Restoration of Extensively Damaged Vital Teeth Flashcards
what are the central core guidelines
- pulp and 1 mm thick surrounding layer of dentin should be preserved if possible
- retentive features should not be cut deeper than 1.5mm at cervical line or central fossa -2mm
- auxillary retentive features ideally kept in “safe zone”
- caries removal: deeper areas filled with base
what happens to the central core as we age
it shrinks and receds
what 5 categories are involved in decision making
- deciding on the type of restoration to use
- using defects as retentive features
- pin placement and retention
- bases and cores
- tooth preparation procedures
what restoration do you use with extensive peripheral destruction
full crown
what do you do with an isthmus destruction greater than 1/2 intercuspal width
inlay or onlay
what do you do when more than 50% of tooth structure is gone and loss of cuspal support
crown and likely a core build up too
what do you do with a less destructive central lesion
inlay or onlay
what do you do with a large central lesion
build up and crown
when would you decide you need RCT
- if pulp is exposed
- if post is needed for retention of build up
what would qualify as combined extesnive periperal and central destruction
- deep proximal lesions impinging on vital core
- more than 50% of vital core destroyed
what can you do to increase retention and resistance
- re orientation of sloping surfaces
- adding grooves
- adding box forms
- adding pins with a build up
what can we do to increase resistance form with less than ideal tooth structure remaining
- reduce the total occlusal convergence of the axial walls
- add grooves
- add box forms
- increase wall height
how can you increase wall height
- place finish line more apical
- pin retained core
- crown lengthening
- orthodontic extrusion
how should you reshape axial walls to reduce TOC
increased axial reduction in the cervical 1/2 of the preparaion wall
what do you do with sloping surfaces left after cusp fracture or caries removal
- break slope into vertical and horizontal components
what does conversion of a sloping surface into one large vertical wall do
weakens the tooth with too much removal and endangers the vital core of the tooth
what should you do in a sloped wall if greater than 3mm vertical wall length apical to the fracture cusp
a facial shoulder with axial wall reduction leaves adequate wall legnth for resistance form
describe the grooves that are placed parallel to the long axis of the tooth for resistnace and retention
- at least 1mm wide and deep
- 0.5mm to 1mm away from the finish line
- spaced around the tooth
what do proximal grooves do
shorten the radius of the arc of rotation
walls of a groove or a box are best placed:
perpendicular to the displacing forces
how can box form be used for retention
- remove caries
- convert caries removal into a box form by squaring walls
- not needed on intact walls
- box should be well into dentin to resist displacing forces
when two boxes are needed, less than 180 degrees of tooth circumference remains:
- this poses a great risk for cuspal fracture
- use a build up and full crown to protect against fracture
what is the risk with placing margin more apical
invading the biological width
what do you need to remember to do with a build up
finish line needs to be on tooth structure and you still need at minimum 2-3mm of ferrule
how do you remove biological width restriction
crown lengthening
what does orrthodontic extrusion do
extrude the tooth out of the bone to gain some height
describe a core build up
-replaces lost tooth structure to improve retention of a crown
- a core must be anchored firmly to the tooth and not just palced to fill the void
- retention for a core is often with the use of pins
when is a build up needed
when more than 50% of tooth structure is lost
what are the build up guidelines
- short axial walls: repeated de cementation of crown
- excessive interocclusal distance- needs pin retained core
- crown margin needs to be on sound tooth structure
describe amalgam as a build up material
not retentive but strong
- compressive strength
- dimensional stability
- corrosion- sealing
- isolation technique less senstivie
- often used in RCT teeth into canal for strength
describe composite as a build up material
retentive but not as strong
- bonds to tooth structure
- still needs help with pins
- tooth prep at same visit
- ease of manipulation
- can be thinner than 2mm
- color of material aids in crown matching
when is the use of a pin recommended in a build up
if 1/2 or more of the clinical crown has been destroyed
when should cusps be shortened or removed in a build up
if 1/2 their height are weak
for amalgam core, the cavity floors and walls should be _____
flattened
crown margins in a build up should be at minimum ________ material margin
1mm apical to build up
what are limitations with an amalgam core build up
- matrix placement can be difficult if tooth is severely broken down
- slow setting material:10-15 mins before removing band
- no bonding or natural retention
- requires at least 2mm thickness
- color shows through some ceramic crowns
- final crown prep occurs another day
what are the limitations in using composite as a core build up material
- technique sensitive
- isolation can be challenging
- microleakage posssible as material shrinks when cured
what is the rationale for pins
- pins are helpful to support the build up material when residual tooth structure does not provide adequate retention itself
- pins increase resistance for build up support
- the resistance is both internally and apically
- pins should be placed non parallel
what are the guidelines for pin placement
- place in sound, healthy dentin
- do not damage or undermine nearby enamel
- angulatin can create problems. avoid perforations or pins into the pulp
what happens if the pin is placed in unhealthy dentin
the threaded pin will not bite and will just spin in the hole and or fall out
how much enamel should be left in pins
-flat area of placement
- 0.5 to 1mm from DEJ or axial wall
- at least 0.5mm of dentin should surround the pin
what problems do pins introduce
-dentin stresses creating micro fractures
- microleakage around the pin
what are the guidelines for pin placement
- best used in line angles of posterior teeth to avoid furcation , perforations and the pulp
- 1 pin per missing cusp, line angle, or axial wall
- at least 5mm of space between pins
- max of 4 pins per tooth
what is the pin placement procedure
- use pilot drill to make pilot hole, depth gauge is on the drill
- use slow speed
- watch angulation and position
- using filpin latch pin and slow spped handpiece, place pin just in hole, then full rheostat power
- the pin will snap off at the area of the shaft that has been scored
- the teeth of the pin should engage in the dentin
- the pin should not be mobile or able to be easily pulled out
describe the self limiting twist drill
- cutting tip and helical flutes
- 2mm deep
- one motion without stopping
- too much wobble or imperfect handpiece technique creates a pilot hole that is too wide
if the pin is mobile or pulled out:
the dentin is either still decayed or too soft to support a pin
how can pins create non parallelism
bend them
where should pin be during bending
in dentin
how do you bend the pins
bender instruments
pins placed in dentin should:
- be 2mm deep into dentin
- be 2mm coronal into build up
- minimum 1mm radius of build up still around pin after preparation is done
what do you do once pins are placed
- place matrix around prep
- build up can be placed
- matrix is removed and now crowm prep can proceed
what are the pin complications
- fluted root shape
- furcation
- pulp penetration- RCT needed
what do you do if pin exits tooth surface above bone
flap and smooth to tooth contour
what do you do if fractured pin
move to another location 1.5mm away
what do you do if stripped pin
use a larger sized pin
what are bases used for
to protect pulp in teeth that have excavations that are deep and near the pulp
- to fill undercuts when an entire build up is not needed
describe the strength of bases
-weaker materials that do not provide strength like a build up
- not strong enough to support grooves, boxes or other retentive features
what are the materials for bases
- polycarboxylate cement
- glass ionomer cement
- resin modified glass ionomer cement
- silver reinforced glassed ionomer cement
what liner is used with bases
CaOH- dycal
what is the common protocol/steps for bases
- gluma (gluteraldehyde): 2 x60 sec coats
- dycal/calcium hydroxide
- vitrebond
- glass ionomer
- routine restoration steps
what is the sequence of treatment for extensively damaged teeth
- evaluate periodontal and endodontic health
- remove all caries or old restorations
- re evaluate your prep
- restore
