Australasian Dentist Issue 93

CATEGORY 86 AUSTRALASIAN DENTIST LINICAL Part 2: Preliminary investigation of 200 TMD patients using ‘Fully Protective Occlusal Splints’ with ‘Formal Occlusal Splint Therapy’ By Dr Michael Darveniza MDSc PhD (Qld) FRACDS, Prosthodontist: Lismore, New South Wales. Measurement of splint parameters The length of the lateral path from the centric stop to the canine rise landing pad was measured with a periodontal probe. This involved adding three increments together: namely, early path with lateral or latero-distal movement, mid-path with vertico-lateral movement and final path with antero-vertical movement ending at the canine rise landing pad (Figs. 6, 7 and 8). The length of protrusive path ramps fromthe centric stop region to the end of the protrusive landing pad was measured with a periodontal probe (Fig. 9). This involved adding two increments together: early and mid-path collectively and final path (Fig. 9). Lateral and protrusive paths are curvilinear but were measured in a linear manner. Overjet was measured with a periodontal probe from the labial of the lower incisors and canines to the labial surfaces of the splint when in hinge occlusion, and varied between 3-5 mm. Disclusion was measured with a periodontal probe between the splint and the mesiobuccal cusp of the lower first molar while the ipsilateral lower canine contacted the canine rise landing pad of the splint (Part 1 Fig. 5). (Darveniza 2022). Equilibrating and adjusting the occlusion Hinge occlusion was equilibrated by registering centric stops using two layers of red/black Accufilm (Parkell, Farmingdale, New York, USA) registration paper together in articulating forceps for larger centric stop area of registration as illustrated (Figs. 6, 7, 8 and 9). This also resulted in two colour choices from the same paper, namely two layers of externally visible red named ‘double red’, or two layers of black named ‘double black’ for registration on different surfaces and situations. An example of different surfaces requiring registration, double black being more visible on gold crowns than double red (Kelleher 1984). An example of a clinical situation requiring occlusal registration of a splint, prior to fitting a bridge under an existing splint, the occlusion of the splint could be registered in red. After fitting the bridge and internally adjusting the splint, the registration is performed on the splint with black. If the occlusion on the splint is the same as before the bridge was fitted, then the black marks will register evenly on top of all of the red marks indicating that the splint is not rocking on the bridge. Centric relation was recorded using the Dawson 1979 bilateral manipulation technique for initial and final evaluation. Centric relation was largely determined using unguided closure as researched by Hobo and Iwata but with a modification by the author using digital skin contact on the left side of the chin region (not chin point guidance) to monitor errant unilateral mandibular movements (Hobo and Iwata 1985). All patients were treated in the supine position with the maxillary plane of the teeth at 90 degrees to the floor to optimize recording centric relation (Lund et al. 1970). Fig. 6. Early path of 3 mm with a latero-distal vector during left lateral protective mandibular movement. Latero-distal movement appears to be associated with lax TMJ’s from bruxism stretched ligaments and a large immediate side shift of 2 mm or more noted during Pantronic readings. Fig. 7. Mid-path of 7 mm with a vertical vector forming along a moderate incline restrictive canine rise ridge in left lateral protective mandibular movement. Fig. 8. Final path of 2 mm with an antero-horizontal vector during a left lateral protective mandibular movement. Fig. 9. The early path of 3 mm (two black/ white lines) shows no red marking following an adjustment to create a small open bite to a depth of about 1 mm at the centric stops, then 1.5 mm along the path about 0.5 mm deep and graduated to zero at the end of this 3 mm path. Mid-protrusive path was 5 mm long and final path at the incisal edge was 2 mm and ends as a protrusive landing pad.