Colour stability of a new light-cured ceramic stain system subjected to glazing temperature

A step-by-step technique to create an ideal color match, form, and surface texture to all-ceramic restorations

OBJECTIVES

Although the presence of a chairside CAD/CAM system in the dental office saves time and cost, it deprives the dentist from the dental technologist' skills and experience. The dentist now has to gain and acquire knowledge and skills about how to finish, characterize, stain, and glaze ceramic restorations. The main objectives of this article is to teach novel and reproducible techniques for surface color, texture, glaze and polish for either the chairside or laboratory fabricated indirect ceramic restoration.

CLINICAL CONSIDERATIONS

A protocol for intraoral characterization of monolithic ceramics; the "Triple R" protocol for tooth color mimicking was followed. It consist of three steps: (1) "Recognize" tooth color shapes, (2) "Record" the present color shapes in the patient dentition by drawing a color map for the color shapes extension and determine which luster paste stain to be used for replicating them, and (3) "Replicate" intraorally the recorded color shapes guided by the adjacent natural teeth using low fusing ceramic pastes (shades and stains) for color shape replication. Also, the final touch technique was followed to shape, texture and final surface finish of dental restorations. It is composed of 5 basic levels which we call dental "micro-esthetics that define shape, texture, and surface luster.

CONCLUSIONS

Following the steps of both; the "Triple R" protocol and the "FINAL TOUCH" technique will help to reproduce the final shade of the restoration to create the illusion of a natural tooth to the observer.

CLINICAL SIGNIFICANCE

This article shows how combining two practical methodologies to record and replicate both color shapes and surface texture of natural teeth may extend mimicking, that is, step by step natural tooth shade beyond the limitations of the available commercial shade guides.

Changes in quality of life induced by tooth whitening are not influenced by global self-esteem: a randomized double-blind placebo-controlled trial

The purpose of this paper is to investigate which elements of tooth colour are most influenced by whitening and to identify the short-term changes in satisfaction with smile aesthetics and quality of life induced by tooth whitening and the role of global self-esteem. Sixty participants were randomly assigned to a treated or a placebo group (each group N = 30). Their anterior teeth were bleached with a photo-activated whitening gel, or subjected to a placebo. Lightness, chroma and the translucency of teeth were assessed before and 1 week after the procedure using a spectrophotometer. The Self-Esteem Scale, Psychosocial Impact of Dental Aesthetics Questionnaire, the Orofacial Aesthetic Scale and the Oral Health Impact Profile were administered to subjects. Changes in colour and chroma were greater in the treated than the placebo group (3.8 ± 1.5 vs. 1.7 ± 1.5 and - 3.2 ± 1.5 vs. 0.0 ± 1.1; p < 0.001). The treated group reported increased satisfaction with appearance and a decrease in psychological and social impacts (p < 0.05). In the placebo group there was no objective change in colour but the subjects reported an increase in satisfaction and dental self-confidence, as well as a decrease in psychological impact (p < 0.05). Self-esteem did not have a moderation nor a mediation effect. In conclusion, patients are not able to accurately detect the colour change induced by tooth whitening after 1 week, but they are also largely suggestible when evaluating the changes in quality of life. Changes in quality of life induced by tooth whitening are not influenced by global self-esteem.ClinicalTrials.gov Identifier NCT03380702.

The in vitro and in vivo reproducibility of a video-based digital imaging system for tooth colour measurement

OBJECTIVES

To assess the robustness of a new custom built video-based digital imaging system (VDIS) for measuring tooth colour and whiteness under in vitro and in vivo conditions.

METHODS

The VDIS imaging system was developed for tooth colour measurement and evaluated in vitro and in vivo. The in vitro validation used extracted human teeth (HT, n=14) stored in water and VITA Classical shade guide tabs (SG, n=16). These were measured by the VDIS at baseline, 5min, 2h, 1 week and 2 weeks to evaluate the system repeatability. For in vivo validation, adult volunteers (male/female, n=34) with two natural, unrestored central incisors had their teeth imaged using the VDIS at baseline, 5min and 2h (3 images each) by two different operators to evaluate time and operator effects. Between taking individual images, subjects moved from the imaging-frame to assess the effect of re-positioning on reproducibility. From the in vitro and in vivo images, the average tooth RGB values were obtained, and the CIELAB values and a tooth whiteness index WIO value were calculated. Repeatability and reproducibility of VDIS imaging system was assessed using appropriate repeated measurement analysis techniques and ANOVA.

RESULTS

The measurement variations in vitro were between 1 and 2 units of ΔWIO and the average colour differences were less than 1 ΔE^*_ab unit. For the in vivo study, analysis of the CIELAB parameters and WIO showed that subject variability accounted for between 82 and 99% of the observed variability in the measurement process. The operator variability was less than 0.5% and the overall measurement error was found to be only 0.3% for WIO. Across assessment times the variability was less than 0.5%.

CONCLUSIONS

The dental imaging system V-DIS was shown to be a highly reproducible means for tooth colour and whiteness measurement.

CLINICAL SIGNIFICANCE

Digital imaging based techniques gives a highly reproducible approach to measuring tooth colour.

Color stability of lithium disilicate ceramics after aging and immersion in common beverages

STATEMENT OF PROBLEM

The color of an esthetic restoration and its color stability are important for long-term success. However, the impact of common beverages on lithium disilicate ceramic is not well known.

PURPOSE

The purpose of this in vitro study was to investigate color variations of lithium disilicate ceramics after thermocycling (TC) and immersion in commonly consumed beverages.

MATERIAL AND METHODS

A total of 288 specimens (1×10×10 mm) were fabricated from IPS e-max computer-aided design (CAD) (n=72), IPS e-max CERAM ([CER] n=72), IPS e-max Press with glazing ([PG] n=72), and IPS e-max Press without glazing ([PNG] n=72) according to the manufacturer's instructions. Each group was divided into 4 subgroups (n=18): TC, coffee, black tea, and red wine. Thermocycling was performed at 21 900 cycles at 5°C, 37°C, 55°C, and 37°C (3 years' clinical simulation), whereas the specimens were soaked in the staining solutions for up to 54 hours (3 years' clinical simulation). Color parameters L*, a*, and b* were assessed with an ultraviolet-visible spectroscopy recording spectrophotometer. Color difference (ΔE) was calculated using the equation [ΔΕ= [(ΔL*)² + (Δa*)² + (Δb*)²]½]. Intraexaminer reliability was assessed by using the intraclass correlation coefficient. Two-way analysis of variance was used for the analysis of ΔΕ, and the parameters L*, a*, and b* were analyzed with linear mixed models for repeated measurements and the Bonferroni pair-wise comparison test (α=.05).

RESULTS

Parameters ΔΕ, L*, a*, and b* were significantly affected by the interaction between material and treatment (P<.001). A ΔΕ >1 was recorded for PG with tea, wine, and coffee, PG after TC and CER after TC. For L*, greater reduction was observed for PNG with tea and CER after TC, whereas for a* significant changes were positive (to red shades), except for PNG with TC, where PNG with wine showed the greatest positive change. For b*, significant changes were negative (to blue shades) except for PNG with tea and coffee and CAD with tea.

CONCLUSIONS

All groups demonstrated color changes below the clinically perceptible level (ΔΕ<3.7), except PNG in tea which showed statistically significant color differences (ΔΕ>4). CAD presented higher color stability compared with the nonglazed Press specimens.

Development of polarization dental imaging modality and evaluation of its clinical feasibility

OBJECTIVES

In the evaluation of tooth color, the specular reflection caused by roughness or saliva on the tooth surface may cause artefacts in image analysis. In this study, a polarization dental imaging modality (PDIM) was developed to obtain cross-polarized images and, therefore, to address the problem of specular reflection. Its clinical validity was evaluated by performing 3 studies of shade tab selection for implant, plaque distribution detection, and evaluation of tooth whitening.

METHODS

In vivo human tooth and shade guide color images were obtained, and the minimum color difference between them was calculated for the best color matching shade tab selection. A dental plaque disclosing agent was used to differentiate plaque regions on teeth, and plaque distribution was detected by applying the K-means algorithm. In vivo human teeth were treated with a commercial tooth whitening gel, and tooth whitening was quantitatively evaluated using the PDIM images.

RESULTS

The PDIM produced repeatable glare-free tooth color images by effectively removing the specular reflection from the tooth surface. The cross-polarized tooth images were successfully utilized for shade guide selection, plaque detection, and tooth whitening by minimizing artefacts in the quantitative image analysis. The PDIM could simultaneously provide both qualitative and quantitative assessment of the tooth condition in clinical diagnosis.

CONCLUSIONS

The clinical feasibility of the PDIM was successfully verified in 3 clinical studies by showing its clinical efficacy as a new imaging modality.

Resin cement color stability and its influence on the final shade of all-ceramics

OBJECTIVES

Adhesive resin cements may go through internal discoloration, which may show-through and affect the appearance of translucent all-ceramic restorations. This in vitro study evaluated the amount of resin cement color change and its effect on the final shade of the all-ceramics.

METHODS

Three different resin cements in both light and dual-cure forms were included in the study (Nexus-2/Kerr; Appeal/Ivoclar Vivadent; Calibra/Dentsply). All resin cements contained veneered (IPS Empress Esthetic, ETC1 shade, 20 mm × 1 mm ingot discs) and uncovered groups (n=10/group), all luted on white backgrounds (acetalpolyoxymethylene/Delrin(®)). Curing was performed according to ISO standards with a calibrated LED curing-light (Flashlite 1401). Samples were stored in 37°C distilled water at dark. Spectrophotometric baseline color measurements (Color Eye 7000A) were performed from the samples' top surfaces at 24h (D65 illuminator). Samples were subjected to 65 h of accelerated ageing (Atlas Ci4000). Further color measurements from the same areas were recorded in CIEL*a*b* coordinates where a ΔE data above 3 was accepted as visible discoloration (OptiviewLite-1.9software). Statistical analysis was performed using a nested random effects model and Tukey's post hoc analysis.

RESULTS

Light-cure groups showed better color stability in all three resins but only in Appeal resin cement, the dual-cure group discolored significantly more (p<0.001). More discoloration was recorded on uncovered cement groups that represented the exposed cement at the margins. There was no visible color change (ΔE>3) through the ceramic surface on any veneered group.

CONCLUSIONS

All resin cements showed varying degrees of discoloration after accelerated ageing however their actual color change was partially masked by the ceramic. Dual-cure resin cements may affect aesthetics on restoration margins if directly exposed.

In vitro color stability, stain resistance, and water sorption of four removable gingival flange materials

STATEMENT OF PROBLEM

Evaluation of the color stability of materials used for removable gingival flange prostheses may provide information on their serviceability.

PURPOSE

This in vitro study compared the color stability, stain resistance, and water sorption of 4 materials commonly used for gingival flange prostheses.

MATERIAL AND METHODS

Forty-five cylindrical disks (15 mm in diameter and 10 mm thick) were fabricated out of 1 silicone (Gingivamoll), 1 copolyamide (Flexite Supreme), and 2 heat-polymerized acrylic resins (QC-20 and Vertex). Ten specimens of each material were evaluated by a spectrophotometer after 7, 14, 30, 60, 120, and 180 days of immersion in staining solutions of coffee and tea, whereas specimens placed in water and exposed to air, served as controls. Color differences before staining and after storage periods were assessed. Another 5 specimens of each material were tested for water sorption after 56 days. Data for color change (DeltaE) and weight difference (DeltaW) were analyzed by use of a repeated measures analysis of variance and Scheffe's multiple comparisons (alpha=.05).

RESULTS

The coffee solution produced the highest discoloration value in the silicone material (DeltaE=7.31 +/- 0.57, P<.001), followed by the copolyamide (DeltaE=4.22 +/- 0.40, P<.001), and 2 acrylic resins. In the tea solution, the copolyamide had the greatest staining (DeltaE=2.74 +/- 0.56), whereas the other materials had smaller color changes (P<.001). All investigated materials were relatively color stable (DeltaE < 2) when stored in air and water for 6 months. The copolyamide material showed the greatest water uptake, whereas silicone adsorbed the least water (P<.001).

CONCLUSIONS

All flange materials tested demonstrated color stability in air and water. However, the color changes of silicone and copolyamide materials stored in coffee solution for 180 days were greater than 3 NBS (National Bureau of Standards) units, which would be characterized as appreciable and considered clinically unacceptable.