DENTAL SHADE MATCHING. THE COMPARISON OF VISUAL SHADE MATCHING ABILITIES WITH VITA EASYSHADE® AND DENTAL SHADE RECOGNITION SMARTPHONE APPLICATIONS

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Angela Sarah Haack

V, 13

DENTAL SHADE MATCHING.

THE COMPARISON OF VISUAL SHADE MATCHING

ABILITIES WITH VITA EASYSHADE® AND DENTAL

SHADE RECOGNITION SMARTPHONE APPLICATIONS

Master’s Thesis

Supervisor

Dr. Gediminas Skirbutis

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LITHUANIAN UNIVERSITY OF HEALTH SCIENCES MEDICAL ACADEMY

FACULTY OF ODONTOLOGY DEPARTMENT OF PROSTHODONTICS

DENTAL SHADE MATCHING.

THE COMPARISON OF VISUAL SHADE MATCHING ABILI-TIES WITH VITA EASYSHADE® AND DENTAL SHADE RECOGNITION SMARTPHONE APPLICATIONS

Master’s Thesis

The thesis was done

by student ……… Supervisor ………...

(signature) (signature)

……… ………

(name surname, year, group) (degree, name surname)

……… 20…… ………20……

(day/month) (day/month)

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3 EVALUATION TABLE OF CLINICAL–EXPERIMENTAL MASTER’S THESIS

Evaluation: ...

Reviewer: ...

(scientific degree, name and surname)

Reviewing

date: ...

No. MT parts MT evaluation aspects

Compliance with MT requirements and

evalu-ation

Yes Partially No

1

Summary (0.5 point)

Is summary informative and in compliance with

the thesis content and requirements? 0.3 0.1 0

2 Are keywords in compliance with the thesis es-_sence? 0.2 0.1 0

3 Introduc-tion, aim and tasks (1 point)

Are the novelty, relevance and significance of the

work justified in the introduction of the thesis? 0.4 0.2 0

4 Are the problem, hypothesis, aim and tasks _{formed clearly and properly?} 0.4 0.2 0

5 Are the aim and tasks interrelated? 0.2 0.1 0

6

Review of literature (1.5 points)

Is the author’s familiarization with the works of

other authors sufficient? 0.4 0.2 0

7

Have the most relevant researches of the scientists discussed properly and are the most important

re-sults and conclusions presented? 0.6 0.3 0

8 Is the reviewed scientific literature related enough

to the topic analysed in the thesis? 0.2 0.1 0

9 Is the author’s ability to analyse and systemize the _{scientific literature sufficient?} 0.3 0.1 0 10

Material and methods (2 points)

Is the research methodology explained

comprehensively? Is it suitable to achieve the set

aim? 0.6 0.3 0

11 Are the samples and groups of respondents formed and described properly? Were the selec-tion criteria suitable?

0.6 0.3 0

12 Are other research materials and tools (question-naires, drugs, reagents, equipment, etc.) described properly?

0.4 0.2 0

13 Are the statistical programmes used to analyse da-ta, the formulas and criteria used to assess the lev-el of statistical rlev-eliability described properly?

0.4 0.2 0

14

Results (2 points)

Do the research results answer to the set aim and

tasks comprehensively? 0.4 0.2 0

15 Does presentation of tables and pictures satisfy

the requirements? 0.4 0.2 0

16 Does information repeat in the tables, picture and

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17 Is the statistical significance of data indicated? 0.4 0.2 0

18 Has the statistical analysis of data been carried out _properly? 0.4 0.2 0 19

Discussion (1.5 points)

Were the received results (their importance, drawbacks) and reliability of received results

assessed properly?

0.4 0.2 0

20 Was the relation of the received results with the _{latest data of other researchers assessed properly?} 0.4 0.2 0

21 Does author present the interpretation of results? 0.4 0.2 0

22 Do the data presented in other sections (introduc-_{tion, review of literature, results) repeat?} 0 0.2 0.3 23

Conclu- sions (0.5 points)

Do the conclusions reflect the topic, aim and tasks

of the Master’s thesis? 0.2 0.1 0

24 Are the conclusions based on the analysed materi-_{al? Do they correspond to the research results?} 0.2 0.1 0

25 Are the conclusions clear and laconic? 0.1 0.1 0

26

References (1 point)

Is the references list formed according to the

requirements? 0.4 0.2 0

27 Are the links of the references to the text correct? Are the literature sources cited correctly and

pre-cisely? 0.2 0.1 0

28 Is the scientific level of references suitable for _{Master’s thesis?} 0.2 0.1 0 29 Do the cited sources not older than 10 years old form at least 70% of sources, and the not older

than 5 years – at least 40%? 0.2 0.1 0

Additional sections, which may increase the collected number of points

30 Annexes Do the presented annexes help to understand the _{analysed topic?} +0.2 +0.1 0

31

Practical recommen-

dations

Are the practical recommendations suggested and

are they related to the received results? +0.4 +0.2 0

General requirements, non-compliance with which reduce the number of points

32

General require- ments

Is the thesis volume sufficient (exclud-ing annexes)?

15-20 pages

(-2 points) (-5 points) <15 pages 33 Is the thesis volume increased artificial-_ly? -2 points -1 point

34 Does the thesis structure satisfy the

re-quirements of Master’s thesis? -1 point -2 points

35 Is the thesis written in correct language, _{scientifically, logically and laconically?} -0.5 point -1 points

36 Are there any grammatical, style or

computer literacy-related mistakes? -2 points -1 points

37 Is text consistent, integral, and are the

volumes of its structural parts balanced? -0.2 point -0.5 points

38 Amount of plagiarism in the thesis. >20%

(not evaluated) 39

Is the content (names of sections and sub-sections and enumeration of pages) in compliance with the thesis structure and aims?

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5

40

Are the names of the thesis parts in compliance with the text? Are the titles of sections and sub-sections distin-guished logically and correctly?

-0.2 point -0.5 points

41 Was the permit of the Bioethical

Committee received (if necessary)? -1 point

42 Are there explanations of the key terms

and abbreviations (if needed)? -0.2 point -0.5 points

43 Is the quality of the thesis typography (quality of printing, visual aids, binding) good?

-0.2 point -0.5 points

*In total (maximum 10 points): *Remark: the amount of collected points may exceed 10 points.

Reviewer’s comments: ___________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ _________________________________ ________________________________

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SUMMARY

Purpose

The purpose of this study is to determine and compare the accuracy and the reliability of the visual dental shade matching method with a specialized shade matching device and two dental shade matching smartphone applications.

Materials and methods

For the visual dental shade matching, 204 dental students were asked to match dental shade tabs as well as extracted teeth. The same shade tabs and extracted teeth were also examined by a spectro-photometer and two smartphone applications. The generated results were compared for accuracy and reliably. Results were evaluated using Microsoft Excel and IBM SPSS 23. Statistical signifi-cance was accepted at p<0.05. For the accuracy, mean values, standard deviations and t-tests were calculated. Inter-rater and the intra-rater reliability was calculated using mean and standard devia-tion. Eab was calculated defining the distance between a selected and the actual dental shade.

Results

VS matched shade tab 1, 2, and 3 respectively with 52.5% (73%), 49.0% (64.2%), and 47.5% (70.1%), INST matched with 61.5% (61.5%), 67.3% (88.5%), and 100% (100%) perfectly (accord-ing to the threshold). DTSR recognized shade tab 3 with 100% (100%) and CHROM shade tab 1, 2, and 3 with 51% (51%), 0 (41.2%), and 0 (62.7%) respectively.

Conclusion

Instrumental shade matching revealed the best results followed by visual shade matching. The accu-racy and repeatability of CHROM increases significantly with the introduction of the threshold val-ue. Both smartphone applications cannot be used in a serious shade matching process yet.

Keywords: shade guide, shade matching, visual, instrumental, spectrophotometer, smartphone

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LIST OF ABBREVIATIONS

Eab Difference of color measurements between two dental shades calculated

ac-cording to Lab

CHROM Smartphone application Chromatcher

CIE Commission Internationale de l’Eclairage

Df Degree of freedom

DTSR Smartphone application Dental tooth shade recognition

ET Extracted tooth

IBM SPSS 23 Statistical software from the company IBM version 23

INST Instrumental method (spectrophotometer, Vita Easyshade®)

IOS Software used by Apple phones

Lab Tooth color system using lightness, the distribution on a red-green and

yel-low-blue scale

LCh Tooth color system using lightness, chroma and hue

M Mean

RGB Red, green, blue color space

SD Standard deviation

SMART Both smartphone application considered

ST Shade tab

VS Visual method

Vita 3D Master® Dental shade guide of the company Vita Zahnfabrik Vita Classical® Dental shade guide of the company Vita Zahnfabrik

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INTRODUCTION

Color matching and precise color reproduction of as natural looking dental prosthesis is still one of the most crucial steps in prosthodontics (1,2). One of the major problems is the correct selection of a tooth color as close to the natural adjacent tooth color as possible. According to a study conducted by Gómez-Polo et al. (2014), the matched tooth color is the major aspect considered by the patient when judging the quality and satisfaction of the prosthesis (3). However, several studies have found that most patients are unhappy with the appearance of their dental prosthesis which is mostly caused by a non-matching tooth color (4–6). This emphasizes the importance of focusing on the matching process. Shade matching can be divided into visual or instrumental shade matching. Visual shade matching faces certain inert obstacles such as the gender or the experience level of the observer but also external influencing factors such as the lightening of the environment. Altogether, this makes the visual shade matching process very subjective and very unpredictable (7–9). To overcome the subjectivity and achieve standardized, reliable and accurate color measurements and matches, den-tal color matching devices have been introduced into the denden-tal market and have been available for daily practices (10,11). The available devices range from digital cameras to spectrophotometer (12– 14). Those shade matching devices have been tested in several studies for their accuracy and relia-bility (14). Many of those studies come to the conclusion that shade matching devices outperform the visual shade matching method (10,15–18). However, the visual shade matching method is still the more commonly used method (9,17). Reasons for not using the shade matching device are seen by Moodley et al. (2015) and Tung et al. (2002) in the fact that specialized devices like the spectro-photometer are expensive and not always convenient to use (19,20). Digital imaging and digital photography could offer an effective and less expensive alternative (21,22). The combination of pa-tients demanding more esthetic restorations and with dentists not willing to invest in expensive so-lutions, researchers have been forced to investigate in new technologies for cost efficient digital shade matching (15). The use of smartphones with their high-resolution photographic technology and their clinical applications for both healthcare professionals and patients represents an eligible alternative for the shade matching process (23–25). In other fields of dentistry, smartphones have been already integrated in dental procedures (26). In a previous study, a smartphone camera was already tested for color matching with a positive outcome (23). Nevertheless, no smartphone appli-cation available for dental shade matching has yet been assessed, to the author’s best knowledge. The aim of this study is to assess the shade matching abilities of two smartphone applications. The shade matching ability is examined using three shade tabs and three extracted teeth in an in vitro setting to compare the accuracy, repeatability, and reliability of two different smartphone applica-tions with visual and instrumental shade matching results. The hypotheses of this study are:

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11 H0 = The smartphone applications are as accurate and reliable as the visual shade matching abili-ties of dental students.

The objectives and tasks included to achieve this aim are:

1. To test the smartphone applications according to their accuracy and repeatability

2. To test the accuracy of dentistry students of the Lithuanian University of Health Science in the visual shade matching process for their accuracy and reliability

3. To test the spectrophotometer Vita Easyshade® for its accuracy and reliability in the shade matching process

4. To compare the three shade matching methods according to their accuracy and reliability and to define the best working method

5. To examine if visual shade matching accuracy and reliability is influenced by factors such as gender and level of experience.

6. To assess if the introduction of a threshold value influences the results gained by any of the measured methods

7. To examine if the smartphone applications show any divergences or limitations compared to visual and instrumental shade matching

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REVIEW

Dental tooth color determination differs from other science where quantities such as mass or vol-ume are intrinsic properties of an object and are identical for all observers. By contrast, the descrip-tion of the color of an object refers to a sensadescrip-tion experienced by a particular observer (27). The color perceived by an observer is hence mainly influenced by three sources: the observer, the influ-encing conditions in which shade matching is performed and the object itself (28,29). The influenc-ing factors of an observer are connected to the observer’s shade matchinfluenc-ing experience, age and gen-der, visual abilities and level of eye fatigue. No consensus is however found concerning whether females or males achieve better matching results (30–34). The same issue accounts for the experi-ence level of observers. Ortolan et al. (2013) and Alshiddi et al. (2015) were able to prove that ex-perienced and trained observers revealed better results than inexex-perienced ones (35,36), although Bahannan. (2014) were unable to show a statistically significant difference between experienced and inexperienced observers (7). Influencing conditions during the shade matching process include different lighting conditions (28). Depending on the light source, the quality and intensity of light reaching the teeth is altered and the color will be perceived differently by any observer. The phe-nomenon, called metamerism, means that a color is perceived by several observers to be the same in one light and different when another light source is applied (37,38). Several studies examining this phenomenon have confirmed the influence of different light sources of the perception of dental shades and recommend natural day light during the shade selection process (39,40). The object it-self adds difficulties in the color determination process as in their properties of reflectance, surface morphology, opacity, and translucency. The color perceived by an observer is a combination of dif-ferent wavelengths of light reflected by the surface of an object. Wavelengths visible for the human eye range from approximately 380 – 780 nm (41). Dental shade matching appears as a demanding task in the field of dentistry since a combination of optical properties are innate to a tooth color (13). A natural tooth has an inner opaque dentin layer covered with a translucent enamel layer (8). The tooth itself has a curved surface, which increases the scattering effect of the hydroxyapatite crystals within the enamel layer as the dentinal tubules in the dentin layer (29). The bluish appear-ance of the enamel layer derives from the trans-illumination of the reds and the scattering of the blue (42). Teeth vary dramatically in their opacity, translucency and surface morphology, and can be considered neither as homogenous nor as monochromatic which is what makes shade matching so difficult (13,43). Not only color determination is a difficult task in the shade matching process but also color communication. Colors are hence categorized in the Munsell color system according to hue, chroma, and value (LCh-values). Hue describes the actual color, for example red, green, and blue - chroma is the intensity of the hue and value is the brightness. Dental shades and tooth colors are described in such a manner. In 1976, the CIELAB color system was introduced by the

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sion Internationale de l’Eclairage (CIE). This color system enabled dentists as well as researchers to categorize dental shades using three definite values. Unlike the Munsell color system, the dental shade is not categorized according to their hue, chroma, and value, but according to their lightness (CIE-L), their distribution on the red-green (CIE a* with positive values representing red colors) and yellow-blue scale (CIE b* with positive values representing yellow) (44). The strength of this system is its ability to represent colors with a distance to each other (Eab) (37). The possible

meas-urement of colors and their differences is important for the reproduction of dental shades (28). Col-or matching utilizes this numeric system and shade guides used fCol-or the visual shade matching pro-cesses make use of them. Visual shade matching is completed by successively comparing the shade tabs with the natural teeth under the same environmental condition until the closest match is found (45,46) Visual shade matching is very subjective and unpredictable, a shortcoming that has re-searcher to develop specialized shade matching instruments. Shade matching devices range from colorimeter to spectrophotometer and imagining devices (14). Spectrophotometers are among the most accurate, highly precise, useful and flexible instruments for overall color matching in dentistry (15,16). Spectrophotometers, such as the Vita Easyshade® are usually easy to handle and make the selection process more objective and accurate. Those color measurements are not influenced by the surrounding light source or other distracting factors. Furthermore, color information is provided in LCh-values as well as in shade tab equivalent which simplifies color communication.

Hence, it is no surprise that the comparison of visual and instrumental shade matching has gained an increasing amount of interest during the last decade (10,15–18,47). A systematic review by Chen et al. (2012) investigated the question if instrumentally performed shade matching is superior to visual shade matching (46). For their review, 26 studies were compared. A total of 23 of the studies compared visual and instrumental shade matching and the remaining three studies selected infor-mation for the comparison of the spectrophotometer and colorimeter. The settings of the studies were either in vivo or in vitro, whereas one study combined both setting. The tested objects in the in

vitro studies were either extracted teeth or shade tabs. The sample sizes between those studies

var-ied significantly with the smallest sample size containing four teeth and the largest up to more than 3,000 teeth. The middle third was the mostly assessed surface for the shade matching measuments. According to their outcomes, the spectrophotometer offered more accurate and reliable re-sults. Interestingly, also using digital imaging in a shade matching process provided higher accura-cies compared to visual shade matching. Digital photography offers significant benefits to dental practices due to their efficiency and ease of use. Each of the three colors (red, green, and blue) is measured at each pixel location and used to create a color image (14,28). Digital cameras and other RGB devices represent a suitable approach to electronic shade taking (48). The ability to translate the RBG system into LCh or Lab values gives digital cameras the opportunity to be used in dental

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shade matching processes. Wee et al. (2006) investigated the ability of commercially available digi-tal cameras in combination with calibration models and their results indicated the possibility of in-tegrating their approach in the color reproduction in dentistry (49). Tam et al. (2012) proposed a method using a digital camera for the shade matching process that can, as stated by the authors, substitute spectrophotometers and colorimeters (50). In 2017, Tam et al. vetted the accuracy of shade matching exploiting the function of a digital camera of a smartphone. The captured images were compared using special software to a trained data set. The results of their study state that their approach using a smartphone in combination offers a suitable method for dental shade classification (23).

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VS

Vita Classical

1224 readings 312 readings 612 readings

MATERIALS AND METHODS

The clinical trial was approved by the Bioethics Center of the Lithuanian University of Health Sci-ence, Kaunas (Protocol No. BEC-OF-92) (Annex 1).

The main design and the methodology followed a previous study conducted by Brandt et al. (2017) (15). The experiment was conducted in vitro using shade tabs and extracted teeth. The study was composed of three major columns: visual shade matching (VS), shade matching using the spectro-photometer (INST), Vita Easyshade® (Vita Zahnfabrik, Bad Säckingen, Germany) and two smartphone applications, SMART, Dental Tooth Shade Recognition (Medical Effect LLC, Switzer-land) (DTSR) and Chromatcher (DMP Dental Industry S.A., USA) (CHROM).

1 Setting

For the visual as well as for the technology based dental shade matching, the same room was used in the prosthodontics department in the Lithuanian University of Health Science. The room was composed of a window facing north, which was covered by an opaque layer for the entire period of time. The ceiling light and an additional light which was set to daylight with 5500 Kelvin were in-stalled in the room. The additional light was arranged in such a manner that the light always came from above at an angle of about 45° facing the booth. The booth with the selected shade tabs (ST) and the extracted teeth (ET) was placed on a table in the middle of the room. The booth was set at a fixed distance for the visual part of the clinical trial so that there was a distance of about 25cm be-tween the booth and the participants. The shade tabs and the extracted teeth were installed in a

ro-Statistical analysis Measurement point INST Vita Classical SMART Vita Classical Measurement method Output values

Conversion of the VITA classical® values into L, C, h-values Conversion of L, C, h- values into L, a, b-values

Comparison of L-,a, b- values Accuracy in % and t-test

Reliability and repeatability in %

Experiment/trial

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tatable inner part of the booth. Therefore, only one shade tab or extracted tooth was visible once at a time. The installation of the shade tabs and the extracted teeth were arranged in such a way that on-ly the crown part of the shade tabs and extracted teeth was presented. The booth itself was painted in grey to ensure that students were not influenced by the surrounding color of the booth.

The shade tabs installed in the booth were three shade tabs from the Vita Classical® Shade guide (Vita Zahnfabrik, Bad Säckingen, Germany). The shade tabs were selected accordingly to the study conducted by Pop-Ciutrila et al. (2015) and Smith and Wilson (1998) who found that the most common dental shade among the Spanish population is B3 or A2 respectively (51,52). The color identification of the shade tab was covered with a tape and the shade tabs were installed by a third person so that the supervising examiner did not know which shade tab was installed at which posi-tion. This was done to establish a double blinded setting.

The extracted teeth were teeth collected in the Maxillofacial Surgery Department of the Lithuanian University of Health Science. Three extracted teeth were installed in the booth, two lower central incisors and one upper lateral incisor. After extraction, the teeth were examined for any defects and superficial staining as well as dental plaque and calculus was removed by scaling and polishing. For polishing, the Flairesse coarse polishing paste from the company DMG was used. The apices of the extracted teeth were shortened and the apical root canal was widened with a bur to be able to place a metal wire into the tooth for fixation. Until the installation of the extracted teeth to the booth and in between readings, the teeth were kept in an isotonic solution to prevent dehydration. The color of the extracted teeth was not measured or examined before the clinical trial, also with the aim to es-tablish a double blinded clinical trial.

For the shade matching process, the same second full set of the Vita Classical® shade guide was always used. The shade tabs in the shade tab holder were arranged as recommended by the manu-facturer and disarrangements were corrected before participants were asked to match the shades.

2 Visual comparison of dental shades

Students taking either practical or theoretical class in the prosthodontics department of the Lithua-nian University of Health Science were asked to participate voluntarily in the clinical trial. Students were invited individually to avoid the shades were being matched collectively and to ensure that each student was not influenced by the shade matching decision of other students. The students were given a short introduction, orally and in written form, about the aim and setup of the clinical trial and were then asked to sign a written consent (Annex 2). Appropriate information was then given for each task (Annex 3). However, no additional training and information was given concern-ing how to best accomplish shade matchconcern-ing.

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The clinical trial for testing the visual abilities of shade matching of the students was composed of three parts. The first part consisted of a small questionnaire asking the students general information such as their age, their gender, the semester they are currently enrolled in, the study program (Lith-uanian or international program) and their level of experience concerning shade matching. The ex-perience level was determined indirectly by asking if the students had already had patient contact in the prosthodontics department, if they had already had to do shade matching and if yes, where they had received their shade matching knowledge to accomplish the task (Annex 4).

The second task was for the students to do the Ishihara Color Blindness Test. Plates of the Ishihara Color Blindness Test were shown to the students and they were asked to write down what they saw. The students were instructed that they should note down the result as fast as possible, optimally within a few seconds. Students who recognized more than two plates incorrectly were considered as colorblind. Participants passing the Ishihara test, were deemed as having normal vision, either natu-rally or with corrective lenses (53). The result of the color blindness test was noted down on their questionnaire (Annex 5).

In the last and final part, students were asked to match the shades of three shade tabs and three ex-tracted teeth consecutively. The students were advised to match the shades in five to seven minutes but no time limit was set. The participants were allowed to take the shade tabs out of the holder, ro-tate the rotatable part of the shade tab and place it next to the presented tab or tooth. Students were advised to do the shade matching as they would do it for a real patient. The viewing angle was set to about 45° and the distance between the observer and the shade tab was 25cm (17). In the booth, shade tabs and extracted teeth were shown consecutively. The shade tabs were taken from a Vita Classical® shade guide. For the shade matching process, the students were given a second full set of shade stabs from the Vita Classical® shade guide. The shade tabs within the second shade guide were arranged as suggested by the manufacturer. After the student had matched the first shade tab and his or her answer was noted down, the inner part of the both was turned to the next shade tab by the supervisor and the student was asked to match the next shade tab. Students were not informed about their shade matching success during the entire clinical trial (Annex 6).

3 Dental shade matching using a spectrophotometer

All measurements were performed under the same standardized test conditions by one trained oper-ator. To exclude deviations due to production, the same device was used for all the measurement. The Vita Easyshade® was calibrated using the calibration plate on the docking station prior to measurements. The optical handpiece was held at a 90° angle to the installed shade tabs and the ex-tracted teeth consecutively. For the shade tabs, the trainings modus was selected as proposed by the manufacturer. For the extracted teeth, the single spot measurement for natural teeth was used. The

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probe tip was placed for all measurements onto the vestibular surface of the matching object con-tacting it on the middle third. Each shade tab and extracted tooth was measured 52 times. To achieve standardized conditions, it was tired to measure the same spot each time. The training mo-dus as well as the single spot measurement for natural teeth gives the shade color in the Vital Clas-sical® shade guide and Master 3D®. For this clinical trial, the Vita ClasClas-sical® values were noted down (Annex 7).

4 Dental shade recognition using smartphone applications

Two smartphone applications were tested regarding their accuracy and reliability of shade match-ing. One application was used for the Android-based systems, and one was used for the IOS-based system. For the Android-based system, the smartphone application Dental Shade Tooth Recognition was used. The application was developed by Medical Effect LLC. For the IOS-based system, the application Chromatcher was used, which was developed by DMP Dental. Both applications were able to be downloaded for free. The smartphone with the Android system was a Samsung Galaxy S8, the smartphone with the IOS system was an iPhone S6. For capturing the picture, the main back camera was used for both smartphones. The smartphones were installed on a tripod. The tripod was set at a distance of 10cm between the shade tabs or the extracted tooth and the camera. A light-correcting device (Smile Lite, Smile Line, St-Imier, Switzerland) was installed on the smartphone. The correcting light was tested before the clinical trial was conducted and the results gained with the correcting light were much better in comparison the results without the light correcting device. The Smile Lite device also offers also a live polarizing filter and a milky opaque diffuser. In the pre-liminary testing, the combination of using the filter as well as the diffuser revealed the best results. Both applications have a similar system concerning their functionality. After opening the applica-tion, the user has the opportunity either to upload a picture from the gallery or to take a new picture within the application. The latter was chosen for this clinical trial. After the picture has been taken using the application, the user can crop the picture to the desired size and focus on a certain area. The picture is then uploaded and ready for shade matching. The user can place their finger on the screen on the area they want to match for a dental shade. The recognized shade will then be pre-sented at the screen. For the DTSR, the user can select between different tooth guides. In this clini-cal trial the Vita Classiclini-cal® tooth guide was selected (Annex 8).

5 Data acquisition for calculating ΔE and threshold for ΔE

Each dental shade tab is composed of a dental shade color that can be represented on a graph by x-, y-, and z-values. The representation of the color can be categorized either according to the LCh or Lab system. The LCh systemsrepresent colors according to their lightness, chroma and value. The Lab system describes colors according to their lightness, their coordinates on the red-green and the

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blue yellow scale, respectively. Thus, each color has one precise point on that graph. These LCh reference values for the shade tabs were defined by measurements done using a spectrophotometer. The Vita Easyshade® is able to present the measured coordinates in single spot measurement mo-dus. According to these coordinates, the spectrophotometer recommends a tooth shade within the Vita Classical® and Vita 3D Master® system. In addition to the recommended shade, the quality of the match is presented. The quality of the match is calculated according to the difference of the measured coordinates in comparison of the perfect coordinates. The measured coordinates and the difference to the perfect color coordinates of the recommended shade were then either subtracted or added to the measured coordinates. The LCh values were then converted into the Lab system an online converting program (http://colormine.org/convert/lch-to-lab). Those values were then further used to be able to calculate the color difference (Eab) between the dental shades matched by the

visual, instrumental or application based method and the reference values of the true dental shade. For the calculation of the color difference (Eab) between the different shade tabs, the following

formula was used 𝐸𝑎𝑏 = √[(𝐿𝑖− 𝐿𝑗) 2

+ (𝑎𝑖− 𝑎𝑗) 2

+ (𝑏𝑖− 𝑏𝑗) 2

]. Several studies have reported dif-ferent clinically acceptable threshold for shade matching (54). The threshold selected for this study is Eab = 3.3 (47).

6 Statistical methodology

The data were processed using Microsoft Excel 2010 while statistical analyses were carried out us-ing the IBM statistical software SPSS statistics 23 (55). Statistical significance was accepted at P < 0.05 (55). The accuracy and reliability was assessed for a perfectly correct matched dental shade and for a match within a threshold value. Reliability was also divided into inter-rater and intra-rater reliability.

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RESULTS

1 Data collection

For the visual shade matching part, 204 dental students enrolled at the Lithuanian University of Health Science were asked to participate in this clinical trial from February 20th to 26th, 2018. Re-quirement for the students to participate in this clinical trial were practical dental courses. Begin-ning in the 4th semester of the odontology study program, students learn practical dental skills in phantom classes. Therefore, student studying in the 4th or higher semester were eligible.

For testing the matching abilities, 52 measurements per test object were taken with the spectropho-tometer, Vita Easyshade®. In total, 312 measurements were taken with the spectrophotometer. Measurements were taken on February 27th and 28th, 2018. The smartphone applications were tested on March 1st and 2nd, 2018. One day was dedicated to testing the Android-based smartphone cation, DTSR, and the other day was used to obtain readings with the IOS-based smartphone appli-cation, CHROM. All readings from both applications combined make up 612 readings.

Table 1: Trial series. Trial

series

Method N Trial object Number

of objects Readings Total amount of readings 1 VS 204 ST 3 1 612 2 VS 204 ET 3 1 612 3 INST 1 ST 3 52 156 4 INST 1 ET 3 52 156 5 DTSR 1 ST 3 51 153 6 DTSR 1 ET 3 51 153 7 CHROM 1 ST 3 51 153 8 CHROM 1 ET 3 51 153

Total amount of readings 2148

2 Preliminary data management

No missing data were found, meaning that each student accomplished all three parts and filled in all needed values in each single task. Outliers were seen for INST and DTSR, as the third shade tab was measured with 100% of the readings with the same correct color. Those values were viewed separately since many statistical tests cannot be computed if the standard error of the difference is 0.

3 Descriptive statistics

3.1 Socioeconomic parameters

Out of 204 dental students participating, 136 participants were female, making up 66.7%, and 68 participants were male, representing 33.3%. The majority of students, 36.7% or 75 in number, were studying in the 10th semester which is the last semester before students receive their medical doctor

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degree. 53 students, representing 25.9% of the participants each, were either enrolled in the 4th or the in the 8th semester. Students studying in their 6th semester made up the smallest group (23 partic-ipants or 11.3%). The average age of the students was 23.39 years old ranging from 19 to 47 years old. 142 participants were studying in the Lithuanian program offered by the university, and 60 par-ticipants were studying in the international program. The country of origin of the international stu-dents varied between different countries including Israel, Sweden, Germany, etc. but the number of students representing each country was too small to be considered individually in this analysis. 139 students (58.3%) stated that they had already had patient contact and were treating patient at the prosthodontics department of the university. 123 of those students (60.3%) were also confronted with a shade matching task during their practical classes and while working with patients. 90 partic-ipants (44.1%) gained their shade matching knowledge during classes at the university, 10.3% of the participants from classes at the university but also from outside, for example volunteering at dental clinics. The conducted Ishihara Color Blindness test revealed that 9 of the participants were colorblind, representing 4.4%. Those participants were marked separately and their results were lat-er tested if the color blindness negatively influences the shade selection process.

Table 2: Socioeconomic parameters VS.

Parameter N Percentage Gender Males 68 33.3% Females 136 66.7% Age Average 23.39 Range 19-47 Study program Lithuanian program 142 69.6% English program 62 30.4% Semester 4th semester 53 26.0% 6th semester 23 11.3% 8th semester 53 26.0% 10th semester 75 36.8% Color blindess Detected 9 4.4% Experience level Patient contact 139 68.1%

Shade matching experience 123 60.3%

Color matching knowledge

Classes at LSMU 90 44.1%

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3.2 Distribution of dental shades matched

The distribution of the dental shades selected by the different methods is seen in table 3 and 4. For VS, the results show that about half of the participants selected the correct dental shade for each of the three shade tabs (52.2% for ST 1, 49% for ST 2, and 47.5% for ST 3). For ST 1, the distribution reveals that the second most commonly selected dental ST is B4 and A4 with 20.6% and 20.1% re-spectively. Other dental shades have been selected but only amount to a negligible percentage. For ST 2 and 3, the distribution of dental shades is wider (nine and eleven different shades selected for ST 1 and 2 respectively) as for ST 1 (eight different shades) and the tendency towards certain dental shades is not as pronounced as for ST 1.

For the ET 1 and 2, the tendency towards A1 and B1 with 51% and 35.3% as well as with 41.2% and 35.3% respectively is seen. The distribution for the ET 3 does not show any tendency towards any dental shade.

INST showed a clear tendency with more than 60% of all color measurements for all three shade tabs towards the correct dental shade. The results also show that if the dental shade was not correct-ly selected oncorrect-ly six other dental shades had been chosen maximalcorrect-ly. For the extracted teeth, the dis-tribution of the measured dental shades becomes wider. A definite tendency to dental shade B2 is only seen for the ET 1 with 67.3%.

DTSR has a clear tendency within all measurements for dental shade A2, expect for ST 1 where dental shade A1 was the most often measured dental shade. Besides those two dental shades, all other dental shades being measured only amount to a negligible percentage.

The results gained by CHROM also show a tendency to selecting A3.5 and B2 for most of the color measurements. However, for ST 1 and 2 alternative dental shades included only A3 or A3 and A2 respectively.

Table 3: Distribution of selected shades in percentage from ST A1 to B4.

A1 A2 A3 A3.5 A4 B1 B2 B3 B4 VS ST 1 52.5 20.1 0.5 0.5 20.6 ST 2 10.3 12.3 1.0 2.0 49.0 4.9 ST 3 0.5 47.5 10.3 0.5 8.8 0.5 ET 1 51.0 2.5 0.5 35.3 1.5 ET 2 41.2 2.5 0.5 0.5 35.3 2.5 ET 3 11.3 18.1 6.4 3.4 1.0 13.2 2.5 0.5 INST ST 1 11.5 61.5 15.4 ST 2 21.2 3.8 67.3 ST 3 100 ET 1 3.8 9.6 19.2 67.3 ET 2 46.2 13.5 40.4 ET 3 9.6 17. 36.5 3.8 30.8

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23 DTSR ST 1 19.6 76.5 3.9 ST 2 94.1 2.0 2.0 ST 3 100 ET 1 96.1 2.0 ET 2 96.1 2.0 2.0 ET 3 27.5 39.2 2.0 2.0 7.8 CHROM ST 1 49.0 51.0 ST 2 17.6 41.2 39.2 2.0 ST 3 37.3 62.7 ET 1 45.1 2.0 52.9 ET 2 68.6 2.0 25.5 ET 3 3.9 2.0 70.6 23.5

Table 4: Distribution of selected shades in percentage from ST C1 to D4.

C1 C2 C3 C4 D2 D3 D4 VS ST 1 1.5 3.9 0.5 ST 2 3.9 6.4 10.3 ST 3 1.0 4.4 0.5 6.4 19.6 ET 1 2.9 5.9 0.5 ET 2 7.8 8.8 1.0 ET 3 5.4 1.0 2.9 2.0 21.6 10.8 INST ST 1 7.7 1.9 1.9 ST 2 7.7 ST 3 ET 1 ET 2 ET 3 1.9 DTSR ST 1 ST 2 2.0 ST 3 ET 1 2.0 ET 2 ET 3 2.0 3.9 3.9 2.0 5.9 CHROM ST 1 ST 2 ST 3 ET 1 ET 2 2.0 2.0 ET 3

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3.3 Average distribution of matched shade according to Eab

The Eab of the Vita Classical® shade tabs range from 1.225 to 31.251, representing the dental

shades A1 to D4 (Annex 5). The E_ab of the presented shade tabs was Eab=5.09 between A3.5 and

B3, Eab=5.88 between B3 and A2, and Eab=10.60 between A3.5 and A2.

The results of the average distribution of matched shades according to Eab are seen in table 5. The

results revealed by DTSR have the highest maximum with 19.77 which means that the difference between the actual dental shade and the measured dental shade is the biggest. The mean is also the highest for DTSR with 12.16 and 12.00 for ST 1 and 2 respectively. CHROM showed the lowest maximum for ST 1 and 2. The readings revealed by CHROM had the smallest difference between the actual and the selected dental shade. INST showed the smallest mean for all three shade tabs. Since ST 3 was selected correctly by INST and DTSR with 100%, no minimum, maximum, mean and standard deviation could be calculated.

Table 5: Delta E calculations.

N Minimum Maximum Mean SD

VS ST 1 204 .00 16.75 2.8548 3.96315 ST 2 204 .00 11.08 2.9288 3.60876 ST 3 204 .00 9.99 2.0793 2.25521 INST ST 1 52 .00 12.23 2.8488 3.94070 ST 2 52 .00 11.08 1.6030 3.18143 ST 3 52 .00 .00 .0000 .00000 SMART DTSR ST 1 51 10.60 19.77 12.1554 2.87856 ST 2 51 5.88 15.67 11.9991 1.21136 ST 3 51 .00 .00 .0000 .00000 CHROM ST 1 51 .00 7.26 3.5590 3.66562 ST 2 51 2.24 7.19 4.0995 1.61576 ST 3 51 1.61 10.60 4.9609 4.39236 4 Statistical analysis 4.1 Accuracy measurements

The accuracy of each of the shade matching methods was assessed in three ways: the first calcula-tions examined how often which method selected the correct dental shade, the second calculation investigated if the correct dental shade was not chosen, how close the selected dental shade was in comparison to the perfect dental shade; and the third calculation examined if there was a difference of the averages between the different shade matching methods (t-test).

4.1.1 Accuracy according to a perfect match

Results of the accuracy of perfectly matched shades can be seen in table 6. The results revealed that shade matching using INST had the highest accuracy among all three shade tabs, followed by VS.

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The accuracy of VS however declines continuously with each shade tab. The revealed accuracy us-ing SMART is quite low. Both applications did not recognize the correct dental shade for two shade tabs. Comparing DTSR and CHROM, it can be seen that DTSR performs better in recognizing the dental shade for ST 3. The dental shade of ST 3 was recognized correctly with 100% by DTSR, whereas CHROM only recognized the correct dental shade for STs 1 with 51%.

Table 6: Accuracy of perfectly matched shades.

SMART

VS INST DTSR CHROM

ST 1 52.5% 61.5% 0% 51%

ST 2 49% 67.3% 0% 0%

ST 3 47.5% 100% 100% 0%

4.1.2 Accuracy according to the threshold

Results of the accuracy according to the threshold value can be seen in table 7. For the calculation including Eab, a threshold of 3.3 was chosen. This means that color selections with Eab smaller or

equal to 3.3 were clinically still acceptable and considered as a good match. The calculations re-vealed the same ranking within the different shade matching methods as in the measurements for accuracy of a perfect match. However, VS achieved the best accuracy within the threshold value for ST 1. The results of DTSR were not influenced by the introduction of the threshold value. CHROM, by contrast, gained much better results accepting readings within the threshold value. Their results in accuracy increased by 41.2% and 62.7% for ST 2 and 3 respectively.

Table 7: Accuracy according to a threshold.

SMART

ST 1 73% 61.5% 0% 51%

ST 2 64.2% 88.5% 0% 41.2%

ST 3 70.1% 100% 100% 62.7%

The results are also depicted graphically using box plots in figure 2, 3, 4, and 5. Box plots represent the distribution of a range of the different shade matching methods. The box plots divide the results of each group into four sections. Those sections are called quartiles. The box itself represents the middle 50% of the dental shade selections for each method. The upper and lower 25% quartiles are pre-sented with a line in the graph which is called whiskers. A line shown within the box represents the me-dian of the scores.

The box plots for VS showed that middle 50% of the results for ST 1 matching is represented by the smallest box, followed by ST 3, and then by ST 2. ST 1 shows also a lower upper quartile with mainly five outliners. The upper quartile of the shade selection for ST 2 is wider than those of ST 1 and 3, but no outliers are seen. For ST 3, the upper quartile lies in between that of ST 1 and 2. One student was an

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26 outliner in the shade matching process for ST 1 and 3. In the shade selection of ST 1 are the most outli-ers seen. The median for ST 1 and 3 lies at 0, for ST two it is 2.24.

The box plots for INST showed slightly different results. The results of ST 3 are only represented by a line. This is the case because INST recognized only one dental shade for ST 3. No range can be presented or calculated. The box plot for the ST 2 shows no upper and no lower quartiles. The mid-dle 50% of the matches is quite narrow and only measurements represent outliers. The box plot for ST 1 has a wider box and an upper quartile. No outliers are seen. For ST 1 and 2, the median lies on the 0 value line.

The boxplots for DTSR shows no boxes for neither of the measurements. ST 3 was recognized with 100% with the correct dental shade. No quartiles, average and median can be calculated. Only lines representing the median can be seen. The median for shade selection 1 and 2 lies at 10.60 and 12.15 respectively. For ST 1, five outliers are seen in the upper quartile. One outlier lies in the upper quar-tile and two in the lower quarquar-tile.

Fig. 2: Boxplots VS shade tab 1, 2, and 3.

Fig. 3: Boxplots INST shade tab 1, 2, and 3.

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27 The box plots for CHROM showed the middle 50% of the results for ST 2 matching representing the smallest box, followed by ST 3, and then by ST 1. ST 1 and 3 show no upper and lower quartiles. ST 2 shows only an upper quartile. The median of the dental shade selection lies at 0, 5.09, and 1.60 for ST 1, 2 and 3 respectively. None of the box plots show outliers. The box of ST 1 is the widest.

VS against INST and SMART

Results of the t-tests can be seen in table 8. Comparing the mean values of the ST 2 between INST (M=1.60, SD=3.18) and VS (M=2.93, SD=3.61) a statistically significant difference was found (T(254)=2.42; p<.05). A statistically significant difference (T(254)= 6.64; p<.001) was also found comparing the mean of VS (M=2.08, SD=2.26) with the mean of INST (M=0, SD=0) for the ST 3. For ST 2 and 3, it was ascertained that INST showed smaller deviation of the measurements com-pared to VS. For ST 1, no statistically significant difference was assessed. Between the mean of VS (M=2.85, SD=3.96) for ST 1 and the mean of DTST (M=12.16, SD=2.88), there was a statistically significant difference seen (T(253)=15.74; p<.001). Comparing the mean values of ST 2 between VS (M=2.93, SD=3.61) and the DTSR (M=12.00, SD=1.21) a statistically significant difference was found (T(253)=17.6792; p<.001). A statistical significant difference (T(253)=6.5746; p<.001) was also found comparing the mean of VS (M=2.08, SD=2.26) with the mean of DTSR (M=0, SD=0) for the ST 3. For all three shade tabs it was noted that VS revealed means with smaller vari-ances compared to DTSR. Between the mean of VS (M=2.93, SD=3.61) for ST 2 and the mean of CHROM (M=4.10, SD=1.62), there was a statistically significant difference seen (T(253)=2.26; p<.05). Comparing the mean values of the ST 3 between VS (M=2.08, SD=2.26) and CHROM (M=4.96, SD=4.39) a statistically significant difference was found (T(253)=6.55; p<.001). Also in the comparison between the VS and CHROM for ST 2 and 3, VS showed smaller deviations of the mean compared to CHROM deviations. No statistical difference was found for ST 1 comparing VS and CHROM.

Table 8: T-test of VS compared with INST and SMART.

Group 1 Group 2 T df P

VS – ST 1 INST – ST 1 0.0098 254 0.9922

VS – ST 2 INST – ST 2 2.4197 254 0.0162

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28 VS – ST 3 INST – ST 3 6.6389 254 0.0001 VS – ST 1 DTSR – ST 1 15.7429 253 0.0001 VS – ST 2 DTSR – ST 2 17.6792 253 0.0001 VS – ST 3 DTSR – ST 3 6.5746 253 0.0001 VS – ST 1 CHROM – ST 1 1.1675 253 0.2441 VS – ST 2 CHROM – ST 2 2.2582 253 0.0248 VS – ST 3 CHROM – ST 3 6.5513 253 0.0001

INST against SMART

Results of the t-tests comparing INST with SMART can be seen in table 9. Comparing the mean values of the ST 1 between INST (M=2.85, SD=3.94) and DTSR (M=12.16, SD=2.88) a statistical-ly significant difference was found (T(50)=-12.830; p<.001). A statistical significant difference (T(50)=-20.489; p<.001) was also found comparing the mean of INST (M=1.60, SD=3.18) with the mean of DTSR (M=12.00, SD=1.21) for ST 2. Comparing the mean values of the ST 2 between INST (M=1.60, SD=3.18) and CHROM (M=4.10, SD=1.62) a statistically significant difference was found (T(50)=-4.991; p<.001). Between the mean of INST (M=0, SD=0) for ST 3 and the mean of CHROM (M=4.96, SD=4.39), there was a statistical significant difference seen (T(50)=-8.066; p<.001). For ST 1 and 2 it was ascertained that INST showed smaller deviation of the measure-ments compared to DTSR. INST showed also smaller deviations of the mean for ST 3 in compari-son to CHROM. No statistical significant difference was found between the mean of INST and the mean of CHROM for ST 3.

Table 9: T-test of INST compared with SMART.

Group 1 Group 2 T df P INST – ST 1 DTSR – ST 1 -12.830 50 .000 INST – ST 2 DTSR – ST 2 -20.489 50 .000 INST – ST 1 CHROM – ST 1 -.790 50 .433 INST – ST 2 CHROM – ST 2 -4.991 50 .000 INST – ST 3 CHROM – ST 3 -8.066 50 .000 DTSR against CHROM

Results of the t-tests of DTSR and CHROM can be seen in table 10. Between the mean of DTSR (M=12.16, SD=2.88) for ST 1 and the mean of CHROM (M=3.56, SD=3.67), there was a statisti-cally significant difference seen (T(50)=13.82; p<.001). Comparing the mean values of ST 2 be-tween DTSR (M=12.00, SD=1.21) and CHROM (M=4.10, SD=1.62) a statistically significant dif-ference was found (T(50)=27.98; p<.001.) A statistically significant difdif-ference (T(50)=-8.07; p<.001) as also found comparing the mean of DTSR (M=0, SD=0) with the mean of CHROM (M=4.96, SD=4.39) for ST 3.

The results show CHROM means with a smaller variance for ST 2 and 3 in comparison to the DTSR. Only for ST 3 did the mean of DTSR show a smaller deviation than CHROM.

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29 Table 10: T-test of DTSR compared with CHROM.

Group 1 Group 2 T df P

DTSR – ST 1 CHROM – ST 1 13.820 50 .000

DTSR – ST 2 CHROM – ST 2 27.98 50 .000

DTSR – ST 3 CHROM – ST 3 -8.066 50 .000

4.2 Reliability and repeatability measurements

4.2.1 Intra-rater reliability and repeatability for a perfect match

Results of the intra-rater reliability and repeatability for a perfect match can be seen in table 11. The intra-rater reliability presents the mean value matching the correct dental shade performed by the same shade matching method and the same observer. These results clearly state that ISNT revealed the best readings recognizing all three shade tabs correctly. Also, it is seen that INST always matched at least one dental shade correctly. This applies also for DTSR though DTSR also never matched more than one dental shade correctly. VS achieved best results recognizing one dental shade as well as CHROM. However, almost one third of the readings by VS matched two shade tabs correctly.

Table 11: Intra-rater reliability and repeatability of perfectly matched shades.

SMART

0 shade tabs correct 17.2% 0% 0% 49%

1 shade tab correct 33.3% 19.2% 100% 51%

2 shade tabs correct 32.8% 32.7% 0% 0%

3 shade tabs correct 16.7% 48.1% 0% 0%

4.2.2 Intra-rater reliability and repeatability according to a threshold

The results can be seen in table 12. The calculations, taken the threshold value under consideration, elucidate the previous results: INST has the highest repeatability matching all three shade tabs, fol-lowed by VS which received the highest intra-rater reliability for matching dental shades for two shade tabs within threshold value. DTSR, as seen before, was only able to match one dental shade perfectly correct. All other measurements performed by DTSR were outside the threshold values. The biggest change was seen for CHROM. Whereas for perfectly matched dental shades CHROM was only able to achieve readings for one shade tab, the inclusion of the threshold value showed clearly that selected dental shades were within the threshold value for all three shade tabs. Compar-ing SMART, CHROM revealed certainly more reliable results than DTSR.

Table 12: Intra-rater reliability and repeatability according to the threshold.

SMART

0 shade tabs correct 8.3% 0% 0% 13.7%

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2 shade tabs correct 36.3% 38.5% 0% 41.2%

3 shade tabs correct 32.8% 55.8% 0% 13.7%

4.2.3 Inter-rater reliability and repeatability for a perfect match

The results can be seen in table 13. The inter-rater reliability describes the mean value of the per-centage of agreement between the different shade matching methods. The results of our measure-ments showed that INST provides the most reliable shade matching method with 76.2%, followed by VS with 49.79%. DTSR and CHROM revealed only very low reliability with 33.3% and 17% respectively.

Table 13: Inter-rater reliability and repeatability of perfectly matched shades.

SMART VS INST DTSR CHROM ST 1 52.5% 61.5% 0% 51% ST 2 49% 67.3% 0% 0% ST 3 47.5% 100% 100% 0% Reliability 49.7% 76.2% 33.3% 17%

4.2.4 Inter-rater reliability and repeatability according to a threshold

The results can be seen in table 14. Inter-rater reliability and repeatability for VS, INST, and CHROM increased compared to the reliability and repeatability measurements for perfectly matched shades. The results obtained by DTSR were not influenced by the consideration of the threshold value. All other color measurements, besides those for dental shade A2, were not accepta-ble. The ranking within the methods stayed the same as it was calculated for perfectly matched shades. However, the gap between VS and CHROM decreased from 32.07% to 12.9%. This de-crease is caused by an inde-crease threefold of the repeatability of CHROM.

Table 14: Inter-rater reliability and repeatability according to a threshold.

SMART VS INST DTSR CHROM ST 1 73% 61.5% 0% 51% ST 2 64.2% 88.5% 0% 41.2% ST 3 56.4% 100% 100% 62.7% Reliability 64.5% 83.3% 33.3% 51.6% 4.3 Control variables

A paired t-test was done to calculate if there is a difference for the visual color matching abilities between students having normal color vision or being colorblind, between genders, between differ-ent semesters, between the Lithuanian study program or the international, between studdiffer-ents having shade matching experience and students without any experience. For all the mentioned values, no statistically significant differences were found.

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DISCUSSION

Previous studies have investigated the influencing factors of visual shade matching (7,30–33,35,36). Alternative methods using a colorimeter or spectrophotometer have been tested for their accuracy and inter-device agreement and inter-rater reliability (2,8,11,56,57). Different settings have been used and no consensus has been found concerning any superiority of any of these methods (8,56). Investigations into new methods using digital photography have been employed and have been suc-cessfully integrated into shade matching in the field of dentistry (49,50,58). Smartphone cameras and special software for the analysis of those pictures have been examined in the shade matching process (23). However, no integration of the latter seems to be apparent in daily practice. This study examined the suitability of two smartphone applications for their integration in the dental shade matching process. For the suitability, accuracy and reliability testing and comparison were done with the visual and instrumental shade matching method. A smartphone in combination with already available shade matching applications were tested because, with regard to cost efficiency, familiari-ty, and ease of use, smartphones appeared to be beneficial in the shade matching process. Especially the continuous development and optimization and the high quality of the built-in cameras of smartphones make them eligible for further testing their applicability in the shade matching process.

1 Setting

A simple methodology approach was chosen, one used by another study (15). The different shade matching methods were tested in an in vitro setting using shade tabs and extracted teeth. Using shade tabs for testing the accuracy and reliability of shade matching abilities has also been used by Pohlen et al. (2016), Lehmann et al. (2017), Tsiliagkou et al. (2016), Ortolan et al. (2013), and Parameswaran et al. (2016) (17,35,59–61). Extracted teeth were also the test object in studies con-ducted by Pecho et al. (2015) (62). Nevertheless, several studies concon-ducted their studies in vivo (15,36,47). The advantage of an in vitro setting was that the authors of this study did not rely on any patient. The authors were able to conduct the clinical trial throughout the day at different day times. Additionally, standardized conditions could be easily achieved and no influencing factors such as make up or clothing had to be considered. The disadvantage of the in vitro setting was that the test-ing conditions were rather unnatural and unrealistic. The shade tabs and the extracted teeth were presented in a booth rather than in an environment imitating the oral cavity. The booth was colored with a neutral matt grey color as it is suggested for dental shade matching and as also conducted by Pecho et al. (2015) (25,62,63). However, no clinical simulation with gingiva or adjacent teeth were shown as in other studies (16,60).

The room that was chosen for the clinical trial was a room available in the Prosthodontics Depart-ment of the Lithuanian University of Health Science. Nevertheless, the room was not built for

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tal treatment but for holding lectures. The room was only composed of a standardized ceiling light. The ceiling light is the same as installed in the practical working cabinets but no additional light was provided such as of a dental light, etc. The additional light used in this study was primarily in-stalled for this research and was set according to the authors recommendations. Recommendations for the light installation included the angle of the lamp to the tested object, the intensity of the light, and the temperature of the light. The selected temperature of the light was 5500 Kelvin. This light temperature was also used by Kröger et al. (2015), Pimentel and Tiossi (2014), Pohlen et al. (2016), and Sinmazisik et al. (2014) (10,18,53,59). As an alternative light temperature, other studies also used 6500 Kelvin (17,47,55). Martinez et al. (2014) showed better results using a light source of 6500 Kelvin compared to ambient light (64). No variation between different light sources was in-vestigated during this study, despite several studies stating the impact of such variations (39).

As done in other studies the source of natural light which is recommended for doing visual shade matching was excluded (16). Daylight was excluded to obtain a standardized condition since the clinical trial was conducted during winter time with unstable weather conditions and throughout different times during a day.

2 Test subject selection

The test subjects were selected according to the field of interest. Our interest was to investigate the matching abilities of two smartphone applications in comparison to visual shade matching of dental students and a spectrophotometer. Dental students were admitted if they were studying in the se-cond year of the education program. These students present rather an inexperienced cohort (34). As stated of previous studies, the level of experience has an influence of the visual shade matching ability (35,36). However, no clear consensus is given on this topic as other studies affirm our results that the experience level has no effect (33,65). No additional training was provided to the test sub-jects. Previous studies have claimed that the accuracy and reliability of visual shade matching in-crease with additional training (66,67). The trial was conducted throughout the day. Students were asked to participate voluntarily during their practice time in the Prosthodontics Department at the Lithuanian University of Health Science. The times, students participated in this study ranged from 8:00 in the morning to 20:00 in the evening. It was not assessed if time of the day of participation had any influence on the student’s matching ability nor if the students were tired or stressed. How-ever, tiredness and eye fatigue have been stated to influence the visual shade matching abilities (68,69). No students from other Universities or other study programs were included in the study whereas different results of shade recognition have been shown between different dental related oc-cupations (13,35,67).

DENTAL SHADE MATCHING. THE COMPARISON OF VISUAL SHADE MATCHING ABILITIES WITH VITA EASYSHADE® AND DENTAL SHADE RECOGNITION SMARTPHONE APPLICATIONS

Angela Sarah Haack

DENTAL SHADE MATCHING.

THE COMPARISON OF VISUAL SHADE MATCHING

ABILITIES WITH VITA EASYSHADE® AND DENTAL

SHADE RECOGNITION SMARTPHONE APPLICATIONS

TABLE OF CONTENTS

SUMMARY

LIST OF ABBREVIATIONS

INTRODUCTION

REVIEW

MATERIALS AND METHODS

RESULTS

DISCUSSION