Readings Flashcards
Who developed the first porcelain jacket crown
Charles Henry Land
Define TOC
the angle of convergence between 2 opposing prepared axial surfaces
What is the most effective means of assessing TOC
Facial/lingual clinical views because the MD surfaces are readily visible. Obtain FL views with a mirror
(Posterior/anterior) teeth are more commonly prepped with greater TOC
posterior
(Maxillary/mandibular) teeth are more commonly prepped with greater convergence
Mandibular
What teeth in the mouth are prepped with the greatest convergence
mandibular molars
(FL/MD) surfaces are prepped with greater convergence
FL
Which are prepped with greater convergence FDP abutments or individual crowns
FDP abutments
which creates greater convergence monocular vision (one eye) or binocular vision (2 eyes)
monocular
Which is more sensitive to changes in TOC (retention/resistance)
resistance
The 2001 Goodacre article suggests TOC should be between
10-22 degrees
If you have a small clinical crown your TOC needs to be (small/large)
small
3mm OC height of the crown with _ TOC should be adequate
17.4 degree TOC
What is the minimal OC for anteriors and PMs height needed for adequate retention and resistance form when prepped within the acceptable TOC range of 10-20
3 mm
What is the minimal OC for molars height needed for adequate retention and resistance form when prepped within the acceptable TOC range of 10-20
4mm (molars are prepped with greater convergence than anteriors and PMs and located where occlusal forces are greater
What should you do if your axial wall height is below the requirements
- Add grooves/boxes
- Decrease the TOC (cervically)
Horizontal forces commonly are directed in the (FL/MD) direction on teeth
FL
The greater the FL dimension the (better/worse) the resistance form
worse (hence why molars often lack adequate resistance form)
OC/FL ratio the lower this number the more (flexible/strict) the TOC guidelines
strict
Reccomended OC/FL ratio for all teeth should be
0.4 (or higher)
Teeth have geometric forms after pep what is the shape of the Pms and anteriors, maxillary molars, and mandibular molars
PMs and anteriors= over
Mandibular molars= rectangle
Maxillary molars= rhomboidal
T/F The shapes of teeth after their prep influence their retention form
t
What shapes have been retention/resistance form
teeth with corners (molars) not the conical or circular teeth the circular teeth should employ grooves and boxes (Thus it is important to preserve the natural circumference morphology of the teeth)
Grooves and boxes when prepped ususally have (greater/less) TOC than their axial walls
less- thus more resistance form
rooves and boxes are most routinely prepped for what teeth in the mouth and why
mandibular molars because they has short OC height, worst OC/FL ratio, porepped with greatest TOC (worse than maxillary moalrs) etc
To resist FL forces grooves and boxes should be placed where
MD SURFACES- plus these surfaces are commonly prepped with lower TOCs
Indications for subgingival margins
- Increase the OC height of the prep
- Extend beyond caries/restorative materials
- Esthetics
- Obtain ferrule
The dentogingival complex included what
CT attachment, epithelial attachment and sulcus depth
Why are chamfer finishlines suitable for CCC
- Provides adequate bulk for the restoration
- Distinct and visible
- Easy to form
Recomended depth of chamfer finish line is _ by depends on
0.3-0.5mm depends on the bulk of the metal **Must posses a min. depth of 0.3 mm
Depth from metal ceramic finishline is
0.8-1 mm (Shoulder finishline)
Occlusal reductions vary based on what factors
- Type of crown
- Position/alignment in arch
- Occlusal relationships
- Periodontal considerations
Malaligned teeth often require (more/less) reduction
more
Why should line angles be rounded
create stress concentration, optimizes fit and makes casting easier
Smooth preps enhances what … and decreases _
marginal fit… retention (with zinc phosphate luting agents but NOT with adhesive type cements)
Decision for what bur to use for a metal ceramic margin should be based on what
not marginal fit but on preference for esthetics, formation ease and type of metal-ceramic crown
When placing a post the minimum root wall thickness of _ should be maintained all around
1 mm
How much GP apical seal should be left
4-5 mm
Steps for parapost placement
- Determine diameter and post depth
- Remove GP (Gates, pesso reamer, hot instrument)
- Select a parapost drill that corresponds to the last gates glidden drill used (Can be used with the Universal Hand Driver or with Slow speed contraangle- drill should spin clockwise)
- Increase the size of the parapost drills until you reach the desired size
- Insert post in post space check occlusal clearance (shorten if needed)
- Clean and rinse canal and dry with paper points
- Lentulo spiral used to coat the walls of the post space with cement
- Coat the post with cement and seat
- Remove excess cement
List the steps for direction fabrication of cast post and core
- Build up with GC pattern resin
- insert the corresponding parapost temporary post in the space and make a temp (ONLY apply cement to the crown margins and not in the post space)\
- Sprue, invest, cast
- Cement (clean and dry canal, coat walls with lentulo spiral and post shaft
Describe the steps for making a cast post and core with the indirect method
- PLace the parapost into the post space and take an elastomeric impression (Make sure the anti-rotational box is filled with impression material)
- Make a provisional
- Pour the model
- Place the burnout post in the space on the model
- Core with GC pattern
- Cast alloy
Paraposts size 3 and 4 correspond to what gates
3 (0.9 and 1 mm respectively) and 3= 0.9mm
Parapost 4.5 and 5 posts correspond to what gates drills
4 (1.14 and 1.25) and gates 4= 1.10
Parapost 5.5 and 6 correspond to what gates drill(s)
5.5= gates 5 (1.40) and gates= 1.30 and 6= Gates 6 (gates 6= 1.5)
Optimal post length
- Equal the OC dimension of the crown
- Longer than the crown
- 1 and 1/3 of the crown length
- 1/2 the root length
- 2/3rd the root length
- 4/5ths the root length
- post should end halfwaybetween the crestal bone and root apex
- Post should be as long as possible without disturbing apical seal
**Most desirable is 3.4ths the root length but this is not possible in all teeth without compromising the apical seal
Post diameters shouldn’t exceed
1/3rd the root diameter at any location
Safe post diameters are between
0.6 and 1.2 mm
Posts should not extend further than _ mm apical to the canal oriface of molars because
7 because of increased risk of perforation
What gates gliddens and round burs should be avoided due to their excessive diameters
6 gates (1.4 mm) and 4 round burs (2 is good)
Adequate parapost size for maxillary centrals are
3-5
Adequate parapost size for lateral incisors are
3 and 4
Studies show that only _ mm of GP is necessary for apical seal but the recomendations are _-_mm because
4mm… 4-5mm because it is hard to stop right and 4 and distortion on X-ray. Anything less than 4mm can lead to leakage
Purposes of intrim restoration
- Maintain tissue health and contour
- Diagnostic purposes (template for tooth contours and occlusion)
- Psychological treatment for the patient (mutual understanding of treatment outcome and limitations are identified)
- Prevent tooth migration
Requirements for provisional restorations
- Good marginal adaptation
- Adequate retention/resitance
- Strong/durable
- Non-irritating to pulp and tissues (low exothermicity)
- Non-porous and dimensionally stable
- Color stable
- Physiologic embrassures and contours
- Occlusion=Physiologic
- Cleansible
- Easily removed
- Inexpensive
- No allergies
Provisionals for FDP bridges require more _ strength than single crowns
tensile (flextural strength)
Intrim restorations are generally made using what two techniques
- Custom fabrication
- Preformed materials fabrication
Provisional materials have been divided into what three different groups
- Chemically activated autopolymerizing acrylic resin
- Heat activated acrylic resin
- Light activated acrylic resin
What are the most frequently used material for intrim fabrication
methacrylate resin
Why is it perfered to make intrims from metacrylate resins indirectly
because they are exothermic
Most composite materials in intrim fabrication use _ resin
bis-acryl
What are the main advantages and disadvantages of methyl methacrylates
Advantages
- Durable
- High polish
- Inexpensive
Disadvantages
- Exothermic polymerixation
- Polymerization shrinkage
- Strong odor
Advantages and disadvantages of ethyl methacrylate
Advantages
- Lower exothermic reaction
- Lower polymerization shrinkage
Disadvantages
- Poor surface hardness
- Poorer color stability
Advantages and disadvantages of Bis-GMA composite
Advantages
- Easy to use
- Low exothermic reaction
- Low polymerization shrinkage
Disadvantages
- Brittle
- Alterations and repairs are tough
- Less polishability
Advantages and disadvantages of visible light polymerized composite
- Low temp change (contraversial)
- Controlleable working time
- Good surface hardness
- Very esthetic
Disadvantages
- Brittle
- Expensive
- Alterations and repairs= difficult
Examples of materials on the market that are methyl metharylate for making temps are
jet and duralay
Most composites are available in a _ delivery system
auto-mix (makes the easy to use and fast but expensive)
Varnish materials to make the provisional surface smoother (are/aren’t) adviable
arent
Bis-acryl is compatible with what sorts of materials
composite materials
Why are visible light polymerized resin temps less tissue toxic than methyacrylate
They don’t produce free monomers after polymerization
Preformed materials are typically made of
- Plastic
- Cellulose
- Acetate
- Metal
Preformed materials achieve a more custum fit by
Relining with acrylic resin
What are the downsides of preformed intrims
- Easy but more subject to abuse and inadequate treatment outcome
- Improper fit, contour, occlusion, etc.
Marginal adaptation for autopolymerizing acrylic resins can be improved through what technique
Relining (vent if the intrim doesn’t seat fully)
Volumetric polymerization shrinkage for PMMA is _ compared to resin materials which are _
6% … 1-2%
T/F Pigments in food can stain provisionals
t
What factors influence staining of provisional restorations
- Hygiene
- porosity
- foods (i.e curry and tumeric)
Increases in surface roughening (increase/decrease) darkened staining
increase
What materials exhibited the LEAST darkening
methyl methacrylate
What materials exhibited the best and worst color stability
Best= Methyl methacrylate Worst= Bis-acryl
Increases in the pressure applied to the provisional does what to gingival recession
increases
How can you reduce the amount of gingival recession that occurs with a provisional
Good contours and margins
Pulp injury from provisional can occur how
-Thermal or chemical irritation
What provisional material shows the lowest increase in temp
bisacryl
How can the heat given off by a temp be dissapated
- Matrix material (putty)
- Air and water coolants
Temperature rise is greatest with what material and template
PMMA and vacuum adapted templates
Why should vaseline be applied to tooth
prevent chemical injury
Should the provisional be removed from the tooth before complete setting
no
What materials have a greater potential for allergic contact stomatitis and why
autopolymerizing methacrylate because of residual monomer
Allergy signs include
- Redness, necrosis, ulceration
- Disappears when provisional is removed
- Reaction recurs when provisional is replaced
How can you reduce the amount of unpolymerized monomer to reduce allergy
relininge (indirect technique)
How can you increase the strength of a provisisonal
-Pressure and heat
Provisional luting materials should have what properites
- Low solubility
- Tooth adhesion
- Resist bacterial penetration
- *Most important function is to provide a good seal between the tooth and restoration
Most commonly used provisional cements are
- CaOH
- ZOE
- Non-eugenol materials
*These all have poor properties- don’t want to use for long term but are easily removable
What are the advantages of ZOE cements
- Antibacterial
- Decrease dentin hypersensitivity
Disadvantages of ZOE temp cements
-free radical production necessary for polymerization of methacrylate materials can by significantly hampered by presence of eugenol (interferes with acrylic acid polymerization and hardening)
