Currently, the development of technological advances has driven the development of educational content using third-dimensional technology, thus impacting the teaching of dentistry in a significant manner. This implementation has facilitated the updating and improvement of the teaching-learning process in the subjects that require the student to develop clinical competences.
Objective:To evaluate the impact of the contents of the 3D teaching material on the prevention of dental decay and malocclusions in childrenranging between 6 to 12 years, taught to students of- Preventive Dentistry and Public Health I at the school of Dentistry UNAM.
Method: "Preventive measures for dental caries in children aged 6 to 12 years on pits and fissures sealants" was taught. A total amount of 164 students were divided into two groups randomly: group A, the subject was taught in a traditional way. On the other hand group B was taught through a video designed with 3D images. The learning was evaluated within 24 hours by means of a questionnaire consisting of 14 multiple-choice questions using the Likert scale.
Results:The average group A was evaluated by means of the Likert scale (traditional teaching) was 24.78 (SD = 5.6), whereas B (3D) was 37.66 (SD = 2.8). The average rating of group A was 7.03 (SD = 0.9) and that of group B (3D) was 8.82 (SD = 0.7), in both cases the differences were statistically significant for a p = .001.

Conclusions:The output educational content which emerged after the use of3D allow the handling of a large amount of information in a broad and immersed display without cognitive filtering through multiple and flexible representation, promoting in the students the unification of the cognitive part with the procedural part.

Keywords:Learning of clinical techniques, 3D educational material, Traditional teaching

Introduction
The representation and simulation (stereoscopic) of objects and images in 3D (3D) uses a real virtual reality system that allows the recipient to have the sensation of depth generated from different images projected alternately for the right and left eye [1]. The quality of the training on heath human resources has been the subject of concern in the universities, as well as on the sufficient and necessary practical experience required forthe student, has determined the updating of the curriculum. The profile of the learning goes from the acquisition of theoretical knowledge all through the integration in practice and finally the demonstration of competence through the application. In order to keep in mind a large proportion of this knowledge is strongly demanding, so that the knowledge of simulationscan be eventually be applied to real experience. Dental education is based on this simulation, together with the fact of having trained teachers in the management of specialized equipment and use of innovative methodologies to increase the probability of patient safety on the part of the future professional [2].
The teaching of Medicine has evolved, from the decade of the sixties, towards new forms of teaching and learning; Problem-based learning (ABP) evidences (ABE) in which the curriculum was focused on the student and the teacher as a facilitator of the teaching-learning process, expecting that the students learn from the real world knowledge and the accumulation of experience based on their  own learning. The whole process starts by presenting a problem with numerous evidences to demonstrate the effectiveness of this technique [3]. In this sense, Dentistry has followed the same steps since the use of software has facilitated better diagnoses and planning of orthodontic treatments, [4]This may even be applied in the diagnosis and treatment of temporomandibular dysfunction; [5]In addition, the teaching-learning of conceptual contents and management of dental materials to mention a few. In the volumetric images, the anatomical and dental areas that facilitate the multiplanar (2D) reconstruction of the scanned volume are visualized with great precision, that is, the visualization of the images in the three planes of space: axial, sagittal and transverse as well as the 3D reconstruction. All such images have been very useful in different areas of Dentistry such as Surgery, Implantology, Periodontics, Endodontics and Orthodontics [6-8].

Studies such as the one conducted by Abid and Jean-Marc confront the teaching of peritoneal embryogenesis in a traditional way where memorization is the result of this teaching model and show that the use of 3D technology is significantly more efficient than traditional to achieve the objectives In terms of short and long term, in particular for the assimilation of dynamic phenomena and emphasize that short and long term studies are necessary to demonstrate that this benefit has a long lasting effect. Variables such as motivation and performance of the students lead to investigate the effect of teaching based on 3D simulation and verify that learning based on these variables favors students to perceive their basic psychological needs that must be met and can substantially improve learning in general[9,10].
In fact, Dale [11] has mentioned that learning is related with the participation in simulations since it allows to learn in a more efficient way.

The results obtained from the use of tools that showinterconnection betweenE-Learning platforms (at a distance) with 3D scenarios have created learning spaces whichhave significantly enhanced the joint work and, therefore, the collective knowledge since they were achieved levels of participation and generation of knowledge more complete in the process with students who attended this project based on 3D than with traditional classes because the learning curve of use of the 3D platform is quite effective and for teachers this means It is of great importance and creativity since it allows to design innovative practices in a virtual space [12].

The study was divided into two stages: in the first stage, the film and 3D photography equipment was acquired as cameras, video accelerator card, computers and printer. Three recording techniques were developed to obtain clear images of dental structures, to form a bank of images and videos in 3D on prevention of dental caries based on the control of biofilm and placement of sealants of pits and fissures in children from 6 to 12 year old. Content and image criteria were unified, as well as the duration of each image in the exhibition of clinical aspects of caries so that the student could differentiate the existing characteristics between normality and abnormality and knew, step by step, the technique of placement of the sealants For the 3D material corresponding to pits and fissures, extracted natural teeth were used that were cut in a digital sense so that the student knew, in a natural model, the topography and characteristics of the pits and fissures. In the second stage, the evaluation of learning about dental caries prevention was carried out using 3D teaching materials. The study involved 164 students who at the time of the study were regular students enrolled in the first year of the Dentist Surgeon Career at the School of Dentistry of the UNAM to evaluate the learning of the topic "Preventive measures for dental caries in children from 6 to 12 years old through the placement of pit and fissure sealants." The students were randomly divided into two groups: group A was taught the subject using the traditional teaching technique based on rigid images projected on the blackboard and later the teacher demonstrated the technique by placing the sealants of pits to the students in the clinic. Group B was formed by students who were taught the same subject through a video designed with stereoscopic and threedimensional images in the 3D room of the School of Dentistry [13]. The learning in both groups was evaluated 24 hours after the subject was given through a questionnaire consisting of 14 multiple-choice questions (validated by experts) using the Likert scale. Both questionnaires evaluated the same contents. The questionnaires corresponding to the Likert scaling included three response options: in agreement, neither agreement nor in disagreement and in disagreement, the correct answer was always qualified with threepoints and the incorrect one point, if the answer was neither agreement nor disagreement it was qualified with two points.
The questionnaires were evaluated by a panel of nine expert teachers in the area of teaching of Preventive Dentistry and Public Health I that were selected with well-defined criteria: teachers who taught the topic subject to evaluation and who had a minimum of 10 years of teaching seniority in the area, who have participated in the design of the study program of the Subject of Preventive Dentistry and Public Health I and its annual review.
The information was analyzed descriptively and the student test was applied to determine if there were statistically significant differences between both educational techniques.

The average group score in the questionnaire designed with the Likert scale of group A (traditional teaching) was 24.78 (SD = 5.6) and in group B (3D) the group average was 37.66 (SD = 2.8) (Graph 1). Regarding the average score obtained with the questionnaire designed with multiple choice answers, group A (traditional teaching) obtained an average of 7.03 (SD = 0.9) and only 1.22% obtained the highest grade, 2.43% presented the minimum grade, the average of group B (3D) was 8.82 (SD = 0.7) (Graph 2). The minimum grade in this group was 5.7 and the maximum was 8.8, 18.29% of the students obtained the minimum grade and the 7.31% obtained a grade of 8.82.
The statistical analysis showed that the differences in the score with the evaluation in the form of Likert scaling between group A and group B are statistically significant. t = -18.540, p = .001, IC95% = -14.253 - -11.503) and the difference in grade obtained between both groups with multiple choice questions were also statistically significant: t = -13.297, p = .001, IC95% = -2,059 - -1,526).

The virtual scenarios managed with three-dimensional images make it possible for the viewer to be immersed in models close to reality, this allows that even after a lapse of time the concepts, processes and the articulation of elements or parts can be remembered, in this study it was It is evident that the students managed to start the short-term memory with the teaching of the theme "Preventive measures for dental decay in children ranging6 to 12 years of age by placing sealants of pits and fissures" and the scores obtained in the evaluations show that the differences are attributable to the method and its contents; results that reaffirm that published by other authors [7-11]. The corresponding information of the advantages of dental enamel engraving was significant for a greater number of students when they witnessed the technique of placing sealants of pits in this continues to comply with the proposal by Dale[11]. In this study, the totality of students who received the teaching of the technique of placing sealants of pits and fissures by means of 3D lenses, observing the images of the digitized dental arches that rotated and articulated, knew the topographic characteristics of the pits and fissures of cuspid teeth, also clearly observed the obvious destruction of dental tissue due to the carious process that sits in the fissures when the anaerobic microbial population is present in them and above all, they managed to differentiate the normality of the abnormality. On the other hand, those who participated in this academic experience with the traditional teaching technique had serious problems when the teacher summoned them to give the explanation in the clinic since when they were placed around the dental unit occupied by a patient to observe, step by step , the procedures of the technique only the students closest to the dental unit had a better visual and auditory access of the explanation of the teacher, not so the students that were outside the visual radio, this without counting that variables such as height and use of glasses were some important limitations. In this model of teaching not all students can visualize the practice and only those who were in front of the dental unit and in the first row observed the simulation of the technique of sealants of pits, therefore, if we want to raise the quality of the dental care is necessary to be trained in the management of specialized equipment and didactic methodologies of great coverage [12,13].

In Dentistry the learning of clinical techniques through didactic sessions using 3D material promotes a more complete learning, with more quantity and quality of information. Short-term memory allows to compare the advantages and disadvantages of clinical techniques and the student can remember more information by bringing to mind the images of anatomical models, study and clinical characteristics of a disease such as dental caries to achieve a long-term learning Thanks: We strongly thank the Support Program for Innovation and Improvement of Teaching for financial support in the realization of this project.

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