Jaws relation

Maxillo mandibular relation records

Record bases
Definition :
A record base or base plate is a temporary form representing the base of a denture. It is used in recording maxillomandibular relations and in the arrangement of the teeth.
Requirements :
should be rigid.
should be accurate.
should be stable.
the borders should be round & smooth as the borders of finished dentures.
should be thin at the crest ,labial & buccal slopes to provide space for tooth arrangement.

Occlusion rims

Definition : occlusion rims are occluding surfaces constructed on record bases or permanent denture bases to be used in recording jaw relations and for arranging teeth.
Requirements :
the position should be in the anticipated position of the artificial teeth.
it must be securely attached to the base.
the occlusal surface must be smooth and flat.
it should be contoured to support the lip and cheeks accurately.
all the surfaces should be smooth.


Uses :
The occlusion rims are used :
to establish the level of the occlusal plane.
to establish the arch form.
to record the maxillary mandibular relations.
for arrangement of the teeth.

Wax Rim

Wax rims are smooth and have a flat occlusal surface. They are about as wide buccolingually as denture teeth – wider in the posterior, narrower in the anterior
The occlusal rim must be centered buccallingually over and parallel to the residual ridge crest.
The anterior portion of the maxillary occlusal rim is labially oriented









The anterior wax rim height is 22-mm on the maxillary and 18-mm on the mandibular arch.
The width of the anterior rim is approximately 3- to 4-mm thick.
The width of the occlusal rim in the posterior region is approximately 8- to 10-mm thick.
The occlusal rim is properly sealed to the baseplate without any voids.
The posteriors of the occlusion rims are cut at a 30º angle to the occlusal plane

Orientation of occlusal plane

The occlusal plane is defined as the average plane established by the incisal and occlusal surfaces of the teeth".

Importance of orientation of occlusal plane

Anteriorly, occlusal plane mainly helps in achieving esthetic & phonetic.
posteriorly, it forms a milling surface, where tongue & buccinator muscle are able to position the food bolus onto it , and hold it there during mastication.

Incorrect of occlusal plane would hamper esthetics, phonetics, & mastication. It may affect stability of complete denture & ultimately result in alveolar bone resorption.

The vertical length of the maxillary occlusion rim

Anteriorly extend 2mm below relaxed lip& oriented to be parallel to inter pupillary line.
Posteriorly the vertical length and occlusal plane are made to be coincide with (Camper's line).
(Camper's line, ala-tragus line) line passing from the lowest point of the ala of the nose to the center of the tragus of the ear.









The vertical length of the mandibular occlusion rim
Anteriorly the level of mandibular occlusion rim with the level of the lower lip.
Posteriorly the vertical length of the rim with level of the retromolar pad.

In case of failure in orientation of correct occlusal plane, that can be discovered clinically in the try-in step of complete denture construction, we should correct the defect by the following;
If the defect occur in posterior teeth
• Remove all posterior teeth (premolars &molars, upper & lower ).
• Re-orient the occlusal plane.
• Take vertical & horizontal relation.
• Re-mount the casts & re-arrange the teeth.
• Remove all anterior teeth.
• Re-arrange the teeth.

Vertical relations

Vertical relations
Rest vertical dimension The distance between two selected points one on the fixed part (maxillae) and one on the movable part (mandible) when the maxillofacial musculature is in a state of tonic equilibrium.
Occlusal vertical dimension : the distance between two selected points one on the fixed part (maxillae) and one on the movable part (mandible) when occluding members (teeth) are in contact.





Rest vertical dimension The distance between two selected points one on the fixed part (maxillae) and one on the movable part (mandible) when the maxillofacial musculature is in a state of tonic equilibrium.
Occlusal vertical dimension : the distance between two selected points one on the fixed part (maxillae) and one on the movable part (mandible) when occluding members (teeth) are in contact.

There are many of factors that affect the measurement of vertical dimension which is:

• Patient must sit in upright position with head unsupported.
• Any tension should be avoided.
• Special attention and enough time should be given to those patients having neuromuscular disorder.
• No valid method for all patients, so it is advisable to use several methods and compare the result

Recording the rest vertical dimension (physiological methods):

Facial measurements (reference points)
Tactile sense (opening ------- closing)
Phonetics (em)
Facial expression (skin tone and the lips contour)
Anatomic land marks (Willis guide)

Anatomical Land Mark:

Measurement of a fixed landmark of the face by a special scale called the sorenson profile scale. The Sorenson Profile Scale measurement was taken by placing the nasion locator of the instrument firmly in the depression at the bridge of the nose and raising the chin seat until it lightly touched the most inferior and anterior border of the chin. Or by using Willis bite gauge which is designed to measure the distance from the pupil of the eye to the rima oris and the distance from the nasal spine to lower border of the mandible when measurement is equal the jaw at rest.

Recording the occlusal vertical dimension (mechanical methods):

• Pre-extraction records
• Profile photographs
• Radiography (cephalometric profile and the condyles in the fossae)
• Articulated cast
• Facial measurements
• Former dentures
• Edentulous patients (wax occlusion rims)

Evaluating vertical dimension

The inter occlusal distance (free way space) is the distance or gap existing between the upper and the lower teeth when the mandible is in the physiological rest position. It is usually 2-4 mm when observed at the position of the first premolars.
The closest speaking space is the closest relationship of the occlusal surfaces and incisal edges of the mandibular teeth to the maxillary teeth during function and rapid speech.

Patients tactile sense

Swallowing followed by relaxing (cones of a soft wax )
Phonetics (3, 33) (5,55) ( Emma )


Horizontal relations

Compensating Curve [ Glossary of Prosthodontic Terms]

• is the“antero-posterior curvature* (in the median [sagittal] plane) and the medio-lateral curvature** (in the frontal plane) in the alignment of the occluding surfaces and incisal edges of artificial teeth that are used to develop balanced occlusion.”
• “The curve introduced in the construction of complete dentures to compensate for opening influences produced by the condylar and incisal guidances during lateral and protrusive mandibular excursive movements-called also the compensating curvature, compensating curve”
• * = Curve of Spee in the natural dentition
• ** = Curve of Wilson in the natural dentition

Each condyle moves about 3 axes

Vertical

Sagittal

Horizontal

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

The lower incisor mesial point angle* scribes out the classical Posselt’s Envelope of Motion shape in the sagittal plane that is the extreme (maximum) border movement of the mandible limited by bone, ligaments, muscles and occlusal contact. Most functional movements are intraborder movements


* An envelope of motion will be scribed out by any location on the mandible (including the condyle) but although having the same characteristics, will have different proportions and size.

“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

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.
Significance
• It is a bone to bone relation in a vertical direction.
• In the absence of pathosis the relation is fairly constant throughout life.
• It can be recorded in acceptable limits
• It is used in determining the vertical dimension of occlusion.

• 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
• the most retruded relation of the mandible to the maxillae when the condyles are in the most posterior unstrained position in the glenoid fossae from which lateral movement can be made, at any given degree of jaw separation


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

When to Use Centric Relation

When entire occlusion being restored
No remaining posterior centric stops
When complete, fixed, or removable partial dentures involve the entire occlusion

When to Not to Use Centric Relation

Stable occlusion
No pathology
Posterior centric stops present
No valid reason to change
Use maximum intercuspation

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 :

Functional (chew in) :
The Patterson technique and the Needles – House technique are examples of the functional method. 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.



The Patterson method uses wax occlusion rims. A trench is made in the mandibular rim and a mixture of half plaster and half carborundum paste is placed in the trench. The mandibular movements generate compensating curves in the plaster and carborundum. When the plaster and carborundum are reduced to the pre determined vertical dimension of occlusion, the patient is instructed to retrude the mandible and the occlusion rims are joined together with metal staples.

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.

• 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 or the trial denture bases. 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.

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.
• instruct the patient to turn the tongue back ward toward the posterior border of the upper denture.
• instruct the patient to tap the occlusion rim or back teeth together repeatedly.
• Tilt the patient head back while the various exercises just listed are carried out.
• Palpate the temporalis and masseter muscles to relax them.

Registering Centric Relation

Occlusion rim notched to aid stabilizing the record bases





•
• Index fingers on the rim, thumbs under symphysis

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)

Registering Centric Relation

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

Too Shallow

1-2 mm


Thin Layer of Material

Too Thick

Check Record
Have patient close into record
Ensure smooth arc of closure, no horizontal deviations
Medium on sides of rim can causes deflection

Registering Centric Relation

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)

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

Registration Should be Sharp, Not Rounded

Registering Centric RelationMounting the Mandibular Cast

Ensure record is repeatable
Increase the height of incisal pin 1 mm, invert articulator
Place wax rims together, lute with sticky wax - 4 spots

Registering Centric Relation

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 interdigitate with the opposing “V-shaped” notches
Make at height greater than the established occlusal vertical dimension
Wax is removed, chilled
Condylar elements are released from hinge position
Instrument protruded, and the records approximated

Factors that affect the centric relation record :

Resiliency of the tissues supporting the denture bases.
Stability and retention of record bases.
The tempro-mandibular joint and its neuro muscular mechanism.
Technique employed in making the records.
Amount of pressure applied in making the records.
The skill of the dentist


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. The records are made in the same manner as for centric records, for lateral movement record, Hanu recommend the following formula :
L=(H/8)+12
L :lateral condylar inclination degree.
H :horizontal condylar inclination degree.

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