A survey on dental undergraduates’ knowledge of oral radiology

Dentists’ incorrect behavior with regards to Oral Radiology, as reported in the literature, has been related to inadequate training of undergraduates. Aim: This study assessed dental undergraduates’ knowledge of Oral Radiology. Methods: A questionnaire containing 30 questions pertaining to three domains - General Principles, Radiobiology/Radioprotection and Technique/Interpretation - was used as data collection instrument. A total of 195 students answered the questionnaires. Results: No statistically significant differences were found between second-, third- and fourth-year students (p>0.05) when the whole questionnaire and the General Principles domain (p>0.05) were considered. The Technique/Interpretation domain presented a borderline statistical significance level (p=0.051), with more correct answers attributed to second-year students. A statistically significant difference (p<0.05) was seen for the Radiobiology/Radioprotection domain, in which the fourth-year students performed better. Conclusions: Dental undergraduates’ knowledge of Oral Radiology did not increase or decrease significantly comparing the undergraduate years. However, with the exception of the Technique/Interpretation domain, students of more advanced undergraduate years answered more correctly the questions. Nevertheless, the Technique/ Interpretation domain should be reinforced throughout the undergraduate course.


Introduction
Literature shows that many dentists have neglected not only the basic principles of radiology, but also certain national laws on radiograph application 1-6 . Inappropriate procedures mostly involve inadequate development of films, use of cone indicators, incorrect radiographic techniques, excessive exposure time, failure to protect patients during radiographic exposure, and improper disposal of processing solutions and lead foil 3 . These procedures result in radiographs of inadequate quality for diagnosis, higher radiation doses for patients and damage to the environment 3 . Some authors associate such failings with an inadequate training of undergraduates 3,[7][8] .
Currently, education of dental students is being discussed all over the world with a view to changes [9][10][11][12] . In Brazil, the Ministry of Education has proposed new Curriculum Guidelines for Dental Courses 10 . These Guidelines propose an interdisciplinary general graduation in dentistry. However, 10 years after the Guidelines were first proposed, little discussion has taken place in terms of education on Oral Radiology. As an example, this subject is taught during a 1-year period in Brazilian undergraduate dental courses, although dental radiographs are taken throughout the whole undergraduate course.
Piracicaba Dental School and other Brazilian universities are implementing new curricula based on the abovementioned Guidelines. Learning deficiencies must be assessed in order to propose methodological strategies and improve the course. With such a background, this study set out to investigate the development of Oral Radiology knowledge during an undergraduate dental course.

Material and methods
This cross-sectional study was conducted at the Piracicaba Dental School, University of Campinas, Piracicaba, SP, Brazil. Its design received full approval from the local Research Ethics Committee (protocol #095/2011) and the participants were second-, third-and fourth-year undergraduate students. First-year students did not participate because Oral Radiology is not a subject in their curriculum.
In order to evaluate the students' knowledge, a selfadministered questionnaire containing 30 questions on Oral Radiology was applied at the end of the academic year. The Chart 1 shows the questionnaire with the answers considered correct. The questions pertained to three domains: General Principles, Radiobiology/Radioprotection and Technique/ Interpretation. The questionnaire had been validated earlier according to the protocol described by Ferreira et al. 13 (2012). The students received the questionnaire after agreeing with their participation and giving their written informed consent. The questionnaire was not used for graduation purposes and the students were not obliged to fill it out.
Questions were answered with "True", "False", or "I don't know" statements. The aim of the "I don't know" statement was to prevent random responses by guessing the Chart 1: Questions of the questionnaire applied and the respective correct answers. The students were asked to answer each question as "True", "False" or "I don't know".   answers. The SPSS software version 18.0 (SPSS Inc., Chicago, IL, USA) was used for statistical analysis and the data were dichotomized into correct and incorrect answers (including the "I don't know" answers). The correct and incorrect frequencies were tested in relation to the students' year group, using the Chi-square test. These frequencies were also tested in relation to each of the three main domains of the questionnaire. Significance level was set at 5%.
Each undergraduate year group invited to participate in this study had approximately 80 students regularly enrolled in the undergraduate course, so the sample comprised a population of 240 potential respondents.

Results
The overall response rate was 81.2% (n=195) and the final sample comprised 68 second-year (34.9%), 75 thirdyear (38.5%) and 52 fourth-year students (26.7%). The sociodemographic survey ( Table 1) showed predominance of female students (74.4%) aged 20 to 23 years (67.1%), with a household income above five minimum wages (74.8%). Table 2 shows the percentage of correct and incorrect answers to the questionnaire. The chi-squared test did not show statistically significant difference between these values (p>0.05).
Analyzing the questions separately, Question 18 ("An adequate maintenance of the x-ray machine results in better productivity, and protection for both operator and patient") yielded the largest number of correct answers. On the other hand, Question 17 ("Barriers like lead walls are mandatory to ensure adequate protection for the operator") presented the largest number of incorrect answers. Question 11 ("Routine radiographic examination with a six-month interval cannot cause stochastic biological effects") was also answered incorrectly by most students.
Analyzing each questionnaire domain (Table 3), no statistically significant difference was found either for the General Principles or for the Technique/Interpretation domains (p>0.05). In the General Principles domain, fourthyear students answered more questions correctly, while the second-year students performed better in the Technique/ Interpretation domain. A statistically significant difference (p<0.05) was seen for the Radiobiology/Radioprotection domain with more correct answers attributed to the fourthyear students.

Discussion
This study set out to investigate to what extent dental undergraduates' knowledge of Oral Radiology developed throughout their course. Brazil has the largest number of Oral Radiology courses and oral radiologists 14 . The incorrect behavior of dentists in terms of Oral Radiology is reported in the literature and it is correlated to a deficiency in the undergraduate education 3,7-8 .
Various parameters are used to determine the effectiveness of education, namely student's performance, satisfaction, attitudes and skills, accomplishment of course goals and objectives, teachers' perceptions and evaluation of the course [15][16] . In this study, students' knowledge was evaluated by means of a self-applied questionnaire, a methodology also used in similar studies [17][18][19] . The questionnaire used in this research had been previously validated according to a protocol referred to in the literature 13 . The aim of this validation process was to obtain a trustworthy instrument for evaluation of the students. It included specialist's opinion in the field, pilot tests to verify students' understanding of the questions, consistency of data, and reproducibility of the questionnaire.
Undergraduates at advanced levels of a dentistry course have more study content than students at initial levels. Therefore, it is expected that the more advanced the student level, the better their knowledge of course content. In this study, fourth-year students answered more questions correctly than did either second-or third-year students. Since the questionnaire was not used to grade the students in levels, it is believed that the obtained results are close to the real situation and thereby provide a reliable evaluation of the students' knowledge. Some deficiencies were, however, detected for fourth-year students in relation to the specific domains evaluated in the study.
The General Principles domain presented uniform behavior throughout the course, with no statistically significant difference between the students (p>0.05). The evaluated students answered correctly about 61 to 65% of this domain, showing satisfactory knowledge of the fundamentals of Oral Radiology.
Undergraduates' knowledge of the Radiobiology/ Radioprotection domain increased to a significant extent (p<0.05). Since the second-year students had not studied this subject when the research was conducted, they produced more incorrect answers than other students. On the other hand, fourth-year students registered more correct answers than did third-year students. Such results strongly indicated that dental students showed a significant increase in their knowledge of radioprotection procedures and the consequences of exposure to radiation along the course. It is important to emphasize that only the Radiobiology/Radioprotection domain had not been taught to the second-year students when the questionnaire was applied.
The Technique/Interpretation domain showed a borderline statistical significance level (p=0.051). Secondyear students performed better than fourth-year students, which in turn, answered more questions correctly than did the third-year. Possibly, the second-year students answered more questions correctly because they had studied this subject just before the questionnaire was applied. Despite the decrease in the knowledge levels, as observed in the Technique/Interpretation domain, it presented the highest percentage of correct answers.
Dental radiographs are a valuable diagnostic tool for patient assessment and treatment planning in most clinical specialties of dentistry 20 . The obtained results demonstrated that third-and fourth-year students showed less knowledge of the Technique/Interpretation domain. These students are closest to entering the professional field and this lower knowledge should concern the clinical practice because a thorough knowledge of the various available radiographic modalities, their application, and accurate interpretation of the images and obtained data is necessary for the ethical and efficient practice of dentistry 20 . Question 29 ("Multilocular ameloblastoma has a ground-glass appearance") presented the highest percentage of incorrect answers in the Technique/ Interpretation domain.
Education systems worldwide are undergoing remar-kable changes, as courses and programs are being designed in new ways 19 , moving away from the passive teacher-centered to a more active learner-centered learning 21 . The Brazilian Guidelines for Dental Education 10 encourage a more active learner-centered learning. The literature has shown that this methodology presents better results in Oral Radiology 20 . Therefore, it can be suggest that an active learner-centered methodology be introduced in the evaluated school in order to improve students' knowledge of the Technique/ Interpretation domain. It is important to emphasize that this was a cross-sectional study, which evaluated only one dental school, which means that the obtained results refer to a group of students who took part in the survey and, undoubtedly, there are differences between courses. Hence, further longitudinal investigations involving other dental schools are recommended to provide more data for discussion on education in Oral Radiology. Additionally, the present study evaluated only the students' theoretical knowledge and not their practical skills.
In conclusion, dental undergraduates' knowledge of Oral Radiology did not increase or decrease significantly comparing the first-, second-and fourth-year groups. However, except for the Technique/Interpretation domain, the more advanced the undergraduate year, the more correctly the students answered the questions. Nevertheless, we believe that the Technique/Interpretation domain needs to be reinforced throughout the course.