Effects of storage and toothbrush simulation on color, gloss, and roughness of CAD/CAM, hand-cast, thermoforming, and 3D-printed splint materials

Effect of layer thickness and polishing on wear resistance of additively manufactured occlusal splints

OBJECTIVE

To evaluate the effect of polishing and layering thickness on the wear resistance of 3D-printed occlusal splint materials.

METHODS

Specimens with 3 different layer thicknesses (50, 75, 100 µm) were produced in the form of a disc 3 mm thick using V-Print splint resin on a 3D-printer with digital light processing technology. (n = 16 for each thickness) All specimens were washed and cured according to the manufacturer's instructions. Half of the specimens of each layer thickness were polished with silicon carbide papers. All specimens were subjected to 120.000 cycles of a chewing simulator for 2-body wear tests. Before and after the wear test, the specimens were scanned with a laser scanner, and the images were overlaid using a 3D analysis program and the volume loss was calculated. The wear patterns of the specimens were examined under a scanning electron microscope. Statistical evaluation was performed using a Shapiro-Wilk test, 2-way ANOVA, 1-way ANOVA, and Tukey post hoc test (α = 0.05).

RESULTS

While polishing had a significant effect (p = 0.003) on the wear volume of the occlusal splints, layer thickness (p = 0.105) and their interaction between polishing and layer thickness (p = 0.620) did not significantly affect the wear volume. Regardless of the polishing, the lowest mean wear was observed for D50 (0.064 mm3), followed by D75 (0.078 mm3), and D100 (0.096 mm3). However, a significant difference was observed only between polished D50 and unpolished D100.

CONCLUSION

The polished 3D-printed occlusal splint resin showed higher wear resistance than the unpolished one, regardless of the layer thickness.

CLINICAL SIGNIFICANCE

Since different layer thicknesses of 50 µm and greater had no effect on the wear resistance of the material, a layer thickness of 100 µm may be preferred for faster printing. However, polishing occlusal splints may reduce the amount of wear and improve clinical performance.

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.

Impact of effervescent denture cleaning tablets on color and surface characteristics of additively manufactured and hand-cast splint materials

OBJECTIVES

This study is to evaluate the color stability, surface roughness, and hardness of additively manufactured and hand-cast splint materials after a 6-month commercially available denture cleaning tablet immersion simulation.

MATERIALS AND METHODS

Disc-shaped additively manufactured and hand-cast auto polymerizing acrylic resin specimens were prepared (N = 40 each). All specimens were exposed to coffee solution totally 2 days. Thereafter, all specimens were immersed into three different effervescent solutions that simulated 6 months of clinical use. The total color change (ΔE*ab), surface roughness (Ra), and Vickers hardness (Vh) were measured at baseline and after immersion protocols. A two-way ANOVA and Bonferroni's post hoc test were used for color change. The dependent t-test and ANOVA were used for roughness and hardness evaluation.

RESULTS

Additively manufactured splint materials were more affected by coffee immersion. It was observed that all denture cleaning tablets induced a noticeable alteration in color of the specimens (p < 0.05). Roughness and hardness measurement changes after solution immersions were statistically significant for both splint groups (p < 0.05). On the other hand, distilled water and denture cleaning tablets created similar roughness and hardness measurements at baseline and after immersion.

CONCLUSIONS

After 6 months use of tested cleaning tables, the color stability, surface roughness, and hardness of both groups were affected. The evaluation of the surface properties of splint materials could be recommended to the dentists in periodic controls during splint treatments.

CLINICAL RELEVANCE

The use effervescent denture cleaning tablets altered the surface characteristics of tested splint materials over time with nonsignificant difference between each other. After 6 months, awareness should be raised about surface characteristics of splint materials.

Effects of storage and toothbrush simulation on Martens hardness of CAD/CAM, hand-cast, thermoforming, and 3D-printed splint materials

OBJECTIVES

To investigate Martens hardness parameters of splint materials after storage in liquids and toothbrush simulation.

MATERIALS AND METHODS

Ten specimens per material and group were fabricated (hand-cast CAST, thermoformed TF, CAD/CAM-milled CAM, 3D-printed PS, PL, PK, PV), stored in air, water, coffee, red wine, and cleaning tablets and investigated after fabrication, 24 h, 2- and 4-week storage or toothbrushing. Martens hardness (HM), indentation hardness (HIT), indentation modulus (EIT), the elastic part of indentation work (ηIT), and indentation creep (CIT) were calculated (ISO 14577-1).

STATISTICS

ANOVA, Bonferroni post hoc test, between-subjects effects, Pearson correlation (α = 0.05).

RESULTS

HM varied between 30.8 N/mm2 for PS (water 4 weeks) and 164.0 N/mm2 for CAM (toothbrush). HIT values between 34.9 N/mm2 for PS (water 4 weeks) and 238.9 N/mm2 for CAM (toothbrush) were found. EIT varied between 4.3 kN/mm2 for CAM (toothbrush) and 1.8 kN/mm2 for PK (water 2 weeks). ηIT was found to vary between 16.9% for PS (water 4 weeks) and 42.8% for PL (toothbrush). CIT varied between 2.5% for PL (toothbrush) and 11.4% for PS (water 4 weeks). The highest impact was identified for the material (p ≤ 0.001).

CONCLUSIONS

Storage and toothbrushing influenced Martens parameters. The properties of splints can be influenced by the choice of materials, based on different elastic and viscoelastic parameters. High HM and EIT and low CIT might be beneficial for splint applications.

CLINICAL RELEVANCE

Martens parameters HM, EIT, and CIT might help to evaluate clinically relevant splint properties such as hardness, elasticity, and creep.