Quality Resource Guide l Intraoral Appliance Therapy in the Management of Temporomandibular Disorders 1st Edition 4 www.metdental.com Criteria for optimum treatment effects include: 1. Stable and retentive. 2. Bilateral equal intensity anterior and posterior occlusal contacts so that an environment of a stable physiological mandibular posture (typically in centric relation or adapted centric relation) is created. 3. Canine guidance in lateral and protrusive excursions of the mandible. 4. No distalizing contacts that could compress highly vascularized and innervated. retrodiscal tissues hence the occlusal surface of the appliance should be as flat as possible. Importantly, as pain, muscle activity and inflammation subsides, the resulting changes in maxillo- mandibular relationships must be compensated for by regular adjustment of the appliance. Most patients are advised to wear the appliance during sleep and/or when their activity prohibits conscious awareness of awake parafunctional behaviors such as clenching. With improvement, the patient may be gradually weaned off the appliance. However, some patients engage in sleep bruxism, a recognized oral motor behavior often associated with disturbed sleep. Long-term wear of an appliance while sleeping may be necessary in selected cases. If there is no improvement within the first 2-4 weeks after judicious use of the appliance, then the patient should be re-evaluated for other factors that may require a partial or complete reassessment of the management regime. Systematic review of randomized clinical trials for intra-oral appliances suggests that: 27,28 1. Stabilization splints can reduce TMD pain compared to non-occluding splints in those subjects with more severe pain. 2. Stabilization splints in the short term were equally effective in reducing TMD pain compared to physical medicine, behavioral medicine, and acupuncture. Anterior repositioning appliances (Figure 2) are used less often because repositioning of the mandible over some time can result in irreversible changes to the occlusion such as bilateral posterior open bites. The purpose of these appliances is to alter the structural condyle-disc-fossa relationship to decrease adverse joint loading. Although compression of the retrodiscal tissues may be reduced by positioning the mandible anteriorly, the clinician must remember that the TMJ remains loaded when utilizing these devices. Recent studies looking at fluid film pressures within the TM joint in various circumstances raise a question as to the routine utility of this approach. 29,30 Systematic review of randomized clinical trials for intra-oral appliances suggests that: 27,28 1. Anterior repositioning and soft splints have some evidence to suggest efficacy in reducing TMD pain compared to placebo controls. 2. Anterior repositioning splints are at least equal to or more effective in treating TMJ clicking and locking than stabilization splints. An anterior bite plane or anterior discluding device (Figure 3) is usually a segmental appliance that occludes only with anterior teeth. No particular closure position is dictated; a full range of motion is permitted on a flat surface. Functionally, the patient will gravitate to occluding on the appliance in a centric relation position as long as there is no interfering contact. The rationale for the use of this device is the fact that separating the posterior teeth results in a decrease in the recruitment of the closure (elevator) muscles. Indications for use of anterior bite plane include: 1. When manipulation cannot be accomplished due to muscle splinting (guarding or protective co-contraction). 2. Management of painful masticatory musculature on an emergency basis. 3. When limited opening prevents other forms of intervention. The appliance must be used short-term or on an episodic basis to minimize the potential for re-eruption or supra-eruption of the posterior teeth and/or intrusion of the anterior teeth. A systematic review of randomized clinical trials for intraoral appliances suggests that anterior bite planes demonstrate modest evidence of efficacy for headaches and inconclusive evidence of effectiveness compared to stabilization intraoral appliances for TMJ pain. 27,28 Effects of Intraoral Appliance Therapy The mechanism of intraoral appliance therapy has long been debated. Some of the commonly mentioned mechanisms of action are: increasing the vertical dimension associated with the thickness of material utilized; protection of the dentition and/ or supporting structures from excessive loads; redirection of the forces; alteration of sensory input from the mechanoreceptors in the periodontal ligaments; cognitive awareness of what the individual is doing with the teeth (behavioral changes); change in mandibular position/condylar position; providing elements of occlusal contact that may be lacking due to missing or malposed teeth; and a placebo effect. 25,31 Figure 3 Anterior bite plane intraoral appliance. Figure 2 Anterior repositioning intra-oral appliance.