|Year : 2017 | Volume
| Issue : 1 | Page : 12-18
Visual and instrumental evaluation of reliability of clinical ceramic restoration with dental shade guide by two distinct observer population: An observational study
Dolly Gupta, Mahantesh Bembalagi, Raghunath Patil
Department of Prosthodontics and Crown and Bridge, KLE VK Institute of Dental Sciences, Belagavi, Karnataka, India
|Date of Web Publication||18-Jan-2017|
Dr. Dolly Gupta
Department of Prosthodontics and Crown and Bridge, KLE VK Institute of Dental Sciences, Belagavi, Karnataka
Source of Support: None, Conflict of Interest: None
Context: Dental ceramics are the most natural appearing replacement material for missing tooth substance available in a range of shades and translucencies to achieve a life-like result. Ceramic restorations are fabricated with porcelain layers of different opacity, shade, and thickness to provide a natural appearance. Since the ceramic layer thickness is important for shade development, utmost precision and control are required for a predictable and reproducible result. Shade guides provided by various companies are of 2.5 mm thickness, but clinically all-ceramic crown restoration requires a maximum thickness of 1.5 mm.
Aim: The purpose of this study was to evaluate the shade of clinical ceramic restorations with dental shade guide by two distinct observer population.
Materials and Methods: A total of 400 individuals aged 23-45 years participated in this observational study. Two hundred were dental professionals (DPs) and other 200 were nonprofessionals (NPs), a random passerby in the vicinity of the dental school. Evaluation was done between a shade guide and ceramic restorations of thickness 1.5 mm. For visual evaluation, observers were asked to take one shade tab from a box containing eight shades and to select the matching clinical ceramic restoration, and a number of correctly matched shades were recorded. Same experiment was repeated after 1 month for half of the observers. For instrumental evaluation, spectrophotometer was used, and three readings were taken per sample.
Results: The results from the present study showed that there was a significant difference for number of correct shades matched by two observer groups. Percentage of correctly matched shades by instrumental evaluation was 37%. Good visual-instrumental shade agreement was observed.
Conclusions: The present study concluded that there was significant difference for number of correct shades matched by two observer groups - DP and NP. Good visual-instrumental agreement was found.
Keywords: All ceramic restorations, instrumental matching, visual matching, VITAPAN Shade Guide
|How to cite this article:|
Gupta D, Bembalagi M, Patil R. Visual and instrumental evaluation of reliability of clinical ceramic restoration with dental shade guide by two distinct observer population: An observational study. Indian J Health Sci Biomed Res 2017;10:12-8
|How to cite this URL:|
Gupta D, Bembalagi M, Patil R. Visual and instrumental evaluation of reliability of clinical ceramic restoration with dental shade guide by two distinct observer population: An observational study. Indian J Health Sci Biomed Res [serial online] 2017 [cited 2019 Oct 20];10:12-8. Available from: http://www.ijournalhs.org/text.asp?2017/10/1/12/198575
| Introduction|| |
The desire to look beautiful has been prevalent for ages. It never dies rather it upsurges itself in different forms and fields of life. Hence, how can the field of dentistry be not affected by people's demands? They desire a restoration that suffices their hunger for something that looks very much like original and what material could satisfy these desires better than ceramics.
Metal ceramic crowns (MCCs) are the most common fixed prostheses for the full-coverage restoration of the anterior teeth. However, the opaque substructure of the MCCs restricts its potential in areas of high esthetic importance. All ceramic crowns, having no metal substructure, permit greater light transmission within the crown, thereby improving the color and translucency of the restoration.
Ceramics are among the earliest to group of inorganic material to be structurally modified by man. For over 200 years, interest in ceramics has held the attention of dental professionals (DPs). Although dentists have remained suspicious of the structural longevity, potential abrasivity, and fit of ceramic restorations, their unsurpassed esthetic and biocompatible qualities have provided the stimulus to overcome their limitations. Dental ceramics are the most natural appearing replacement materials for missing tooth substance available in a range of shades and translucencies to achieve a life-like result.
Many color order systems are available, but for a variety of reasons, including worldwide recognition, consistency, flexibility, and simplicity, the Munsell color order system is the system of choice for color matching in dentistry. According to the Munsell system, color has three components namely - hue, chroma, and value.
Color determination in dentistry can be divided into two categories: visual and instrumental. Visual color determination by comparison of a patient's tooth with a color standard is the most frequently applied method in clinical dentistry. The cones are color-sensitive receptors in the eye responsible for encoding color. Each cone contains structures or visual pigments sensitive to one of three wavelengths of light: red, green, and blue.
Instrumental measurements can quantify color and enable communication to be more uniform and precise. Spectrophotometers and colorimeters have been used to attempt to overcome problems with visual matching in dentistry. Colorimeters provide measurements in CIELAB units (L*a*b*) in a three-dimensional color space and were developed by the Commission Internationale de I"Eclairage in 1931. The L* color coordinate ranges from 0 to 100 and represents lightness; the a* color coordinate ranges from 90 to 70 and represents greenness on the positive axis and redness on the negative; the b* color coordinate ranges from 80 to 100 and represents yellowness (positive b*) and blueness (negative b*).
However, the aim of this study is to evaluate and compare the shade of clinical ceramic restorations with dental shade guide both visually and instrumentally.
| Materials and Methods|| |
This observational study was conducted in the Department of Prosthodontics and Crown and Bridge, KLE VK Institute of Dental Sciences, Belagavi. A total of 400 individuals aged 23-45 years participated in this observational study. Out of 400, 200 was dental professionals (DP), including staff and postgraduate students of KLE V.K Institute Of Dental Sciences, Belagavi, and other 200 was nonprofessionals (NPs), random passerby in the vicinity of the dental school. Eight ceramic restorations were fabricated of shades A1, A2, A3, A3.5, B1, B2, C1, and C2 (one sample for each shade). To fabricate the ceramic restoration of 1.5 mm thickness, first a tooth preparation was done on 21 typodont for all ceramic restorations [Figure 1]. Two-plane labial reduction was done of 1.5 mm thickness and incisal reduction of 2.0 mm thickness. Final thickness was checked with the putty index made before the preparation. From the single preparation, all eight ceramic restorations were fabricated. Eight wax patterns copings were made, sprued, and invested followed by pressing with VITAPAN Pressable ceramic of the required shades. Then, the copings were trimmed to get the even thickness of 0.5 mm [Figure 2], which is followed by layering of the dentin and enamel. Thickness of the restoration was checked and maintained after each firing using the electronic caliper with 10-micrometer resolution. Once the dentin layer is applied and fired, the thickness was maintained to 1.3 mm [Figure 3], followed by enamel layering and final thickness of 1.5 mm. After finishing, add-on glazing was done [Figure 4]. No external stains were applied on any of the ceramic restoration.
|Figure 4: Eight ceramic restorations of thickness 1.5 mm of shades - A1, A2, A3, A3.5, B1, B2, C1, and C2 (top from left to right) and corresponding shade tabs from VITA Classic Shade Guide (bottom)|
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Visual matching test for shade tab to ceramic restoration was done with 400 observers, out of which 200 were DP and 200 were NP. NP (n = 200) was instructed individually to focus on the middle third of the shade tab when selecting the shade tab to ceramic restoration. The middle third focus corresponded to the area targeted with the instrument. Each observer DP and NP was asked to take one shade tab from a box containing eight shades and to select the matching clinical ceramic restoration. All identifying shade nomenclature was masked to prevent influence on shade selections. Observers were given unlimited time to match the shade guide with ceramic restorations, under standardized illumination. Testing was done between noon and 1 pm under normal daylight. The number of correct shades selected was recorded. One month later, half of the observers were tested again under the identical conditions to determine the repeatability of human observers.
The spectrophotometer X-Rite [Figure 5], instrument, was used for instrumental color matching. The middle third of the shade guide tooth was selected for all readings. The instrument was calibrated before use according to the manufacturers' recommendations. Each sample tab of both shade guide and ceramic restorations was measured three times, and an average CIE coordinate measurement was recorded for each tab, from which ΔE was calculated.
To check the repeatability of an instrument, test was repeated after 1 month, and three readings for each tab were recorded, and ΔE was calculated.
Results obtained from visual and instrumental evaluation were then subjected to statistical analysis.
The values of the present observational study, which revealed the effect of different thickness of porcelain layer on shade matching, were subjected to statistical analysis to check the correlation between two observations made.
| Results|| |
[Table 1] - mean and standard deviation of correctly matched shades for 200 observers of each group were tabulated. DPs matched mean of 3.2 shades correctly out of 8 and NPs 2.9 out of 8. The number of correctly matched shades between two observer groups was found to be statistically significantly different with P = 0.048.
|Table 1: Comparison of the shade of clinical ceramic restorations to shade tab in terms of mean (standard deviation) as given by nonprofessionals and dental professionals using unpaired t-test |
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[Table 2] - When correlation between initial scores and after 1 month was checked. Highly significant correlation was found between two readings taken, 1 month apart for both the observer groups. The value of correlation coefficient for NP group was found to be 0.718 and for DP group 0.771.
|Table 2: Correlation between initial scores and the scores taken after 1 month for both nonprofessionals and dental professionals using Pearson's correlation coefficient |
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[Table 3] - on comparison of shade matching visual v/s instrumental. The difference between shade matching by visual or instrumental matching was found to be statistically nonsignificant.
|Table 3: Comparison of the shade of clinical ceramic restorations in terms of Mean (SD) as given by Non - Professionals and Dental Professionals and instrumental evaluation using unpaired t test |
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[Table 4] - correlation of 2 readings taken a month apart for instrumental evaluation. Correlation coefficient for two readings taken by spectrophotometer was found to be 0.991, highly significant, inferring very high repeatability of the instrument.
|Table 4: Correlation between initial scores and the scores taken after 1 month for instrumental evaluation using Pearson's correlation coefficient |
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| Discussion|| |
Under standard conditions, using ceramic restoration, and shade tab from VITAPAN Classic Shade Guide, DP observers produced an average of 3.2 correct matches out of 8, i.e., 40% correct matches. Out of the 200 observers, 4 had no mismatches and resulted in a perfect score of 8 whereas 6 scored 0 also. Visual color determination is a complex process and involves a number of subjective and objective phenomenon. A 40% average of correct matches of DP observer group was found to be consistent with other studies. In a study done by Della Bona et al., three distinct observer populations - nondental observers, dental students, and dentists participated. Nondental observers matched shade tabs-to-tabs whereas dental students and dentists conducted intraoral shade matches in two lighting conditions, cool white fluorescent lighting, and natural sunlight, and it was found that dentists population matched highest, i.e., 42% under natural sunlight.
In the present study, ceramic restoration of thickness 1.5 mm, which is the maximum thickness required clinically, was matched with shade tabs of thickness 2.5 mm by DPs with the score of 40% correct matches which in contrast to the study done by Gokce et al., in which two sets of porcelain discs of 16 shades each were manufactured of thickness 2.5 mm to exact CIE L*a*b* values were subjected to shade matching under standard lighting condition, and it was found that DPs with normal color vision matches 63% shades correctly.
So from this, it can be inferred that with the difference in the thickness of the porcelain layer, there will be a difference in shade matching. Percentage of correct matches decreases with the decrease in the thickness of porcelain layer. Moreover, to get a better esthetic outcome, shade tabs of 1.5 mm thickness can be manufactured for better shade matching.
The other observer group of NPs in the present study matched an average of 2.9 shades correctly out of 8, i.e., 36% correct matches. The results for the NP group were found to be consistent with other studies. A study done by Della Bona et al., also showed similar results with 32% of correct matches when nondental observer group was asked to match shade tabs-to-tabs. The difference between correct matches of DP group and NP group was found to be statistically significant with the P < 0.05 as shown in [Table 1], which was also found to be consistent with results of other studies. Thus, rejecting the null hypothesis of the present study which stated that there was no significant difference in shade selection of clinical ceramic restoration with dental shade guide by two distinct observer population. Whereas in another study done by Poljak-Guberina et al., results are contradicting and they stated that no statistically significant differences were recorded based on profession, gender, and age.
Comparison of the shade of clinical ceramic restorations to shade tab in terms of P value as given by DPs and NPs (1st and 2nd reading after 1 month) using paired t-test was found to be 0.15 and 0.12, respectively. There was no statistically significant difference found between 1st reading and 2nd reading taken after 1 month for both the groups inferring good reliability of a human eye. For reliability statistics, results were subjected to Cronbach's alpha test for both DP and NP group, and results showed Cronbach's alpha value of 0.848 and 0.809, respectively, showing good reliability. The results were found to be consistent with the study done by Okubo et al., A study done by William D. Culpepper had contradictory results showing a lack of consistency among the individual dentists participating in the experiment in matching natural tooth shades.
To check correlation between initial scores and the scores taken after 1 month for both DP and NP group, average mean values were subjected to Pearson's correlation coefficient, and a good correlation was found between and among the observers for the mean number of correct matches when the test was performed second time.
Visual color assessment is dependent on the observer's physiologic and psychologic responses. In join, consistency may result from factors such as fatigue, aging, emotions, lighting conditions, previous eye exposure, object, and metamerism. Despite these limitations, the human eye can detect very small differences in color. However, the ability to communicate these color differences in terms of magnitude and the nature of the difference is limited.
Instrumental measurements objectively quantify color and enable communication to be more uniform and precise. Instruments for clinical shade matching include spectrophotometers, colorimeters, and imaging systems. Spectrophotometers are among the most accurate, useful, and flexible instrument for overall color matching. Studies have been performed comparing the accuracy and reliability of various clinical shade matching devices. A study was done by Kim-Pusateri et al., evaluating the reliability and accuracy of four dental shade matching instruments, and it was found that spectrophotometers showed highest accuracy of 92.6% and reliability of 96.9%.
In the present study, for instrumental evaluation, spectrophotometer was used. Spectrophotometer gives CIE L*a*b* coordinates and ΔE values. ΔE value is important in quantifying the color difference between two samples.
ΔE values are interpreted as:
- 0 = Perfect match
- 0-2 = Mismatch, human eye cannot detect, only machine can detect
- 2-3 = Mismatch, only expert eye can detect
- >3 = Mismatch, visible to all.
Under controlled condition in the present study, a ΔE value of 2 or <2 was considered as a perfect match and only above was considered as a mismatch. Moreover, results of instrumental evaluation in the present study showed three correct matches out of 8, i.e., 37.5% correct matches which were found to be inconsistent with other studies. In a study done by Okubo et al., instrumental evaluation showed 50% correct matches.
In another study done by Ho-Jung Son et al., influence of dentin porcelain thickness was checked, and it was concluded from this study that increases in dentin porcelain thickness results in a gradual decrease in lightness and an increase in the red-green coordinate and the yellow-blue coordinate. Hence, from this, we can infer the results of the present study could be inconsistent with the other studies because of the difference in the thickness of the samples subjected to evaluation.
According to the study done by Dozic et al., also small changes in opaque/translucent porcelain thickness ratio can perceivably influence the final shade of the layered specimen. On the other hand, some of the authors have also concluded through their studies that increasing thickness of the semi-translucent systems from 1.0 to 2.0 mm did not improve shade matching.
In consideration for visual-instrumental agreement, the human eye sees the heterogenous aspects of shade tab or ceramic restoration or tooth, the variation in shade, and translucency whereas an instrumental evaluation amalgamates these characteristics and makes it a homogenous shade. In instrumental shade identification, the amount of light that is reflected back to the instrument from the surface of the sample affects the reading.
In this research, in regards to visual-instrumental shade agreement for both the observer group, DP and NP were found to be statistically not significantly different, which are in accordance with the results of other studies as well., In a study done by R. Duane Douglas and Jane D. Brewer, there was a strong correlation found between instrument and visual assessment.
An important consideration in instrumental evaluation is the ability of these instruments to measure tooth/shade tab/ceramic restoration color reliably and accurately. Reliability refers to the consistency of the device in matching the same specimen. In the present study, two readings of instrumental evaluation taken in a month gap were subjected to Pearson's correlation coefficient test, and result was found to be highly significant with 0.991 correlation coefficient. Results are in accordance with the results of other studies.,,, A study done by Tung et al., in 2002 also showed similar results.
In a study done by Pecho et al., he compared visual and instrumental shade matching performances using two shade guides - Vita Classical (VC) and Vita Toothguide 3D-Master and three color difference formulas, concluding neither color difference formula was 100% efficient. Yet, the use of CIEDE2000 (2:1:1) and VC shade guide most closely represented the visual perception of dental students. It is recommended that instrumental color determination be always accompanied by experienced human visual perception.
| Conclusions|| |
Within the limitations of this observational study, the following conclusions can be drawn:
- There was a significant difference for number of correct shades matched by two observer groups, i.e., DP and NP
- Correlation between two readings taken for checking reliability of human eye was found to be high for both DP and NP group
- Percentage of correct matched shades by instrumental evaluation was found to be lesser in the present study as compared to the literature, due to the difference in the thickness of the compared samples
- In this research, in regards to visual-instrumental shade agreement for both observer groups, DP and NP were found to be statistically not different with instrumental evaluation
- Repeatability of an instrument used in the study was highly significant, with correlation coefficient of 0.991.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3], [Table 4]