صناعة

Horizontal Jaw relations

صناعة اسنان / د . هند (م 8 - 9)
ثاني اسنان موصل
د . هند (م 8)
(750)

Each condyle moves about 3 axes

Vertical

Sagittal

Horizontal

• The most retruded physiologic relation of the mandible to the maxillae to and from which the individual can make lateral movements. It is a condition that can exist at various degrees of jaw separation. It occurs around the terminal hinge axis
•






Centric occlusion: it is tooth-to-tooth relationship dictated by bone to bone relationship.
Maximal intercuspal position: is a maxillomandibular relationship determined by tooth-to-tooth relationship.

Eccentric relation any relation of the mandible to the maxillae other than centric relation
Protrusive relation is the relation of the mandible to the maxillae when the mandible is thrust forward
Right & left maxillomandibular relation are the relations of the mandible to the maxillae when the mandible is moved either to the right or left side

Movements of the mandible

Hinge like movement used in opening & closing the mouth for introduction of food & crushing brittle food

Protrusive movement used in the grasping & incision of food

Right or left lateral movements use in the reduction of fibrous food











Bennett movement: The bodily side shift of the mandible which when it occurs may be recorded in the region of the rotating condyle on the working side

“Hinge Axis” (Horizontal Axis)

Is repeatable when the condyles are maximally seated in Centric Relation: & is then called the “Terminal Hinge Axis”


Jaw manipulation about the posterior border of movement in the initial 20-26mm of opening is about the terminal hinge axis (opening about the hinge or horizontal axis with the condyles in Centric Relation)

Border movement

A average movement in sagital plane
4-1 terminal hinge movement (border movement)
1-6 opening exceeding hinge movement (border movement)
6 maximal opening
4 retruded contact position or maximum intercuspation
4-3 tooth contact from centric occlusion in straight protrusion following cingulae of maxillary anterior teeth
3-2 edge to edge contact
2-5 protrusion of mandibular anterior teeth beyond the maxillary anterior teeth
4-5 guided by tooth contact (intra border movement)
5 contact in maximum protrusion
5-6 movement from maximal protruded contact to maximal opening
B horizontal movement area
C movement in three planes







4
5
2
3
4-1
1
6

Importance of centric jaw relation (Significance)

It is learnable, repeatable, and recordable position which remains constant throughout life.
It is a reference position from which the mandible can move to any eccentric position and return back involuntarily.
It is the start point for developing occlusion.
Functional movements like chewing and swallowing are performed in this position
It is a reliable jaw relation, because it is bone to bone relation.

Requirements for making centric relation record:

to record the correct horizontal relation of the mandible to the maxillae.
to exert equalized vertical pressure.
to retain the record in undistorted condition until the casts have been accurately mounted on the articulator


Methods used to make centric relation record :
1. Functional (chew in) :
The Patterson technique and the Needles – House technique. Both are based on same principle. The patient produces a pattern of mandibular movements by moving the mandible to protrusion, retrusion, and right and left lateral.

The Needles – House technique uses compound occlusion rims with four metal styli placed in the maxillary rim. When the mandible moves with the styli contacting the mandibular rim, the styli cut four diamond shaped tracings. The tracings incorporate the movements in three planes, and the records are placed on a suitable articulator.


Diamond-shaped marking made on the mandibular rim. (MP maximum protrusion, MLL maximum left lateral, MRL maximum right lateral, CR centric relation).

The Patterson method In this method used wax occlusion rims. A trench is made along the length of mandibular rim. A 1:1 mixture of pumice and dental plaster is loaded into the trench. When the patient moves his mandible, compensating curves on the mixture will produced, and the height of the mixture is also reduced. The patient is asked to continue these movements till a predetermined vertical dimension is obtained. Finally the patient is asked to retruded his jaw and the occlusal rims are fixed in this position with metal staples;

2. Graphic method :

The graphic methods record a tracing of mandibular movements in one plane, an arrow point tracing. The apex of properly made tracing presumably indicates the most retruded relation of the mandible to the maxillae from which lateral movements can take place.
Graphic methods are either intraoral or extraoral, depending upon the placement of recording device. The extra oral tracing is preferable because it is more accurate, visible and large.

Intraoral tracing

3. Tactile or inter occlusal check record :
• The tactile or inter occlusal check record method is referred to as a physiologic method. The normal functioning of the patients properioception and tactile sense is essential in the making of an accurate record.
The records are made using a recording medium (impression plaster, zinc oxide eugenol, impression compound and wax) between the occlusion rims. The patient closes into the recording medium with the lower jaw in its most retruded position and stops the closure at a predetermined vertical relation. This method has advantage of causing minimal displacement of the recording bases in relation to the supporting bone.

INDICATIONS of Tactile or inter occlusal check record :

1- Abnormally related jaws.
2- Displaceable, flabby tissues.
3- Large tongue.
4- Uncontrollable mandibular movements.
5- It can also be done for patient already using a complete denture.

A number of methods have been described to assist the patient in retruding his mandible :

• Instruct the patient by saying : “let your jaw relax, pull it back, and close slowly and easily on your back teeth.”
• Instruct the patient by saying :”get the feeling of pushing your upper jaw out and closing your back teeth together.”
• Instruct the patient to protrude and retrude the mandible repeatedly with the operator holding the finger lightly against the chin.
• Instruct the patient to turn the tongue back ward toward the posterior border of the upper denture.(disadvantage displacing the mandibular record base by the action of the elevated tongue).


Tilt the patient head back, the tension of muscles under chin make protrusion more difficult.
Palpate the temporalis and masseter muscles to relax them.
Boo's series of stretch exercise:
a- Open the mouth wide and relax.
b- Move the jaw to the left and relax.
c- Move the jaw to the right and relax.
d- Move the jaw forward and relax, in series of movements.
The results to be expected are for the patient to be able to follow the dentist's directions in moving the jaw to centric relation and the desired eccentric positions.

Registering Centric Relation

Occlusion rim notched to aid stabilizing the record bases

Preparing Occlusion Rims

Place 3 widely separated lines between the rims in the centric position (mid line & canine eminences)
Check that record base heels(rims do not touch)
Ensure record CR is repeatable

Registering Centric Relation

Two sharp “V”-shaped notches in the molar/premolar area of each sided wax depth 1-2 mm

Too Shallow

1-2 mm
Ensure adequate notch depth

Registering Centric RelationB.

Place Alluwax into a 1-2mm slot in maxillary rim
Fill to slight excess
Ensure wax is dead soft
Hot water bath for softening (use care not burns patient mouth)

Keep Wax Neat

Registering Centric Relation
Stabilize mandibular record base using index fingers on the flange (or in a recess in the rim) and the thumbs under the symphysis

• Hold position until set 1-2 min

• Remove both rims together
• Chill and separate

Mounting the Mandibular Cast

Place wax rims together, lute with sticky wax - 4 spots


Increase the height of incisal pin 1 mm, invert articulator

Mount the mandibular cast with mounting plaster

Return the incisal pin to contact when rims contacting without centric record
Occlusion rims should be touching evenly, over the entire occlusal surface
Do not alter incisal pin after rims closed to contact
• Otherwise, position of correct vertical dimension can be lost

Protrusive Records

Balanced occlusion
Used to set the condylar guidance
Protrude a minimum of 5-6 mm
Registration material placed bilaterally, posterior to the canines
Patient closes with mandible positioned anteriorly

Protrusive Records

Material must inter digitate with the opposing “V-shaped” notches
Wax is removed, chilled
In articulator : the Condylar elements are released from hinge position, Instrument protruded, and the records approximated.

Eccentric relation record :

The purpose of these records is to adjust the articulator to simulate the eccentric movements (lateral and protrusive) of the mandible to the maxillae. This adjustment permit arrangement of the teeth in balanced occlusion. When the protrusive eccentric record is made on Hanau articulator, the following formula is used to obtain an acceptable lateral inclination for lateral movement record,
L=(H/8)+12
L :lateral condylar inclination in degreeas obtained from formula.
H :horizontal condylar inclination in degrees as established by the protrusive relation record. .