Color Differences Between Pink Veneering Ceramics and the Human Gingiva

Fifteen ceramic gingival samples: A proposed gingival shade guide

OBJECTIVE

(1) To put forward a set of valid pink ceramic samples for subjective gingival colour selection in the Caucasian population, and (2) to assess the quality of the shade matches provided by the selected pink samples.

METHODS

The ceramic gingival shade samples (n = 133) were obtained by mixing pairs of basic colours from a single system. In each mixture, the proportions of the colours were altered in 10% increments, following the numerical order used by the manufacturers of the three colour systems under study (Heraceram, Vita VM9 and IPS Style). The CIELAB colour coordinates were recorded using spectrophotometry in three zones of healthy anterior gingiva (n = 360). The sample was randomly divided into two subsamples, each of which contained 180 participants. Subsample 1 was used to select the ceramic gingival samples that provided the best shade matches, using the k-means clustering method. Subsample 2 was used to assess the chromatic validity of the selected gingival samples, according to the coverage error.

RESULTS

To identify the ceramic gingival samples that best represented participants' gingival colour, the minimum colour differences (ΔEab∗, ΔE00) between the cluster centroids and the 133 gingival samples were calculated. Fifteen gingival samples were selected: 8 from the Heraceram system, 4 from the VM9 system, and 3 from the IPS Style system. Coverage errors for the 15 gingival samples fell below the gingival clinical acceptability thresholds in the three gingival zones examined.

CONCLUSIONS

The 15 ceramic gingival colour samples provide satisfactory coverage of the gingival colour space, with coverage errors below the ΔE00 clinical acceptability threshold of 2.9 units. These pink colour samples have the potential to provide good gingival shade matches in subjective colour selection.

CLINICAL SIGNIFICANCE

Mixing basic ceramic colours is a viable method for generating a series of pink shades that can be used as a physical gingival shade guide. The resulting guide provides valid results (under the acceptability thresholds) for subjective selection gingival colour selection in clinical practice.

Degree of Standardisation in Ceramic Gingival Systems

No gingival shade guide exists that can be used as a 'gold standard' in gingival shade selection. This research, therefore, aimed to determine whether comparable results in subjective gingival shade selection can be achieved using basic gingival colours produced by distinct manufacturers. It also aimed to explore how coverage of the colour space is affected by mixing these basic colours to create additional shades. To achieve these objectives, the basic gingival colours of three ceramic systems (Heraceram, Kulzer, Madrid, Spain; Vita VM9, Vita Zahnfabrik, Bad Säckingen, Germany; IPS Style, Ivoclar, Schaan, Liechtenstein) were analysed. The colour systems were expanded by creating porcelain gingival samples, whose colours were obtained by mixing the basic colours, altering each mixture by increments of 10%, and respecting the numerical order used by manufacturers to identify the colours. The colour coordinates of the basic and additional colours were recorded using spectrophotometry, and the intra- and inter-system colour differences were calculated using the Euclidean (ΔEab) and CIEDE2000 (ΔE00) formulae. None of the basic colours in the three systems, despite their similar nomenclature, were found to be interchangeable (the colour differences exceeded the gingival acceptability threshold: ΔE00 2.9 units). The expanded gingival colour systems, with mixtures altered by 10% increments, notably increased the gingival colour space covered by the original systems. The authors concluded that there are clear differences between the basic gingival colours produced by distinct manufacturers using the same nomenclature. Ceramic samples produced by mixing basic gingival colours are a resource with the potential to improve subjective gingival shade matching.

Coverage error and shade-match accuracy in three ceramic gingival systems

STATEMENT OF PROBLEM

Research into the coverage error (CE) of gingival systems that have been expanded by using ceramic specimens created by mixing basic colors is lacking.

PURPOSE

The purpose of this in vitro study was to compare the CEs of 3 ceramic gingival color systems that have been expanded with basic-color mixtures from a sample of 360 White participants and to classify the participants according to the accuracy of the shade match achieved with each system.

MATERIAL AND METHODS

L*a*b* color coordinates were recorded in 3 zones of attached gingiva for 360 White participants with healthy gingival tissue (187 men and 173 women). The CEs were calculated for 3 ceramic gingival systems that had been expanded with specimens obtained by mixing the basic colors in consecutive order, the color percentages in each mixture having been altered by 10% increments. The systems were Heraceram (Kulzer GmbH) (n=51); Vita VM9 (Vita-Zahnfabrik) (n=41); and IPS Style (Ivoclar AG) (n=41). The participants were classified into 3 groups according to how well the selected shade matched their gingival color (excellent, acceptable, or poor). The data were analyzed using a 1-way ANOVA with a randomized block design and the homogeneity of proportions test (α=.05).

RESULTS

Statistically significant differences were found between the CEs of the 3 expanded gingival systems in the 3 zones where gingival color was measured (P<.001). The expanded Heraceram system had the smallest CE (ΔE00: minimum 2.66 in the middle zone and maximum 2.95 at the mucogingival line). In the 3 gingival zones, the expanded IPS Style system produced the largest percentage of participants with a poor shade match (ΔE00: minimum 71.4% at the mucogingival line and maximum 75.8% at the free gingival margin), while the expanded Heraceram system had the lowest percentage of participants with a poor shade match (ΔE00: minimum 33.3% in the middle zone and maximum 41.7% at the mucogingival line).

CONCLUSIONS

The CEs calculated for the expanded Vita VM9 and IPS Style ceramic gingival color systems exceeded the clinical acceptability thresholds in the 3 zones examined. According to the ΔE00 formula, the gingival color of at least 33% of participants matched poorly with the expanded systems studied.

Effects of staining and artificial aging on optical properties of gingiva-colored resin-based restorative materials

Objectives

To evaluate CIEDE2000/CIELAB differences in color (ΔE₀₀/ΔE_ab), and translucency parameter (ΔTP₀₀/ΔTP_ab), and gloss of gingiva-colored resin-based restorative materials upon staining/aging.

Materials and methods

Disc-shaped, 10 mm in diameter, and 2-mm-thick samples (n = 5/group) were made from giomer (Beautifil II gingiva), oligomer-based (crea.lign GUM gel), CAD/CAM polymethyl-methacrylate-based (IvoBase CAD), PMMA-based (ProBase Hot), and dimethacrylate-based (SR Nexco Paste Gingiva). Color and gloss were recording using a benchtop spectrophotometer and gloss meter, respectively, at baseline (T0), and upon staining in coffee or red wine for 60 (T1) and 120 h (T2), or artificial aging of 150 kJ/m² (T1) and 300 kJ/m² (T2). Three-way analysis of variance (materials x staining conditions x time intervals), Tukey’s test (α = 0.05), and Pearson’s correlation test were used in analytical statistics.

Results

CIEDE2000 color differences ranged from 1.0 to 4.4 (coffee), 1.5 to 5.3 (wine), and 0.9 to 2.0 after artificial aging, with ΔE₀₀ values being significantly higher for Beautifil than other materials (p < 0.05). ΔTP₀₀ values ranged from 0.2 to 0.7 and were statistically higher upon staining in wine compared to artificial aging (p < 0.05). Gloss values at T0 were 76.7–87.0. Beautifil exhibited the lowest gloss retention (50.8–60.2%) after staining, compared to > 90% of other materials (p < 0.05). ΔE₀₀/ΔE_ab and ΔTP₀₀/ΔTP_ab were positively correlated (p < 0.0001).

Conclusions

Color, translucency, and gloss changes of gingiva-colored restorative materials were material- and staining/aging-dependent. Generally, wine caused greatest changes in color (with IvoBase CAD being the most color stable) and translucency parameter. All materials except Beautifil gingiva II exhibited staining- and aging-dependent gloss retention greater than 90% for all compared time intervals.

Clinical relevance

Optical properties of resin-based gingiva-colored restorative materials depend on material, staining/aging conditions, and exposure time. Certain materials should be avoided in individuals with high consumption of red wine and coffee.

Dental student, dentist, dental assistant, and layperson perception of pink gingival porcelain color

STATEMENT OF PROBLEM

How pink gingival porcelain color is perceived by participants classified according to profession and sex is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the degree of correlation between the ordering of color tabs by participants classified according to profession, years of dental work experience, and sex and the ideal chromatic order based on the color coordinate L∗ (lightness).

MATERIAL AND METHODS

Twenty-one colored specimens made of Heraceram pink gingival porcelain were used. A group of 352 participants (118 men and 234 women) comprised of dental students (n=126), dentists (n=54), dental assistants (n=56), and laypersons (n=116) were enrolled. They were asked to order the specimens starting from the lightest to the darkest. The Kendall coefficients of concordance W and correlation T were used to determine whether the individuals in each experimental group rating the specimens were consistent and accurate.

RESULTS

The degree of agreement between the ideal ordering and that carried out by the participants within the different professional categories was greater than 0.8 in all assessments. No statistically significant differences were found among the groups in relation to professional category, work experience, or sex (P>.05). The Kendall coefficients were higher in the ranking of the darker specimens for all groups of participants.

CONCLUSIONS

No statistically significant differences were found among dentists, dental assistants, dental students, and laypersons in the arrangement of pink porcelain specimens according to their lightness. In addition, in all groups, the darker gingival specimens were ordered significantly better according to their lightness than the lighter specimens.

The reproducibility of electronic color measurements of the marginal gingiva

INTRODUCTION

This study evaluated the reproducibility of electronic color determination system evaluations of the marginal gingiva, which could be important for adhesive cervical fillings or prosthetic restorations that imitate the gingiva.

MATERIAL AND METHODS

In 50 subjects, the L*, a*, and b* color coordinates were evaluated five times at a point in the marginal area of a central incisor using different electronic color determination systems: (SP) Shadepilot, (ES) Easyshade, (CE) Crystaleye, and (SV) X-Rite. The mean color difference (ΔE) and its standard deviation between the five measurements from each participant were calculated separately for each device. Further ICC for interdevice reliability was determined.

RESULTS

The L*, a*, and b* color coordinates and ΔE values differed significantly among the systems (p < 0.001). Within each patient and measurement system, ΔE ranged from 1.4 to 3.2 (SD 1.1-2.5), L* from 2.6 to 5.7 (SD 2.6-5.7), a* from 11.9 to 21.3 (SD 3.6-3.9), and b* from 15.1 to 28.9 (SD 1.7-4.3). Interdevice reliability ranged between 0.675 and 0.807.

CONCLUSIONS

Color determination of the marginal gingiva using the electronic tooth color determination systems tested herein showed limited reproducibility. The results obtained with the different measurement systems differed enormously.

CLINICAL RELEVANCE

These results show that the electronic color measurement devices tested allow no high reproducible determination of color coordinates of the marginal gingiva.