Radiation Protection in Dentistry

Radiation protection in dentistry-do we practice what we learn?

Abstract.

Aim: Easy availability, overuse and lack of reinforcement of the radiation hazards facts have unknowingly resulted in overlooking of ALARA among many dentists . The aim of the present study was to assess the awareness, concern and practice of radiation protection in general dental practice.

Materials and methods:The study was conducted among 156 private dental practitioners in West Bengal India. A cross-sectional self-administered questionnaire consisting of a total of 28 items was employed. The obtained data was compiled systemically and was analyzed by using SPSS 17.

Results: Bisecting angle technique and use of E speed films with manual processing was the most common. Majority of the participants had no idea about the type of cone used (37.2% ), tube current (37.8%), kvp56.4% (88). Exposure time was equally variable with maximum variability in case of digital radiographs. Use of lead barriers and aprons were poor .

Conclusion :The knowledge and practice of radiation protection is not satisfactory. Repeated reinforcement and training and the most importantly change in attitude to follow ALARA is required.

key words:

Radiation, questionnaire survey, safety measures, dentists

Introduction:

X-ray is invisible but its effects are not. Radiological investigations are first modality of diagnosis in most oral and maxillofacial disorders nevertheless its detrimental effects cannot be ignored. Easy availability, overuse without proper knowledge and lack of reinforcement of the radiation hazards facts have unknowingly resulted in overlooking of ALARA principles in many cases. ^{[1, 2 ]}

The aim of the present study was to assess the awareness, concern and practice of radiation protection in general dental practice in the state of west Bengal in India.

Materials and methods:

The present study was conducted among private dental practitioners in west Bengal India. Ethical clearance was obtained from the Institutional Review Board, Haldia College of Dental Sciences, Haldia. The investigators visited 250 private dental practices in west Bengal, India but only 156 dentists were part of the study, all of those who had a radiographic machine were included in the study. The purpose of the study was explained to the dental practitioners and their consent was subsequently obtained. A cross-sectional self-administered questionnaire consisting of a total of 28 items was employed in the present study. Information pertaining to demographic data such as age, gender, educational qualification, and type and duration of practice was also collected.

The obtained data was compiled systemically and was analyzed by using SPSS (statistical package for social sciences) Chicago III software version 17. Mean was calculated for demographic variables. For all variables frequency and percentage were calculated. The significance of difference between two independent groups was determined using Chi-squared test. Level of significance was set at 0.05.

Results

Questionnaires were distributed to 250 dentists but only 156(62.4%) were considered as study subject as they possessed radiographic unit. Of 156 dentists134 were male and 22 female dentists. 75.6% (118) were university graduates (BDS) and 24.4% (38) were post graduates (MDS) involved in general practice. 34.6% (54) had < 5yrs of experience, 28.8 %( 45) 5-10yrsexperiece, 23.7 %( 37) had 11-25yrs of experience and 12.8 %(20) had > 25yrs of experience. (Fig-1)

61.5 %( 96) had either intraoral x-ray unit or extra oral unit or both. Majority of the dentists 85.3% advised for radiographs only after clinical examinations. IOPAR was a common radiograph advised (44.2 % advised at least 30-49 iopar /week) followed by opg ( 39.7% advised for at least 1opg/week. Bitewing /occlusal were not very commonly advised.

Majority of the participants had no idea about the type of cone used (37.2% i.e. 58), tube current (37.8% (59). 56.4% (88) dentists said that kvp of dental x-ray machine should be within60-80kvp and 50% used cylindrical collimation. Though about half of them kept the exposure time 0.5sec to 0.8secs about 20% used a longer exposure 1.2 secs. 62.2 % (97) of the respondents used films, mostly E speed films. Among 8.9 %( 14) who used digital sensors 50% had no idea about the type used. In case of extraoral radiography 60.3% had no idea of the type of receptor being used. 49.4%(77) preferred bisecting angle technique, only a mere 3.2% used film holders, 55%(86)used patients finger, 7.8% assistant used to hold film and remaining 34% of the dentist used to hold the film themselves. 87.3% used manual processing or both, only 3.8% automatic processing rest used digital imaging. 35.9% changed processing solutions every week. A shocking fact was noticed that 83.3% of those using manual processing threw the processing solutions in sewage drains and lead foils in dustbins.

Around 40.3 %( 63) of the responders did not stand behind any barriers during exposure. Many of the dentists were completely unaware of the position distance rule to be followed in case of lack of barrier. Only 59%of the responders knew correctly where to stand during exposure (>6ft), 10.9% had no idea while 30.1% answered it wrongly. Similarly 45.7% did not know the correct angulations to stand. 46.2% (72) of the dentists never made their patients wear lead apron 60.9% (95) did not use thyroid collar, 42.3% (66) of the dentists never wore the lead apron during exposure. More than half 51.3% (80) did not have any idea of the correct thickness of lead apron. 93.6% (146) did not have any form of dose monitoring and 45.5% (71) did not know of radiographic machine periodic calibration. Awareness of radiation protection and pregnancy was good. 51.3% (80) said x-ray should only be done in emergency, 57% (89) considered 2^nd trimester to be safest for radiographs but 16.7 %( 26) considered it can be done in any trimester.

Discussion

The respondents’ knowledge concerning the technical details of their equipment was limited, with 82.3% not being aware about the kilovoltage peak of their machine. With respect to radiation protection of the patients, a radiographic unit with a voltage capacity between 60Kvp to 70Kvp is recommended.^[3] Up to 10.8% dentists were not aware about the speed of film. 94.1% dentists preferred technique was bisecting angle technique for periapical radiography, silmilar to study by Sheikh et al.^[4]

Higher qualifications (MDS) showed a significant difference only in the type of radiographic machine (p=0.026), number of radiographs taken(p=0.049) and preferred periapical technique )p=0.037).this was in contrast to the findings by other studies ^[5] where MDS had a better attitude score probably due to better exposure to relevant scientific literature and continuing dental education programs. This indicates that the prevailing attitude towards radiation protection is very casual in west Bengal dentists.

Use of rectangular collimator reduces the dose about 5 times in comparison to circular cone.^[6] In our study only 27% of the dentists used rectangular collimator, the results were slightly higher than other studies Math et al(7%),^[6] Belgium (6%), ^[7] Turkey5.5%. ^[3]

About 50% of the study population thought 0.5-0.8 sec as the ideal exposure time. But with increased use of handheld portable x-ray devices with lesser kvp (most uses 60kvp) the duration of exposure used is often longer.^{[8 ]} In good agreement with another study ^[6] 62.2 % of the dentists used E speed films. Interestingly survey showed 5.1% used self processing films. Since self processing films are not commonly available in West Bengal does it reflect social desirability bias?

Only 8.9 %( 14) used digital radiography which is less than the results of Ilguy et al,^[3] Kaviani et al^[9]. Dentist should be encouraged to use faster films and digital radiography as it requires only half the exposure of E speed films.^[6] Only a mere 3.2% used film holders, in others patient, dentist or assistant used to hold the film. Use of bisecting angle technique is more common than paralleling in consistent with results of other studies. ^{[3, 6, 7 ]}Another interesting finding was that those using digital sensors rarely used a film holder. This is completely paradoxical practice. Use of paralleling cone technique along with film holder reduces unnecessary exposures- ALARA[^6] is followed.

87.3% used manual processing or both, only 3.8% automatic processing rest used digital imaging. Results are in good agreement with Math et al^[6] (92%), Ilguy et al ^[3](85%). 83.3% of those using manual processing threw the processing solutions in sewage drains and lead foils in dustbins indicating that the set guidelines of biomedical waste management are equally not followed.

Handheld portable x-ray devices are increasingly used for intraoral radiography. There are no set guidelines for duration of exposure, position -distance rule is not followed, radiation safety of operator is in question as the unit is hand held, set angulations for exposures intraoral periapical radiographs cannot be met especially for lowers as the x-ray unit is obstructed by the patients upper thorax and shoulders. The authors are in agreement Berkhout et al [10] for an international set guidelines for hand held digital x-ray.

In contrast to the study Binnal A^[5] where respondents with ›11 years of experience in practice had better radiation protection practices we found younger dentists had better radiation protection practice probably attributed to training in undergraduate course.

Most dentists do not take radiographs irrespective of the necessity if the patient is pregnant due to the fear of exposure of radiation to fetus. However a study by Kusama et al^[11] indicated that the fetus does not directly receive radiation doses during head and chest diagnostic exposures and that the absorbed dose was estimated at less than 0.01 mGy.

Threshold radiation dose for pregnancy termination is only above 25 rads or 250 mGy.^[12] Radiations threshold for the development of congenital defects during the most sensitive period is 0.2 Gy and the threshold for growth retardation and abortion is much higher.^[12]

The first semester is the most sensitive period during pregnancy^[13] and exposure threshold for the development of definitive defects increases after main organogenesis period.^[12] Nonetheless, no radiography procedure should be carried out on pregnant women unless there is an absolute necessity. When such procedures are undertaken, all the precautions should be exercised to minimize the radiation dose.^[14] Dentists had an acceptable level of awareness (51.3%) regarding pregnancy and radiation exposure. Only 16.7% (27) considered diagnostic radiation can be done in any trimester (with all precautions), 57%considered 2^nd trimester to be safest.

Given that the practice of holding the film by fingers and use of portable dental unit were high around 40.3 %( 63) of the dentist did not stand behind any barriers during exposure rather stood beside the patient. Many of the dentists were completely unaware of the position distance rule to be followed in case of lack of barrier. Only 59%of the responders knew correct distance to stand during exposure (>6ft), similarly only 55.8% knew the correct angulation to stand to avoid being in direction of primary and secondary radiation.

93.6% did not have any dose monitoring and 45.5% did not know of radiographic machine periodic calibration. The negative response in this survey on dosimetry is far higher than that reported by math et al only 40%.^[6] A large group of dentists never used lead apron and thyroid collars. This is irrespective of years of experience or qualification and gender which is unlike other studies.^[6,7] This brings forward the gaping difference in clinical practice and theoretical knowledge imbibed in undergraduate courses. Perhaps the fact that there was no recognition of dento-maxillofacial radiology as a specialty in West Bengal until 2009 shows the poor level of response. The result of the study should alert the dental professional societies that more attention to be given to the negligent attitude towards dental radiology practice. There are few limitations of this study. Study sample was localized to particular region were there was no undergraduate radiation protection training. Questionnaires based studies are susceptible to acquiescence (yea-saying) bias, deviation (faking bad) bias, and social desirability (faking good) bias.^[5]

Conclusion

At the age of CBCT we are still striving to follow minimal radiation protection measures. Government and dental authority should make it mandatory for all dentists to attend at regular intervals continuing dental education programs on basic imaging in dentistry and radiation protection. Set guidelines for hand held x-ray machine is must. Repeated reinforcement and training and the most significant factor- attitude in each dental professional to follow ALARA will certainly make a great difference in radiation protection for individual and the mass.