COMMON CAUSES OF ERRORS

The radiograph certainly plays a very important ro- le in diagnosing certain pathological conditions, and the instruments presently available can assure excel- lent quality. On the other hand, a poor quality radio- graph can give erroneous information, simulating the presence of pathologies that do not in fact exist or hi- ding their presence from the viewer.

Therefore, to avoid errors of radiographic interpre- tation, the dentist must be familiar with some basic dark room rules, in addition to the rules of geometric projection that regulate image formation on the radio- graphic film.

Insufficient knowledge of these rules leads to waste of time and materials, film, and fluids, but especially in- creases the patient’s radiation exposure in the attempt to obtain a flawless film.

Because a colleague or the patient himself may re- quest the radiograph, it must be not only presentable and legible, but absolutely perfect. Radiographs must be considered visiting cards of the dental office! The following are the most common causes of er- rors.26,38,39,50

1) Light radiographs (Fig. 5.72)

A) Exposure errors (underexposed film)

a) Insufficient milliamperage (when adjustable) b) Insufficient kilovoltage (when adjustable) c) Insufficient exposure time

d) Excessive film-to-radiographic source distan- ce

e) Film packet reversed in the mouth (with the lead facing the teeth) (Fig. 5.73)

f) Use of expired film

B) Processing errors

a) Underdeveloped film because of – bath temperature too low – development time too short – broken dark room thermometer

b) Dilute or contaminated developing solution c) Exhausted developing solution

d) Prolonged immersion in the fixing bath

2) Dark radiographs (Fig. 5.74)

A) Exposure errors (overexposed film)

a) Excessive milliamperage (when adjustable) b) Excessive kilovoltage (when adjustable) c) Excessive exposure time

d) Film-to-radiographic source distance too short

B) Processing errors

a) Overdeveloped film because of

– too high bath temperature (dark or large- grained film) (Fig. 5.75)

– prolonged development time b) Developing solution too concentrated c) Too brief immersion in the fixing bath d) Accidental light exposure

e) Inadequate red light in the dark room f) Filtration of light through the doors or win-

dows of the dark room

Fig. 5.72. Light radiograph.

B A

Fig. 5.74. Dark radiograph.

Fig. 5.76. Radiograph with too little contrast. Fig. 5.75. Dark, grainy radiograph.

Fig. 5.77. Fingerprints on the radiograph.

c) Film contaminated by developer before treat- ment (Fig. 5.79)

d) Excessive folding of the film (Fig. 5.80)

5) Light stains

a) Film contaminated by the fixer before treatment (Fig. 5.81)

Fig. 5.78. The radiograph had been partially in contact with another film du- ring fixation.

112 Endodontics 5 - Endodontic Radiography 113

b) Film in contact with the basin or with another film during development (Fig. 5.82)

c) Name of the patient written on the wrapper be- fore treatment in the dark room (Fig. 5.83) d) Scratches on the film (Fig. 5.84)

6) Yellow or Brown stains

a) Exhausted developing solution b) Exhausted fixer

c) Contaminated solution

d) Insufficient washing of the film before drying and filing (Fig. 5.46)

7) Blurry radiographs (Fig.5.85)

a) Patient movement

b) Movement of the X-ray machine

c) Double exposure

8) Radiographs with partial images

a) Film not immersed completely in the develo- ping solution (Fig. 5.86)

b) Poor alignment of the long cone (Fig. 5.87) It is advisable to have an adequate supply of film in the office, without overstocking, so that one is not left with an enormous stock of expired film.

If there are several packages, open and use those that expire soonest.

The films must be kept in the refrigerator, far from hot or humid environments, but particularly from ra- diation. For the ideal developing and fixing times, see Table III.

Fig. 5.79. A finger contaminated with developer has touched the film in the

dark room prior to treatment. Fig. 5.80. The dark line that simulates a vertical fracture of the lower right cen-tral incisor, as well as a mandibular fracture, is in fact due to excessive bending of the film prior to its positioning in the mouth.

Fig. 5.81. The clip with which the radiograph was immersed in the developer was contaminated with fixer, because it had not been adequately washed.

Fig. 5.82. The radiograph had been partially in contact with another film du- ring development.

Table III

Times recommended for Ultrarapid film, 65 kilovolts, 7.5 mA, developing bath at 25° C, with constant agitation of the immersed film.

Development 20” Rinse 2” Fixing 3”

}

dark room

Fixing 15’

Washing 20’

}

Fig. 5.83. The name of the patient was written with a ball-point pen on the film

wrapper before processing. Fig. 5.84. The film has been “rinsed” in a basin containing other films, as well as more clips!

Fig. 5.85. Blurred radiograph caused by movement during exposure. Fig. 5.86. The film has not been completely immersed in the developer.

Fig. 5.87. The X-ray tube head was misaligned. This error can confirm that the X-ray beam is well collimated!

114 Endodontics 5 - Endodontic Radiography 115

Note that the film needs never be completely fixed so as to be read in ambient light. Immersion in the fixer for a few seconds suffices, and the film can then be removed from the dark room and read by incident light (Fig. 5.88). The film must then be reimmersed in the fixer, where it remains for about 15 minutes. It can then be removed after 10 to 20 seconds to be read by light transmission (Fig. 5.89). A good reader of radiographs eliminates the circumambient light, which can be achieved with a simple visor (Fig. 5.90) and the use of an adequate magnifying lens (Fig. 5.91).

If one takes into consideration the time required to close the dark room door, open the radiographic film wrapper, immerse the film in the baths, reopen the dark room door, and exit, it is clear that it should take

no more than 40 to 50 seconds before a film can be examined.

If “rapid” developing and fixing solutions are used (Fig. 5.92), this time can be halved. The importance of reducing the developing time is obvious, especially in the case of intraoperative radiographs; in this situa- tion, it is important to eliminate delays, and one need not wait for the radiographs to dry.

If, on the other hand, one can wait longer and needs a dry radiograph to give to a colleague or patient, one can use an automatic developer (Fig. 5.93) which in a few minutes (more or less, depending on the manu- facturer) produce dry radiographs.

A very important but unfortunately frequently over- looked phase is that of washing. The quality of film

Fig. 5.88. Although barely immersed in the fixer and removed from the dark room, the radiograph can be read by incident light. It is illuminated from abo- ve by the lamp of the unit or a light on the cabinet.

Fig. 5.89. After the radiograph has been properly fixed, it can be read by tran- smitted light on a light box.

Fig. 5.90. Prof. Langeland uses a visor to eliminate ambient light. Fig. 5.91. Interpretation of radiographs is facilitated by enlargement (Designs for Vision, 2.5x) and the elimination of surrounding light (shielding of the li- ght box).

of the dentist of the techniques of stomatological radiology, so as to obtain consistently well-orien- ted and correctly exposed and developed radio- graphs, so that the maximal diagnostic information can be drawn from them.

B) The dentist must never hold the radiographs in the patient’s mouth, placing his/her hands in the path of the primary X-ray beam. In the past, various types of damage to the fingers have been described, ranging from simple dystrophic changes to cancerous lesions. The radiograph must be kept in the mouth by the patient himself. If the patient cannot (e.g., in the case of children, elderly patients with Parkinson’s disease, etc.), then an adult companion with no professional radiation exposure must keep it in place.26

C) Numerous studies indicate that, at parity of kilo- voltage, the patient’s exposure with the use of the long cone and the paralleling technique is much less than that which occurs with the use of the short cone and the bisecting angle technique.35 D) The use of high kilovoltage is recommended. The

X-ray machine must also have good overall shiel- ding, a good centerer of the beam, which must be filtered and collimated, so that its diameter is between 6 and 7 centimeters (Fig. 5.94).

E) The X-ray machine switch must be fitted with an alarm that emits sound and light to indicate the precise moment and length of execution of a ra- diograph.35 _{The switch must also be provided with} an extension cord so that the operator can stand at least 2 meters from the tube. This is the minimum distance for protection against the primary X-ray beam as well as the secondary beams that form (by

Fig. 5.92. Rapid developing and fixing solutions. Fig. 5.93. The Dürr automatic developer, which is essential whenever dry radio- graphs are needed immediately.

preservation depends on this step, which can reduce yellowing with time. The films must therefore always be rinsed for 20 minutes in running water.

PROTECTION OF THE PATIENT, DENTIST, AND