This quasi-experimental, single-blind study evaluated 4th year volunteer dental students of School of Dentistry of Kermanshah University of Medical Sciences in 2018-2019. The students had passed the theoretical course of lateral cephalometry and were selected using census sampling. This study was conducted during the second semester of the 2018-2019 academic year and introduced the use of a mobile application to compare the efficacy of traditional learning versus smartphone-based mobile learning for instruction of cephalometric landmark identification to dental students. Sample size was calculated to be a minimum of 26 students in each group according to a study by Silveira et al, , standard deviation of knowledge score to be 2.87 and 2.61 in the traditional learning and smartphone learning groups, respectively, accuracy (d) of 2.5, alpha=0.05, and power of 90%.
The study was approved by the ethics committee of Kermanshah University of Medical Sciences (IR.KUMS.REC.1397.791). The students were ensured about the confidentiality of their information, and signed informed consent forms prior to participation in the study. All the volunteers were enrolled in the study except for those who reported previous knowledge/training in lateral cephalometric landmark identification. The volunteers were informed that evaluation of their performance in this study would have no effect on their final grade in this course. The study was conducted in the Orthodontics Department by an expert orthodontist. All participants received basic theoretical training regarding lateral cephalometric analysis. The educational program consisted of 2 hours of lecture-based learning that focused on theoretical learning regarding lateral cephalometric analysis. The students were then randomly divided into two groups of intervention (smartphone-based mobile learning) and control (lecture-based learning). The educational contents were the same in both groups and focused on tracing of lateral cephalograms and landmark identification.
Intervention group (n=27): Dental students in the intervention group were provided with a smartphone application. This mobile app was designed for the Android operating system to educate the students regarding the identification of landmarks on lateral cephalograms according to the chapter 4 of the Radiographic Cephalometry: From Basics to 3-D Imaging, 2nd edition, by Alexander Jacobson and Richard L. Jacobson in 2007 . The app included seven main topics for cephalometric tracing namely (I) general considerations, (II) marking the soft tissue profile, and outlining the external border of the skull and vertebrae with three subtopics of outlining the soft tissue profile, outlining the external border of the skull in the anterior region from the frontal to the nasal bone, and in the posterior region in the occipital bone, and outlining the first and second cervical vertebrae (C1 and C2), (III) outlining the base of the skull, internal margin of the skull, frontal sinus, and porion, with subtopics of outlining the base of the skull, roof of the orbit, sella turcica, sphenoidal platform, frontal sinus, dorsum sellae, the foramen magnum, the floor of the middle crania fossa and porion, (IV) outlining the maxilla and its related structures in subtopics of nasal bone, piriform foramen, infra-orbital ridge, key ridge, pterygomaxillary groove, anterior nasal spine, nasal floor, posterior nasal spine, maxillary first molars, maxillary anterior region, and maxillary incisors, (V) outlining the mandible with the subtopics of anterior symphysis, symphyseal bone marrow, inferior border of the mandible, posterior ramus, condyles, coronoid and sigmoid notch, anterior ramus, mandibular first molars, and mandibular incisors, (VI) identification of cephalometric landmarks with the subtopics of ANS, Ar, Ba, Bo, Gn, Me, N, Or, PNS, Pog, Po, point A, point B, PTM and S, and (VII) drawing the anatomical planes.
Each topic was clickable to access the subtopics. By clicking on each subtopic, an educational video clip recorded by a skillful instructor (orthodontist) would be played with audio explanations of the practical steps in cephalometric analysis. Written explanations would also appear in a side bar. The user could choose to view the entire text by selecting the continuous scroll. This classification in presentation of topics was intended to enhance the access of users to different topics and accelerate their learning process. One of the authors (F. D.) personally installed the app in the smartphones of students and provided them with the necessary instructions on how to use and navigate it. During the practice time of cephalometric tracing, the mentors supervised the students working with the app and using the pamphlet. The two groups were scheduled for practice at different days. Also, they were strictly requested not to share the educational contents with the other group.
Control group (n=26): Dental students in the control group received the same educational content as did the intervention group in a classroom setting in the form of a 2-hour workshop and also received a pamphlet with the same educational content as in the smartphone application, in order to be able to review the taught topics later.
The students had 10 hours of self-study by use of the mobile app or traditional models, depending on their group allocation. Both groups were requested to study the educational contents during their regular attendance in the orthodontics department for 10 h under the supervision of instructors. Two-week time was allowed for the students in the intervention group to use the application and for the students in the control group to review the taught topics and then both groups participated in a test to assess their expertise in cephalometric landmark identification (Figure 1). Lateral cephalogram of an orthodontic female adult patient with no cleft lip/palate, no supernumeraries, no missing teeth, no anatomical anomalies, no severe asymmetry, no skeletal dysplasia requiring orthognathic surgery, and no use of denture or dental splint was demonstrated to dental students and they were asked to trace the cephalogram and identify four landmarks. The aforementioned four landmarks were selected by two orthodontists and one radiologist in a group discussion and included the posterior nasal spine (PNS), articulare (Ar), gonion (Go) and orbitale (Or).
PNS: The most posterior point on the sagittal plane of the hard palate on the mid-sagittal plane
Ar: A point at the intersection of the image of the posterior margin of the ramus and the outer margin of the cranial base.
Go: The outer point on either side of the lower jaw at which the jawbone angles upward.
Or: The most inferior point of the inferior border of orbit.
The lateral cephalogram was taken by Cranex 3D (Soredex, Tuusula, Finland) and printed by a laser printer (Dry view 5950; Kodak, USA) using 8×10 inch Kodak medical X-ray film.
The X and Y coordinates of each landmark identified by dental students were compared with the reference points identified by the orthodontists. The mean distance between the identified landmark and the reference point was calculated and reported as the mean consistency while the standard deviation of this mean was reported as the accuracy of measurement for each group (Figure 2).
Data were analyzed using SPSS version 18 (SPSS Inc., IL, USA). Normal distribution of data was evaluated using the Kolmogorov-Smirnov test, which showed that the data were normally distributed. Thus, the two groups were compared using independent sample t-test. The Chi-square test was applied to assess the correlation of gender and study group. Level of significance was set at 0.05.