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Degradation of Dental Radiographic Processing Solutions
Degradation of dental radiographic processing solutions Th e
d e n ta l p r o f e s s io n
depends
on
r a d io g r a p h s
in p r o v id in g p a t ie n t s w it h o r a l h e a lt h c a r e o f th e
C ecil E. Brown, Jr., DDS Robin J. Winkworth, LDS, RCS
h ig h e s t
sta n d a rd s.
F o r
p la n n in g ,
it
is
im p e r a t iv e
O rville V. Anderson
g ra p h s b e p ro d u ce d
Albert C. Jerm an , DDS, Brooks Air Force Base,
t h e p a t ie n t .
Tex
M uch sa fe , u se .
The activity of radiographic processing solutions was m onitored by densitometry readings in this study to determ ine the number of satisfactory ra diographs that could be produced before degrada tion of the solution occurred. In 86 processing sessions, 7,890 fu lly exposed radiographs and 199 control radiographs were processed. Degradation was first noticed at the 74th processing session when 6,965 radiographs had been processed, but even at the end of the study, the radiographs pro cessed in the solution were of an acceptable qual ity.
in t e r p r e t iv e
e x a m in a
t io n s , f o r a d e q u a t e d ia g n o s is , a n d f o r tre a tm e n t
be
has
been
r e lia b le
r e g u la t e d
done
o u tp u t
to
th e
q u a lit y
d e v e lo p
th a t
and
e n su re
a n d h ig h -s p e e d f ilm r a d ia t io n
to
e q u ip m e n t
R a d ia t io n
th a t
r a d io
w it h m in im a l ir r a d ia t io n o f
is
e le c t r ic
p ro p e r
t im e r s
f ilm
h a s re d u ce d
p a t ie n t r e c e iv e s .
r e la t iv e ly
c o n v e n ie n t
to can
e xp o su re ,
th e a m o u n t o f
Th ese
im p r o v e
m e n ts a r e r e a s s u r in g ; h o w e v e r , w it h o u t q u a lit y c o n tro l
in
gra p h s
can
f ilm
p r o c e s s in g ,
r e s u lt .
in g t e c h n iq u e s a r e r e c o g n iz e d le m
in
t h is p h a s e
c e s s e d f ilm p a t ie n t a n d
in a d e q u a t e
In c o n s is t e n c ie s
in
r a d io
p ro ce ss
a s a m a jo r p r o b
o f d e n t is t r y . Im p r o p e r ly p r o
o ft e n n e c e s s it a t e s r e e x p o s u r e o f th e m ay
a ls o
le a d
to
in c o r r e c t d ia g n o
s is . A u t o m a t ic p r o c e s s in g u n it s a r e n o w a v a ila b le th a t
re d u ce
som e
of
th e
p r o b le m s ;
h o w e v e r,
h a n d p r o c e s s in g is s t ill u s e d in m a n y d e n t a l o f f ic e s . I n is
1200 ■ JADA, Vol. 87, November 1973
th e
e it h e r in s t a n c e , th e d e v e lo p in g p r o c e s s
sam e, an d
th e fin a l p r o d u c t d e p e n d s
on
Fig 1 ■ Aluminum step wedge designed for periapical radiographs: (1) step wedge; (2) periapical radiographic film packet; (3) pressboard packet stabilizer; (4) lead insert. the meticulousness of each phase. Much has been written on darkroom tech niques and equipment.1' 18 Procedures in timetemperature techniques, proper lighting, and methods for handling film have been well estab lished. One area o f radiographic processing that has not been adequately covered is the life of the processing solution.
D e ve lo p in g p ro cess and s o lu tio n d e g ra d a tio n The developing process, a complicated chem ical procedure, has been covered well in the lit erature. Radiographic films are coated with an emulsion impregnated with silver halide crys tals. These crystals are sensitive to X rays or light and form an invisible latent image when exposed. The developing process chemically converts the invisible latent image into a visible image. Reducing agents in the developing solu tion, such as Elon and hydroquinone, convert the exposed silver halide crystals into black me tallic silver that forms the visible image. The fixer contains a clearing agent, sodium or ammonium thiosulfate, that dissolves and re moves the undeveloped silver halides from the emulsion. The process o f conversion of the exposed film into a developed radiograph causes a chemical exhaustion or degradation o f the processing so lution. According to Fuchs,1 the degradation of the solution is affected by the number o f films
processed and their densities, the rate of oxida tion, contamination, and the accumulation o f by-products of the developing reactions. H ow ever, the number o f films that can be processed and the rate at which oxidation and other detri mental actions occur before the quality o f radio graphs is affected are not clear. I f this informa tion is obtained, it can be used to maintain high quality in the processing of radiographs. In this study, the longevity of dental radiographic processing solutions was investigated in order to establish a method o f quality control in processing dental radiographs.
M e th o d s and m a te ria ls A series of periapical films was developed under controlled conditions. A controlled method of determining density and contrast by densitome try readings was adapted for dental radiographic equipment. The activity of the processing solu tion was monitored daily throughout the experi ment. A radiographic step wedge was construct ed for standard periapical film (Fig 1) and was used to produce control radiographs. Steps were designed to provide an image of six densities, an ideal range of contrast for this study (Fig 2). The lead plate insert was used to produce the lowest density. Periapical film packets could be stabilized against the base of the step wedge; this ensured against distortions in images because of discrepancies in object-film distances. A standard dental radiographic unit* that had Brown—others: DEGRADATION OF RADIOGRAPHIC SOLUTIONS ■ 1201
Fig 2 ■ Periapical radiograph produced from step wedge. Num bers have been inserted for identification of densities.
previously been standardized for timing, radia tion output, and meter accuracy was used to ex pose the control film . A ll exposures were made at about the same time of day in an effort to avoid voltage discrepancies. Exposures o f 0.6 second at 90 kv and 10 ma with a target-film distance of 14 inches were used to produce the control ra diographs. A calibrated densimetert was used for all readings. The step wedge was set on a marked platform so that it would be in the same position for each exposure. The radiographic unit was placed in position with the tube head at 90°. Its location was marked on the platform so that it could also be repositioned (Fig 3). A ll processing was done in a thermostatically controlled developing unit.$ Each tank accom modated 5 gal o f processing solution. The unit was located in a conventional darkroom that had been thoroughly inspected for light leaks, cleanliness, and safe light specifications. Before the formal investigation, the darkroom procedures o f the two investigators were stan dardized; they performed all processing using the following technique. The tanks were thor oughly cleaned, and the solutions (Kodak liq uid radiograph developer and replenisher, and fixer and replenished) were mixed using distilled water according to manufacturer’ s instructions. The solutions were stirred with separate stirring rods to prevent contamination. The tempera tures o f the solutions and water bath were ad justed to the optimum of 68 F. A laboratory mer cury thermometer was used. (Among the four available float type of darkroom thermometers, there was a difference of four degrees in read ings.) Films were immersed in the developing 1202 ■ JADA, Vol. 87, November 1973
Fig 3 ■ Top, view of step wedge and radiographic unit. Note location markers on platform. Bottom, radiographic unit and step wedge in position. solution for 4.5 minutes. Initially, the hangers were agitated for eight seconds by drawing them slowly in and out of the solution to ensure full surface coverage and to eliminate air bubbles. Subsequently, agitation was performed by rais ing the hangers out o f the solution for eight sec onds every 60 seconds to remove by-products from the film surface. This permitted fresh chem
w e re
s t e p -w e d g e c o n t r o l r a d io g r a p h s a n d 5 0 f u lly e x
r in s e d f o r e ig h t s e c o n d s , t h e n t r a n s f e r r e d to t h e
p o s e d d e g r a d a t io n r a d io g r a p h s w e r e p r o c e s s e d .
ic a ls
to
c o n t in u e
d e v e lo p m e n t . T h e
f ilm s
f i x i n g b a t h w h e r e t h e y r e m a in e d f o r e ig h t m in
T h e m e a n v a lu e s o f d e n s it o m e t r y r e a d in g s w e r e
u t e s . T h e y w e r e t h e n w a s h e d f o r 2 5 m in u t e s a n d
re co rd e d
d r ie d f o r 2 5 m in u t e s . A
s o lu t io n
a c t iv it y
w as
o m e try
r e a d in g s ,
and
sto p w a tc h w a s u se d fo r
t im in g . F u lly a p ic a l
e xp o sed
p e r ia p ic a l f ilm s
U lt r a - S p e e d
D e n ta l
o n th e c o n tro l g ra p h . N o o b se rve d a
d e cre a se
on
r e la t iv e ly
th e
in
d e n s it
s t r a ig h t
lin e
(K o d a k
P e r i
w a s p r o d u c e d o n th e g r a p h . T h is in d ic a t e d th a t
F ilm ,
P o ly -
th e p r o c e s s in g a n d e x p o s u r e p r o c e d u r e s f o r th e
X -ra y
s o ft p a c k e t § ) w e r e u s e d to d e g r a d e t h e s o lu t io n s .
c o n tro l
E x p o s u r e s w e r e m a d e b y p la c e m e n t o f th e f ilm
th e re
r a d io g r a p h s
w as
no
w e re
d e t e c t a b le
c o n s is t e n t ,
and
th a t
d e g r a d a t io n
of
s o lu
o n a w h it e t o w e l, w it h t h e m a r k e r n o t c h f a c in g
t io n s d u r in g t h a t p e r io d . I t
up.
f o r e , to in c r e a s e th e n u m b e r o f d e g r a d a t io n f ilm s
A n
o ve rh e a d
6 0 -w
in c a n d e s c e n t
b u lb
w as
p ro c e s s e d to
illu m in a t e d f o r o n e m in u t e .
N o
A t
Experim ental procedure
100 a t e a c h p r o c e s s in g s e s s io n .
m e a s u r a b le
d e te cte d
at
th a t
w a s d e c id e d , t h e r e
th e
t im e ,
lo s s
in
s o lu t io n
3 0 -se c o n d
2 ,7 0 0
f u lly
a c t iv it y
p r o c e s s in g e xp o sed
w as
s e s s io n .
d e g r a d a t io n
r a d io g r a p h s a n d 6 9 c o n t r o l r a d io g r a p h s h a d b e e n p r o c e s s e d . T h u s , th e n u m b e r o f th e o r ig in a l c o n
N in e t y
c o n s e c u t iv e
exp o sed
c o n tro l
w it h u s e o f th e
r a d io g r a p h s
ste p
4 Vi m o n t h s .
In
p le t e t h e
w e d g e . S o lu t io n s
w e r e d e g ra d e d in 8 6 s e p a ra te d a r k r o o m d u r in g
t r o l r a d io g r a p h s (9 0 ) w a s n o t s u f f ic ie n t to c o m
w e re
each
s e s s io n
n u m b e r o f c o n t r o l a n d d e g r a d a t io n
s e s s io n s a
expo sed
c e r t a in
r a d io g r a p h s
c e r t a in w it h
w e re p ro ce sse d . P r o c e s s in g p r o c e d u r e s w e re
sta rte d 48 h o u rs
a ft e r th e s o lu t io n s w e r e m ix e d . I n s io n , f iv e
ste p -w e d g e
in v e s t ig a t io n .
T h e re fo re ,
tw o
co n tro l if
no
th e
r a d io g r a p h s
e x p e r im e n t
e ffe c t
on
w e re
c o u ld
used
be
s t a n d a r d iz a t io n ,
u s in g
th e f ir s t s e s
o n ly d if fe r
e x p o s e d a n d f r e s h ly e x p o s e d r a d io g r a p h s . A f t e r th e 4 3 rd d a rk ro o m
b y f r e s h s o lu t io n s f o r e a c h o f th e s ix s te p s , a n d
c o n t r o l r a d io g r a p h s w e r e u s e d . B e c a u s e
d e n s it o m e t r y
um e
o b t a in e d
as
e n c e in d e n s it ie s w a s o b s e r v e d b e t w e e n t h e p r e
p r o c e s s e d to e s t a b lis h t h e b a s e lin e a s p r o d u c e d
w e re
to
c o n t in u e d ,
f r e s h ly e x p o s e d c o n t r o l r a d io g r a p h s . N o
c o n t r o l r a d io g r a p h s w e re
r e a d in g s
o r ig in a l
p r e e x p o s e d c o n t r o l r a d io g r a p h s a n d t w o f r e s h ly
fo r each .
lo s s ,
th e
s e s s io n , o n ly f r e s h ly e x p o s e d
u p p e r p o r t io n
o f th e
o f v o l
p r o c e s s in g
T h e f iv e v a lu e s f o r e a c h o f th e s te p s w e r e a v e r
h a n g e r s w a s n o t b e in g c o v e r e d b y t h e d e v e lo p
a g e d , a n d t h e m e a n v a lu e s w e r e p lo t t e d o n a c o n
in g
tro l g ra p h .
u s e d to k e e p
(W it h in
each
ste p
le v e l,
th e re
w as
th e
next
n in e
d a rk ro o m
f u lly
s e s s io n s ,
m o re
h a n g e rs
w e re
th e r a d io g r a p h s b e n e a t h th e s o lu
D u r in g t h e t o t a l 8 6 p r o c e s s in g p e r io d s , 7 ,8 9 0
d u r in g th e f ir s t s e s s io n , 5 0
d e g r a d a t io n r a d io g r a p h s w e r e p r o c e s s e d . F o r
P r o g r e s s iv e ly
t io n .
s lig h t d if fe r e n c e in t h e f iv e v a lu e s u s e d to e s t a b lis h a c o n t r o l.) A l s o
s o lu t io n .
e xp o sed
d e g r a d a t io n
r a d io g r a p h s
and
199
c o n t r o l r a d io g r a p h s w e r e p r o c e s s e d .
tw o
NUMBER OF PERIAPICAL RADIOGRAPHS PROCESSED+ CONTROLS 250 500 1000 1500 2000 2500 3000 3500 3800 4400 4900 5390 5890 6390 6790 7390 7890 +
+
+
20
+
+
+
40
+
+
+
+
60
+
80
+
+
+ +
100
+
¡3 0
+
T5T
TIME ELAPSED (DAYS)
Fig 4 ■ Graph shows density value of control radiographs for duration of investigation. Numbers on hori zontal lines correspond to densities in Figure 2. Brown—others: DEGRADATION OF RADIOGRAPHIC SOLUTIONS ■ 1203
R e sults Figure 4 illustrates the mean densitometry read ings charted for each processing period. The density units represent the common log o f opac ity of the developed silver. Lines one through six represent the respective step densities on the control radiograph (Fig 2); the vertical distance between each line indicates the contrast between each step. Figure 4 shows that the densities o f all steps remained relatively constant until the 74th pro cessing session. A t that point, 6,790 fully ex posed degradation radiographs and 175 control radiographs had been processed. The density of step six began to drop noticeably on the graph; however, the decrease was not yet visible. The decrease in density was the first indication that the activity of the solutions was beginning to weaken enough to affect the darker areas of radiographs. Densities not only decreased but the contrast between each step decreased, as indicated by the narrowing o f the space between each line on the graph. This was also evident on visual inspection. When a density dropped from its level to the level o f the next density, it could be seen visually; that is, when step five dropped from a reading o f 1.43 to a level o f 0.88 (which was the original reading for step four), these steps could be matched visually (Fig 5). Figure 6 represents the reproducibility of densitometry readings per processing time for each level o f the step wedge.
D iscu ssio n By following strict procedures, we processed a far greater number of periapical radiographs be fore degradation occurred than we had antici pated. Because of the drop in densities, degrada tion was considered to begin at the 74th process ing session. A t this time, 6,965 radiographs had been processed. By the end of the investigation at the 86th processing session, 8,089 periapical radiographs had been processed. Even at this point clinical radiographs processed in the solu tions were acceptable; however, this was sub jective, and no attempt was made to establish at what point radiographs become unacceptable. Theoretically, the fully exposed films used for degradation purposes were equivalent to a great er number o f clinical films. Because fully ex1204 ■ JADA, Vol. 87, November 1973
Fig 5 ■ Visual shift in densities of control radiographs after degradation occurred. Top radiograph was processed during first processing period; bottom radiograph was processed dur ing 79th processing period. STEPWEDGE STANDARD LEVEL____________ DEVIATION
MAXIMUM DIFFERENCE
l
.0 0 4 3 1
.0 2
2
.0 0 9 4 6
.0 5
3
.0 1 4 0 5
.0 7
4
.0 1 8 3 8
.0 9
5
.0 3 2 5 0
.1 7
6
.0 6 3 8 4
.2 8
Fig 6 ■ Standard deviation of reproducibility of densitometry readings pooled over all processing times for each step wedge level. Degrees of freedom equal 88. Maximum difference is larg est difference observed between densitometer readings made at same processing time. posed films were used in degrading the solu tions, more chemical activity was required to produce their total blackness; that is, the amount o f silver halides that had to be converted to metal lic silver was greater than that needed in the pro cessing of clinical radiographs. Oxidation was not the problem that it was ex pected to be. Although the processing tanks were covered, they were not airtight. I f oxida tion did occur, the solutions were not affected for four months. The loss of developing solution was a prob lem. Additional hangers had to be used so that
f ilm
c o u ld b e s u b m e r g e d , a n d in a c lin ic a l s it u a
t io n
t h is
w o u ld
be
im p r a c t ic a l.
R e p le n is h m e n t
s e e m s n e c e s s a r y to m a in t a in s o lu t io n le v e l r a th e r
and television branch, support services division at Brooks Air Force Base. Dr. Jerman, a lieutenant colonel, USAF DC, is chief, experimental dentistry function, dental sciences branch, clinical sciences division, Brooks Air Force Base.
t h a n c h e m ic a l a c t iv it y . S t a t is t ic a lly , t h e m e t h o d u s e d in t h is in v e s t ig a t io n w a s v a lid , a n d t h e f in d in g s h a v e b e e n w e ll s u p p o r t e d b y a d d it io n a l in v e s t ig a t io n .
Sum m ary D e g r a d a t io n
o f d e n ta l
r a d io g r a p h ic
p r o c e s s in g
s o lu t io n w a s c a r r ie d o u t in a c o n t r o lle d p r o t o c o l, a n d th e a c t iv it y
o f th e
s o lu t io n s w a s m e a s u r e d
b y d e n s it o m e t r y r e a d in g s . D u r in g f o u r m o n t h s , 6 ,7 9 0 f u l l y 175
e xp o sed
p e r ia p ic a l r a d io g r a p h s
c o n t r o l r a d io g r a p h s w e r e
d e g r a d a t io n ta n k
p ro ce sse d
and
b e fo re
o f t h e c o n t r o ls w a s d e t e c t e d . E a c h
a cco m m o d a te d
5
U S
g a l.
In
v ie w
o f th e
n u m b e r o f r a d io g r a p h s p r o c e s s e d a n d t h e le n g t h o f th e e x p e r im e n t , d e n t a l r a d io g r a p h ic p r o c e s s in g
s o lu t io n s s e e m
m o re
r a d io g r a p h s
to b e o f
c a p a b le
s a t is f a c t o r y
o f p r o c e s s in g q u a lit y
h a d b e e n a n t ic ip a t e d . A l s o , o x id a t io n be
le s s
o f
a
p r o b le m
under
th a n
s e e m s to
c o n t r o lle d
c o n d i
t io n s t h a n it w a s p r e v i o u s ly e x p e c t e d t o b e .
The research reported in this paper was conducted by person nel of the dental sciences branch, clinical sciences division, USAF School of Aerospace Medicine, Aerospace Medical Divi sion, Air Force Systems Command, US Air Force, Brooks AFB, Tex. Further reproduction is authorized to satisfy the needs of the US government. Dr. Brown, a lieutenant colonel, USAF DC, is chief of dental consultation, dental sciences branch, clinical sciences division, US Air Force School of Aerospace Medicine, Brooks Air Force Base, Tex, 78235. Dr. Winkworth, a squadron leader in the Royal Air Force, is an exchange dental officer in the dental sciences branch. Mr. Anderson is medical photographer, photography
* Model GE90-11-11AA2-2, General Electric Co., Milwaukee. t MacBeth transmission densitometer, model TD102. MacBeth Corp., Newburgh, NY. t Bar-Ray developing unit, model B-2440. Bar-Ray Products, Inc., Brooklyn, NY. § Eastman Kodak Co., Rochester, NY. 1. Fuchs, A.W. Principles of radiographic exposure and pro cessing, ed 2. Springfield, III, CharlesCThomas, 1958, p233. 2. Wainwright, W.W., and Villanyi, A.A. The simplest radiographic analyzer: the X-ray checker. J S Calif State Dent Assoc 28:122 April 1960. 3. Lozier, M. Significance of correct processing in intraoral roentgenography. I. Oral Surg 3:911 July 1950. 4. Lozier, M. Significance of correct processing in intraoral roentgenography. II. Oral Surg 3:1060 Aug 1950. 5. Sweet, A.P.S. X-ray processing solutions. Dent Radiog Photog 28:27 No. 2, 1955. 6. Stewart, J.L., and Drisko, R.R. An evaluation of rapid x-ray film processing solution. Oral Surg 22:334 Sept 1966. 7. Morrow, W.H. Processing of dental radiographs. Br Dent J 122:395 May 2, 1967. 8. Smith, N.J.D. The sensitometric evaluation of dental radiographic film. Br Dent J 129:455 Nov 17, 1970. 9. Webber, R.L., and Ryge, G. The significance of exposure parameters in dental radiography. Oral Surg 27:740 June 1969. 10. Feldman, M.L., and Bozen, S. Automatic processing of periapical film. Oral Surg 26:647 Nov 1968. 11. Pentel, L., and Hyman, M. A method of assaying x-ray de veloper activity. Oral Surg 24:777 Dec 1967. 12. Reid, J.A. Improved exposure and processing techniques in dental radiology. J Can Dent Assoc 33:474 Sept 1967. 13. Wuehrman, A.H.; Manson-Hing, L.R.; and Jamison, H.C. X-radiation in dental offices in Jefferson County, Alabama. II. Darkroom facilities and processing techniques. Oral Surg 16:1450 Dec 1963. 14. Degerlng, C.l. Dental roentgenographic film density and clinical diagnosis. A preliminary report. Oral Surg 15:1089 Sept 1962. 15. Richards, A.G. Technical factors that control radiographic density. Dent Clin North Am July 1961, p 371. 16. Carr, J.D., and Norman, R.D. Effective use of the dark room. Dent Clin North Am July 1961, p 363. 17. Cowan, L. Processing pitfalls in radiodontics. J Ontario Dent Assoc 40:15 April 1963. 18. Hunt, S. The processing of dental X-ray film. Dent Pract Dent Rec 22:113 Dec 1971.
Brown—others: DEGRADATION OF RADIOGRAPHIC SOLUTIONS ■ 1205
d e n ta l p r o f e s s io n
depends
on
r a d io g r a p h s
in p r o v id in g p a t ie n t s w it h o r a l h e a lt h c a r e o f th e
C ecil E. Brown, Jr., DDS Robin J. Winkworth, LDS, RCS
h ig h e s t
sta n d a rd s.
F o r
p la n n in g ,
it
is
im p e r a t iv e
O rville V. Anderson
g ra p h s b e p ro d u ce d
Albert C. Jerm an , DDS, Brooks Air Force Base,
t h e p a t ie n t .
Tex
M uch sa fe , u se .
The activity of radiographic processing solutions was m onitored by densitometry readings in this study to determ ine the number of satisfactory ra diographs that could be produced before degrada tion of the solution occurred. In 86 processing sessions, 7,890 fu lly exposed radiographs and 199 control radiographs were processed. Degradation was first noticed at the 74th processing session when 6,965 radiographs had been processed, but even at the end of the study, the radiographs pro cessed in the solution were of an acceptable qual ity.
in t e r p r e t iv e
e x a m in a
t io n s , f o r a d e q u a t e d ia g n o s is , a n d f o r tre a tm e n t
be
has
been
r e lia b le
r e g u la t e d
done
o u tp u t
to
th e
q u a lit y
d e v e lo p
th a t
and
e n su re
a n d h ig h -s p e e d f ilm r a d ia t io n
to
e q u ip m e n t
R a d ia t io n
th a t
r a d io
w it h m in im a l ir r a d ia t io n o f
is
e le c t r ic
p ro p e r
t im e r s
f ilm
h a s re d u ce d
p a t ie n t r e c e iv e s .
r e la t iv e ly
c o n v e n ie n t
to can
e xp o su re ,
th e a m o u n t o f
Th ese
im p r o v e
m e n ts a r e r e a s s u r in g ; h o w e v e r , w it h o u t q u a lit y c o n tro l
in
gra p h s
can
f ilm
p r o c e s s in g ,
r e s u lt .
in g t e c h n iq u e s a r e r e c o g n iz e d le m
in
t h is p h a s e
c e s s e d f ilm p a t ie n t a n d
in a d e q u a t e
In c o n s is t e n c ie s
in
r a d io
p ro ce ss
a s a m a jo r p r o b
o f d e n t is t r y . Im p r o p e r ly p r o
o ft e n n e c e s s it a t e s r e e x p o s u r e o f th e m ay
a ls o
le a d
to
in c o r r e c t d ia g n o
s is . A u t o m a t ic p r o c e s s in g u n it s a r e n o w a v a ila b le th a t
re d u ce
som e
of
th e
p r o b le m s ;
h o w e v e r,
h a n d p r o c e s s in g is s t ill u s e d in m a n y d e n t a l o f f ic e s . I n is
1200 ■ JADA, Vol. 87, November 1973
th e
e it h e r in s t a n c e , th e d e v e lo p in g p r o c e s s
sam e, an d
th e fin a l p r o d u c t d e p e n d s
on
Fig 1 ■ Aluminum step wedge designed for periapical radiographs: (1) step wedge; (2) periapical radiographic film packet; (3) pressboard packet stabilizer; (4) lead insert. the meticulousness of each phase. Much has been written on darkroom tech niques and equipment.1' 18 Procedures in timetemperature techniques, proper lighting, and methods for handling film have been well estab lished. One area o f radiographic processing that has not been adequately covered is the life of the processing solution.
D e ve lo p in g p ro cess and s o lu tio n d e g ra d a tio n The developing process, a complicated chem ical procedure, has been covered well in the lit erature. Radiographic films are coated with an emulsion impregnated with silver halide crys tals. These crystals are sensitive to X rays or light and form an invisible latent image when exposed. The developing process chemically converts the invisible latent image into a visible image. Reducing agents in the developing solu tion, such as Elon and hydroquinone, convert the exposed silver halide crystals into black me tallic silver that forms the visible image. The fixer contains a clearing agent, sodium or ammonium thiosulfate, that dissolves and re moves the undeveloped silver halides from the emulsion. The process o f conversion of the exposed film into a developed radiograph causes a chemical exhaustion or degradation o f the processing so lution. According to Fuchs,1 the degradation of the solution is affected by the number o f films
processed and their densities, the rate of oxida tion, contamination, and the accumulation o f by-products of the developing reactions. H ow ever, the number o f films that can be processed and the rate at which oxidation and other detri mental actions occur before the quality o f radio graphs is affected are not clear. I f this informa tion is obtained, it can be used to maintain high quality in the processing of radiographs. In this study, the longevity of dental radiographic processing solutions was investigated in order to establish a method o f quality control in processing dental radiographs.
M e th o d s and m a te ria ls A series of periapical films was developed under controlled conditions. A controlled method of determining density and contrast by densitome try readings was adapted for dental radiographic equipment. The activity of the processing solu tion was monitored daily throughout the experi ment. A radiographic step wedge was construct ed for standard periapical film (Fig 1) and was used to produce control radiographs. Steps were designed to provide an image of six densities, an ideal range of contrast for this study (Fig 2). The lead plate insert was used to produce the lowest density. Periapical film packets could be stabilized against the base of the step wedge; this ensured against distortions in images because of discrepancies in object-film distances. A standard dental radiographic unit* that had Brown—others: DEGRADATION OF RADIOGRAPHIC SOLUTIONS ■ 1201
Fig 2 ■ Periapical radiograph produced from step wedge. Num bers have been inserted for identification of densities.
previously been standardized for timing, radia tion output, and meter accuracy was used to ex pose the control film . A ll exposures were made at about the same time of day in an effort to avoid voltage discrepancies. Exposures o f 0.6 second at 90 kv and 10 ma with a target-film distance of 14 inches were used to produce the control ra diographs. A calibrated densimetert was used for all readings. The step wedge was set on a marked platform so that it would be in the same position for each exposure. The radiographic unit was placed in position with the tube head at 90°. Its location was marked on the platform so that it could also be repositioned (Fig 3). A ll processing was done in a thermostatically controlled developing unit.$ Each tank accom modated 5 gal o f processing solution. The unit was located in a conventional darkroom that had been thoroughly inspected for light leaks, cleanliness, and safe light specifications. Before the formal investigation, the darkroom procedures o f the two investigators were stan dardized; they performed all processing using the following technique. The tanks were thor oughly cleaned, and the solutions (Kodak liq uid radiograph developer and replenisher, and fixer and replenished) were mixed using distilled water according to manufacturer’ s instructions. The solutions were stirred with separate stirring rods to prevent contamination. The tempera tures o f the solutions and water bath were ad justed to the optimum of 68 F. A laboratory mer cury thermometer was used. (Among the four available float type of darkroom thermometers, there was a difference of four degrees in read ings.) Films were immersed in the developing 1202 ■ JADA, Vol. 87, November 1973
Fig 3 ■ Top, view of step wedge and radiographic unit. Note location markers on platform. Bottom, radiographic unit and step wedge in position. solution for 4.5 minutes. Initially, the hangers were agitated for eight seconds by drawing them slowly in and out of the solution to ensure full surface coverage and to eliminate air bubbles. Subsequently, agitation was performed by rais ing the hangers out o f the solution for eight sec onds every 60 seconds to remove by-products from the film surface. This permitted fresh chem
w e re
s t e p -w e d g e c o n t r o l r a d io g r a p h s a n d 5 0 f u lly e x
r in s e d f o r e ig h t s e c o n d s , t h e n t r a n s f e r r e d to t h e
p o s e d d e g r a d a t io n r a d io g r a p h s w e r e p r o c e s s e d .
ic a ls
to
c o n t in u e
d e v e lo p m e n t . T h e
f ilm s
f i x i n g b a t h w h e r e t h e y r e m a in e d f o r e ig h t m in
T h e m e a n v a lu e s o f d e n s it o m e t r y r e a d in g s w e r e
u t e s . T h e y w e r e t h e n w a s h e d f o r 2 5 m in u t e s a n d
re co rd e d
d r ie d f o r 2 5 m in u t e s . A
s o lu t io n
a c t iv it y
w as
o m e try
r e a d in g s ,
and
sto p w a tc h w a s u se d fo r
t im in g . F u lly a p ic a l
e xp o sed
p e r ia p ic a l f ilm s
U lt r a - S p e e d
D e n ta l
o n th e c o n tro l g ra p h . N o o b se rve d a
d e cre a se
on
r e la t iv e ly
th e
in
d e n s it
s t r a ig h t
lin e
(K o d a k
P e r i
w a s p r o d u c e d o n th e g r a p h . T h is in d ic a t e d th a t
F ilm ,
P o ly -
th e p r o c e s s in g a n d e x p o s u r e p r o c e d u r e s f o r th e
X -ra y
s o ft p a c k e t § ) w e r e u s e d to d e g r a d e t h e s o lu t io n s .
c o n tro l
E x p o s u r e s w e r e m a d e b y p la c e m e n t o f th e f ilm
th e re
r a d io g r a p h s
w as
no
w e re
d e t e c t a b le
c o n s is t e n t ,
and
th a t
d e g r a d a t io n
of
s o lu
o n a w h it e t o w e l, w it h t h e m a r k e r n o t c h f a c in g
t io n s d u r in g t h a t p e r io d . I t
up.
f o r e , to in c r e a s e th e n u m b e r o f d e g r a d a t io n f ilm s
A n
o ve rh e a d
6 0 -w
in c a n d e s c e n t
b u lb
w as
p ro c e s s e d to
illu m in a t e d f o r o n e m in u t e .
N o
A t
Experim ental procedure
100 a t e a c h p r o c e s s in g s e s s io n .
m e a s u r a b le
d e te cte d
at
th a t
w a s d e c id e d , t h e r e
th e
t im e ,
lo s s
in
s o lu t io n
3 0 -se c o n d
2 ,7 0 0
f u lly
a c t iv it y
p r o c e s s in g e xp o sed
w as
s e s s io n .
d e g r a d a t io n
r a d io g r a p h s a n d 6 9 c o n t r o l r a d io g r a p h s h a d b e e n p r o c e s s e d . T h u s , th e n u m b e r o f th e o r ig in a l c o n
N in e t y
c o n s e c u t iv e
exp o sed
c o n tro l
w it h u s e o f th e
r a d io g r a p h s
ste p
4 Vi m o n t h s .
In
p le t e t h e
w e d g e . S o lu t io n s
w e r e d e g ra d e d in 8 6 s e p a ra te d a r k r o o m d u r in g
t r o l r a d io g r a p h s (9 0 ) w a s n o t s u f f ic ie n t to c o m
w e re
each
s e s s io n
n u m b e r o f c o n t r o l a n d d e g r a d a t io n
s e s s io n s a
expo sed
c e r t a in
r a d io g r a p h s
c e r t a in w it h
w e re p ro ce sse d . P r o c e s s in g p r o c e d u r e s w e re
sta rte d 48 h o u rs
a ft e r th e s o lu t io n s w e r e m ix e d . I n s io n , f iv e
ste p -w e d g e
in v e s t ig a t io n .
T h e re fo re ,
tw o
co n tro l if
no
th e
r a d io g r a p h s
e x p e r im e n t
e ffe c t
on
w e re
c o u ld
used
be
s t a n d a r d iz a t io n ,
u s in g
th e f ir s t s e s
o n ly d if fe r
e x p o s e d a n d f r e s h ly e x p o s e d r a d io g r a p h s . A f t e r th e 4 3 rd d a rk ro o m
b y f r e s h s o lu t io n s f o r e a c h o f th e s ix s te p s , a n d
c o n t r o l r a d io g r a p h s w e r e u s e d . B e c a u s e
d e n s it o m e t r y
um e
o b t a in e d
as
e n c e in d e n s it ie s w a s o b s e r v e d b e t w e e n t h e p r e
p r o c e s s e d to e s t a b lis h t h e b a s e lin e a s p r o d u c e d
w e re
to
c o n t in u e d ,
f r e s h ly e x p o s e d c o n t r o l r a d io g r a p h s . N o
c o n t r o l r a d io g r a p h s w e re
r e a d in g s
o r ig in a l
p r e e x p o s e d c o n t r o l r a d io g r a p h s a n d t w o f r e s h ly
fo r each .
lo s s ,
th e
s e s s io n , o n ly f r e s h ly e x p o s e d
u p p e r p o r t io n
o f th e
o f v o l
p r o c e s s in g
T h e f iv e v a lu e s f o r e a c h o f th e s te p s w e r e a v e r
h a n g e r s w a s n o t b e in g c o v e r e d b y t h e d e v e lo p
a g e d , a n d t h e m e a n v a lu e s w e r e p lo t t e d o n a c o n
in g
tro l g ra p h .
u s e d to k e e p
(W it h in
each
ste p
le v e l,
th e re
w as
th e
next
n in e
d a rk ro o m
f u lly
s e s s io n s ,
m o re
h a n g e rs
w e re
th e r a d io g r a p h s b e n e a t h th e s o lu
D u r in g t h e t o t a l 8 6 p r o c e s s in g p e r io d s , 7 ,8 9 0
d u r in g th e f ir s t s e s s io n , 5 0
d e g r a d a t io n r a d io g r a p h s w e r e p r o c e s s e d . F o r
P r o g r e s s iv e ly
t io n .
s lig h t d if fe r e n c e in t h e f iv e v a lu e s u s e d to e s t a b lis h a c o n t r o l.) A l s o
s o lu t io n .
e xp o sed
d e g r a d a t io n
r a d io g r a p h s
and
199
c o n t r o l r a d io g r a p h s w e r e p r o c e s s e d .
tw o
NUMBER OF PERIAPICAL RADIOGRAPHS PROCESSED+ CONTROLS 250 500 1000 1500 2000 2500 3000 3500 3800 4400 4900 5390 5890 6390 6790 7390 7890 +
+
+
20
+
+
+
40
+
+
+
+
60
+
80
+
+
+ +
100
+
¡3 0
+
T5T
TIME ELAPSED (DAYS)
Fig 4 ■ Graph shows density value of control radiographs for duration of investigation. Numbers on hori zontal lines correspond to densities in Figure 2. Brown—others: DEGRADATION OF RADIOGRAPHIC SOLUTIONS ■ 1203
R e sults Figure 4 illustrates the mean densitometry read ings charted for each processing period. The density units represent the common log o f opac ity of the developed silver. Lines one through six represent the respective step densities on the control radiograph (Fig 2); the vertical distance between each line indicates the contrast between each step. Figure 4 shows that the densities o f all steps remained relatively constant until the 74th pro cessing session. A t that point, 6,790 fully ex posed degradation radiographs and 175 control radiographs had been processed. The density of step six began to drop noticeably on the graph; however, the decrease was not yet visible. The decrease in density was the first indication that the activity of the solutions was beginning to weaken enough to affect the darker areas of radiographs. Densities not only decreased but the contrast between each step decreased, as indicated by the narrowing o f the space between each line on the graph. This was also evident on visual inspection. When a density dropped from its level to the level o f the next density, it could be seen visually; that is, when step five dropped from a reading o f 1.43 to a level o f 0.88 (which was the original reading for step four), these steps could be matched visually (Fig 5). Figure 6 represents the reproducibility of densitometry readings per processing time for each level o f the step wedge.
D iscu ssio n By following strict procedures, we processed a far greater number of periapical radiographs be fore degradation occurred than we had antici pated. Because of the drop in densities, degrada tion was considered to begin at the 74th process ing session. A t this time, 6,965 radiographs had been processed. By the end of the investigation at the 86th processing session, 8,089 periapical radiographs had been processed. Even at this point clinical radiographs processed in the solu tions were acceptable; however, this was sub jective, and no attempt was made to establish at what point radiographs become unacceptable. Theoretically, the fully exposed films used for degradation purposes were equivalent to a great er number o f clinical films. Because fully ex1204 ■ JADA, Vol. 87, November 1973
Fig 5 ■ Visual shift in densities of control radiographs after degradation occurred. Top radiograph was processed during first processing period; bottom radiograph was processed dur ing 79th processing period. STEPWEDGE STANDARD LEVEL____________ DEVIATION
MAXIMUM DIFFERENCE
l
.0 0 4 3 1
.0 2
2
.0 0 9 4 6
.0 5
3
.0 1 4 0 5
.0 7
4
.0 1 8 3 8
.0 9
5
.0 3 2 5 0
.1 7
6
.0 6 3 8 4
.2 8
Fig 6 ■ Standard deviation of reproducibility of densitometry readings pooled over all processing times for each step wedge level. Degrees of freedom equal 88. Maximum difference is larg est difference observed between densitometer readings made at same processing time. posed films were used in degrading the solu tions, more chemical activity was required to produce their total blackness; that is, the amount o f silver halides that had to be converted to metal lic silver was greater than that needed in the pro cessing of clinical radiographs. Oxidation was not the problem that it was ex pected to be. Although the processing tanks were covered, they were not airtight. I f oxida tion did occur, the solutions were not affected for four months. The loss of developing solution was a prob lem. Additional hangers had to be used so that
f ilm
c o u ld b e s u b m e r g e d , a n d in a c lin ic a l s it u a
t io n
t h is
w o u ld
be
im p r a c t ic a l.
R e p le n is h m e n t
s e e m s n e c e s s a r y to m a in t a in s o lu t io n le v e l r a th e r
and television branch, support services division at Brooks Air Force Base. Dr. Jerman, a lieutenant colonel, USAF DC, is chief, experimental dentistry function, dental sciences branch, clinical sciences division, Brooks Air Force Base.
t h a n c h e m ic a l a c t iv it y . S t a t is t ic a lly , t h e m e t h o d u s e d in t h is in v e s t ig a t io n w a s v a lid , a n d t h e f in d in g s h a v e b e e n w e ll s u p p o r t e d b y a d d it io n a l in v e s t ig a t io n .
Sum m ary D e g r a d a t io n
o f d e n ta l
r a d io g r a p h ic
p r o c e s s in g
s o lu t io n w a s c a r r ie d o u t in a c o n t r o lle d p r o t o c o l, a n d th e a c t iv it y
o f th e
s o lu t io n s w a s m e a s u r e d
b y d e n s it o m e t r y r e a d in g s . D u r in g f o u r m o n t h s , 6 ,7 9 0 f u l l y 175
e xp o sed
p e r ia p ic a l r a d io g r a p h s
c o n t r o l r a d io g r a p h s w e r e
d e g r a d a t io n ta n k
p ro ce sse d
and
b e fo re
o f t h e c o n t r o ls w a s d e t e c t e d . E a c h
a cco m m o d a te d
5
U S
g a l.
In
v ie w
o f th e
n u m b e r o f r a d io g r a p h s p r o c e s s e d a n d t h e le n g t h o f th e e x p e r im e n t , d e n t a l r a d io g r a p h ic p r o c e s s in g
s o lu t io n s s e e m
m o re
r a d io g r a p h s
to b e o f
c a p a b le
s a t is f a c t o r y
o f p r o c e s s in g q u a lit y
h a d b e e n a n t ic ip a t e d . A l s o , o x id a t io n be
le s s
o f
a
p r o b le m
under
th a n
s e e m s to
c o n t r o lle d
c o n d i
t io n s t h a n it w a s p r e v i o u s ly e x p e c t e d t o b e .
The research reported in this paper was conducted by person nel of the dental sciences branch, clinical sciences division, USAF School of Aerospace Medicine, Aerospace Medical Divi sion, Air Force Systems Command, US Air Force, Brooks AFB, Tex. Further reproduction is authorized to satisfy the needs of the US government. Dr. Brown, a lieutenant colonel, USAF DC, is chief of dental consultation, dental sciences branch, clinical sciences division, US Air Force School of Aerospace Medicine, Brooks Air Force Base, Tex, 78235. Dr. Winkworth, a squadron leader in the Royal Air Force, is an exchange dental officer in the dental sciences branch. Mr. Anderson is medical photographer, photography
* Model GE90-11-11AA2-2, General Electric Co., Milwaukee. t MacBeth transmission densitometer, model TD102. MacBeth Corp., Newburgh, NY. t Bar-Ray developing unit, model B-2440. Bar-Ray Products, Inc., Brooklyn, NY. § Eastman Kodak Co., Rochester, NY. 1. Fuchs, A.W. Principles of radiographic exposure and pro cessing, ed 2. Springfield, III, CharlesCThomas, 1958, p233. 2. Wainwright, W.W., and Villanyi, A.A. The simplest radiographic analyzer: the X-ray checker. J S Calif State Dent Assoc 28:122 April 1960. 3. Lozier, M. Significance of correct processing in intraoral roentgenography. I. Oral Surg 3:911 July 1950. 4. Lozier, M. Significance of correct processing in intraoral roentgenography. II. Oral Surg 3:1060 Aug 1950. 5. Sweet, A.P.S. X-ray processing solutions. Dent Radiog Photog 28:27 No. 2, 1955. 6. Stewart, J.L., and Drisko, R.R. An evaluation of rapid x-ray film processing solution. Oral Surg 22:334 Sept 1966. 7. Morrow, W.H. Processing of dental radiographs. Br Dent J 122:395 May 2, 1967. 8. Smith, N.J.D. The sensitometric evaluation of dental radiographic film. Br Dent J 129:455 Nov 17, 1970. 9. Webber, R.L., and Ryge, G. The significance of exposure parameters in dental radiography. Oral Surg 27:740 June 1969. 10. Feldman, M.L., and Bozen, S. Automatic processing of periapical film. Oral Surg 26:647 Nov 1968. 11. Pentel, L., and Hyman, M. A method of assaying x-ray de veloper activity. Oral Surg 24:777 Dec 1967. 12. Reid, J.A. Improved exposure and processing techniques in dental radiology. J Can Dent Assoc 33:474 Sept 1967. 13. Wuehrman, A.H.; Manson-Hing, L.R.; and Jamison, H.C. X-radiation in dental offices in Jefferson County, Alabama. II. Darkroom facilities and processing techniques. Oral Surg 16:1450 Dec 1963. 14. Degerlng, C.l. Dental roentgenographic film density and clinical diagnosis. A preliminary report. Oral Surg 15:1089 Sept 1962. 15. Richards, A.G. Technical factors that control radiographic density. Dent Clin North Am July 1961, p 371. 16. Carr, J.D., and Norman, R.D. Effective use of the dark room. Dent Clin North Am July 1961, p 363. 17. Cowan, L. Processing pitfalls in radiodontics. J Ontario Dent Assoc 40:15 April 1963. 18. Hunt, S. The processing of dental X-ray film. Dent Pract Dent Rec 22:113 Dec 1971.
Brown—others: DEGRADATION OF RADIOGRAPHIC SOLUTIONS ■ 1205