Effects of ceramic layer thickness, cement color, and abutment tooth color on color reproduction of feldspathic veneers.

AIM: To optimize the esthetics of ceramic restorations, it is important to determine accurately the effects of various parameters on the final color of the restoration. However, there is a lack of information on what determines the color of translucent feldspathic veneers formed using ceramics such as Vita Mark II. The aim of this study was to evaluate the effects of the ceramic layer thickness, cement color, and abutment tooth color on the color of the feldspathic ceramic veneer restoration. MATERIAL AND METHODS: A total of 30 all-ceramic monolithic veneers (Vita Mark II) were fabricated using a CAD/CAM system. The crowns were divided into three groups of differing ceramic thickness (0.4-, 0.7-, and 1.0-mm thick). Each type of crown was seated on six different-colored abutment teeth (1M1 [reference], 1M2, 2M2, 3M2, 4M2, and 5M2) using seven different try-in paste colors. The color of the resulting restoration was evaluated using spectrophotometry with a spot-measurement device (Vita Easyshade Advance 4.0). Color data are expressed in CIE L*a*b* system coordinates, and color differences ΔE relative to the reference tooth were calculated and analyzed using one-way analysis of variance (ANOVA) with the Bonferroni post hoc test at α = 0.05. RESULTS: The color difference ΔE of the feldspathic all-ceramic veneer system was significantly affected by the thickness of the ceramic layer, the cement color, and the abutment tooth color (P < 0.05). The smallest values of ΔE compared with the reference color were found when try-in pastes shade -3 was used. As the thickness of the ceramic layer increased, a significant decrease in ΔE was found. As the color of the abutment tooth varied from light to dark, a significant increase was found in ΔE. CONCLUSION: The thickness of the ceramic layer, the cement color, and the abutment tooth color significantly affected the color of the resulting CAD/CAM feldspathic ceramic veneer restoration.

Reliability of visual and instrumental color matching.

OBJECTIVE: The aim of this investigation was to evaluate intra-rater and inter-rater reliability of visual and instrumental shade matching. MATERIALS AND METHODS: Forty individuals with normal color perception participated in this study. The right maxillary central incisor of a teaching model was prepared and restored with 10 feldspathic all-ceramic crowns of different shades. A shade matching session consisted of the observer (rater) visually selecting the best match by using VITA classical A1-D4 (VC) and VITA Toothguide 3D Master (3D) shade guides and the VITA Easyshade Advance intraoral spectrophotometer (ES) to obtain both VC and 3D matches. Three shade matching sessions were held with 4 to 6 weeks between sessions. Intra-rater reliability was assessed based on the percentage of agreement for the three sessions for the same observer, whereas the inter-rater reliability was calculated as mean percentage of agreement between different observers. The Fleiss' Kappa statistical analysis was used to evaluate visual inter-rater reliability. RESULTS: The mean intra-rater reliability for the visual shade selection was 64(11) for VC and 48(10) for 3D. The corresponding ES values were 96(4) for both VC and 3D. The percentages of observers who matched the same shade with VC and 3D were 55(10) and 43(12), respectively, while corresponding ES values were 88(8) for VC and 92(4) for 3D. CONCLUSIONS: The results for visual shade matching exhibited a high to moderate level of inconsistency for both intra-rater and inter-rater comparisons. The VITA Easyshade Advance intraoral spectrophotometer exhibited significantly better reliability compared with visual shade selection. CLINICAL SIGNIFICANCE: This study evaluates the ability of observers to consistently match the same shade visually and with a dental spectrophotometer in different sessions. The intra-rater and inter-rater reliability (agreement of repeated shade matching) of visual and instrumental tooth color matching strongly suggest the use of color matching instruments as a supplementary tool in everyday dental practice to enhance the esthetic outcome.

Comparison of visual shade matching and electronic color measurement device.

OBJECTIVE: The objective of this study was to compare the performance of visual shade matching and spectrophotometric measurements. MATERIALS AND METHODS: A total of 100 observers matched pairs of corresponding shade tabs from two VITA classical A1-D4 shade guides. The tab identifiers on one shade guide were masked. Lack of visible color differences between the corresponding tabs was confirmed by means of an intraoral spectrophotometer. Means and standard deviations were calculated. Analysis of variance (ANOVA) (α = 0.05) with a Bonferroni correction was performed to detect significance of differences between groups. RESULTS: A total of 72.5% of tab pairs (or 11.6 tabs) were matched using the visual method, and 98.9% were matched using the spectrophotometer (P < 0.001). Female observers showed significantly better results than male observers (P = 0.027). Both genders showed the highest visual scores in group B, followed by groups C, A, and D. CONCLUSIONS: Instrumental shade-matching systems have the potential to improve color matching in dentistry. Results were influenced by gender. CLINICAL RELEVANCE: The dental spectrophotometer exhibited a significantly higher percentage of correct matches of corresponding shade tabs compared with conventional visual shade matching.

Fracture Strength of Monolithic All-Ceramic Crowns on Titanium Implant Abutments.

PURPOSE: The fracture strengths of all-ceramic crowns cemented on titanium implant abutments may vary depending on crown materials and luting agents. The purpose of this study was to examine differences in fracture strength among crowns cemented on implant abutments using crowns made of seven different monolithic ceramic materials and five different luting agents. MATERIALS AND METHODS: In total, 525 crowns (75 each of Vita Mark II, feldspathic ceramic [FSC]; Ivoclar Empress CAD, leucite-reinforced glass ceramic [LrGC]; Ivoclar e.max CAD, lithium disilicate [LiDS]; Vita Suprinity, presintered zirconia-reinforced lithium silicate ceramic [PSZirLS]; Vita Enamic, polymer-reinforced fine-structure feldspathic ceramic [PolyFSP], Lava Ultimate; resin nanoceramic [ResNC], Celtra Duo; fully crystallized zirconia-reinforced lithium silicate [FcZirLS]) were milled using a CAD/CAM system. The inner surfaces of the crowns were etched and silanized. Titanium implant abutments were fixed on implant analogs, and airborne-particle abrasion was used on their exterior specific adhesion surfaces (Al2O3, 50 µm). Then, the abutments were degreased and silanized. The crowns were cemented on the implant abutments using five luting agents (Multilink Implant, Variolink II, RelyX Unicem, GC FujiCEM, Panavia 2.0). After thermocycling for 5,000 cycles (5 to 55°C, 30 seconds dwell time), the crowns were subjected to fracture strength testing under static load using a universal testing machine. Statistical analyses were performed using analysis of variance (α = .0002) and the Bonferroni correction. RESULTS: No significant difference among the luting agents was found using the different all-ceramic materials. Ceramic materials LiDS, PSZirLS, PolyFSP, and ResNC showed significantly higher fracture strength values compared with FSC, FcZirLS, and LrGC. The PSZirLS especially showed significantly better results. CONCLUSION: Within the limitations of this study, fracture strength was not differentially affected by the various luting agents. However, the fracture strength was significantly higher for PSZirLS, PolyFSP, ResNC, and LiDS ceramics than for the FSP, LrGC, and the FcZirLS ceramic with all luting agents tested.

Dental color matching: A comparison between visual and instrumental methods.

The aim of this study was to compare the agreement rate (%) and color difference (ΔE*ab) of three dental color-measuring devices, with the visual shade identification. The tooth color were determined by two operators, which were advised to select a VITA classic shade tab in each other's agreement. The Shadepilot (SP), CrystalEye (CE) and ShadeVision (SV) were used to measure tooth color. Statistically analyses include agreement rate (%), color difference (ΔE*ab), McNemar test (p=0.05), Student's t-test (p=0.05) and Bland Altman scatterplots. The SP had an agreement of 56.3% with the visual shade determination, the CE 49.0% and SV 51.3%. ΔE*ab of the visually and instrumentally selected shade tabs and natural teeth were frequently above the threshold for acceptability. Comparing both methods, for SP ΔE*ab values differ in a range of clinical acceptability.

Color difference thresholds in dentistry.

PURPOSE: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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. CLINICAL SIGNIFICANCE: 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.

Retentive strength of monolithic all-ceramic crowns on implant abutments.

The aim of the study was to determine the retentive strength of monolithic all-ceramic crowns cemented on titanium implant abutments. 225 crowns (75 crowns each of Mark II, Empress CAD, and e.max CAD) were milled using a CAD/ CAM system. The crowns were cemented onto sandblasted titanium implant abutments using five luting agents (Multilink Implant, Variolink II, RelyX Unicem, Fujicem, and Panavia 2.0). After thermocycling, the crowns were removed using a universal testing machine. The location of luting agent residue on the abutment and inner crown surfaces was evaluated. Statistical analysis was performed using ANOVA with the Bonferroni correction. In comparing the luting agents, no significant difference was found between Vita Mark II and Empress CAD. For e.max CAD, the luting agent RelyX Unicem had a significantly higher mean retentive strength than did Multilink Implant (p = 0.003) or Panavia 2.0 (p = 0.001). In comparing the ceramic materials, e.max CAD showed significantly higher pull-off strengths than the other two ceramic materials when the luting agents RelyX Unicem and Fujicem were used (all p < 0.001). The residues of nearly all luting agents were located entirely or almost entirely (75%-100%) on the inner crown surfaces of all ceramic materials, except for the luting agent GC Fujicem, which left more luting agent residue (0%-75%) on the abutment surfaces of all ceramic materials. In comparing the five luting agents, significant differences in the resulting retentive strength were only found for the ceramic material e.max CAD. The other ceramic materials did not show significant differences in retentive strength, independent of the luting agent.

Are dental color measuring devices CIE compliant?

OBJECTIVES: This in vitro study evaluated the accordance of dental color measurement devices with a Commission Internationale de l'Eclairage (CIE)-compliant reference system, by comparing the CIE lightness, chroma, and hue (L*C*h°) color coordinates of ceramic samples. METHODS: Four color measurement devices: Vita Easyshade® Advance (A); DeguDent Shadepilot™ (B); X-Rite® Shadevision (C); and Crystaleye Olympus (D), were compared with a CIE-compliant reference system by recording the L*C*h° color coordinates of ceramic samples matching the tooth colors of the Vita Linearguide 3D-Master®, under standardized test conditions. Differences between regression lines for the dental color measurement device data and regression lines for the CIE-compliant reference system data were evaluated. RESULTS: All devices offered high intraclass correlation coefficients (0.9771- 0.9999) for the L*C*h° color coordinates. The regression lines of the L* and C* coordinates for device A were steeper than those of the CIE-compliant reference system; the regression lines for devices B, C, and D were nearly parallel to those of the reference system, but with an offset. The regression lines of the h° coordinates for all devices were almost parallel to those of the reference system, with slopes near 1. Excluding the L* and h° coordinate measurements of device A, the measurements with the devices exhibited deviations from the reference system that were greater than those expected by chance (P < 0.0002). CONCLUSIONS: The dental color measurement devices assessed here offered excellent reproducibility, but showed significant deviations from the CIE-compliant reference system regarding the L*C*h° color coordinates.

Repeatability of color-measuring devices.

INTRODUCTION: The objective of this study was to evaluate the intra- and interdevice repeatability in different tooth regions using three color-measuring devices under clinical conditions. MATERIALS AND METHODS: Fifteen shade measurements (cervical, body, incisal) were recorded on 15 patients by one investigator using three color-measuring devices (VITA Easyshade compact, DeguDent Shadepilot, X-Rite ShadeVision). CIE Lab values were determined for all maxillary anterior teeth. Intraclass correlation coefficients (ICCs) were used to statistically analyze intra-and inter-device repeatability for different tooth regions. Color differences (ΔE) between measurements were also computed to evaluate the clinical acceptability of repeatability values. The data were evaluated using analysis of variance and Bonferroni's adjustment to control for multiple testing. Differences were deemed significant when P < 0.016. RESULTS: The three color-measuring devices generally exhibited high repeatability of color coordinates for all tooth regions (ICC > 0.516-0.986, ΔE < 3.03). In contrast, inter-device repeatability was lower for all tooth regions (ICC = 0.010-0.922, ΔE = 4.06-16.04). CONCLUSIONS: High intra-device repeatability of color coordinates could be achieved for all tooth regions when the same color-measuring device was used. However, because of low inter-device repeatability, results using different color-measuring devices are not comparable.

Four color-measuring devices compared with a spectrophotometric reference system.

OBJECTIVES: The objective of this study was to compare the L*C*h° color coordinates of dental color-measuring devices with those of a spectrophotometric reference system. METHODS: The International Commission on Illumination (CIE) L*C*h° color coordinates of ceramic samples, matching the colors of the VITA Linearguide, were recorded using four color-measuring devices (VITA Easyshade (A), VITA Easyshade compact (B), Degudent Shadepilot (C), X-Rite Shadevision (D)) and a spectrophotometric reference system under standardized test conditions. The intraclass correlation coefficients, regression lines with coefficients of determination, and mean deviations of the dental color-measuring devices from the spectrophotometric reference system were calculated. RESULTS: All of the devices had high intraclass correlation coefficients, between 0.979 and 1.000. Nearly all measurements, except the hue values of devices A, B, and D, showed coefficients of determination close to 1.0 over the range of measurements for L*C*h° color coordinates. Similarly, all of the devices had coefficients of determination near the optimum value of 1.0. Devices C and D produced regression line slopes near the optimum value of 1.0 and intercepts close to the optimum value of zero. Only the L* coordinate measurements of devices A and B and the h° coordinate measurements of device B differed not significantly from the spectrophotometric reference values. CONCLUSIONS: The electronic dental color-measuring devices tested showed excellent repeatability, but some devices showed substantial deviations in color coordinate values from the spectrophotometric reference system. Devices C and D showed higher precision than devices A and B.