change (∆E₀₀) were done using one-way ANOVA followed by multiple pairwise comparisons using Bonferroni adjusted significance level. Comparisons of the Ra at two stages (Ra1 and Ra2) were done using paired t-test. Univariate linear regression was performed followed by multivariable regression to assess the association between ∆E₀₀ and different factors (materials, solution, and time). Significance was set at P value <0.05.

RESULTS

The highest change in Ra following artificial tooth brushing was reported in the CM group, while the lowest change was reported in the SM group, with a significant difference between both groups (P<0.001). SM group had significantly lower ∆E₀₀ than the CM group followed by 3D printed SLA and DLP groups (P<0.001). Storage in coffee for 30 days showed the highest ∆E₀₀ values (P<0.001).

CONCLUSIONS

SM resin showed the least surface roughness and color change followed by 3D printed SLA resin. The difference in printing technology affected the tested properties with improved readings of 3D printed SLA resin.

CLINICAL SIGNIFICANCE

Milled provisional FPDs showed higher surface smoothness and color stability than those fabricated by SLA printing technology, but with no significant difference between both groups. Therefore, SLA printed resins can be an adequate substitute to milled resins in the fabrication of provisional FPDs to overcome the high expenses of milled provisional FPDs.

Comparison of surface roughness and color stainability of 3-dimensionally printed interim prosthodontic material with conventionally fabricated and CAD-CAM milled materials

STATEMENT OF PROBLEM

Studies on the surface roughness and color stainability of interim prostheses produced with 3-dimensional-printing technology are lacking.

PURPOSE

The purpose of this in vitro study was to investigate the effect of different surface treatments on the surface roughness and stainability of 3-dimensionally printed, computer-aided design and computer-aided manufacturing (CAD-CAM) milled and conventional interim materials.

MATERIAL AND METHODS

A total of 320 specimens were fabricated from autopolymerizing polymethyl methacrylate, bis-acryl composite resin, CAD-CAM polymethyl methacrylate resin (milled), and 3-dimensionally printed composite resin (printed) (n=80). A group of each material was divided into 2 groups (n=40) as per the applied surface treatment procedure: conventional polishing (C) or coated with a surface sealant (B). Surface roughness values were measured with a profilometer. Each group of specimens was then divided into 4 subgroups (n=10) and stored for 1 day, 7 days, and 30 days at 37 °C in different solutions: distilled water, cola, coffee, and red wine. Color parameters were measured with a spectrophotometer before and after each storage period, and color differences (CIEDE2000 [ΔE₀₀]) were calculated. Data were statistically analyzed with the Shapiro-Wilk test, Kruskal-Wallis test, and Mann-Whitney U test followed by the Friedman test (α=.05).

RESULTS

The highest surface roughness values were determined for the polymethyl methacrylate -C, and the lowest were observed in the printed-B. After 30 days, the highest mean ΔE₀₀ values were observed in polymethyl methacrylate-C for all staining solutions (P=.001). The highest ΔE₀₀ for all materials was observed in the red wine group. Color change increased significantly with storage duration (P=.001).

CONCLUSIONS

All tested materials had a surface roughness higher than the plaque accumulation threshold (0.2 μm). The surface roughness values of coated materials were significantly lower than those of their conventionally polished groups, except for the printed groups. The application of a surface sealant agent significantly decreased the staining of the materials.

Effect of acidic beverages on surface roughness and color stability of artificial teeth and acrylic resin

PURPOSE

The aim was to evaluate the effect of four acidic beverages on the roughness (Ra) and color change (ΔE_ab) of two brands of artificial teeth and a heat-polymerized acrylic resin (HPAR) for use in a prosthetic base.

MATERIALS AND METHODS

All materials were divided into 5 groups, according to the used acidic beverage (artificial saliva - control, red wine, orange juice, coke-based, and lemon juice-based soft drink). The immersion process was divided into two stages: T1 - immersion in the acidic solutions for 10 minutes for 14 days; T2 - after T1, the samples were immersed in grape juice for 14 days. The Ra of the samples was evaluated in a rugosimeter and the ΔE_ab in a spectrophotometer, before and after the immersions. The analysis of variance of one (ΔE_ab) and two factors (Ra) and Tukey were performed (α=.05).

RESULTS

There was a statistical difference for roughness after immersion (T1) for Trilux and Tritone teeth, regardless of the acid solution. For Trilux teeth, all acid solutions increased Ra (P<.05). For Tritone teeth, only the coke-based soft drink did not statistically change Ra. Grape juice (T2) altered Ra only of artificial teeth (P<.05). The color was changed for all materials, after T1 and T2.

CONCLUSION

In general, the acidic solutions changed the Ra and ΔE_ab of HPAR and artificial teeth after T1. The grape juice altered the roughness only of the artificial teeth, promoting a clinically acceptable color change in the materials.