Fixed Prosthodontics BDS4 Flashcards
Why do we replace teeth?
Improve aesthetics
Improve occlusal stability e.g. prevent eruption of opposing teeth
Improve function e.g. mastication, speech.
For periodontal splinting
Restoring OVD
Patient preference
What is a diagnostic wax up?
What are the advantages of a diagnostic wax up?
Wax is added to study casts in order to mock up the appearance of a fine restoration
Usually used for bridges, veneers, build-ups etc.
Facilitates communication as it gives a visual aid to show patient
Allows for greater accuracy and consistency
3D visualisation by patient and dentist
Allows for provisional trial
Incurs extra cost and time but can equally save costs and time in the long term
What are the various types of wax ups that can be sued in fixed pros?
Wax up is done on a study cast of patient Composite mock up done directly on teeth then impression sent to lab Wax up, then clear vacuum formed stent or putty matrix made to allow changes to be duplicated in the mouth Composite shell (lab constructed) to be temporarily placed in the mouth Computer imaging - may be idealistic but not achievable and very expensive
What is the diagnostic wax up technique?
Alginate impression for study casts
Good communication with lab asking them to construct study casts and add wax as prescribed
Explanation to patient, they can take wax up away with them to consider
Possible putty matrix construction or VFS may be carried out
What are extra-coronal preparations?
Give examples
It is when restorative material on a base or core is placed over the tooth to bring the tooth back into its functional or aesthetic normal structure
Crowns
On-lays
Veneers
What are the reasons for placing veneers?
Improve aesthetics
Change teeth shape/contour
Correct peg shaped laterals
Reduce/close proximal spaces and diastema’s
Align labial surfaces of in-standing teeth
When should you not use veneers?
Poor OH High caries rate Gingival recession Root exposure High lip lines Severely rotated/overlapping teeth Extensive tooth surface loss/Insufficient bonding area Heavy occlusal contacts Severe discolouration
What are the reasons for restoring teeth with inlays/onlays?
In tooth wear cases (increase OVD)
When there is fractured cusps
Restoration of root treated teeth
Replace failed direct restorations
Why do we treat tooth wear?
Aesthetic concerns from patient Symptoms of pain and discomfort Unstable occlusion Functional difficulties Excessively fast rate of tooth loss so prevention is key
What are the 5 factors that need to be taken into consideration when treating localised anterior maxillary tooth wear?
The pattern of tooth loss
Inter-occlusal space
Space requirements for restoration to be used
Quality and quantity of remaining hard tissue, especially the remaining enamel as this greatly affects success rate
Aesthetic demands of patient.
What are the 3 types of patterns observed in maxillary tooth wear?
Tooth wear limited to palal surfaces
Tooth wear involving palatal and incisor edges resulting in reduction of crown height
Tooth wear limited to labial surface
Why is there a lack of inter-occlusal space associated with tooth wear?
When teeth wear, there is no increase in freeway space but there is compensation for loss of tooth substance by dental-alveolar bone growth
This growth maintains masticatory efficiency but leaves no space for restorations to be placed
What is the Dahl technique?
It is a technique used to gain inter-occlusal space in cases of localised tooth wear without tooth reduction
Initially, an appliance is placed anteriorly increasing the OVD by 2-3mm
Over time, the posterior teeth erupt into occlusion
This creates space to allow for restorations of the anterior teeth
What is the technique used for treating localised anterior maxillary tooth wear?
Modification of Dahl Technique;
Mount study models with face bow registration
Open articulation by 1-2mm to create space to allow for incisor build-ups
Diagnostic wax up, starting with the canines and then continuing waxing up the rest of the teeth when the articulator is closed
What is the procedure for using a vacuum formed matrix in tooth wear cases?
Use PTFE tape to cover teeth adjacent to tooth being built up to prevent teeth sticking together
Try the matrix in place then remove
Cut a vent hole on incisor edge to allow extra composite to vent out of the matrix
Etch and bond tooth in question for build-up
Load matrix tray with composite and seat firmly, remove excess composite that comes out of the vent
Light cure composite
Remove matrix and trim
Remove dental dam
What special investigations do you carry out prior to placing extra-coronal restorations?
Sensitivity testing - thermal and EPT
Percussion and mobility testing
Radiographs (peri-apical)
Why do we require study casts for planning crowns?
To create a diagnostic wax up of patients teeth
For articulation, surveying and designing the crowns
To allow for facebow to be mounted - particularly if OVD is being changed
Occlusal registration and analysis
What are the different types of crowns that are available?
All metal restorations;
Precious gold or platinum
Non precious nickel, titanium and chromium
Metal-ceramic restorations;
Porcelain fused to metal
What are the advantages and disadvantages of metal-ceramic restorations?
Advantages;
Good aesthetics
Good strength
Minimum palatal reduction
Disadvantages;
Appearance at cervical margin may be poor
Destruction of tooth tissue and risk of pulpal damage
Allergies to components used
Could be abrasive to opposing teeth.
Root fracture may occur
What types of full gold crowns are available?
Type I and II = better for onlays and inlays
Type III and IV = better for crowns, bridges and RPDs
