A Comparison of Accuracy Between Different Facial Scanning Techniques

• Study Setting: The study will be conducted in the Oral and Maxillofacial Prosthodontics Department.

• Sample Size Calculation: Sixty participants will be selected to share in this study from the outpatient clinic of Prosthodontics Department, Faculty of Dentistry, Ain-Shams University. G power program (3. 1) was used for calculations of sample size. Statistical calculator was based on 95% confidence interval and power of the study 80% with α error 5%.

According to a previous study done by Nuytens et al. " Trueness and precision of a handheld, a desktop and a mobile 3D face scanning system: An in vitro study"

• Eligibility criteria: Inclusion Criteria Those who completed growth. Exclusion Criteria

1- Men with beards. 2- Those with maxillofacial deformity Justification for Exclusions (Those will interfere with the scan)

• Randomization and allocation concealment technique:

Randomized Controlled Trial (RCT) Randomization will be guided by a computer-generated list. The groups will be placed in numbered closed opaque sealed envelopes according to the computer-generated list of random numbers and an envelope will be allocated to each patient. Double blinding will be done by one of the postgraduate students who will be the only one to know the key so that the authors and the patients won't know in which group the patient will be. Afterwards, the authors will be informed by the randomization to be tabulated.

• Details of the interventions, testing and follow up The total of 60 scans will be analyzed using (Geomagic metrology software). Fourteen inter-landmark distances will be digitally measured to assess three facial regions-upper, middle, and lower face-and categorized into vertical and horizontal dimensions. This boundary will be replicated on each of the experimental scans using a best-fit alignment technique. For each distance, trueness will be calculated as the mean absolute deviation from the reference measurements across all scans for each modality. Precision will be assessed by computing the standard deviation of the repeated measurements for each distance.

The patients will be divided into three groups; group (I), group (II) and group (III).

In all groups; 14 landmarks will be taken as reference points at the following positions: glabella (g), right exocanthion (exR), left exocanthion (exL), right endocanthion (enR), left endocanthion (enL), pronasale (prn), right alare (alR), left alare (alL), subnasale (sn), labiale superius (ls), labiale inferius (li), right chelion (chR), left chelion (chL), pogonion (pg).

In all groups, A reference scan will be acquired in the form of a cast driven through alginate impression, then the cast will be scanned by desktop scanner. Scanning will be exported as a standard tessellation language (STL).

3D face scanning systems: Three scanning modalities will be tested. All scans will be conducted by the same operator in identical lighting, temperature (24°C), pressure (760 mmHg), and humidity (45%) conditions. In all scans, the head position will be standardized by a head-chin rest.

Group I: Handheld scanner (Metismile; Shining 3D, China):

Uses an infrared structured light system with a VCSEL projector. It contains three 1.3 MP cameras for data acquisition and one 5 MP texture camera. A series of scans will be taken each session took about 35 seconds. Scans will be captured according to manufacturer calibration protocols, processed in HD mode, and exported as PLY files.

Group II: Desktop scanner (RAYFace v2.0; Ray Co., Korea):

Employs white and blue structured light technology combined with depth and infrared sensors. The scanning duration will be approximately 0.5 seconds per scan. The scan will be taken following manufacturer guidelines, and scans will be exported in PLY format after HD processing Group III: Mobile face scanning application (Heges; Marek Simonik) on a smart device (iPad Pro X, Apple Inc., Cupertino, CA) It has a True Depth camera utilizing VCSEL technology, projecting 30,000 IR dots for depth mapping at a working distance of 300-450 mm. A tablet stand will be used for stability.

• An experienced single calibrated operator is going to do all the scans for each technique.
• Blinding techniques Single blinding will be done for the outcome assessor.

Method of evaluation:

A total of Sixty scans will be analyzed using (Geomagic metrology software). Inter-landmark distances will be digitally measured to assess three facial regions-upper, middle, and lower face-and categorized into vertical and horizontal dimensions. This boundary will be replicated on each of the experimental scans using a best-fit alignment technique. For each distance, trueness will be calculated as the mean absolute deviation from the reference measurements across all scans for each modality. Precision will be assessed by computing the standard deviation of the repeated measurements for each distance.

IX. Statistical Analysis The data will be collected, arranged, and tabulated to be statistically analyzed.

Inclusion criteria

• Those who completed growth

Exclusion criteria

• Men with beards.
• Those with maxillofacial deformity