THE CONSTRUCTION AND APPLICATION OF THE

CEPHALODONTOMETER

EDWARD M. GRIFFIN, D.D.S., and MEYER HOFFMAN, D.D.S., BROOKLYN, N. Y.

TH E recent advance in the science and art of orthodontia, wherein studiesin the growth and development of the jaws and faciocranial structures have

constituted so important a part, has given evidence of the great need for scien­tifically accurate mensuration of relative growth rates and computations in dis­tances of the various anatomic parts involved.

Scientific considerations concerning the most feasible and promising of theavenues of approach to study this problem seem acceptable to the choice of thepioneer in the field, namely, B. Holly Broadbent, and the method to be that ofthe scientifically accurate production and the duplication of radiographs forcomparison of changing measurements and proportions.

In consultation with an engineer, we have completed the construction ofan instrument to initiate such studies.

In considering the nature of the orthodontic problem, it is apparent thatit is necessary, in order to formulate a plan for practical and reliable diagnosis,to consider the revelations of research pertaining to growth and development ofthe jaws and face, particularly as concerns a starting point from which tomeasure or determine the relative positions of the jaws to each other; second,as concerns their position respectively to underlying structures, remotely to thecramum.

It is with regard to this second consideration that the need for the applica­tion of such an instrument, as herein described, is manifested. The studies in­volved are the relative position of the facial structures as they show emergenceto a greater or lesser degree from beneath the brain case; the status of growthof the brain case and of underlying facial structures; the study of the compara­tive growth rates in degree as well as speed during respective periods with thecenter or anterior border of the foramen magnum construed to be the center ofgrowth activity and the area contiguous to the basoeranial axis as that whichmanifests lesser change in applying mensuration to respective outlying anatomicpoints which in turn show greater change and instability.

This study is promising from the approach by scientifically accurate radio­graphs, with others of extreme accuracy in duplication for comparison of chang­ing measurements and proportions. The processes of growth, as revealed throughresearch by several investigators, indicate that growth takes place concomitantlywith added increment from behind, as well as increase in height and width.

, 'The face therefore grows backward, but in consequence of this, the facemigrates forward," as stressed by Milo Hellman; also, in concurrence withHunter, Humphrey, Keith, Compton, Brash, Todd and others who made similarstudies through different avenues of approach.

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240 Edward M. Griffin and Meyer Hoffman

Clinically, then, it is important to apply the stimulus so that the develop­ing structure adds the increment posteriorly, without drawing the teeth forwardwithin their investing tissues by a direct stimulus in advance of the generalfacial development. The dentition should present, in the finished case, in a satis­factory position relative to the apical bases of the jaws.

Fig.!.

Fig. 2.

If subsequent to treatment the dentition is positioned more anteriorly thanthat which constitutes a proper basal relationship, then a bimaxillary protrusionis produced and a decided disharmony in the facial proportions results.

Consequently, such studies pertaining to the changing positions of the teethand in turn the relative changes of the underlying structures should be of in­estimable value to offer enlightenment concerning the true effect and the changesinvolved during the treatment of malocclusions.

Construction. and Application of the Cephalodontometer 241

The mechanical construction of the cephalodontometer consists of a frame­work within which the head of the patient is placed in position for exact duplica­tion at any subsequent time to produce the film of duplicate exposures to thecentral rays of the x-ray machine.

First, the head is known to be in duplicate position at the subsequent sittingsby the readings of various calibrated level gauges, the readings of which recordthe position of the head relative to three planes, in complete registration, as it is

r

Fig. 3.

Fig. 4.

definitely positioned within the framework. The duplication of position of thehead relative to the x-ray machine is made by means of focusing a beam of lightfrom a telescope which is fastened to the machine. The focus is made uponthe center of the target which is fastened to the framework. The position ofthe target relative to the head is definite and recorded by the various calibratedgauges, as stated.

The manner of positioning the head preparatory to making the exposure forthe production of the lateral plate is herewith described.

242 Edward M. Griffin and Meyer Hoffman

The head is positioned first, relative to the calibrated adjustment rods, EE'(Fig. 1), to be received in the ear holes. The readings of the distance from endof rods to surface on respective suspension arms are recorded. The head isleveled in the horizontal plane relative to the ear rods in position by adjustmentbilaterally of the level gauges, LL', which are mounted on adjustment arms.

Fig. 5.

Fig. 6.

These arms extend from the suspension arms, which carry the ear hole rods, tothe other terminal which is the orbitale feeler point. The points are positionedwhen the orbitales have been palpated. The extension arms which carry thelevel gauges terminate by two adjustment extensions, so situated that theyintervene between the level gauges and the final point terminations, or the

Construction and Application of the Cephalodontometer 243

orbitale feeler points. These two adjustment extensions are each calibrated,D and D' (Figs. 1 and 2) and the readings are recorded from each, bilaterallyto the head, after their adjustment permits of the level gauge readings with theear rods in position. The head is now securely positioned in the Frankfort hori­zontal plane.

The calibrated extension arm which offers two point support to the occiputis next positioned securely to the surface of the head and the reading is recorded,G (Fig. 2).

The frontonasal extension support arm is next adjusted to the nasion forfurther fixation of the head, C (Figs. 1 and 2).

Fig. 7.

The parietal extension arm support, B (Figs. 1 and 2), is next adjusted tothe head and locked to position.

The central, principal extension arm which carries the ear rod and thefurther extension arm to the orbitale on the side of the head which is towardthe x-ray machine also carries a circular calibrated gauge, J (Fig. 2), which ismounted with an adjustment protractor. The protractor terminates with a dot,F (Figs. 1 and 2), in the center of a circular target. This point is the pointof focus for a beam of light projected from the telescope, H (illustration 3 and5), which is mounted upon the x-ray machine, I (Figs. 3 and 5).

In the next preparation for the exposure, the light is so focused from a cross­section hairline field view in the telescope and the reading is so recorded of theangulation of the protractor to the circular gauge.

244 Edward M. Griffin and Meyer Hoffrnan

The instrument permits of variation in the position which bounds the fieldof the central ray as determined by the angulation set for the protractor; how­ever the target F is always 2% inches below the central ray and it is always anddefinitely so fixed.

The cassette, A (Figs. 1-5), carrying an 8 x 10 film with intensifying screen,is mounted and securely positioned in the recess within the frame to receive iton the opposite side of the head from the x-ray machine. The cassette frameis provided with a calibrated scale on the sides, K (Fig. 4), which intercepts therays and thus provides the gauge as shadowed upon the film, for use in record­ing the distances of various readings when the, film is studied and mensurationsare made.

The head being securely positioned in the Frankfort horizontal plane andall readings having been recorded with the beam of light focused upon the center

Fig. 8.

of the target, the field is cleared of mechanism for the exposure. The apparatusis next swung to position of retraction as shown in Fig. 5. In this position, theoccipital, parietal, and frontonasion extension arms only remain in position toprevent any movement of the head during exposure. Previous to exposure, leadpoints are placed in the ear holes to record the porion points on the film, theear hole pointers having been removed with retraction of the apparatus. Fig. 6shows a view of a typical lateral plate with markings of some principal ana­tomic points for study film. Fig. 7 is a close-up illustration of the apparatusfor clearer view of structural details. Fig. 8 shows application of apparatus topatient's head during the procedure of making calibrated readings.

ONE HANSON PLACE.