Jaw Relation Records & Techniques for RPD

McCracken's RP Prosthodontics; Stewart’s Clinical RP Prosthodontics.

Why to Record the Jaw Relations ?

•To establish and maintain a harmonious relationship with all oral structures and to provide a masticatory apparatus that is efficient and esthetically acceptable.

• To ensure that all the effects of occlusal loading be distributed as evenly as possible to all supporting structures capable of receiving the force.

To best control the undesirable effects of rotational or torquing forces on the prosthesis.

To prevent any deflective contacts of the teeth during centric or eccentric closures as these can produce pathological changes in the supportive structures or in the neuromuscular mechanism that controls mandibular movement.

Jaw Relation Records – A Review

• Vertical Jaw Relations:Rest Vertical Dimension ‘RVD’

Occlusion Vertical Dimension ‘OVD’

• Horizontal Jaw Relations:Centric Relation

Centric Occlusion

Eccentric Relations

Protrusive relation

Lt & Rt Lateral relations

• Face bow Registration.

The vertical distance between two selected points, one on the fixed (maxilla) and one on the movable member (mandible).

Vertical Jaw Relation

Vertical Jaw Relations

Rest Vertical Dimension ‘RVD’

Occlusion Vertical Dimension ‘OVD’

Inter-occlusal Distance / Free way Space

Rest Vertical Dimension (RVD)Is the distance measured when the mandible is in the rest position.

Occlusal vertical Dimension (OVD)Is the distance measured when the occluding rims or teeth are in contact.

Vertical Jaw Relations

Inter-occlusal Distance

The distance between the occluding surfaces of maxillary and mandibular teeth when the mandible is in the rest position.

For a complete denture patient, it is the difference between RVD and OVD.

RVD – OVD = 4 mm

or RVD – 4 mm = OVD

Inter-occlusal Distance

In natural dentition it ranges from 2-4 mm in the premolar area - the Freeway Space.

Vertical Jaw Relations

If stable occlusal contacts are provided by the remaining natural teeth, the existing OVD and CO relation should be recorded.

For the patients whom one of the arch is edentulous or whom the opposing teeth do not provide stable occlusal contacts, OVD has to be measured as follows,

RVD – OVD = 3 - 4 mm

Altering the Existing OVDNormally the OVD of a partially edentulous patient is provided by the opposing natural teeth contact

and it should not be changed.

Unless,

Altering the Existing OVD

1. Symptoms of diminished OVD exist such as tired aching muscles, unexplained pain in the head and neck region, shortened nose-chin distance (appearance of premature aging).

2. Excessive Free way Space or ‘over-closure’ of the jaws.

Altering the Existing OVD

Wearing of the teeth does not mean that OVD should be increased – unless the free-way space is greater than 4mm.

How to alter the existing OVD

1. Confirm the loss of vertical dimension by taking history, cephalometric examination, and the presence of excessive free-way space.

2. Increase the existing OVD temporarily by fabricating an acrylic resin occlusal overlay appliance in maximum intercuspation, ensuring that 4mm of freeway space must exist.

How to alter the existing OVD

3. Restore the desired OVD permanently with the help of fixed and removable prosthesis (made simultaneously) only after the physiologic response of the patient to this appliance is positive.

Altering the existing OVD - a case report

Altering the existing OVD – a case report

Horizontal Jaw Relation

Centric Relation

‘the most retruded position of the mandible to maxilla at an established OVD’.

It is a bone to bone relation that is repeatable by the patient. It remains constant throughout life & during its recording cuspal relation of the teeth is not considered.

The maxillo-mandibular relationship in which the condyles articulate with the thinnest a vascular portion of their respective disks, with the complex in the anterior-superior position against the slopes of the articular eminences.

To record this position, the mandible

is directed superiorly and anteriorly

restricted to a purely rotary movement

about a transverse horizontal axis.

Horizontal Jaw Relation(Centric Relation)

Horizontal Jaw Relation

Centric Occlusion

‘the relation of the mandible to maxilla in the maximum intercuspation of the teeth’.

It is a tooth-tooth relation - a position of habitual closure.

Horizontal Jaw Relation

What to Record – C.R or C.O

In more than 90% of people, C.O is 0.1 - 2mm in front of the CR.

Horizontal Jaw Relation

What to Record – C.R or C.O

Centric Occlusion should be recorded whenever a patient requiring a partial denture has cusps on remaining natural teeth that can guide

the mandible back to this position,

otherwise,

Horizontal Jaw Relation

What to Record – C.R or C.O

C.R should be recorded, e.g., for distal extension RPD, or when the opposing arch is edentulous.

Methods of Establishing Occlusion for RPDArticulator or Static Technique

This method of formulating occlusion cannot be used without first clinically establishing the occlusal relationship of the jaws - by using record bases and occlusion rims attached to the RPD framework.

Methods of Recording Jaw relations:

Direct Apposition of Casts (Hand Articulation).

Use of Record blocks attached to the Framework.

Methods of Recording Jaw relations

Direct Apposition of Casts (Hand Articulation)

This method can only be used when sufficient opposing teeth

remain in contact to make the existing jaw relationship obvious.

Methods of Recording Jaw relations

Direct Apposition of Casts (Hand Articulation)

The occluded casts are secured together with the help of wooden sticks and sticky wax and mounted arbitrary on an articulator.

A face-bow record may also be used.

A clinical appointment is saved by using this method.

Methods of Recording Jaw relations

Record Blocks attached to the Framework

Recording jaw relations clinically are essential when,a. the remaining dentition does not provide sufficient occlusion.

Methods of Recording Jaw relationsRecord Blocks attached to the Framework

b. one of the arches is edentulous.

Methods of Recording Jaw relations Record Blocks attached to the Framework

Making the Record Block:After carefully verifying

the fit and occlusion of the RPD framework intra-orally and after performing the altered cast procedure, an auto-polymerizing acrylic resin base is usually attached to the framework saddle areas. A base-plate wax base may also be formed.

Methods of Recording Jaw relations Record Blocks attached to the Framework

A wax occlusion rim is then placed over the resin base, while considering the width and height dimensions of the natural missing teeth.

Methods of Recording Jaw relationsClinical Procedure:

1. The framework with the attached record block is first tried in the mouth for reconfirming the fit of framework.

2. The height of the wax occlusion rims are so adjusted intra-orally that 1mm of space exists between the opposing teeth & the rims. For two opposing rims, occlusal plane is adjusted on one of the rims, e.g., mandibular distal extension wax rim.

Methods of Recording Jaw relationsAdjusting the Occlusion rim

Methods of Recording Jaw relationsAdjusting the Occlusion rim

Additionally, adjusting the Occlusal Plane of the remaining natural teeth may also be indicated by ‘Enameloplasty’

Methods of Recording Jaw relationsAdjusting the Occlusion rim

Methods of Recording Jaw relations

3. The recording medium (wax or ZnO paste) is then placed on the mandibular wax rims while V notches are cut in the upper rim -

the patient is then guided in the desired C.O or C.R position.

Methods of Recording Jaw relations

Methods of Recording Jaw relationsIdentify An Inaccurate Record

Methods of Recording Jaw relations

4. Care must be taken to avoid any pressure being applied on the soft tissue under the record bases to avoid any inaccuracies.

Methods of Recording Jaw relations

Any pressure applied during recording the jaw relations will result in inaccurate mounting.

5. A face-bow record should also be taken for mounting the casts accurately.

The Face-bow / Ear-bow

is an instrument used to record the spatial relationship of the maxilla to some anatomic reference (transverse horizontal axis) and then

transfer this relationship to an articulator.

The registration obtained by means of a face-bow is called a

“face-bow record”.

To relate the maxillary cast to the condylar elements of the articulator at the same orientation that the maxillary teeth have to the mandibular condyles of the patient.

Why Use a Face-bow

As the teeth move during opening, closing, and lateral movements, the arc of closure of the teeth on the articulator and the patient’s mouth should remain identical to avoid any occlusal premature contacts.

The length of this arc is measured from the center of the condyle to the incisal edge or the cusp of the teeth.

As this record mounts the casts at the same angulations as the jaws are related in the mouth, the artificial teeth being placed on the cast can be visualized as they will actually look in the mouth.

How to Use a Face-bow

The steps of making this record can vary depending on the type of face-bow & articulator being used, however, following are the basic steps,

1. Preparation of the face-bow / bite fork.

How to Use a Face-bowLocating the ‘arbitrary’ Hinge Axis:

Place an indelible pencil mark 13 mm in front of the posterior margin of the tragus of the ear, on a line between the tragus of the ear to the outer canthus of the eye.

How to Use a Face-bow

2. Orientation of the face-bow to bitefork & reference points.

How to Use a Face-bow

The reference points for this orientation may differ depending on the types of face-bow being used.

How to Use a Face-bowUse of a Hinge axis Locator

Obtaining & Transferring the Face-bow Record

3. Orientation of face-bow to articulator.

Obtaining & Transferring the Face-bow Record4. Mounting the maxillary cast to articulator.

Use of an Ear-bow

Use of an Ear-bow

Thank you