What is a dental articular?
A hinged mechanical device to which maxillary and mandibular casts are attached, and which is intended to reproduce as closely as possible the relationship of patient’s maxilla to mandible in RCP or ICP.
Why use articulators?
- Diagnostic study casts during treatment planning
- Sometimes may facilitate the laboratory technician in making appropriately shaped crowns, bridges and dentures with functional occlusal schemes.
What are the types of articulators?
- Simple hinge (plane line)
- Average value (free plane)
- Semi adjustable
- Fully adjustable
What is this?
Simple hinge articulator
- equivalent to holding casts in your hand
- Occlusal relationship only correct when casts are together
- Opening arch of casts is determined by the hinge design and is the same for all casts mounted on this device.
What is this?
Average value articulator
- sufficiently accurate for reproducing ICP
- OK for posterior restorations where there is obvious guidance from other teeth
- Complete removable prostheses – balanced articulation
what is this?
Semi adjustable
- Mandibular condyle
- Used for fixed prostheses work often
- Multiple units
- Re-organised occlusion
- Group functions
- Anterior guidance
- Occlusal analysis
What is the terminal hinge axis?
An axis through both condyles when they are in the most superior and posterior unstrained position in the glenoid fossa
What is this movement known as?
Posselt’s envelope of movement
According to the Posselt’s envelope of movement the RCP (retruded cuspal position) sits posteriorly to the ICP (intercuspal position) by how much?
1 mm posteriorly, also more inferior to the ICP
The anterior position will allow for the central incisors to do what?
Come edge to edge
what does the MO stand for on the Posselt’s envelope of movement?
Maximum opening
When the patient postures forward, from a retruded position or an intercuspal position, the condylar head moves down against the articulator eminence, it does this with an angle called the?
Condylar angle, this is different in everybody which is dependent on your anatomy
Prior to preparing teeth for laboratory fabricated restorations you must determine whether there is;
1. Pain from TMD
2. Unexplained facial pain
3. Chronic dental pain
4. Discomfort from mobile teeth
Occlusal vertical position = OVD
Occlusal facial height = OFH
Free way Space = the difference between the postural position – OVD
What is the retruded position?
When the condyle is in its most superior, anterior position within the glenoid fossa (terminal hinge axis position) and the mandible is elevated, the first tooth contact position is termed the RCP, CR, CRCP, RAP or ligamentous position.
. Why would you use a facebow recorder?
To allow casts to be mounted on a semi/fully adjustable articulator
Why would you use a semi adjustable articulator?
- To allow for relationship of the casts to be visualised in a number of functional positions during planning stage
- To allow the relationship to be changed by waxing up or fabrication of restoration
- What does a facebow record?
Relationship of the maxillary teeth to the condylar head in a retruded position ie; when it sits within the glenoid fossa in a posterior superior position
- What are the steps taken in completing a facebow record?
- Using bite-fork (angle goes towards pts right) on upper part place wax
- Place on the upper teeth and ensure its in centre and press against the upper teeth (no biting) giving an occlusal indentation
- Use reference plane location on the incisal edge of the 3s and the it will make the reference point on the side of the face
- Use self centering earbow and adjust to place. Place the bitefork and ask the pt to hold it ensuring it is held in the right place
- Join the bite-fork and earbow using the jig
- Follow the number on the jig. Numbers should be the right way round and facing youself.
- bring down the earbow and fit int to the correct hole and secure. Then the earbow adjusted and engages. Tigthen the screws, before doing so, ensure all is in the right place
- How are casts mounted on the articulator?
- Facebow and interocclusal record
- Facebow: Calliper like device that records the relationship of the maxilla to the terminal hinge axis (position of condyle)
- Bite fork: to record position of teeth (maxillary teeth)
- Bow: to link bow and bite fork
- Pointer for 3rd reference point: to align teeth to horizontal axis (Frankfurt plane)
- What factors need to be considered when prescribing restorations?
- Pain from TMD
- Unexplained facial pain
- Chronic dental pain
- Discomfort from mobile teeth
