Biomedical subjects
Publications and source records attributed to J P Lucchini.
A universal face bow is reported for transferring an arbitary or located hinge axis on most articulators. Its use is simple and safe due to the rigidity of the assemblies during every step of the transfer.
A new semi-adjustable Arcon articulator is reported. It is an evolutive device that can be set with two different types of condylar housings. - A Type: adjustable condylar guidance, preadjusted Bennett angle at 13 degrees - B Type: adjustable condylar guidance, adjustable Bennett angle. It is possible to set on this B type fossa assembly another Bennett wing with an adjustable immediate side shift This device has a double lock in centric relation and may be set with an arbitrary or localized hinge axis.
The use of a mounting table allowing arbitrary hinge axis transfer on a semi-adjustable articulator is described. Following this method an accurate stabilization can be expected. This may prevent errors during the mounting of maxillary models.
When recording and transferring centric relation onto an articulator errors can be minimized by proper use of dental materials. Remaining errors may be due to either the patient or the clinician. 3 recording techniques (Lucia, Dawson, Ramfjord) are being tested by 2 operators on 12 patients. In order to get a proper centric relation one must not rely upon a technique of taking it but rather on an adequate clinical evaluation of the TMJ at that moment. The role of inadequate intermaxillary relationship upon painful TMJ syndroms cannot be underestimate.
3 waxes commonly used to record interocclusal positions are tested on an articulator. All recordings are made at the same opening and the condylar variations are analysed with a Buhnergraph. Soft materials may induce errors and relining the interocclusal records allows a higher degree of accuracy.
Dental plasters and self-curing acrylic resins are tested. One must pay attention to the setting expansion of plasters and to the setting contraction of acrylic resins which may be very important if these materials are used without care.
Three materials commonly used for interocclusal registrations are tested under habitual conditions. The wax-type samples are softened in hot water to the optimal temperature, and then cooled off for hardening either in ice water, or room temperature water, or at room temperature air. These materials are stored for one month. Measurements are taken: - prior to any treatment - after hardening - after storage. The results are statistically analyzed. The least distorsion of material is obtained with the softer wax and vice versa. The room temperature air cooling has given best results. Time does not seem to modify measurements made on heat treated materials which may be accurately stored at room temperature.
When mounting models on the articulator there is some possibility of error due to the expansion of plaster during the setting period. If one does not pay attention to this expansion, one can observe an opening in between the arms of the articulator. In order to minimize expansion one must: -- increase the W/P ratio -- decrease the amount of plaster used for mounting the models The expansion modifies the reference plane and this is important only in case of remountings.