Fixed and removable pros Flashcards
What fractures to a tooth would make it unrestorable with a crown?
Fractures that extend past the ACJ
What are the indications for a crown?
F - Minimise risk of tooth fracture
R - Repeated failure (of direct restoration)
A - Aesthetics
N- New crown to replace an existing crown
D - Difficulty achieving contact/occlusion w direct rest
P - For aiding removable/permanent pros (dentures/bridge abutment)
“FRANDP”
Biological width
~2-3mm
From junctional epithelium (where the gingival becomes attached) and connective tissue attachment to root surface of the tooth.
If this is encroached due to large crowns being made it can cause failure
When should you NOT use a crown?
Poor OH
Active disease (caries or periodontal disease)
Inadequate crown height
Inadequate access for tooth preparation or impression taking
When there is a more minimally invasive option
How many vital teeth prepared for crowns subsequently need root canal therapy?
20%
Cores: amalgam
Pros: easy, cheap, differentiates from natural tooth well, packable (no voids)
Cons: long setting time, weak in thin sections, mercury?, electrolytic action, not adhesive
Cores: composite
Pros: strong in thin section, tooth coloured, light curable (so immediate setting)
Cons: moisture control, hard to distinguish
Self threading pins
Not commonly used, ss pins in the dentine used to aid retention for core materials etc.
Makes the core more at risk of fracture
Panavia
RMGI adhesive luting cement (active)
NAYYAR core
3-4mm of canal filled with amalgam/composite above the RCT, makes a successful “NAYYAR” core - this avoids use of post.
Would you use a post in a posterior tooth?
No. Roots often curved. Root fracture likely as they do not reinforce the roots.
Use NAYYAR core instead.
What bur is used to prep canals for posts?
Blunt non-cutting tip burs (Gates-Gliddens)
Work up in size —> cuts laterally not vertically.
Describe the preparation for a post
Blue section = post
White section = core
Red section = GP
Light yellow = crown
Ferrule preparation
Active vs Passive posts
Active = mechanical retention
Passive = relies on frictional/cementation etc
What is the most important feature of a post?
Length
Most commonly used post system
ParaPost is parallel serrated post fibre reinforced.
What else can cuspal coverage restorations offer beneficially apart from preserving the integrity of a weakened tooth?
Correct occlusal discrepancies and aid reorganisation of the occlusal scheme
EBD: crowning RCTs?
Non-crowned after RCT were lost six times faster than crowned RCTs.
Hydrophilic impression materials
Alginate (irreversible) and agar (reversible)
Hydrophobic impression materials
Silicones
Polysulphides (smelly not used)
What impression material is commonly used for indirect restorations and why?
Silicone (addition polymerisation reaction)
in DDH use Affinis.
hydrophilic properties means this won’t recoil from the detailed areas (gingival crevicular fluid)
Why is retraction cord useful for impression taking
Absorbs moisture and displaces soft tissue
Preformed crown
Polycarbonate - pre-made sizes —> trim to fit
How many remaining occlusal units are required to allow for sufficient adaptive capacity?
four occlusal units
The Rochette bridge
A type of dental bridge that uses perforated metal wings (retainers) bonded to the adjacent teeth with composite resin. The perforations in the wings enhance the retention by allowing the resin to flow through and create a mechanical lock.
The maryland bridge
A dental prosthesis consisting of a false tooth (pontic) with metal or porcelain wings on either side that are bonded to the back of the adjacent teeth (abutments) using a strong dental resin.
Cantilever design
Replacement of one tooth, crowning the other
Fixed-fixed bridge
Replacement of multiple teeth in an arch, crowning two teeth either side
Fixed-moveable
Allows for two paths of insertion
Major retainer (is attached to the pontic rigidly), the minor retainer is the movable part.
Conventional bridges: abutment
the prepared tooth to which the bridge fits onto
Conventional bridges: retainer
The indirect restoration for the abutment
Conventional bridges: connector
Part of the bridge which connects the retiner to the pontic
Conventional bridges: pontic and the saddle
pontic - prosthetic tooth/teeth
saddle - alveolar ridge after tooth loss
What are some requirements for a cantilever bridge?
There cannot be any excursive loading onto the pontic, pontic usually sits mesial to the retainer, can only fabricate one missing tooth.
Which bridge is durable for the longest?
fixed-fixed
spring cantilever bridge
For replacement of an anterior tooth where the anterior teeth are very spaced apart
Complex bridgework
Where there is a combination of multiple designs to fit complex situations
Pier abutment
Tooth with pontics either side (generally avoided as can act as a pivot)
Pontic design
Modified ridge lap (or any variation that involves relief of the gingiva to allow cleaning underneath)
RRBs: how is the metal retainer bonded to the palatal surface of the tooth?
Sandblasted with alumina particles (50um)
Enamel etched
Panavia resin then used to bond both chemically and micromechanically
RRBs: what preparation is required of the tooth?
Ideally preparation to the tooth should not be done unless the path of insertion is a problem.
At DDH —> cingulum rest is created for location/occlusal rests if posterior tooth + removal of undercuts
Why might a ridge with teeth opposing an edentulous ridge be problematic?
Lack of stability of the opposing denture
Trauma and resorption of the ridge
Inability to achieve balanced occlusion
Flabby/fibrous ridge
Taking an impression of flabby ridge
Special tray with perforations
Mucostatic impressive (relaxed)
Two stage impression with putty and then use light bodied putty
Combination syndrome recommendations
Good in this situation to include a lower denture to address this instability
When may you consider extracting teeth?
Overerupted –> theres not space for them!
Overlay appliances/overdenture benefits
YOU’RE KEEPING THE TEETH!
alveolar bone isn’t being lost
helps balance occlusion
Natural upper teeth, no lower teeth
Implants in the lower, retaining roots and provide over denture, soft lining
Reline vs rebase
Rebase - WHOLE thing entire fit surface
Reline - chair side, partial surface
Temporary reline material uses (tissue conditioner)
Inflamed ridge, gives a soft ridge allowing tissues to heal
Useful in immediate dentures or after implant surgery
example - “COE-COMFORT”
Soft relines uses
Bruxism, atrophic ridges
Placticisers leach, candida infections
Soft lining examples
Heat cured acrylics
Self cured acrylics
Heat cured silicones - molloplast B!
Self cured silicone
Permanent reline uses
Peripheral seal issues, fit isn’t very good, post immediate dentures, prolongs life span of some older dentures
Rebase stages
- Remove undercuts from the denture
- Wash impression (closed mouth - to keep the occlusion the same)
- Cast in stone (carve post-dam)
- Plaster overcast (keeps occlusion the same)
- Cut away the palate (horse shoe)
- Wax up and replace with PMMA
Repair examples
- Two pieces fit together; no impression needed –> send to lab
- Missing pieces; insert remaining pieces into mouth and take an impression
- PMMA broken off CoCr; add retentive tags/ solder? only really temporary repairs
Additions
Only to partials
Tooth, clasps
Immediate addition
Tooth is added onto the denture
Send impression before XLA to lab
Post-immediate addition
Pt returns after XLA
Take impression with denture in mouth
Retention addition
Take impression with denture in mouth
These will be stainless steel Not CoCr
Easier to add onto a___ denture than a ____
Easier to add onto a PMMA denture than a CoCr denture.
Overdenture
Any denture over natural teeth, roots or even dental implants
Which patients can benefit particular from over dentures?
MRONJ and radiotherapy benefits
- these pts are contraindicated for XLA so useful in these situations
Precision attachments in over dentures
Metal component female, resin fibre component male. (poppy buttons vibes)
Immediate replacement dentures considerations
Denture will become loose and then need a new one (2 dentures in total! this is only temporary)
Not ideal for surgical XLA
part flange design
Open face flange design
Bulk upper anterior alveolar ridge with an undercut management
Consider an open face flange/partial design to avoid a design that acts as a food trap
Aftercare for Immediate replacements
Keep them in 24hrs, ideally overnight
Ideally review the next day (or within a few days); check for areas of healing and inflammation.
Remove dentures after meals and salty mouth wash.
Consider temporary reline 1 month?
One step immediate denture design
Modified spoon denture (temporary!!!)
Clinical stages for immediate denture design
SAME AS for normal partial dentures.
But lab will remove the stone teeth to make the full denture (lab instructions clear)
