Thoughts on Occlusion

Contacts and occlusion remain the two most important concerns to Doctors according to many dental trade magazines. And while solid contact models provide a standard for proximal contacts, in many laboratories occlusion is less of a focus. Dental technicians are generally trained only to deal with ideal situations, which are not common. "In only slightly more than 10% of the population is there complete harmony between the teeth and the temporomandibular joints." (1)

Unfortunately, the concepts of Centric Relation / Centric Occlusion are considered by many to be 'advanced concepts' and not taught to most technicians even though this should be one of the basics. "The presence of an immediate or early lateral translation, or side shift, has been reported in 86% of the condyles studied" (2).

But understanding head and oral anatomy is not enough; there are other uncontrollable factors that affect the restorative process, such as the movement of teeth due to the periodontal ligament, TMJ dysfunction, or drifting /movement from temporization. Knowing that models and articulators cannot accurately represent all of the physiological conditions of the patient, the laboratory needs to have procedures to identify and work within these conditions

Starting with inspection and equilibration of the model, adjustments are made until wear facets meet, then excursive patterns are determined and outlined. Proximal contacts are fitted to the working model and confirmed on a solid model. Centric occlusion is established on the crown compensating for the periodontal ligament or temporization with a ribbon style of "feeler" gauge. The gauges are incremental and once the dimension is determined for a particular doctor it can consistently be repeated, assuring accurate occlusion at seating.

Excursive wear patterns are then found on the model. Time is spent studying the patterns because they give information on posterior disclusion, or TMJ conditions the patient may have. The crown is placed on the model and adjusted until all excursions are clear. Cuspid guidance is established unless contraindicated. We will make an incisal guide table for all cuspid restorations if provided for.

1. Posselt U: Studies in the mobility of the human mandible. Acta Odontol Scand 1952; 10 (suppl 10): 1-109.

2. Aull AE: Condylar determinants of occlusal patterns. Part I. Statistical report on condylar path variations. J. Prosthet Dent 1965; 15 : 826-835

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