Skull adapted for teaching roentgenographic technique

Oral roentgenology American

Arthur

Academy

of Oral

H. Wuehrmann,

Roentgenology

Editor

Skull adapted for teaching roentgenographic technique Douglas C. Ruhlman, Los Angeles, Galif.

D.M.D., ad

DFSARTMENT

DIAGNOSIS,

LOS

ANGELES,

OF ORAL SCHOOL

Frank M. Lucatorto,

USIVERSITY

OF CALIFORNIA

M.X., D.D.S., AT

OF DENTISTRY

T

caching aids in laboratory-technique courses are numerous and undergo constant refinements to meet the demands of a crowded curriculum. These refinements are directed toward effectively teaching the preclinical student skills and procedures with a minimum consumption of time, space, and manpower. Manikins and typodonts used in the teaching of principles in operative, crown and bridge, and anesthesiology courses usually augment didactic lectures which are followed by laboratory sessions where each student may develop his skills. In developing a preclinical course in oral roentgenology for a large class, four problems are recognized : 1. There are few, if any, effective laboratory methods for providing a simulated clinical situation. 2. The usual method of teaching oral roentgenology consists of a didactic course followed by clinical trial-and-error practice. 3. The ratio of x-ray machines to students is such that time consumption and cumbersome scheduling of the roentgenology area is required. 4. The amount of unnecessary radiation may be increased as a result of problems created in the learning situation. B’undamental techniques in the teaching of oral roentgenology may be facilitated without the use of radiation or expensive equipment. Scheman’ described a simple aid for teaching the principles of x-ray by using the analogy of light. Similar teaching aids and exercises may be in use but are difficult to find reported in the literature. 743

744

Ruhlnaan

and Lucntorto

O.S.,().!A L 0.1’. .I 1111v, I !lfifi

We have devised R teaching aid which WP believe accomplixhr~s th(> f’ollo\~i~~~ objectives : 1. The student can visualize directly t,he relationship of film placenrc:nt to tooth position. 2. The student can visualize directly the relation of horizontal and vertical positioning of cone and central beam to appreciate image distortion. 3. The student can visualize directly t,he effects of altering target-objcctfilm distances to improve image definition. 4. The student can visualize directly those anatomic structures which will be projected onto the film in two-dimensional form. 5. The student can learn to handle the materials and procedures involved in roentgenology techniques. MATERIALS AND METHODS The skull Fig. I shows a normal anatomic skull that can be obtained from various sources for approximately $25.00 to 50.00. On the maxilla and the opposite side of the mandible all boric st,ructure surrounding the roots and apices of the teeth is removed, with the exception of about l/b inch near the cervical portion of the crown. Essentially, this creates a window around the roots, extending from the midline to the tuberosity of the maxilla and from the midline to the ascending ramus of the mandible, and allows for transmission of light in a buccolingual direction. The skull is mounted on a standard laboratory manikin setup.

long

cone

simulator

This consists of a tube approximately 16 inches in length and 3 inches in dia,meter containing the working parts of a tensor light with a reflector. The device is shown in Fig. 2; its approximate cost is 20.00. The tube is attached, with a flexible U-joint, to a standard base for a fluorescent desk lamp. This gives movements simi1a.r to those of the head of an x-ray machine. The light within the tube is collimated, as in an x-ray machine, by a metal diaphragm to produce a desira.ble area of light at the end of the corm. The light within the tube and the diaphragm ca.n be moved up a,nd down within the cone. The light itself is turned on and off by a switch located at the base of the mount. A two-way switch provides two selections of light intensity. Application

The purpose of these materials is to provide a laboratory technique exercise which is similar to t.he actual clinical sibuation. Using any film-holding device, the student may be shown and then practice

Fig.

746

ECuhlnaun und Lucatorto

O.S.,ox & 0.1’. .Tnnr, 1966

proper film placement, regardless of whcthcr a right-angle or bisecting angle technique is being taught. With the roots exposed, the student can appreciate the relationship of the long axis of the tooth to the film. This is also true of other structures, such as the maxillary sinus, mandibular canal, incisive canal, etc. The student is next shown and allowed to practice t,he horizontal and vertical placement of the cone. Fig. 3 shows the film, skull, and cone in place. The exposed roots again help the student to visualize the proper orientation of the cone to the teeth and film. At this point the student may turn on the light. Immediately he is able to tell whether the target-object-film relationship is properly oriented. An image of the teeth is thrown on the film packet as if this film had been exposed to x-radiation (Figs. 4 and 5). The image shows very nicely the extent of coverage, cone rutting, open or closed conta.cts, periapical coverage, foreshortening, and elongation. The effects

Fig.

3

4

I)‘kull for

teaching

roentgellographic

technique

Fig.

747

5

of increasing target-object distance can also be shown by moving the light source up a,nd down within the tube. As the light source is moved further away within the cone, the image becomes sharper and dimensionally more accurate. At this point the student should have obtained a basis for film and cone placement, using one half of the skull. The other half of the skull can be used to introduce the exposing and developing of film. When the mounted skull is fixed to a dental chair next to an x-ray machine, the student may practice the principles that he has learned up to this point. These simula.ted conditions should provide the student with a good grasp of the principles of roentgenographic techniques. He should now be able to obtain satisfactory diagnostic films on a living patient with minimum time loss and without excessive use of ionizing radiation. He should also be better equipped to criticize the quality of his films. SUMMARY The purpose of the project described here was to develop a teaching aid for oral roentgenology. Windows were prepared in the maxilla and mandible of a skull so that a light source, represent.ing the focal spot of an x-ray machine, passing through the window would produce an image on a film packet which is positioned by means of standard film-holding devices. This teaching aid offers the following advantages : 1.. It serves as an intermediate step between classroom and clinic, reducing time consumption and unnecessary radiation during the trial-and-error period. 2. A concept of target-film-object relationship can be easily visualized. 3. This inexpensive laboratory teaching aid can be used in ot,her than rocntgenology courses. REFERENCE