The study was formulated as a randomized unblinded educational intervention of pre-clinical teaching for a period of one year. The participants were 75 first year dental undergraduate students from Faculty of Dental Sciences, Sri Ramachandra University, Chennai, Tamil Nadu, India. The students were divided into three groups namely Group A, Group B and Group C (n=25) using systematic random sampling. The sample size and power of the study was arrived with a ratio of 1:1 using assumed mean score of 60 points and an improvement 7 points for the groups with a standard deviation 8 and 9, and was computed using the software from Open Source Epidemiologic Statistics for Public Health version 3.01. All students who participated in the study had no prior exposure to any teeth arrangement skill and had zero baseline knowledge in the field of dentistry. This study was an evaluation of the teaching methodologies that are routinely practiced in the pre-clinical laboratory in all the dental institutions throughout the country and has been recognised by the Dental Council of India. It did not incorporate any additional or new methods, which could affect students’ work schedule. The skill that was evaluated was a part of the pre-clinical curriculum that the students are expected to perform in the first year B.D.S. The study did not involve any ethical issues that will be experienced by the student participants, as it did not interfere in any personal issues or require extra time from the students as the study was carried out during the allotted laboratory hours inside the premises of the institution. Ethical committee approval was not found to be essential. The study commenced with the approval of the Dental Education Unit of the University and the Head of the Department of Prosthodontics after obtaining consent from all of the students. The students who gave a written consent were included in the study and there was no specific exclusion criterion for the study as it was part of the pre-clinical curriculum followed by all the students in their first year.

Group A, B and C were exposed to three different teaching methodologies and were instructed to complete three teeth arrangements, the order of the teaching methodology for each of the three arrangements are depicted in [Table/Fig-1]. Each study participant fabricated three sets of articulated edentulous maxillary and mandibular occlusal rims approved by a single instructor to ensure uniformity. The instructor who has completed his Masters in Prosthodontics, with an academic experience of seven years in handling clinical and pre-clinical work, and a qualified examiner for final pre-clinical examinations conducted the study. He objectively evaluated the three teeth arrangements of each participant using a scoring system with points. The points for the scoring system were formulated by assigning points for each step in the exercise that are vital in completion of the teeth arrangement [Table/Fig-2].

The study was carried out in the allotted pre-clinical laboratory hours for the first year students in the dental curriculum. Four laboratory classes each three hours in duration were utilized for completing one teeth arrangement for the respective teaching methodology. A duration of three laboratory classes were given in-between each change in teaching order for the students to prepare the articulated models for the next teeth arrangement.

Group A students were exposed to a live demonstration of teeth arrangement. Group B students were exposed to group discussion and the students were provided with hand-outs, to be followed during teeth arrangement with diagrams. Group C students were exposed to classroom lecture where the individual position of different teeth was illustrated using pictures projected from different angulations on a power point presentation. All three groups had a single instructor to avoid bias. Once the three groups completed their respective classes, they were asked to proceed with one teeth arrangement each. In the process of teeth arrangement students had access to the material used for their respective teaching. Group A was given access to a completed teeth arrangement on which demonstration was given and a recorded video of the demonstration was made available on a projected screen for reference, Group B was given access to the hand-outs of teeth arrangement principles [10], Group C had access to power point presentation with photographs. The videos used for the study purposes were recordings that were made when the instructor was giving the live demonstration. The pictures used in the study for teaching were made ready by the instructor following standard textbooks prior to commencement of the study. The hand-outs used in the study were taken from the standard textbooks used by the students. No online pictures or videos were used in the study. The students were not allowed to carry their articulators home, discuss or access teaching material with another group. The materials such as hand-outs and videos that were used for teaching were taken back from the students once the teeth arrangements were completed and submitted. The teaching methodology was changed in each group for the second and third teeth arrangement, at the end of the third teeth arrangement, each student was exposed to three different teaching methodology, the difference between the order of teaching pattern they were exposed to, is explained in the [Table/Fig-1].

The mean, standard deviation and median scores were computed for each arrangement among the groups. Inter-group comparisons were performed using Kruskal-Wallis rank sum test and this was followed by inter-group comparisons using the Dunn’s test. R statistical software version 3.2.3 was used and for the intra-group comparisons, the “PMCMR” package for R was used.

The scores for all three groups at the end of three teeth arrangements were tabulated and average scores for each group were calculated [Table/Fig-3,4 and 5]. The scores were tabulated only for the students who completed their teeth arrangement in the scheduled time. Students who were irregular for the class or were unable to complete all the three teeth arrangement in the stipulated period due to absence for their own reasons were removed during statistical analysis. Six candidates were excluded from the study, Group A had two drop-outs due to incomplete work, Group B and Group C each had one drop-out due to incomplete work and one due to personal reasons. The mean, median and standard deviation for all the three groups and their corresponding scores were calculated and were statistically analysed. It can be observed that there is difference in mean scores among the groups for all the three arrangements. On statistical analysis using Kruskal Wallis rank sum test there was significant difference among the groups at the end of the 1^st teeth arrangement (p=0.0045) and the 3^rd teeth arrangement (p=0.0059) [Table/Fig-6]. There were no statistically significant results observed among the groups in the second teeth arrangement (p=0.4193). It was observed that mean, median scores were higher in Group A when compared to Group B and Group B had better scores compared to Group C. The Dunn’s test for inter-group comparisons between Group A and Group C was statistically significant in first arrangement (p=0.0031) and third arrangement (p=0.0057) [Table/Fig-7]. At the end of the third teeth arrangement on comparison of scores Group A>Group B >Group C. The order of teaching followed for Group A revealed better retention and reproducibility of the skill followed by Group B, which revealed that the teaching pattern taught in first teeth arrangement influenced the students’ performance in the subsequent arrangements.

Development of a skill involves the concept of learning, by which a learner improves performance through practice until the correct performance of the motor skill becomes automatic [11]. It is essential for the student to conceive the knowledge during their early learning stages especially at the pre-clinical years. Pre-clinical curriculum in complete denture removable prosthodontics involves teaching and learning of fundamental laboratory and clinical steps [1]. It involves fabrication of a completely edentulous model over which a trial denture base with occlusal rims to be fabricated. Teeth arrangement would be done on this mock model simulating patient’s jaw to perform better on clinical procedures. The students are expected to perform this skill in stipulated period of time following standard teeth arrangement principles [10], which is evaluated at the end of their pre-clinical curriculum. Teaching any procedure to a first year undergraduate student with no clinical exposure will only make them an observer [12], which in turn reflects in learning, grasping, retaining and reproducing the skill; hence, it requires sequential emphasis of these procedures and subsequent evaluation of the skill.

Learning in small groups enables the students to observe the procedure and learn with more clarity and interaction. It provides an opportunity for each student to participate, and interact with the operator [13], also charges the student with the responsibility for learning and checking themselves through self and peer evaluation [1]. However, demonstrations to small group of students are time consuming but they increase the perception of confidence in dental students [7,14]. This study involved three small groups, who were exposed to different teaching methodologies in different orders as depicted in [Table/Fig-1]. The order of teaching showed difference in performance among the groups and Group A students who were initially exposed to live demonstrations performed better at the end of first and third teeth arrangement exercise.

Lectures, seminars, reading assignments and laboratory experiences are instructional methods used to teach new concepts to dental students but they fall short in teaching the technical aspects of clinical procedures [13]. Lectures are usually monotonous and they fail to impart a skill, they give only an outline of a procedure. Group C students, who were exposed to lectures in their first teeth arrangement had obtained lesser scores when compared to other groups. Lectures can help students to acquire knowledge about basic principles of arrangement but the position, placement and the errors cannot be judged. Group B students who were exposed to group discussion with hand-outs performed better than Group C but had obtained lesser scores when compared to Group A. Hence, these methods are considered to be passive with respect to students’ participation in the learning process and have questionable learning outcomes [1]. Statistically significant results were obtained between Group A and Group C at the end of first teeth arrangement (p=0.0031).

Demonstrations on an articulated model by an instructor focus on the skill to be learnt. Such live demonstrations was found superior to other forms of teaching, leading to increased student confidence, communication skills and greater understanding of procedures [13,14]. Study done by Bazyk et al., showed that their students expressed a preference for live demonstrations as they allowed them the opportunity to ask questions, interact with the instructor, understand difficulties and errors during the progress of the procedure [15]. Group A students were exposed to live demonstration and were allowed to view the video recording, which enhanced their learning and retaining the skill. This improved sensitisation of the learned skill through video-assisted instruction, overcomes shortfalls, enables better visualizations of practical techniques during small group teaching [7,13,16–18]. A procedural video that is well designed and developed can be equally effective as a live demonstration. In addition, they have an advantage as the students can review the video any time when compared to live demonstration where everyone crowds around the instructor [5].

Video assisted teaching is also a cost-effective way of conveying new knowledge, especially when there is a shortage in academic staff as they require less time than conventional teaching methods [19,20]. Updating electronic content is easier than printed material where the learners can tailor their experience to meet personal learning objectives [21]. Videos that explain the procedural steps can be accepted as a good teaching tool that will allow better visualization of the steps on a larger screen and act as an audio and video stimulation for the students [5,22]. Comparative research has also shown that video-based instructions are superior to traditional lectures [13,17,23] but unlike a teacher who actually taught and perhaps, offered explanation, the students cannot depend on a computer to elaborate on specific points, which showed none of these methods replaces live demonstrations and students’ active participation [24]. Studies done by Devitt et al., and Holt et al., also showed that instructional multimedia could only be used as a complementary method of teaching [25,26].

No other form of teaching is beneficial to beginners or slow learners in pre-clinical years. Hence, a blended curriculum approach is needed to allow flexibility, easy access for updating information, face-to-face interaction, decrease the repetition and lessening the demand for faculty supervision in an increased class size [9]. It also encourages the students to learn and has positive effect on students motor performance [27,28]. In this study, the three teaching patterns were imparted to all the groups in different order. Difference in scores were observed among groups for the three teeth arrangements which revealed that in a blended teaching curriculum the order of teaching would show a significant difference in students’ learning ability. Pre-clinical curriculum and student’s performance are crucial in deciding their skill before they diagnose and treat patients in the dental clinics. The knowledge they acquire must be rightly perceived through a proper teaching methodology, which enables them to correlate and apply it with clinical reasoning. Teaching methodologies for beginners have a direct impact on the quality of treatment rendered to patients. Retention of acquired knowledge is influenced by the order of teaching methodology, visual teaching patterns showed a higher retention than lectures and group discussions [29,30]. Hence, this study was conducted with a motive to improve the present curriculum and to achieve an ideal order of teaching to help students in acquiring a concrete and sustained knowledge.

The limitations of the study were that, a single instructor was appointed for all the teaching methodologies and the operator fatigue could have affected the outcome of the study. The knowledge acquired by the students from a single instructor would be limited. Additional instructors and evaluators in groups could have been added to conduct the study for first year students consecutively to minimize bias.

The results of the present study implies the need for a teaching methodology that helps the first time learners to observe, learn, practice and reproduce the acquired skill in a pre-clinical laboratory. The order of teaching in a pre-clinical curriculum greatly influences the knowledge acquired by the student and this concrete knowledge is essential for each student to perform in clinical situations. Live demonstrations with video assisted teaching followed by other methods have shown better results which suggest that each pre-clinical practice should begin with a live demonstration to increase the immediate learning absorption followed by lectures with power point presentation and group discussion for retention of knowledge and memory retrieval. A multi-centre study in different dental schools with instructors who follow the similar pre-clinical curriculum will help to validate these results.