Facebow registration and fabrication of the occlusal splints
TMJ, plaster, CAD
CAD, CAVITY, TMJ
A digital facebow (Zebris JMAnalyser+, Zebris Medical GmbH, Isny, Germany) was used to capture the patients’ axis relations and the trajectories of the temporomandibular joint (TMJ) in accordance with Posselt’s envelope of motion. Additionally, condylar guidance inclination, lateral excursion and the Bennett angle were recorded. The measurements were saved as XML data and later used for the virtual planning of the occlusal splint. Dental impressions of both jaws were taken with a polyether impression material (Impregum) to fabricate dental plaster casts. The maxillary cast was mounted in an articulator (Artex CR, Amman Girrbach AG, Koblach, Austria) according to the individual axis relations obtained with the digital facebow. The mandibular cast was mounted in the MMR position captured with the bite registration. The dental casts were digitized in the designated MMR position by a laboratory scanner (Tizian Smart-Scan Plus, Schütz Dental GmbH, Rosbach, Germany) and the occlusal splint was virtually designed with a CAD software (exocad, exocad GmbH, Darmstadt, Germany) by a dental technician, who was blinded to the type of MMR registration method. The virtual splint was exported as a standard tessellation language (stl) file and sent to a dental milling unit (Tizian Cut 5.2 plus, Schütz Dental GmbH), where the occlusal splint was milled from a PMMA blank (Astron Clearsplint, Schütz Dental GmbH) with thermoplastic properties. Finishing of the splints were performed by a dental technician. The splint was inserted into the patient’s oral cavity in a second appointment, where the accuracy of the internal and occlusal fit was examined. If any further occlusal interferences appeared, the splint was adjusted and the extent of the necessary adjustments was documented (“none”: 0, “very few”: 1, “a few”: 2, “many”: 3, “very many”: 4). All patients were instructed to wear the occlusal splints regularly at night (sleep splint).