INTRODUCTION
Dental radiographs play an irreplaceable role in conservative dentistry and endodontics. Radiographs, such as intraoral periapical radiographs (IOPARs) and bitewing radiographs made either in conventional or digital format are routinely employed in dental practice. The role of the radiographic tool starts from diagnosis and follows through all the stages of treatment and even postoperative evaluation in an endodontic practice.
Endodontists can be easily categorized as that group of dentists who are at high risk of radiation exposure given the nature of the occupation among the other dental professionals. Being the case, injudicious use of dental radiography without employment and utilization of accepted radiation precautions and protection can harm the individual in the long term, often inflicting irreparable damage to the personal and professional life.1-3
An Insight into the Potential Problem
As per the standard operating protocol in contemporary endodontics, IOPARs are the radiographs preferably utilized during endodontic treatment of a teeth.1,4 For any given treatment, four IOPARs are made at different stages of endodontics treatment, which include
Preoperative radiograph
Radiograph to determine the working length
Radiograph to confirm the master cone prior to obturation
Postoperative radiograph to confirm the treatment
In some or many cases requiring an endodontist's intervention, multiple radiographs with change in the angulation during any of the stages of the treatment due to the technical complexities may be needed in addition to the routinely used radiographs.
An IOPAR can be made in different modalities and the commonly utilized modalities are either conventional radiograph employing film-based technique or a digital radiography technique utilizing sensors. Quantitatively, under standard conditions and with usage of optimized, calibrated equipment, the radiation exposure from a single film-based IOPAR is 0.0095 mSv and a single digital IOPAR is 0.0031 mSv.5-7
Based on an empirical arithmetic (even though hypothetical, this following calculation is based on an unofficial, verbal survey of randomly selected 50 consultant endodontists), a busy consultant endodontist would be on an average doing five single-visit endodontic treatments per day and would be working for 300 days to the maximum. As per protocol, if all four radiographs are taken for every endodontic treatment, it accounts to 20 exposures for IOPARs per day. That adds up to 6,000 exposures per year for the busiest endodontist who follows the standard of care. The total exposure for a 1-year long work would be 57 mSv. If digital radiography is employed in all the operatory and is utilized, the exposure would be drastically reduced to 18.6 mSv.
Clinical Relevance of the Data
Ionizing radiation can have biologically damaging effects by two modes: Either by affecting the cell directly or free radicals-associated indirect effect. These effects are found to cause deoxyribonucleic acid damage.7,8 Biological hazards of radiation can be classified based on occurrence probability into nonstochastic and stochastic effect.9-11
Nonstochastic or deterministic effect, wherein a determined dose above which the damaging insults start to appear. Stochastic effect where there is no deterministic dose that could lead to biological damage. High-dose ionizing radiation (X-ray) has both deterministic and stochastic effects. In contrast to lower doses, radiation hazards are primarily stochastic rather than deterministic.12-14
The two average exposure values can be compared with the annual limits of radiation proposed by NCRP and ICRP. An endodontist taking IOPARs with conventional film-based technology at the above quantum would cross the annual limits of radiation exposure or more so touch the upper limits of radiation exposure levels. Correlating the data, it can be suspiciously concluded that there would be a greater probability of proneness to the stochastic effects of hazardous radiations (Table 1).
Improvements in the radiation equipment and proper adherence to radiation protection measures during exposure have been effective in mitigating most of the direct radiation injury.15,16 One of the greatest sources of radiation received by the dentist and the dental worker is by secondary radiation scattered from the patients’ facial bones.17
The International Commission on Radiological Protection (ICRP) developed the risk/benefit concept, which recommended that all patient exposures must be justified and kept as low as possible.18 It is a mandatory issue to follow the ALARA principle “As Low as Reasonably Achievable” during dentist routine work.19 It has been reported in the dental literature that ALARA principles are not strictly applied in the dental field,20,21 which can be of concern for the dental professional due to the ill effects of radiation.
The short-term effects of radiation on a tissue (effects seen in the first days or weeks after exposure) are determined primarily by the sensitivity of its parenchymal cells. When continuously proliferating tissues (e.g., bone marrow, oral mucous membranes) are irradiated with a moderate dose, cells are lost primarily by reproductive death, bystander effect, and apoptosis.22
The long-term deterministic effects of radiation on tissues and organs (seen months and years after exposure) are a loss of parenchymal cells and replacement with fibrous connective tissue.22
RISK VS BENEFIT OF DENTAL FILMS
The dose to the skin of the face is about 10 mGy when taking dental films using an open-ended cylinder. Therefore, a patient would have to receive 25 complete mouth radiographic series (CMRS) in a very short time to significantly increase the risk of skin cancer (Table 2).
Radiation to the lens of the eye may produce cataracts (a cloudiness of the lens). The X-ray dose associated with this problem appears to be about 2 Gy (2000 mGy). The dose to the eye from a CMRS, using an open-ended cylinder, is only about 0.6 mGy. So lens is not considered as an organ in danger.23
The thyroid gland is fairly resistant to radiation in the adult. However, thyroid cancer has been found in people who were exposed to a dose as low as 0.05 Gy (50 mGy) when they were children. The dose to the thyroid from a CMRS is only about 0.25 mGy. This dose to the thyroid can be further reduced by about half with the use of a thyroid collar. The use of a thyroid collar should be mandatory for children, since their thyroid tissues are more radiosensitive.24
Malignant changes in bone marrow may result in leukemia. There is active (blood-cell-producing) marrow in the mandible, skull, and cervical spine. About 13% of the total bone marrow lies in the head and neck areas. The dose to the bone marrow in a full-mouth series of radiographs is about 0.15 mGy. The X-ray dose associated with leukemia is about 50 mGy.
The genetic effects of radiation can have far-reaching results. However, the dose to the reproductive cells from dental radiography is very small, only about 0.005 mGy or less for males and 0.003 mGy for females. The female dose is lower because the reproductive cells are in more protected body location. If the patient wears a lead apron, exposure to the reproductive cells is virtually zero (0.000–0.0003 mGy).14
OPERATOR PROTECTION FROM RADIATION
People who work with radiation (that includes you) are also entitled to protection from radiation. There are exposure limits for occupationally exposed radiation workers.
Table 2: Radiosensitivity of Different Organs
| High | Intermediate | Low |
| Lymphoids | Vasculature | Optic lens |
| Bone marrow | Cartilage | Muscle |
| Testis | Bone | |
| Intestine | Salivary glands | |
| Mucous membrane |
The maximum permissible dose (MPD) is the dose of radiation to the whole body that produces very little chance of somatic or genetic injury. The MPD for whole-body exposure per year for occupationally exposed personnel is 0.05 Sv (5 rem). An age-based formula has also been developed as guideline for any accumulated dose (N in years).
Planning and Designing of a Safe Radiology Department
Radiation area should be at one corner in the building such that at least two walls open to the environment.
One extra thickness of brick with barium plaster is a must for the walls.
Warning board and light should be seen, when the machines are operating, at the entry.
The barriers should have 2 mm or more of lead and it should go at least 12 inches below the ground.
All the timers, control consoles should be kept behind the lead barriers.
Conch shell design: The operatory that contains the X-ray unit should be constructed in such a manner that it protects people in surrounding areas from radiation.
Film badge service: Is a good way to keep track of occupational exposure. Badges are worn by personnel at all times while at work, and are regularly sent to the company providing the service. Written reports of the exposure recorded on the badges are provided. If proper safety precautions are followed, no one in a dental office should receive radiation doses close to their MPD.
Lead barrier: It is preferable that the operator stands behind lead barrier while exposing films. The barrier should have a window or other means of monitoring the patient during the exposure.25 If no barrier is available, the operator should stand at least 6 feet away from the patient and in an area that lies between 90° and 135° to the primary beam. These are areas of minimum scatter radiation.
Never hold the film or tube: Dental personnel should never hold films for patients. If assistance is necessary, ask a family member or guardian to help. Be sure to protect the helper with lead apron as well. Dental personnel should also never hold the tube head for stability.