CATEGORY 98 AUSTRALASIAN DENTIST LINICAL Introduction The jaw joints are called the Temporomandibular Joints (TMJ’s) (Figs. 1, 2 and 3) and the affliction associated with them and the muscles of mastication is called a Temporomandibular Disorder (TMD). Temporomandibular disorders (TMDs) were classified in 1992 by Dworkin and LeResche into three major diagnostic groups. These were: (I) muscle diagnoses, (II) disc displacements and (III) arthralgia, arthritis and arthrosis (Dworkin and LeResche 1992). Comprehensive counselling of Temporomandibular Disorder (TMD) patients has often been lacking in both clinical practice and research protocols. Although Ramfjord and Ash claimed ‘it is important to support the splint therapy with enthusiastic counselling of the patient for every appointment’ (Ramfjord and Ash 1983,Ramfjord and Ash 1994). Part 1: ‘Full Counselling’ during ‘Full Occlusal Therapy’ with case studies for habit modification, sleep posture analysis and instructions for delivering a splint to manage TMDs. By Dr. Michael Darveniza MDSc PhD (Qld) FRACDS Fig. 1 Schematic vertico-oblique view of the TMJ’s, teeth and surrounding structures of a 14-year-old with a premature contact 17/47, often due to the erupting wisdom teeth, and a normal condyle/disc/fossa assembly and centred disc. Fig. 2 Schematic vertico-oblique view of a physiologically adapted mandibular position from figure 1 now with an adaptive centric occlusion. The TMJ disc shows anterior displacement with reduction and a stretched posterior ligament. The physiological adaptation process involves posturing the mandible forward and laterally to circumnavigate away from the prematurity to achieve maximum interdigitation but at expense of the disc. An aetiological hypothesis could be that with hyperfunction of this off-centred mandible that the thickest portion of the disc was used to shim the fossa/condyle to stabilise the mandible during mastication resulting in chronic disc displacement. Full occlusal protection Full occlusal protection can be defined as an occlusal or bite scheme that protects the teeth, muscles of mastication and TMJs during a significant range of excursive jaw movements for differing skeletal jaw types. The common length of lateral paths requiring full protection for different skeletal types include Class 1 and Class 2 Division 1 paths of 4-6 mm, Class 2 Division 2 paths of 6-12 mm and Class 3 of 3-5 mm. Theocclusionor bitecanbe sub-divided into the four major bites or occlusions namely, hinge occlusion, left occlusion, right occlusion and forward occlusion. The lower jaw is called the mandible and moves through four major movements namely, hinge, left, right and forward mandibular movements. Hinge movement occurs centrally in the TMJ’s with the head or condyle of the jaw joint rotating against a tough mobile fibrocartilage disc seated in the cup or fossa. Hinging directs the lower jaw towards the back teeth for chewing (Figs. 1, 2 and 3). If the teeth on the left side bite simultaneously with the teeth on the right side a protective hinge occlusion occurs and this protects the TMJ’s and musculature. When the lower jawhinges and opens past 15mm, the condyle stops hinging and moves straight or translates leaving the safety of the fossa and is directed straight onto a bony outcrop called the articulate eminence to perform excursive movements. Excursive movements include left, right and forward mandibular movements for tearing and incising food. The canine and incisor teeth, in general, guide the lower jaw during excursive movements to protect the discs of the TMJ’s. When the opposite upper and lower canines correctly couple a protective left and right bite forms with corresponding mandibular movements
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