Bridegwork Flashcards
What are the treatment options for missing teeth?
No treatment
Replace tooth
Close space (ortho)
What are the 2 types of bridges and 2 types of bridge designs.
Adhesive v conventional
Fixed-fixed v cantilever
What are some local indications for bridgework?
Big teeth
Heavily restored teeth (abutments for conventional)
Favourable abutment angulations
Favourable occlusion (no heavy contacts)
What are some general contraindications for bridge work?
Uncooperative pt
MH- allergy to metal
Poor OH, high caries rate, perio disease
Large pulp (for conventional)
What are some local contraindications for bridgework?
High possibility of further tooth loss within arch
Poor prognosis of abutments
Large length of span
Ridge form and tissue loss
Tilting/ rotated teeth
Degree of restoration (how much tooth is left after prep)
PA and perio status poor
What is a pier?
An abutment tooth which stands between and is supporting 2 pontics, each Pontic being attached to a further abutment tooth
What are some advantages of adhesive cantilevers?
Minimal/ no prep
No LA
Less costly, less surgery time
Can be used as provisional
In which case would an adhesive cantilever be used as a provisional restoration?
In hypodontia pts - used as a provisional before considering implants
What are some disadvantages of adhesive cantilevers?
Moisture control required
Metal shine through
Chipping porcelain
Can debond
Occlusal interferences (may fracture in lateral excursions)
No trial possible
When would an adhesive cantilever be contraindicated?
Insufficient/ poor enamel quality
Long spans
Excess soft or hard tissue loss
Heavy occlusal force (bruxist)
Poorly aligned/ tilt led/ spaced teeth
Contact sports - encourage use of mouth guard
What is a direct resin retained bridge?
Using the patients own tooth (or acrylic denture, polycarbonate crown or cellulose matrix filled w composite).
Used in emergency, trauma or if tooth needs to be extracted immediately.
Extract tooth, cut off root and remove coronal pulp, place composite over pulp and etch and bond tooth and contacts. Place composite inter proximally and cure.
Where should the margin of the indirect RBB be in relation to the gingiva?
0.5mm supra gingival
Why are cantilever bridges more successful than fixed fixed bridges anteriorly ?
There are divergent guidance paths anteriorly (due to arch form) therefore, fixed- fixed are more likely to debond as the forces are going in multiple directions
If preparation is required for RBB, what principles should it follow?
180 degree wrap around with supra gingival chamfer line around 0.5mm.
Anterior- occlusal reduction if heavy contacts, cingulum undercut removal, metal retainer wing should be 0.7mm thickness (will settle in 2 weeks).
Posterior- occlusal rests 2mm deep.
Consider:
Rests- provide mechanical retention, helps to locate when seating
Proximal grooves- mechanical retention, vertical cuts towards interproximal areas
Keep within enamel
How do you temporise bridge prep?
RPD- Essix retainer
If prep remains in enamel- no need to temporise (uses sensitive toothpaste)
If into dentine- cover with layer of dentine bonding agent
When should bridge be fit after prep appt?
Within 2 weeks to minimise over eruption and tooth movement
What is the retainer wing made of and how is the fitting surface prepared?
CoCr or nickel chromium alloy
Sandblasted surface to increase micro mechanical retention (aluminium oxide 50 um creates small indentations on surface)
Describe the process of fitting the RBB
Try in - occlusion, fit and aesthetics
Micro etch with AlO (sandblast) - should have been done in lab
Clean retainer
Apply chemically or dual cure composite luting cement (panavia 21) to fitting surface
Isolate with dam
Etch tooth, wash and dry
Apply primer for 30 secs
Air dry
Fit retainer
Remove excess cement
Oxygen inhibitor (oxyguard) placed around cement margins for 3 mins, then washed off
Check occlusion
Demonstrate cleaning around and underneath bridge (super floss/ interdental brushes)
What are some advantages of conventional fixed fixed bridges?
Robust design
Max retention and strength (+bonding)
Can be used in longer spans
Disadvantages of conventional fixed fixed bridge?
Prep can be difficult - need parallel tooth preps for common POI (danger of over taper - ideally 5-7 degrees)
Removal of tooth tissue can danger the pulp
Advantages for conventional cantilever bridges
Conservative design, no need to ensure multiple tooth preps are parallel
Disadvantages of conventional cantilever?
Short span only
Mesial cantilever is preferred (if abutment is more posterior, more likely to occlude on abutment - see saw effect)
Treatment option for bridge prep with 2 different POI
Fixed moveable bridge with dovetail
What are some disadvantages to a fixed moveable bridge?
Limited length of span (one tooth)
Hard to clean beneath moveable joint
Can’t construct provisional bridge
What is a hybrid bridge?
One retainer conventional and one adhesive.
What is a spring cantilever bridge?
One Pontic attached to end of a metal arm which runs across the palate to a rigid connector on the palatal side of retainer.
- useful if spacing between upper incisors, when adjacent teeth are unrestored and where a posterior tooth will provide suitable abutment
However- can only replace upper incisor, difficult to control movement of the Pontic and can be difficult to clean under palatal connector
What must be evaluated when assessing an abutment for spring cantilever bridge?
Supporting tissues should be healthy and free of inflammation
Crown to root ratio should be minimum 1:1 (optimum 2:3)
3 functions of a pontic
Restore appearance of missing tooth
Stabilise occlusion
Improve masticatory function
What should be considered with regards to Pontic design (3)
Cleansability (smooth surface, should not harbour join of metal and porcelain)
Appearance (anterior- tooth like, posterior- function more important)
Strength (longer span- greater thickness to withstand more occlusal force)
What is a wash through Pontic design?
No contacts with soft tissue - functional rather than aesthetic
Lower molars
Space between Pontic and ridge makes easy to clean
What is a dome shaped pontic?
Used in lower incisor/ premolar/ upper molars
Occlusal 2/3 of bucal surface visible (tooth like), lower 1/3 is narrow (cleansability)
What is a modified ridge lap Pontic design?
Bucal surface looks like tooth but lingual surface cut away - space to clean here (although can cause food packing lingually)
What is a ridge lap Pontic design?
Greatest contact with soft tissue
Need good OH to avoid food packing/ plaque trap under fitting surface
What is o ate Pontic design?
Best aesthetic result, presses down on gingiva causing it to mould into divet
Need very good OH
What are the 5 Pontic design options
Wash through
Dome Pontic
Modified ridge lap
Ridge lap
Ovate
Material options for conventional bridges?
All metal (gold/ nickel/ CoCr/ SS)
Metal ceramic
All ceramic (zirconia, lithium disilicate)
What is the max span for a zirconia bridge?
3-4 units
What are the principles of parallelism for bridge prep? Eg of bridge spanning 11 to 13
Prep mesial of 11, then mesial of 13
Then prep distal 11, then distal of 13 etc…
Then prep labial (2 planes) of 11, then labial 13
How are each type of bridges cemented in?
All metal and metal ceramic - GI luting cement (aquacem) or RMGI luting cement
Adhesive resin bridge - Panavia (dual cure resin cement)
All ceramic - NEXUS (dual cure resin)
Why should distal cantilevers be avoided?
Initial contact on bridge will be distally, causing bridge to lift up - leverage forces on abutment may cause its to tilt.
In which circumstance can a distal cantilever be considered?
From premolar abutment if unopposed/ opposed by a denture (SDA)
What are 4 reasons for adhesive bridgework to debond?
Unfavourable occlusion
Insufficient coverage with adhesive wing for bonding
Poor enamel quality of abutments
Inadequate moisture control during cementation
Caries
What are the clinical methods for checking adhesive bridge deboning?
Press on Pontic, look for movement of adhesive wing
Press adhesive wing and look for bubbles of saliva at the wing/ tooth interface
Explore margins with a probe, looking for defects/movement of wing
Pass floss underneath wing
Radiographic evidence
how can the gingiva be manipulated to create the best impression?
use of retraction cord (bathed in astringent eg ferric sulphate)
what materials are used to take the bridge impression?
polyvinyl siloxane materials (eg extrude)
polyether materials (eg impregum)
what are the advantages of impression material in a gun dispenser?
prevents air bubbles in material
ease of mixing
regular consistency
predictable setting characteristics
what is the purpose of the heavy bodied putty material in a putty wash technique?
supports the light bodied material
why is a fixed fixed adhesive bridge not usually recommended?
can debond on one side and pt may not notice - secondary caries
what is Antes law?
PDL of the pontic should be equal to or less than the PDL of the abutment
why should canines not be used as an abutment for RBB?
Wing may be sheared off during canine guidance
