Introduction {#sec1-1}
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Exact determination of tooth shade is essential to achieve esthetic dental restorations. It involves color analysis, communication to technician, interpreting color information, building the restoration, and color confirmation before cementation in a patient\'s mouth.\[[@ref1]\] Selection of color may also vary according to factors such as light source, surrounding tissues, and patient\'s make up. However, one of the most crucial factors in determination of tooth color is a clinician\'s color perception.\[[@ref1][@ref2]\]

There are two methods of shade determination: comparison with shade tabs and shade measurement with electronic devices. Despite recent advances like spectrophotometry and colorimetry, shade guides remain the most popular options for tooth color selection. Various shade guides available for use in dentistry are Vitapan Classical, Ivoclar Vivadent Chromascop, and Vitapan 3D master. Various tools have been used to reduce variability in color selection among dental professionals. Spectro shade micro (MHT), Vita easy shade, and Easyshade Compact are some of the latest improvements in shade matching. Within the oral cavity, resolution of digital colorimeters has been found to be similar to the human eye.\[[@ref2]\] A combination of visual methods and technology-based tools minimizes the subjectivity of visual color assessment. This also provides an easy communication of accurate color analysis to the laboratory for restoration\'s shade resulting in a good esthetic outcome.

Even for a dentist with normal color vision, color matching is complicated by the individual\'s own differences in color observation. In the United States, the prevalence of color blindness in dental students was found to be 7.8%. Color vision deficiencies may result in impaired shade matching ability. This is more pronounced in the yellow region of the optical spectrum that is relevant for shade matching in dentistry.\[[@ref3]\] A smaller percentage of population in South East Asia is known to be affected by these disorders. Around 1.69% females and 8.73% males have been color blind in India.\[[@ref4]\]

The teaching of color sciences is multidisciplinary across dental colleges in the country. Three dimensions of color, Munsell system, metamerism, and fluorescence are taught in the form of lectures in the first year of dental training.\[[@ref5]\] The Department of Operative Dentistry and Department of Prosthodontics provide lectures as well as clinical demonstration on shade matching techniques while teaching about esthetic restorative materials, partial dentures, and complete dentures.\[[@ref5][@ref6]\]

Successful shade matching is a complex and multidimensional process that involves the cognitive ability of the students.\[[@ref7]\] The development of shade matching ability among dental students after years of their training is indispensable. There is also a paucity of literature on this subject. Therefore, the aim of the present study was to assess and compare the shade matching ability of undergraduate dental students in various years of dental education.

Materials and Methods {#sec1-2}
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A cross-sectional study was conducted among Bachelor of Dental Surgery (BDS) students from September 2018 to October 2018 (24^th^ August 2018). Ethical approval was obtained from the Institutional Ethical Committee of Manav Rachna Dental College, Faridabad.

The students were selected on the basis of verbal consent and on a first come first participate basis. Students with confirmation of color vision blindness using Ishihara test with 24 plates were excluded from the study.

Enrolled participants were given two exercises to assess shade matching ability through a proforma specifically designed for the study. The exercises were performed in the airy outdoors under natural light in the afternoon. To neutralize the effect of interference from the surroundings on color perception, the participants were asked to look at the shade for 5 s to prevent accommodation reflex toward the red and yellow colors of the color spectrum.\[[@ref5]\] The after-image formation by looking continuously at an object of one color was minimized by viewing a grey color background.\[[@ref6]\]

In the first exercise, basic shade matching ability of the students was assessed by shade tab matching in a bench setting. The participants were given a new Vitapan Classical shade guide (Vita Zahnfabrik, Bad Sackingen, Germany) and three blinded shade tabs. The three blinded shade tabs were A3, B1, and D2. The participants were asked to match the blinded shade tab with its corresponding tab from the shade guide and fill in the proforma. In the second exercise, the participant was asked to perform intraoral tooth color matching in order to evaluate the ability for shade matching of the participants in a working on patient setup. The participants were requested to match tooth shade using Vitapan shade guide for one central incisor in three selected patients and answer in the proforma accordingly. Teeth were kept wet to limit the influence of surface morphology while evaluating for hue and chroma.

Patient 1 had normal tooth shade with no variations of color. Patient 2 had a moderate variation in tooth shade from on the labial surface. Patient 3 had severe variations in tooth shade with the presence of hypo-calcification lines on the labial surface. The cases were identified with the help of a prosthodontist.

Vita easyshade compact was used to perform spectrophotometric measurements to determine the correct shade match for the three reference patients who were used in the Exercise 2. Color coordinates CIE L\*a\*b\* were obtained for the tooth area and shade tab using the database of dental spectrophotometer. The color difference ΔE\* between three tabs and the natural tooth were calculated using the equation by Da Silva *et al*. 2008\[[@ref7]\] and Swift *et al*. 1994.\[[@ref8]\]

ΔE\* = {(L\*target tooth − L\*shade guide)^2^ + (a\* target tooth − a\* shade guide)^2^ + (b\* target tooth - b\* shade guide)^2^}½

For data analysis, in present study, the shade tab equivalent with a ΔE\* ≤ 3.7 were considered as clinically appropriate color matches.

Both the exercises were marked separately. The data from participants were tabulated on Microsoft excel. The participants answering correctly for all three shade matches were categorized as excellent and those with two correct matches were categorized as good. Participants having one correct shade match were designated as fair while those with no match were categorized as poor. Statistical analysis was done using SPSS software, version 21. The frequency of correct responses was calculated and the data was compared across each of five years using Chi-square test. The level of significance was taken as *P* value \< 0.05 with 95% confidence interval.

Results {#sec1-3}
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A total of 150 students participated in the study with 30 participants from each year. There were 37 male and 113 female participants. For Exercise 1, 53 participants (35.30%) showed fair color matching ability in bench setting, 26.70% (*n* = 40) showed good ability, 22.70% (*n* = 34) demonstrated an excellent ability, whereas 15.30% (*n* = 23) had a poor ability of color matching. According to year-wise ability of students in Exercise 1, 40% of first-year students (*n* = 12) obtained fair scores, 23.30% obtained good scores, and 10% obtained excellent scores. \[[Table 1](#T1){ref-type="table"}\] A total of 8 first-year students (26.70%) demonstrated poor scores in Exercise 1. For second, third, and final years, the number of students obtaining fair, good, excellent, and poor score level was 36.70%, 26.70%, 10%, and 26.70% for the second year, 46.70%, 23.30%, 26.70%, and 3.30% for third year, and 30%, 23.30%, 33.30%, and 13.30% for final year students, respectively. In the interns, 23.30% participants had fair scores, 36.70% had good scores, 33.30% had excellent scores, and 6.70% had poor scores. Difference in shade matching ability among years of dental education was statistically significant \[[Table 1](#T1){ref-type="table"}\].

###### 

Distribution of study participants according to their performance in Exercise 1

                   Year1            Year2        Year3        Year4        Year5        Total
  ---------------- ---------------- ------------ ------------ ------------ ------------ -------------
  Poor             8 (26.7%)        8 (26.7%)    1 (3.3%)     4 (13.3%)    2 (6.70%)    23 (15.3%)
  Fair             12 (40%)         11 (36.7%)   14 (46.7%)   9 (30%)      7 (23.3%)    53 (35.3%)
  Good             7 (23.3%)        8 (26.7%)    7 (23.3%)    7 (23.3%)    11 (36.7%)   40 (26.7%)
  Excellent        3 (10%)          3 (10%)      8 (26.7%)    10 (33.3%)   10 (33.3%)   34 (22.70%)
  Total            30               30           30           30           30           150
  Chi-square (P)   21.117 (0.049)                                                       

For Exercise 2, where clinical color matching ability of the students was analyzed, 34% (*n* = 51) obtained fair scores, 33.30% (*n* = 50) obtained good scores, 26% (*n* = 39) obtained excellent scores, whereas 6.70% (*n* = 10) of the participants had poor scores \[[Table 2](#T2){ref-type="table"}\].

###### 

Distribution of study participants according to their performance in Exercise 2

  Exercise 2   YEAR OF DENTAL TRAINING              Total                                               
  ------------ ------------------------------------ ------------ ------------ ------------ ------------ ------------
  Poor         4 (13.3%)                            2 (6.7%)     2 (6.7%)     2 (6.7%)     0 (0%)       10 (6.70%)
  Fair         13 (43.3%)                           10 (33.3%)   11 (36.7%)   11 (36.7%)   6 (20%)      51 (34%)
  Good         11 (36.7%)                           14 (46.7%)   11 (36.7%)   6 (20%)      8 (26.7%)    50 (33.3%)
  Excellent    2 (6.7%)                             4 (13.3%)    6 (20%)      11 (36.7%)   16 (53.3%)   39 (26%)
  TOTAL        30                                   30           30           30           30           150
               Chi-square=26.920; *P* value=0.008                                                       

According to the year of study, the percentage of individuals with fair, good, excellent, and poor scores, respectively, were 43.30%, 36.70%, 6.70%, and 13.30% for first-year; 33.30%, 46.70%, 13.30%, and 6.70% for second year; 36.70%, 36.70%, 20%, and 6.70% for third years, and 36.70%, 20%, 36.70%, and 6.70% for the fourth year. None of the interns had a poor score in this exercise while 20% of interns obtained fair scores, 26.70% obtained good scores, and 53.30% obtained excellent scores. Difference in clinical color matching ability among students according to years of dental training was found to be statistically significant \[[Table 2](#T2){ref-type="table"}\].

According to case-wise responses of participants to Exercise 2, 36% of the participants obtained fair scores for Patient one, 25% had good scores, 29% had excellent scores, and 10% had poor scores. For Patient two, 33% of participants obtained fair scores, 25% had good scores, 29% and 13% had excellent and poor scores, respectively. For Patient three, 5% of the participants had poor scores, 26% obtained fair scores, 28% good scores, and 41% obtained excellent scores \[[Table 3](#T3){ref-type="table"}\].

###### 

Distribution of study participants according to the patient-wise responses

  Scores      Patient 1   Patient 2   Patient 3
  ----------- ----------- ----------- -----------
  Poor        10%         13%         5%
  Fair        36%         33%         26%
  Good        25%         25%         28%
  Excellent   29%         29%         41%

Year-wise distribution of participants according to case-wise acceptable answers showed that 18% of both first and second year participants gave acceptable answers about tooth shade for Patient one and 22, 21, and 23% of participants from third, fourth, and fifth year, respectively, gave correct answers for this case. For Patient two, 15% of first years, 20% of second years, 17% of third years, 23% of final years, and 25% of interns gave a correct answer. For Patient three, 11% of the participants from first year, 18% of participants from second, third, and fourth year, and 34% from interns gave an acceptable response \[[Table 4](#T4){ref-type="table"}\].

###### 

Year-wise distribution of participants according to patient-wise acceptable answers

              Year 1   Year 2   Year 3   Year 4   Year 5
  ----------- -------- -------- -------- -------- --------
  Patient 1   18%      18%      22%      21%      23%
  Patient 2   15%      20%      17%      23%      25%
  Patient 3   11%      18%      18%      18%      34%

Discussion {#sec1-4}
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Clinical practice today is largely governed by a patient\'s perspective of esthetics. Shade matching to adjacent teeth is one of the important aspects of a successful restoration. Hence, correct tooth color determination is a crucial step in the successful planning and performing dental treatments.\[[@ref9]\] The standard method for clinical shade matching is the human eye along with comparative analysis among operators or auxiliary personnel. Shade matching is a much more complicated task than it may look like, especially with respect to hue, value, and chroma. However, the color determination ability improves over time through training, exercise, and experience.\[[@ref10]\]

Students for the present study were selected from all five years of dental education system in India. First-year students are not exposed to a formal knowledge or clinical experience of shade matching and, hence, performed the exercises based on the individual\'s visual perception. Second-year students have some form of theoretical knowledge but no clinical experience, whereas third year onwards the students have wider exposure to both patient contact and clinical color matching.

The present study showed an improvement in shade matching ability with the level of dental education which was in contrast to a similar study done on the shade matching ability of dental students in the US by Jaju *et al*.\[[@ref11]\] In the latter study, tooth color matching ability in bench setting is not significantly associated with year of education. In addition, it has been shown that there is no relationship between shade matching ability and informative teaching.\[[@ref12]\] However, in the present context, dental education is a synthesis of both informative and practical-based teaching. Theoretical concepts in teaching are indispensable for improvement of understanding in students before practical learning; therefore, a combination of both approaches is important. This is emphasized by an increase in both fundamental and clinical color matching abilities across years of dental education.

Tooth color matching fundamentals are first discussed theoretically in the second year in the Indian dental education system. The Operative and Prosthodontic departments provide lectures on shade matching techniques and protocol when discussing composite materials, porcelain, removable, partial, and complete dentures. The application of this knowledge is reinforced in preclinical and clinical sessions, and skills are assessed as a component of students\' competency requirements in both third and fourth years. Students may also present and discuss color sciences when they present comprehensive treatment cases in the third and fourth years. This accounts for an increase in acceptable scores for the bench test and clinical setting from second year to third year.\[[@ref13]\]

The present study also showed that there is an increase in fundamental color matching ability with years of education. It can also be said that theoretical teaching has an impact on basic color matching ability. There is no theoretical teaching about color matching in the third year of dental education in India; only practical application is introduced based on the already existing knowledge imparted in the second year. Therefore, there is a transient change in percentage of poor and acceptable scores for fundamental color matching test. This is in contrast with the findings from the similar study conducted by Jaju *et al*. in the US.\[[@ref11]\]

Further, there was a decrease in number of poor scores from first year to second year and from fourth year to fifth year. In addition, there was a significant difference between class years on students\' ability to shade match, which improved with increasing years of education. These results were not in agreement with the previous study by Jaju *et al*. in the U.S. dental students.\[[@ref11]\] These results are a representation of the participant\'s cumulative dental knowledge and fundamental color matching ability. An increase in exposure to clinical cases and competencies and skills testing at the end of fourth year in Indian dental education system adds to enhanced exercise and experience with increase in years of education.

The present study showed better scores with respect to Exercise 2 as compared to Exercise 1. These results suggest that clinicians are more particular of shade matching in a clinical scenario than under controlled *in vitro* conditions.\[[@ref14][@ref15]\]

It is well-known that the color of the same shade tab from different shade guides for a system can have differences. In this study, the shade tab matches are the identical shade tabs in the complete shade guide. The match was confirmed with a dental spectrophotometer, and the color difference ΔE\* value between each target tab and corresponding tab in a complete shade guide system was less than 0.5---a color difference that is imperceptible.\[[@ref11][@ref16]\]

Color difference assessment has been proven to be a learned trait which was substantiated by a study done by Ramesh *et al*. in which dental surgeons were more accurate in perceiving color changes as compared to laypersons.\[[@ref17]\] Another study by Majeed *et al*. showed that postgraduate trainees were the most skillful in color matching because of their interest in continuing education and grooming.\[[@ref18]\] Alfouzan *et al*. also observed that there was a significant difference between the pre- and post-test values for the students\' dental shade matching qualities for all of the test groups as compared to control groups.\[[@ref19]\]

The results of the present study support the efficacy of clinical expertise for clinical shade matching. Thus, educational outcomes need to include a lifelong learning with emphasis on dental materials, technology, and technique-enhancements for optimal results for all patients.\[[@ref20][@ref21][@ref22]\] The findings from this study could be used to help identify and support students/clinicians who might struggle with color interpretation and stress present in clinical environment.\[[@ref23]\] Patient\'s expectations for highly aesthetic outcomes in dentistry continue to increase with technological advancements in dentistry. Further, there is an increased desire of esthetics in both the genders. It has impact on the psychology of the patient which affects family health directly. Therefore, further studies on the need and impact of color science in dental education are required.

Conclusion {#sec1-5}
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The present study showed that the clinical performance of dental students for shade matching improved with increasing years of dental education. In addition, better outcomes were seen in a clinical setting as compared to *in vitro* conditions in Exercise 1. Thus, it can be concluded that, though the color matching ability is more of an individual perception, dental knowledge and clinical experience with increasing years of education lead to better clinician performance and better esthetic outcomes for the patient.

Declaration of patient consent {#sec2-1}
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The authors certify that they have obtained all appropriate patient/participant consent forms. In the form, the patients/participants have given their consent for their images and other clinical information to be reported in the journal. The patients/participants understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship {#sec2-2}
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Nil.

Conflicts of interest {#sec2-3}
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There are no conflicts of interest.
