occlusion sheet # 3 - Suhaib Attieh

Occlusion lecture #3
By the date of 22/2/2011
Done by Suhaib Attieh
In this lecture we’ll take about face bows, occlusal relationship recording (centric & eccentric), mounting casts (review), programming articulator & pantographic tracing.
*Face-bow:
Definition: mechanical device that’s used to transfer the hinge axis from the patient’s mouth to the articulator. In other words it records the special position of the maxillary arch or the occlusal plane to the terminal hinge axis.
**terminal hinge axis is an imaginary line that passes through the two condyles & around which the mandible hinges (opens & closes). We use it in mounting our cast % programming our articulator. The difference between the transverse & the terminal hinge axis that the terminal hinge axis is the axis when the mandible in the centric position which is the last hinge axis & it’s the one that we record because it’s constant.
**face bow for sure is always applied to upper jaw.
Components of the face bow:
1- Transverse component.
2- Two adjustable arms.
3- White form.
4- Indicator which is the third reference point. This point differ between different types of face bows, ex. Some use the infra-orbital, the nasial or the ala of the nose as an arbitrary point away from the lateral incisor by 22mm.
Types of the face bow:
1- Kinematic face bow: indicates the exact position of the true hinge axis of the patient & we use it with a fully adjustable face bow.
2- Arbitrary face bow: indicates appoint that is very close but not exactly on the hinge axis & we use it with semi adjustable articulator which is more common to be used in clinics. Less accurate but sufficient to do a good prosthetic work & it’s very useful.






Types of the face bow according to the indicator point:
1- Whipmix face bow which use the nasial point as an indicator.
2- Hanau face bow which use the infra-orbital notch.
3- Denar face bow uses an arbitrary point that’s 22mm away from the lateral incisor which is located at the ala of the nose we mark the point then we adjust the bite fork according to it.
*centric relation:
Definition: it’s the position of the mandible in which the condyles are in the upper most position in the clinoid fossa & related anteriorly to the distal slope of the articular eminence. It’s a jaw to jaw relationship independent on teeth where the condyles are in the most superior anterior position. Another definition is the relation between the mandible & the maxilla when the condyles are in the avascular thinnest portion of the articular disc.
*centric occlusion: acquired occlusion, hapetual occlusion, hapitual centric or maximum intercuspation all indicates the same definition.
Definition: it’s _a teeth to teeth_ relationship in which the teeth are in the maximum interdegetation. There’s no stable one maximum intercuspation –as in the centric relation- because we may lose a tooth or more. So if we want to restore a tooth in the mouth, we take the centric relation to the lab & we’ll work on it.
*interocclusal records:
Definitions: are wax recordings of various mandibular positions used ether to mount the cast ore to adjust mechanical settings of the articulator. If it’s a centric interocclusal record (during the centric relation _where the wax shouldn’t be perforated_ & centric occlusion _where the wax must be perforated because of the maximum intercuspation_) it’s used to mount the cast. If it’s an eccentric interocclusal record (as in lateral & protrusive movement) it’s used to adjust the condyler guidance of the articulator.
**techniques of registration:
a- Register a centric relation of patient:
1-ungided method: in which you ask the patient to retreat the mandible as much as possible & then take a record but it’s the most inaccurate method.
2-bilateral manipulation: the bimanual manipulation where you use the two hands in order to put the patient in centric relation & it’s the most accurate. First of all we put the patient in supine position that allows the mandible to drop backward by gravity then you put both thumbs on the chin _where it exert a posterior pressure _ & the rest four fingers below the ramus of the mandible (which is easy when you’re behind the patient’s head)_ where they exert an upward pressure _ then you start small openings & closings until you see that movement is rotational & that indicates the position of the condyles is in the most superior anterior position.
3-chin point manipulation: using a single hand & it’s less accurate than the bilateral manipulation. Even that it’s also used by some dentists. In registration you put your thumb on the patient’s chin and use other fingers to push the mandible backward & upward which isn’t a suitable for the patient & may lead to muscle reflexes & makes it less accurate.
*But if it’s hard on the patient to remember the centric relation & he only can remember the centric occlusion we use a deprogrammer (we’ll take about it later on). An example of a simple deprogrammer is to put cotton rods between his anterior teeth & ask him to bite on. First there will be a fatigue in his muscles so you can manipulate the patient easier then he tends to forget the old position that he used to bite on in maximum intercuspation that’s what’s so called an anterior deprogrammer.
*to be sure that my centric relation record is the right one I must take three records two of which at least must be the same.
b- Register a centric occlusion of patient: very easy. We want the maximum interdegetation.

**materials used in registration:
1- Wax: not very stable in temperature.
2- Bite registration material as Silicon.
*lateral records:
They record the relation between the mandible & the maxilla in eccentric position of the mandible. They’re used to program the Bennett’s angle of the opposing side in the articulator. For example if we take right lateral interocclusal record we’ll get the left Bennett’s angle (remember that the working side in this case is the right & the nonworking is the left).
**registration of the lateral interocclusal records:
First of all we ask the patient to bite in the centric relation for example & we mark the midline. Then we ask the patient to close his mouth on the right side & we mark another point. We take the wax record to the already mounted casts & we change the settings of the left Bennett’s angle on the articulator (so that is an eccentric record used in programming the articulator).
**before reprogramming our articulator we must mount the upper & lower casts which is dependent on the centric relation so we can’t use the eccentric records unless we already used the centric record & mounted the casts
Q: would you mount your casts (during the synthesis of prosthesis) on the articulator in centric relation or centric occlusion?
A: that depends on the number of missing teeth. If we have only one missing tooth & we would make a simple crown for example, we mount in centric occlusion because it’s conserved & it’s the usual thing. But if we have many missing teeth especially posteriorly we may lose the centric occlusion so we depend on centric relation as in the case of complete denture where the patient has lost his teeth & his centric occlusion so we mount in centric relation. Also if we want to make a diagnostic cast for a patient to study his occlusion, intercuspation or interferences we mount in centric relation.
*steps of mounting on the articulator:
1- Mounting of the upper cast using face bow.
2- Mounting the lower cast using centric interocclusal record.
3- Programming the articulator using eccentric records.
*protrusive records are used to program the condyler angle of the articulator
*pantographic tracing:
Used to simulate the articulator to the condyler movements & it’s necessary to obtain a precise tracing of movement.
Consists of:
1- Two face bows one attached to the upper & one to the lower.
2- Six tables (two anterior & two laterals on each side) & six styluses to draw the mandibular movements on the tables. The orientation of these six tables gives us the three dimensional movement of the mandible.
The pantograph is used to program a fully adjustable articulator. It records all the movements of the lower jaw from the most retreated position to the most protruded one including also the lateral movements.
Occlusion lecture #3
For Dr. Suzan hatter
Done by Suhaib Attieh
Good luck