Acceptability and perceptibility thresholds in dentistry: A comprehensive review of clinical and research applications.

Does background color influence visual thresholds?

The aim of this prospective multicenter study was to determine 50:50% perceptibility threshold (PT) and 50:50% acceptability threshold (AT) of dental ceramic under simulated clinical settings. The spectral radiance of 63 monochromatic ceramic specimens was determined using a non-contact spectroradiometer. A total of 60 specimen pairs, divided into 3 sets of 20 specimen pairs (medium to light shades, medium to dark shades, and dark shades), were selected for psychophysical experiment. The coordinating center and seven research sites obtained the Institutional Review Board (IRB) approvals prior the beginning of the experiment. Each research site had 25 observers, divided into five groups of five observers: dentists-D, dental students-S, dental auxiliaries-A, dental technicians-T, and lay persons-L. There were 35 observers per group (five observers per group at each site ×7 sites), for a total of 175 observers. Visual color comparisons were performed using a viewing booth. Takagi-Sugeno-Kang (TSK) fuzzy approximation was used for fitting the data points. The 50:50% PT and 50:50% AT were determined in CIELAB and CIEDE2000. The t-test was used to evaluate the statistical significance in thresholds differences. The CIELAB 50:50% PT was ΔEab = 1.2, whereas 50:50% AT was ΔEab = 2.7. Corresponding CIEDE2000 (ΔE00 ) values were 0.8 and 1.8, respectively. 50:50% PT by the observer group revealed differences among groups D, A, T, and L as compared with 50:50% PT for all observers. The 50:50% AT for all observers was statistically different than 50:50% AT in groups T and L. A 50:50% perceptibility and ATs were significantly different. The same is true for differences between two color difference formulas ΔE00 /ΔEab . Observer groups and sites showed high level of statistical difference in all thresholds. Visual color difference thresholds can serve as a quality control tool to guide the selection of esthetic dental materials, evaluate clinical performance, and interpret visual and instrumental findings in clinical dentistry, dental research, and subsequent standardization. The importance of quality control in dentistry is reinforced by increased esthetic demands of patients and dental professionals.

BackgroundThe aim of this study was to evaluate the 50%:50% perceptibility thresholds (PT) and acceptability thresholds (AT) for color differences in ceramic shade tabs observed by dentists and patients using CIEDE2000 color difference formula. Material and MethodsTwenty-two combinations of ceramic shade tabs from the VITA 3D Master shade guide were assembled to be used for the visual comparison analyses. The color difference between each shade tab pair was numerically determined by spectrophotometry using the VITA EasyShade V, and calculated using the CIEDE2000 formula (ΔE00). Twenty dentists and twenty patients were recruited for this study. All participants performed the visual assessment of the provided shade tab pairs under D65 illumination and a grey background, and requested to determine if they could perceive a color difference between them (PT) and whether they considered the combination clinically acceptable (AT). The correlation between numeric data of color difference between the shade tabs, and the perceptibility and acceptability thresholds given by the participants was analyzed by logistic regression (α=0.05; β=0.0085).ResultsThe PT for dentists was ΔE00= 2.29, and ΔE00= 2.27 for patients. The AT for dentists was ΔE00=2,41, and ΔE00=2,83 for patients. The results showed a statistically significant difference between PT and AT thresholds for both dentists and patients. However, there was no statistically significant differences in PT (p=0.39) or AT (p=0.54) between patients and dentists.ConclusionsWithin the limitations of this study, it was possible to conclude that while the PT and AT vary significantly within each group, they are statistically similar between dentists and patients when discriminating color differences in ceramic tabs. Key words:Color difference, esthetic, aesthetic, spectrophotometry, CIEDE2000.

To determine 50:50% perceptibility threshold (PT) and 50:50% acceptability threshold (AT) for computer-simulated samples of human gingiva using CIEDE2000 and CIELAB color difference formulas. Each of the 60 pairs of simulated human gingiva was displayed on a calibrated monitor, together with three pairs of upper central incisors of different lightness. The color of gingiva left and right from the midline was compared. A total of 30 observers (15 dentists, 15 laypersons) participated in the study. CIEDE2000 and CIELAB formulas were used to calculate the thresholds and a Takagi-Sugeno-Kang Fuzzy Approximation model was used as fitting procedure. Paired t-test (α = 0.05) was used in evaluation of statistical significance of differences. The PT and AT for CIEDE2000 and 95% confidence intervals were 1.1 [0.4, 1.7] and 2.8 [1.8, 4.0], respectively. Corresponding CIELAB values were 1.7 [0.2, 2.6] and 3.7 [2.1, 5.7]. Significant differences (P < .01) were recorded between PT and AT, between the corresponding threshold values in CIEDE2000 and CIELAB formulas as well as between dentists and laypersons. The difference between the perceptibility and acceptability threshold for gingiva was statistically significant in both CIEDE2000 and CIELAB. The same was true for differences between the corresponding thresholds using two color difference formulas, and between dentists and laypersons. Visual thresholds of human gingiva were not dependent upon lightness of adjacent teeth. Overall, CIEDE2000 color difference formula provided better fit than CIELAB formula in the evaluation of color difference thresholds of human gingiva. The data on visual thresholds for healthy human gingiva can be used as quality control tool/guide for selection and evaluation of dental materials, interpretation of color-related findings in clinical dentistry and research, and for standardization in dentistry. It is of particular value that this study was designed based on in-vivo color evaluation of healthy keratinized gingiva of subjects of different ethnicities, age groups, and gender.

Translucency thresholds for dental materials

To determine the influence of in vivo dehydration and rehydration on color and whiteness variations in maxillary anterior teeth of younger, middle-aged, and older individuals. The spectrophotometric shade of maxillary anterior teeth from younger (20 to 30 years, n=20), middle-aged (50 to 60 years, n=20) and older (65 to 80 years, n=20) participants were assessed at baseline and every 10 minutes for 30 minutes after rubber dam isolation (dehydration). The teeth were then allowed to rehydrate, and shade values were assessed every 10 minutes for 30 minutes, after 24 hours, and after 48 hours. Data were collected as International Commission on Illumination (CIE) L*a*b* color coordinates. Color differences (ΔE*ab) and whiteness differences (ΔWID) were evaluated. Statistical analysis was performed using one-way analysis of variance with the Tukey Honest Significant Difference test. The color and whiteness changes of maxillary anterior teeth in older individuals after dehydration for 30 minutes were significantly lower than that of younger and middle-aged individuals. In younger participants, after 10 minutes of dehydration, mean ΔE*ab values of maxillary anterior teeth were above the acceptability threshold (AT), while mean ΔWID values were above AT only in maxillary canines. In middle-aged participants, mean ΔE*ab values were above AT, and mean ΔWID values were above the perceptibility threshold (PT) and below AT after 10 minutes of dehydration. In older participants, mean ΔE*ab values were above PT and below AT at 20 minutes of dehydration, while mean ΔWID values were above PT at 10 minutes of dehydration, and both were above AT at 30 minutes of dehydration. The mean ΔE*ab values were above AT after 20 minutes of rehydration in younger and middle-aged participants, while they were below AT in older participants after 10 minutes of rehydration. Mean ΔWID values were below AT for older participants after 20 minutes of rehydration. All mean ΔWID values were below AT and above PT after 30 minutes of rehydration except central incisors of younger participants. After 24 hours of rehydration, mean ΔE*ab and mean ΔWID values of participants in all age groups were below AT. After 48 hours of rehydration, mean ΔE*ab and ΔWID values of participants in all age groups were below PT except mean ΔE*ab values of canines and mean ΔWID values of central incisors in younger participants. L*, a*, and b* values were significantly different between age groups at 30 minutes of dehydration and after 48 hours of rehydration (p<0.05). Color and whiteness changes due to dehydration were less pronounced in older participants. Dehydration for 10 minutes in most maxillary anterior teeth of younger and middle-aged participants led to perceptible and clinically unacceptable color and whiteness changes. Maxillary anterior teeth of older participants showed color and whiteness changes that were perceptible at 10 minutes of dehydration but clinically acceptable up to 30 minutes of dehydration. After 30 minutes of dehydration, a 10- and 20-minute rehydration was needed, respectively, for color and whiteness changes to be clinically acceptable in maxillary anterior teeth of older individuals, while a 30-minute rehydration was recommended for the middle aged group and for maxillary laterals and canines of the younger group. Color and whiteness changes in most maxillary anterior teeth were imperceptible only after 48 hours of rehydration.

Perceptibility and acceptability thresholds for color differences of light and dark maxillofacial skin replications

PURPOSEThe aim of this study is to evaluate the effect of resin cement color, cement thickness, and thermocycling on the final color of monolithic lithium disilicate crowns.MATERIALS AND METHODSA total of ninety prepared central incisors of typodont teeth were restored with lithium disilicate crowns which have different cement thicknesses (40 µm, 80 µm, and 120 µm) and cement shades (clear, yellow, and white). Color parameters of restorations were measured with a spectrophotometer in three different steps 1) before cementing 2) after cementing and 3) after thermocycling with 10000 cycles. Color differences (ΔE00) were calculated with the CIEDE2000 formula and evaluated according to perceptibility (0.8) and acceptability (1.8) thresholds. The ΔE00 data were analyzed by using two-way ANOVA before and after thermocycling (α = .05).RESULTSThere was no interaction between the cement shade and the cement thickness factors. After cementation, the mean ΔE00 was under the perceptibility threshold in the group of 40 µm cement thickness and clear cement while it was between the perceptibility and acceptability thresholds (0.8 < ΔE00 < 1.8) for all other groups. After thermocycling, the ΔE00 values were between the perceptibility and acceptability thresholds for all experimental groups. Although there were no significant differences among the groups, thermocycling increased the color difference values.CONCLUSIONThe cementation of restorations with clear, yellow, and white resin cements resulted in color differences with uncemented restorations except for the group cemented with clear cement in 40 µm cement thickness. All study groups revealed perceptible color change after thermocycling.

Whiteness difference thresholds in dentistry

Objectives: To examine the effects of surface treatments on the color stability, surface roughness, surface gloss, and wettability of monolithic polychromatic material jetting (MJT) 3D-printed denture material. Material and Methods: Twenty-one color variants of the same denture material (TrueDent; Stratasys, Eden, MN, USA) underwent two surface treatments (polishing only or polishing and glazing), creating 42 study groups with a total of 420 samples (n = 10 per group). The samples were manufactured using a PolyJet 3D printer (J5 DentaJet; Stratasys, Eden, MN, USA), a type of MJT 3D printer. Color measurements were taken with a digital spectrophotometer before and after the surface treatments, and quantitative color differences (ΔE00 and ΔC*) were calculated using the CIE2000 system. Comparisons of ΔE00 were made against the 50%:50% acceptability threshold (AT) of 1.8 and the 50%:50% perceptibility threshold (PT) of 0.8 for tooth shade, as well as the 50%:50% PT of 1.72 and the 50%:50% AT of 4.08 for gingival (pink) shade. After surface treatment, the gloss was measured using a glossmeter, surface roughness was measured with optical profilometry, and wettability was measured by contact angle measurements using an optical tensiometer. The significance of surface treatment on color changes for each color variant was evaluated using one-sided, one-sample t-tests against the AT and PT. The effects of surface treatment on surface gloss, surface roughness, contact angle, and ΔC* were analyzed using t-tests for each color variant. Pairwise comparisons between groups were made using Fisher's Protected Least Significant Differences (α = 0.05). Results: In most cases, glazing caused the color change (ΔE00) to exceed the AT and PT, with a few exceptions. Most materials exhibited a more vibrant (more saturated) appearance and statistically higher chroma, with glazed surface treatments compared to polished ones, though there were some exceptions. For all materials, the glazed samples had significantly higher gloss units than the polished ones (p < 0.0001). Additionally, all materials showed significantly higher surface roughness in glazed samples compared to polished ones (p < 0.0001 for most). The polished samples had significantly higher contact angles (p < 0.0001 for most). Conclusions: Surface treatments significantly influenced the color, surface gloss, surface roughness, and wettability of MJT 3D-printed denture materials. Glazing led to increased chroma and gloss and produced more hydrophilic surfaces, although it also increased surface roughness. These results highlight the importance of surface treatment selection in optimizing the clinical performance of MJT-fabricated dentures.

Background and aimsTo verify the color match of metal-ceramic and full ceramic crowns, using instrumental methods.MethodsA number of 153 teeth (anterior and posterior teeth), in 62 patients, were restored with metal ceramic (MC, n=119), pressed-ceramic (PC, n=28), and zirconia-ceramic (ZC, n=6) full coverage crowns. The shade of a reference natural tooth was recorded instrumentally with a dental spectrophotometer (Vitaeasyshade Advance 4.0) in “single tooth measurement”, which provided the base color in Vita Classic (VC) and Vita 3D Master shades (3D).For verifying the outcome of the restoration “verify restoration” mode was used, and ΔE values were recorded for both VC and 3D Master shade guides. Moreover, matching symbols were also recorded (***=good, **=fair, *=poor). Descriptive statistics was performed and data were analyzed (One-sample z-Test, α=0.05) for comparison with visual thresholds in dentistry (Perceptibility Threshold – PT=1.2 and Acceptability Threshold – AT=2.7).ResultsThe data did not follow a normal distribution (Kolmogorov-Smirnov test, p<0.05). Recorded color difference was significantly higher than PT and AT, for all types of restorations, regardless of the coding system (p<0.05). For MC crowns in 2.52% (4.20% for 3D) of the cases the color difference was smaller than PT, in 19.32% (the same for 3D) of cases was between PT and AT, and in 78.15% (76.47% for 3D) of cases was higher than the AT. For PC crowns in 3.57% (0% for 3D) of the cases the color difference was smaller than PT, in 25% (32.14% for 3D) of cases was between PT and AT, and in 71.42% (67.85% for 3D) of cases was higher than the AT. In the case of ZC crowns none of the restorations had color difference smaller than PT, but in 16.66% of cases was between PT and AT, and in 83.33% of cases was higher than the AT, for both VC and 3D.ConclusionWithin the limitations of the study, a better color match was achieved in the case of pressed ceramic crowns, made of lithium disilicate. In most of the situations the color difference between the restoration and the reference tooth exceeded the perceptibility thresholds, but the matching was recorded as “fair” by the spectrophotometer.

This study aimed to determine the perceptibility and acceptability thresholds for the relative translucency parameter (RTP) of ceramic materials, using observer-based assessments under simulated clinical conditions. The null hypothesis was that no difference existed in RTP values for perceptibility and acceptability thresholds. Specimens of lithium disilicate in five translucency levels were fabricated into discs and anterior crowns. RTP was calculated using the CIEDE2000 color difference formula with black and white backings. Digital photographs of paired crowns on typodont models were presented to 30 dental clinicians in a controlled visual environment using a randomized Qualtrics survey. Observers judged translucency differences (perceptibility) and clinical appropriateness (acceptability). A repeated-measures logistic regression model was used to analyze observer responses. A significant relationship was found between Delta RTP (△RTP) and both perceptibility and acceptability judgments (p < 0.0001). Perceptibility thresholds were identified at -17.5, while acceptability thresholds were defined at 12.6. △RTP values exceeding 27 were consistently perceived as different, while values below 12 were often judged acceptable. The null hypothesis was rejected, confirming a statistical difference between perceptibility and acceptability judgments and their relationship to RTP. Clinically relevant RTP thresholds for translucency perception and acceptability were established. These findings validate RTP as a meaningful and quantifiable tool for assessing esthetic differences in translucency among restorative materials. The results have implications for material selection and clinical decision-making in prosthodontics.

To determine if identical dental shade guides can be used interchangeably considering their precision. Twenty Vita classical (VC) and Vita 3D-Master (VM) shade guides were subjected to spectrophotometric measurements and their CIELab values were measured in three shade tab regions: incisal, middle, and cervical and also in total. The mean L*, a*, and b* values for analogous shade tabs were calculated to identify CIELab values for typical shades. ∆E00 color differences between a typical shade and its analogous shade tabs were measured. ∆E00 values were compared with perceptibility (∆E00 = 0.8) and acceptability (∆E00 = 1.8) thresholds using one-sample t test (α= 0.05). An error was considered when the ∆E00 value was greater than the threshold. Subsequently, the shade guides' precision scores were calculated. Mean ∆E00 values ranged between 0.3 and 0.5 for VC tabs and between 0.3 and 0.6 for VM tabs. Precision scores for both shade guides ranged from 83.3% to 100%, considering the perceptibility threshold. Regarding the acceptability threshold, precision scores for VC ranged from 93.3% to 100%, while the precision scores for VM were 100%. Owing to high precision of VC and VM, identical dental shade guides can be used interchangeably. Using identical dental shade guides interchangeably may affect the color results of restorative treatments. This study identified high levels of precision for identical shade tabs of Vita classical and Vita 3D-Master across different batches. Thus, similar dental shade guides can be used interchangeably.

ABSTRACTObjectiveThis study assessed the impact of the method of manufacturing, surface treatment, and thickness on the stainability of zirconia after thermocycling.MethodsTwenty 0.5 × 10 mm and 20 1 × 10 mm zirconia disks were fabricated using a milling machine. Also, 20 0.5 × 10 mm and 20 1 × 10 mm zirconia disks were fabricated using a 3D printer. After sintering, samples were subjected to one of the two surface treatments (n = 10). Eight study groups were arranged as (1) 0.5 mm printed–polished, (2) 1 mm printed–polished, (3) 0.5 mm printed–glazed, (4) 1 mm printed–glazed, (5) 0.5 mm milled–polished, (6) 1 mm milled–polished, (7) 0.5 mm milled–glazed, and (8) 1 mm milled–glazed. CIELab values were measured with a spectrophotometer before and after 10,000 thermal cycles in coffee solution. ΔE00 readings were compared with perceptibility (< 0.8) and acceptability (< 1.8) thresholds. Data were analyzed using three‐way ANOVA and the Games–Howell test (α = 0.05).ResultsAlthough all mean ΔE00 values were below the acceptability threshold, only 1 mm printed–glazed zirconia and all milled zirconia samples, except for the 0.5 mm polished group, were below the perceptibility threshold. A significant interaction was found between the production method, surface treatment, and thickness (p = 0.002); 0.5 mm printed zirconia, either polished or glazed, and also 1 mm polished printed zirconia exhibited significantly higher ΔE00 than their milled counterparts. Moreover, glazing significantly reduced stainability in all zirconia specimens (p < 0.05). Also, 1 mm milled–polished zirconia had a lower ΔE00 value than its 0.5 mm counterpart (p = 0.038).ConclusionsPrinted zirconia had less color stability than milled zirconia. Glazing provided the lower color change for both milled and printed zirconia. Thicker milled–polished zirconia had a better color stability.Clinical SignificanceAlthough the color stainability of printed zirconia was more than milled zirconia, it showed clinically acceptable color change values along with the milled zirconia, regardless of the method of surface treatment and thickness.

To estimate the time required for teeth to dehydrate and rehydrate and its relation to the accuracy of tooth shade selection. Thirty-two participants were recruited, and color measurements were conducted using a spectrophotometer placed with a custom jig. After isolation, baseline measurements were made at 1, 2, 3, 5, 7, 10, and 15 min intervals to determine dehydration time. After mouth rinsing, measurements were made to determine rehydration time. CIEDE2000 values were obtained for color change between the baseline recordings and all intervals and compared to the 50:50% perceptibility and acceptability thresholds. Analysis of variance (anova) and Tukey test was used for multiple comparisons. The tooth color changes were beyond the ΔE00 perceptibility threshold (0.8) within the first minute of dehydration (P > 0.0001). After the first minute, 87% of the teeth were beyond the ΔE00 perceptibility threshold (0.8), and 72% of the teeth were beyond the ΔE00 acceptability threshold (1.8). After 15 min of rehydration, 90% of the teeth were beyond the perceptibility threshold, and 65% were beyond the acceptability threshold. Shade selection procedures should be carried out within the first minute and before teeth dehydrate by means of isolation. Teeth do not rehydrate within 15 min after rehydration. Teeth dehydration has a negative impact on shade selection, which can affect the final esthetic outcome. Shade selection should be performed at the beginning of any restorative procedure.