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Biomechanical occlusion in CMD II

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Development and change of occlusion concepts

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Introduction

Craniomandibular dysfunction (CMD) is a common disease of the stomatognathic system. According to a recent estimate, about 3 million Germans suffer from the consequences of CMD. The local effects and the effects on the entire body are numerous and complex, just like the reasons for the dysfunction.
When fitting a dental prosthesis, it is important to ensure that it is optimally integrated in order to prevent the occurrence of CMD. Parameters were recently drawn up to enable trouble-free fitting.
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Aesthetische Zahnbehandlungen
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Weitere Informationen unter www.mvz-kopfzentrum.de

The problem of dynamics

Occlusal surfaces that are fabricated according to purely static wax-up concepts, e.g., those of Lundeen and Thomas, have interferences in the dynamics of mandibular movements, which are located again and again at the same occlusal site (Polz 2013).

Occlusal design according to Payne & Lundeen or Thomas is only partly similar to natural occlusal surfaces (Polz 2013).
Polz identified recurrent morphological patterns in the occlusal surfaces, which he linked with mandibular movements. This meant that the biomechanics of the occlusal surfaces could be deciphered.

Principles of biomechanical occlusion

Dynamic occlusion

The principles of biomechanical occlusion relate mandibular movements to the natural morphology of the occlusal surface.
The morphological alignment of the cusps to each other is perfectly aligned with the craniomandibular system. This means that a dental prosthesis must have natural morphology if it is to function not only statically but also dynamically.

The occlusal compass (according to Polz)

  • illustrates how a tooth must be constructed so that it can be integrated in the craniomandibular system.
  • describes and sketches the direction of mandibular movements in occlusal relief (similar to the arrow point tracing in a patient).
#pic#

The movements of the mandible can be defined by color coding and the main linear direction. The excursive movements are traced from the centric position as far as the guided final position. The illustration of the occlusal compass is identifiable on the occlusal surfaces from the upper to lower jaw in exactly opposite direction.
  • Left and right lateral movement (latero- and mediotrusion) is recognized. There are several intermediate movements between these, namely, protrusion and latero-protrusion.
  • Immediate side shift and re-surtrusive laterotrusion are also listed as borderline movements.
  • There is a fissure in the regions of the greatest masticatory movement, which enables the antagonist cusp to slide out of the opposing tooth without contact.
  • There are therefore no tilting forces (working or balancing contacts) that could harm the temporomandibular joint, the masticatory muscles or the periodontium.
  • Exception: latero-protrusion - it always goes toward a cusp incline.

Color code

  1. Black = protrusion (forward movement)
    • Both condyles move downward and forward.
    • The maxillary 1s with the mandibular 1s and mesial halves of mandibular 2s take over guidance in the anterior region.
    • Opening in vertical direction with disclusion of the posterior teeth
    • The stamp cusps of the mandibular posterior teeth "leave" their antagonists in mesial direction, whereas the stamp cusps of the maxillary posterior teeth leave their antagonists in distal direction.
  2. Blue = laterotrusion (working movement, mastication side) and green = mediotrusion (balancing movement, non-mastication side)
    • The working or laterotrusion condyle moves laterally (Bennett movement).
    • The balance or mediotrusion condyle moves forward, inward, i.e., towards the middle, and downward.
    • The angle produced to the protrusion plane is the Bennett angle.
    • On the laterotrusion side, the maxillary and mandibular canines usually take over guidance (canine guidance) but the premolars may contribute to guidance (= segmental guidance) and in some cases the posterior teeth are deliberately used also for guidance (= group guidance).
    • On the laterotrusion side, the stamp cusps of the mandibular posterior teeth leave the antagonists in buccal direction whereas the stamp cusps of the maxillary posterior teeth leave the antagonists in lingual direction.
    • On the mediotrusion side, the stamp cusps of the mandibular molars leave their antagonists in mesiopalatal direction whereas the stamp cusps of the maxillary molars leave their antagonists in distobuccal direction.
    • Balancing facets can occur on the mediotrusion side.
  3. Red = re-surtrusive laterotrusion
    • Borderline movement in the occlusal compass
    • The condyle describes a simultaneous movement laterally, backward (re-) and upward (sur-). It therefore influences the direction of the movement and the disclusion of the posterior teeth.
    • The stamp cusps of the mandibular posterior teeth "leave" their antagonists in buccal and slightly distal direction whereas the stamp cusps of the maxillary posterior teeth leave their antagonists in lingual and slightly mesial direction.
  4. Red = immediate side shift
    • Combines all defined types of side shift, such as progressive, early and distributed side shift
    • Borderline movement in the occlusal compass
    • Influences the mediotrusion side
    • The first millimeters of the condyle from centric position should be noted these are relevant for occlusion in the molar region.
    • On the mediotrusion side with immediate side shift, the stamp cusps of the mandibular molars leave their antagonists in palatal and mesiopalatal direction whereas the stamp cusps of the maxillary molars leave their antagonists in buccal and distobuccal direction.
  5. Yellow = latero-protrusion
    • Anterior-canine guidance
    • Because of the small angle between protrusion and mediotrusion, illustration of medio-protrusion is omitted in the occlusal compass.
    • In latero-protrusion, by contrast, the angle between laterotrusion and protrusion is nearly 90° In this movement, the path of the stamp cusps leads directly over the cusps of the antagonists.
    • All movements lead through or along the fissures provided the central fossa is present as centric position.
    • On the latero-protrusion side, the stamp cusps of the mandibular molars leave their antagonists in mesiobuccal direction and the stamp cusps of the maxillary molars leave their antagonists in distolingual direction.
The canines are important for relieving the posterior teeth. Their long stable roots have many more receptors than other teeth. They program and regulate the muscle-controlled mandibular movements during mastication.


sources

  • Bauer A, Gutowski A (1984) Gnathologie - Einführung in Theorie und Praxis. Quintessenz Verlag, Berlin
  • Jordan RE, Abrams L, Kraus BS (1992) Kraus‘ dental anatomy and occlusion. Mosby Year Book, St. Louis, USA
  • Kornfeld M (1974) Mouth Rehabilitation. Vol.2. The C.V. Mosby Co, St.Louis, USA
  • Lotzmann U (1981) Die Prinzipien der Okklusion. Verlag Neuer Merkur GmbH, München
  • Polz M (2013) Zahnantomie, Zahnfunktion und biomechanische Okklusion. Quintessenz Zahntech 5:592-604
  • Schöttl W (1978) Das TMR-System. Quintessenz Verlag, Berlin
  • Stuart CE (1984) Die gnathologische Aufwachstechnik. Quintessenz-Verlag, Berlin
  • Thomas PK, Tateno G (1982) Die gnathologische Okklusion. Quintessenz Verlag, Berlin