Radiographic evaluation of defects created in mandibular condyles

dental radiology Editor: LINCOLN R. MANSON-HING, D.M.D., M.S. American Academy of Dental Radiology School of Dentistry, University 1919 Seventh Avenue South

of Alabama

Birmingham, Alabama 35233

Radiographic evaluation of defects created in mandibular condyles NivclEdo Gowxlzws, (‘.D., D.C.O., D.L., M.S.,‘% Alnn ill. LViller, D.D.S.,** Sey~)~o~~r H. Yule, D.D.S.,*;** NeTtry M. Rosenberg, D.D.S.,#+** alad J. DontrId Hn~Lptfuehre~,***** Chicago, 111. COLLEGE OF DENTISTRY,

UNIVERSITY

OF ILLINOIS AT THE MEDICAL CENTER

Twenty-four defects were created in mxndibular condyles. These were divided into two groups of twelve (small and large). Seven radiographic techniques were utilized, and their effectiveness in demonstrating these defects was evaluated. A variety of condyles was selected for evaluation with respect to size as well as horizontal and vertical angulation. The created defects varied greatly with respect to size and location. After examination of each of the created defects in the condyles with each of the radiographic techniques, the created defects were localized with silver amalgam and re-examined

with the radiographic techniques. The radiographs of each condyle mere compared for visualization of the defects. With all techniques used in this study, visualization of the smaller defects was very poor. The technique that scored the highest for visualization of all defects was corrected anterior-posterior laminagraphy.

M

any radiographic techniques for evaluating the temporomandibular joint have been described. (The term tenlporol)~andibular joint will here after be contracted TMJ.) Most of these techniques have been designed to eliminate physically anatomic structures which would normally obstruct adequate radiographic visualization of the joint. Few authors have given attention to the vari*Postdoctoral Student, Department of Radiology. **Assistant Professor, Department of Radiology. “**Dean and Professor of Radiology, College of Dentistry College of Medicine. “““*Professor and Head, Department of Radiology. **“**Principal Electronics Technician.

and Professor

of Radiology,

Volume 33 Number 3

Defects created in ?,rn~~dibulrrr condyles

475

ation in morphology and angulation of individual condyles so that not only a “good” radiograph but also an undistorted visualization of structure may be perceived. The review of the literature indicated that numerous techniques have been proposed for radiographic examination of the TMJ; however, most did not consider morphologic variations between condyles. The authors of many of these articles claimed that their techniques were the best, and this has contributed to cont.roversy. However, careful evaluation of the literature has made it apparent that each of the more popular techniques has serious limitations. Moreover, the assessment, of location and type of bony condyle alterations has often been subjective. The purposes of this study are (1) to identify which, if any, of the techniques are of value in consistent reproduction of visible images of defects created in the condyle and (2) to define the conditions under which these techniques are most reliable. The literature on the subject of TMJ radiography is quite extensive and redundant. Papers which exemplify treatment of the topic and appear representatire will be cited. Further, the techniques employed for this study, while limited to seven, exhibit nearly all the principles incorporated in all the techniques reported. REVIEW

OF THE LITERATURE

Altschul,l 1927, laid down several principles for radiography of the TMJ, and these principles are the basis of most current techniques : Avoid superimposition of other cranial structures, direct the x-ray beam perpendicular to the film cassette, and place part as near film as possible while maintaining correct orientation. In 1935 Gillis” stated ; “Since 1885-1890, the movements of the condyle of the mandible and its relative position in its fossa have been the subject of much study and more speculation.” In his report he proposed a technique, stating precise angles at which the rays enter the skull. However, he failed to describe the exact position of the head or the place of entry of the rays. The point of entry is situated approximately i/Z inch in front of the external auditory meatus and 2 inches above, and the angle of incidence of the rays is about 15 degrees downward. The sagittal plane is not parallel to the film. One year later, Lintlblom” presented his transcranial technique for the projection of the TMJ and severely criticized the Gillis technique, although he admitted superficial similarity to his own. There may have been incorrect observation by Lindblom, because the point of incidence of the central rays is different in the two techniques. In fact, in the Qillis technique, rays enter the skull in front of the external auditory meatus while in the Lindblom technique they enter behind it. Although the films presented by Gillis and Lindblom show some similarity, the orignal Lindblom transcranial technique defines the point of entry of the central ray as 20 mm. back of the external auditory meatus and 60 mm. above it. MeQueen,” claiming that previous techniques had met with only partial

476

Goncalves

et al.

Oral Surg. September,1974

success, described a lateral subcranial or transpharyngeal technique. He attempted not only to avoid the dense cranial structures surrounding the joint but also to minimize distortion while maximizing detail, contrast, and density. In defense of his lateral transcranial projection of the TMJ, Gilli@ countered Lindblom categorically : “This technique shows up temporomandibular joint dysfunction and we claim no priority among those who are pioneering in a new field of usefulness for dentistry.” While others described the use of laminagraphy for skull examination, Petrilli and Gurley6 were the first to propose the method for TMJ examination. They sympathize with the roentgenologist, stating: “. . . it must be admitted that from the radiographer’s viewpoint this region is one of the most complicated and the shadow areas are the most dense of the entire body that he is called on to examine.” While they recognize the advantages of laminagraphy, they suggest no specific technique. In 1943 Kurz’ developed a head holder, or small cephalostat, which he claimed would give results as satisfactory as those obtained by laminagraphy with a conventional x-ray machine. One year later, Goughs advocated laminagraphy as the only method of obtaining an undistorted lateral representation of the anatomy of the TMJ. In addition, he claimed the superiority of laminagraphy to demonstrate lesions not clearly shown by routine radiography. ZimmeP and, later, Franklo were the first to examine the TMJ from the frontal view. The latter suggested that examination be made with the patient’s mouth open, Using a 15-degree angle board, Updegravel’p I2 described the first technique in which slight variations in angle of observation can be made. Grewcock13, I4 presented his transcranial technique and stated that, properly executed, it could demonstrate the correct condyle/fossa relationship. This technique was not selected for this project because it appears quite similar to those of both Gillis and Updegrarel’g I2 and represents an average of the two. In 1954 Donovan’” supported the dependability of his headholder, developed in 1950, in reproducing results on successive occasions. He attached fine wires to the condyle, eminence, and fossa and radiographed the articulation. In his conclusion, he stated: “A well developed tracing is essential for accurate interpretation, and the usefulness of the temporomandibular joint roentgenograms depends far more on functional analysis in terms of reference positions than on static analysis of joint structure.” Lindblom16 attempted to relate the symptoms of TMJ (Costen’s) syndrome to the radiograph of the joint, using the technique that he proposed in 1936. In discussing his findings he indicated that diagnosis of disease of the TMJ could not be made by radiograph alone but must be correlated with physical examination as well as subjective findings. Brandrup-Wognsen,17 using a simple transcranial technique, complicated it by incorporating a plastic locating device and by requiring trigonometric computation to define direction of the beam. He admitted inaccuracy in the calculation, however, stating : “Since we are always working with the same degree of approximate accuracy, this is of no significance.”

Volume 38 Number 3

Defects created in mandibular

condyles

477

Berry and Hofmanls were the first to propose the use of cinefluorography for motion studies of the TMJ. McLeran and co-workers,l@also using cinefluorography, concluded that there was need for modifications and improvements to make this method more valuable. Considering the target-film distance, LawtherZo presented a new head positioner for TMJ roentgenography. He indicated that the target-film distance should be 68.5 inches. He claimed that this eliminated distortion and enlargement of the TMJ and permitted the use of anatomic structures and anthropometric landmarks outside the joint for reference points in measurements. The author claimed that the roentgenographic results obtained when this head positioner was used are of value in studying the normal articulations of the TMJ, in diagnosing TMJ disturbance, and in studying the joint of the same person during extended periods of treatment. It should be pointed out, however, that increase in distance alone, while it will reduce magnification, does not eliminate distortion. Panoramic radiography for examination of the TMJ was first proposed by Paaterozl in 1949; subsequently Updegrave,22 Ando, and Manson-Hing’* described different types of panoramic machines for TMJ visualization. Lindblomz5 stated that the articular fossa becomes more shallow with the process of aging and that this factor should also be considered in radiography of the TMJ. Since the angle of observation can alter apparent depth of fossa, one wonders if his observation is valid. However, studies by Yale and associates26-2g have shown that condylar morphology is highly variable. While there is a high incidence of bilateral symmetry of condylar type, there is a low incidence of symmetry of combined condylar angles. A technique of cephalometric laminagraphy was described in which these variations were taken into consideration. The results produced an excellent lateral projection of the condyle. The application of this specific technique to oral diagnosis was described by Rosenberg.30 Updegrave31 supported his technique as the most practical, stating that stereoscopy, laminagraphy, and cinefluorography are specialized techniques of examination of the TMJ which require sophisticated equipment usually found only in schools, hospitals, or research centers. He did not deny the superiority of the sophisticated techniques, Mazaheri and Biggerstaff 32 commented on several methods that are used to obtain roentgenographic information about joint structures. They stated : “The supplemental roentgenographic information without an over-all physical examination of the patient with temporomandibular joint symptoms may not be conclusive. Many joints which are troublesome to the patient may appear normal on roentgenographs at the time of examination. Conversely, joints that may appear abnormal may be asymptomatic to the patient.” In 1970 Morgan33 modified Updegrave’s’l, l2 technique by altering the 15 degree angle board. He did not recognize, however, the existence of a variety of condylar angles in developing his technique. Weinberg34 stated : “Many dentists feel that temporomandibular joint (TMJ) radiographs have little clinical value in diagnosis and treatment due to their inaccuracy and variability. This concept is based on the assumption that even

478

Goncalves

Table

Oral Surg.

et 01.

September,1974

I Condyle size (mm.) nna angulation (degrees) I

Condyle 1

2 3

N-L

A-P

measurement 20.0 19.4 18.6

measurement 8.2 8.6 8.4

18.5

22.0 23.2 19.8 19.4 17 5 1i2 15.5 15.0

7

8 9 10 11 12 Key to defect

Horizontal

angle 15 13 18

8.5

8.2 7.7 6.3 7.0 9.0 9.0 7.3 7.2

23 21 10 9 11 20

Vertical angle 9 11 -1 -3 14 17 -6 -12 19 17 6 7

Location

GSA

LSA cs

AC CSA MA

SLA MS AL L SL AM

location:

S = Superior. M = Medial. 1, = 1,atrra1.

A = Anterior. P = Posterior. C = Central. Table

I

I

II. Comparison

of exposure factors for various techniques

MoQtbeen” GilliS* Panoramic Kelly-Koett Kelly-Koett GE-3000 50 KVP 80 KVP 80 KVP Exnosure 8 Ma. 50 Ma. 50 Ma. r 20 sec. 0.6 sec. 0.6 sic. Screen blocker I 2 2 Diaohrazm 0.047 inch slit 6.4 cm. round 6.4 cm. round 18.5 cm. 18.5 cm. Co& length 7.6 cm. 11.0 cm. 11.0 cm. 4.1 cm. Cone diameter *Without rotary motion on adapted GE control panel. tWith an adapted GE control panel using 8 inch rotary motion of the cone and one screen Machine

under the most controlled conditions successive radiographs of the same joint will not produce identical or even similar results.” Klein and associates3” published a work about different radiographic techniques in T&Id examination and, in their summary, said: “The radiograph is an important aid in the diagnosis of the temporomandibular joint problems. A marked difference of opinion exists in the interpretation of radiographs produced by various techniques.” They concluded that “tomographs using the Polytome H provided evidence of condyle and glenoid fossa irregularities that were undetectable by the usual radiographs.” MATERIALS AND METHODS Dry skull material

Six dry skulls were sleeted from the collection of Asiatic Indian skulls in the Department of Radiology, University of Illinois College of Dentistry. The twelve condyles chosen appeared to be normal and represented a variety of sizes and axial orientations. Dimensions and angular positions (Table I) were recorded in

Volume 38 Number 3

Defects created in nlandibular

Defect

size (mm.)

D. Large

3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.5

3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0

CASP LAS ACS AC SACM AMS SLA MASP LCAS L

3.0

3.0

LS MAS

Up&grave

1

InfWiOT-SUpeTiOT*

Kelly-Koett 80 KVP 50 Ma. 0.6 sec. 2 6.4 cm. round 18.5 cm. 11.0 cm.

GE-100 65 KVP 10 Ma. 0.1 sec. None 4.5 cm. round None None blocker per film in a five-film

defects

M.&id lateral

Locatim

Depth

479

and location

B. Small defects Diameter

condyles

6.0 8.0 6.0 6.0

(

Inf ertir SUpeTiOT

Anterior

posterior

2: 6:0

20” 7.5 7.5 10.0 5.5

5.0 6.0 5.0 6.0 4.0 5.0 5.5 5.5 11.0 6.0

4.5 7.0 4.0 5.0 6.0 7.5 5.5

0.0 5.0

5.0 6.0

56::

CAPLt Kelly-Koett Kieffer 60 KVP 25 Ma. 2.0 sec. 1 per film 3.9 cm. round 18.5’ cm. 6.0 cm.

CLLt Kelly-Koett Kieff er 60 KVP 25 Ma. 2.0 sec. 1 per film 3.9 cm. round 18.5 cm. 6.0 cm.

cassette.

anticipation of the possible influence of these parameters on the visibility of the artifacts to be created. Axial lengths and anteroposterior thickness were measured with a vernier caliper and rounded to one decimal place. Horizontal and vertical condyle angles were determined via radiographs, as described later. Measurements were made with a protractor and recorded to the nearest degree. The maxillary and mandibular teeth were articulated and maintained in position with adhesive tape. The size of the TMJ space was approximated, and utility wax was fitted to the base of the articular fossa to fill the joint space SO that the condyles could be placed repeatedly in an identical position. Radiographic

techniques

Evaluation of the visibility of artifacts created in the twelve condyles was limited to seven selected techniques. The methods chosen are representative of groups of the very large number proposed in the literature. Radiographic factors and machine type are recorded in Table II. Panoramic radiography, known also as pantomoPanoramic techvziqne.22

480

Oral

Gomalues et al.

Surg.

September,1974

graphic, panographic, and “Panorex,” is curved-surface laminagraphy. The x-ray source and film are mored in a controlled and related manner, so as to make it appear that the dental structures stand alone without other structures being radiographically superimposed. Skulls were positioned to give the best image of mandibular condyles without regard to detail sharpness of the anterior teeth. The General Electric 3000 machine was used. Gillis fechwique. The Gillis technique?, x is representative of the family of la.teral transcranial projections. The central ray of the x-ray beam entered $‘z inch in front of and 2 inches above the ipsilateral external auditory meatus and was directed toward the contralateral TJIJ. 2blcQuee)r. techwique. The McQueen technique 4, 36 is a lateral subcranial or transpharyngeal projection. The central beam entered 3/4 inch in front of the external auditory mcatus and was directed toward the contralateral TMJ. T:‘pdegrat~e fechviqne.“, I2 A 15-degree angle board with an ear post perpendicular to the surface permits repetition of patient positions. Ear posts of varying lengths allow for a change of head position, since t,he other contact points are the zygoma and the angle of the mandible. The central ray is directed vertically toward the affected condyle, so that the point of entry is not constant. Interior-superior (subntextal ,vertez) fech+tique. In this technique the skull is positioned in the head holder so that the posterior borders of the rami remain parallel to the floor and perpendicular to the cassette. The central ray is directed parallel to and midway between posterior borders of the rami. Corrected nllferior-posterior lanzhtagrcrphy~ (CAPL). This techniquez9 utilized the horizont.al angle obtained from a preliminary inferior-superior x-ray film. The horizont,al angle is formed by the intersection of the transmeatal line and the extended condylar axis. The laminagraphic cut, is oriented perpendicular to the long axis of the condyle. The vertical angle used in the following technique is obtained from this projection. Corrected lnternl. lawklngraphy (CLL). This technique, presented by Yale,29 requires the horizontal angle obtained from the inferior-superior x-ray picture and the rertical angle obtained from the corrected anterior-posterior laminagraph. The intersection of transmeatal lines and long axis of condyle, as seen in the CAPI, view, defines the vertical angle. The vertical angle is positive when the medial pole of the condyle is directed superiorly, and the angle is negative when the medial pole of the condyle is directed inferiorly. Classification

The investigation was divided into five phases, with photographs and radiographs prepared during each. All condyles in each phase were photographed from four directions : superior, posterior, anterior, and lateral. Phase A was a photographic and radiographic record of the conditions and radiographic appearances of the condyles before alterations. Each succeeding *In April of 1962, the International Committee on Radiological the term tonzography to describe all types of section techniques.

Units

officially

adopted

Fig. 1. Pluses A through E, condyle 10. A, Control. B, Small defects. rind opaque alloy. I), Large defects. E, Large defects and opaque alloy.

C, Small

defects

482

Gomalves

III. Evaluation

Table

Defect

of small-defect BL

LocfitioR

/

Radiographic evaluation Panoramic Gillis McQueen Updegrave Inferior-superior CAPL CLL Total Key A = P = C =

Oral Surg. September, 1974

et al.

CSA 0 0 0 :

B8 (

LSA

ii

0 0 0 0 0 E,

0

1

to defect location: Anterior. Posterior. Central.

visualization 1

B3

B4

CS

AC

0 ii 2 : 0 2

B5 /

0” 0” 0 1 0 1

GSA 0 0 0 0 :, 1 2

B6 1

MA 0 0 i 0 3 0 3

R = Superior. Y = Medial. 1, = Lateral.

phase was documented with photographs and radiographs of each condyle. Artifacts were fabricated with a rountl dental rotary bur. A defect rated as small, varying from 3 to 4 mm. in diameter and 3 to 4 mm. deep, was created in each condyle for Phase B in a variety of locations (Table I). Each small defect was filled with dental amalgam alloy for Phase C, offering a radiopaque artifact. Tlates rubber glove material was utilized to contain the amalgam in the defect. For Phase I) the alloy and latex separator were removed and the defect was enlarged to sizes ranging from 4 mm. to 10 mm. in diameter and 4 mm. to 11 mm. in depth (Table I). The procedure for Phase C was repeated for the large defects created for Phase I> to constitute Phase E. Fig. 1 demonstrates the five phases of one of the twelve defects (condyle No. 10) in one of the seven techniques evaluated (Gillis), and compares the photographs with the corresponding radiographs. Evaluation

of defects

Size of defects. The Phase B defects are referred to as small, while the Phase I> defects are called large. The relationship of defect sizes and condyle size can be determined and evaluated by referring to Table I. (Table I). The defects were charted as to location, Key to defect locakation with the following symbols used to identify the evaluation of the defect on the condyle : A = Anterior S I= Superior 1 = Posterior

M = Medial C = Central II = Lateral

Combinations of these symbols were used to described the location of the defect, with the first letter of each combination denoting the primary location and the following letters describing the extent-for example, LSA = defect on lateral aspect extending to the superior and anterior surfaces of the condyle (Table T).

B7

B8

B9

BiO

Bll

/

Bid

1

SLA

MS

AL

L

SL

1

AM

1

0 0 0 1 0

0 0

: 0

0

0

0

2 0 02

2 0 0

0 0 0

2 0 3

8

3 2 0 5

0 : 1

i

1

31

ii

Total No.

) Per cent

0 0

0 0

4 3

x.3 6.2 x.3 22.9 x.3

1; 4 26

Defect locntio~. The location of the induced condylar defects were selected at random. The key to defect location (Table I) discloses the distribution of the defects on the condyles. Five of the twelve small defects were placed on the lateral third of the condyle (B2, B7, B9, BlO, and Bll), three were on the medial aspect of the condyle (B6, B8, and B12), and four were in the central third of the condple (Bl, B3, B4, and B5). Of the twelve large defects, five were placed on the lateral third of the condyle (112, D7, n9, DlO, and Dll), four were on the medial aspect of the condyle (IX, D6, IH, and Dl2), and three were located in the central third of the c011dy1~ (Dl, D3, and D4). Each of these defects also encompassed a portion of the anterior, superior, or posterior aspect of the condyle and, in many instances, a combination of these. Frequently, enlargement of the defect for Phase D involved an additional surface. Criteria, for scori,~g defect ~4succlimtio)l. A graded scale from 0 to 1 was used to evaluate the degree of visibility of each defect for each of the seven techniques, and evaluation was made by three persons : 0 = No visible defect. 1 = Vague area of radiolucency witjh no break in cortical surface 2X Visible radiolucency not consistent with defect, size and no apparent break in cortex. 3 = IJnquestionablc ratlioluceney showing break in cortex. 4 = Defect obvious with significant cortical disruption. All amalgam-filled defects in both Phases C and E were visible for all techniques. They, together with Phase A, were used for evaluation of Phases B and D. Evnlwrtim of defect Gaunliztrtiolb (Tables IIZ md IV). Since there were twelve defects in each group, and each defect, could score from 0 to 4 points (depending on the degree of visualization), a maximum of forty-eight points could be scored if every defect in a particular technique disclosed maximum visualization.

484

Oral Surg. September, 1974

Goncalves et al.

Table

IV. Evaluation

Radiographic Panoramic Gillis McQueen

of large-defect

evaluation

Inferior-suoerior Updegrave CAPL CLL Total I

Eey A = P = C =

Table

: 0

i 1

0 1 0

0 0 0

0 4 3 7

0 4 0 4

:, 1 2 5

:: 0 3 4

:, 0 2 3

Length

12 11 9 10 4 3 8 2 7 6

:

scores compared to length, thickness, horizontal, Thickness

(mm. )

Thickness

15.0 15.5 17.5 18.2 18.5 18.6 19.4 19.4 19.8 20.0 22.0 23.2

ii 0

S = Superior. M = Medial. L = Lateral.

V. Visualization Length

Table

:: i

to defect location: Anterior. Posterior. Central.

Condyle

visualization

Small

7.2 7.3 9.0 9.0 8.5 8.4 7.0 8.6 6.3

Large

0 3 1 5 1 2 5 1

Condyle

i 12 19 4 5 7 d 7

z 2 3

f

7 8 12 11 6 5 3 4 2 9 10

Thickness

Length

6.3 7.0 7.2 7.3 7.7 8.2 8.2 8.4 8.5 8.6 9.0 9.0

19.8 19.4 15.0 15.5 2,3.2 20.0 22.0 18.6 18.5 19.4 17.5 18.2

and vertical

(mm.) Small

Large 9 7 3 8 1 7 3 5 4 12” 19

VI Small

Ratio Medial Central Lateral Anterior Superior Posterior Numerator in ratio represents total possible

defects

I Per cent

Larae Ratio

defects Per cent

B/84 9.5 14/112 12.5 5/112 4.5 31/140 22.1 13/224 9.3 52/140 37.1 11/224 4.9 55/280 19.6 15/196 7.7 59/280 21.1 o/o 0.0 14/56 25.0 designates total visibility score by region. Denominator in ratio score if maximum visualization were realized for all involvements.

Scores were tabulated for all condyles by radiographic technique for both series of defects (Tables III and IV). Location of defects visualized. After evaluation of the number of defects that could be visualized and determination of scores for each of the radiographic techniques, distribution by location of visibility scores for each technique, together with per cent frequency, was determined is shown in Tables III and IV.

Volume Number

38 3

D7 SLA

Defects created i?z mandibular

D9

08 /

MASP

1

LCAS

Dll

DIO 1

L

1

LS

condyles

Dll (

485

Total

MAS

1

No.

1 Per cent

0 : ii

0 01 10

0 20 i

1 3 i:

: 3 i

0 1 it

2 1; 13

1::: 27.0 27.0

3 3 9

3 2 7

4 3 12

4

0 0 8

ii 0 3

2: 20 82

5::: 41.6

angles Horizontal Horizontal

Condyle

angle

(degrees) Small

Vertical

angle

Large

Vertical

23 22

7 5

3 2

9 ;

-12 - 6

8 7

5 3

21 20 19 18 17 15 13 11 10 9

128 6 3 4 1 2 11 9 10

05 i

3 kl 4 :

43 11 12 1 i

i i

1 0 1 3 1 5

--3 1 6 7 9 11 14 17 17 19

8 12 19

Condyle

(degrees)

6 10 9

Small

0 1 2 i 1

Large i i 8 3 7 4 3 1 19 12

FINDINGS

There appears to be no correlation between defect visibility and length or thickness of condyle (Table V) . Data are inconclusive with respect to dependence of defect visibility on tither horizontal or vertical condylar angle (Table V). A hint that tlefccts arc more visible at the extremes than at the mean might indicate a need for further study. F’or all contlyles, with the exception of No. 6, the visibility score increased with an increase in size of the defect. For the four condples registering the highest total defect-visibility scores (vertical total numbers 7, 8, 9, and lo), the lateral, superior, and anterior surfaces were each involved three times whereas the medial, central, and posterior regions were involved once each (Tables III and IV). Comparing radiographic techniques in Tables III and IV (horizontal totals), it is evident that, for visualization of either small or large condyle defects, the panoramic, Uillis (F’ig. 1)) and inferior-superior projections are inferior. The only technique in which defects were visualized in medial, central, and lateral locations was CAPL which was better than all others, although not outstanding,

Oral surg. September, 1974

Goncalves et al.

486

Table

VII.

Incidence

of defect visualization

by technique

Small defects Techniques Panoramic Gillis McQueen Updegravc Inferior-superior CAPL CLL

i

Medial

third

o/o o/o O/4 o/3 3/4 (75%) 5/11 (45%) o/4

(Bl-12)

Central

third

o/o o/o O/4 213 l/4 l/11 l/4

for medial, central,

(66%) (25%) (10%) (25%)

Lateral

414

third

o/o o/o ‘y$;

l/3

o/4

*

since it scored a composite of a possible ninety-six defect-visibility points, approximately one third of the masimum possible score. If one examines the composite scores for all condyles and all techniques used, tlcfects less than 4 mm. in diameter and depth are visible, even faintly, no more than 7.7 per cent of the time. When defects were enlarged to two and sometimes three or more diameters, the defect-visibility scores rose to only 24.4 per cent. Comparing scores (Table VI) for frequency of condyle surfaces involved for either small or large defects, we find that large defects of the lateral and small defects of the central region constitute the extrcmc ranges of defect-risibility score by condyle surface involvetl. Restricting the location of tlefects to lateral, central, and medial regions along the contlylar axis (Table Vl), it becomes obvious that for small defects the central region has the lowest score. \\‘lien defects were enlarged, scores increased more rapidly for lateral regions than for medial regions. However, enlarged defects of the caentral region bccomc much more e\-ident. Table VII shows the distribution of visibility scores for medial, central, and lateral regions by technique. DISCUSSION

Correct radiographic interpretation is dependent on recognition of changes or lack of changes in form and density of the image on the film. When concentrating on a particular structure in a radiograph, one tends to overlook the fact that the obscrvcd image is a representation of a volume compressed into a plane and that remotely located structures exert their influence on the observable result. One need look only at the variety of forms and densities seen in a “simple normal” intraoral periapical film to realize the complexities to be considered. The mandibular condylc exists in many forms, the sizes and shapes of which are not readily defined. Radiographic examinations of the condyle are further impaired by the complexity of surrounding structures. All radiographic techniques require that the x-ray beam traverse cranial or facial bones in order to project an image of the mandibular condyle. This creates a complex composite to be analyzed. In any given projection it is difficult, if not. impossible, to identify the exact reason why an entity is or is not visible on the radiograph. For this reason, some

and

Volume 38 Number 3

Defects created an wam3ibuhr

condyles

487

lateral locations Larae Me&d

third a/2

l/7 $3

‘(15%) cy;

0 o/3 4/24 (17%) 2/20 (lo%j

defects Central

/Dl-1%) third

o/2 l/7 (15%) l/13 (7%) 2’130/g14%) 5/24 (20%) 10120 (5oo/,j

I

Lateral

third

2/2

(lOO%l

s/20

(4096j

of the general principles will be recalled and opinions cited for specific cases. It should be pointed out that, while comparisons of defect size were made with condyle length and thickness, the image actually included other structures superimposed. It is not surprising, therefore, that the laminagraphic techniques which attempted radiographically to remove adjacent structures give higher visibility scores. The suggestion of possible influence of condylar angulation on visibility scores might be explained as resulting from change of position relative to other structures penetrated by the x-ray beam. The theory of operation of the laminagraph is based on the supposition that thin cuts are made. In practice, the cuts are not clearly defined, so that structures of high density, even at some distance, influence the image. A review of tables III and IV of condyle No. 6 reveals that the defect, after enlargement, was less visible than the small defect. One explanation for this was the creation of more parallel anterior and posterior surfaces, giving a more uniform thickness which could have affected defect visibility. Other contributing factors to explain a drop in visibility score when the defect was enlarged might be unstable electrical factors from the power source, subtle changes in chemistry of processing, or minor variations in positioning of the skull. With regard to positioning of the skull, attention should be called to the fact that, even though a head positioner was used for certain projections, there can be no assurance that positions were exactly duplicated. It should be recognized that, had defects of a given size and position been placed similarly on a different condyle, the visibility might have varied too. If it were possible to obtain a large number of identical condyles and create identical defects so that anatomic structures were no longer variable, the results might have been more conclusive. Preliminary studies indicate that polycycloidal tomography, applying the CAPL and CLL techniques, should provide more definitive radiographic visualization of the condylar defects. CONCLUSIONS

1. Radiographic visualization of radiolucent defects (3 to 11 mm.) is rarely possible by readily available methods. 2. Visualization of radiopaque artifacts (3 to 11 mm.) may be made by even the simplest radiographic technique.

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Oral Surg. September, 1974

3. Small defects involving either end of the condyle are more tletectable than defects that are centrally located. 1. Ilarge defects arc most readily detected when located laterally. 5. A combination of CAPL and CLI, techniques (which gave the two highest visibility scores) should yield the most cliagnostic information. REFERENCES

1. Altschul, W. : Some New Methods in Roentgenography, Am. J. Roentgenol. Radium Ther. 17: 659-666. 1927. Study of Temporomandibular Articulation, J. Am. Dent. 2. Gillis, R. R. : Roentgen-Ray Assoc. 22: 1321-1328, 1935. 3. Lindblom, G. : Technique for Roentgen-Photographic Registration of the Different Condyle Positions in the Temporomandibular
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in Oral Diagnosis, J. Am. : Methods and Application 30. Rosenberg, H. M. : Laminagraphy Dent. Assoc. 74: 88-96, 196i. W. J. : Interpretation of Temporomandihular Joint Radiographs, Dent. Clin. 31. Updegrave, North Am., pp. 567-586, November, 1966. 32. Mazaheri, M., and Biggerstaff, R. H.: Standardized Sectional Laminagraphs of the Temporomnndibular Joint, J. Prosthet. Dent. 18: 489-496, 1967. 3 3 . Morgan, D. H.: Mandibular Joint Pathology, Dent. Radiogr. Photogr. 43: 3-11, 1970. 34. Weinberg, of Duplicability of Temporomandibular Joint RadioL. A.: An Evaluation graphs, 5. Prosthet. Dent. 24: 51%541! 1970. 35. Klein, I. E., Blatterfein, L., and Migbno, J. C.: Comparison of the Fidelity of Radiographs of Mandibular Condyles Made by Different Techniques, J. Prosthet. Dent. 24: 419-452, 1970. 36. Lewis, G. R.: Temporomandibular Joint Radiographic Technics-A Comparison and Evaluation of Results, Dent. Radiogr. Photogr. 37: 8-20, 1964. Reprint reqwests to: Dr. Henry M. Rosenberg Department of Radiology College of Dentistry University of Illinois at the Medical P. 0. Box 6998 Chicago, Ill. 60680

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