Fixed Prosthodontics
*Glossary of Prosthodontic terms (9th ed.) states occlusion as:
  1. the act or process of closure or of being closed or shut off.
  2. the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues.
Before we talk about occlusion, one must be familiar with various terminologies that are commonly used in Prosthodontic discussion. The following discussion will briefly deal with various terminologies in short. You can always click link to know the details of that particular concept. 

Centric Relation*

Centric relation (\sĕn΄trĭkrĭ-la΄shun\) acronym is CR; is a maxillomandibular relationship, independent of tooth contact, in which the condyles articulate in the anterior-superior position against the posterior slopes of the articular eminences; in this position, the mandible is restricted to a purely rotary movement; from this unstrained, physiologic, maxillomandibular relationship, the patient can make vertical, lateral or protrusive movements; it is a clinically useful, repeatable reference position. CR diagramatic representation The centric relation has been used in dentistry as a repeatable reference position for mounting casts in an articulator. To understand the concept of centric relation in a meaningful way, the basic anatomy of temporomandibular joint must be understood.

Centric Occlusion*

Centric occlusion (\sĕn΄trĭk a-kloo΄zhen\): is the occlusion of opposing teeth when the mandible is in centric relation; this may or may not coincide with the maximal intercuspal position; comp maximal intercuspal position.

Maximal Intercuspal Position*

Maximal intercuspal position \mak΄sa-mal ĭn΄ter-kus΄pal΄ pazĭsh΄an\: acronym is MIP; the complete intercuspation of the opposing teeth independent of condylar position, sometimes referred to as the best fit of the teeth regardless of the condylar position; comp, CENTRIC OCCLUSION.

Mandibular Movement

Mandibular movement can be categorised into various categories.  It occurs around 3 axes. These are
  1. horizontal axis
  2. vertical axis
  3. sagittal axis

Determining factors of mandibular movement

The determining factors of mandibular movements, we can call them, determinants of mandibular movement, are
  1. right and left temporomandibular joint
  2. anterior teeth of maxillary and mandibular arches
  3. the neuromuscular system

Organisation of Occlusion

The consolidated arrangement of the teeth in function is very important. There are three recognised concepts that describe the manner in which teeth should or should not contact in various functional and excursive positions of the mandible. These concepts are:
  1. Bilateral balanced occlusion
  2. Unilateral balanced occlusion
  3. Mutually protected occlusion

Occlusal Interference

The undesirable occlusal contacts that may produce mandibular deviation during maximum intercuspation or Mein and smooth Passage to and from the intercostal position are known as occlusal interferences. The occlusal interferences can be divided into:
  1. Centric occlusal interferences
  2. Working side occlusal interferences
  3. Non-working side occlusal interferences
  4. Protrusive occlusal interference

Occlusal theory

Functional Cusp

In a normal dentition, during centric closer, lingual cusp of maxillary posterior teeth and the buccal cusp of the mandibular posterior teeth make contact with the occlusal fossa or the marginal region of the opposing teeth. They grind food like a mortar during mastication: these cusps are known as functional cusps or centric holding cusps or supporting cusps.

Non-functional Cusp

On the contrary, the buccal cusp of maxillary molars and lingual cusp of mandibular molars do not contact opposing teeth. They work similar to the rim of pestle and prevent food from overflowing, and protect the buccal mucosa and tongue by keeping them away from the functional cusps.  Since these cusps do not make direct contact with opposing teeth, they are called non-functional cusps or non-supporting cusps.

Occlusal scheme

  1. Cusp-fossa arrangement
  2. Cusp-marginal ridge arrangement

Anatomic determinants and their effects on occlusion

There are several anatomic elements that have effect on occlusal morphology, they are:
  1. Condylar guidance
  2. Anterior guidance

For details of each topic, one can read the following references:
  1. Fundamentals of Fixed Prosthodontics 3rd ed. by Herbert T. Shillingburg, Sumiya Hobo, Lowell D. Whitesett, Richard Jacobi, Susan E. brackett. pages 18, 20, 340, 341, Quintessence Publishing Co, Inc.
  2. Glossary of Prosthodontics (9th ed.)

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