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ORIGINAL ARTICLES
NUMBER 4 YEAR 2010
Conventional Versus Spectrophotometric Shade Taking for the Upper Central Incisor: A Clinical Comparative Study
1 Department of Prosthodontics, Victor Babes University of Medicine and Pharmacy Timisoara, Faculty of Dentistry

Correspondence to:
Anca Jivanescu, Victor Babes University of Medicine and Pharmacy Timisoara, Faculty of Dentistry, Department of Prosthodontics, Timisoara, Anghel Saligny str., No 17, Tel: 0744-570488.
E-mail: ajivanescu@yahoo.com
REZUMAT
Introducere: Restaurarea unui singur incisiv central superior reprezinta o adevarata provocare pentru echipa medic dentist- tehnician dentar. Corecta alegere, comunicare si reproducerea cat mai precisa a culorii incisivului central superior reprezinta cheia succesului in cazul tratamentului restaurator protetic. Obiectiv: avestui studiu a fost determinarea variabilitatii intre diferiti observatori in ceea ce priveste alegerea culorii unui incisiv central superior, utilizand doua chei de culori (Vita Classic si Vitapan 3D Master) si compararea rezultatelor cu cele obtinute cu ajutorul spectrofotometrului Vita Easy Shade. Material si metoda: Studiul a implicat 26 de studenti ai Facultatii de Medicina Dentara, care au examinat culoarea incisivului central la 4 pacienti cu ajutorul a doua chei de culori conventionale (Vita Classic si Vitapan 3D Master). Rezultatele au fost comparate cu cele obtinute cu spectrofotometrul Vita Easy Shade. Pentru compararea rezultatelor intre determinarile facute de studenti si cele facute de spectrofotometru s-a utilizat un software de analiza statistica IBM SPSS Statistics (Version 19). Rezultate: Procentajul de corelatie calculat a fost de 37,5 % pentru cele doua chei de culori utilizate. Concluzia: acestui studiu a fost ca determinarea culorii in cazul incisivului central cu ajutorul cheilor de culori prezinta variatii destul de mari intre diferiti examinatori, iar spetrofotometrul Vita Easy Shade poate fi un util mijloc educational .

ABSTRACT
Introduction: Restoration of a single upper central incisor is one of the most challenging situations for the dentist-dental technician team. Proper selection, communication and more accurate color reproduction of the upper central incisor is the key to a successful prosthodontic treatment. The objective of this study was to determine the inter-observer variability in shade selection for the upper central incisor when using two shade guides (Vita Classic and Vitapan 3D Master) and to compare the results with those of Vita Easy Shade spectrophotometer. Material and method: The study involved 26 students of the Faculty of Dentistry, who examined the color of central incisor for 4 patients with conventional shade guides. Standard conditions were used to choose the color and determinations were made independently by two shade guides, Vita Classic and Vita 3D Master. The results were compared with those obtained by using the Vita Easy Shade spectrophotometer. The IBM SPSS Statistics (Version 19) software was used to statistically compare the results of the students with the spectrophotometer results. Results: A frequencies analysis concluded that the correlation percentage between the determinations of the students and the spectrophotometer was 37.5% for both Vita Classic and Vitapan 3D Master shade guide. Conclusion: this study showed that there are some large variations in color determination for the upper central incisor by using 2 conventional shade guides and the spectrophotometer may be a useful educational tool.
INTRODUCTION
The aesthetic restoration means a similar shape and color of related teeth. Determination and precise communication of color is a requirement for a successful restoration and for obtaining an aesthetic harmony. Often young professionals are faced with situations where the correct choice of color is a very difficult task, which can lead to unwanted errors. Tooth shade matching in prosthetic dentistry involves five steps:1
• Analysis of color;
• Color communication to the dental technician;
• Interpretation of the color information in the ceramic part selection;
• Making the restoration;
• Color verification before the final cementation in the mouth.
According to a study conducted in 2002 in Dental Lab Products Report, almost half of the dentists have modified the technique of choosing the color for the upper central incisor2.
Since the traditional techniques of choice for shade guides are subjective, the modern digital devices of color analysis allow precise and standardized measurements.
In the last two decades, the use of colorimeters and spectrophotometers became more frequent. Colorimeter first appeared in 1870, but by 1990 the primary use was in chemistry. Douglas said that in the oral cavity, the resolution of digital colorimeters is about as close as the human eye.3
Spectrophotometric analysis is based on the wave length reflected by the tooth. The rays reflected from the tooth are captured by an optical instrument and are measured, in comparison with those from the database provided by the shade guides. This technology measures 300,000 spectral curves, which includes 6 million of reference points based on different wave lengths.4 The spectrophotometer measures numerous points along the visible spectrum and can be used to determine the values of CIE L* a* b*. Spectrophotometer is an accurate device by itself and it is independent of the light source or filters.
The spectrophotometer measures the closest shade to the traditional shade guides (Vita Classic and Vitapan 3D Master). Using the digital system will implicate the measurement of the parameter ΔE, which records the difference between two colors.5

MATERIAL AND METHOD

Our study involved 26 students of the Faculty of Dentistry. First, the visual acuity was determined, for the 26 volunteers. We have used a training program, an educational software provided by Paravina4 which has tested the ability of differentiating the value, the chroma and hue. In this study were selected only those students who had no chromatic perception disabilities (a test score above 80%).
In the present study was analyzed the tooth shade of the upper central incisor for 4 patients (2 men and 2 women), with the help of 2 shade guides. The shade guides were as follows:
1. Vita Classic (16 color tabs guide)
2. Vitapan 3D master (the 26 colors of Vita 3D Master shade guide are arranged according to the degree of clinical crown value).
Examinations were held in a separate room, not to be influenced by the other subjects. Time of determination for each shade guide was about 1 minute for every 4 patients.
The conditions of tooth shade match were: natural light, a sunny day at noon, in front of the window. Patients’ clothes were covered with a gray-white material.
First, the students started the color determination with the help of Vita Classic shade guide, followed by Vitapan Master 3D shade guide. (Fig. 1, 2)
Figure 1. The shade determination for the upper central incisor with Vita Lumin Vacuum shade guide
Figure 2. The shade determination for the upper central incisor with Vitapan 3D Master shade guide

Finally, the instructor determined the color by using the spectrophotometer Vita Easy Shade. (Fig.3) In this case the light or environment conditions did not influence the results.

Figure 3. The color (shade) determination for the upper central incisor with the Vita Easy Shade spectrophotometer

RESULTS

This study has been conducted on 26 students of the Faculty of Dentistry analyzing the tooth shade of an upper central incisor in 4 patients (2 men and 2 women), with the help of 2 shade guides: Vita Classic and Vitapan 3D Master. The shade perception of the students was compared with the shade as obtained by the Vita Easy Shade spectrophotometer. The results of determinations are listed in the table 1.
The difference of shade was computed using the CIE L* a* b* mean values of each shade from both shade guides with the ΔE formula:
ΔE=((L*1-L*2)2 + (a*1 – a*2)2 + (b*1 - b*2)2)1/2,
Where (L*1,a*1,b*1) is the CIE L* a* b* of the shade computed by the spectrophotometer and (L*2,a*2,b*2) is the CIE L* a* b* of the shade perceived by the student.

Table 1. Results for tooth shade determination for patients A, B, C and D.
Table 2. ΔE results obtained for all patients and ΔE mean for each patient and shade guide

The ΔE values are listed in the Table 2. The ΔE values resulting from the ratings of each student can be viewed per patient in Figures 4-7
The ΔE mean was also computed for all patients for each shade guide. The result was similar between the 2 shade guides, Vitapan 3D Master having a ΔE mean of 3.45 and Vita Classic a ΔE mean of 3.59.

Figure 4. ΔE values for patient A.
Figure 5. ΔE values for patient B.

Figure 6. ΔE values for patient C.
Figure 7. ΔE values for patient D.

The IBM SPSS Statistics (Version 19) software was used to statistically compare the results of the students with the spectrophotometer results. A frequencies analysis concluded that the correlation percentage between the determinations of the students and the spectrophotometer is 37.5% for both Vita Classic Shade Guide and Vitapan 3D Master Shade Guide. This can be observed in Table 3 on the first line, frequencies corresponding to the ΔE value “00” and in Table 4 also on the first line, frequencies corresponding to the ΔE value “00”.

Table 3. Frequencies of ΔE values obtained with the Vita Classic Shade Guide
Table 4. Frequencies of ΔE values obtained with the Vitapan 3D Master Shade Guide

The same results can be observed in Fig. 8 and 9.

Figure 8. Frequencies of ΔE values obtained with the Vita Classic shade guide
Figure 9. Frequencies of ΔE values obtained with the Vitapan 3D Master shade guide

DISCUSSION

Finding the correct color for a successful aesthetic treatment is a mandatory requirement.
In 1998 Okubo and al compared the results of using Vita shade guide and a dental colorimeter.6 Tung and collaborators reported that, when using Vita shade guide by experimented dentists, the correlations with the colorimeter determinations tend to be over 60%.7
Studies by Paul and others have shown a correlation of 27% in color reproducibility among practitioners who took the shade with the shade guide for central incisors of 30 patients.8 In the same time, 3 determinations with the spectrophotometer showed a reproducibility of 83%.
Another clinical study conducted by Paul and collaborators revealed that the shade determination for porcelain fused to metal crown by spectrophotometer is superior to visual method with the shade guide.9
Paravina analyzed and compared the arrangement of Vita Classic and Vitapan 3D Master shade guides.10 They concluded that 3D Master key arrangement is more realistic and suggested arranging the Vita Classic shade guide according to brightness. The conclusion was that the use of 3D Master shade guide decreases the possibility of errors and increases the intermediate precision among practitioner’s different determinations.
Dancy and others reported that digital shade match can serve as an alternative to conventional visual methods for restoring anterior teeth with all ceramic crowns.11
A study conducted by Douglas compared the ability to reproduce the color of the target shade tab and concluded that most crowns fabricated by the laboratories in this study, when compared to the prescribed shade tab, were above the clinical threshold for an acceptable shade match under intraoral conditions.12
In a recent clinical study, crowns fabricated using a dedicated spectrophotometer had a significantly better color match and a lower rate of rejection due to shade mismatch compared to crowns fabricated with a conventional shade-matching method.13
In our study, observers were students in the 6-th year of the Faculty of Dentistry. The purpose of this study was the analysis of repeatability determinations made by the students with the 2 shade guides and the correspondence determinations measured by the Vita Easy Shade. The mean ΔE was computed for all patients for each shade guide. The result was similar between the 2 shade guides, Vitapan 3D Master having a ΔE mean of 3.45 and Vita Classic a ΔE mean of 3.59.
The IBM SPSS Statistics (Version 19) software was used to statistically compare the results of the students with the spectrophotometer results. A frequencies analysis concluded that the correlation percentage between the determinations of the students and the spectrophotometer is 37.5% for both Vita Classic Shade Guide and Vitapan 3D Master Shade Guide

CONCLUSIONS

In this study, it can be concluded that the shade matching for the upper central incisor with conventional shade guide highlights a marked variation between observers. The ratings with Vitapan 3D Master shade guide are more accurate. The Vita Easy shade spectrophotometer can be a useful educational tool for the color management in dental schools.
REFERENCES

1. Chu SJ. Clinical steps to predictable color management in aesthetic restorative dentistry. Dental Clinics of North America, 2007;51(2):473-485.
2.Chu SJ. Communicating and verifying tooth shade using the electronic shade matching system. Dental Lab Products Report, sept 2002.
3. Douglas RD. Precision of in vivo colorimetric assessment of teeth. J Prosthet Dent 1997;77:464-70.
4. Paravina R, Powers J. Esthetic color training in dentistry, Mosby 2004(book and CD)
5. J.Brewer, A.Wee, R.Seghi. Advances in color matching. Dental Clinics of North America, 2004; 48(2): 341-58.
6. Okubo SR, Kanawati A, Richards MW, et al. Evaluation of visual and instrument shade matching. J Prosthet Dent 1998;80:642-8.
7. Tung FF, Goldstein GR, Jang S, et al. The repeatability of an intraoral dental colorimeter. J Prosthet Dent 2002; 88:585-90.
8. Paul SJ, Peter A, Pietrobon N, et al. Visual and spectrophotometric shade analysis of human teeth. J Dent Rest 2002;81;578-82.
9. Paul SJ, Peter A, Rodoni L, et al. Conventional visual vs. spectrophotometric shade taking for porcelain-fused-to-metal crowns: a clinical comparison. Int J Periodontics Restorative Dent 2004;24:222-31.
10. Paravina RD, Powers JM, Fay RM. Dental color standards: shade tab arrangement. J Esthet Restor Dent 2001; 13:254-63.
11. Dancy WK, Yaman P, Dennison JB, et al. Color measurements as quality criteria for clinical shade matching of porcelain crowns. J Esthet Restor Dent 2003,15(2):114-21.
12. Douglas RD, Brewer JD. Variability of porcelain color reproduction by commercial laboratories. J Prosthet Dent 2003;90:339-46.
13. Da Silva, Park S, Weber H, et al. Clinical performance of a newly developed spectrophotometric system on tooth color reproduction. The Journal of Prosthetic Dentistry 2008;99(5): 361-8.



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