Articulators

Articulators

1. Articulators
•Dental articulator is an instrument or mechanical analogues of the
TMJ & the upper & lower arches, advice to which casts of the upper
and lower dentate or edentulous jaws can be attached for
reproducing jaw relation and movement of the lower jaw relation to
the upper.
•Purpose of an articulator:-
•*To hold the maxillary & mandibular cast in a determined fixed
relationship.
•*To stimulate the jaw movements like opening & closing.
•*To produce border movements (extreme lateral & protrusive
movements)
Prof. Abdullateef Haidar
[email protected]

2. Uses of an articulator:-
•*To diagnosis the state of occlusion in both the natural &
relationship dentitions.
•*To plan dental procedures based on the relationship
between opposing natural &artificial teeth .e.g. evaluation
of the possibility of balanced occlusion.
•*To aid in the fabrication restorations & prosthodontic
replacements.
•To correct & modify completed restorations.
•*To arrange artificial teeth

3. Uses of an articulator:-
•* The simplest form of articulator consists of two arms or
bows united by a hinge. This type of instrument enables an
accurate record of a single static relationship between the
jaws to be maintained. And the only movement can be
made is an opening and closing one about the hinge. It's
known as a simple hinge articulator.
•* There are types of articulators. These articulators vary
considerably in their capacity to stimulate jaw movement
and relationship

4. * Classification of dental articulators:
•The design of articulators have been based on :-
•1-Theories of occlusion Bon will theory
• Conical
• Spherical
•2-based on the types of inter occlusal record.
•3- based on the ability to stimulate the jaw relation.
•4 based on the adjustability of articulator

5. Various types of articulator. Are used by the dentists or
laboratory technicians. Posse it has classified articulators
into 3-groups:- based on their design :-
•1- Simple (hinge) articulators
•2- Average (Mean) value articulators
•3- Adjustable articulators
•a- Simple adjustable
•b- Fully adjustable

6. 1- Simple hinge articulator
•articulator* It consists of two arms or two metal forms on bows united by hinge
mechanism. To these arms the casts could be attached.
•Simple hinge articulator

7. •2- Average value articulatorBon will's anatomical
articulation was based on the theory that the distance between the
condyles and mid incisal point of the mandible was an equilateral
triangle of 4 inch side. A sliding ring and spring mechanism about the
horizontal "condylar" element allowed for opening and protrusive
and lateral

8. •Gritman produced an articulator having the
condylar guides inclined at 15 to the horizontal, to
allow for the effect of articular eminence in joint
activity.
•Gysi (simplex) articulator produced with incisal
pointer.
•The Gysi (simplex) articulator, which was produced
condylar guidance in recognition of the form of the
glenoid fossa and was provided with an incisal
guide pin and an incisal table set at a fixed value of
60.
•
*
The incisal guidance mechanism was an important
development

9.  
2- Average value articulator

10.  
3- Adjustable articulators:
•* There are: - (A) Simple (semi adjustable) and (B) Fully
adjustable articulators as the following description:
•A) Simple or semi adjustable articulator.
•* This type depend on face bow transfers and protrusive
condylar path obtain from the patient mouth. While the
lateral condylar path is adjusted according to an arrange
value by special formula (Hanaue formula):
• H
•L = -------- +12
• 8

12. * Face Bow:
•
*
Face Bow: it is caliper-like device which is used to record
the relation ship between the inter-condylar axis and either
the maxillary and mandibular arch.

*
This relationship can be record or transferred to an
articulator, so that casts of patient's jaws will assume the
same relationship to the hinge axis of articulator as that of
the upper or lower jaw of the patient to inter-condylar
axis.
•
*
Two types of face bow exist:
•1- Simple (arbitrary) face bow
•2- The hinge axis (kinemetic FB(

13. •
*
The face bow consist of (U) shaped body (frame) which is
large enough to extend from the TMJ about 5-7.5cm in
front of the face. The face bow have condyles indicators
(rods) touch the condyle region and this is the fork which
touch to the occlusal rim the condyle rod position in front
of the external auditory meatus 13mm on the line extend
from the outer cantus of eye to the top of the tragus.
•
*
The body of the face bow carries a joint for securing a
fork having an off set rod attached and another for orbital
pointer.
•* The face bow have the functions of locating the hinge axis
and related the maxillary cast to this axis, and then to the
facility of the mounting of the upper cast.

14. •* Face Bow:

17. ..
•Mounting the casts

18. Mounting the casts

19. Dental Materials
Acrylic Resin
•Acrylic is the most commonly used polymer for denture
base, it is lightweight and esthetically can be accepted.
Acrylic is composed of chain of Methacrylate molecules
linked together to give polymethyl methacrylate (PMMA),
and it is either Heat Cure Acrylic or Cold Cure Acrylic.
•This is supplied as liquid and powder which are mixed
together to be reacted and produce hard substance
(denture base).

20. This is supplied as liquid and powder
which are mixed together to be
reacted and produce hard substance
(denture base).
Powder composed of : 1) PMMA
beads (polymer).
Initiator (benzoyl peroxide).
Pigments + Fibers some times.

21. •Liquid composed of : 1) Mathylmethacrylate
(monomer).
•2)Cross-Linking agent.
•3) Inhibitor (hydroquinone). 4)Activator (in cold
cured acrylic).
•Requisites for Dental Acrylic resin:
•1- Biologic Consideration That it should be tasteless,
odorless, nontoxic and have nonirritating to the oral
tissues. It should be insoluble in saliva and have resistance
to microbial growth.
•2- Physical Properties: The resin should posses adequate
strength and resilience to resist biting or chewing forces,
excessive wear. It should be dimensional stable and include
thermal changes.
•;-
Prof. Abdullateef Haidar
[email protected]

22. •Requisites for Dental Acrylic resin:
•3- Esthetic Properties: The material should have sufficient
translucency to be compatible with the appearance of oral
cavity and also it should be Radio-opaque with x-ray.
•4- Handling Characteristics: It should be easily to mix,
shaped, cured and insert. The final product should be easy
to polish and could be repair easily if it is fracture.
•5- Economic Consideration: It should have low cost and
should not require complex equipments.
•6- Overall Performance of Methacrylate: Although the
mathacrylate fulfill these requirements reasonably well, no
resin till now met all the mentioned requirement.

23. •Manipulation:
•The powder and liquid should be mixed together in
a ratio 2.5:1 by weight and 3:1 by volume as
polymer/monomer ratio.
•The correct ratio is important because if we use
high rate of powder, not all the polymer (powder)
will be wet by monomer (liquid), so the acrylic will
be granules. And if the liquid in high rate there will
be shrinkage of the acrylic base due to uncomplete
polymerization. So the more monomer
more shrinkage.

24. •Activation and Curing:The mode of activation and curing of
the resin mixture is either cold (self curing acrylic) or hot
(heat curing acrylic) according to the acrylic type
•1- Heat Cured Acrylic Resin: There are many method for
polymerization acrylic resin, but the conventional method is by using
hot-water bath container for 7hr at 70
0
C , then 3hr at 100
0
C. This
method can be used faster, also there is Microwave energy method,
it is widely used for construction complete and partial denture.
•2- Cold Cured Acrylic Resin (Self Curing): This type does not need
external heating because it should be self curing and polymerization.
It is end with inaccurate size so it will decrease the retention of the
denture base also it is more porous, less resistance to the abrasion,
has allergic reaction (more residual monomer). So it is consider as
less strong than heat cured acrylic. It is not used to construct
complete or partial denture due to its disadvantages, but it can be
used in orthodontic appliance, repairing of dentures, relining and
when ever strength is not needed.

25. •Glass Transmition Temperature (Tg):
•The temperature at which there is an abrupt
increase in the thermal expansion coff, indicate
increase molecular mobility. (it is character of glass
structure) when the Tg below the glass structure
loses its fluid characteristics and has sufficient
resistance to deformation, in other word it mean
softening temp. and this temp. apply for glass,
acrylic resin, waxes.

26. •Properties of Acrylic:
•1) The Tg of self cure is 90
0
C and 105
0
C for heat cure.
•2) Poor impact strength.
•3) Resist fracture of mastication.
•4) Thermal insulator.
•5) Low specific gravity (not heavy).
•6) Radiolucent and could be radio paqe with metal foil strips.
•7) Absorb water (cold curing type is more).
•8) Good esthetic and color.
•9)Drying out of acrylic cause cracks.
•10) Less hardness in compare with gold or chrom-cobalt.
•11) Insoluble in the fluid that may be in contact with oral cavity.
•12) Insufficient manipulation and curing process lead to porosity
(gaseous porosity).

27. •Heat Activated Acrylic Resin:
•Heat-activated or heat-cured acrylic resin used in fabrication of
nearly all denture bases. It need thermal energy for polymerization,
that will provided using water path or microwave over or other type
of heat and pleasure to reach the material to complete
polymerization.
•Composition: As it discussed before that it composed from powder
and liquid ,and the powder (polymer) consist of spheres of
polymethylmeth acrylate and small amount of benzyl peroxide (the
initiator). The liquid consist of un polymerized (methylmetha crylate)
with small amount of hydroquinone as inhibitor to prevent
undesirable polymerization or setting of the liquid during storage.
Also the liquid or monomer consist of Glycoldimeth acrylare base
used as cross-linking agent by the double bound per molecule.
•The storage of acrylic is recommended for limited time and
temperature, because its properties will change within the time.

28. •Polymer-Monomer Interaction:
•When powder and liquid are mixed in the proper proportion, a
workable mass is produced after passing different stages:
•1- Sandy stage. 2- Sticky stage. 3- Dough stage (workable). 4-
Rubber stage. 5- Stiff or Hard stage.
•According to ADA specification No.12 the mixture require at least
5min to reach the dough stage which is the workable time, so we
should consider this time during the manipulation process.
•Polymerization Cycle:
•The heating process used to control polymerization is
called the polymerization cycle or curing cycle. This process
should be controlled to avoid porosity or bubbles inside the
denture base which may be happened by the effects of
uncontrolled temperature (boiling of monomer).

29. •Chemically Activated Acrylic Resin:
•It also called Auto polymerizing Resin or Cold-curing
or Self curing. The addition of tertiary amine
(dimethyl-para-toluidine) to the liquid (monomer),
the tertiary amine will work to decompose of the
benzoyl peroxide when mixing the powder with the
liquid.
•So that the fundamental difference between heat
and cold curing acrylic is the method of dividing the
benzoyl peroxide which is the initiator or reaction.