An Investigation into Condylar Position with Leaf Gauge and Bimanual Manipulation

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1 An Investigation into Condylar Position with Leaf Gauge and Bimanual Manipulation Donald H. Downs, D.D.S. Colorado Springs, CO. U.S.A. INTRODUCTION The information derived from th is study is worth serious consideration because it implies that the correct use of a leaf gauge greatly enhances the clinician's ability to obtain and record centric relation. Only a minor amount of experience and technique familiarity is required. The important concept to grasp is that TIME is an essential component of centric relation capture. The use of a leaf gauge as an aid to obtaining and recording centric relation is controversial. There have been reports in the literature that refer to its use which claim that the condyles are forced posteriorly. 1 A clinician for whom I have the greatest respect has stated that in his study club work on centric relation they consistently show with the Verichek that the distal vector of force resultant from the leaf gauge forces the condyles down and back when the interincisive angle is steep and the horizontal overlap is tight, as is common in a Class 11, Div. 11 occlusion. 2 Other clinicians who enjoy an equal reputation use the leaf gauge routinely with obvious success. PURPOSE This study was undertaken to attempt to visualize what the condyles were actually doing in the sagittal plane under the influence of the leaf gauge, bimanual manipulation or a Lucia jig and to compare the three methods. The Lucia jig was included because when correctly made it provides a contacting surface for the lower central incisors which is at ninety degrees to the arc of mandibular closure. Theoretically, this eliminates the potential for a distal vector of force. MATERIALS A Klett type clutch (Fig. 1) was constructed of plastic so that when Fastray auto-curing acrylic was injected into the embrasure spaces of the teeth it would bond to the clutch allowing firm The Journal of Gnathology Vol. 7, No. 1, :i

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7 An Investigation into Condylar Position with Leaf Gauge and Bimanual Manipulation It should be clearly understood that the equipment for support of the graph paper during this study did not provide true stability. None of the patients could go through minutes of protrusion-retrusion, opening and closing, method changes, tooth contact decision making and photography without moving their head. Finite conclusions of less than one-half millimeter probably are not warranted but are not necessary either. General condylar direction and method comparison were the goals and were clearly shown. CONCLUSION The conclusions are: 1) that the leaf gauge, as used in this study, does not cause the condyle to be positioned down and back. 2) that no difference in condyle position in the sagittal plane was demonstrated between the three methods of mandibular positioning. 3) most importantly, that time is required to obtain the centric relation position, and that without going through serial leaf gauge additions, one can only guess when compression is complete. 4) that centric relation is a muscle induced position. 5) that since rebound occurs rapidly, one must take that into account when performing occlusal correction. 6) that when the terminal transverse mandibular axis is marked on the skin, the same mandibular positioning technique should be used as will be used for recording centric relation. Therefore, the plea by Dr. McHorris for resolution before reconstruction4 is supported and emphasized by this study, because without resolution, the retention of some degree of distraction during centric relation recording is highly probable. REFERENCES 1. Williamson, E.H., Steinke, R.M., Morse, P.K., Swift, T.R.: Centric Relation: A Comparison of Muscle Determined Position and Operator Guidance. Am. J. Orthod., Vol. 77, , Feb Dawson, P.E.: Personal communication. Chicago, 111., Feb Downs, B.H., Ritchey, B.: One Man's mandible: delivered before Acad. Denture Prosthetics, Colorado Springs, CO, McHorris, W.H.: TMJ Dysfunction - Resolution before Reconstruction: J. of European Acad. of Gnath., Vol. 1, Dr. Donald Downs 1235 Lake Plaza Drive, Suite 251 Colorado Springs, Co U.S.A. The Journal of Gnathology Vol. 7, No. 1,