Fixed pros Flashcards
What is an articulator?
A hinged mechanical device to which maxillary and mandibular casts are attached.
What is the aim of an articulator?
To reproduce as closely as possible the relationship of a patient’s maxilla to mandible in RCP or ICP.
- Some articulators allow relationship to be reproduced during opening arc and during lateral and protrusive jaw movements (functional movements).
2 reasons to use articulators?
- Diagnostic study casts during treatment planning.
- May facilitate laboratory technician appropriately shaped crowns, bridges and dentures with functional occlusal schemes.
4 types of articulator?
- Simple hinge.
- Average value.
- Semi adjustable.
- Fully adjustable.
Simple hinge?
plane line
average value?
freeplane.
define occlusion?
the way the maxillary and mandibular teeth come together.
What are the splints for bruxism called? Maxillary? Mandibular?
STABILIZATION splints.
- Maxillary: michigan splint.
- Mandibular: tanner appliance.
Simple hinge articulator (4)?
- Equivalent to holding casts in hands.
- Occlusal relationship only correct when casts are together.
- Opening arc is determined by hinge design and is the same for all casts mounted (different from that of patient).
- Lateral and excursive movements not possible.
Average value articulator (6)?
- Sufficiently accurate for reproducing ICP.
- Condylar incilnation is set by manufacturer and cannot be changed.
- Allow for some degree of protrusive and lateral movements.
- OK for posterior restorations where there is obvious guidance from OTHER teeth (ex. canines).
- Complete/ partial removable prostheses - balanced articulation.
- Movement of cast is NOT accurate to patient movement.
2 cases where an average value articulator may be used?
- OK for posterior restorations where there is obvious guidance from OTHER teeth (ex. canines).
- Complete removable prostheses - balanced occlusion.
3 things that can be adjusted and 1 that cannot be adjusted in semi- adjustable articulators?
- Adjustment of condylar inclination.
- Bennett movement.
- Bennet angle.
- Cannot adjust inter-condylar distance.
2 types of semi-adjustable articulators?
- Arcon (Denar).
- Non arcon (Dentatus).
What is an arcon articulator?
Condylar component is attached to the MANDIBULAR member of the articulator and glenoid fossa is attached to the MAXILLARY member.
What is a non-arcon articulator?
Condylar component is attached to the MAXILLARY component.
Is arcon or non arcon more anatomically correct?
Arcon (denar).
What are arcon articulators used for?
Fixed prostheses work.
What are non arcon articulators used for?
Removable prostheses.
What cases are semi-adjustable articulators used for (5)?
- Fixed prostheses (when group function and one of the teeth in group function will be part of the restoration).
- Multiple units (ex. involved in guidance).
- Re-organised occlusion (ex. increasing vertical dimension).
- Group function (teeth involved guide the mandible).
- Anterior guidance.
- Occlusal analysis.
2 things needed to mount maxillary and mandibular casts onto an articulator?
- Facebow registration.
- Interocclusal record.
Define terminal hinge axis
An axis through the centre of the head of both condyles when they are in the most POSTERIOR/ANTERIOR? and SUPERIOR UNSTRAINED position in the glenoid fossa.
Centric relation?
Maxillomandibular relationship INDEPENDENT OF TOOTH CONTACT in which the condyles articulate in the anterior superior position against the posterior slopes of the articular eminences - UNSTRAINED, PHYSIOLOGIC
What is the first tooth contact called when the mandible closes in the terminal hinge axis position?
Retruded contact position.
When would you use a simple hinge articulator as opposed to just holding the casts in your hand?
When there are unsupported posteriorly/anteriorly due to missing teeth. Would use WAX RECORD BLOCKS to achieve this.
Where is RCP relative to ICP?
Approximately 1mm posterior and inferior to ICP.
Why is RCP important?
Gives us space in a worn dentition within a functional envelope.
What is the theory of mandibular movement called?
Posselt’s envelope of movement.
Condylar inclination?
When a patient postures forward from a retruded or intercuspal position, the condylar head moved DOWN AGAINST THE ARTICULAR EMINENCE –> CONDYLAR ANGLE.
In what position do we want the condyle when we are recording the condylar angle?
Record position in RETRUDED and INTERCUSPAL (or slightly protruded) POSITION
What is a gothic arch?
When the most posterior position is ICP.
During a lateral excursion, what happens to the condyle on the working side? What is this called?
Moves LATERALLY –> BENNETT MOVEMENT.
During a lateral excursion, what happens to the condyle on the non working side? What is this called?
Condyle moves MEDIALLY, FORWARD AND DOWNWARDS –> BENNETT ANGLE.
Things we can change on a semi-adjustable articulator (3)?
- Bennett angle.
- Bennet movement.
- Condylar angle.
Things we cannot change on a semi-adjustable articulator (2)?
- Shape of the condylar movement (cannot have sigmoidal path - it is straight line).
- Intercondylar distance.
What is a facebow?
Calliper like device that records the relationship of the maxilla to the terminal hinge axis (position of condyle).
Bite fork?
Record position of teeth (maxilla).
Bow?
Record position of the terminal hinge axis (condyle)
Jig?
To link bite fork and bow.
Pointer?
- 3rd reference point, to align the teeth to the horizontal axis (frankfurt plane).
Where do you place the pointer?
- Incisal edge of lateral incisor or canine.
- If edentulous upper border of lower lip.
What is the distance to record from the pointer?
42mm
How should the bitefork come out?
To the side of the OPERATOR (right of the patient).
In denar articulator, how is the position of the condyles represented?
Position of the condyle represented by the EAR AXIS on the SLIDEMATIC EAR BOW.
Does dentatus or denar bite fork have more mechanical retention?
denar
What position do we want condyle in when taking interocclusal records?
relaxed retruded position OR intercuspal.
2 ways to record interocclusal records?
- Silicone registration paste.
- Beauty wax.
What must be recorded if you want to adjust the condylar angle, bennett angle and bennett shift on an articulator?
Static relations of:
- Left and right static lateral excursions.
- Protrusive.
4 things you must determine prior to preparing teeth for laboratory fabricated restorations?
- Pain from TMD?
- Unexplained facial pain?
- Chronic dental pain?
- Discomfort from mobile teeth?
OVD?
occlusal vertical dimension.
OFH?
Occlusal facial height.
FWS?
- Difference between POSTURAL POSITION (at rest) and OVD (measurement when teeth are together).
- Space between teeth ANTERIORLY when the patient is at rest.
- Normal 2-4mm.
- Postural position - OVD = FWS.
4 ways to measure FWS?
- Willis gauge.
- Mirror handle.
- Point on soft tissues and spring dividers.
- Gingival margins and dividers.
Best way to measure FWS in dentate patient?
- Gingival margins and dividers.
Comfortable closed position where the maximum number of natural teeth meet (5)?
- ICP/IP (intercuspal position).
- Maximum intercuspation.
- CO (centric occlusion).
- Muscular position
Muscular position?
Comfortable closed position where the maximum number of natural teeth meet in COMPLETE DENTURE PATIENTS.
- Patient has good muscle memory of how IP was when they were dentate.
Retruded position (5)?
- CR (centric relation).
- CRCP (centric relation contact position).
- RCP (retruded contact position).
- RAP (retruded axis position).
- Ligamentous position.
what do we consult when looking for prosthodontic definitions?
Glossary of prosthodontic terms ninth edition.
why is centric relation important (4)?
- CLINICALLY USEFUL, REPEATABLE.
- UNSTRAINED, PHYSIOLOGIC.
define retruded position?
When the mandible is in its most SUPERIOR, ANTERIOR position within the glenoid fossa (TERMINAL HINGE AXIS POSITION). When the mandible is elevated (closed), the first TOOTH CONTACT POSITION is called RCP, CR, CRCP, RAP or ligamentous position.
define retruded contact?
Contact of a TOOTH or TEETH along the RETRUDED PATH OF CLOSURE. (during closure around a transverse horizontal axis).
What is the relationship between rcp and icp?
the mandible closes around the TERMINAL HINGE AXIS and then is guided by the TEETH (usually with an anterior slide of 1-2mm) into ICP.
What must occur when providing restorations that do NOT interfere with the occlusion?
When conforming to the present occlusion, restorations should NOT interfere with the ANTERIOR SLIDE (1-2mm).
what is the difference between ICP and RCP (in mm)
about 1mm in 90% of people.
Why is the space between RCP and ICP useful?
RCP is a PHYSIOLOGICAL POSITION. Provides space in a FUNCTIONAL POSITION (mandible, joints, muscles not strained). Thus in TOOTH WEAR CASES where interocclusal space has been lost due to dento-alveolar compensation, this PHYSIOLOGICAL SPACE CAN GIVE INCREASE IN VERTICAL DIMENSION TO RESTORE ANY WORN SURFACES WHEN THERE IS NO SPACE IN INTERCUSPAL POSITION.
what approach do we take hen providing restorations?
FUNCTIONAL approach and not morphological (for posterior teeth).
What determines the guidance of the mandible?
- Teeth.
- TMJs.
- Masticatory muscles.
another term for TMJ?
ginglymoartrhoidal joint.
what innervates the TMJ?
Innervated by mandibular division of the tirgeminal nerve V3.
What supplies and drains blood to TMJ?
Supplied by superficial temporal branches of external carotid artery and vein.
what muscles help move the TMJ?
muscles of mastication (jaw opening and closing).
3 things that surround the TMJ?
- Connective tissue capsule.
- Intrinsic and extrinsic ligaments.
is protrusion functional or non functional?
NON FUNCTIONAL.
What guides the mandible forward (protrusion) in a class I incisor relationship?
INCISORS AND CANINES - ANTERIOR GUIDANCE.
What guides the mandible forward (protrusion) in a class II division 2 INCREASED OVERBITE incisor relationship?
when this patient tries to protrude, they HINGE OPEN.
What guides the mandible forward (protrusion) in a class II division 1 incisor relationship?
when mandible slides forward, the POSTERIOR TEETH guide the mandible
What guides the mandible forward (protrusion) in a reverse overjet incisor relationship?
when mandible slides forward, the POSTERIOR TEETH guide the mandible.
2 difference guidance for lateral excursion?
- Canine guidance.
- Group function.
What guidance for lateral excursion is more common in younger people? Why?
- CANINE guidance (as older canine tip and palatal surface become worn an lead to group function).
4 functions of ICP?
- Occlusal phase of mastication.
- Aids jaw stabilization.
- Supports soft tissues for oral seal during swallowing.
- Contributes to appearance.
At what point in the chewing cycle is ICP gained?
ICP is the position gained at the END OF THE CHEWING CYCLE (MAXIMUM FORCE IS EXERTED). Periodontium is loaded AXIALLY in ICP.
Why is ICP important when placing crowns?
Maintaining ICP helps avoid EXCESSIVE FORCES THUS MINIMIZING FAILURE (porcelain, post, core, root etc). Also helps avoid accelerated WEAR OF OPPOSING TEETH, TOOTH MIGRATION AND TOOTH MOBILITY.
What must be done prior to the fabrication of crowns?
OCCLUSAL EXAMINATION.
6 methods of examining the occlusion?
- Clinically.
- Aid of handheld casts.
- Articulating paper.
- Occlusion wax
- Radiographs.
- Wax record blocks (when there is lack of posterior support).
5 things to observe regarding the OCCLUSION in ICP when considering CROWN PROVISION?
- is there space for the restoration?
- Is this position reproducible/correct?
- How different is this to RCP (in 90% of people 1mm anterior to RCP).
- Is the FWS within a normal range?
- Functional relationships?
How may the FWS be affected in a patient with tooth wear?
- FWS may be INCREASED.
- However DENTOALVEOLAR COMPENSATION may occur, re-establishing the FWS and thus no space to build up teeth.
- Vertical dimension (FWS, dentoalveolar compensation, will index teeth be prepared).
- Parafunction (grinding, habits ex. pens, failed crowns/bridges/veneers?).
- Lateral Guidance (canine vs group function, balancing side contacts).
- Protrusive movements (anterior vs posterior guidance).
- Are occlusal adjustments required prior to tooth preparation? (ex. interferences, incisal plane, overerupted tooth).
There is incisor guidance for protrusive movements and you are providing crowns on the upper anteriors. Why is this important.
We want to ensure the palatal surfaces of the upper anteriors are copied as they guide the mandibular movement when the mandible postures forward. MAINTAIN GUIDANCE.
2 methods of copying the palatal surface of upper anteriors involved in guidance when providing crowns? (when upper anterior restorations involve the palatal morphology).
- Alternate crown technique of replacement (2 PHASE CROWN REPLACEMENT).
- Articulated models with a customized INCISAL GUIDANCE TABLE.
What is done when providing a crown for a tooth which has a balancing side contact (interference)?
Must remove the balancing side contact prior to crown preparation to ensure this is not replicated onto the final crown. reduce forces on crown and thus REDUCE FAILURE RISK.
Crowning a tooth which is the first contact when going from RCP to ICP?
Must remove the first contact prior to crown preparation to ensure this is not replicated onto the final crown. reduce forces on crown and thus REDUCE FAILURE RISK.
How do you transfer clinical information to the laboratory?
- facebow recording.
- Static movements recorded (ICP, protrusive, lateral).
- Articulators (semiadjustable - bennet angle, bennet movement, condylar angle).
- Limitations (of articulators).
4 instances when facebow recording is required?
- Multiple units involved.
- Teeth to be restored are CRUCIAL for mandibular movements/ guidance.
- You wish to create specific guidance.
- Reorganizing the occlusion
Method of taking better quality alginate impressions for crown provision?
SMEAR ALGINATE ON THE OCCLUSAL SURFACES (prevent air blows, thus excess stone on cast which alters occlusion).
What approach do you normally want to take with occlusion?
CONFORMATIVE APPROACH.
What occlusal approach may you take in cases with SEVERE TOOTH WEAR?
REORGANIZED APPROACH.
Define centric relation?
- A MAXILLOMANDIBULAR relationship INDEPENDENT OF TOOTH CONTACT in which the condyles articulate in the ANTERIOR-SUPERIOR POSITION against the posterior slopes of the articular eminences.
- UNSTRAINED, PHYSIOLOGIC relationship.
- CLINICALLY USEFUL, REPEATABLE.
What articulator is usually used for fixed prosthodontic work?
semi-adjustable
2 methods that can be done when upper anterior restorations involve the palatal morphology?
- Use alternate crown technique of replacement.
- Customized incisal guidance table.
How does a customized incisal guidance table work?
- Incisal pin is guided by MOLDABLE material which was ADDED when the cast had the ORIGINAL CROWNS.
- When the cast with new preparations is then placed and the crowns are waxed up, this should still allow the INCISAL PIN TO STILL CONTACT THE CUSTOMIZED INCISAL TABLE.
What is the conformative approach?
Recreating the occlusion we has when we did not have restorations even after restoration provision. do not want to change anything about the occlusion.
What is a reorganized approach?
- When we CHANGE the occlusion (either vertical or horizontal position).
- Ex. toothwear cases when we want to recreate a better tooth shape.
3 things used for facebow recording?
- Earbow.
- Bitefork.
- Transfer jig.
4 different mediums that can be applied to the bitefork?
- Beauty wax.
- Modelling wax.
- Grey aluwax.
- Composition
12 steps to recording a facebow?
- Soften wax in hot water, gently dry, fold in two layers and place it on bite fork ensuring to not cover the centre line.
- Place against the upper teeth and push it. DO NOT BITE. Ensure you have occlusal indentations of the INCISORS, PREMOLARS and MOLARS.
- Chill the wax in cold water.
- Try wax back in to ensure it is not distorted (does not move or rock).
- Measure 43mm from either the CUSP TIP OF THE UPPER CANINE or INCISAL EDGE OF THE LATERAL INCISOR to articulate the casts (3rd reference point).
- Use a SELF CENTERING EARBOW, ask patient to put this into their ears like they might do a stethoscope and push it firmly.
- Allow nurse to hold earbow and push it FORWARDS so that it slightly distorts the tragus and sits snuggly into the external auditory meatus.
- Position bitefork and ask patient to hold it using their THUMB on their LEFT hand (check that it is sitting correctly).
- Use TRANSFER JIG to join earbow and bite fork together. The numbers on the jig should be facing the OPERATOR. Flat part of vertical pin faces the patient.
- Use the reference plane locator to ensure in correct position and then TIGHTEN ALL 3 SCREWS.
- Remove everything by only loosening the TOP SCREW.
- Disinfect bitefork prior to sending it to laboratory.
2 GENERAL reasons why a semi-adjustable articulator may be required?
- To allow the relationship of the casts to be visualized in functional positions during the PLANNING stage.
- To allow the relationship to be changed (REORGANIZED) by the WAXING UP/ FABRICATION OF RESTORATIONS.
What does a facebow record?
The 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).
Why may a facebow be required?
To allow the casts to be mounted on a semi or fully adjustable articulator.
What is the relationship between ICP and RCP in natural teeth?
- ICP 1mm anterior to RCP in 90% of cases.
- RCP and ICP coincident in 10% of cases.
What is ICP called in edentulous patients?
Muscular position
What is overbite determined by in edentulous patients?
cuspal height
what is overjet determined by in edentulous patients?
varied and may be determined by SKELETAL RELATIONSHIP.
What are the balancing and working sides on lateral excursions?
- Balancing sides: non-working side (bennett angle - medial, forward, downward).
- Working side: side toward which the MANDIBLE MOVES IN A LATERAL EXCURSION (bennet movement - lateral)
What guidance may you have on protrusion of natural teeth?
- anterior guidance (contacting surfaces of anterior teeth limit mandibular movements).
- posterior guidance
Define balanced articulation?
The bilateral, simultaneous occlusal contact of the anterior and posterior teeth on EXCURSIVE MOVEMENTS.
how do you achieve balanced articulation?
Hanau’s Quint simplified (KxI)/(OPxCxOK)
- CUSPAL HEIGHT has an impact on overbite.
- COMPENSATING CURVES are required to achieve balanced articulation.
what plane is the occlusal plane parallel to?
alar tragal line
Do you use a facebow for removable pros?
- Usually no, as an average value articulator is used and the occlusal relationship recorded is not altered.
- In exceptional cases, then usually a Dentatus semi adjustable articulator.
