30. Devices for simulation of the mandible movements. Fixators and occludator.

whats in it

• articulators

• function

• occludators are classified as

• corrections done in the mouth

• phenomenon of the tmj

• 4 classes of the devices

What are articulators?

• It is a mechanical instrument designed to represent the TMJ and the joint members to

  which maxillary and mandibular casts may be attached to stimulate jaw movement

• -  Usually, this position is when there is maximal intercuspation or centric occlusion

function?

•  hold maxillary and mandibular casts in a determined fixed position

• -  to stimulate accurate jaw movements like opening and closing

• -  to produce boarder movements (extreme lateral and protrusive movements) and intra

  boarder movements

types of occludators

0. Occludators are classified as:

   1. Gypsum occludator (fixed)

   2. Occludators made of wire

   3. Occludator with limitative (restrictive) screw

   4. Modern occludators (Biocop-Orthomat)

Corrections in the patient’s mouth:

• Articulating paper is used, and trimming is later done

• -  Dentures made using occludators have reduced functional effectiveness as it does

  NOT represent the patient’s masticatory apparatus

• -  Most frequently observed problems when using these devices are preliminary contacts

  that may cause traumatic occlusion

0. Phenomenon of the TMJ and peculiarities: + aXIS

• -  The TMJ is described as highly incongruent

• -  This phenomenon is typical for humans only because of the well groups of

  defined teeth (incisors, canines, premolars, molars)

• -  All kinds of articulators follow Bonvills geometric triangle, where the

  bisector of the triangle is exactly 8.5 cm (this is the anatomical axis of

  rotation of the two heads of the condylar process)

• -  The real mechanical axis is 2.5 cm behind and under the anatomic axis of

  rotation

0. Classification of mechanical devices depending on the abilities of them: (class 1 and 2)

1. Class 1 (NON-adjustable)

• -  also known as hindge occludators

• -  Simple mechanical devices, only register the static position between upper and lower

2. Class 2 (NON-adjustable)

• -  Allow horizontal and vertical movements, without reproducing the movements of

  lower jaw

• -  Upper jaw contains a screw adjuster

  Further classified to:
  A – amount of eccentric motion only permitted by arbitrary values
  B – amount of eccentric motion only permitted by theory of arbitrary motion
  C – amount of eccentric motion permitted is determined by patient using engraving methods

• -  incisal guide pins run on an inclined plate in a fixed inclination

class 3

3. Class 3 (SEMI-adjustable)

- Allow horizontal and vertical movements

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- Reproduce the path of condyle guidance (with a mechanical model of the TMJ)

- Uses a facebow to relate to the patients TMJ Further classified to:

• adjustable incisal guide tables

ACRON TYPE (ACRON - CON IS AT THE BOTTOM BC CONDYLE IS ON BOTTOM)

- Very similar to the TMJ joint

- Are very precise with good occluso-

articulating relationships

- Glenoid cavity

Consists of:

spherical part: that resembles the condylar head (always from metal)

plate: resembling the glenoid fossa

- Can be made of metal or plastic

Biggest difference: the articulator is equal to human movement with the glenoid cavity located in the upper branch and the condyle in the lower branch

NON ACRON TYPE

- There are 2 basic types; Type 1:

- Mechanic joint looks like acron type however metal plate is different

- There is no anatomic curvature of the articular tubercle

- Plate is absolutely flat

Type 2:

- Very complex mechanism

- Contains 2 metal disks placed one into another

- Inner disk has a drilled hole containing a

cylindrical body (this is how the movement is made)

Biggest difference: the condyles are in the upper part and the glenoid cavity in the lower part of the instrument

class 4

4. Class 4 (Adjustable)

• -  Mechanical device that accepts data from 3D registers

• -  Allows independent adjustment of each condyle

• -  Duplicates the trajectory unilaterally

• -  Mostly used in severe and difficult cases of malocclusion

• condyles that are

  made of a acrylic dough which is contoured to make a preferred condylar guidance

  and incisal guidance