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the doses to  critical organs  of known sensitivity to the stochastic effects of radiation must be measured .
the highest risk in dental radiography are for leukemia and cancer of the thyroid , even in doses as low as 500 msv .
the aim of this study was to calculate the average surface radiation dose to the thyroid gland and gonads during full - mouth intraoral periapical ( iopa ) and maxillary occlusal radiography .
the various materials used were routine diagnostic instruments , namely rubber bands , pocket dosimeter , x ray machine 
explor  model , ektaspeed plus iopa films , ectaspeed plus occlusal film , and thyroid collar [ figures 1 and 2 ] .
pd4507 [ table 2 , figures 3 and 4 ] with a digital display manufactured by bhabha atomic research centre , mumbai , maharashtra , india was used to measure the surface radiation dose .
it also had the facility of depicting cumulative doses which made calculations of doses less than 1mr ( 10 gy ) possible .
this pocket dosimeter had the capacity to measure the maximum level of radiation upto 999mr ( 9.99 mgy ) .
other technical specifications are shown in table 1 specifications for a pocket dosimeter pocket dosimeter pd - 4507 pocket dosimeter with a charger besides , this pocket dosimeter had an added advantage over other conventional dosimeters in that the measured radiation dose was expressed in digits , which ruled out chances of error in reading , unlike the pen dosimeter , where the reading was to be read against a meter which gave room for error in visual reading . however , like the pen dosimeter , the pocket dosimeter also made use of a geiger - muller counter .
the subjects for the study were average adult patients of age group ranging from 16 years to 65 years .
the x ray machine used was  explor  model from confident dental equipments , with standardized 65 kvp and 10 ma .
the films used were kodak ektaspeed plus iopa films of size 31  41 mm ( 1  1 inches ) and kodak ektaspeed plus occlusal films of size 57  76 mm ( 2  3 inches ) .
the patient was made comfortable and asked to sit on the dental chair . to measure the surface radiation dose at the thyroid level during full - mouth iopa radiography ,
the patient was positioned such that the mid saggital plane was perpendicular to the floor . for the maxillary five film series ,
the head of the patient was adjusted such that the maxillary occlusal plane was parallel to the floor .
the x ray cone angulation was set at + 40 , + 45 , + 30 , + 20 degrees for maxillary iopa films for anterior teeth , canines , premolars , and molars , respectively .
for the mandibular five- film series , the head of the patient was adjusted such that the mandibular occlusal plane was parallel to the floor , upon opening the mouth .
the x ray cone angulation was set at -15 , -20 , -10 , -5 degrees for mandibular iopa films for anterior teeth , canines , premolars , and molars , respectively .
the dosimeter was placed at three levels , namely the isthmus , right lobe , and the left lobe [ figures 57 ] and the average dose was calculated . the total number of subjects taken amounted to 60 , 20 each , for the three levels , namely the right lobe , the left lobe , and the isthmus .
dosimeter at the isthmus level of thyroid gland during full - mouth iopa radiography dosimeter at the right lobe level of thyroid gland during full - mouth iopa radiography dosimeter at left lobe level of thyroid gland during full - mouth iopa radiography to measure the surface radiation dose at the thyroid level during maxillary occlusal radiography [ figure 8 ] , the head of the patient was adjusted such that the mid saggital plane was perpendicular to the floor .
the head of the patient was positioned such that the maxillary occlusal plane was parallel to the floor .
dosimeter at the thyroid gland level in maxillary occlusal radiography the x ray cone was angulated at + 65 degrees and positioned such that the central rays passed between the eyes through the base of the nose .
the dosimeter was fixed in place as mentioned previously and doses were recorded at the thyroid level on the same patient .
this procedure was done on a total of 20 subjects . to measure the surface radiation dose at the gonadal region [ figure 9 ] , during a 10 film full - mouth iopa radiography
the dosimeter was placed in the center between the thighs , as close to the gonads as possible .
dosimeter at the gonadal region in full - mouth iopa radiography to measure the surface radiation dose at the gonadal region during maxillary occlusal radiography [ figure 10 ] , the patient was positioned as mentioned before and the dosimeter was placed on the center of thighs , as close to the gonads as possible .
dosimeter at the gonadal region in maxillary occlusal radiography after each reading , the dosimeter was reset and used for another subject .
the digital readings were recorded , tabulated , and the average dose for single patient was calculated .
the surface radiation doses observed at the isthmus level , at the level of the right and left lobe of the thyroid gland during a 10 film full - mouth iopa radiography , were 6.3 mrads , 13.9 mrads , and 12.6 mrads , respectively , and cumulative dosage was 10.93 mrads . the surface radiation dose at the thyroid level during maxillary occlusal radiography was 0.4 mrads . [ tables 35 ] total number of subjects average surface radiation dose in full - mouth iopa radiographs(10 films ) average surface radiation dose in maxillary occlusal radiography the surface radiation dose at the gonadal region during 10 film full - mouth iopa radiography and maxillary occlusal radiography was 0.4 mrads and 0.15 mrads , respectively .
dental radiographs and chest radiographs are the most common radiographs taken for routine investigations . radiation exposure to patients in dental radiographic examination has been investigated time and again .
many of the previous studies were based on based on methods or conditions that do not provide good bases for comparison .
most of the dose determinations have been done with phantoms , mannequins or , with cadavers .
no real effort has been made to determine the actual tissue - equivalence of dental phantoms as compared to living subjects . in 2004 , mortazavi et al estimated the entrance surface doses ( esd ) to skin at mandibular or maxillary arcs using tld badges to be 1.1730.606 mgy .
the use of pocket dosimeter in our study makes possible precise measurements of surface radiation dose in living subjects and rules out the chances of error in visual reading . until 1982
, the exposure dose to the thyroid gland in full - mouth examination using iopa radiography still remained as high as 49 mrads ( julian gibbs ) . similarly in 1980 , danforth and gibbs reported the radiation dose to the thyroid using 20 iopa films to be 400 gy to 920 gy , and to the parotid gland to be 130gy to 480gy . in our study , during full - mouth iopa radiographic survey using 10 films , radiation exposure dose to the thyroid gland was calculated as 10.93 mrads and the average radiation dose at the thyroid level during maxillary occlusal radiography was calculated as 1.5 mrads . in 1982 , julian gibbs et al calculated the gonadal dose from a full - mouth iopa survey to be 2 mrads . similarly in 1993 , tarnjit saini et al found the radiation dose to the male gonadal region to be 0.8 mrads using 20 iopa films . in our study the surface radiation dose at the gonadal region during a 10 film intraoral full mouth radiographic survey and in maxillary occlusal radiography was found to be 0.4 mrads and 0.15 mrads , respectively .
to conclude , the surface radiation dose to the thyroid gland and the gonads was evaluated during a 10 film full - mouth iopa and maxillary occlusal radiography using a digital pocket dosimeter pd4507 .
this study may be beneficial for the dental professionals worldwide to undertake proper precautionary measures to limit the radiation dose and allay the fear among the patients regarding the dental radiography , if any .
aim : the quantitative aspects of radiation doses to critical organs can help the dental professionals to take the necessary radiation protective measures as deemed necessary and can help the general public to allay radiation exposure fear in dental radiography , if any . 
 our study determines the surface radiation dose to thyroid and gonads in full - mouth intraoral periapical ( iopa ) and maxillary occlusal radiography.materials and methods : a total number of 120 subjects participated in the study . 
 the surface radiation dose was estimated to the thyroid gland and the gonads in full - mouth iopa radiography using 10 iopa ( e speed films ) and in maxillary occlusal radiography . 
 the measurements were calculated using a digital pocket dosimeter ( pd-4507).results : the average dose at the thyroid gland level during full - mouth intraoral and maxillary occlusal radiography was estimated to be 10.93 mrads ( 1.093  10 - 2 mgy ) and 0.4 mrads ( 4.0  10 - 2 mgy ) , respectively . 
 the average surface radiation dose at the gonadal region during a full mouth intraoral and maxillary occlusal radiography was estimated to be 1.5 mrads ( 1.5  10 - 2 mgy ) and 0.15 mrads ( 1.5  10 - 3 mgy ) , respectively.conclusion:our results suggest that although the radiation exposure doses to critical organs namely thyroid and gonads is within the safe limits still precautionary measures for these organs are advocated .