| Abstract|| |
Objective: To assess dental students' knowledge of dental radiation protection and practice as well as correlating their knowledge to practice on dental radiography.
Materials and Methods: A cross-sectional questionnaire based study on radiation protection among dental students. Correct responses to the questions were allocated 1 mark while wrong response received no mark. Statistical analysis was performed using SPSS version 17 (Chicago, IL.). Pearson's coefficient correlation analysis was performed to establish relationship between various variables with the significant level set at 5%.
Results: The study was conducted among 78 final year dental students, of which 32 were females and 46 were males. The mean score of the students on knowledge of radiobiology was 1.85 ± 1.19. Knowledge of radiation protection was abysmally poor with mean score of 0.92 ± 0.80 while the mean score of radiation protection practice was 2.69 ± 1.42. There was no significant correlation between the number of radiographs taken and knowledge of radiation protection or practice. A greater proportion of students with ''good'' radiation protection knowledge in comparison to those with ''poor'' knowledge kept a distance of over 3 metres from the patients/X-ray tube, wore lead apron, used the lowest possible settings on the X-ray machine and used collimators. Most (75.6%) of the students thought they did not have adequate knowledge on radiation protection.
Conclusion: There is need to expand the curriculum to provide better exposure to radiation protection and its practice, so that these students on graduation will be well grounded with the principle governing dental radiography.
Keywords: Assessment, dental students, knowledge, radiation protection, radiation practice
|How to cite this article:|
Enabulele JE, Igbinedion B O. An assessment of Dental Students' knowledge of radiation protection and practice. J Educ Ethics Dent 2013;3:54-9
|How to cite this URL:|
Enabulele JE, Igbinedion B O. An assessment of Dental Students' knowledge of radiation protection and practice. J Educ Ethics Dent [serial online] 2013 [cited 2019 Jul 17];3:54-9. Available from: http://www.jeed.in/text.asp?2013/3/2/54/136044
| Introduction|| |
Dental radiographs are important tools in the diagnosis of oral diseases. It helps the dentist to employ appropriate treatment regimen for patients' dental conditions, and plays a continual important role in dental practice. Hence its availability in most dental clinics is considered crucial. Radiation dosage from such dental radiographs are low and are thought to present minimal risk.  It is estimated that about 480 million dental radiographs are performed annually accounting for approximately 15% of all diagnostic X-ray examinations.  Consequently concern over such frequent low level exposure to ionizing radiation is arising.  These concerns borders around the observations that dental radiographs are performed frequently (including on children who have more radio-sensitive tissues), utilization of old X-ray machines, development of cone beam computed tomography and poor knowledge of radiation amongst dentists and other health workers that take dental radiographs.
Dentists take radiographs in the evaluation of their patients. During undergraduate and post graduate training dentists are trained to perform dental radiographic exposures particularly during clinical rotations. In Nigeria students are allowed to take dental radiographs under supervision. The undergraduate dental training in Nigeria is divided into the pre-clinical levels (1 st , 2 nd , and 3 rd year) of study and the clinical levels (4 th , 5 th and 6 th year) of study. In the institution where this study was carried out the fifth and sixth year curriculum of dental students includes two schedules each of lectures in dental radiology with the second schedule of the fifth and 6 th year having basic radiation physics, the production of X-rays, radiation biology and protection and radiology of oral diseases among other topics.  These students are also exposed to clinical postings in the oral diagnosis and radiology clinic for a period of 4 weeks in the 5 th year and 8 weeks in the 6 th year. On completion of the course, the undergraduate student is expected to be able to explain the production of ionizing radiation, image formation and principles of radiation biology and protection from effects of ionizing radiation to oneself, clinical staff and patients.  Eventually these dental students would metamorphose to dentists and may perform dental radiography in their clinics. Their knowledge and practice on dental radiography are consequently crucial.
Exposure to dental radiation should be minimized where practicable.  Consequently, the ALARA (As Low As Reasonably Achievable) principle was adopted to minimize radiation dose. In general, ALARA principle take into consideration the justification for the radiological study and taking the imaging examination with the least amount of radiation that can produce radiographs of reasonable diagnostic quality. As a result radiographs should only be taken at the minimum dosage with reasonable information yield in as much as a safer method is not available. , The benefits from such radiographic exposures should outweigh the potential risk. Consequently operators of radiographic equipment should be thoroughly familiar with radiation safety practices and radiation regulations to protect themselves, their colleagues and the patients.
X-rays are harmful to humans and can cause genetic damage, leukemia and oncogenesis. We are all exposed to daily radiation from natural and artificial sources with man-made source accounting for about 18% of such radiation doses.  Exposure to medical ionizing radiation is estimated to cause about 100-250 deaths in the United Kingdom annually.  Studies have shown that there is poor knowledge among dental students,  medical students,  dentists,  medical doctors, , radiographers  and other health workers. , The radiation protection knowledge and practice of dental radiography by dentists is consequently crucial. Unfortunately proper radiation protection practice by dentists is inadequate.  This observation may reflect their poor knowledge of radiation protection. As such, we undertook this study to assess dental students' knowledge of dental radiation protection and practice as well as correlating their knowledge to practice on dental radiography. To the best of our knowledge similar studies had not been done.
| Materials and Methods|| |
This is a cross-sectional study on radiation protection conducted at the School of Dentistry of the University of Benin. A four section questionnaire was administered to volunteering final year dental students at the University of Benin. The questionnaires were collected after being filled by the students within the hour of administration with all the students seated and interaction between students discouraged. Correct responses were allocated 1 mark while wrong response receives no mark. No point was subtracted for wrong responses. There was no student identifier in the questionnaires.
The first section consists of socio-demographic data and questions bordering on if the students had previous exposure to formal lectures on radiation protection and pre-medical school graduate certificate. The second section consists of questions on radiobiology while the third section was on radiation protection. The fourth section was meant to test good radiation protection practice and also contains other questions such as if the students feels that their knowledge on radiation protection was adequate and the kVp of the machine they use.
Each of the second, third and fourth sections have five questions each for assessing that section. Radiobiology, radiation protection and practice scores were categorized into; 0 to 2 points (poor), 3 points and above (good).The correct responses of radiobiology (section 2) and radiation protection (section 3) were summated to yield ''total knowledge on radiation protection'' which was subsequently graded into ''poor'' (0 to 4 points) and ''good'' (5 to 10 points). Statistical analysis was performed using SPSS version 17 (Chicago, IL). Pearson's coefficient correlation analysis was performed to establish relationship between various variables with the significant level set at 5%.
| Results|| |
The study was conducted among 78 final year dental students, of which 32 were females and 46 were males. The mean score of the students on knowledge of radiobiology was 1.85 ± 1.19 (of 5 points). The proportion of students with a score of 2 points was the most, accounting for 22 (28.2%) of all the students. None of the students correctly answered all the questions on radiobiology. In comparison to the knowledge of radiobiology, knowledge of radiation protection was abysmally poor as the mean score was 0.92 ± 0.80 (of 5 points) while the modal score was zero point (accounting for 24 (30.8%) of the students). Only one student correctly ranked the effectiveness of the methods of protecting patients. Surprisingly, none of the student knew the correct annual radiation dose limit for a dentist and only 14(17.9%) of the total number of students correctly knew what each of the acronyms of ALARA stood for. Overall, the mean of the total (sum of radiobiology and radiation protection scores) score by the students was 5.45 ± 2.66 (of 10 points) and the modal score was 3 points (23.1%). No student was observed to have a score of 10. On categorizing the total knowledge of radiation protection, 12(15.4%) students had ''good'' score while 66(84.6%) students had ''poor'' score.
Although none of the students used film badge, the other indices tested showed that they had good radiation protection practice knowledge - [Table 1]. The mean score of radiation protection practice was 2.69 ± 1.42 (of 5 maximal points) and modal score of 4 points (39.7%). The proportion of students with ''good'' radiation protection practice rating was 50 (64.1%) whereas 28 (35.9%) had ''poor'' rating. Undermining that 52 (66.7%) of the students responded that they used the lowest possible settings during dental radiographic exposure on patients, only 2 (2.6%) actually knew the kVp of the machine used in the department.
The mean radiographs taken by these students monthly were 12.87 ± 8.8 with 53 (67.9%) students taking an average radiographs of 0 to 9 per month (''poor'' rating) and 25 (32.1%) took over 9 radiographs/month (''good'' rating). There was no significant correlation between the number of radiographs taken and knowledge of radiation protection or practice.
A greater proportion of students with ''good'' radiation protection knowledge in comparison to those with ''poor'' knowledge kept a distance of over 3 metres from the patients/X-ray tube [7 (58.3%) vs. 34 (51.5%)], wore lead apron [12 (100%) vs. 54 (81.8%)], used the lowest possible settings on the x-ray machine [11 (91.7%) vs. 41 (62.1%)] and used collimators [10 (83.3% vs. 40 (60.6%)] - [Table 2]. Of the preceding tested parameters of radiation protection practice, those that used the lowest possible settings was at statistical significant level, P = 0.046. Most 59 (75.6%) of the students thought they did not have adequate knowledge on radiation protection.
|Table 2: Cross-tabulations of total knowledge of radiation protection against radiation protection practise indices|
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| Discussion|| |
Radiological investigations should only be prescribed by medical personnel for specific purposes when the benefit outweighs the risk. Thus, it is imperative that the dentist ensure that adequate justification for the dental radiograph is met and that minimal permissible exposure is given. These dentists should be knowledgeable on radiation protection in order to properly protect the patients, themselves and others around them and their knowledge of ionizing radiation from medical devices makes explanation of the benefit and risk to the patients easy.
In order to assess knowledge on radiation protection it is pertinent to establish the level of awareness on radiobiology. These students had an appreciable degree of knowledge on radiobiology. Radiation causes cell damage by ionization with the consequent formation of ions that can produce free radicals, break chemical bonds, creates cross-linkage between macromolecules or damage molecules and genes. Undifferentiated rapidly proliferating cells are susceptible to radiation damage than differentiated stable cells because cells are more sensitive in the M and G2 phase and most resistant in the late S phase. Examples of such rapidly proliferating cells are found in foetuses; hence the developing foetus is particularly sensitive to the effects of radiation especially 2-9 weeks after conception which is the period of organogenesis. 
In comparison, knowledge on radiation protection was poor. Only one student knew the correct order of sequence for the effective radiation protection of patients for dental radiography. The most effective method is to reduce repeat rate, followed by the use of modern fast film, thyroid shield utilization and finally lead apron. Reducing repeat rate comes with experience, adequate training and application of standard radiation protection practices with proper departmental quality control programme. If no repeat radiograph is taken then there will be no additional undue exposure to radiation of the patients. Consequently, the exposing health professional should apply the appropriate settings and be familiar with the optimal settings to use. The use of faster film speed can also reduce radiation exposure to about 50% while maintaining the diagnostic quality. 
Poor knowledge of the meaning of ALARA was observed, as only 17.9% of the students actually knew what the acronyms meant. It can be deduced that these students who were unfamiliar with the term may not be able to apply the principle of ALARA in practice. Consequently, patients may receive unnecessary radiation dose if the ALARA principle is not put into practice. Furthermore, none of the students knew the annual radiation dose limit for dentist. The maximum permissible annual dose of ionizing radiation for health care workers is 50 millisieverts (mSv) and the maximum permissible life time dose is 10 mSv multiplied by a person's age.  Concerning peri-apical radiograph dose, only 10.3% of these students could estimate the average radiation dose during a single peri-apical exposure. The effective dose from intra-oral peri-apical radiograph is 0.005 mSv. , Gijbels et al. further determined the effective dose from peri-apical radiographs with rectangular collimation as 0.001 mSv (anterior), 0.001 mSv (lateral) and 0.003 mSv (posterior) while for round collimation the values were 0.001 mSv (anterior), 0.002 mSv (lateral) and 0.005 mSv (posterior). Hence, rectangular collimators reduce the radiation dose to patients when compared to conical collimators.
Contrary to the earlier observation that these students have poor knowledge on radiation protection, majority (67.9%) of the students correctly opted to protect the thyroid gland rather than the brain or nostril during head and neck radiography. In the head and neck region the thyroid gland is one of the most sensitive organs. Sikorski et al. documented that radiation exposure reduction by thyroid shield varied from 5% to 56% for a complete-mouth survey, 2% to 18% for a bitewing survey, and 10% to 79% for a panoramic survey. In addition, their study showed that thyroid skin exposures measured on adults were 33% to 84% lower in offices in which thyroid shield was used as compared to offices in which it was not used and thyroid skin exposures measured on children were 63% to 92% lower. As a result it is highly recommended that leaded thyroid shields should be employed in children. ,
Sixty-four percent of the student had good radiation protection practice while 367% had poor knowledge, an observation incongruous to knowledge on radiation protection assessment. None of the students had a thermolumincent dosimeter (TLD) badge despite some performing up to an average of 40 dental radiographs per month. Although 52.6% of these students kept a distance of at least 3 meters to the radiation beam, there is still some radiation dose absorbed from scatter radiation. The direct and scatter radiation dose to the patient as well as the scatter radiation to the imager are considered very low, however some studies showed evidence of increased risk of brain, salivary gland, and thyroid tumours from dental radiographic exposure. ,,,, It is therefore crucial that other means of reducing radiation dose be employed. The use of collimation further reduces patients' primary and scattered radiation. Collimators are like aperture of a camera that reduces the field of irradiation and are typically conical/circular or rectangular. Rectangular collimators are five times more effective at reducing the radiation dose compared to conical collimators. , Consequently collimators should be provided in every dental radiographic unit, especially rectangular type. In the center where this study was conducted, rectangular and circular collimators are available, but the circular type is more commonly used.
None of the students in our study had dosimeter which is likely due to the financial implication. It is the authors' opinion that students should acquire durable dosimeters which they may also use long after graduating from dental school. Education plays an important role in the use of dosimeter.  Ilguy et al. reported low usage of dosimeters among dentists with 11% of specialist utilizing dosimeters in comparison with 2.7% by non-specialists. Unfortunately, most of the students were ignorant of the maximum acceptable life-time cumulated radiation dose which dosimeter is used to calculate.
In this study, knowledge of radiation protection positively affected the students' practice of taking dental radiographs with reduced exposure to radiation. A higher proportion of students with good radiation protection knowledge use the lowest possible setting in acquiring dental radiographs which was at statistical significant level (P = 0.046). Similarly a higher proportion of these students with good knowledge of radiation protection kept a distance of more than 3 metres from the patients, wore lead aprons and used collimators (although not at statistical significant level). About 86.4% of the students wore lead apron while all those with good knowledge did wear lead apron which sharply contrast with the 8.7% that did so in the study on dentists in Turkey. 
Methods to protect the imaging health personnel include education, implementation of radiation protection program and usage of barrier shielding. The radiation protection program should also limit the life time and annual radiation exposure within the allowable threshold. Training in radiation protection should be a continuous process even after graduation from dental school because studies have shown that substantial amount of knowledge is lost by 6-12 months following course attendance, and to achieve long-term knowledge retention, early or repeated reinforcement may be necessary.  Attendance at such refresher courses is crucial as about two-third of these students were aware that their knowledge of radiation protection was inadequate.
In conclusion, the dental students in this study did have good knowledge on radiation biology but show relatively poorer knowledge on radiation protection. Despite their poor radiation protection knowledge their practice was better. We recommend that the curriculum of dental school be expanded further to provide better exposure to radiation protection and its practice, so that these students on graduation will be well grounded with the principle governing dental radiography, its justification, quality control practice and the correct practise of the ALARA concept.
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Joan E Enabulele
Department of Restorative Dentistry, University of Benin, Benin
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2]