Abstract
Among the various methods (including the method using Lucia's jig) for guiding the mandible to centric relation, locating centric relation with a leaf gauge has been assumed to be the optimum way.
In this paper, the virtue of the Lusia's jig which has been improved by DR Lusia in 1985 is discussed in comparison with the old one. The improvement was to add a ledge on the upper part of the lingual side of the jig to where the incisal edge of the lower incisor contacted and in which the surface of the ledge was made in parallel to the occlusal plane.
One of demerits of the old Lucia's jig was that the patient was apt to bite anteriorly due to lack of vertical stop for the lower incisor, causing the condyles to displace anteriorly. On the contrary, another demerit of it was that, in some cases, the incisal edge of the lower incisor was apt to slide along the lingual surface of the jig in supero-posterior direction and then the mandible was forced to retrude and the condyles were pressed backwards.
In the improved version of Lucia's jig, the above mensioned demerits were cancelled by placing a vertical stop (a ledge) . In addition, an merit was added that the incisal edge of the lower incisor can move freely back and forth or left and right in small area on the surface of the ledge.
The method of locating centric relation with a leaf gauge has the same demerits as the old Lucia's anterior jig had. Therefore, it is concluded that the method using an improved Lucia's jig is superior than the method using a leaf gauge.
