Prep of a cavity Flashcards
What determines the design of a cavity?
structure and properties of the dental tissues
the diseases
properties of restorative materials
what was stereotypic thinking
caries was classified in classes and the class determined the shape of the cavity
why do we no longer use stereotypic thinking
as it resulted in the removal of healthy tooth tissues
why do we have to sometimes take out healthy tooth tissues if we are using amalgam
amalgam does not stick to the tooth therefore the bottom of the cavity has to be wider to lock it in
what must be continually reviewed and reassessed when preparing a tooth for restoration
position of the caries
extent of the caries
shape of the prepared cavity
final restorative material
what are the different classifications on the position of the caries
pit & fissure
approximal
smooth surface
root
why are pits and fissures prone to caries
the depths of these can cause susceptibility to caries as patients struggle to clean these areas resulting in accumulated plaque
what are the different types of approximal caries
posterior
anterior
what are the different types of smooth surface caries
can be caries or erosion/abrasion/abfraction/hypoplasia
what is approximal caries due to
the surface of particularly crowded teeth can be more susceptible due to the lack of access for oral hygiene aids
what is root caries
root caries is caries on an exposed root which often penetrated more easily into the exposed dentine
what are the different stages of caries
it has an initiation and development
carious lesion forms as a direct consequence of the metabolic activity in the biofilm, if factors tip the de/remineralization balance towards demineralization, the stages of progressive lesion formation leading to cavitation can be clinically detected
what should operative treatment be done with the context of
prevention
when should operative intervention be done
o When the lesion is cavitated
o When the patient can’t access the lesion for prevention
when should a restoration be considered
o The lesion is into dentine radiographically
o The lesion is causing a pulpitis
o The lesion is unaesthetic
why is a restoration not a positive thing
placing a restoration puts the patient into the restorative cycle
what is the restorative cycle
describes the unintended consequence for all operative procedure’s which is to place the patients tooth into the restorative cycle which will continue throughout the life of the patient
describe briefly the structure of enamel
prismatic structure
what are the different cut of prisms when cutting enamel
side cut prisms or end cut prisms
why does resin composite adhere to enamel
it is a dry tissue - the ultrastructure of enamel permits the adhesion successfully
what should be removed before a restoration is placed
any unsupported enamel and/or under occlusal load
what is important to consider in terms of the dentinal-pulp complex
Operative procedures involving dentine affect the pulp
describe briefly the structure of dentine
dentine is porous
more elastic
wet tissue
why is dentine more difficult to adhere to
Because dentine is innately wet and so this becomes a problem that must be overcome during operation as the composite is hydrophobic
what is the difference between primary dentine and tertiary dentine
tertiary dentine occurs in chemical and biological trauma while primary dentine has big open tubules and it is not as mineralized
what should be assessed before bonding dentine
quality of the proposed dentine
what are you looking for when assessing dentine
dead tracts secondary dentine tertiary dentine sclerosis calcification
what are the different types of dentine
intra, inter and peritubular dentine
how can dentine vary
Tubules can have different diameters
There are different densities of dentine
Different levels of mineralization with the dentine
what is intratubular dentine
dentine within the tubules
what is intertubular dentine
dentine between the tubules
what is peritubular dentine
dentine that makes up the walls of the tubules
when can you remove healthy tooth tissue
o The material used for the restoration requires it
o The margins of the cavity are in contact with another tooth surface
o The margins of the cavity cross an occlusal contact
what are the steps to cavity preparation
- identify and remove carious enamel
- remove enamel to identify the extent of the lesion at the ADJ and smooth the enamel margins
- progressively remove peripheral caries in dentine
- only then remove deep caries over the pulp
- outline form modification (enamel finishing, occlusion, requirement of restorative material)
- internal design modifications (internal line and point angles, requirements of the restorative materials)
what is a wall
any surface of the tooth preparation is referred to as a wall
what is the cavosurface angle
formed by the junction of a prepared tooth surface wall and external surface of a tooth
what is a line angle
a junction of two surfaces of different orientations along the line and its name is derived from the involved surfaces
what is a point angle
junction of 3 plane surfaces or three line angles of different orientation and its name is derived from its involved surfaces or line angles
what do stress concentrators do
allow a crack to spread
what can a sharp line angle lead to
a potential crack
what are the final steps in the final cavity design
ensure no traces of restorative material remain
smooth external enamel sharp line or point angles
create appropriate cavo surface margin angles
check for stress concentrators
what is the first principle
access caries
what are the steps to accessing caries
apply a dental dam
remove overlying enamel
follow caries at the ADJ
do not extend to non carious areas
if you find discolored dentine that is hard what do you do
do NOT remove it
how do we access inter proximal caries
via healthy enamel through palatal side and move forwards to labial and gingival side
what is the second principal
extent
what determines the outline form
how the caries has spread at the ADJ
what are the steps of these second principle
clear all caries at ADJ check staining at ADJ smooth enamel cavo-surface margins examine adjacent contact for caries avoid trauma to adjacent tooth
when do you remove dentine
if dentine sticks to probe
how do you remove restorations
high speed bur - start at centre and cut towards the edge
cut restoration into pieces
what is the 3rd principle
removing dentinal caries
what is dentinal caries detected as
brown stain or soften tissues when using a SHARP probe
any sticking of the probe indicates residual carious dentine which should be removed
what caries should be removed first and which last
residual carious dentine must first be removed from the ADJ and last from the plural floor
what instruments should be used when removing caries from the ADJ
hand held excavator
round bur
what instruments should be used when removing caries on the pulpal floor
large round bur
large hand held excavator
why should we use large instruments when working on the pulpal floor
small burs and excavators will cut more deeply more quickly which gives a risk of pulp exposure
what is the fourth principle
modification
what happens in the fourth principle
Once caries removal or removal of an existing restoration is complete then the material to be used can be decided and the cavity should be prepared appropriately
what are the advantages of composite
o Aesthetics o Conservation of tooth tissue o Support for remaining tooth tissue o Adhesion/bonding o Command cure o Low thermal conductivity o Elimination of galvanism o Amalgam alternative
what are the disadvantages of composite
operator sensitive
what are the disadvantages of amalgam
o Does not bond to enamel or dentine
o Does not support the tooth
o Held into the cavity by retention and resistance form
o Cut dentine may require sealed resin layer
o Amalgam is prevented from fracturing by adequate bulk, needs to be at least 2mm deep
what are the advantages of amalgam
o It is strong under occlusal load
o Not tooth coloured
o Less moisture and technique sensitive
what is retention
Features of the cavity which prevent the restoration being dislodged in any occlusal direction
what is the cavosurface angle for amalgam
90 degrees and 120 degrees
what is the configuration factor
number of bonded surfaces to the number of unbonded surfaces in a dental restoration
what does a high configuration factor mean
leads to increased polymerization contraction stress
what does a low configuration factor mean
reduced polymerization contraction stress
what should be done after preparing the cavity
Wash the cavity with a mixture of air and water to remove the loose debris, rinse with chlorhexidine and remove
Rinse with water and leave surface moist
