BDS4 dickie bridges Flashcards
indications bridges?
- Function and stability
- Appearance
- Speech
- Psychological reasons
- favourable abutment angulation
- favourable occlusion
contra-indications bridges?
- Poor oral hygiene
- High caries rate
- Periodontal disease
- Large pulps (conventional bridge)
- uncooperative pt
- Prognosis of abutment poor
- Length of span too great
- Degree of restoration (how much of tooth is left after preparation)
what is retainers?
The extracoronal or intracoronal restorations that are connected to the pontic and cemented to the prepared abutment teeth
what is a pier?
An abutment tooth which stands between and is supporting two pontics, each pontic being attached to a further abutment tooth
what is a unit? and for example what would a bridge with 2 retainers and one pontic be?
Either a retainer or a pontic
- e.g. A bridge with two retainers and one pontic = 3 unit bridge
what are types of bridge designs?
conventional or adhesive/resin retained
- fixed-fixed
- cantilever
fixed moveable bridge
hybrid bridge
spring cantilever bridge
what is a cantilever bridge?
This type of bridge has a retainer (or retainers) at one side of the pontic only
- can be either conventional or adhesive/resin retained
what is a fixed-fixed bridge?
This type of bridge has a retainer at each end with a pontic in the middle joined by rigid connectors.
- can be either conventional or adhesive/resin retained
what are advantages of resin bonded bridgework?
- Minimal or no preparation
- Less costly
- Less surgery time
- Can be used as a provisional restoration
what are disadvantages of resin bonded bridgework?
- Metal shine-through
- Chipping pocelain
- Can debond (High chance of it debonding again)
- Occlusal interferences
- No trial period possible
what are indications for resin bonded bridgework?
- Young teeth (Less destructive)
- Good enamel quality
- Minimal occlusal load
- Good for single tooth replacement
what are contraindications for for resin bonded bridgework?
- Insufficient or poor quality enamel
- Long spans
- Heavy occlusal force e.g. Bruxist
- Poorly aligned, tilted or spaced teeth
what must you do with study models for resin bonded bridgework and what may you consider
- mounted on semi-adjustable articulator with facebow registration
- may consider diagnostic wax-ups
when to use a direct resin bonded bridge?
- Very useful in emergency situation
- If tooth needs to be extracted immediately
- If tooth has been lost traumatically
what are considerations in regards to existing restorations in abutment teeth?
- firstly need sound enamel
composite - ok but might need to consider replacing prior to prep
amalgam - compromised bond to chemically cured composite cement so consider replacing
what is supra gignival chamfer finish line for bridge?
0.5mm
how do you do a minimal prep anterior preparation?
- Occlusal contact reduction,
- Cingulum undercut removal only
- Chamfer margin (0.5mm supra-gingival)
how do you do a heavier preparation anterior prep?
0.5mm palatal reduction(NOTE – metal retainer wing should be 0.7mm thick)
Cingulum rest
+/- Proximal grooves
Chamfer margin (0.5mm supra-gingival)
how do you do posterior preparation?
- Occlusal rests
- 180º wrap-around with chamfer finish line (0.5mm supra-gingival)
- +/- Proximal grooves
why must you fit bridge as quickly as possible?
Minimise over-eruption and tooth movement
what is treatment of retainer?
try in
- fit and aesthetics
chairside micro-etching with 50 micron aluminium oxide particles (sandblast)
- should have been done by technician
clean retainer
- ultrasonic bath if required
- use ethanol to ‘degrasse’ if required (reduced surface tension)
apply chemically (or dual cure) cure composite luting cement just prior to placement of restoration after tooth treatment
how would you go about the treatment on the tooth prior to placing retainer?
- Prophylaxis
- Isolate with dental dam
- Etch tooth: 37% ortho-phosphoric acid (some preparations are 40%)
- Wash & dry
- Apply primer (A and B mixed together) for 30 seconds
- Air dry for 2 seconds
- No need to cure (unlike for direct composite restorations)
after treatment of tooth what do you do?
Fit retainer (coated with luting cement) to abutment tooth/teeth
Remove excess cement
Oxygen inhibitor (Oxyguard II) placed around cement margins for 3 minutes
- Wash off
what do you do post-cementation?
check occlusion
- confirm pontic does not have excessive occlusal forces applied
demonstrate to patient how to clean around and underneath the bridge
- superfloss
- interdental brushes
what are advantages of a conventional fixed-fixed bridge?
- Robust design
- Maximum retention and strength
- Can be used in longer spans
- Laboratory construction straightforward
what are disadvantages of a conventional fixed-fixed bridge?
- Preparation difficult (parallel tooth preparations needed)
- Preparation must be minimally tapered
- Common path of insertion for abutments
- Removal of tooth tissue (danger to pulp)
what are advantages of a cantilever bridge?
Conservative design
- Compared to fixed-fixed conventional design
Laboratory construction straightforward
No need to ensure multiple tooth preparations are parallel
what are disadvantages of a conventional cantilever bridge?
- Short span only
- Rigid to avoid distortion
- Mesial cantilever preferred
what is a solution to fixed-fixed designs when abutment teeth are not parallel?
fixed moveable bridge
- retainers with separate paths of insertion the bridge is united by a moveable connector
what is a fixed-moveble bridge?
This type of bridge has a rigid connector usually at the distal end of the pontic and a moveable connector mesially
- Allows some vertical movement at the mesial abutment tooth
what are advantages of conventional fixed-moveable bridge?
- Preparations don’t require a common path of insertion
- Each preparation designed to be retentive independent of others
- More conservative of tooth tissue
- Allows minor tooth movement
what are disadvantages of conventional fixed-moveable?
- Length of span limited
- Laboratory construction more complicated
- Possible difficulty in cleaning beneath moveable joint
- Can’t construct provisional bridge
what is a hybrid bridge?
one retainer is conventional preparation the other retainer is minimal preparation (adhesive/ resin retained/ resin bonded)
what is spring cantilever bridge?
One pontic attached to the end of a metal arm that runs across the palate to a rigid connector on the palatal side of a retainer
what are advantages of conventional spring cantilever bridge?
- Useful if spacing present between upper incisors
- Where adjacent teeth are unrestored
- Where a posterior tooth would provide a suitable abutment (i.e. already has a crown/large direct restoration)
what are disadvantages of conventional spring cantilever bridge?
- Can only be used to replace upper incisor teeth
- Difficult to clean beneath palatal connector
- May irritate the palatal mucosa
- Difficult to control movement of pontic, due to springiness of metal arm and displacement of palatal soft tissues
how do you evaluate abutment?
Must be able to withstand the forces previously directed to the missing teeth
Supporting tissues should be healthy and free of inflammation
Crown to root ratio
- length of tooth coronal to alveolar crest compared to length of root embedded in bone. Optimum ratio 2:3. (Minimum ratio 1:1)
what are types of pontic designs?
- wash through
- dome shaped
- modified ridge lap
- ridge lap pontic (full saddle pontic)
what are types of materials for conventional bridges?
- All metal
Gold
Nickel/Cobalt chromium?
Stainless steal - Metal ceramic
- All ceramic
Zirconia
E.g. LAVA and Procera®
Lithium disilicate
E.g. - E.max - Ceromeric
BelleGlass™
Vectris®
Targis® Vectris®
when would you especially use gold material for conventional bridges?
lower posterior area
what is most common material for conventional bridges?
metal ceramic
what is properties of LAVA?
- 3-4 unit fixed bridge (max span)
- withstand occlusal forces
- good aesthetics
- similar reduction to MCC
what are properties of zirconia?
- preps on casts scanned (straumann)
- milled
- +/- feldspathic (layer) porcelain on top
what does a vaccum formed stent allow during construction of a bridge?
- checking of reduction during tooth prep
- construction of provisional bridge
what must you aim for when doing a conventional bridgework prep?
parallelism of tapered surface of each prep
- it is doing same side of both abutments one after other instead of whole abutment then other abutment
what do you use for definitive cementation for all metal conventional bridge work and metal ceramic bridgework?
- aquacem (GI luting agent)
- RelyX luting (RMGI luting agent)
what do you use for a definitive cementation for an adhesive/resin bonded/resin retained bridgwork?
- panavia 21 (anaerobic duel cure resin cement with 10-MDP)
when should you use distal cantilevers and why?
avoid if possible
concern that occlusal forces on pontic will produce leverage forces on abutment tooth causing it to tilt
when may you consider a distal cantilever?
- may consider distal cantilever from premolar abutment if unopposed or opposed by a denture
why do you use cantilevers more anteriorly?
arch of dentition makes it so that occlusal forces on a fixed-fixed will lead to abutment pulling pontics in diff directions leading to debonding of 1 surface and then plaque gets trapped underneath a wing causing caries
why do you want a fixed-fixed on posterior teeth
- more likely as you want to spread occlusal load over several teeth
what does sandblasted do?
creates small indentations on fitting surface
when is there a higher risk of failure for bridges?
- when abutment tooth is smaller than pontic
what does overtaper result in?
reduced retention
what is degree of taper for fixed-fixed?
5-7 degrees
why is mesial cantilever preferred?
- reason is when patients occlude they are more likely to bite onto posterior teeth before anterior ones
what is properties of zirconia and lithium disilicate?
ceramic is more likey to fracture than metal
- zirconia - stronger but poorer aesthetic
- lithium disilicate - weaker but better aesthetic
what does a wash through pontic do?
give patient extra occlusal contact to bite on
more for a lower molar and is for function not appearance
when is ovate pontic used?
- for pts with good OH but want best aesthetic result.
- pushes down onto gingiva and gives look of pontic piercing out of gum
what is difference between adhesive and conventional by how they look?
adhesive has a metal wing because of minimal prep
conventional has another crown on top of abutments as it requires significant prep
