Buscando una perspectiva desde dónde percibir y actuar

In dentistry, the basic principle of protection from io- nizing radiation is to reduce as much as possible the radiation exposure of the patient and then of the staff, without of course denying the dentist the desired be- nefits of diagnostic radiography.26

The decision whether or not to obtain a radiograph must be based on a risk-benefit assessment. The pa- tient should be exposed to radiation only when the benefits outweigh the risk.51

It is important to emphasize to the patients that it is more likely that they will sustain an injury for having refused a clinically important radiograph as compared to the remote possibility that they will develop any di- seases as a result of exposure to ionizing radiation. Studies on the doses of radiation absorbed by the bo- ne marrow from taking dental radiographs have de- monstrated that the radiation absorbed in a complete oral examination including 21 endoral radiographs is equivalent to that of a 65-day exposure to natural io- nizing radiation (cosmic, from terrestrial or non-terre- strial sources).26,59

Nonetheless, even if the biological damage conse- quent to radiation exposure in a dental practice is mi- nimal,13 _{it must not be overlooked.}

The principal methods of protection are as follows: A) Fundamentally, a thorough familiarity on the part

116 Endodontics 5 - Endodontic Radiography 117

the Compton effect) from radiation scattered from the patient, the floor, the walls, or nearby objects. It is better still if the switch is located outside the

area in which the radiographs are taken. If this is not possible, the operator should wear a lead apron.

F) Where possible, it is always advisable to position the switch outside the treatment room. Floors, walls, and ceilings usually do not require additional shielding. If, however, the dividing walls are made of wood or other light materials, it is advisable to provide shielding with lead panels.

G) It is a good idea to use a timer to regulate the ma- ximum and minimum exposure times to standardi- ze the results. Adequately connected to a system of switches, the timer can control several X-ray ma- chines in different rooms. In this case, an expert electrician should perform the wiring, so that it is impossible to mistake the position of the switch and erroneously expose the dentist, patient, and auxiliary personnel to accidental or undesired ra- diation. The use of a switch fitted with interde- pendent satellites eliminates the risk of undesired exposure and adheres fully to the safety standards of the dental office 36 _{(Fig. 5.95).}

H) The patient must always be protected with a lead apron, which principally protects the gonads, and

a lead collar to protect the thyroid 58 _{(Fig. 5.96).} When radiographs are performed in the upper qua- drants, it is advisable to protect the crystalline lens with sunglasses to whose inner aspect at least 3 lead sheets obtained from radiograph wrappers ha- ve been attached (Fig. 5.97). Nonetheless, Danforth and Torabinejad 13 _{have demonstrated that one} would have to undergo at least 10,900 endoral ra- diographs to receive the threshold radiation dose required to produce cataracts.

Fig. 5.94. The diameter of the well collimated X-ray beam must not exceed 6-7 cm.

Fig. 5.95. This Philips timer (right) is used to automatically regulate the expo- sure time according to the teeth being treated. A switch (left) allows a single timer to control several X-ray machines in different rooms.

Fig. 5.96. The patient’s gonads and thyorid must always be protected by a lead apron.

I) In the case of pregnant patients, one should re- frain from obtaining radiographs. As Marci 34 _con- firms, “somatic damage to the embryo is due to maternal abdominal irradiation during pregnancy, which can cause abnormalities of variable severity and type, depending on the dose administered and the developmental age of the embryo. Limited use of dental radiology is necessary, as for other types of radiological studies, since, although the practi- ce of oral radiography carries a low risk of radia- tion exposure, it is also true that during the period in which the human species undergoes organoge- nesis (fifteenth to twenty-fourth days of gestation), even the administration of doses of only 35 Rem can cause malformations incompatible with life. In the subsequent phases of pregnancy, the sensitivity of the product of conception to the teratogenic ac- tion of X-rays progressively diminishes, and, at pa- rity of radiation dose absorbed, the percentage of malformations thus decreases”. According to Marci, to avoid damage caused by irradiation of the em- bryo, practitioners in many countries apply the “ten day” rule, which limits diagnostic radiation exposu- re to the ten days that follow the beginning of the menstrual cycle.

Although this procedure refers only to exposure of the pelvis to primary rays, it would be prudent to apply such limitations also in the dental practice, or else to take the appropriate precautions to protect the abdomen of a woman undergoing dental radio- graphs with the appropriate lead apron.

The concept of not performing even simple endo- ral radiographs in cases of presumed pregnancy is still valid, as there is no concrete information about

diation.

M) It is a good idea to use high speed radiographic film such as Kodak Ultraspeed or Ektaspeed (Fig. 5.98) which require exactly half the exposure ti- me than the earlier very sensitive films,14,16,20,25,30,31,51 so as to reduce the exposure time to a minimum, fractions of a second. The use of high sensitivity or high speed film requires a more precise exposu- re technique and suitable manipulation in the dark room. It must be kept in mind that although the Ektaspeed is safer for the patient due to the shor- ter exposure time required, on the other hand the Ultraspeed film is superior in terms of contrast and image quality.30

In 1994, Ektaspeed Plus dental X-ray film (Eastman Kodak, Rochester, NY) was introduced. Recent stu- dies 7,12,41 _{demonstrate that the use of Ektaspeed Plus} film for working length determination can reduce pa- tient radiation exposure by 50%, while producing a quality, diagnostic radiograph with good contrast and density. When compared to Ektaspeed, Ektaspeed Plus has a higher contrast, is less grainy and faster. When compared to Ultraspeed film, Ektaspeed Plus demonstrates that it is superior or equivalent and only

Fig. 5.97. Three lead sheets obtained from endoral radiographic film wrappers are glued to the inner surfaces of sun glasses. They are more efficacious in pro- tecting the patients’ crystalline lens.

Fig. 5.98. Ultra-Speed films and, even more, Ekta-Speed, are very rapid films that allow the use of considerably shorter exposure times.

118 Endodontics 5 - Endodontic Radiography 119

slightly more grainy. Considering the reduced radia- tion exposure required for Ektaspeed Plus (only half the time compared to Ultraspeed film), several authors

ERN, F.P.G.M., DOESBURG, W.H., LEMMENS, W.A.J.G.: Evaluation of a technique for standardized periapical radio- graphs. Oral Surg. 44:646, 1977.

16 FARMAN, A.G., MENDEL, R.W., VON FRAUNHOFER, J.A.: Ultraspeed versus ektaspeed X-ray film: Endodontists’ per- ceptions. J. Endod. 14:615, 1988.

17 FAVA, L.R.G., DUMMER, P.M.H.: Periapical radiographic te- chniques during endodontic diagnosis and treatment. Int. Endod. J. 30:250, 1997.

18 FITZGERALD, G.M.: Dental roentgenography. II. Vertical an- gulation, film placement and increased object-film distance. J.Am. Dent. Assoc. 34:160, 1947.

19 FITZGERALD, G.M.: Dental roentgenography. III. The roen- tgenographic periapical survey of the upper molar region. J. Am. Dent. Assoc. 38:293, 1949.

20 FLETCHER, J.C.: A comparison of ektaspeed and ultraspeed films using manual and automatic processing solutions. Oral Surg. 63:94, 1987.

21 FORSBERG, J.: Radiographic reproduction of endodontic “working length” comparing the paralleling and the bisec- ting-angle techniques. Oral Surg. 64:353, 1987.

22 FORSBERG, J.: A comparison of the paralleling and bisecting- angle radiographic techniques in endodontics. Int. Endod. J. 20:177, 1987.

23 FORSBERG, J.: Estimation of the root filling length with the paralleling and bisecting-angle techniques performed by un- dergraduate students. Int. Endod. J. 20:282, 1987.

24 FORSBERG, J., HALSE, A.: Radiographic simulation of a peria- pical lesion comparing the paralleling and bisecting-angle te- chniques. Int. Endod. J. 27:133, 1994.

25 GIRSCH, W.J., MATTESON, S.R., McKEE, M.N.: An evaluation of Kodak ektaspeed periapical film for use in endodontics. J. Endod. 9:282, 1983.

26 GOAZ, P.W., WHITE, S.C.: Oral radiology. Principles and in- terpretation. The C.V. Mosby Company. St. Louis, 1982. 27 GOERIG, A.C., NEAVERTH, E.J.: A simplified look at the buc-

cal object rule in endodontics. J. Endod. 13:570, 1987. 28 GROSSMAN, L.I.: A brief history of endodontics. J. Endod.

Special Issue, 8:S 36, 1982.

29 KHABBAZ, M.G., SEREFOGLOU, M.H.: The application of the buccal object rule for the determination of calcified root ca- nals. Int. Endod. J. 29:284, 1996.

suggest substituting Ultraspeed and Ektaspeed with Ektaspeed Plus film for intraoral imaging.12,41

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120 Endodontics 6 - Visiography Systems 121