Fixed Prosthodontics Flashcards
Topics covered: facebows and articulators, the occlusal examination, combining removable and fixed pros
In which cases might a facebow record be required?
In cases where the use of a semi or fully-adjustable articulator is indicated.
For example:
- cases where you need to visualise a number of functional positions during the planning stage to reorganise the occlusion (e.g. tooth wear cases) by the waxing up or fabrication of restoration.
What position does a facebow replicate ?
It replicates the position of the maxillary teeth to the condylar head in a retruded position.
List the 4 main types of articulator:
- Simple hinge
- Average value
- Semi-adjustable
- Fully adjustable
What are the 2 different types of semi-adjustable articulator?
- Denar (arcon)
- Dentatus (non-arcon)
What is the difference between a Denar semi-adjustable articulator and a Dentatus semi-adjustable articulator?
Denar has a mandibular condyle and is used for fixed pros work
Dentatus has a maxillary condyle and is used for rem pros work
When would you use a Denar semi-adjustable articulator?
- For fixed pros work
- When there is group function and multiple fixed unit restorations that may influence this
- When you want to reorganise the occlusion with a diagnostic wax up
- When there is anterior guidance and fixed restorations that may influence this
- When you want to carry out occlusal analysis
- When you wish to create specific guidance
When would you use a Dentatus semi-adjustable articulator?
- Removable pros work
- Multiple units
- Re-organised occlusion
- Group function
- Anterior guidance
- Occlusal analysis
What is the terminal hinge axis?
An axis through both condyles when they are in the most superior and posterior untrained position in the glenoid fossa of the temporal bone.
In short - the terminal hinge axis is the position of the condyle
When is the position of the terminal hinge axis most important?
When we are relaxed.
When the patient moves forward from an RCP/ICP, the condylar moves down against the articular eminence.
What is this angle known as?
The condylar angle.
When moving into a lateral excursion, the condylar head moves medially, forward and downwards.
(a) What is this angle known as?
The working side condyle moves laterally.
(b) What is this movement known as?
(a) Bennett angle
(b) Bennett movement
What 2 elements do you need in order to mount casts on a semi-adjustable Denar (arcon) articulator?
Facebow
Interocclusal record
In a facebow recording, what is the bite fork used to record?
The position of the teeth.
In a facebow recording, what is the bow used to record?
The position of the terminal hinge axis.
In a facebow recording, what is the jig used to record?
The link between the bow and the bite fork.
In a facebow recording, what is the pointer used for?
Used to align teeth to horizontal axis (Frankfurt plane)
What can and cant be changed on a semi-adjustable articulator?
The condylar angle, Bennett angle, and Bennett movement CAN be changed on a semi-adjustable articulator.
The shape of the path, and the condylar distance CANNOT be changed on a semi-adjustable articulator.
What 4 things must be determined before preparing teeth for a lab fabricated restoration?
- Is there any pre-existing pain from the TMD?
- Is there any unexplained facial pain?
- Is there any chronic dental pain?
- Is there any discomfort from mobile teeth?
What is an average FWS?
2-4mm
What is centric relation?
Maxillomandibular relationship, independent of tooth contact, in which the condyles articulate in an anterior superior position against the posterior slopes of the articular eminences.
In this position the mandible can only make rotary movements.
The patient can carry out vertical, lateral, and protrusive movements.
Reproducible and clinically useful position.
What is centric occlusion?
The first contact point of the teeth when the mandible is in centric relation (centric relation contact point)
What is the retruded contact position (RCP)?
Also known as centric relation contact position.
The initial point of tooth contact during mandibular closure with the condyles in centric relation and the mandible in the retruded arc of closure.
What is occlusion?
Force management - prevents teeth, restorations, joints, PDL, and periodontium from breaking down.
What 2 reasons would you not conform a patients occlusion to centric relation?
As the mandible is positioned further back in centric relation it can cause:
- Aesthetic issues
- Can collapse their airway
Give 1 example of when the centric relation contact point is useful?
When reorganising the occlusion in anterior tooth wear cases - creates more space anteriorly.
What is the ligamentous position?
The ligaments determine where the condylar head sits in the glenoid fossa.
What is guidance determined by?
Teeth, TMJ, masticatory muscles.
What is the TMJ stabilised by?
Intrinsic and extrinsic ligaments.
Which nerve innervates the TMJ?
The mandibular division of the trigeminal nerve.
Where does the TMJ gain its blood supply?
The superficial temporal branches of the external carotid artery
If a patient has a Class I incisor relationship, which guidance will they have during a protrusive excursion?
Incisor/canine guidance
If a patient has a Class II Div I incisor relationship, which guidance will they have during a protrusive excursion?
Posterior guidance
If a patient has a Class II Div II incisor relationship, which guidance will they have during a protrusive excursion?
Increased overbite - hinge open
If a patient has a Class III incisor relationship, which guidance will they have during a protrusive excursion?
Reverse overjet - posterior guidance
What is the max bite force?
40-200N
Why is it important to assess occlusion prior to providing an indirect restoration?
To minimise the risk of failure.
How many mm away is the RCP normally from the ICP?
about 1mm
If a pt demonstrates canine guidance and you are looking to provide a porcelain crown for a canine, what may you want to do to prevent it from taking a heavy load and fracturing?
You may want to change the guidance to group function by altering the shape of the crown to prevent it from taking a heavy load and fracturing.
When teeth are involved in anterior or lateral guidance, what might be useful?
Articulated models with a customised incisal guidance table.
How would your treatment plan be structured if your patient requires both removable and fixed prosthesis?
- Design the denture first - ie:
- 1st imps
- Occlusion
- Design
- Request special trays (to take 2nd imps after tooth modification if required) - Prepare the tooth for the indirect restoration PLUS additional prep for rest seats
- Prescribe for the desired polished surface morphology:
- Use words, diagrams, and verbal instruction. - 2nd imps:
- Try to do this on the day of fitting the crown
- Panavia and rely x should have set by then - Try-in, finish, ease.
If fitting a crown AFTER fitting a denture, what specialist technique should be used?
How many additional appointments will using this technique add on?
The transfer coping technique.
1 additional appointment.
What type of articulation should you aim to create in prosthetic dentition?
Balanced articulation.
What curves can be used to achieve balanced articulation?
Compensating curves.
What can be used to help transfer information from the previous fixed prosthesis to the new fixed prosthesis?
A customised incisal guidance table.
Which type of articulator is normally used for removable prosthesis?
An average value articulator.
When fixing toothwear, what are we aiming to do?
Increase the OVD
Decrease the FWS (more overopened)