Vertical Dimension

VD related to muscle

• Muscle always wins!

• Repetitive contracted length of muscle determines Mnd-Mx relationship

When teeth erupt up, the alveolar process erupts with it

• Teeth erupts unitl something stops them

Even rapid abrasive wear does NOT result in loss of VD

• VD is unrelated to comfort unless you go past a point

You can NOT unload the TMJ by increasing vertical dimension

Can increase the vertical at the anterior TWICE the amount of Vertical Condyle displacement

• • This is measured on the articulator

FALLACIES OF BITE RAISING:

• Gelb appliance: ppl thought of it as a means of "unloading a joint", but it actually made a step occlusion

  • • Intrude posterior teeth, anterior teeth with supraerupt (no stop)

Evidence for stability of Vertical Dimension

• • Measure from 2 points: Zygoma to CEJ junction changes, but occlusal plane stays the same

  • This is because increased length of alveolar process

  • Ortho experiment: Increased VD and measure bony landmarks, and 1-4 years later, the patient's will return to their previous VD

Okay to change vertical if it's NOT segmental, needs to be treated all around

Clinical Example:

• Changing VDO is rare occurance

• Only in worn dentition to eliminate pulp impingement and....

• Lengthening teeth can prevent envelope of function

• When there is a lot of wear, notice that there's usually longer alveolar process

  • • Usually needs crown lengthening

• When joints are health and signs of Instability exist, our condylar position is Centric Relation

Size of the orifice matters:

• Tight neutral zone if SMALL orifice

  • • TIGHT: cannot see as far back to PM/M, lips are thin

• Different inclination indicated

• There is NO standard inclination

Buccinator band: limiting factor on the size of the arch

• Determines Horizontal position and Inclination

• Lower band: weakest

• Tongue presses forward, lips press back

  • Teeth erupt until something stops them

  • Teeth have automatically come into their neutral zone with this

  • Tongue forced forward due to airway problem, THUS neutral zone is more inclined out

  • Tight lips, more retroclined

Tongue position:

• Lower 2nd molar: tongue is widest at this position

• Bulbous crown on buccal or lingual side can cause pain and movement of tooth based on neutral zone

• Can HELP with dentures being held in though!

Overjet, High Vault:

• Tongue can't rest in vault because of narrow high vault (airway problem)

• Can expand Mx palate

Cleft in Lip

Recording neutral zone:

• Can use compound