INTRODUCTION:

Radiographic examination is an indispensable adjunct to clinical examination in dentistry. It is also useful in explaining to the patient, the risks and benefits of the proposed treatment. The objective of dental radiography is to obtain diagnostic quality dental radiographs with minimum exposure to the patient, dental personnel and the public. X-rays used in diagnostic radiology are a type of ionizing radiation which has sufficient energy to ionize biological molecules.¹ The biological effects of ionizing radiation may be classified into deterministic and stochastic effects.

Deterministic effects happen due to high radiation dose and the severity of damage is directly proportional to the radiation dose.²Stochastic effects can manifest by exposure to any dose of radiation and highly unpredictable. There is no safe dose which cannot manifest stochastic effects.³ The exposure to radiation in the maxillofacial region may attribute to tumors of salivary glands, cancers of thyroid gland, may lead to osteoradionecrosis in patients undergoing radiation therapy for head and neck cancers.⁴ The adverse effect of radiation in pregnant women leads to low birth weight in the babies.⁵ Therefore, justification and optimization of dental radiology should be emphasized among dental professionals in order to avoid unnecessary radiation exposure.^6,7 ALARA stands for As Low As Reasonably Achievable. This principle guides the dental professionals in obtaining maximum diagnostic accuracy of radiographs using as minimal radiation dosage possible.^8,9

The basic safety factors including Time of exposure, distance between source and person and the Shielding using barriers made of lead plays a critical role. Efforts toward these objectives include Use of the fast film (F-speed) or digital image receptors, Assurance of adequate and proper X-ray tube filtration, kVp, mA and time, accuracy through regular maintenance and calibration by a qualified service technician and Operator protection that includes use of lead shielding and personal protective wear. Literature reveals that X-ray machines operating at kVp less than 60 leads to greater radiation exposure. Thus kVp should be kept between 60 to 80 for optimum exposure rates.¹⁰

Rectangular collimation of the X-ray beam is capable of restricting the X-ray beam size. Use of rectangular collimators results in 60% less exposure compared to round collimators.¹¹ The speed of radiographic film is dependent on sensitivity of emulsion of film to X-rays. By using fast speed films, lesser radiation exposure would be sufficient to produce images of good diagnostic accuracy. It has been proved by various studies that E and F speed film results in significantly lesser radiation exposure compared to that of conventional D films. Use of F speed films decrease exposure by 70% when compared to D speed films and 20% when compared to E speed films without affecting the quality of the image.¹²

Digital radiographs are known to reduce patient exposure by 75% when compared to D speed films, 50% when compared to E speed films and 40% when compared to F speed films.¹³ For procedures with CCD (charged couple device) and CMOS (complementary metal oxide Semiconductor) and PSP (Photostimulable Phosphor Plate) receptors, prepare the computer and imaging software prior to intraoral receptor placement. This helps reduce technique errors and the need for technique related retakes. The computer should be prepared before taking the x-ray to avoid unnecessary radiation exposure.

Dental personnel who perform dental radiography are responsible for adhering to all of the following radiation safety procedures for their own protection and also to protect Patient from Unnecessary Radiation Exposure. Especially for pregnant women, the first trimester is the stage of organogenesis where one must consider the risk benefit ratio, well ahead of planning for an X-ray and any other dental treatment.¹⁴ Praveen BS et al, revealed that unwanted radiation exposure to the developing fetus during 8 to 15 weeks of pregnancy may lead to greatest risk for chromosomal abnormalities and even mental retardation.¹⁵ Appropriate protective devices, such as protective aprons, to cover patient’s reproductive organs and a protective lead collar to protect patient’s thyroid gland during exposure should be used. The thyroid collar is mandatory especially for pregnant women and children as it is one of the most sensitive organs for radiation induced tumors. The parenchymal component of salivary gland is radiosensitive. Parotid gland is more sensitive to radiation compared to submandibular and sublingual glands.¹⁶

In situations where dental personnel cannot stand behind a protective barrier, they must stand at least 6 feet away from the patient and between 90- 135 degree to the primary X-Ray beam.¹⁷ The intensity of the primary X-ray beam, scatter radiation and leakage from the X-ray tube diminishes rapidly as the distance between the dental X-ray operator and the source of radiation increases.

The study was undertaken to create awareness about the various techniques for minimizing radiation, X-ray shielding, dosimeters and TLD badges for measuring exposure rates, Radiation protection devices and Quality Assurance Testing of X-ray equipment. The importance of Radiation protection apparel and awareness about recently introduced lead free apparels has been emphasized. The biological hazards of radiation should be analyzed and importance of Radiation protection has been emphasized.

MATERIALS AND METHODS:

A cross-sectional survey was conducted in the month of January, 2019. The questionnaire consisted of 15 questions and was structured under the headings of knowledge, attitude and practice. The questionnaire was distributed via google forms and responses collected. A total of 304 responses were collected and assessed. After collecting data, the statistical results were recorded and analyzed.

RESULTS:

Almost 60% of dentists were aware of the radiation protection protocols. Only 44% of them were aware of newer lead free options like the xenolite aprons. About 60% of dentists knew about the ideal distance between operator and patient according to inverse square law. (Fig. 1) Only 46% of them knew about optimization of staff and patient dose. 40% dentists suggested that thyroid collar, lead free apparel, lead glasses, gonad shield were the available radiation protection devices, out of which 29% suggested only lead apparel while only less than 6% suggested gonad shield usage for dental X-rays. (Fig. 2) Only 42% of dentists were aware of the care and maintenance of lead jackets. Around 40% of them suggested thyroid as the organ that is most susceptible to radiation in Dental radiology. 45% of the dental practitioners suggested that the inconveniences faced with regular use of lead apron include heavy weight, high cost as well as time consuming. Only 58% of them considered that it was important to periodically test and monitor the radiation dosage of X- ray equipment. About 43% of dentists suggested that the X- ray equipment should undergo Quality Assurance testing every year. RVG was suggested to be the most preferred mode of radiography followed by OPG. (Fig. 3) About 54% suggested RVG and 21% preferred OPG, for routine dental practice. 43% of dentists preferred F speed film, while 37% suggested use of E speed films. (Fig. 4) Although most of the dentists were aware of usage of lead aprons, only 29% used them regularly while taking dental radiographs. About 50% suggested TLD badges and 26% suggested pocket dosimeter to measure the radiation exposure. (Fig. 5)

The safe distance between x- ray equipment and the optimization of staff and patient dose needs more awareness among General practitioners. More than half population of dentists were not sure of Quality Assurance testing of X ray equipment and its duration and the thickness of lead barrier to be used. Most of the dental practitioners know about conventional radiation protective equipment but fail to use them in regular dental practice due to their heavy weight and increased cost.

Figure 1: Percentage of awareness about the distance between X ray source, patient and operator

Figure 2: Percentage of radiation protection device used by dentists

Figure 3: Percentage of mode of radiography preferred by dentists for routine dental practice

Figure 4: Percentage of dentists who use lead aprons while taking radiograph

Figure 5: Percentage of radiation protection device that are used in dental practice

DISCUSSION:

This KAP Survey was performed to assess the awareness among general practitioners regarding optimization of staff and patient dose, Radiation protective wear, care and maintenance of lead jackets, newer lead free radiation protection options that are available, Quality assurance testing of X-ray equipment and the thickness of lead barrier that should be used. The survey reveals that most of the dental practitioners were aware of the radiation hazards and the Protection equipment but failed to use them in regular practice. Lead jackets, being heavy has been neglected by the dentists. Xenolite aprons, have been recently introduced which is much lighter than lead and would be easier to use. More articles need to be published regarding the recent advances in Radiation protection devices and their efficacy when compared to the traditional lead jackets. Quality Assurance Testing of the X ray equipment needs to be done on a regular basis and the use of radiation monitoring devices should be made mandatory to the dental staff and assistant.

Bisecting angle technique involves steep vertical angulation which provides more radiation exposure to the thyroid gland and the eye lens.18] Paralleling technique comparatively involves less exposure.^19,20 As much as practical, the long axis of the body part being radiographed should be perpendicular to the main X-ray beam (called central ray or CR) and parallel to the image receptor . Use proper immobilization methods to assure that the patient does not move during exposure. Receptor holding instruments with beam alignment devices should be used instead of the patient retaining the image receptor with fingers. The focal spot- film distance should be well adjusted and in Modern machines, they have recessed tubes with FFD ranging from 8 to 12 inches

Dental personnel should take care that only the patient stays in the X-ray room prior to making an exposure. Any assistant or attender should stand behind a protective barrier. If someone must also be in the room to assist or maintain patient safety, then this individual must wear a protective apron. Lead aprons are classified as a secondary barrier to the effects of ionizing radiation as they protect an individual only from secondary radiation and not the primary beam. The quality of radiation protection depends on the thickness of lead apron. It is known that. Many studies have proved 0.25 mm lead thickness attenuates 66% of the beam at 75 kVp and 1mm attenuates 99% of the beam at same kVp. It is recommended that for general purpose radiography the minimum thickness of lead equivalent in the protective apparel should be 0.5mm but not less than 0.25 mm of lead or lead-equivalent thickness. A specially designed lead-impregnated thyroid collar can be used to protect the thyroid gland from excessive radiation during intraoral X-ray exposures.

Protective aprons are primarily designed to protect the wearer from scatter radiation and not the main primary beam. This is the reason why small beam (rectangular) collimation is preferred. Wearing ill-fitting protective garments can result in insufficient protection and discomfort. Larger size aprons inflict ergonomic strain due to excess weight. Overly small garments may not cover the body sufficiently, leaving areas exposed.²¹

Proper storage of protective aprons prolongs their life and effectiveness. It is imperative that lead aprons are not abused, such as by dropping them on the floor, piling them in a heap or improperly draping them over the back of a chair. These actions can cause internal fracturing of the lead and compromise the protective ability of apron. Aprons should be put in hangers without folding them because creases produced by folding leads to crack formation that will allow the radiation to penetrate. The radiation protection apparel should be checked annually to check for any cracks or tear that would compromise the efficiency of the aprons.

According to NCRP’s recommendation, the maximum permissible exposure should not be exceeding 0.1 rem or 1mSv. The ability of the apron material to stop X-rays is measured in “lead-equivalent” thickness that is equivalent to the same thickness of solid lead. Thus, 0.25 mm of lead-equivalent is equal to 0.25 mm of solid lead. The lead-equivalent thickness is stated on a label on the hem of the apron. AERB has laid down recommendations for personnel protection of radiation workers. The protective barrier between the operator and X-ray tube should have a minimum lead equivalence of 1.5mm. Protective aprons and gloves should have a minimum lead equivalence of 0.25mm, and gonadal shields should have a minimum lead equivalence of 0.5mm. Any additional radiation protection devices such as thyroid collar, hand gloves, eye glasses with side shield, should have a minimum of 0.5mm lead equivalence. Thyroid collars made with barium sulfate bismuth oxide composite are light weight alternatives to the standard lead thyroid shields and weigh 27% less than the standard lead collars.²² Mobile shields of 0.5mm lead equivalence with 1mm equivalent lead apron attenuates 98% of scatter.²³ When placed between patient and operator and outside of the primary beam, this shield can reduce the operator doses by 44%^{23, 24.}

Despite the benefits of radiation protection garments, their weight and fit can cause musculoskeletal pain and injury, especially to the spine.²⁵ These ergonomic issues have been addressed by manufacturers by incorporating lead alternatives to make lighter protective aprons. Lead composite shielding materials combined with cadmium, tin, iodine, barium, antimony or tungsten may decrease garment weight compared with use of lead alone but have mixed attenuation efficiencies^26,27 With the advent of newer modes of radiography, the quantity of radiation exposure have been greatly reduced. The RVG (Radio Visuo Graphy) has lesser exposure rates compared to the conventional techniques. The necessity for full mouth radiographs using conventional techniques have been greatly reduced after the OPG was introduced. RVG has been the favorite choice of endodontists. The dosimeters are efficient only when they are worn at the right position and monitored regularly to measure the amount of radiation exposure. Dosimeters used for personnel monitoring have dose measurement limit of 0.1 - 0.2 mSv (10-20 mrem)28] The use of radiation monitoring device should be made mandatory to all dental personnel taking radiographs. Periodically they should be measured to stay within the dose limits. Dosimeter should be worn on the outside of personal protective equipment at the level of shoulder to approximate lens and thyroid exposure.^29,30

CONCLUSION:

Awareness should be created among the general practitioners regarding the hazardous nature of the cumulative effect of radiation. The use of these lead free aprons has reduced the amount of physical strain greatly but validation of their attenuating properties in comparison to lead aprons, needs more rigorous testing. The recent lead free jackets made of Xenolite have the advantage of being light weight and would also be a cost effective option. The dental professionals should constantly update their knowledge about various radiation protection protocols and devices that are recently introduced. Quality assurance testing of X-ray equipment should be made mandatory in every clinic.

CONFLICT OF INTEREST: Nil

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Received on 22.04.2019 Modified on 25.06.2019

Research J. Pharm. and Tech. 2020; 13(1): 81-85.

DOI: 10.5958/0974-360X.2020.00015.3