"The first alternate embodiment uses a single axially attached rod or wing on the lower portion of the analog post. The post is then forced into a slightly undersized hole and resists both twisting and pull-out. A second embodiment using axial rod features uses two such rods on opposite sides of the analog post. A third such embodiment uses three such rods attached every 120 degrees around the bottom end of the post. Any number of such rods can be attached preferably in a symmetric array. The rods can also be enhanced in their gripping action by texturizing their outer surface; alternatively, axial grooves along their length at their outermost position can be added.
"Another embodiment of analog post for hole engagement is made of a larger diameter with a tapered top; a regular array of longitudinal grooves or flutes on the outer side surface engage the hole sides. Yet another embodiment of analog post is one with a knurled outer surface and an annular groove near the bottom end. A final embodiment has male threads along the analog shank which permit screwing into the hole in the resin model much akin to the thread-forming action of a wood screw in a pilot hole in wood.
"When using model based presurgical planning techniques, computer based stereolithography or non-computer methods are used to create an accurate jaw model of resin, plaster, or 'stone' or other plastic material. Similarly, surgical guides which form fit onto the jaw model and onto the patient's jaw are also created. Once analogs are inserted into the jaw model, surgical guide sleeves are bonded to the surgical guide at the analog sites using cement or adhesive inside oversized holes in the surgical guide. These must be at the appropriate height, and the orientation must match that of the analogs in the jaw model. Another embodiment of this invention is a set of accessory parts and a method to insure that the alignment of the surgical guide sleeves bonded to the surgical guide will match that of the analog in registration.
"After the analogs are inserted in the jaw model, at each analog site attachments to each analog are made which will orient the surgical guide sleeve rigidly and accurately to represent the orientation of the analog. After all the surgical guide sleeves are thereby attached to the analogs, the surgical guide with oversize holes at each analog site is lowered onto the jaw model and all surgical guide sleeves are bonded to the surgical guide while they are still attached to the analogs. After the cement or adhesive sets, screws are removed from each analog to free the surgical guide with all of the surgical guide sleeves accurately attached. The guide is then used inside the patients mouth to drill accurate implant holes by using each of the surgical guide sleeves as drill guides.
"The parts attached to each analog in the jaw model are a surgical guide sleeve supported by a form-fitting cylinder support mount, a tube adapter to adjust the height of the guide sleeve above the analog (if necessary), and a screw threaded through the three parts from the top to secure the assembly to the analog below.
"Presurgical planning techniques using accurate whole skull models or models of skull portions other than jaws are also used for cranial and facial reconstruction. Attachments use surgical implants in bone. For example such an approach is used to repair missing bone in the cranium, ear prostheses, and nose prostheses. The procedure starts with an accurate model and a surgical guide with oversize holes in registration with the analogs inserted at sites determined by a surgeon on the skull model. Using the procedure and analog attachments as described above for dental implants, appropriately sized tube adapters, cylinder support mount, surgical guide sleeve and attachment screw are attached to each analog in the skull model. The surgical guide is then fitted carefully atop the protruding elements atop each analog, and the surgical guide sleeves are cemented or otherwise bonded within the oversize holes of the guide capturing the precise angle of the analog in the model. The analog screws are then removed releasing the surgical guide with guide sleeves attached for accurate drilling during the surgical procedure for insertion of the implants.
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