Psychomotor Skills in Root Canal Treatment: Influence of Preclinical Training Time on Clinical Performance and Confidence Level of Undergraduate Dental Students


 Background: Performing root canal treatment is complex and requires the development of psychomotor skills adapted to working without the advantage of vision. Students have allocated special importance to preclinical training in helping them acquire these skills. The aim of this prospective study was to investigate the influence of exposure to additional preclinical training on undergraduate students’ confidence level and clinical performance defined by technical quality and quantity of root canal treatment. Methods: Clinical root canal treatment performed by a cohort of fifth-year undergraduate dental students was followed after half of them attended an additional (elective) endodontic preclinical course the year before. Root canal treatment was radiographically evaluated according to root canal filling length, density and presence of procedural errors. Technical quality and quantity of root canal treatment performed by students who had attended the elective course (attendees) and non-attendees, were compared. All students were also invited to participate in a survey to rate their undergraduate endodontic training and confidence levels performing root canal treatment. Statistical analysis of data was performed using Person chi-square test, Fisher Freeman Halton exact test, and T-test. A p-value <0.05 was considered statistically significant. Results: No significant difference between the two groups in overall root canal treatment quality (p=0.619) was found. Although elective attendees performed significantly less procedural errors (p=0.004), non-attendees completed more root canal treatments (p=0.012). Despite, no significant difference in the reported level of confidence between the attendees and the non-attendees, significantly more elective attendees rated their undergraduate endodontic training as adequate (p=0.002).Conclusion: While there was no significant difference in overall technical quality of root canal treatment, nor confidence levels, between both groups, undergraduate students who attended additional preclinical training performed significantly fewer procedural errors. Furthermore, students who attended additional preclinical training were more satisfied with their undergraduate endodontic education.


Background
The dental pulp -a richly neuro vascularized connective tissue located in a complex canal system enclosed within the hard tissues of the tooth crown and root [1]-is subject to painful infection due to dental caries or trauma [2]. This cascades into the periapical tissues, resulting in periapical disease with possible systemic disease associations [3].
Success of treating of pulpal and periapical disease depends on performing non-surgical root canal (endodontic) treatment which aims to remove the entire infected tissue from the root canal system, shaping then sealing it with a three-dimensional lling, that promotes healing of the periapical tissue [4].
Performing root canal treatment is complex and requires the development of cognitive-perceptual ability integrated with ne motor skills otherwise known as psychomotor skills [5], especially since much of the procedure is performed deep within narrow root canals without the advantage of vision.
The desired outcome of an undergraduate dental curriculum is for graduating students to achieve clinical competence in performing root canal treatment of uncomplicated anterior and posterior teeth [6]. More than any other subject, teaching endodontics has challenged those involved in delivering the required knowledge and skills [7]. Most students view this discipline as complex and di cult to master, which in turn re ects on how con dent they feel when it comes to performing endodontic treatment, especially on molar teeth [8]. This has been echoed by a high frequency of inadequate root canal llings and procedural errors [9][10][11][12].
Students have allocated special importance to preclinical training in helping them acquire the necessary skills [8]. Limited preclinical and clinical training time were cited as major roadblocks to attaining competency and achieving self-con dence in performing root canal treatment [7,8,13,14]. Despite the expert guidelines specifying the scope of endodontic education [15], preclinical and clinical teaching methodologies on endodontic education, the minimum number of cases required to achieve competency remain vague [8,16]. Little is known about the in uence of preclinical training time on improving clinical performance of complex psychomotor tasks as that required in root canal treatment. In addition to how this would re ect on students' con dence level.
The undergraduate curriculum at College of Dentistry, Princess Nourah Bint Abdulrahman University (PNU), Kingdom of Saudi Arabia which offered an extra elective endodontic preclinical course provided a unique opportunity to investigate the in uence of exposure to additional preclinical training time on clinical performance, by comparing the technical quality and quantity of root canal treatment performed clinically by fth-year undergraduate students, who attended and who did not attend the elective course. Their con dence level in performing root canal treatment was also compared. The alternative hypothesis was that students exposed to additional preclinical training would demonstrate higher con dence levels and improved clinical performance.

Methods
This prospective cohort study involved all registered fth-year ( nal) undergraduate students (n=46) at PNU, College of Dentistry, during the academic year 2019-2020. Half of these student (n=23) attended an elective endodontic preclinical course during the previous year. The study was exempt from ethical approval by the institutional review board at PNU (IRB#19-0165).
The undergraduate dental curriculum at PNU, College of Dentistry is a ve-year program, composed of a mixture of the block (modules) and stream (longitudinal) courses. Undergraduate endodontic teaching starts with a preclinical block course in the third year composed of a theoretical component and hands-on preclinical sessions that run for seven weeks, culminating in a total of ninety contact hours. All preclinical training takes place in a simulated setting, on mannequin heads, on which students are expected to complete root canal treatment for plastic and natural anterior and posterior teeth. Upon passing this preclinical course, students can commence performing non-surgical root canal treatment on patients under close supervision as part of stream comprehensive clinical courses.
An elective advanced preclinical endodontic block course is also offered in the fourth year. This course runs for ve weeks (a total of forty-ve contact hours) and offers advanced theoretical knowledge along with simulated preclinical training sessions focused on molar teeth.

Case selection
All completed non-surgical root canal treatment cases performed by the fth-year students during the academic year were evaluated. Students performed root canal treatment at the college of dentistry's dental clinics under the supervision of endodontic specialists, with an average student to staff ratio of 1:7. An aseptic technique with rubber dam isolation was applied in all cases. Working length was established using electronic apex locator and periapical radiographs. Canal cleaning and shaping was done either using manual 0.02mm taper stainless-steel k-les (Medin, A.S. Czech Republic) with step-back technique or rotary instrumentation using nickel-titanium Protaper Universal les (Dentsply Maillefer, Ballaigues, Switzerland). Canals were irrigated with Sodium hypochlorite 2.25% for chemical disinfection, dried with paper points then lled with guttapercha cones and AH plus sealer (Dentsply-Sirona, United States) using a lateral condensation technique. On completion, coronal restoration was performed, and a postoperative periapical radiograph was exposed using the paralleling technique.
The academic dental software system, AxiUm (Exan, BC, Canada) -employed at the dental clinics -was used to specify all nonsurgical root canal treatment cases completed by fth-year students from the start of the academic year on the rst of September 2019 until work at the dental clinics was abruptly terminated on the eighth of March 2020 due to the COVID 19 pandemic. Retreatment cases were excluded. During evaluation, records with poor quality or missing periapical radiographs were also excluded.
The cases were divided into two groups: Group 1; (attendees), teeth treated by students who had attended both the preclinical endodontic block course in the third-year and the elective preclinical course in the fourth-year. Group 2; (non-attendees), teeth treated by students who had not attended the elective preclinical course.

Assessment of clinical performance
Root canal treatment quality and procedural errors Clinical performance of the students was assessed by evaluating the technical quality of the performed root canal treatment and the presence of procedural errors. Technical quality was determined based on criteria for adequate root canal lling: distance between the end of the root canal lling and the radiographic apex, lling density and the detection of procedural errors, which had been adopted by Barriesh-Nusaair et al. [10] and Balto et al. [9]. and are summarized in Table 1 and Table 2.
The tooth was considered as one unit, scored according to the presence of errors, and/or defects in obturation length and density in any of its canals, for clinical failure of one root will eventually lead to failure of the tooth [9]. End of root canal lling is either at or ≤ 2mm from radiographic apex.
Inadequate Root canal lling is either short more than 2mm from the radiographic apex or extends beyond radiographic apex.

Density of root canal lling
Adequate No voids visible within the root canal lling or between the lling and the canal walls.
Inadequate Voids are visible within the root canal lling or between the lling and the canal walls.

Presence of procedural errors Present
One or more procedural errors are detected.

Non present
No procedural errors detected. Table 2: Criteria for detection of procedural errors.

Procedural Error Criteria of Diagnosis
Ledge formation The obturation was at least 1 mm shorter than the working length and deviated from the original canal shape in teeth where root canal curvature occurred.

Apical transportation
In the apical third, the obturation was located on the outside curve of the canal.

Apical perforation
The apical termination of the lled canal was different from the original canal terminus or when the obturation extruded through the apical foramen.

Root perforation
Extrusion of canal obturation in any other area of a root except the furcation area and the inner wall of the root Strip perforation Extrusion of canal obturation in the lateral (inner) wall of the root canal

Presence of fractured instrument
A fractured instrument was detected inside a root canal or with its tip extending into the periapical area

Furcation perforation
Extrusion of lling material through the furcation area in multi-rooted teeth Number of cases performed by each student was also recorded. Two endodontists with a minimum experience of three years, blinded to the treating students, evaluated independently, the technical quality of canal obturations, and presence of procedural errors by studying the preoperative, working length, and postoperative radiographs. Mesial and distal angulated radiographs were included for multi-rooted teeth. The periapical radiographic images were retrieved from the digital archives, viewed, and analyzed using Mipax (Microtek, Taiwan). All radiographs were examined at 1.5 magni cation on the same 21-inch LCD monitor resolution (1920 × 1200 at 60 Hz) in a darkened room, and the same ambient conditions were sustained during all the radiographic evaluation. Each original digital image was manipulated by the investigator to enhance the contrast and brightness of the image to give the subjectively clearest image of the root canal and radiographic apex as recommended by Akdeniz and Sogǔon [17].
Prior to the actual study, intra-and inter-examiner reliability was determined by evaluating eighteen endodontically treated teeth randomly selected from AxiUm records, these were not included in the study. These cases were evaluated twice by the same examiners, four weeks apart. Inter-and intra-examiner agreement were measured by Cohen's kappa (k). Values for interexaminer agreement for obturation length, density, and procedural errors were k=0.702, k=0.667, and k=0.824 respectively, while intra-examiner reliability ranged from (k=0.77 -k=1). This indicated good to excellent agreement [18]. Therefore, as reported by previous studies [19][20][21], it seemed acceptable to randomly allocate the sample radiographs equally between both endodontists.
Undergraduate students' con dence survey All students completing the ve-year dental program in 2019-2020 were invited to participate in an online questionnaire survey at the beginning of their internship year in July 2020. Prior to completing the questionnaire, the students were made aware of the objectives of the survey and how the results will be used. They were informed that participation is voluntary, their answers will remain entirely anonymous, and they can withdraw at any time during or after completing the questionnaire.
The questionnaire adapted from Davey et al. [14], and Murray and Chandler [22] contained thirteen multiple-choice format questions and three open-ended questions. The questionnaire indicated students' attendance of the endodontic elective course, assessed their experiences, perceived competence performing root canal treatments, along with their self-rated levels of the con dence in carrying out various endodontic tasks and their views on their undergraduate endodontic training.
Participants were asked to classify their perceived level of con dence over a ve-point scale: very con dent, con dent, neutral, low con dence, or extremely low con dence.

Statistical analysis
Statistical analysis was performed using the Statistical Package for Social Sciences software (SPSS version 27.0 IBM Inc., Chicago; IL, USA), Descriptive data analysis was carried out and Person chi-square test, Fisher Freeman Halton exact test were conducted to analyze the categorical data: root canal lling quality, con dence level and satisfaction. Independent samples Ttest was used to compare the number of teeth completed students in each group. A p-value <0.05 was considered statistically signi cant.

Assessment of endodontic technical quality and procedural errors
One hundred and ninety teeth were evaluated through the AxiUm software system. Thirty-one teeth were excluded either due to missing or unclear radiographs, or records revealing that the treatment was incomplete. Of the remaining one hundred and ftynine treated teeth, the majority (95.6%) were posterior teeth: molars (n=69) and premolars (n=83). Root canal llings were regarded as adequate in 60.38% (n=96) of these cases. Procedural errors were recorded in only thirty teeth (18.8%), of which apical perforation and instrument separation were the most frequent: 50% and 26.6%, respectively.
On assessing root canal treatment quality, 63.5% (n=40) of the teeth were treated by elective course attendees, and 58.33% (n=56) of non-attendee cases were regarded as adequate quality. Table 3 shows distribution of root canal treatment quality according to tooth type among students in both groups. Although signi cantly more teeth treated by attendees were of adequate lling length (p=0.015) and lacked procedural errors (p=0.004). There was no signi cant difference between the two groups in overall quality (p=0.619). The mean number of teeth treated by students who had attended the elective course (2.74) was signi cantly lower than that of non-attendees (4.17); (p=0.012). Undergraduate students' con dence survey The questionnaire response rate was very high 97.8%. All students who had attended the elective course participated. When asked about their reason for attending the course, twelve students (52.1%) stated the desire to improve their hand skills and performance, while the remaining eleven students (47.9%) were motivated by their interest in endodontics.
In regards to students' con dence level in performing different stages of root canal treatment, there was no signi cant difference in the level of con dence between the attendees and the non-attendees (Table 4). Although more students who attended the elective course perceived themselves competent in treating multi-rooted teeth (Table 5), this was not statistically signi cant (p=0.069). Attending the elective course was also not associated with a signi cant increase in the perception of competence in treating single-rooted teeth (p=1.00). However, the number of treated premolars was signi cantly associated with a perception of competence in treating multi-rooted teeth (p= 0.043). Table 4: Self-evaluated level of con dence in performing different stages of root canal treatment among elective course attendees (A) and non-attendees (NA).
Perceived level of con dence Very con dent Con dent Neutral Little con dence  On asking students about their perceived quality of undergraduate education, elective course attendees were more likely to describe all aspects of their undergraduate endodontic training as adequate (Table 6). This proved signi cant concerning the overall undergraduate training and theory content (p=0.002), (p=0.006) respectively. Another element associated with having an adequate opinion of undergraduate endodontic training was the student's perception of being competent in performing endodontic treatment on both single and multi-rooted teeth (p= 0.021) (p=0.038). In regards to the open-ended questions targeting student opinion and feedback on their undergraduate endodontic training: only nineteen students (42%) completed these questions. Students clearly expressed the desire to increase clinical and preclinical endodontic training hours, with a special focus on the use of rotary instrumentation and managing endodontic procedural errors.

Discussion
The issue of time in education is a matter of concern as it incurs greater costs and effort [23]. The undergraduate students in this study were supervised and taught by the same instructors, in relatively equal clinical training conditions [24,25] only half of them had undergone the extended preclinical training. This permitted investigating the effect of extending preclinical training time on undergraduate students' con dence levels and clinical performance of root canal treatment [24,25]. Previous studies have examined the effect of certain modi cations in preclinical endodontic teaching; for example, training on arti cial instead of natural teeth and using the electronic apex locator, by evaluating the technical quality of root canal treatment performed by the undergraduate students in a similar manner [19,26].
The present ndings showed no signi cant difference between the teeth performed by students who had attended the elective course and those who had not, as far as the overall technical quality of root canal treatment is concerned. At rst glance this suggests that preclinical training time did not in uence the undergraduate students' clinical performance of root canal treatment. This can be explained by what Chambers et al. [27] described as the "learning curve" relationship between practice and competence, where a certain point is reached beyond which extra practice no longer lends to the acquisition of skill. A study also looking into the acquisition of medical clinical skills through practice concluded that while the amount of practice time played a role in achieving an "initial mastery" of basic skills, progress beyond that was not achieved through repetition, but by performing tasks that speci cally target the areas of performance de ciency [28].
However, students who did not attend the elective preclinical course performed signi cantly more procedural errors than those who attended. In fact, cases with procedural errors (instrument fracture, ledging, perforation) that required either referral to an endodontic specialist or board residents to complete the treatment or tooth extraction due to non-restorability were by nonattendee students. Overall, the frequency of procedural errors (18.8%) was fairly low which is in accordance with other studies [20,21,29,30] .
Adequate root canal treatment was seen in 60.3% of the cases performed by the undergraduate students, in spite of the fact that the majority of the treated teeth were posterior teeth (premolars and molars) which are usually associated with lower frequencies of adequate treatment when performed by undergraduate dental students (49.5% in premolars and 26.3% in molars) [31]. An explanation may have been that the students were constantly supervised by endodontists with a low student to instructor ratio [16,21]. Another explanation may be the exclusion of root canal lling taper as an evaluation criterion of root canal lling quality in this study [25,32]. Studies considering taper had reported lower frequencies of adequate root canal treatment [9,10,30]. Taper is a subjective matter that cannot be adequately re ected in a two-dimensional radiograph, moreover, it may be in uenced by the canal's original anatomy giving the impression of a large taper irrespective of actual instrumentation [33]. Accordingly, it was excluded as an evaluation criterion in this study [25,32].
The mean number of teeth completed by non-attendees was signi cantly higher compared to attendees. One possible explanation is that non-attendees sought out more opportunities to practice through clinical experience. Other factors that could lend an explanation to this result is the fact that the academic year was cut short due to the COVID-19 pandemic, and that retreatment cases performed by the students were not accounted for in the study [34].
Although more attendees 78.3% perceived themselves competent in treating multi-rooted teeth compared to non-attendees 45.4%, survey results showed no signi cant difference between the two groups in con dence levels whether in performing a particular stage of endodontic treatment or in their self-perception of competence in treating single or multi-rooted teeth. These ndings are in line with other studies exploring what was termed self-e cacy -a combination of competence and con denceof students [32,34], which found no difference between students who attended different theoretical and clinical modules. Con dence levels in this study were also in close proximity to those reported by similar studies despite the di culty in drawing conclusions from other studies due to variations in methodologies [14,22,35,36].
The difference between attendees and non-attendees lay in their satisfaction with the quality of their endodontic undergraduate education. When asked about their perception of the overall training quality of endodontic education, 87% (n = 20) of elective course attendees reported adequate training, in contrast to only 45.4% (n = 10) of non-attendees.
Students attribute great importance to preclinical training in helping them acquire the necessary skills in root canal treatment [8], which would explain this signi cant difference in the level of satisfaction. Sukotjo et al. [37] found that shortening preclinical hours in the undergraduate dental curriculum affected student anxiety and stress levels especially those measured prior to entering the clinics. The replies to the open-ended questions at the end of the questionnaire echoed this desire for more training time (clinical and preclinical), similar to what has been reported by previous studies when sounding out student perspectives on their undergraduate education [7,8].
A recent study by Baaij et al. [32] concluded that undergraduate students' feelings of competence and con dence were in uenced by clinical experiences in endodontics, speci cally, successful ones. In accordance with this, the ndings of the present study show that students' self-perception of competence was associated with the number of teeth they reportedly treated, in particular: premolars. A reason for that maybe that students were required to pass an endodontic competency assessment, which involved completing root canal treatment on a two-canal upper premolar.
Certain limitations to this study should be kept in mind: a relatively small sample size. Students from only a single academic year were included, as the elective course was unavailable to students from the previous year, and the elective course became mandatory for subsequent fourth-year students. The attendees' reasons for taking the course were mainly either a desire to increase skill or having an interest in endodontics. However, the reason why non-attendees did not choose to take the elective course was not explored. This could have shed more light on speci c characteristics of that group.
Students' innate cognitive, perceptual and psychomotor abilities related to acquiring competence in psychomotor skills were also not investigated [38]. Studies have shown that these abilities may play a role during the initial stages of skill acquisition and their in uence tends to diminish with increased training [38]. However, innate spatial abilities remained of in uence regardless of practice, for tasks of an important spatial nature, which could very well apply to procedures in root canal treatment [39].
Case di culty which has a major part to play in undergraduate root canal treatment performance [29], was not taken into consideration in this study. It was assumed that endodontists supervising the students assess the case and refer moderate to high di culty cases to post-graduate students or endodontic specialists within the Dental College's clinics.
Although the overall technical quality of root canal treatment performed by undergraduate students and their con dence levels were not affected by their preclinical training time. Students who attended the elective course performed signi cantly fewer procedural errors and were more satis ed with their undergraduate endodontic education.
In spite of students' perspective regarding lack of training time, more focus should be placed on how preclinical endodontics is taught, how to facilitate deliberate practice and not how much, i.e., the quality not the quantity [37]. Further research is required on pinpointing the challenges of acquiring of psychomotor skills required in root canal treatment and introducing novel teaching strategies targeting these unique skills.

Conclusion
Within the limitations of this study, no signi cant difference was found in overall quality of clinical root canal treatment performed by undergraduate students who attended extended preclinical training compared to those who did not, nor were their con dence levels affected. However, students who attended additional preclinical training performed signi cantly fewer procedural errors and were more satis ed with their undergraduate endodontic education.