1 INTRODUCTION

Students seek various knowledge to form the basis of their medical education and apply that knowledge in clinical practice. Moreover, they learn and acquire basic dental skills from educators. However, simulation-based education is equally important; for a long time, it enabled theoretical learning through the utilization of off-the-shelf models, and dentistry students acquired practical education through the treatment of patients.1 Usually, off-the-shelf models are used with epoxy resin for teeth and bones and polyurethane for gums. However, educators need to help students find the connections between the theoretical and practical aspects of education. Thus, several approaches have been designed and attempted worldwide to aid this connection.2-4 Crossover of information between the dental sphere and other health care disciplines in the development of simulations has been limited.1 Therefore, it is important to acquire various knowledge and technique through simulation.

In the Department of Oral and Maxillofacial Surgery at our institution, patients with maxillofacial deformities are treated by surgery after careful preoperative planning, including relevant orthodontic discussions. Previously, paper surgery using two-dimensional cephalometric measurements and model surgery was performed.5 However, more recently, dedicated computerized software-based digital simulations have been used,6-10 which allows software-based analysis of the computed tomography (CT) data of the patient by simulation. Simulations using such CT data will help in treatment planning in orthodontics and orthognathic surgery.11 In addition, there is also a method of improving the simulation accuracy by merging other three-dimensional (3D) images.12 These images help in the fabrication of the bite splints required during surgery. This is achieved by combining the intraoral data of the patient captured using a 3D scanner.6, 8, 13 However, these techniques are still at the research stage and have not been used as proactively as is expected in the future. Therefore, dentists who are capable of using these techniques and devices need formal training on their application for future purposes. Certainly, the training in dental treatment is being conducted in trials using 3D-printed models, and training using these models is now being conducted in oral surgery. We hypothesized that the educational effect would be improved by effectively conducting training using maxillofacial simulation software (MSS) and a 3D-printed model. This simulation-based research is reported in accordance with the guidelines of Cheng et al.14

2 MATERIALS AND METHODS 2.1 Participants

At our institution, undergraduate dentistry students in the Department of Oral and Maxillofacial Surgery were provided clinical practice education, including medical consultations with patients, observation of major and minor surgeries, including tooth extractions. This was followed by formative and comprehensive assessments by the educators. The training program was conducted individually in various departments (operative dentistry and endodontics, periodontics, prosthodontics, orthodontics, pediatric dentistry, etc.) over 1 year. When students were free to choose during this period, we implemented a new curriculum, in addition to the formative assessment that was in use for students choosing oral surgery as their department. The participants were 5th-year undergraduate students. The validity of the curriculum content was evaluated by comparing it in two different curricula (in 2017 and 2018). One had the simulation lecture curriculum (SLC) with 13 students participating in 2017. The other type had the self-simulation curriculum (SSC) in 2018, with 11 students participating. These curricula were the new trial. This study is a cross-section in design.

2.2 3D Printing

CT data from healthy individuals (a researcher's personal CT data) were used in these curricula. This CT data was provided by a researcher himself, and this has been approved by the Institutional Review Board of our institution. The MSS software Pro Plan CMF (Materialise, Leuven, Belgium) was used. The maxillofacial 3D-printed model was made by Objet 260 Connex (Stratasys, Eden Prairie, MN, USA). The cortical bone part was composed of acrylonitrile butadiene styrene-like material (RGD835 VeroWhitePlus; Stratasys), and the bone marrow part was a support material (SUP705B; Stratasys) (Figure 1).

The maxillofacial simulation software Pro Plan CMF: Osteotomy is customizable for each case. The maxillofacial three-dimensional-printed model is made by Objet 260 Connex: This model can be split like the jaws. The cortical bone part is composed of acrylonitrile butadiene styrene (ABS)-like material, and the bone marrow part is a support material

2.3 Evaluation method

To evaluate the educational effect of this method, a test with a maximum score of 20 was conducted before and after practical training. Students were questioned on similar problems in both curricula. The answers to the test questions were collected immediately to prevent discussions of answers among students. A 4-point assessment questionnaire before and after the curriculum and a subjective assessment were also administered. A t-test was performed on the average scores of the pre- and post-curriculum tests. The p-value was set at 0.01. The test questions consisted of 20 technical and anatomy questions (maximum score of 20 points), which were difficult to learn through the normal curriculum (Figure 2).

The test consisted of 20 technical and anatomy questions (maximum score: 20 points) about the Le Fort I osteotomy and bilateral sagittal split osteotomy. The test was conducted before and after the practical training. This knowledge is otherwise difficult to learn through a normal curriculum

We conducted the questionnaire to examine the students’ understanding. It was before training and immediately after training and was conducted for each curriculum. The questionnaire contained six items and was assessed on a 4-point scale (Figure 3). The average score was calculated for each item in the questionnaire before and after the training, and the t-test was performed. The p-value was set at 0.01. Prior to this study, the pilot test was conducted to examine the validity of the questionnaire.

The questionnaire was assessed on a 4-point scale and consisted of six items about self-understanding of the practical training. This was conducted before and after the practical training

For the statistical analyses, the IBM SPSS Statistics 19 (IBM SPSS, Turkey) program was used to assess the results. We performed normality testing before the actual analysis and confirmed that it was normally distributed.

2.3.1 Simulation lecture curriculum

A total of 13 students participated (seven male and six female) in 2017. First, the educators conducted the lecture using Pro Plan CMF such that the students could view the simulation. The simulations involved Le Fort I osteotomy and bilateral sagittal split osteotomy. The lectures included the descriptions of the dissection and the operative procedure followed by practical training on osteotomy that was conducted using the maxillofacial 3D-printed model, as well as the actual surgical instruments. This practical training was directly led by the expert surgeons from the Japanese Society of Oral and Maxillofacial Surgery (Figures 4A and 5).

(A) The simulation lecture curriculum (SLC): The educators conducted the lecture using Pro Plan CMF such that students were able to view the simulation of the Le Fort I osteotomy and bilateral sagittal split osteotomy. After the lecture, practical training on osteotomy was conducted using the maxillofacial three-dimensional-printed model and actual surgical instruments. The students are wearing white medical uniforms, and the educators are wearing blue medical uniforms. (B) Self-simulation curriculum (SSC): The students were asked to bring their personal computers and install the Pro Plan CMF software. Following the installation, they went through the simulations of the Le Fort I type osteotomy and bilateral sagittal split osteotomy individually. They conducted practical training on osteotomy using the maxillofacial three-dimensional-printed model and actual surgical instruments as in the simulation lecture curriculum. The students are wearing white medical uniforms, and the educators are wearing blue medical uniforms

Study protocol flow chart. Simulation lecture curriculum (SLC) and self-simulation curriculum (SSC) were implemented in different years, and osteotomy practical training was conducted similarly

2.3.2 Self-simulation curriculum

A total of 11 students were involved (four male and seven female) in 2018. First, the students were instructed to bring their personal computers (PCs) and install the Pro Plan CMF software. They were asked to glance through the simulations of the Le Fort I osteotomy and bilateral sagittal split osteotomy individually on their PCs after being instructed on the procedure for operating the software. Subsequently, practical training was conducted on osteotomy using the maxillofacial 3D printed model along with actual surgical instruments, as in the SLC (Figure 4B and Table 1).

TABLE 1. The simulation lecture curriculum (SLC) students showed a significant difference in the students’ understanding of instruments (Question-5: I was able to understand how to use surgical instruments in practical training), and the self-simulation curriculum (SSC) students showed a significant difference in the students’ understanding of surgical techniques (Question-3: I was able to understand the surgical method in the practical training). Furthermore, all post-training questionnaires of the SSC had higher average scores than those of the SLC SLC SSC Question Pre Post ｔ Pre Post ｔ 1 3.54 3.62 0.42 3.64 3.91 1.35 2 3.08 3.62 1.91 3.27 3.82 1.82 3 3.23 3.77 2.34 3.45 4.00 3.01* 4 3.15 3.54 1.73 3.36 3.91 2.04 5 3.15 3.77 3.07* 3.45 3.91 2.03 6 3.23 3.85 2.66 3.55 4.00 2.59 2.4 Correspondence to students

Prior to the study, we explained in writing that these curriculums did not affect student grades. In addition, only students who gave their consent to participate were included. The curriculum also included dentists from the Department of Oral Surgery to support simulation and training. Students received knowledge and technical feedback from the instructor after training.

3 RESULTS

In the SLC students, the average pre- and post-test scores were 14.9 and 15.3 points, respectively. In the SSC students, the average pre- and post-test scores were 15.5 and 17.8 points, respectively. Both the SLC and SSC students showed increased average scores after practical training. Among the SSC students, there was a significant difference in the difference of average scores, thereby demonstrating that understanding was deepened as students individually went over the simulations (Figure 6).

Both simulation lecture curriculum (SLC) and self-simulation curriculum (SSC) students had increased average scores after practical training Among SSC students, there was a significant difference in the difference of average score

In the questionnaire, the SLC students showed a significant difference in question-5 “I was able to understand how to use the surgical instruments in practical training”, and the SSC students showed a significant difference in question-3 “I was able to understand the surgical method in practical training.” Furthermore, all post-training questionnaires of the SSC had higher average scores than those of the SLC. These findings suggest that self-simulation, followed by practical osteotomy helped deepen the understanding of the procedure (Table 1). In addition, in the “free comment” section of the SSC questionnaire, students provided responses, such as “I was able to sufficiently understand the 3D positional relationship, which could not be understood by simply observing the surgery,” “I was able to understand the anatomical positional relationship”, and “I was able to gain a deep understanding of the surgical instruments.” We also observed increased interest among students, saying, “If there is a next time, I would like to tell others about it.”

4 DISCUSSION

The medical education scenario has undergone massive changes. Traditionally, lectures presented by the educators were the primary source of knowledge for medical students, followed by learning the basic techniques before gradually engaging in the patient's treatment. Currently, there are many treatments using 3D printing, 3D scanners, and image analysis software due to advances in medical care; however, the application of 3D printing, 3D scanners, and image analysis software for the purpose of medical education is rare since they are still in the development stages.1, 15, 16

In the context of education, evoking and retaining the focus/interests of students is crucial for educators. Currently, students utilize smartphones and tablets for learning. This indicates the need for educators to adjust with the use of PC and adopt novel methods to make lectures attractive and respect the circumstances of the time. One significant source of education today is YouTube, as it offers web-based education that is simple and easy for students. With YouTube, even educators can easily establish a virtual patient group.17-20 However, there is no means to verify the open-source transmission of videos, and it is difficult to assess the students’ understanding of the content, which will eventually require evaluations by the educator through the observation of their practical skills. Furthermore, this was not entirely different from the content of face-to-face lectures, except students and educators were not affected by time constraints. The study found that SLC, which was similar to watching YouTube, was less understood than SSC. This proved that even if the latest devices were used, students would not be able to improve their understanding without devising a lecture method.

Virtual reality (VR)-based education is also available. Students are provided an almost real experience of medical procedures through VR video viewing.4, 21, 22 This VR device can efficiently attract the interest of students. Furthermore, education is also imparted through simulation-based devices, which students can use to perform simulations using instruments similar to that used in the actual clinical practice while viewing the VR footage, which allows them to have almost real experiences of healthcare facilities.23 However, the challenge remains regarding the evaluation of students’ understanding of VR-based educational content as that with YouTube-based learning. Despite this, the present study was able to supplement knowledge, such as the purpose of the instrument rather than the experience of surgery by using the actual instrument.

Education using state-of-the-art digital technologies is very useful for evoking the interest of students. However, students of the current digital generation memorize such operations and are unable to cope with the events encountered practically. Such problems can be attributed to the lack of prior planning. Therefore, students should clearly understand the key aspects of operative procedures before performing them and know the circumstances necessitating certain operative procedures. Nevertheless, the best way to learn surgery is through practical experience.24-27 In the present study, we found that the interest in further knowledge increases as the knowledge of anatomy and surgery is acquired. We believe that this is a great advantage of face-to-face lectures. Although simulation software, YouTube, and VR are worth using, we thought it would be preferable to use them as a teaching aid.

To date, off-the-shelf models have been used in basic teaching techniques.1 However, because these models are ready-made, they are unsuitable for the simulation of difficult operative conditions. Unfortunately, developing new off-the-shelf models that consider difficult medical situations would involve significant investment costs and be extremely time-consuming.28 Therefore, with this training, we planned a study based on the simulation software related to orthognathic surgery, which has recently been standardized.6-9, 29 The self-fabrication of the maxillofacial model by a 3D printer possibly reduced its development time for it to be used for practical training. These could be customized freely for easy teaching. Until now, we have been educating students using 3D-printed models; however, developmental skills and sound knowledge of human anatomy are necessary.26, 20-25, 27-33 For this study, performing simulations using the MSS initially and then executing the planned surgical osteotomy procedure ensured that students improved their skill set and understanding of anatomy. Furthermore, they could deepen their understanding of the details of surgery by recognizing the importance of surgical planning, along with the materials and the techniques used.

From our experience, we emphasize that practical hands-on training and learning can improve the knowledge of students. The 3D-printed models could also make a great contribution as teaching materials. The educational effect could be improved by using both the written materials and the 3D-printed models.15 However, combining the cadaveric materials and the 3D-printed models would reduce the educational effect.16 The 3D-printed models alone do not impose any disadvantages on students, but they allow them to grasp the knowledge of only the important parts. By clarifying the scope of teaching for the students using software like our curriculum, the effects of learning would be further improved.

This training curriculum was planned with an emphasis on the following: (1) evoking the interest of students of the digital generation, (2) using a device that can be operated intuitively like a video game, (3) simplifying the treatment planning process for the student's understanding, and (4) executing operative procedures using instruments as in actual treatment conditions. The students understood the MSS quickly because it could be operated intuitively. They acquired the technical skills through a one-hour lecture and could glance through the planning lecture easily thereafter. We thought introducing a new software program to the students would hinder their learning; however, since most recent software applications are user-friendly, they were not burdensome to the educator. We believe that 3D printing, 3D scanners, and image analysis software currently used in clinical practice are extremely useful for education; hence, their active use in education is recommended, which will not only facilitate simulation software and 3D-printed model-based treatment in the clinic but also promote further research.

ACKNOWLEDGMENTS

We are grateful to Dr. Satoru Matsunaga (Department of Anatomy, Tokyo Dental College) for his assistance in this study. This study was supported by the Tokyo Dental College President Encouragement Education Grant. This grant was awarded in April 2017 and covered the student education.

CONFLICT OF INTEREST

The authors declare no conflict of interest.