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Table of Contents   
ORIGINAL RESEARCH  
Year : 2020  |  Volume : 31  |  Issue : 5  |  Page : 712-717
A comparison between visual, digital photography and polarizing filter photography for shade selection


Department of Prosthodontics, A B Shetty Memorial Institute of Dental Sciences, NITTE (Deemed to be University), Deralakatte, Mangalore, Karnataka, India

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Date of Submission29-Mar-2019
Date of Decision29-Apr-2019
Date of Acceptance25-Sep-2020
Date of Web Publication08-Jan-2021
 

   Abstract 


Aim: There is an increased awareness for aesthetically pleasing restorations among patients in current practice. Due to variability in the natural tooth colour, shade selection becomes an intricate procedure. The aim of this study is to determine which of the three named methods is more accurate for shade selection in aesthetic dentistry. Materials and Methods: Two VITAPAN classical shade guides were used for this study. Nine shades were selected from the first shade guide (A1, A2, A3.5, B1, B2, B3, C1, C2, C3) and the number was concealed. Ten selected participants were asked to identify each concealed shade with the second shade guide. Canon 5D camera with ISO 200, shutter speed 1/100 sec, F22 was used for capturing images of the second shade guide. Photoshop CS3 Software was used for developing the digital shade guide. The participants were asked to match the shades from the first shade guide with the prepared digital shade guide. The third photographic shade guide was prepared using a polarised filter on the Canon 5D camera with the same settings. The participants were asked to match shades with the prepared photographic shade guide. Results: Total observations made during the study were 270. Cross table statistical analysis (Chi-square test) done using SPSS 20.0 showed statistically significant difference between conventional and digital photography (P = 0.049). Analysis between digital photography and polarizing filter photography did not reveal a significant association (P = 0.181). Conclusion: Digital photographic method was most accurate among the three shade selection methods. It can be used to obtain aesthetic results.

Keywords: Digital photography, polarizing filter, shade selection

How to cite this article:
Kelkar KC, Dogra ES, Bhat V, Prasad D K, Hegde C. A comparison between visual, digital photography and polarizing filter photography for shade selection. Indian J Dent Res 2020;31:712-7

How to cite this URL:
Kelkar KC, Dogra ES, Bhat V, Prasad D K, Hegde C. A comparison between visual, digital photography and polarizing filter photography for shade selection. Indian J Dent Res [serial online] 2020 [cited 2021 Jan 18];31:712-7. Available from: https://www.ijdr.in/text.asp?2020/31/5/712/306445



   Introduction Top


There has been an increased awareness for aesthetically pleasing restorations among patients. Hence it is a practitioner's responsibility to provide restorations which can merge well with the surrounding natural dentition. Selection of appropriate shade for the prosthesis can be a challenging process. Factors such as shade matching conditions (lighting),[1] education and training, various shade matching tools and knowledge of colour science influence the final dental prosthesis.[2]

Visual shade selection method is one of the most frequently used procedure however it is highly subjective and inconsistent.[1],[3] Fatigue, ageing, colour defective vision, medications and experience may influence the colour perception of an individual.[3] Variation seen during natural daylight can influence the shade matching.[1] The various shade guides used for visual shade selection vary from each manufacturer company.[4],[5] Also, each generation of tabs are dissimilar within a given shade guide company.

Instrumental methods of shade selection include the use of spectrophotometer, colourimeter and photography.[1] The use of these devices involves huge investments resulting in fewer dentists opting for them.[1],[4]

Digital photographs provide an array of colours to choose from. They help in visualizing the morphology, colour and texture of the teeth thus improving the communication between a dentist and a technician.[1],[3],[4],[6] Images produced via photography can be analysed using appropriate software. This provides the value of colours from the whole or part of such images. The tooth shade can be analysed objectively and transmitted via internet to the technician thus giving more information about the restoration to be fabricated.[5]

Polarising filter eliminates glare and reflection seen in an image while increasing colour saturation.[2] It enhances the translucency and allows us to better visualize the real polychromatic nature of teeth.[1],[2]

The purpose of the present study was to determine which among the three named methods i.e., visual shade selection, digital photography and polarising filter photography is better for shade selection in aesthetic dentistry and whether experience influences the ability for accurate shade selection. The null hypothesis for this study considered that there was no significant difference in the shade selection methods under study.


   Materials and Methodology Top


A total of ten observers (five males, five females) were selected based on their work experience comprising of four postgraduate students, three dental technicians and three professors. Each of the observer was asked to perform shade selection according to the following methods:

  1. Visual shade selection
  2. Digital photographic shade selection
  3. Polarizing filter photographic shade selection


For visual shade selection

Two VITAPAN classical shade guides were used for this study. Nine shades were selected from the first shade guide (A1, A2, A3.5, B1, B2, B3, C1, C2, C3) and the shade number was concealed. The selected tabs depicted the most common shades used in a clinical setup. For the control shade guide, same shade tabs were selected from the second VITAPAN classical shade guide.

Each observer was given one concealed shade tab in a random sequence and was asked to identify the shade from the control shade guide (in natural daylight). No time limit was imposed for the matching. Each observer made nine observations giving a total of 90 observations from this method.

For digital photographic shade selection

Digital photographs of each selected shade tab from the control group were captured individually to prepare a digital photographic shade guide. A Canon 5D camera was mounted on a tripod stand at a height of two feet and the shade tabs were kept at 30 cms from the camera. A standardised camera setting of ISO 200, shutter speed 1/100 seconds, F22 were used for capturing all photographic images. The lighting conditions while capturing these images comprised of a mixture of daylight and overhead light tubes and camera inbuilt flash. Using Photoshop CS3 software, a digital photographic control shade guide was prepared. For capturing images of the concealed shade tabs, each tab was placed at right central incisor position in a typhodont with adjacent central incisor missing. Thus, nine images of typhodont with concealed shade tab in the right central incisor position were captured and transferred to Photoshop Cs3 software. The prepared digital control shade guide was layered above each captured photograph of the concealed shade tab. Thus nine photoshop document files (PSD) were developed for matching.

For polarizing filter photographic shade selection

A circular polarizing filter was attached to the Canon 5D camera. Photographs of control shade tab were captured using polarising filter to prepare polarised shade guide.

Images of typhodont with concealed shade tab at right central incisor position and missing adjacent central incisor were taken. The photographs were captured with the same camera settings and lighting conditions standardised for digital photographic shade selection. These nine images were transferred to photoshop Cs3 software and the prepared polarised shade guide was layered on each photograph. Thus nine PSD files were developed for matching for the polarising method.

Verbal instructions with a demonstration for computerised shade matching was given to educate the ten observers and introduce them to Photoshop Cs3 software. The 18 PSD files (nine digital photographs, nine polarizing filter photographs) were coded as per concealment of the shade tabs. Each observer was presented with a PSD file and asked to match the missing central incisor with the adjacent right central incisor from the shade guide provided above. The observer could move around the control shades and even overlap two shades for selection. Once the shade was matched, the observation was noted, and the next file was presented for shade selection. Each observer made nine digital photographic observations and nine polarized filter photographic observations giving a total of 180 observations.

The cross table statistical analysis was done using Chi-square test in SPSS 20.0 software.


   Results Top


A total of 270 observations were made during this study. In visual shade selection method, 50% of the observations were correct. In the digital photographic method of shade selection, the correct percentage of shade matching was 63.3% whereas for polarizing filter photographic shade selection the correct percentage was 55.6% [Table 1]. The cross table statistical analysis showed a significant difference between the visual and the digital photographic shade selection method (p = 0.049). In comparison with the visual method, an increase of 5.5% was observed in polarizing filter photography (p = 0.275). Analysis between digital photography and polarizing filter photography did not reveal a significant association (p = 0.181). In the analysis, level of significance is taken as 5% and level of confidence is taken as 95%. For comparison of observations among different group of shade selection Chi square test is used with 5% level of significance. Overall confidence interval is 50.42% to 62%. For visual group the 95% confidence interval lies between 39.67% to 60.33%. For digital group the 95% confidence interval lies between 53.3% to 73.3% and for polarized filter group it lies between 45.2% to 65.8%.
Table 1: Number of correct and incorrect observations in three methods (original)

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In the study Reliability Index for the ten observers was calculated to be 0.5. The individual matching ability of each observer is given in [Table 2]. Observer one (66.6%) and five (66.6%) had the most correct observations in visual method. The least accurate shade matching was done by observer four (11.1%). In digital photographic method, observer six was most accurate with all correct observations. Most of the observers achieved an accuracy of more than 50% in this method. With the use of polarising filter photographic method, observer ten had the most accurate observations (100%).
Table 2: Individual Matching Ability of each Observer (Original)

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The professors and postgraduate students had an increase in the correct number of observations in digital shade selection methods as opposed to visual method whereas the dental technicians showed a better shade matching ability in the visual shade selection method. As the sample size is very small no statistical test for the significant increase is carried out and only the observations are noted down.


   Discussion Top


The study of colour is an integral part of esthetic dentistry. The colour of an object is determined by the nature of the light source illuminating an object, its spectral reflectance[1] properties and nature of human colour perception.[4] Ideal colour temperatures for shade matching ranges from 5000 k to 7500 k.[7] However, these conditions vary in natural daylight. Various shade selection methods are being practised by dental professionals worldwide although the most frequently used is visual shade matching. It depends on an individual's perception of shade selection and is influenced by the light source, ageing, eye fatigue, medication, colour vision deficiencies and dehydration of the tooth. In this study, 50% of the observers matched the shades correctly for visual shade selection method. In a study done by Jared et al., 43% of the shades were matched accurately by the observers. Schropp et al. evaluated the efficacy of digital photographs and graphic computer software for colour matching with conventional visual matching in a simulated clinic. They observed 32% correct visual shade matches.
Figure 1: VITAPAN classical shade tab randomisation done

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Figure 2: Visual shade selection

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Figure 3: Digital photographic shade selection

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Figure 4: Polarizing filter photography shade selection

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Figure 5: Observer performing shade matching

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Figure 6: Overlapping of shade tabs during digital shade matching

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In the present study, nine shade tabs were selected from the VITAPAN classical shade guide according to the most frequently used shades in a clinical setup. Use of a limited number of shade tabs from the same manufacturer could have resulted in an increased number of correct observations. Several studies have concluded that the use of human extracted teeth[5] or human subjects[4] influences the visual shade selection.

Instrumental methods for shade matching include the use of a spectrophotometer, colourimeter and digital photography. Spectrophotometers and colourimeters are complex, expensive and not necessarily associated with higher accuracy. Hence fewer dentists opt for these options.

The use of digital photography in shade selection helps in analysing the morphology, colour and texture of the adjacent structures to fabricate an accurate prosthesis. It bridges the lack of communication between the dentist and the technician. Digital photographic shade selection procedure showed an increase of 13% as compared to visual shade selection. Our results are in confluence with Jared et al. (61.1%) and Schropp et al. (66%). The observers in this study preferred the computerized methods as it allowed them to see the shade guide and the dentition adjacent to the missing tooth on the same screen. The shade tabs could be moved around the computer screen and even overlapped to obtain optimum results.

The use of a polarizing filter enhances the optical properties of a shade tab by eliminating the reflected light. Thus, it gives a matte effect to the captured images.[1],[2] In this study 55.5% of the observations were matched correctly by the observers. There was an increase of 5.5% as opposed to visual shade selection and a decrease of 7.5% in correct observations as compared to the digital photographic method.

There was a variability in shade selection between each observer in visual shade matching. Dental technicians showed a better shade matching ability in this method. This may be due to the experience of an individual. Our results are in accordance with a study done by McMaugh et al. where the mean score values observed by technicians was higher in comparison to the students and practitioners.[8] Çapa et al. evaluated the factors affecting shade matching in dentists, dental staff members and laypeople and observed a higher success rate in dental technicians due to their experience in routinely performing porcelain shade matching.[9] The highest percentage of accuracy by observers one and five was 66.6% in visual shade selection whereas in digital and polarizing filter photographic shade selection 100% accuracy was shown by observer six and ten respectively.

Previous studies have stated the influence of gender on shade perception with females having a superior shade matching ability than males.[10],[11] In this study, shade matching was not influenced by the gender of an observer. Similar findings were seen by Clary et al. Darker shades are better perceived by the human eye.[3] In this study, most accurately perceived shade by the observers was B3 [Table 3].
Table 3: Number of times shade were matched correctly in the three methods (original)

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Education and experience aids in improved shade matching skills.[7] The professors and technicians in this study showed better shade matching ability than the postgraduate students in visual shade matching technique. Adequate knowledge about colour science and training for shade matching will help in increasing the shade selection skills.[12]

One of the limitations of this study was matching few shade tabs of the same company with each other which may have resulted in higher accuracy.[5] The observers had no time limitation for each of the shade selection methods which could have resulted in eye fatigue. Also, increasing the number of observations in each shade selection method could have improved the matching skills of each observer.


   Conclusion Top


Digital photographic shade selection method was most accurate among the three-shade selection methods. It provides better communication between a clinician and technician and can be used to obtain optimum aesthetic results.

Within the parameters of this study, a new polarizing filter shade guide was prepared. However, the use of polarising filter did not significantly influence the shade selection as compared to digital photographic shade selection and visual shade selection methods.

Shade matching when regularly practised can enhance a clinician's shade selection skills. Thus, education and training may improve an individual's shade matching abilities.

Acknowledgement

This manuscript has been read and approved by all the authors, requirements for authorship have been met, and each author believes that the manuscript represents honest work.

Key Messages

The study aims to identify which shade selection method provides more accurate results. It was observed that education and experience aids in accurate shade selection. The use of a polarising filter during photography enhances the optical properties of the shade tabs used.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Sampaio CS, Gurrea J, Gurrea M, Bruguera A, Atria PJ, Janal M, et al. Dental shade guide variability for hues B, C, and D using cross-polarized photography. Int J Periodontics Restorative Dent 2018;38(Suppl):s113-s8.  Back to cited text no. 1
    
2.
Gurrea J, Gurrea M, Bruguera A, Sampaio CS, Janal M, Bonfante E, et al. Evaluation of dental shade guide variability using cross-polarized photography. Int J Periodontics Restorative Dent 2016;36:e76-81.  Back to cited text no. 2
    
3.
Schropp L. Shade matching assisted by digital photography and computer software. J Prosthodont 2009;18:235-41.  Back to cited text no. 3
    
4.
Miyajiwala JS, Kheur MG, Patankar AH, Lakha TA. Comparison of photographic and conventional methods for tooth shade selection: A clinical evaluation. J Indian Prosthodont Soc 2017;17:273-81.  Back to cited text no. 4
[PUBMED]  [Full text]  
5.
Jarad FD, Russell MD, Moss BW. The use of digital imaging for colour matching and communication in restorative dentistry. Br Dent J 2005;199:43-9.  Back to cited text no. 5
    
6.
Tam WK, Lee HJ. Accurate shade image matching by using a smartphone camera. J Prosthodont Res 2017;61:168-76.  Back to cited text no. 6
    
7.
Clary JA, Ontiveros JC, Cron SG, Paravina RD. Influence of light source, polarization, education, and training on shade matching quality. J Prosthet Dent 2016;116:91-7.  Back to cited text no. 7
    
8.
McMaugh D. A comparative analysis of the colour matching ability of dentists, dental students, and ceramic technicians. Aust Dent J 1977;22:165-7.  Back to cited text no. 8
    
9.
Çapa N, Kazazoğlu E, Çalikkocaoğlu S. Evaluating factors that affect the shade-matching ability of dentists, dental staff members and laypeople. J Am Dent Assoc 2010;141:71-6.  Back to cited text no. 9
    
10.
Gasparik C, Grecu AG, Culic B, Badea ME, Dudea D. Shade-matching performance using a new light-correcting device. J Esthet Restor Dent 2015;27:285-92.  Back to cited text no. 10
    
11.
Jasinevicius TR, Curd FM, Schilling L, Sadan A. Shade-matching abilities of dental laboratory technicians using a commercial light source. J Prosthodont 2009;18:60-3.  Back to cited text no. 11
    
12.
Parameswaran V, Anilkumar S, Lylajam S, Rajesh C, Narayan V. Comparison of accuracies of an intraoral spectrophotometer and conventional visual method for shade matching using two shade guide systems. J Indian Prosthodont Soc 2016;16:352-8.  Back to cited text no. 12
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Correspondence Address:
Dr. Vinaya Bhat
Department of Prosthodontics, A B Shetty Memorial Institute of Dental Sciences, Deralakatte, Mangalore - 575 018, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijdr.IJDR_286_19

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