Australasian Dentist Issue 93

CATEGORY 88 AUSTRALASIAN DENTIST When an MRI cannot be prescribed a clinician must consider a provisional TMD differential diagnosis between ‘clinical disc displacement’ and muscle diagnoses, and arthritic conditions (Dworkin and LeResche 1992). The author selected patients with two or more of the following signs and symptoms frequently associated with clinical disc displacement: TMJ pain other than arthralgia, joint noises other than solely coarse crepitus (arthrosis), chronic restrictedmouthopening or closing other than myofascial spasm, noticeable deviation (2 mm or more) of the mandible during opening but not associated with an asymmetrical mandible or muscular spasm, history of locking but not transient trismus. Six of the 200 selected patients had an arthrogram or MRI and of these five were diagnosed with non-reducing discs and the other a reducing disc. Numerical guidelines for splint design The recommended numerical guidelines to fabricate a ‘Fully Protective Occlusal Splint’, colloquially called a ‘Darvo splint’, for adult patients included: Angle’s Class 1 and 2 cases were 4-5 mm for splint thickness at the first molars, 9-11 mm for lateral slide with 4-5 mm of overjet, 8-10 mm for protrusive path with 4-5 mm overjet and disclusion of 4-6 mm; and Angle’s Class 3 cases were similar but varied with shorter excursive paths of 6-8 mm for lateral and 5-7 mm for protrusive paths and a smaller overjet of 3-4 mm. For children and teenagers, the parameters were: 3-4 mm for splint thickness, 7-9 mm for lateral slide with 3-4 mm of overjet, 6-8 mm for protrusive path with 3-4 mm overjet and disclusion of 4-5 mm. For patients with reducing disc displacement 4-5 mm thick splints were recommended (Hegab et al. 2018). For patients with non-reducing disc displacements (Hegab et al. 2018) , severe clenchers and bruxers, deep overbite and worn-down dentitions 6-7 mm thick splints were recommended. Extreme bruxers and those patients who perform extreme cross- over were supplied with splints with extra- long lateral paths between 12-15 mm long, on the affected side. The lateral path length from centric to the border movement has been measured to be about 12 mm in pantographic studies (Darveniza 2001). The lateral path length measured from 100 of these splints was a mean of 10.2mm to enable accommodation of large canine raises and to accommodate for lip comfort (Table 1). Formal occlusal splint therapy Patients were advised to wear the splint when sleeping, and ideally an extra two hours during day but not when eating, and only all day if the patient felt the necessity. The sequence and timing for formal occlusal splint therapy involved generally four or occasionally more adjustments over a minimum three-month period (Table 2). At the end of this period near-reproducible posterior centric stops in hinge occlusion were mostly observed between the third and fourth splint adjustments generally with concomitant diminution of TMD symptoms. At each splint adjustment appointment, the patient’s comments, signs (measure mouth opening), and symptoms were recorded, and targeted counselling continued. Acknowledgements My gratitude is extended to ceramists Paul Buchanan and Simon Donaldson, dental technician Peter Stefan and denture prosthetist Peter Anastasia for constructing these ‘Fully Protective Occlusal Splints’. I am grateful to Carl Warner, professional photographer, for all his audio-visual contributions in this paper. I would like to thank John Atkins, former lecturer in philosophy from the University of Queensland, for the editorial help he afforded me in writing this paper. u Correspondence: mdarvo@hotmail.com References Darveniza M. Full occlusal protection-Theory and practice of occlusal therapy. Australian Dental Journal. 2001;46(2):70-79. Darveniza M. Part 1: Preliminary investigation of 200 TMD patients using ‘Fully Protective Occlusal Splints’ with ‘Formal Occlusal Splint Therapy’. Australasian DENTIST No 92 MAR-APR ed. Black Rock, Victoria: Great Australian Publishing; 2022. p. 70-72. Dworkin SF, LeResche L. Research Diagnostic Criteria For Temporomandibular Disorders: Review, Criteria, Examinations and Specifications, Critique. Journal of Craniomandibular Disorders: Facial & Oral Pain. 1992;6(4):301-355. Egan N. Complete Oral Examination with a view to Eliciting Occlusion Related Temporomandibular Joint Pain Dysfunction. Australian Society of Prosthodontists Bulletin. 1982;12(1):7-12. Fricton J. Myogenous Temperomandibular Disorders : Diagnostic and Management Considerations. Dent Cl N Am 2007;51:61-83. Hegab A, Youssef A, Abd Al Hameed H, Karam K. MRI-based determinationof occlusal splint thickness for temporomandibular joint disk derangement: a randomized controlled clinical trial. Oral Surg Oral Med Oral Pathol Oral Radiol 2018;125:74-87. Hobo S, Iwata T. Reproducibility of mandibular centricity in three dimensions. J Prosthet Dent. 1985;53 (5):649-654. Kelleher M, Setchell DJ. An Investigation of Marking Materials Used in Occlusal Adjustment. Br Dent J. 1984;156:96-102. Kovaleski W, De Boever J. Influence of occlusal splints on jaw position and musculature in patients with temporomandibular joint dysfunction. J Prosthet Dent. 1975;33(3):321-327. Lund P, Nishiyama T, Moller E. Postural activity in the muscles of mastication with the subject upright, inclined, and supine. Scand J dent Res. 1970;78:417- 424. Poveda-Roda R, Bagan JV, Sanchis J. Temporomandibular disorders. A case- control study. Med Oral Patol Oral Cir Bucal. 2012;17(5):794-800. Rieder C. Development of a simplfied system for clinical evaluation of occlusal interrelatioships. Part II. Storage of the information. J Prosthet Dent. 1975;33(4):433-441. Table 1. Summary statistics for ‘Fully Protective Occlusal Splint’ measurements (n = 100) . Splint dimension Mean Standard Mean ± 1SD Mean ± 2SD (mm) Deviation (mm) (mm) (mm) (Range that (Range that includes 68% includes 96% of individuals) of individuals) Disclusion at first molar 5.41 0.87 4.5 – 6.3 3.7 – 7.1 Lateral slide length 10.22 1.17 9.1 – 11.4 7.9 – 12.6 Lateral slide overjet 4.54 0.63 3.9 – 5.2 3.3 – 5.8 Protrusive path length 9.45 1.06 8.4 – 10.5 7.3 – 11.6 Protrusive path overjet 4.63 0.52 4.1 – 5.1 3.6 – 5.7 Thickness at first molar 4.28 0.61 3.7 – 4.9 3.1 – 5.5 Table 2. Stages and timing of ‘Formal Fully Protective Occlusal Splint Therapy’. SEQUENCE OF TREATMENT USUAL TIMING Formal Occlusal Splint Therapy involves 4 splint adjustments (SA) Over a minimum 3-month period with full counselling concerning Splint adjustment 1: 1–2* weeks after fit oro-facial and occluso-mandibular Splint adjustment 2: 2-3+ weeks after SA 1 habits during a minimum of 4 Splint adjustment 3: 3–4+ weeks after SA 2 splint adjustments Splint adjustment 4: 4–5+ weeks after SA 3 Recommend removing wisdom teeth, if necessary, after SA 4 if jaw comfortable *= 1-3 days after fitting if an acute TMD condition + = can be longer if the TMD condition is chronic LINICAL