The Michigan splint (synonyms: Michigan splint; splint therapy according to Ash and Ramfjord; splint therapy with the Michigan splint) is one of various so-called bite splints or equilibration splints used in dental practice. It is also used in modified forms and serves to harmonize the interplay of temporomandibular joints and masticatory muscles in order to subsequently make corrections to occlusion (tooth row closure), if necessary.
Indications (areas of application)
The treatment concept with a Michigan splint consists of freeing the lower jaw from its interlocking with the upper jaw, thereby enabling it to adjust itself in a position resulting from a relaxed muscular and temporomandibular joint situation, detached from the constraints imposed by the relief of the opposing teeth.
The described concept of an equilibration splint to cancel the occlusion is useful,
- To harmoniously adjust an uncertain final bite position preprosthetically (before provision of new dentures),
- To preprosthetically test a desired change in bite height,
- To reduce dysfunction-based pain in patients with myoarthropathy (MAP) preprosthetically at least, although in the aforementioned multifactorial clinical picture, the ideal of complete pain elimination is difficult to achieve,
- To readjust the function of the masticatory muscles and temporomandibular joints in a harmonious interaction and thereby eliminate established occlusal disorders by grinding-in measures or prosthetic therapy,
- To provide as little “work surface” as possible in bruxism (involuntary nocturnal grinding and pressing) by reducing the final bite contacts.
The procedure
Steps in the dental practice:
- Impression of both jaws
- Centric bite taking, if possible in the initial situation;
- Facebow transfer.
Working steps in the dental laboratory:
- Model fabrication;
- Transferring the models to an articulator (device used to simulate temporomandibular joint movement) according to the facial arch settings;
- Making the splint for the upper jaw from transparent plastic according to specific design specifications:
- The bite elevation required to accommodate the splint must be kept as small as possible;
- Plateau in the posterior region (SZB) with an occlusal field (field for contact with the lower jaw) of size 0.5 mm x 0.5 mm; the occlusal field safely excludes interference contacts. Only the supporting buccal (facing the cheek) cusp tips of the mandibular teeth can come into contact.
- The limitation of the occlusal field results from an anterior / canine guide reaching after 0.5 mm, which is set at an angle of 40 ° to 60 °, whereby all posterior teeth are out of contact even with slight lateral movement (sideways movement of the mandible), thus free of interference contacts.
- Small anterior plateau.
Working steps in the dental office:
- Insertion and fitting of the splint on the patient; rocking fit, not too tight, not too loose;
- Checking the occlusion contacts, if necessary grinding in pre-contacts;
- Control of canine guidance, which must proceed undisturbed by contacts in the posterior region;
- Informing the patient regarding the daily wearing time and expected duration of treatment, as well as behavior in the absence of symptoms;
- Arrangement of the first control appointment after a week at the latest, in case of acute pain symptoms even earlier.
