Tooth colour : a review of the literature

https://www.dentalxp.com/content/1863/8c629565-70a7-4c79-97a3-86b5e7206825.pdf

Dental color matching instruments and systems. Review of clinical and research aspects

Statement of problem There is little agreement in the dental literature as to how much color difference constitutes an acceptable shade mismatch or how much color difference is considered perceivable to observers. Most studies attempting to determine perceptibility and acceptability of tolerances for shade mismatches have been conducted under in vitro conditions that are not applicable to clinical scenarios. Purpose The goal of this study was to determine valid acceptability and perceptibility tolerances for shade mismatch in an actual clinical scenario using spectroradiometric instrumentation. Material and methods A test denture was fabricated that allowed 10 maxillary left central incisors of varying shade mismatch with the right central incisor to be interchanged within the denture base. A spectroradiometer was used to determine the CIELAB coordinates and color differences (ΔE) between the right central incisor and the interchangeable left central incisor denture teeth. The interchangeable denture teeth ranged uniformly from 1 ΔE unit (visually undetectable) to greater than 10 ΔE units (an obvious shade mismatch). The test denture with each of the interchangeable teeth was modeled by a subject to 28 dentists in a clinical setting. For each of the interchangeable teeth, dentist observers were asked if they could see a difference between the central incisors and, if so, whether the difference was acceptable. A Probit regression analysis was used to predict acceptability and perceptibility tolerances with 95% confidence limits. Results The predicted color difference at which 50% of the dentist observers could perceive a color difference (50/50 perceptibility) was 2.6 ΔE units. The predicted color difference at which 50% of the subjects would remake the restoration due to color mismatch (clinically unacceptable color match) was 5.5 ΔE. Acceptability and perceptibility color tolerances at the 50/50 level were significantly different ( P Conclusions Tolerances for perceptibility were significantly lower than tolerances for acceptability for shade mismatch between 2 denture teeth.

Intraoral determination of the tolerance of dentists for perceptibility and acceptability of shade mismatch.

Statement of problem The ability of tooth-colored restorative materials for provisional restorations to resist stains is important when interim prostheses are worn for a long period. Discoloration of provisional restorative materials may result in patient dissatisfaction and additional time and expense for replacement. However, the effect of different staining agents on the color difference of resin composite restorative materials has not been completely clarified. Purpose The purpose of this study was to evaluate the stainability of auto- and light-polymerized composite provisional restorative materials, reinforced microfill, and microhybrid resin composite restorative materials upon exposure to different staining agents. Material and methods Forty-five cylindrical specimens (15 × 2 mm) were prepared for each of an autopolymerized bis-acryl composite provisional restorative material (Protemp II), a light-polymerized composite provisional restorative material (Revotek LC), a reinforced microfill (Micronew), and a microhybrid composite (Filtek Z250, Herculite XRV) restorative material, using a brass mold. The specimens were wet-ground with 1000-grit silicon carbide abrasive paper for 10 seconds. The 5 restorative material specimens were divided into 9 groups (n=5) and stored for 24 hours at 37°C in different types of solutions: water, coffee, coffee with sugar, tea, tea with sugar, coffee with artificial creamer and sugar, cola, red wine, or sour cherry juice. Color of all specimens was measured before and after exposure with a colorimeter using CIE L ∗ a ∗ b ∗ relative, and color changes (ΔE ∗ ) were then calculated. The data were analyzed with a 2-way analysis of variance (ANOVA), and mean values were compared by the Tukey HSD test (α=.05). Results The interaction of provisional restorative materials and staining agents was statistically significant ( P =.0001). For the 5 restorative materials tested, the lowest ΔE ∗ values were observed in the water, cola, and sour cherry juice groups. The highest color difference for all restorative materials was observed in the red wine groups. For microhybrid composite materials and light-polymerized composite provisional material, when tea and coffee groups with and without sugar were compared, both groups with sugar demonstrated a higher color difference than without sugar. When comparing the 5 different restorative materials, the reinforced microfill material group (Micronew) demonstrated significantly less color change than the other materials tested. The highest color difference in this study was observed for specimens in the light-polymerized composite provisional material group (Revotek LC). Conclusion The reinforced microfill restorative material tested was found significantly more color stable than the autopolymerized bis-acryl, light-polymerized composite provisional restorative materials, and microhybrid composites tested. The largest color difference was observed in the light-polymerized composite provisional material. The presence of sugar in coffee and tea increased the color difference compared to coffee or tea without sugar for light-polymerized composite provisional material and microhybrid composites.

Effects of different drinks on stainability of resin composite provisional restorative materials.

Color related to ceramic and zirconia restorations: A review

Statement of problem. Visual color matching to determine shades in dentistry is inconsistent and unreliable. If accurate, instrumental measurement of tooth color would provide objective, quantified data to match natural teeth to clinical shade guides. Purpose. This study evaluated and compared the ability of a new computerized colorimeter and a simple visual test to match ceramic shade guide teeth. Material and methods. Thirty-one (n = 31) observers with normal color vision were allowed unlimited time to match one set of Vita Lumin shade guide teeth to the corresponding shade guide teeth of a second Vita Lumin shade guide. The same test was administered to 14 of the observers several months later to determine within-subject variability. A computerized colorimeter (Colortron II) equipped with a positioning guide was used to measure the middle third of each shade guide tooth. Through a "match tool" present in the computer's software, readings from one shade guide were matched with readings of the other shade guide by using CIELAB measurements and ΔE values. The mean number of correct matches by the colorimeter and of correct matches in visual test were compared with a 1-tailed t test. Repeatability for both tests was determined with a paired t test. Results. The Colortron II instrument correctly matched 8 of the 16 tabs (50% correct), whereas visual matching by examiners averaged 7.7 of 16 correct matches (48% correct) (standard deviation 2.7). No statistically significant differences existed between the 2 methods. The colorimeter demonstrated 100% repeatability and the visual test demonstrated fair repeatability (correlation coefficient r=.60). Conclusions. Shade determination by visual means was inconsistent. Accuracy of a new colorimeter in matching porcelain shade guide teeth was only slightly better. (J Prosthet Dent 1998;80:642-8.)

Evaluation of visual and instrument shade matching

Purpose Using the one-step polyvinyl siloxane impression technique, this study compared the effect of putty material working time on the dimensional accuracy of recovered improved stone casts.



Materials and Methods An acrylic resin master cast was fabricated with embedded reference points to enable both horizontal and vertical measurements. Four commercially available polyvinyl siloxane impression putties with light body washes were evaluated: 1) Extrude (Kerr), 2) Cutter (Coltere), 3) Express (3M), and 4) Reprosil (Caulk). Each putty was mixed by hand for 30 seconds, placed in a plastic stock tray, and seated on the master cast at 0, 30, 60, 90, and 120 seconds after mixing (N = 100, n = 5). The impressions were poured in improved stone, and vertical and horizontal measurements were made to 0.001 mm between reference points on recovered casts using an optical traveling microscope. ANOVA (p .05) was used to compare vertical and horizontal measurements to master cast dimensions.



Results No statistically significant difference was found among casts for all materials and time periods tested. When horizontal measurement ranges were evaluated, Extrude casts exhibited the widest range of measurement, especially when the trays were seated at 90 and 120 seconds. When vertical measurement ranges were evaluated, Express casts at 120 seconds exhibited the widest range.



Conclusions A high range of variability in vertical and horizontal dimensions occurred at the later time periods, especially for Extrude and Express casts. As a result of rapid polymerization and poor flow properties of putty materials, the impression tray should be seated within 60 seconds after putty mixing to reduce dimensional variability of recovered casts.

Scott R. Okubo

Papers

Evaluation of visual and instrument shade matching

Working times and dimensional accuracy of the one-step putty/wash impression technique.