Tutorial 3 - preliminary jaw registration

Question 1

What is the reason for undertaking this stage?

Answer 1

To enable you to articulate your primary casts.
The purpose of articulation is to enable you to accurately study the patient’s occlusion, on an articulator, whilst designing his/her denture.

Question 2

When articulating dentures, what are we looking for?

Answer 2

Over-eruption of teeth - is there room to fit an oppoasing tooth? If there is no opposing tooth, this may naturally cause the opposing tooth to grow further down.

Interdigitation - is there room to place denture components such as rests and clasp arms where you want them? It involves the alignment and positioning of teeth in such a way that the cusps of the upper teeth (typically the molars and premolars) interlock or “interdigitate” with the cusps of the lower teeth when the jaw is closed.

Question 3

what is maximum intercuspation?

Answer 3

maximum intercuspation: upper and lower teeth are in the fullest, most stable contact with each other

Question 4

There are 2 different clinical techniques for recording the preliminary jaw registration.

Answer 4

Methods:
If there IS a definite position of maximum intercuspation
If there is NOT a definite position of maximum intercuspation

The one used depends upon the number and position of remaining natural teeth. You need to determine whether or not there is a position of maximum intercuspation.

Question 5

How is this method of jaw articulation carried out?

there IS a definite position of maximum intercuspation.

Answer 5

1. Place the upper wax occlusal rim in the mouth and trim it until maximum intercuspation is re-established. (Natural tooth to tooth contact).
2. Then, remove from mouth and repeat with the lower wax rim (if there are 2 rims).
3. Now, put both wax rims in the mouth simultaneously and trim until maximum intercuspation re-established. (Natural tooth to tooth contact).
4. Cut grooves in the rims with a wax knife
5. Record position of maximum intercuspation using Zinc Oxide Eugenol paste or softened wax. check not allergic to this can be messy process.

Question 6

How is this method of jaw articulation carried out?

there is NOT a definite position of maximum intercuspation,

Answer 6

Generally though, where there is no definite position of maximum intercuspation you will need to record the relationship of the maxilla to the mandible in the retruded position, because it is a reproducible position.

You may need to determine the vertical dimension at which you will record the jaw registration if you are lacking natural tooth to tooth contacts.

Question 7

what is a vertical dimension determination?

Answer 7

Vertical Dimension of Occlusion refers to the vertical height between the upper and lower jaws when the teeth (or dentures) are in maximum intercuspation.

According to the BSSPD, another definition is “a measurement of the face made between any two selected points, one above and one below the mouth, usually in the mid-line”.

Question 8

Exaplain how we would carry out the vertical dimension determination.

Answer 8

To determine the patient’s rest vertical dimension (RVD) - ie “The vertical dimension with the mandible in the rest position”. This is done with a Willis Bite Gauge or a pair of calipers. Your patient needs to be sitting upright, with their head unsupported.

To determine the occlusal vertical dimension (OVD). The occlusal vertical dimension you are aiming for will usually be 2 to 4mm less than the value you obtained for rest vertical dimension. Therefore, RVD – OVD = 2 to 4mm. the value for RVD should always be greater than the value for OVD in completed dentures

Question 9

once we have done the vertical dimension determination, what shall we do?

Answer 9

When trimming our wax occlusal rims in the case where there are no natural tooth to tooth contacts:

1. Firstly establish the patient’s RVD then trim the wax rims until you obtain the desired value for OVD (2-4mm less).
2. Then take your record using ZOE or wax as before, but in retruded position
   3 disinfect the wax occlusal rims before sending them to the laboratory.

Lab instructions are:
“Please use jaw registration record to articulate the primary casts”. If special trays have not already been constructed these will also need to be requested.

YOU will then survey the casts and design your denture.

Question 10

What is the nect stage after the preliminary jaw registration stage?

Answer 10

1. Confirmation of the design with your patient
2. Any necessary tooth preparations
3. Secondary impressions in special trays