Maxillmandibular Relation

 Maxillmandibular Relation

 "Jaw relation is defined as, ‘’ any relation of the mandible to the maxilla’’  which may be one of the three relations

,Orientation jaw relation ‘Facebow

Vertical jaw relation

Horizontal jaw relation

 Orientation jaw relation ‘Facebow’

This record gives the angulations of the maxilla in relation to the base of the skull. The plane of maxilla maybe tilted in some patient while the plane of mandible will not be altered because it articulates with the base of skull

Hence, the maxillary tilt will altered the relationship of the maxilla to the mandible during different movement

So, It is necessary to do orientation jaw relation before carrying out other jaw relation by face bow.

  Vertical jaw relation

The length of the face as determined by the amount of separation

Factors affecting vertical jaw relation

Teeth: act as occlusal vertical stops

Musculature:  be in a state of minimal tonic contraction

Vertical jaw relation can be recorded in two positions

 Vertical dimension at rest position

 Vertical dimension at occlusion

Both these relations should be recorded 

In a normal dentulous patient, the teeth do not maintain contact at rest

The space between the teeth at rest is called the ‘’ free-way space’’

The free-way space exists only at rest

The vertical dimension at occlusion should always be 2-4 mm lesser than the vertical dimension at rest

Vertical dimension at rest

The length of the face when the mandible is in rest position

This is the position of the mandible in relation to the maxilla when the maxillofacial musculature are in a state of tonic equilibrium

It is essential to record the vertical dimension at rest as it acts as a reference point during recording the vertical dimension at occlusion

VD at rest = VD at occlusion + free-way space

( VD – vertical dimension)

Methods can be used to measure the vertical dimension at rest

Facial measurements after swallowing and relaxing

Tactile sense

Measurement of anatomic landmarks 

Speech

Facial expression

We will explain only  the first method

Facial measurements after swallowing and relaxing

The patient is asked to sit upright and relax

Two reference points are marked, on the tip of the nose and the tip of the chin

The patient is asked to perform functional movements like wetting his lips and swallowing

The patient is instructed to relax his shoulders

Once the patient performs the above mentioned movements, his mandible will come to its physiological rest position

The distance between the two reference points is measured when the mandible is in its physiological rest position

    Vertical dimension at occlusion 

The length of the face when the mandible is in occlusion 

Recording of Vertical dimension at occlusion

Mechanical methods:

 Ridge relation

 Pre-extraction records

 Measurement from former dentures

Physiological methods

 Using wax occlusal rim

 Physiological rest position

 Phonetics

 Aesthetics

 Swallowing

 Tactile sense 

 Patient’s perception of comfort

Only phonetic method we will discuss

Phonetics 

This involves observing the movements of the oral tissues during speech and more importantly listening and analyzing the speech of the patient 

The Max. and Mand. Show a relationship during speech

Used to determine the vertical dimention

Two common methods of phonetics 

 Silverman’s closest speaking space

 The ‘F’ OR ‘V’ AND ‘S’ speaking anterior tooth relation

Silverman’s Closest Speaking Space

Measures the vertical dimension when the mandible is in function

This differs from the Niswonger’s and Thomson’s method

When sounds like ch,s,j are pronounced, the upper and lower teeth reach their closest relation without contact

This minimal amount of space between the upper and lower teeth in this position is called the Silverman’s closest speaking space 

This space indicates the vertical dimension of the patient

The ‘’F’’ or ‘’V’’ and ‘’S’’ speaking anterior tooth relation)

The incisal guidance is established by arranging the anterior teeth on the occlusal rim before recording the vertical dimension at occlusion

Horizontal jaw relation    may be

Centric relation

eccentric relation

Centric relation