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Survey and analysis of roentgen exposure of dentists: preliminary report
Y A L E — H A U P T F U E H R E R . ! . V O L U M E 58, A P R IL 1959 • 49
5. Massier, M .; Schour, I., and Chopra, B. Occurrence of gingivitis in suburban C hicago school children. J . Periodont. 21:146 Ju ly 1950. 6. Burket, L. O ral medicine. Lippincott C o., 1946, p. 599. 7. of
Philadelphia.
J.
B.
United States Department of Agriculture, Bureau Human Nutrition and Home Economics. National
food guide, AIS-53. Washington, D. C., Government Printing Office, 1946. 8. Lyons, H arry. Acute necrotizing periodontal dis ease: an appraisal of therapy and a critical criterion. J.A .D .A . 37:271 Sept. 1948. 9. Gratzinger, Max. Dynamic irritation as a cause of periodontal disease and the means for its elim ina tion. J.A .D .A . 37:294 Sept. 1948.
Survey and an alysis of roentgen exposure of dentists: prelim inary report
Seym our H . Y a le * D .D .S., and J. D . H a u p tfu eh rer,f Chicago
A survey was made o f the radiation re ceived by dentists in 113 Chicago dental offices with 122 x-ray machines. A l though the average dentist surveyed is operating his x-ray equipm ent under safe conditions, individual dentists can estab lish a m ore acceptable level o f personal safety b y: (1 ) establishment o f correct collimation and filtration in each x-ray m achine, (2 ) utilization of high-speed film to red u ce exposure, and (3 ) use o f a timer cord with a minimum length o f eight feet. T h e use o f filtration reduced the m achine’ s roentgen output by 18 per cent, and reduced the dosage to the oper ator by 43.4 per cent.
T h e current awareness o f potential radia tion hazards in the dental office has created a great deal o f unrest and co n fusion am ong the members o f the p ro fession. R ecent extensive studies1"4 by independent researchers in the field o f dental roentgenology have been signifi
cant in helping to solve this problem. H ow ever, to date, little work has been done in assessing the degree o f radiation exposure o f dentists, through a relatively large sampling o f dental offices. T h e purpose o f this study was to con duct a comprehensive survey o f the x-ray facilities in 200 dental offices, under ac tual operating conditions. This is a pre liminary report o f findings on 122 x-ray machines in 113 o f these offices. R E V IE W O F T H E L IT E R A T U R E
In a comprehensive review o f the liter ature, English5 indicated that many haz ards may exist in dental roentgenography when personnel are not aware o f the potential danger o f overexposure to roentgen rays. Budowsky and Kutscher6 made the first significant attempt to collect dataon roentgen-ray exposure o f dentists. N one o f the 71 dentists in their study received m ore than the then allowable m axim um dose o f 0.3 r per week, but nine o f them were exposed to more than
50 • THE JO U R N A L O F THE A M E R IC A N DENTAL A S S O C IA T IO N
(1 ) Name_________________________________________ (2 ) Age_______ (4 ) Address_________________________________ :________________________
( 3 ) Yrs. in Prac._ (5 ) Telephone-----
(6 ) Average num ber of days in office per week___ (7 ) Estimated num ber o f working weeks per year_____________ (8 ) Estimated number of single x-ray exposures per week-------------------Per cent o f exposures per operator: (9 ) D .D .S _______ % (1 0 ) Dental Asst_______ % (1 1 ) Hygienist______ % (1 2 ) D o you n ow subscribe to a film badge service ?______ (1 3 ) H ave you ever subscribed to a film badge service?______ (1 4 ) W hat brand of x-ray film do you use?______________________________________________________ Check speed o f x-ray film used: (1 6 ) M edium ______ (1 7 ) Fast_ (1 5 ) Slow______ (1 8 ) W hat is your average upper molar exposure?_________________/secon d . (1 9 ) Brand of x-ray m achine_____________________________________ (2 0 ) M odel No.. (2 1 ) Serial N o -------------------------- (2 2 ) Approx. age of m achine__________________ (2 3 ) Length o f timer cord-------------------------------ft. (2 4 ) H ow far do you stand from the patient’ s head during exposure?------------------- ----------- ft. (2 5 ) Have you added any filtration?_____________ (2 6 ) W hat k in d?______________________________ (2 7 ) H ow m u ch ?______________________________
Fill out this sh eet only if you have m ore than one machine. (2 8 ) Brand o f x-ray machine__________________________________ (2 9 ) M od el N o _______________ (3 0 ) Serial N o ------------------------------- (3 1 ) Approx. age of m achine________________ (3 2 ) Length (3 3 ) H ow far do you stand from the patient’ s head o f timer cord___________________________ ft. during exposure____________________ ft. (3 4 ) Have you added any filtration?____________________ (3 5 ) W hat kin d?____ !________________________________ (3 6 ) H ow m u ch ?_______________________
(3 7 ) Brand o f x-ray m achine(3 9 ) Serial N o ________________ o f timer cord___________________ during exposure?— (44 ) W hat k in d ?n g.
(3 8 ) M od el No._ (4 0 ) Approx. age of m ach in e. (4 1 ) Length ----- ft. (4 2 ) H ow far do you stand from the patient’ s head Jft. (4 3 ) H ave you added any filtration ?___ ________________ ---------------------------- (4 5 ) H ow m u ch ?__________________________ Radiation survey questionnaire
the currently acceptable m axim um dose o f 0.1 r per week.7 A fter a survey o f six typical dental offices, N olan and Patterson8 indicated that the facilities they found “ presented hazards in a greater or lesser degree.” T h ey further emphasized the need for every possible precaution inasmuch as all .operators were subject to some exposure. D ata were collected from three o f 32 additional machines in the same study. A n average output o f 178 r per minute was reported for these machines. Fixott, C laycom b and Pflugrad,9 in a
survey o f 37 machines, fou n d an initial average output o f 113.1 r per minute. W hen a lon g cone and filtration were employed, the output dropped to 10.2 r per minute. M E T H O D O F PROCEDURE
A radiation survey questionnaire was m ailed to a random sampling o f 600 dentists practicing in the C hicago area. Each dentist was advised that he would becom e eligible fo r a survey o f the radia tion output o f his x-ray equipment upon
YALE— HAUPTFUEHRER
completing and returning the question naire. The survey was conducted in two phases : ( 1 ) collection of specific items relating to operator and machine by means of the questionnaire and (2) measurement of the relative roentgen output of each machine and radiation dose to the operator. Four teams of senior students, in the College of Dentistry, University of Illi nois, (Bertram Goodhart, Stanley Heil man, Robert Hoehne, Richard Holt, Charles James, Calvin Johnson, Roland Rudnick and Edward Tye) were trained to operate the radiation-measuring equip ment employed in the survey. An addi tional senior student (Raymond Salvino) assisted in coordinating the program. Questionnaire • The questionnaire (Fig. 1) and covering letter were designed with the cooperation of B. Duane Moen, di rector of the Bureau of Economic R e search and Statistics of the American Dental Association. These were mailed to each of the 600 dentists. A self-ad-
Fiq. 2 • Method roentgen output
of measurement of relative
VO LUM E 58, APRIL 1959 • 51
Fig. 3 • "C utie Pie" survey meter
dressed, stamped envelope was enclosed to expedite the return of the completed questionnaire. Radiation Measurement • The offices chosen for the survey were divided into geographical areas and a team of student surveyors was assigned to each area. Ini tially, the student team contacted the dentists by telephone and set up appoint ments for the surveys. The dentist was asked to make a patient available for a single x-ray exposure. In making the spe cific survey, the student surveyors exam ined each machine for collimation and added filtration. The dentist was ques tioned on the number o f films used per full mouth survey and the specific loca tion of immediately adjacent x-ray equip ment. With the patient in the chair and the dentist using the conventional + 4 0 an gulation (maxillary occlusal plane par allel to floor) for the central incisor projection, a two-second exposure was made. The relative roentgen output and the dose to the operator were measured as follows: Measurement No. 1 (relative roentgen output) • The term “ relative roentgen output” is used to denote a variation from the actual cone tip dosage, created by the interposition of the nose between the cone tip and chamber, and is to be in terpreted as tissue-filtered dose.
52 • T H E JO U R N A L O F THE A M E R IC A N DENTAL A S S O C IA T IO N
Fig. 4 • Condenser roentgen meter and chambers
The Victoreen roentgen meter with the 25 r chamber was used. The cham ber was placed along a line connecting the point of the chin and the tissue overlying the anterior nasal spine (Fig. 2). Measurement No. 2 (dose to oper ator) • The “ Cutie Pie” survey meter and the Victoreen r meter (with 0.025 r chamber) were employed (Fig. 3 and 4). The “ Cutie Pie” survey meter and the Victoreen 0.025 r chamber were as sembled as a single unit. The complete assembly was held by the operator at navel level during the exposure (Fig. 5). The operator was asked to stand in the position he normally assumed during roentgen-ray examination. The operator was instructed to read the equilibrium position of the indicator needle of the “ Cutie Pie.” This represented the posi tion of the needle immediately before the exposure was terminated. When the “ Cutie Pie” survey meter reading was less than 15, that reading was recorded. In all other instances, the Victoreen r chamber reading was recorded. The approximate time per survey was five minutes.
machines and 22.6 per cent were colli mated (T able 1). 2. Whereas the average relative roent gen output of unfiltered machines was 1.74 r per second, the filtered machines showed a reduction in roentgen output of 18 per cent (Table 2 ). 3. Although the average timer cord length was 6.85 feet, the average operator-to-patient distance was only 4.97 feet. 4. Over 90 per cent of the dentists (average age 45.8 years) operated the x-ray equipment. Although 6.5 per cent o f the dentists had subscribed to a film badge service, none was currently sub scribing. 5. With unfiltered machines, the aver age operator dose was 0.219 mr per sec ond. Where filtration was employed (Table 3 ), this dosage was decreased by 43.4 per cent. 6. The average full-mouth roentgenographic examination utilized 14 films, with an average maxillary molar expo sure of 2.2 seconds. The weekly average of single exposures was 55.9. 7. The average relative roentgen out put varied in the different brands of machines from 1.35 r per second to 2.88 r per second (Table 4 ). 8. Forty-seven dentists indicated that x-ray equipment was present in neigh boring offices.
F IN D IN G S
1. The average age of the 122 ma chines surveyed was 11.6 years. Filtration Fig. 5 had been added to 16.8 per cent of these r-meter
• "C u tie assembly
Pie"
survey
meter-condenser
Y A L E — H A U P T F U E H R E R . . . V O L U M E 58, A P R IL 1959 • 53
Table 1 • Summary of radiation survey findings in 122 x-ray machines in 113 offices in Chicago A verage dose to operator (all machines)
.203 mr/sec.
Average dose to operator (filtered machines)
.124 trir/sec.
A verage dose to operator (unfiltered machines)
.219 mr/sec.
A verage relative r output (all machines)
1.67
r/sec.
Average relative r output (filtered machines)
1.42
r/sec.
A verage relative r output (unfiltered machines)
1.74
r/sec.
A verage distance from operator to patient Average length of timer cord Filtration (added)
4.97
feet
6.85
feet
16.8
% %
output. A possible explanation o f this phenom enon is the incorporation o f m ore effective inherent filtration in this group. W hereas added filtration in a m achine effected som e decrease in relative roent gen output, the operator dose was de creased even more. This may indicate that filtration is effective in reducing
Table 2 • Average relative roentgen output by age o f machine Age of machine (years)
1.74 r/sec.
1.42 r/sec.
18.4
1.77 r/sec.
1.55 r/sec.
12.4
11-15
1.83 r/sec.
22.6 45.8
ye ars
16-20
1.60 r/sec.
Average age of machines
11.6
years
over 20
1.35 r/sec.
6.5 0
Average single exposures Average molar exposure Average number of films per full mouth examination
55.9 2.2
<%>
6-10 '
Collimation
Previous film badge subscription
Decrease
0- 5
A verage ag e o f dentists
Current film badge subscription
Filtered
Unfiltered
%
% per week
Table 3 • Relation of operator-to-patient distance to operator dose
sec. Distance (feet)
Dose
Unfiitered machine
Filtered machine
14 3 or less
9. T h e evaluation o f film speeds used was inconclusive because o f inconsistency in reporting by the dentists. A com plete summary o f the basic find ings is shown in T able 1. D IS C U S S IO N
Although n o attempt was m ade to differ entiate between methods o f filtration, several types were observed. Some m a chines were filtered with copper and aluminum, by the m ethod o f Y ale and G oodm an,3 and others utilized aluminum only. M achines in the 11 to 15 year old age group had the highest relative roentgen output. O ld er units showed a decrease in relative roentgen output with age be cause o f tube wear. New er machines also showed a decrease in relative roentgen
.239 mr/sec.
4-5
.232 mr/sec. .095 mr/sec.
6-7
.202 mr/sec.
more than 7
.116 mr/sec. .003 mr/sec.
Table 4 • Relationship between brand of x-ray ma chine and relative roentgen output
Brand
XRM G . E.
Number of Average age Average relative (yrs.) r output (r/sec) machines 3 45
Fischer
7
X-Cel-Ray
8
5.3
1.35
13.37
1.39
16.9
1.43
5.19
1.56 1.61
Mattern
4
8
W eber
17
Ï2
1.74
Misc.
2
13
1.81
Ritter
30
10.13
1.90
M eyer
6
12.8
2.88
122
11.6
1.67
(total)
(av.)
(av.)
54 • T H E JO U R N A L O F THE A M E R IC A N DEN TA L A S S O C IA T IO N
secondary radiation without an appre ciable loss o f direct radiation energy. T h e average dentist covered in this survey is statistically “ safe.” How ever, individual dentists may not be operating within the limits o f safety as recom m end ed by the National Bureau o f Standards.7 M any dentists are receiving more than the m axim um permissible dose per sec on d 10 and are safe only because o f limited utilization o f x-ray equipment. Certain measures which are m andatory if the dentist is to remain within per missible exposure limits are: (1 ) estab lishment o f correct collim ation and fil tration in each x-ray m ach in e; (2 ) utilization o f high-speed film to reduce exposure further; (3 ) use o f a timer cord o f a m inim um length o f eight feet. SUM M ARY
This article is a preliminary report o f a survey o f the status o f radiation exposure o f dentists in 113 dental offices with 122 x-ray machines. As a result o f a random sampling o f 600 C hicago area dental offices via a radiation survey question naire, 42 per cent o f the dentists re sponded, requesting the survey service. Four teams o f senior dental students at the College o f Dentistry, University o f Illinois, conducted these office surveys. Relative roentgen output o f the machine, and dose to the operator were measured.
In terms o f his ow n safety, the “ statis tical dentist” in this survey is operating his x-ray equipm ent under safe con di tions. H ow ever, evaluation o f the data indicates that certain individual dentists can establish a m ore acceptable level o f personal safety by collim ation and filtra tion o f the x-ray machine, employm ent o f m ore sensitive film and increasing the timer cord length. T h e elem ent o f patient safety was not investigated in this study.
*Professor and head of department of radiology, C o l lege of Dentistry, University of Illinois. jC h ie f dental x-ray technician, department of ra d i ology, Co llege of Dentistry, University of Illinois. 1. Stanford, R. W ., and Vance, J . Quantity of ra d ia tion received by the reproductive organs of patients during routine diagnostic x-ray examinations. Brit. J . Radiol. 28:266 M ay 1955. 2. Etter, L. E. Radiation dose reduction by higher voltage dental roentgenography. J.A .D .A . 53:305 Sept. 1956. 3. Yale, S. H., and Goodm an, 1. S. Reduction of radiation output of the standard dental x-ray machine utilizing copper for external filtration. J.A .D .A . 54:354 March 1957. 4. Richards, A . G . Roentgen-ray radiation and the dental patient. J.A .D .A . 54:476 A pril 1957. 5. English, Ja m e s A . An analysis of the dangers of x-ray irradiation. D. Radiog. & Photog. 25:1, 1952. 6. Budowsky, Ja c k , and Kutscher, A . H . Exposure of x-radiation during the general practice of dentistry. New York D. J . 19:298 June-July 1953. 7. U. S. Department of Commerce. Addendum to radiation handbook 60. National Bureau of Standards, Washington, D. C ., Government Printing Office, 1957. 8. Nolan, W . E., and Patterson, H. W . Radiation hazards from the use of dental x-ray units. Radiology 61:625 O ct. 1953. 9. Fixott, H. C .; Claycom b, C . K., and Pflugrad, A. Dental office radiation hazards. Oregon D. J . 25:2 Jun e 1956. 10. U. S. Departm ent of Comm erce. M edical x-ray protection up to two million volts. National Bureau of Standards handbook 41. Washington, D. C., Government Printing Office, 1949.
Sym phony of Science • A great scientific contribution is like a beautiful mosaic m ade up of many stones, or like a marvelous symphony to which many musicians contribute their share, but no one of which constitutes the mosaic or the symphony itself. Selman A . Waksman.
5. Massier, M .; Schour, I., and Chopra, B. Occurrence of gingivitis in suburban C hicago school children. J . Periodont. 21:146 Ju ly 1950. 6. Burket, L. O ral medicine. Lippincott C o., 1946, p. 599. 7. of
Philadelphia.
J.
B.
United States Department of Agriculture, Bureau Human Nutrition and Home Economics. National
food guide, AIS-53. Washington, D. C., Government Printing Office, 1946. 8. Lyons, H arry. Acute necrotizing periodontal dis ease: an appraisal of therapy and a critical criterion. J.A .D .A . 37:271 Sept. 1948. 9. Gratzinger, Max. Dynamic irritation as a cause of periodontal disease and the means for its elim ina tion. J.A .D .A . 37:294 Sept. 1948.
Survey and an alysis of roentgen exposure of dentists: prelim inary report
Seym our H . Y a le * D .D .S., and J. D . H a u p tfu eh rer,f Chicago
A survey was made o f the radiation re ceived by dentists in 113 Chicago dental offices with 122 x-ray machines. A l though the average dentist surveyed is operating his x-ray equipm ent under safe conditions, individual dentists can estab lish a m ore acceptable level o f personal safety b y: (1 ) establishment o f correct collimation and filtration in each x-ray m achine, (2 ) utilization of high-speed film to red u ce exposure, and (3 ) use o f a timer cord with a minimum length o f eight feet. T h e use o f filtration reduced the m achine’ s roentgen output by 18 per cent, and reduced the dosage to the oper ator by 43.4 per cent.
T h e current awareness o f potential radia tion hazards in the dental office has created a great deal o f unrest and co n fusion am ong the members o f the p ro fession. R ecent extensive studies1"4 by independent researchers in the field o f dental roentgenology have been signifi
cant in helping to solve this problem. H ow ever, to date, little work has been done in assessing the degree o f radiation exposure o f dentists, through a relatively large sampling o f dental offices. T h e purpose o f this study was to con duct a comprehensive survey o f the x-ray facilities in 200 dental offices, under ac tual operating conditions. This is a pre liminary report o f findings on 122 x-ray machines in 113 o f these offices. R E V IE W O F T H E L IT E R A T U R E
In a comprehensive review o f the liter ature, English5 indicated that many haz ards may exist in dental roentgenography when personnel are not aware o f the potential danger o f overexposure to roentgen rays. Budowsky and Kutscher6 made the first significant attempt to collect dataon roentgen-ray exposure o f dentists. N one o f the 71 dentists in their study received m ore than the then allowable m axim um dose o f 0.3 r per week, but nine o f them were exposed to more than
50 • THE JO U R N A L O F THE A M E R IC A N DENTAL A S S O C IA T IO N
(1 ) Name_________________________________________ (2 ) Age_______ (4 ) Address_________________________________ :________________________
( 3 ) Yrs. in Prac._ (5 ) Telephone-----
(6 ) Average num ber of days in office per week___ (7 ) Estimated num ber o f working weeks per year_____________ (8 ) Estimated number of single x-ray exposures per week-------------------Per cent o f exposures per operator: (9 ) D .D .S _______ % (1 0 ) Dental Asst_______ % (1 1 ) Hygienist______ % (1 2 ) D o you n ow subscribe to a film badge service ?______ (1 3 ) H ave you ever subscribed to a film badge service?______ (1 4 ) W hat brand of x-ray film do you use?______________________________________________________ Check speed o f x-ray film used: (1 6 ) M edium ______ (1 7 ) Fast_ (1 5 ) Slow______ (1 8 ) W hat is your average upper molar exposure?_________________/secon d . (1 9 ) Brand of x-ray m achine_____________________________________ (2 0 ) M odel No.. (2 1 ) Serial N o -------------------------- (2 2 ) Approx. age of m achine__________________ (2 3 ) Length o f timer cord-------------------------------ft. (2 4 ) H ow far do you stand from the patient’ s head during exposure?------------------- ----------- ft. (2 5 ) Have you added any filtration?_____________ (2 6 ) W hat k in d?______________________________ (2 7 ) H ow m u ch ?______________________________
Fill out this sh eet only if you have m ore than one machine. (2 8 ) Brand o f x-ray machine__________________________________ (2 9 ) M od el N o _______________ (3 0 ) Serial N o ------------------------------- (3 1 ) Approx. age of m achine________________ (3 2 ) Length (3 3 ) H ow far do you stand from the patient’ s head o f timer cord___________________________ ft. during exposure____________________ ft. (3 4 ) Have you added any filtration?____________________ (3 5 ) W hat kin d?____ !________________________________ (3 6 ) H ow m u ch ?_______________________
(3 7 ) Brand o f x-ray m achine(3 9 ) Serial N o ________________ o f timer cord___________________ during exposure?— (44 ) W hat k in d ?n g.
(3 8 ) M od el No._ (4 0 ) Approx. age of m ach in e. (4 1 ) Length ----- ft. (4 2 ) H ow far do you stand from the patient’ s head Jft. (4 3 ) H ave you added any filtration ?___ ________________ ---------------------------- (4 5 ) H ow m u ch ?__________________________ Radiation survey questionnaire
the currently acceptable m axim um dose o f 0.1 r per week.7 A fter a survey o f six typical dental offices, N olan and Patterson8 indicated that the facilities they found “ presented hazards in a greater or lesser degree.” T h ey further emphasized the need for every possible precaution inasmuch as all .operators were subject to some exposure. D ata were collected from three o f 32 additional machines in the same study. A n average output o f 178 r per minute was reported for these machines. Fixott, C laycom b and Pflugrad,9 in a
survey o f 37 machines, fou n d an initial average output o f 113.1 r per minute. W hen a lon g cone and filtration were employed, the output dropped to 10.2 r per minute. M E T H O D O F PROCEDURE
A radiation survey questionnaire was m ailed to a random sampling o f 600 dentists practicing in the C hicago area. Each dentist was advised that he would becom e eligible fo r a survey o f the radia tion output o f his x-ray equipment upon
YALE— HAUPTFUEHRER
completing and returning the question naire. The survey was conducted in two phases : ( 1 ) collection of specific items relating to operator and machine by means of the questionnaire and (2) measurement of the relative roentgen output of each machine and radiation dose to the operator. Four teams of senior students, in the College of Dentistry, University of Illi nois, (Bertram Goodhart, Stanley Heil man, Robert Hoehne, Richard Holt, Charles James, Calvin Johnson, Roland Rudnick and Edward Tye) were trained to operate the radiation-measuring equip ment employed in the survey. An addi tional senior student (Raymond Salvino) assisted in coordinating the program. Questionnaire • The questionnaire (Fig. 1) and covering letter were designed with the cooperation of B. Duane Moen, di rector of the Bureau of Economic R e search and Statistics of the American Dental Association. These were mailed to each of the 600 dentists. A self-ad-
Fiq. 2 • Method roentgen output
of measurement of relative
VO LUM E 58, APRIL 1959 • 51
Fig. 3 • "C utie Pie" survey meter
dressed, stamped envelope was enclosed to expedite the return of the completed questionnaire. Radiation Measurement • The offices chosen for the survey were divided into geographical areas and a team of student surveyors was assigned to each area. Ini tially, the student team contacted the dentists by telephone and set up appoint ments for the surveys. The dentist was asked to make a patient available for a single x-ray exposure. In making the spe cific survey, the student surveyors exam ined each machine for collimation and added filtration. The dentist was ques tioned on the number o f films used per full mouth survey and the specific loca tion of immediately adjacent x-ray equip ment. With the patient in the chair and the dentist using the conventional + 4 0 an gulation (maxillary occlusal plane par allel to floor) for the central incisor projection, a two-second exposure was made. The relative roentgen output and the dose to the operator were measured as follows: Measurement No. 1 (relative roentgen output) • The term “ relative roentgen output” is used to denote a variation from the actual cone tip dosage, created by the interposition of the nose between the cone tip and chamber, and is to be in terpreted as tissue-filtered dose.
52 • T H E JO U R N A L O F THE A M E R IC A N DENTAL A S S O C IA T IO N
Fig. 4 • Condenser roentgen meter and chambers
The Victoreen roentgen meter with the 25 r chamber was used. The cham ber was placed along a line connecting the point of the chin and the tissue overlying the anterior nasal spine (Fig. 2). Measurement No. 2 (dose to oper ator) • The “ Cutie Pie” survey meter and the Victoreen r meter (with 0.025 r chamber) were employed (Fig. 3 and 4). The “ Cutie Pie” survey meter and the Victoreen 0.025 r chamber were as sembled as a single unit. The complete assembly was held by the operator at navel level during the exposure (Fig. 5). The operator was asked to stand in the position he normally assumed during roentgen-ray examination. The operator was instructed to read the equilibrium position of the indicator needle of the “ Cutie Pie.” This represented the posi tion of the needle immediately before the exposure was terminated. When the “ Cutie Pie” survey meter reading was less than 15, that reading was recorded. In all other instances, the Victoreen r chamber reading was recorded. The approximate time per survey was five minutes.
machines and 22.6 per cent were colli mated (T able 1). 2. Whereas the average relative roent gen output of unfiltered machines was 1.74 r per second, the filtered machines showed a reduction in roentgen output of 18 per cent (Table 2 ). 3. Although the average timer cord length was 6.85 feet, the average operator-to-patient distance was only 4.97 feet. 4. Over 90 per cent of the dentists (average age 45.8 years) operated the x-ray equipment. Although 6.5 per cent o f the dentists had subscribed to a film badge service, none was currently sub scribing. 5. With unfiltered machines, the aver age operator dose was 0.219 mr per sec ond. Where filtration was employed (Table 3 ), this dosage was decreased by 43.4 per cent. 6. The average full-mouth roentgenographic examination utilized 14 films, with an average maxillary molar expo sure of 2.2 seconds. The weekly average of single exposures was 55.9. 7. The average relative roentgen out put varied in the different brands of machines from 1.35 r per second to 2.88 r per second (Table 4 ). 8. Forty-seven dentists indicated that x-ray equipment was present in neigh boring offices.
F IN D IN G S
1. The average age of the 122 ma chines surveyed was 11.6 years. Filtration Fig. 5 had been added to 16.8 per cent of these r-meter
• "C u tie assembly
Pie"
survey
meter-condenser
Y A L E — H A U P T F U E H R E R . . . V O L U M E 58, A P R IL 1959 • 53
Table 1 • Summary of radiation survey findings in 122 x-ray machines in 113 offices in Chicago A verage dose to operator (all machines)
.203 mr/sec.
Average dose to operator (filtered machines)
.124 trir/sec.
A verage dose to operator (unfiltered machines)
.219 mr/sec.
A verage relative r output (all machines)
1.67
r/sec.
Average relative r output (filtered machines)
1.42
r/sec.
A verage relative r output (unfiltered machines)
1.74
r/sec.
A verage distance from operator to patient Average length of timer cord Filtration (added)
4.97
feet
6.85
feet
16.8
% %
output. A possible explanation o f this phenom enon is the incorporation o f m ore effective inherent filtration in this group. W hereas added filtration in a m achine effected som e decrease in relative roent gen output, the operator dose was de creased even more. This may indicate that filtration is effective in reducing
Table 2 • Average relative roentgen output by age o f machine Age of machine (years)
1.74 r/sec.
1.42 r/sec.
18.4
1.77 r/sec.
1.55 r/sec.
12.4
11-15
1.83 r/sec.
22.6 45.8
ye ars
16-20
1.60 r/sec.
Average age of machines
11.6
years
over 20
1.35 r/sec.
6.5 0
Average single exposures Average molar exposure Average number of films per full mouth examination
55.9 2.2
<%>
6-10 '
Collimation
Previous film badge subscription
Decrease
0- 5
A verage ag e o f dentists
Current film badge subscription
Filtered
Unfiltered
%
% per week
Table 3 • Relation of operator-to-patient distance to operator dose
sec. Distance (feet)
Dose
Unfiitered machine
Filtered machine
14 3 or less
9. T h e evaluation o f film speeds used was inconclusive because o f inconsistency in reporting by the dentists. A com plete summary o f the basic find ings is shown in T able 1. D IS C U S S IO N
Although n o attempt was m ade to differ entiate between methods o f filtration, several types were observed. Some m a chines were filtered with copper and aluminum, by the m ethod o f Y ale and G oodm an,3 and others utilized aluminum only. M achines in the 11 to 15 year old age group had the highest relative roentgen output. O ld er units showed a decrease in relative roentgen output with age be cause o f tube wear. New er machines also showed a decrease in relative roentgen
.239 mr/sec.
4-5
.232 mr/sec. .095 mr/sec.
6-7
.202 mr/sec.
more than 7
.116 mr/sec. .003 mr/sec.
Table 4 • Relationship between brand of x-ray ma chine and relative roentgen output
Brand
XRM G . E.
Number of Average age Average relative (yrs.) r output (r/sec) machines 3 45
Fischer
7
X-Cel-Ray
8
5.3
1.35
13.37
1.39
16.9
1.43
5.19
1.56 1.61
Mattern
4
8
W eber
17
Ï2
1.74
Misc.
2
13
1.81
Ritter
30
10.13
1.90
M eyer
6
12.8
2.88
122
11.6
1.67
(total)
(av.)
(av.)
54 • T H E JO U R N A L O F THE A M E R IC A N DEN TA L A S S O C IA T IO N
secondary radiation without an appre ciable loss o f direct radiation energy. T h e average dentist covered in this survey is statistically “ safe.” How ever, individual dentists may not be operating within the limits o f safety as recom m end ed by the National Bureau o f Standards.7 M any dentists are receiving more than the m axim um permissible dose per sec on d 10 and are safe only because o f limited utilization o f x-ray equipment. Certain measures which are m andatory if the dentist is to remain within per missible exposure limits are: (1 ) estab lishment o f correct collim ation and fil tration in each x-ray m ach in e; (2 ) utilization o f high-speed film to reduce exposure further; (3 ) use o f a timer cord o f a m inim um length o f eight feet. SUM M ARY
This article is a preliminary report o f a survey o f the status o f radiation exposure o f dentists in 113 dental offices with 122 x-ray machines. As a result o f a random sampling o f 600 C hicago area dental offices via a radiation survey question naire, 42 per cent o f the dentists re sponded, requesting the survey service. Four teams o f senior dental students at the College o f Dentistry, University o f Illinois, conducted these office surveys. Relative roentgen output o f the machine, and dose to the operator were measured.
In terms o f his ow n safety, the “ statis tical dentist” in this survey is operating his x-ray equipm ent under safe con di tions. H ow ever, evaluation o f the data indicates that certain individual dentists can establish a m ore acceptable level o f personal safety by collim ation and filtra tion o f the x-ray machine, employm ent o f m ore sensitive film and increasing the timer cord length. T h e elem ent o f patient safety was not investigated in this study.
*Professor and head of department of radiology, C o l lege of Dentistry, University of Illinois. jC h ie f dental x-ray technician, department of ra d i ology, Co llege of Dentistry, University of Illinois. 1. Stanford, R. W ., and Vance, J . Quantity of ra d ia tion received by the reproductive organs of patients during routine diagnostic x-ray examinations. Brit. J . Radiol. 28:266 M ay 1955. 2. Etter, L. E. Radiation dose reduction by higher voltage dental roentgenography. J.A .D .A . 53:305 Sept. 1956. 3. Yale, S. H., and Goodm an, 1. S. Reduction of radiation output of the standard dental x-ray machine utilizing copper for external filtration. J.A .D .A . 54:354 March 1957. 4. Richards, A . G . Roentgen-ray radiation and the dental patient. J.A .D .A . 54:476 A pril 1957. 5. English, Ja m e s A . An analysis of the dangers of x-ray irradiation. D. Radiog. & Photog. 25:1, 1952. 6. Budowsky, Ja c k , and Kutscher, A . H . Exposure of x-radiation during the general practice of dentistry. New York D. J . 19:298 June-July 1953. 7. U. S. Department of Commerce. Addendum to radiation handbook 60. National Bureau of Standards, Washington, D. C ., Government Printing Office, 1957. 8. Nolan, W . E., and Patterson, H. W . Radiation hazards from the use of dental x-ray units. Radiology 61:625 O ct. 1953. 9. Fixott, H. C .; Claycom b, C . K., and Pflugrad, A. Dental office radiation hazards. Oregon D. J . 25:2 Jun e 1956. 10. U. S. Departm ent of Comm erce. M edical x-ray protection up to two million volts. National Bureau of Standards handbook 41. Washington, D. C., Government Printing Office, 1949.
Sym phony of Science • A great scientific contribution is like a beautiful mosaic m ade up of many stones, or like a marvelous symphony to which many musicians contribute their share, but no one of which constitutes the mosaic or the symphony itself. Selman A . Waksman.