Jaw relation-prosthesis

Faculty of Dentistry
Assuit university
3rd year student
Feb, 21, 2016
Jaw relations
Recording
Maxillo-Mandibular
Relations

Steps for making full denture
Primary impression
Primary cast
Secondary impression
Master cast
Trial denture base
Occlusion rims

Procedures of Recording
Maxillo-Mandibular Relations
1) Checking extension, retention, and stability of occlusion rim
2) Establishing proper facial contour
3) Orientation of the occlusal plane
4) Determination of vertical dimensions
5) Mounting maxillary cast according to face-bow
6) Registration of centric occluding relations
7) Registration of eccentric jaw relations

Checking extension, retention, and stability
Minimize the liability of recording wrong relationship
Due to :
* ill fitting bases
* Warpage of shellac trial bases

Extend to functional depth
Rounded and smooth
Fill the vestibule
Post dam area
Lingual extension
Hamular notches area

Maxilla
Upward and forward ……….... Post-dam
Downward…… border seal anteriorly
Buccal…….. Border seal posteriorly
Mandible
Downward and forward ……….... Posterior portion
Upward …… border seal anteriorly
Buccal…….. Border seal posteriorly

Alternate vertical pressure on premolar region
The base shouldn’t teeter

Establishing proper facial contour

Orientation of occlusal plane
Anterior occlusal plane influenced by:
* Esthetics
* Phonetics
Posterior occlusal plane influenced by:
* Anatomical land marks
* Condition of residual ridge

Anterior occlusal plane influenced by:
* Esthetics
* Phonetics

Posterior occlusal plane influenced by:
* Anatomical land marks
* Condition of residual ridge

Determination of vertical dimensions
Two measurable lengths of the face are important guides in
making maxillo -mandibular relation records and are referred to as
:
Vertical dimension of rest (VDR).
Vertical dimension of occlusion (VDO).

Vertical dimension of physiologic rest position (VDR)

Vertical separation of the jaws when the opening and closing
muscles of mandible are in a state of minimal tonic contraction
sufficient only to maintain posture

Physiologic rest position
The position assumed by the mandible when the head is in
an upright position, the muscles are in equilibrium in tonic
contraction and the condyles are in a neutral unstrained
position is the physiologic rest position of the mandible.

Vertical dimension of occlusion (VDO)
Vertical separation of the jaws when the teeth or occlusion
rims are in contact.

Interocclusal Distance (IOD)
Vertical separation of the jaws when the opening and closing
muscles of mandible are in a state of minimal tonic
contraction sufficient only to maintain posture.

METHODS OF DETERMINING )VDR(
1. FACIAL MEASUREMENT AFTER SWALLOWING AND RELAXING.
2. SPEECH
3. TACTILE SENSE
4. MEASUREMENT OF ANATOMICAL LANDMARKS
5. FACIAL EXPRESSION.

FACIAL MEASUREMENT AFTER SWALLOWING AND RELAXING.

SPEECH
• 1st method : Ask the patient to repeatedly pronounce the
letter ‘M’, a certain number of times. Distance is measured
immediately after the patient stops.
• 2nd method: keep talking to the patient and measure the
distance immediately after the patient stops talking.

TACTILE SENSE
• Instruct the patient to stand erect and open the jaws wide until
strain is felt in the muscles.
• When the opening becomes uncomfortable, ask him to close
slowly until the jaws reach a comfortable relaxed position.
• Measure the distance and compare it.

MEASUREMENT OF ANATOMICAL LANDMARKS
• Distance between the pupil of the eye and Rima oris and the distance
between anterior nasal spine and lower border of mandible is measured
using Willis guide.
• If both the distances are equal, jaws are considered at rest.

• FACIAL EXPRESSION.
• Patients jaw will be in rest position when he is relaxed.
• Skin around the eyes and chin should be relaxed.
• Nostrils are relaxed and breathing is unobstructed.
• Upper and lower lips have slight contact in one plane.

METHODS OF DETERMINING )VDO(
1. Pre-extraction records.
2. Phonetic : ( closest- speaking space)

Pre-extraction record
Profile photograph : profile photograph are made and enlarged to life
size . measurement of anatomic landmarks on the photograph is
compared with measurement of the same anatomic landmarks on the
face .

Profile silhouettes :- The word silhouettes means " outline "‫ـــ‬ An
accurate reproduction of the profile in silhouette can be cut out in card
board or contoured in wire

Radiograph : profile radiograph of positions of condyles in the fossae
with the teeth in occlusion

Articulated cast : A simple method of recording the vertical relation , as
well as size and shape of the teeth , is through the use of diagnostic cast
mounted on an articulator

Phonetic : ( closest- speaking space)
The vertical dimension can be established by using ” closest-speaking
space “
This technique measures the space when the mandible is involved in
physiologic function of speech
The patient says words beginning with the “ F or V “ to determine
position of maxillary anterior teeth , while position of the mandibular
anterior teeth is determined by position of the mandible when patient
says words beginning with the letter “ S “

Mounting the maxillary cast according to face-
bow record :-
Face-bow is a dental instrument that is used in the
prosthodontics . it transfers the relationship of maxillary arch
and temporomandibular joint to the casts. It aids in mounting
maxillary cast on the articulator.

Mounting the maxillary cast according to face-
bow record :-
-The condylar rods of the bow are positioned on a marked point 13 mm in
front of the canthus – tragus line
-The tip of infra-orbital pointer is positioned on the lowest part of infra-
orbital margin .
-The face bow fork is attached to maxillary occlusion rim . it is heated and
pushed into the labial surface of the maxillary occlusion rim , 3mm above its
lower border .
-Wings of the fork must be parallel to occlusal plane , and midline coincide
with the midline drawn on the maxillary occlusion rim
- Condylar rods released , and the upper cast is mounted on the articulator

Procedures of Recording
Maxillo-Mandibular Relations
1) Checking extension, retention, and stability of occlusion rim
2) Establishing proper facial contour
3) Orientation of the occlusal plane
4) Determination of vertical dimensions
5) Mounting maxillary cast according to face-bow
6) Recording of centric occluding relations
7) Recording of eccentric jaw relations

Recording the centric relation
-Centric relation: It is the most retruded
physiologic relation of the mandible to maxilla
, to and from which the individual can make
lateral movements
Centric occlusion: It is the relation between the
opposing teeth when the mandible is in centric
relation
CR is recorded after determination of VDO

Significance:
- it is adefinite position
- can be repeated and the only relation which can be
dublicated
- - occlusion is more stable if the teeth occlude with the
jaws are in CR

Methods of CR recording:
- 1- Static Method( check bites )
- 2- Functional Methods :
- A) Graphic tracing method
- B) Terminal hinge axis recording
- C) chew in functional generating records

Methods of CR recording:
- Static Method( check bites )
mandible should be in the most retruded position
use recording medium as :
1- softened wax
2-plaster of Paris
3- Zinc oxide eugenol paste

Technique for interocclusal record using
softened wax
( Check bite or wax wafet method )

A) Guide the mandible in centric relation
 Patient in upright position

A) Guide the mandible in centric relation
-insert occlusion blocks inside the mouth and guide the
patient to occlude in centric relation by various methods :
1- instructing patient to " let your jaw relax , pull it back and
close slowly on your back teeth "
2- instructing the patient to " get the felling of pushing your
upper jaw out and close your back teeth together "
3- instructing the patient to turn the tongue backward
toward the posterior border of the upper trial denture base
4- instructing the patient to tap the occlusion rims or back
teeth together repeteadly

B ) Mark Guidelines :
- Midline
- Canine lines

C) Locking the maxillary and Mandibular Occlusion blocks :
1- Two v-shaped grooves in occlusal surface of maxillary
occlusion rimin premolar region / not parallel to each other

2 - remove 2 mm. of wax from lower occlusion block and
replace them by softened wax

3- insert record bases and guide the patient to close in
centric relation until light contact between the anterior
sections of occlusion rims are made and VDO is restablished

4- remove occlusion blocks as one unit , chill in water
5- remove excess wax

D) verification of centric relation record :
 Occlusion blocks are re-inserted and mandible guided to centric position
 The mandibular wax projections shoud fit with the v-shaped grooves and
marked lines should coincide

Advantages :
1- decrease liability to displace soft tissue
2- equalization of pressure
3- simple method , no mechanical devices
Disadvantages:
1- difficulties in handling softened wax during record or possible distortion of
the record after it was made
2- must be checked several time

Jaw relation-prosthesis

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