Pre-prosthetic Treatment Measures
Progressive destruction of the masticatory system leads to functional disorders of the muscles, TMJs, and periodontal tissues
. The vertical distances and horizontal relationships of the jaws are altered. The masticatory system adapts to the function that has been altered by loss of teeth or occlusal surfaces, but the malocclusions usually lead to hyperactivity of the muscles of mastication, which means that the normal neuromuscular program is disrupted. This results in neuromuscular coordination problems with avoidance or adaptive programs, giving rise to muscle diseases (myopathies) that also cause diseased change to the joint tissues.
Bruxism and myoarthropathies (muscle and joint diseases) are the clinical pictures that are triggered by impediments to occlusion.
A definitive prosthetic treatment can turn into treatment failure if the tissue parts do not have time to adjust to the newly reconstructed occlusal situation. Pre-prosthetic splint therapy aims to eliminate this disorder of neuromuscular coordination over a defined period of time and to carry out functional adaptation (Fig 11-24). In the process, the pain symptoms should be reduced
and the impaired mandibular position should improve.
The following considerations apply to prosthetic structures:
- They may only be fabricated once there are no functional disorders of the masticatory system. Otherwise, functional therapeutic measures (regrinding, centric relation splints, long-term provisional restorations) need to be taken.
- They should be fabricated in a fully adjustable articulator; the models are adjusted with a joint-related facebow record.
- They should be realized with maximal intercuspation in centric relation of the mandible. If necessary, splint therapy should be initiated as a pre-prosthetic measure to establish the precise centric position.
The objectives of splint therapy as a pre-prosthetic measure are to correct the static and dynamic occlusal conditions in order to protect the teeth against progressive attrition; to change the condyle-disc relationship; to evenly distribute the forces acting occlusally; and to produce neu-rophysiologic effects that reduce the increased muscle activity.
A splint should interrupt pathologic reflex paths by using flat splint surfaces to eliminate the occlusal disturbances in the neuromuscular control cycle of the masticatory system. Creation of the previous vertical distance eliminates sliding interferences and guides the musculature back to a normal functional sequence. If the enforced occlusal guidances are eliminated, muscular hyperactivity diminishes, the joints are relieved, and the pain symptoms of myoarthropathy disappear. The aim is therefore to restore the original occlusal position that will apply to the definitive restoration. The occlusal splints described in the following paragraphs are classified according to their pre-prosthetic treatment objective.
Occlusal splints are appliances with a flat surface for unimpeded relieving movements to treat a traumatic occlusion with eccentric faulty contacts due to tipping or migration of teeth and mandibular displacement. Decoding the faulty occlusion means that the centric relation of the condyles can be resumed, which is accomplished with re-trusion splints.
Occlusion-raising splints can be used to increase a reduced vertical dimension resulting from posterior tooth loss or generalized abrasion (Fig 11-25). As the occlusal position is restored, the muscles of mastication regain their normal working length.
Fixation centric splints fix a specified intercus-pation situation and are worn for a few months before definitive restoration work is started to establish an interference-free occlusion (Fig 11-26).
The masticatory muscle synchronizer is used for adapting the neuromuscular movement pattern, mainly in the mandible, as an occlusal splint with dominant anterior and canine guidance (Fig 11-27).
Occlusion rims are employed for orthodontic retrusion of the anterior teeth. They are mainly palatal plates with anterior occlusal platforms and a labial bar that are fixed to the maxillary molars with simple clasps.
The Shore plate is a chewing pathway appliance for treating muscular dysfunction in a fully dentate dentition.The chewing pathway is shaped in plastic autopolymerizing acrylic resin onto the vacuum-formed splint.