Influence of Skin Tone and Background Color on the Accuracy of Auricular Scanning: A Clinical Trial
Phase: NA
Conditions: Healthy Participants
Sponsor: yasmine Elsherbeeny

 
 
Influence of Skin Tone and Background Color on the Accuracy of Auricular 
Scanning: A Clinical Trial 
 
 
 
 
Authers: 
Dr/ Yasmine Said Elsherbeeny, (DDS, MSc, PhD), Department of oral and maxillofacial Prosthodontics, 
Faculty Of Dentistry, Ain Shams University, Cairo, Egypt. 
Dr/Amany Mostafa Saad Farahat, (DDS, MSc, PhD), Department of oral and maxillofacial Prosthodontics, 
Faculty Of Dentistry, Ain Shams University, Cairo, Egypt. 
Dr/Mohamed Talaat Elmohammady Mohammed, (DDS, MSc) 
Dr/ Omnia Mohamed Sameh Omar El Sayed Refai, (DDS, MSc, PhD), Department of oral and maxillofacial 
Prosthodontics, Faculty Of Dentistry, Ain Shams University, Cairo, Egypt. 
 
 
Corresponding author: 
 Yasmine Said Elsherbeeny, yasmineelsherbeeny@dent.asu.edu.eg, Department of oral and maxillofacial 
Prosthodontics, Faculty Of Dentistry, Ain Shams University, Cairo, Egypt. 
 
 
Document Date:  
4th July 2025 
 

 
 
Table of Contents 
 
 
 
 
Topic 
Page 
I. 
Abstract 
3 
II. 
Background 
4 
III. 
Research Question 
6 
IV. 
Aims (Objectives) 
7 
V. 
Hypothesis 
7 
VI. 
Ethical Considerations 
7 
VII. 
Study design 
8 
VIII. Materials and Methods 
• Study setting 
• Sample Size 
• Study Procedures 
8 
IX. Data management 
11 
X. Statistical Analysis 
12 
XI. Funding of the Study 
12 
XII. References 
13 

 
 
I- 
Abstract 
Statement of the problem 
Manufacturing the Extraoral prosthesis is troublesome for the patient, the dental 
practitioner and the dental technician. When a person misses his ear congenitally or due to trauma, 
he wishes to have an accurate replacement for his ear with minimum steps and effort. Digital 
technology has been providing the dental field with the most helpful equipment in such cases. 
Owing to the innovation of intraoral scanners with its continuous refinement, this patient now can 
rest assured that he will have his auricular prosthesis with less number of visits and less effort. 
There are different environmental factors that can affect scanning accuracy such as patients skin 
tone and scanning background. 
Aim of the study 
This study aims to evaluate the different backgrounds and skin tones effect on the trueness 
of auricular scanning. 
Materials and methods 
 
Participants with intact ears and different skin tones (black, white and intermediate) will 
be selected from the outpatient clinic, then conventional impression will be taken and stone cast 
will be obtained and scanned via an extraoral scanner, then intraoral scanner will be used to scan 
the auricle three times, first with a black background, second with white background, third without 
background. Trueness of the scans will be evaluated by metrological software. Data will be 
collected, tabulated, and statistically analyzed. 
 
 

 
 
II- 
Introduction 
Auricular deformity can be a congenital condition or happens due to trauma or surgical 
removal. (1.2) Restoring such a defect is a challenging process as the prosthodontist and the dental 
technician should work together to reproduce and replace the missing ear with a much more lifelike 
prosthesis with its minute details, which needs a great level of skill that usually comes with time 
and experience. Conventional fabrication techniques of auricular prothesis involves many time 
consuming and difficult steps like; taking an impression of both the intact and the defect side to 
facilitate sculpting the wax pattern  of the ear guided by the cast of the contralateral side, creation 
of a mold to cast the prosthesis and manufacturing the prosthesis from biocompatible materials 
like silicones which can be pigmented to match the patient`s skin tone. (3,4) This technique is 
somehow troublesome as it involves making a stable backing from acrylic or more recently a 
plastic ring around the ear which allows pouring the impression which is usually more flowy than 
the usual impression. (5) The patient has to sit with his auricle parallel to the floor without any 
movement to enable the practitioner to take the impression with the least possible distortion which 
can be 1-3 mm approximately.  (6) 
This has led to the development of different innovative methods for creating the extraoral 
prosthesis and managing to make this prosthesis unnoticeable to the sight. Implementing the digital 
technology into the dental field has provided the dental team with more feasible methods to 
fabricate an accurate replica of the deformed ear through data digitization, computer-aided design 
(CAD), and computer-aided manufacturing (CAM). Data acquisition is the first step in the digital 
workflow and of great importance. (7) It can be done via different methods such as computed 
tomography (CT) scan, three-dimensional (3D) photogrammetry, magnetic resonance imaging 
(MRI), laser scanners and intraoral scanners. (8,9) 
One of the drawback of computed tomography (CT) scan is the hazardous x-ray exposures, 
furthermore, magnetic resonance imaging (MRI) provides less resolution , laser scanners expose 
the patient to laser which can be harmful to the eyes and it takes several minutes which is quite 
disturbing for the patient who is required to stay still meanwhile, they cannot record all the surface 
details asapores , undercuts or wrinkles, which is also true for extraoral scanners. (10,11) 
Intraoral scanners offer a better outcome for the entire experience as they eliminate the use 
of impression materials and reduce the time taken to take one. They also allow easy data transfer 

 
 
between the dental office and the dental lab which can be saved for future reference. (12-14) There 
are different types of intraoral scanners that can be handheld, which give the practitioner the 
opportunity to scan from different angles allowing him to capture the minute undercuts. (15,16) The 
differences between each type of intraoral scanner depends on its technology, which can be based 
on active wavefront sampling, confocal technology, triangulation theory or a combination of two 
or more of them to improve accuracy. (12,17) In Active wavefront sampling technology, optical rays 
are projected which create three-dimensional simulations. (18) While in IOSs using the triangulation 
theory, a light is projected onto the surface in a pattern which is then captured by a camera or 
sensor positioned at an angle. In confocal technology a laser beam is reflected via a pinhole 
aperture which is captured with sensors without requiring specific angles between light sources 
and sensors like triangulation technology. (18,19) 
The field of intraoral scanning is in continuous shift for developing better outcomes such 
as decreasing scanning time, eliminating the usage of scanning powder and enhancing the image 
color which eventually results in better user experience, patient comfort and better data acquisition. 
(20) This also leads to different outcomes regarding the accuracy of the acquired data. Accuracy is 
recognized by two elements: trueness and precision. Trueness means how close a scanned subject 
is to its original design and precision is the ability of a scan to be consistently repeated. (21) 
Accuracy of scanning is also affected by multiple environmental factors such as the lighting 
condition, (22,23) the background and the skin tone of the patient. (24) Considering the nature of how 
light works, it transfers its energy to the material it reaches, (25) then light is absorbed and reflected 
based on the type of the material. Dark backgrounds absorb more light than lighter backgrounds 
which are expected to reflect more light instead. (26) Light absorption leads to fewer shadows and 
less edge and corners recognition, which affects the result accuracy accordingly. (27-30)  
Evaluation of accuracy of the auricular scanning done under different environmental 
factors compared to the conventional techniques is not well documented in the literature. So, this 
study aims to evaluate trueness of auricular scanning scanned with different types of backgrounds 
and skin tones The null hypothesis is that there will be no difference in trueness between different 
backgrounds with different skin tones. 
 
 

 
 
III- 
Research Question: 
Do different backgrounds and skin tones affect the trueness of auricular scanning scans? 
 
        Problem 
Lack of precise data on the trueness of auricular scans 
done under different backgrounds and skin tones. 
Intervention 
Auricular scanning by intraoral scanner with different 
backgrounds and skin tones. 
Comparator 
Scan of a cast obtained via conventional auricular 
impression by extraoral scanner. 
Outcome  
 
Evaluation of the effect of different backgrounds and 
skin tones on trueness of auricular scans via intraoral 
scanner. 
Time 
No follow-up period 
Setting 
 (Faculty of Dentistry, Ain Shams University) 
 
 
 
 
 
 
 
 

 
 
IV- 
Aim of the Study, Research Objectives, and Clinical Relevance 
Aim: 
This study aims to evaluate the trueness of auricular scanning scanned with different types of 
backgrounds and skin tones  
Outcome: 
Evaluation of the effect of different backgrounds and skin tones on trueness of auricular scans 
via intraoral scanner. 
Clinical Relevance: 
This study helps the dental practitioner to choose and adjust backgrounds according to different 
skin tones in the process of making auricular scans in order to achieve best accurate scans. 
V- 
Hypothesis 
The null hypothesis is that there will be no difference in trueness between different 
backgrounds with different skin tones. 
VI- 
Ethical consideration 
This study will be performed on healthy individuals without auricular deformity who come to 
the outpatient clinic to receive any dental treatment. The participant will have his dental treatment 
done for free. A conventional auricular impression will be made. Then a cast will be poured and 
scanned via extraoral scanner. Then each participant will have his auricle scanned via an intraoral 
scanner with a white background, a black background around his ear and with his own skin as a 
background.  
• Risks and Discomfort to Patients: There are no serious risks regards this study, however, 
mucosal irritation, slight pain, and discomfort are commonly related to conventional procedures 
during impression making. 

 
 
• Minimization of Risk: mouth rinses and oral gel medications will be prescribed in case of 
mucosal irritation. 
• Criteria for Discontinuation of Study or Enrollment or Modification of Intervention: In case 
of patient sickness, incompliance, or refusal to continue in treatment. 
• Privacy: Privacy for participants is protected by several procedures, such as informed consent 
and transparency in how patient data is accumulated and analyzed. Data will be kept in a specific 
folder on a computer with passwords known only by the main operator. 
• Confidentiality: Confidential data of the patients will be privately kept with the main operator. 
• Data Management: Data will be saved in a specific folder with passwords known only by the 
main operator on his personal computer. 
• Consent Procedures if Applicable: Before the provision of the procedures, each participant  will 
read and sign a consent form supplied by the ethical committee of the Faculty of Dentistry, Ain 
Shams University, written in the Arabic language. The consent describes the steps of each 
procedure, their rights, and their role in the study. The consent will be kept with the main operator. 
• Adverse Event Reporting: Any adverse reaction will be reported and written in the patients’ 
data folder. 
 
VII- 
Study design 
This is a comparative experimental study. 
VIII- Materials and methods 
Study settings: 
The study will be conducted in the Department of Oral and Maxillofacial Prosthodontics at 
the Faculty of Dentistry, Ain Shams University. 
Sample size: 

 
 
Sample size calculation was performed using G*Power version 3.1.9.7 based on the results 
of a previous study. (30) A power analysis was designed to have adequate power to apply a two-
sided statistical test to reject the null hypothesis that there is no difference between groups. By 
adopting an alpha level of (0.05) and a beta of (0.2), i.e. power = 80% and an effect size (d) of 
(0.289) calculated based on the results of a previous study. The predicted sample size (n) was 
(135), i.e., 45 samples for each of the three groups; and each group are divided into three 
subgroups. 
 
 
Study procedures: 
1- Sample grouping: 
This study will comprise three main groups based on participants skin tone type determined by the 
Fitzpatrick Scale. 
1. Group 1: Participant Type I 
2. Group 2: Participant Type III 
3. Participant Type VI 
Then each participant group will be stratified into four subgroups: 
o Subgroup 1.1: Auricular scan done via an extraoral scanner by making an auricular 
cast obtained by conventional auricular impression. 

 
 
o Subgroup 1.2: Auricular scan done via an intraoral scanner with a black background 
will be put around the ear. 
o Subgroup 1.3: Auricular scan done via an intraoral scanner with a white background 
will be put around the ear. 
o Subgroup 1.4: Auricular scan done via an intraoral scanner with no background will 
be put during the scan; participant skin is the background. 
2- Participant selection: 
Participants will be selected from the outpatient clinic of the Oral and Maxillofacial 
Prosthodontics Department, Faculty of Dentistry, Ain Shams University to acquire the models 
needed to accomplish this study. 
• Inclusion criteria 
1- Healthy individuals without auricular deformity who come to the outpatient clinic to receive 
any dental treatment. The participant will have his dental prosthesis done for free. 
2-Three types of skin tones will be selected; type I, type III and type VI according to The 
Fitzpatrick Scale. 
3-Participants not exposed to sun burns or tans. 
The Fitzpatrick Scale classifies skin into six types, ranging from very fair (Type I) to deeply 
pigmented (Type VI). It considers two primary factors: 
• 
Baseline skin color (without sun exposure). 
• 
Response to sun exposure, including the tendency to burn or tan. 
Skin Type Description 
Sunburn/Tan Response 
Type I 
Very fair, pale 
Always burns, never tans 
Type II 
Fair 
Usually burns, tans minimally 
Type III 
Medium 
Sometimes burns, tans uniformly 

 
 
Skin Type Description 
Sunburn/Tan Response 
Type IV 
Olive 
Rarely burns, tans easily 
Type V 
Brown 
Very rarely burns, tans darkly 
Type VI 
Dark brown/Black Never burns, deeply pigmented 
 
• Exclusion criteria 
− Uncooperative participants. 
_ Participants without intact ears. 
• Participant evaluation 
* History 
Medical and dental history will be taken from all patients. 
* Examination 
Comprehensive extraoral examinations will be carried out to verify participants fulfilling the 
selection criteria. 
3- Study procedures: 
After participants selection according to the aforementioned scale, they will be assigned to 
three groups, every participant will receive four types of intervention, the first type comprises 
of conventional auricular impression with a flowy impression material while being in a supine 
position with right ear facing upward. In order to preserve the external auditory canal intact, a 
piece of cotton roll will be placed in it. A ready-made open-sided cylinder from the top and the 
bottom will be used as an impression tray with an appropriate distance between the tray and 
the ear, allowing for sufficient thickness of the impression material. A flowy consistency 
impression mix will be applied to the ear’s internal surface and border. A second mix of 
impression with normal consistency will be loaded and placed passively over the first mix, 
filling nearly three-quarters of the tray. Dental plaster will be loaded after a complete set of the 

 
 
impression mate- rial to fill the upper portion of the tray. After the complete set of the plaster, 
the tray will be retrieved in a twisting movement in an outward, downward direction. Then the 
impression will be poured into stone, and the resultant cast will be scanned via an extraoral 
scanner. 
The participant will be given time for rest, then an intraoral scanner will be used to scan 
his ear with two different backgrounds made around his auricle from two different colours; 
black and white. Then the background will be removed, and scanning will be done this time 
with participant own skin as the background. 
 
The resultant standard tessellation files (STL) of every scan done via the intraoral scanner 
will be compared to the STL of the scan done via the extraoral scanner of the same participant 
by a metrological software to evaluate trueness. 
IX- 
Data Management 
The data will first be recorded manually and then transferred into digital form. The obtained 
data will be stored in the Oral and Maxillofacial Prosthodontics Department, Ain Shams University 
library. 
 
X- 
Statistical Analysis 
The collected data will be tabulated, and statistically analyzed using SPSS program (Statistical 
Package for Social Sciences) software version 23.0. Normality will be explored using the 
Kolmogorov-Smirnov and Shapiro-Wilk Test. Descriptive statistics will be done for numerical 
parametric data as mean±SD (standard deviation) and minimum & maximum of the range and for 
numerical non parametric data as median and 1st& 3rd inter-quartile range, while it will be done 
for categorical data as number and percentage. Inferential analyses will be done for quantitative 
variables using A one-way analysis of variance (ANOVA) when comparing between more than 
two means. Post Hoc test: Least Significant Difference (LSD) was used for multiple comparisons 
between different variables with parametric data and Kruskall Wallis test: for multiple-group 
comparisons in non-parametric data & Mann Whitney U in cases of two independent groups with 
non-parametric data. and Two-way ANOVA was used to study the effect of different tested 
variables and their interaction. Comparison of main and simple effects were done utilizing pairwise 
t-tests with Bonferroni correction. Inferential analyses will be done for qualitative data using Chi 

 
 
square test for independent groups. The level of significance will be taken at P value <0.050 is 
significant, otherwise is non-significant. The p-value is a statistical measure for the probability that 
the results that will be observed in a study could have occurred by chance. 
XI- 
Funding 
This study will be self-funded 
 
 

 
 
References 
 
1. Nishimura, R.D.; Roumanas, E.; Sugai, T.; Moy, P.K. Auricular prostheses and osseointegrated 
implants: UCLA experience.J. Prosthet. Dent. 1995, 73, 553–558. 
2. Guo, G.; Schwedtner, O.; Klein, M. A retrospective study of implant-retained auricular 
prostheses. Int. J. Oral Maxillofac. Implant. 2008, 23, 539–543. 
3-Ballo AM , Nguyen CT , Lee VSK . Digital workflow of auricular rehabilitation: A technical 
report using an intraoral scanner. J Prosthodont 2019; 28 (5):596–600 . 
4-Farook TH, Jamayet NB, Abdullah JY, Rajion ZA, Alam MK. A systematic review of the 
computerized tools and digital tech- niques applied to fabricate nasal, auricular, orbital and ocular 
prostheses for facial defect rehabilitation [Internet]. In: Jour- nal of Stomatology, Oral and 
Maxillofacial Surgery, 121. Elsevier Masson SAS; 2020. p. 
5- Beumer, J., III; Marunick, M.T.; Esposito, S.J. Chapter 5. Rehabilitation of facial defects. In 
Maxillofacial Rehabilitation, 3rd ed.; Beumer, J., III, Marunick, M.T., Esposito, W.J., Eds.; 
Quintessence Publishing Co. Inc.: Hanover Park, IL, USA, 2011; pp. 225–313. 
6- Konig, J.; Kelemen, K.; Czumbel, L.M.; Szabó, B.; Varga, G.; Borbély, J.; Németh, O.; Hegyi, 
P.; Hermann, P. Current status of optical scanning in facial prosthetics: A systematic review and 
meta-analysis. J. Prosthodont. Res. 2024, 68, 1–11. 
7- Liu H, Bai S, Yu X, Zhao Y. Combined use of a facial scanner and an intraoral scanner to acquire 
a digital scan for the fabrication of an orbital prosthesis. J Prosthet Dent 2019; 121 (3):531–4 
8- Elbashti ME, Sumita YI, Kelimu S, et al. Application of digital technologies in maxillofacial 
prosthetics literature: A 10-year observation of five selected prosthodontics journals. Int J 
Prosthodont. 2019;32:45–50. 12. 
9-Majid Z, Setan H, Chong A. Modelling human faces with non-contact three-dimensional 
digitizer–Preliminary results. Geogr Inf Sci. 2004;4:82–94. 
10-Ballo, A.M.; Nguyen, C.T.; Lee, V.S. Digital Workflow of Auricular Rehabilitation: A Technical 
Report Using an Intraoral Scanner J. Prosthodont. 2019, 28, 596–600. 

 
 
 
11-Dohiem MM, Emam NS, Abdallah MF, Abdelaziz MS. Accuracy of digital auricular 
impression using intraoral scanner versus conventional impression technique for ear rehabilitation: 
A controlled clinical trial. J Plast Reconstr Aesthet Surg. 2022;75(11):4254-4263. 
12- Ting-shu, S.; Jian, S. Intraoral digital impression technique: A review. J. Prosthodont. 2015, 
24, 313–321. 
13-Abduo, J.; Elseyoufi, M. Accuracy of intraoral scanners: A systematic review of influencing 
factors. Eur. J. Prosthodont. Restor. Dent. 2018, 26, 101–121. 
14-Almalki, A.; Conejo, J.; Wunsche, A.; Anadioti, E.; Blatz, M.B. Digital smile design and 
fabrication of CAD/CAM restorations in a complex esthetic case. Compend. Contin. Educ. Dent. 
2022, 43, 664–688. 
15-Unkovskiy A, Spintzyk S, Axmann D, Engel EM, Weber H, Huettig F. Additive manufacturing: 
A comparative analysis of dimensional accuracy and skin texture reproduction of auricular 
prostheses replicas. J Prosthodont. 2019;28:e460–e468. 
 16-Nuseir A, Hatamleh M, Watson J, Al-Wahadni AM, Alzoubi F, Murad M. Improved 
construction of auricular prosthesis by digital technologies. J Craniofac Surg. 2015;26:e502–e505. 
17- Mizumoto, R.M.; Yilmaz, B. Intraoral scan bodies in implant dentistry: A systematic review. 
J. Prosthet. Dent. 2018, 120, 343–352.  
18- Logozzo, S.; Zanetti, E.M.; Franceschini, G.; Kilpela, A.; Makynen, A. Recent advances in 
dental optics–Part I: 3D intraoral scanners for restorative dentistry. Opt. Lasers Eng. 2014, 54, 
203–221. 
19- Hwang, Henry Hann-Min; Chou, Chi-Wei; Chen, Yi-Jane; and Yao, Chung-Chen Jane (2018) 
"An Overview of Digital Intraoral Scanners: Past, Present and Future- From an Orthodontic 
Perspective," Taiwanese Journal of Orthodontics: Vol. 30: Iss. 3, Article 3. 
20- F. Eggmann1,2 and M.B. Blatz2, Recent Advances in Intraoral Scanners, Journal of Dental 
Research, 2024;103(13):1349-1357. 

 
 
21- International Organization for Standardization. Accuracy (trueness and precision) of 
measurement methods and results — Part 1: General principles and definitions. ISO 5725-1:1994. 
Geneva: ISO; 1994. 
22-C. Wesemann, H. Kienbaum, M. Thun, B.C. Spies, F. Beuer, A. Bumann, Does ambient light 
affect the accuracy and scanning time of intraoral scans? J. Prosthet. Dent. (2020).  
23-Brintouch I, Ali A, Romanos GE, Delgado-Ruiz RA. Influence of simulated skin color on the 
accuracy of face scans. Prosthesis. 2024;6(6):1372-1382. 
24- Arakida T, Kanazawa M, Iwaki M, Suzuki T, Minakuchi S. Evaluating the influence of ambient 
light on scanning trueness, precision, and time of intra oral scanner. J Prosthodont Res 
2018;62:324-9. 
25- Rey, M.; Volpe, G.; Volpe, G. Light, Matter, Action: Shining Light on Active Matter. ACS 
Photonics 2023, 10, 1188–1201. 
26- Mizuno, K.; Ishii, J.; Kishida, H.; Hayamizu, Y.; Yasuda, S.; Futaba, D.N.; Yumura, M.; Hata, 
K. A Black Body Absorber from Vertically Aligned Single-Walled Carbon Nanotubes. Proc. Natl. 
Acad. Sci. USA 2009, 106, 6044–6047. 
27- Akl, M.A.; Mansour, D.E.; Zheng, F. The Role of Intraoral Scanners in the Shade Matching 
Process: A Systematic Review. J. Prosthodont. 2023, 32, 196–203.   
28- Allred, S.R.; Olkkonen, M. The Effect of Background and Illumination on Color Identification 
of Real, 3D Objects. Front. Psychol. 2013, 4, 821.  
29-Varda, K.; Bešlagi´c, E.; Zaimovi´c-Uzunovi´c, N.; Lemeš, S. Ambient Light and Object Color 
Influence on the 3D Scanning Process.In New Technologies, Development and Application V; 
Karabegovi´c, I., Kovaˇcevi´c, A., Mandžuka, S., Eds.; Lecture Notes in Networksand Systems; 
Springer International Publishing: Cham, Switzerland, 2022; Volume 472, pp. 37–45. ISBN 978-
3-031-05229-3. 
30-Brintouch I, Ali A, Romanos GE, Delgado-Ruiz RA. Influence of simulated skin color on the 
accuracy of face scans. Prosthesis. 2024;6(6):1372-1382.