Fixed Pros Flashcards
What factors affect perception of colour
- Light source: natural light (5500K), chair light
- Object: reflects, absorption
- Observer
What are the attributes of colour
- Hue: quality by which possible to distinguish colours
- Value: achromatic measure of the lightness or darkness
- Chroma: degree of strength or saturation of colour of certain hue
What Is metamerism
- Phenomenon when two objects appear to have same colour under one lighting and different under others
What can you tell about porcelain structure
- Glass network broken up by modifiers to control properties, including solubility, viscosity, softening temperature and thermal expansion
What are the properties of dental ceramic and glasses
- Brittleness and hardness
- High modulus of elasticity
- Low thermal and electrical conductivity
- Inertness and good resistance to chemical attack
What are the methods of strengthening porcelain
- Porcelain fused to metals substructures
- Fusing to strong crystalline substructure
- Ion exchange
- Controlled crystallisation of glasses
- Resin-bonded ceramics
What are the glasses (ceramic types)
- Aluminosilicate
- Borosilicate
- Weaker veneering materials
- Tissue augmentation
What are crystalline ceramics
- Alumina and zirconia
- High strength substructures
What are glass-ceramics
- Leucite, apatite
- Lithium disilicate
- Fusing to metal or ceramic substructure
- (Cast or heat pressed)
What are the laboratory stages in making a crown
- Pour and articulate casts
- Wax pattern to full contour
- Cut back wax pattern to correct contour for substructure
- Wax sprued
- Invest the wax
- Burn out wax and cast
- Divest and sandblast
- Remove spruce and trim
- Add the porcelain
- Stains can be applied
What are the advantages of PFM
- High strength and suitable for crowns, bridges and implants
- Good aesthetics and fit
- Favourable wear properties on metal surfaces
- Rests seats, guideplanes and metal occlusal surfaces can be incorporated
What are the disadvantages of PFM
- Aesthetics and contour are poor if tooth is under prepared
- Opacity contraindicates for thin veneers
- Biocompatibility issues with some patients
What are the types of bridges
- Fixed-Fixed Conventional Design.
- Fixed Cantilever Design.
- Fixed Movable Design.
- Resin Retained Bridge
- Hybrid
What are the pontic designs
- Ovate.
- Point/Bullet.
- Modified Ridge Lap.
- Hygienic
What are indications for cores for teeth with vital pulps
- Teeth are vital but lost substantial amounts of tissues.
- Periodontal condition and hard tissue stable
- Needed for the crown
What happens to the pulp in vital tooth with core
- 17% of teeth will become non-vital (felton)
- Stressed pulp syndrome: repeated insult to the tooth leads to pulp necrosis
- 1mm from the pulp more likely to cause irreversible pulpitis (Shovelton)
Whats the problems with lining materials
- Difficult to pack filling materials on some lining materials
- Weak compressive strength
How to protect thin wall of dentine
- Setting calcium hydroxide cement: high pH, stimulates tertiary dentine, toxic to carious bacteria.
- Disadvantages: brittle so apply thinly, soluble and microleakage, doesn’t bond tooth structure
- Dentine bonding agents: seal cut dentine after removal of smear layer
- Glass Ionomer: unsuitable weak bond strength, brittle and leaches away
What are the advantages of amalgam as a core
- Strong compressive strength
- Easy to mix
- Relatively cheap
- Good Longevity
What are the disadvantages of amalgam core
- Colour
- Non – adhesive
- Environmental issues
What are the advantages of a composite core
- Good colour match
- Bonding to the tooth
- Doesn’t require mechanical retention
- Suitable compressive strength
What are the disadvantages of composite core
- Water inclusion over time
- Initial polymerisation shrinkage
- strength
How to increase retention of your core (amalgam)
- Undercuts
- Slots, grooves
- Adhesives: most are not successful long term
What are the problems with dentine pins
- They cause stress in dentine leading to micro cracks
- May be near the pulp
What are parapost characteristics and benefits of each
- Parallel sided: increased retention over tapered
- Serrated: 8x increase In retention over smooth
- Cement escape channel: allows full seating
- Rounded tip: reduces stress
What comes in parapost system
- Drill
- Plastic impression posts (smooth)
- Burnout posts (serrated)
- Wrought metal ‘cast on’ posts in stainless steal or gold
- Aluminium temporary posts
How to assess the size of post
- Use the post of Rad
- Hold measure device against
- Removes least dentine
How to prepare canal for post and how much GP to be preserved
- 4mm GP at apex
- GG bur first
- Narrow drill and build up
- Use silicone stopper
How to do the direct post technique (sending to lab)
- Serrated ‘burn out post
- Use duralay or wax to shape
- Check occlusion and send to be cast
How to do direct technique post (chairside)
- Place wrought gold in canal
- Cut so 1-2mm protruding
- Apply composite resin with etch and bond
- Contour to core shape
What is the indirect post technique (smooth post)
- Place smooth impression post
- Trim to height of neighbouring tooth
- Put groves on post that protrudes and apply adhesive
- Take impression of it (light body in area)
- Will come out with impression
Problems with indirect impression technique for posts
- Impression material doesn’t go in canal: inaccuracy or post moving if put in first
- Multiple appointments
- Costs (lab work)
How to temporise a post system
- Place aluminium temp post
- Trim
- Make temp crown
What are the two types of luting agents
- Non adhesive: reliant on retentive preps
- Adhesive: reliant on micromechanical retention/bond
What are non-adhesive luting agents
- Crowns, retentive onlays, posts
- Zinc phosphate
- Zinc polycarboxylate
- Glass ionomer
What are adhesive luting agents
- Crowns, RBB, inlay/onlay, veneers, posts
- Resin based cement: Panavia, Rely X Ultimate
- Glass ionomer compomer based (aquacem)
How to we check crown on die
- Check the fit surfaces on crown for defects: casting nodules or ‘bubbles’
- Check die for damage: margin deficiencies, proximal contacts of adjacent teeth
- Check crown on die: ledges, over/under extended margins, casting only touch margins
How do you check crown on patient
- Seat crown without forcing
- Check seated fully
- Try not to use LA to give patient proprioception
- Floss contacts
- Check margins
- Aesthetics
- Check occlusion, with and without crown, opposite side
Common errors affecting marginal fit and failing to seat crown
- Tight proximal contacts
- Casting nodule on fit surface
- Over/under extended crown margins
- No die spacer
- Impression distortion
What are the causes of over-extended margin (beyond finish line)
- Poor impression
- Surplus untrimmed ceramic or wax
- Improperly trimmed die
What are the causes of under-extended margin (ledge)
- Poor impression
- Over polished casting
- Improperly trimmed die
- Difficult to identify finish line
What are the causes of over contoured (thick) crown
- Lab over waxed
What are the causes of an open margin
- Casting not completely seated
- Poor impression
- Incomplete casting
- Improperly trimmed die
- Over polished casting
What to do if the contact is open or tight
- Too tight then adjust tight side with rubber wheel
- Open contact: modified in lab
Adjustment of marginal fit of crown
- Over-extended: adjusted with soflex disc
- Deficient need to be remade
How to assess occlusion
- Must be first and last to be checked
- Identify a pair of adjacent occluding teeth and assess resistance with shim stock (10 micro..) without the crown and with
- Mark high spots GHM in ICP use miller forceps
What are indication of zinc phosphate cement
- Single metal or metal-ceramic crowns, Lithium Disilicate, Zirconia crowns with retentive design features, posts
- Advantages: longest track record, high compressive strength, low film thickness, reasonable working time
- Disadvantages: low tensile strength, no adhesion, not resistant to acid dissolution
What are indication of polycarboxylate cement
- Indications same as zinc phosphate
- Traditionally used for vital or sensitive teeth (but no evidence to support its efficacy)
What are the indications of GIC cement
- Mentioned above
- Advantages: high compressive strength, low film thickness, fluoride release, reasonable working time, bond to tooth, resistant to water dissolution
- Disadvantages: sensitive to early moisture, low tensile strength, no molecular adhesion to the crown
What are indicationos for RMGIC cement
- Not recommended for ceramic crowns, onlay, veneers
What are resin cements adv and dis
- Advantages: high compressive strength, high tensile strength, resistant to water dissolution, resistant to acid dissolution, adhesion to the tooth and crown material
- Disadvantage: technique sensitive, variable film thickness, marginal leakage due to polymerization shrinkage
What is the problem with post in posterior teeth
- Divergent and curved roots
- Prep of canal for post will cause perforation
- Teeth are already weakened after RCT and post will weaken it further
What is nayyar core
- 4mm into each canal
- Use GG bur
- Built to full contour
What is the difference between temporary and provisional
- Temporary lasts until proper crown
- Provisional is a temporary crown to test changes in the crown shape, colour, occlusion during function. Lasts longer than a few weeks
What are the functions of temporary crown
- To protect the open tubules from micro leakage and protect root canal treated teeth from bacterial invasion
- Maintain occlusal relationship, preventing over eruption
- To maintain the interdental space and contacts. Preventing of tilting on neighbouring teeth
- To prevent gingival hyperplasia at the margins and maintain gingival health. In some cases, improve gingival health when placed over previously overhanging restorations.
- Maintain appearance
- Extra: can use gauge to measure thickness to see if prep is good
Why do we need Provisionals
- Same as temps and
- Check changes in occlusions are acceptable
- Check phonetics
- Check aesthetics
- Check mastication
What are lab made Provisionals
- Aesthetically demanding cases to visualise as closely as possible to proposed final result
- Long term temporisation where healing is required (implants)
- Creation of optimum tissue health around multiple preparations before taking definitive impression
- To create and ensure occlusal stability in full arch cases before final jaw registration
What are materials for temporary
- Acrylic resins (polymethacrylate)
- Bis acryl composite: Protemp, quicktemp
- Poly methyl methacrylate: Duralay
How can you create temporaries and provisionals
- Over impressions: using putty or alginate indices
- Vacuum formed matrix: created on cast prior to the prep
- Polycarbonate crown: only for anterior and premolar (prefab)
- Aluminium crown: for molars
- Celluloid crown formers: usually only for anterior
What instructions to the patient after temp crown
- Temp crowns are fragile
- Avoid eating until numbness wears off
- Avoid chewing on hard or crunchy foods
- Avoid extreme hot and cold foods in the first few days
- Avoid chewing gum or sticky candy
- Contact clinician it comes off
- Hot or cold sensitivity for one week
- Floss certain way, Te-pe brushes
What are the problems sub gingival preparation
- Difficult prepare, record, cement and clean
- Long term perio health can affected
- Risk of marginal leakage
- Risk of encroaching on the biological width leading to persistent gingival inflammation, bone loss and gingival recession
What is a crown
- An artificial replacement that restores missing tooth structure by surrounding part or all of the remaining structure with a material such as cast metal alloy, metal-ceramics, ceramics, resin, or a combination of materials
What are the steps before a crown
- Periapical radiograph: apical pathology, root filling
- Sensibility testing
- Periodontal tissue assessment (needs to be healthy)
- Core assessment
- Occlusal assessment (why?)
- Wax up (especially multiple teeth)
What are types of crowns
- Full gold
- Full metal
- Ceramo-metal crowns
- Composite crown
- All ceramic
What are the principles of the tooth preparation?
- Preservation of tooth structures
- Resistance and retention
- Structural durability
- Marginal integrity
- Preservation of the periodontium
What is resistance
- The ability to withstand compressive and oblique displacing forces
What is retention in terms of crowns
- The ability to withstand occlusally directed displacing forces.
- Theoretically maximum retention is obtained from parallel walls
What is the taper angle
- 2-3 degree from each side
- Convergence angle is 6 degree
What are the types of finishing lines/ margins
- Feather – edge and chisel finishing lines (difficult to locate, not sufficient bulk)
- Chamfer
- Shoulder finishing
When erosion is suspected what should be asked
- Diet
- Gastric cause (acid reflux)
- Underlying GI disease
- Bulimia
What are the adv/dis of full metal crown
- Advantages: best resistance and retention, less tissue removed, kindest to opposing tooth
- Disadvantages: aesthetics, allergy issues
What are the adv/dis of all ceramic
- Advantages: aesthetics, less tooth in some areas
- Disadvantages: increased destruction in some areas, longevity, moderate strength
What are the adv/dis of ceramo metal crowns
- Advantages: aesthetics, longevity
- Disadvantages: increased tooth structure in some areas
What do you do with undercuts and why when doing impressions
- Addition cured silicones and polyether’s are rigid once set
- Check undercuts: buccal sulcus, periodontal bone loss, large interdental spaces, beneath bridge pontics
- Block out these using soft wax (ribbon wax)
What should we not use special trays with
- Heavy body for crowns as it will get stick
What can you tell me about addition cured silicones
- No by products
- Hydrophobic
- Low viscosity: great surface detail
- Provides accurate fine detail of tooth prep, dimensional stable
What can you tell about polyethers
- No by products and dimensionally stable
- Takes up water so needs to be stored dry
- One viscosity
- Good elastic properties
- Suited for implant prosthodontics
What can you tell me about hydrocolloids
- Poor tear resistance
- Dimensionally unstable: if stored dry they shrink, stored in water they swell
- Inferior impression detail to addition silicones
- Uses: opposing model and study casts
What happens if restoration is placed and changes occlusion
- Fractured cusps or restorations
- Increased tooth mobility
- Muscle fatigue
- Tooth wear
When do you do a jaw reg
- Last tooth in the arch
- Multiple preps
- Multiple anterior prep
- Not need in bounded preparation
futarD
Materials for jaw registration
- Beauty wax and temp bond
- Polyvinylsiloxane bite reg past (normal one>)
What are the favourable characteristics of an impression material?
- Accurate
- Good dimensional stability
- High tear resistance
- Good working time
- Easy to handle
- Low cost
- Pleasant taste and smell
What is the definition of a veneer
- Layer of tooth coloured material attached to the surface of a tooth to re-establish the morphology and function of teeth
- Porcelain laminate veneer: a thin bonded ceramic restoration that restores the facial surface and part of the proximal surfaces of teeth requiring aesthetic restoration
What are the clinical indications of veneers
- Restoring tooth morphology
- Altering tooth morphology: shape, size, diastemas
- Improving aesthetics: discolouration
- Fractured anterior teeth
- Malpositioned teeth
What are the clinical contraindication of veneers
- Lack of sound enamel for adhesion
- Parafunctional habits
- Lack of tooth tissue
- Unstable tooth surface loss: bruxism, erosion
- Unsuitable occlusal schemes
- Poor prognosis of tooth/teeth: mobility
- Bonding to large or extensive pre-existing composite
What are the types of veneers and preparations
- Direct and indirect
- Window: most of the front
- Feather: all the way to incisal edge
- Bevel: incisal edge height reduced
- Incisal overlap: some on the palatal
What improves outcome of resin retained bridges
- Distal cantilever bridge design
- Maximise tooth tissue surface area covered
- Modify teeth to maximise connector height
- Fixed fixed design only across the midline
- Occlusal coverage improves outcome
- Sandblasting before cementation
What is the aetiology of extrinsic discolouration
- Stains that lies on/attach to the tooth surface or in the acquired pellicle
- Incorporation of extrinsic stain within the tooth substance following dental development. It occurs in enamel defect and in the porous surface of exposed dentine
- Plaque, chlorhexidine mouthwash, smoking, tea/coffee, antibiotics
What is aetiology of intrinsic discolouration
- Discolouration following a change to the structural composition or thickness of the dental hard tissues
- Pre-eruptive disease: enamel hypoplasia, medication, disease
- Post-eruptive: trauma, caries, tooth wear, dental restorative material
What are the treatment options for staining
- No treatment
- Removal of surface stain: scale and polish, micro abrasion
- Bleaching
- Restorative treatment: veneers, crowns
What are the bleaching techniques
- Vital: home 10% carbamide peroxide, clinic: 30% photoinitiated
- Non-vital bleaching: inside/outside method using 10% carbamide peroxide
- Materials: hydrogen peroxide, carbamide peroxide (more stable)
Mode of action of bleaching
- Thought to be ingress of oxidisers and oxygenating molecules through enamel micropores.
- Break/ cleave pigment bonds and allow molecules to diffuse through the tooth
- Or become smaller and absorb less light
What are some fixed options for replacing missing teeth
- None
- RBB
- Implant
- Conventional bridge
What is an RBB
- Minimally invasive fixed prostheses which rely on composite resin cements for retention
- Made possible after development of resin cements which bond to tooth and metal
- Non invasive and good longevity
What are the components of an RBB
- Connector: metal element joins wing and pontic
- Wing: non precious metal, nickel-chromium or cobalt chromium
- Pontic: porcelain fused to metal sub structure
What are the advantages of RBB
- Minimally invasive
- Less clinical time compared to implants
- Less expensive
- Failure less catastrophic
- Aesthetic
- Predictable
- No LA
Disadvantages of RBB
- Aesthetics (abutment tooth appear grey, metal can be seen)
- Debonding
- Longevity
What are the types of designs of RBB connectors
- Cantilever: simple, load transmitted on one tooth
- Fixed-fixed: rigid and load more equally distributed
- Fixed-movable: one movable connector, differential movement
- Hybrid: complex bridge, e.g conventional and rbb
When is a fixed fixed design indicated
- Differential movement can cause it to fail
- Indicated where excursive movements on pontics cannot be avoided
- Crossing the midline
When is a hybrid design indicated
- One tooth is prepared conventional
- Other tooth is sound and rbb wing used to conserve structure
- Not much in long term data
Tell me about fibre reinforced composite rbb
- Better aesthetics and adhesion
- Usually fibre reinforced with glass, ultra-high molecular polyethylene or Kevlar fibres
What to do before doing RBB
- Contemporary PA
- Gingival health good
- Informed consent
- Study casts and checked occlusion (lateral excursion)
- Diagnostic wax up maybe
- Shade matching
- No prep required
- Pontic shape
What are the pontic shapes
- Ovate is ideal
- Modified ridge lap is also useful
What factors affect the longevity of RBB
- Design (cantilever, fixed fixed)
- Surface coverage
- Connector height
- Preparation of abutment tooth
- Metal surface treatment (sandblasting)
- Occlusal considerations
- Operator experience/ technique
What is the longevity of RBB
- 80.4% after 10 years
- King et al (2015)
What is the dahl concept
- Relative axial tooth movement
- Observed when local appliance/ restoration placed high
- Occlusion re-establishes full arch contacts over period of time
- Intrusion (40%) and extrusion (60%)
When can you use the dahl concept
- Increase interocclusal space
- Increase OVD
- Sever anterior tooth surface loss
- 6-24months to take full effect difficult to predict (feel acceptable in 1-2 weeks)
Why would you choose direct build up over indirect
- Minimally invasive in wear case
- Afford the clinician control over final aesthetic
- Reduce cost and time (no lab)
- Problems: staining, not as strong,
What is the advantages of a conventional fixed bridge
- 15-20 year life span
- Predictable and aesthetic result
What are the disadvantages of conventional fixed bridge
- Can be very destructive
- Failure can lead to fracture of abutment tooth
- Need for rct in failure
What are the pontic design
- Ideal: passive, smooth fit, adequate embrasure space to allow clean
- Wash through
- Modified ridge lap
- Ovate pontic
- Rindge lap pontic
- Dome pontic
What are some factors of the pontic in cantilever bridge
- Same size or smaller than abutment
- Avoid heavy contact, should only exhibit intercuspal contact
- Posterior where occlusal load is high two abutments may be indicated
What is fixed movable conventional bridge
- Replacement of one or two teeth in the posterior region
- Design utilises a ‘stress-breaking’ effect
- Reducing demands on the minor retainer
Describe some planning factors of crowns for RPD
- Rests
- Guide planes
- Undercuts
- Milled ledge
- Metal where these are is more favourable
What is bruxism
- The parafunctional grinding of teeth.
- Oral habit consisting of involuntary rhythmic or spasmodic non functional grinding or clenching of teeth
What is TMJD
- A collective term for muscle disorders of the masticatory system with two observable major symptoms
- Pain and dysfunction
- Common observations: muscle fatigue, muscle tightness, myalgia, spasm, headaches, decreased range of motion
What is an occlusal splint
- Rigid or flexible device that maintains in position a displaced or movable part
- Also used to keep in place and protect an injured part
- Also used to protect , immobilize or restrict motion in a part
What are the types of splints
- Soft splint
- Hard splint
- Full coverage
- Michigan: cover the teeth
- Anterior repositioning splint
- Partial coverage
What are advantages and disadvantages of soft splints
- Advantages: good for emergency where opening is restricted so accuracy is compromised, cheap to make
- Disadvantages: spongy feel so bruxism chew more and increase pain, short term use, wear down soon
What is NTI-TSS splint
- Nociceptive trigeminal inhibition tension suppression system
- Anterior bite stop
- Helps bruxism, TMD, tension type headaches, migraines
What are hard acrylic splints
- Full or partial coverage
- Partial coverage allows over eruption so may be avoided
What are the role of splints
- Treat TMJD
- Prevent tooth wear
- Check patient can wear RPD, overdentures
- Test increase in OVD: less worried in dentate patient as they can tolerate 5mm, tries to make RCP=ICP
- To check patient in RCP: increases OVD and makes it difficult for muscles to tense and RCP can be done
What are some of the effects of tooth wear
- Loss of coronal tooth structure
- Aesthetics
- Altered horizontal jaw relationship
- Reduced masticatory efficiency
- Hypersensitivity
- Pulpal necrosis
- Soft tissue trauma
- Reduced OVD
For TMD what are the 3 main signs
- Pain in joint or muscle
- Joint sounds
- Limitation of movement
What is the definition of TMD
- Is a set of diseases and disorders that are related to alterations in the structure, function or physiology of the masticatory system
- May be associated with other systemic and comorbid medical conditions
- 33% with one sign of TMD
What is the management of patients with myogenous TMD
- Reassurance
- Splints
- Electronic devices
- Physiotherapy
- Medication
What to consider in restoring a RCT tooth
- Ferrule or not
- Level of fracture
- Length of root and periodontal support
- Quality of RCT
- Crown to root ratio
Molars requiring RCT but display furcation involvement
- Double the risk of molar loss after 10-15years
- Still respond well to periodontal treatment
