Australasian Dentist Issue 93

CATEGORY AUSTRALASIAN DENTIST 87 LINICAL Splint adjustment was performed in hinge occlusion by creating terraced centric platforms for the lower buccal cusps to occlude at right angles preventing incline contacts and slides (Fig. 10). The size of each platform was a minimum of 3 mm in diameter but was usually a rectangle 3 mm antero-posterior by the occlusal width of the splint (Fig. 10). Terracing was required as the occlusal plane of a splint has irregular curves from the presence of the Curve of Spee and tilted teeth. Each terrace was initially formed by adjusting about 50% from the mesial portion of the centric stop as this mark usually corresponds to the mesial incline of the lower buccal cusp. This procedure was repeated until only the tip of the buccal cusp was hitting the centric platform at right angles (Fig. 10). If overadjustment occurred in the regions of the mesial portion and/or centre of the centric stop then the distal incline of the lower buccal cusp would engage resulting in an incline, contact that was adjusted from the distal portion. Adjustments continued until bilateral simultaneous precise right-angle contacts occurred to form a protective hinge occlusion without micro-slides (Part 1 Fig. 1) (Darveniza 2001). Lateral occlusion was adjusted to allow the lower canine to contact on the splint in the following manner: 1) lateral or latero-distal movement in early path (Fig. 6), 2) vertical movement on the canine rise ridge or lateral restrictive ridge with a moderately steep angle in mid-path (Fig. 7) and 3) a flat landing pad of 2 mm in final path with an anterior mandibular vector (Fig. 8). The final length of the path from centric stop to the landing pad was bio-designed a few millimetres short of the border movement. The centric stops opposite the lower canines were then ground away so an open bite of 0.25–0.5 mm formed to accommodate lateral and anterior/ posterior mandibular movements that occur fromwearing a splint thus preventing canine impingement (Kovaleski and De Boever 1975). These adjustments resulted in a vertico-lateral mandibular vector forming a protective lateral occlusion (Fig. 8) (Darveniza 2001). Protrusive occlusion was adjusted to allow the lower incisors, usually the central incisors, to move on two or occasionally three protrusive ramps on the splint in the following manner: 1) initially, the early path (3 mm) and mid-path were adjusted in bilateral contact with a sagittal vector and 2) continued to a flat landing pad of about 2 mm in final path (Fig. 9). The length of protrusive path from the centric stop region to the landing pad was bio-designed a few millimetres short of the border movement. The final adjustment of the 3 mm early path involved: 1) creating an open bite by cutting the centric stops away to a depth of about 1 mm; 2) then 1.5 mm along early path the open bite was continued to a depth of about 0.5 mm and 3) finally graduating the remaining 1.5 mm early path open bite to zero (Fig. 9). This triangular shaped open bite created an occlusal freedom space , called a protrusive freedom space, to accommodate lateral and posterior to anterior mandibular movements (Kovaleski and De Boever 1975). These mandibular changes occur in hinge occlusion between splint adjustment appointments. This protrusive freedom space prevented incisal impingement while creating a bilateral guided sagittal mandibular vector resulting in a protective protrusive occlusion (Fig. 9) (Darveniza 2001). Latero-protrusive occlusion was prevented by designing a large depression about 2-3 mm deep between each protrusive ramp and canine rise ridge. This latero-protrusive fossa along with the concave shape (3-4 mm deep) at the splint edge opposite the 12 and 22 teeth discouraged the development of latero- protrusive contacts and parafunction (Fig. 11). Air vents Air vents were incorporated in the lateral incisor regions of the splint for those patients with breathing problems such as those with nasal obstructions, mouth breathers with large lips andmouth sucking patients (Fig. 12). The vents were about 8 mmwide by 4mmhigh on the labial surface of the splint centred over the lateral incisors and going through to the latero-protrusive fossa (Fig. 11). The vents did not affect the occlusal scheme but improved comfort and compliance (Fig.12). Formal fully protective occlusal splint therapy for 200 TMD patients Complete oral examination of TMD patients was carried out in parallel with two occlusal orientated papers by Egan (Egan 1982) and Rieder (Rieder 1975). The diagnostic imaging examination included an initial radiographic evaluation of TMJ’s, teeth and jaws with an orthopantmograph followed by lateral transcranial radiographs, arthrograms, and MRI of the TMJ’s as indicated. All comments, including colloquial ones, made by the patient were recorded. Examination and palpation of muscles and joints including digital verification externally and or via the external auditory canal by the patient and/ or operator. Patient selection Two hundred dentate patients were selected and treated by the author in his private practice with an emphasis on TMD disc displacement cases. Patients selected had a TMD but not solely a muscle diagnosis (Fricton 2007, Poveda-Roda et al. 2012). Patients with severe osteoarthritis, rheumatoid arthritis, osteoarthritis with arthralgia, or arthrosis were excluded following radiological examination. Fig. 11. A 2-3 mm deep latero-protrusive fossa (blue regions), restrictive canine rise ridges (red lines), raised protrusive ramps (red bands) and a 1-2 mm deep inter-ramp fossa (green) opposing the lower incisal midline. Fig. 12. Air vents for a mouth breathing patient with full shaped lips that peripherally sealed the splint, but the vents formed an airway for both comfort and compliance. Fig. 10. Medio-occlusal view of a splint with red markings showing centric stops on terraced centric platforms and some stops highlighted peripherally with white marker.