Figure 1: Full arch bridge on teeth and implants. The lateral movement is guided by the canine.
Figure 2: After equilibration, the guidances are well shared on the whole posterior occlusal faces on the masticating side.
Figure 3: The real mastication reveals an overguidance on the second bicuspid
Figure 4: The spline connection withstands lateral forces during mastication in an optimal manner.
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Determining The Right Occlusal Scheme for Dental Implants
Marcel G. Le Gall, DDS
The lack of periodontal ligament around an osseointegrated implant has two important consequences:1
• The absence of periodontal receptors reduce the proprioceptive and discriminative capacity of the implants and hinders the mechanisms of avoidance generated by the central nervous system in the presence of occlusal interference.
• The reduced mobility of the implant accentuates the effect of the overload on the implant and peripheral bone.
These two factors complicate the manufacturing and occlusal adjustment of the implant prosthesis which should insure optimal functional efficiency without transferring to implant and bone interface the occlusal axial overload and excessive and/or uncontrolled lateral forces.
To prevent these problems, the contacts and dental movements during mastication and swallowing should be well known.2
However the classical occlusal concepts are only based on the patient’s lateral and protrusive movements when asked to bite down. Thus, only incisors and/or canine guidance are generally recorded, whereas during mastication the movement is inverted and posterior contacts and guides can be revealed.
These mandibular kinetics and position discrepancies have a real importance on implant prosthetics.
It is easy to demonstrate that only applying classical concepts ignores functional interferences on implant prosthetics,3,4 a result of which is amplified by the lack of mobility and the diminishing of deflecting reflexes on the implant.
The occlusal concept of practitioners must be modified in order to prevent such problems.
1. During the prosthetic lab construction:
• The clinical recording of functional parameters and the functional setting of articulators must be used to obtain an acceptable prosthesis for mastication.
2. At the clinical insertion of prosthesis:
• The clinical adjustment of the closure path must be accom plished to obtain equal intensity and simultaneous contacts in intercuspal position (e.g. by using an occlusal jig).
• Mastication on anterior and posterior prostheses must be simulated in order to adjust and obtain a harmonious posterior guidance.
This objective of optimal functional equilibrium must modify the treatment planning for implant placement, influencing the position, the orientation, and the number of implants, under the prosthesis and the overall optimal implant bearing surface.
References
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