By: Dr. Leonard A. Hess, DDS
Clinical Director, The Dawson Academy
There is no topic more confusing and more provoking than changing vertical dimension of occlusion.
The reason is that every dentist has seen cases where it did not go very well, for the patient or the dentist.
Broken crowns, chipped incisal edges, new TMJ issues, muscle pain, and lost bite sensations are problems that can happen when things don’t go right when opening VDO.
The reality is this, opening vertical dimension is very easy. Understanding why, and how much is the hard part.
Because if you do not get it right clinical failures are waiting around the corner. And when we lack predictability, we lack profitability, and then dentistry is very stressful.
Myths Related to Vertical Dimension
1. VDO is Not Related to Comfort
If done correctly you can open VDO and the patient will not realize it has happened. Do it incorrectly and the patient will certainly be uncomfortable.
2. You Cannot Test Changes to Vertical Dimension with Plastic
Wasting time “testing vertical” dimension with a “nightguard” does nothing to make the process predictable.
3. Rest Position and Speech
Rest position and speech is not how you “find” vertical dimension in a natural dentition.
4. People Rarely Have a Loss of VDO Even in Cases of Extreme Wear
What Should You Be Concerned About When Opening VDO
1. Why are You in a Position to Open Vertical Dimension?
If you do not diagnose and treat the cause of the problem, your case will fail. Airway issues, acid issues, TMJ issues, and the worn dentition often go hand in hand. Diagnosis is paramount!
2. What is the Health of the TMJs?
Unstable joints lead to unstable occlusal changes. It is a gamble to make large changes to the occasion without diagnosing the health of the TMJs.
Many people with degenerative joint disease are hiding in plain sight. They have adapted to their poor joint health and no longer know any better.
However, opening VDO can cause sudden changes to their level of comfort.
3. What Esthetic Changes will be Needed in the Restoration of the Case?
Placing the incisal edges in the correct vertical and horizontal position (both maxillary and mandibular) is critical for occlusal plane development, esthetics, anterior guidance, envelope of function, and phonetics.
There will be a price to be paid in deformation if restorative material is placed in the wrong position.
What Types of Cases Often Require Opening VDO?
1. The Worn Dentition
2. Case With Extreme Lingual Wear
3. Cases Where Incisal Length Needs to be Added and the Disclusion Needs to be Kept Shallow
4. Occlusal Plane Issues
5. Deep Bites
Vertical Dimension is Related to Muscle
Your true vertical dimension happens at the level of the joint and muscles, the masseter, and the medial pterygoid.
As you grow and develop your vertical dimension is set as your teeth erupt and meet an opposing force, thusly in your MI position.
Things become complicated when there is a discrepancy between CR and MI in patients and you are opening VDO.
Broken crowns, periodontal complications, mobility issues, and tooth migration can all occur when VDO is opened in a non-repeatable joint position.
Opening VDO in CR eliminates these issues as the occlusion can be restored from a repeatable fixed point of rotation.
Using Centric Relation as a starting point often means gaining restorative space in the anterior while not opening VDO at the level of the joint.
This pivoting of the mandible into CR (in the muscular sling) is a true advantage as the muscle length is not increased or stretched.
If you would like to learn more about these topics
please accept my personal invitation to join us at The Dawson Academy.
