Finding the Centric Relation – The Kois Deprogrammer
Finding the centric relation might sometimes seem hard, but with appropriate devices, such as the Kois Deprogrammer it’ll become just obvious.
The centric relation (CR) can be defined as the physiological position of the condyle in the fossa, when centered and in the most superior and anterior position, and when the meniscus is correctly placed against the posterior incline of the articular eminence. It is also described as the musculoskeletal stable position when it coincides with maximum intercuspation (MI) and occlusal and temporo-mandibular joint (TMJ) stability. The correspondence of the CR and MI provides occluso-articular stability and avoids overloading. This is of utmost importance for preventing TMJ lesions related to occlusion.
Many studies concerning full-mouth rehabilitation associated with increasing the OVD have shown that it is preferable to plan such cases in a Centric Relation position – this being acceptable and reproducible. CR has been well-described in the literature and, although easy to understand, clinical success is often elusive. A partial list of appliances and techniques to find the CR, includes the Lucia Jig, the leaf gauge, and the bilateral manipulation technique.
However, anyone who has attempted to mount cases in CR knows that some patients can be extremely difficult to manage regarding accurate bite relationships.
The deprogrammer has been found to be an effective device for achieving these bite registrations.
What is a Kois Deprogrammer?
The Kois Deprogrammer is a removable, plastic appliance that covers the hard palate and creates a single point of contact between the lower central incisor and the anterior bite plane.
How to fabricate the Kois Deprogrammer?
The lower and upper jaw impressions should be taken with alginate paste
Then the casts are poured.
And trimmed appropriately.
Casts are then mounted in the articulator in the maximum intercuspal position (MIP). The face bow and bite records are not necessary.
The facial bow of the deprogrammer is made out of wire and extended from the most distal tooth on each side of the arch, in order not to interfere with any occlusal surface of the tooth.
The facial bow should be made so as to be adjustable for the dentist, in order to regulate the retention and stabilization of the deprogrammer inside the patient’s mouth.
Then the horseshoe palatal coverage is obtained with an acrylic resin and anterior platform opposing the lower central incisors is fabricated.
The platform should be trimmed to be 3 mm wide and parallel to the labial bow, and should disclude all remaining teeth approximately 1.0-1.5 mm.
In the end, the appliance is polished and ready to deliver to the mouth of the patient.
How to deliver the Deprogrammer?
After receiving the deprogrammer from the lab
The platform should be checked (Fig 10) in order to ascertain that it is not wider than 3 mm.
If it is wider then 3 mm, it should then be narrowed.
Then, the appliance should be placed in the mouth and checked to establish whether the insertion is passive.
Appropriate stabilisation is achieved by means of palatal plate accurately fitted to the palatal surface and by the labial bow.
There should be a separation of 1.0-1.5 mm between the lower and upper posteriors’ occlusal surface.
Then, the patient should lie back in the chair, and be asked to occlude on the appliance through the articulating paper and slide forward and back.
The excess of the acrylic platform palatal to the most retrusive contact should be relieved.
The contact on the platform should be narrowed so that it touches toward the midline of one of the lower incisors.
When the patient closes their mouth and the same initial contact is confirmed – the patient is deprogrammed.
Repeatability is the key criterion to determine when the patient is deprogrammed.
For how long should the Deprogrammer be worn?
It is worn until the necessary muscle deprogramming is accomplished (days or weeks if necessary, usually 2-4 weeks). For some patients, it may be necessary to wear the deprogrammer up to 24 hours per day (except when eating) for old muscle memory to be erased and become completely deprogrammed. It has been has shown that, in patients with a centric prematurity introduced for a short period of time, a percentage of them may take days or weeks to lose the muscular uncoordination in the muscles of mastication once the prematurity is removed. This explains why some patients will not deprogram instantly or in a few hours.
Confirmation of Deprogramming
The initial point of contact should be marked with articulating paper. This must be a single spot, and has to be repeatable and achieved spontaneously upon closing the mouth of the patient, not with any manipulation of the mandible.
When the patient closes their mouth and the same initial contact is confirmed – the patient is deprogrammed (Fig 19). Repeatability is the key criterion to determine when the patient is deprogrammed.
The Kois Deprogrammer has several uses:
1. It can be used as a diagnostic tool to determine if the mandible needs to move in the anterior or posterior direction to reach CR from the maximal intercuspal position (MIP).
2. It is an invaluable tool in diagnosing the three most common types of abnormal occlusal attrition: occlusal dysfunction, parafunction (e.g. bruxism), and constricted path of closure.
3. It can be used during bite registration. This procedure, with the Kois Deprogrammer in place, allows control of the vertical dimension of occlusion (VDO) during bite registration.
4. It facilitates finding premature contacts – i.e. any contact encountered during mandibular closure with the condyles in CR before reaching MIP. If occlusal adjustment needs to be obtained, the KD ensures control because the deprogramming will be maintained.
Are there any contraindications for the Kois Deprogrammer?
1. When structural problems of TMJ are suspected (positive load test) the Kois Deprogrammer is not indicated. In this case, the patient requires posterior support and a Michigan splint is indicated.
2. Periodontally involved lower incisors. In this case, consider splinting the mandibular anterior teeth or prepare a Michigan splint.
3. Patient is gagging. Consider reducing the acrylic palatal plate in order to avoid contact with the extensive part of the soft palate.