Principles of caries removal and cavity preparation Flashcards
what is cavity design determined by?
> structure and properties of the dental tissues
diseases (such as caries, periodontal problems, tooth surface loss)
properties of restorative materials
who is the father of modern dentistry?
G.V. Black
what did the father of modern dentistry believe?
> there was different classes of caries depending on location of the caries
the same shape could be made in whatever location the caries was
he did not take into account the nature of how caries spreads
the system he discovered only worked for amalgam
the use of this particular class system meant more tissue was removed than neccessary
NOT THE SYSTEM WE USE NOW
what is there a strong relationship between / what factors should be reviewed and considered during every restoration?
> the position of the caries
the extent of the caries
the shape of the prepared cavity
the final restorative material
what are the classifications we use for the position of caries?
> pit and fissure
occlusal surfaces
upper lateral incisors
> approximal
between teeth
either posterior or anterior
> smooth surface
> root
when should you intervene for caries removal?
- when lesion is cavitated
- when patient can’t access the lesion for prevention
- lesion has spread to the dentine (radiograph)
- lesion is causing pulpitis
- lesion is unaesthetic
what is pulpitis
inflammation of dental pulp tissue
what enamel factors should be considered for cavity prep?
> brittle
sharp along prisms
dry tissue (low water content)
unsupported enamel / enamel under the occlusal load should never be left in a restoration or it will fail
what do you need to consider when performing operative procedures involving the dentine
how it may impact the pulp
what dentine factors should be considered for cavity prep?
> porous
> more elastic
what gingival tissue factors should be considered for cavity prep?
> is it inflamed with plaque
> margins should be easy to clean
there are loads of operative management diagrams to look at on the lectures xoxox make sure you know these
apologies for another shocking slide by lp x
know
> side cut prisms
>end cut prisms
>occlusion and prism orientation - marginal integrity
>primary dentine - open tubules
>tertiary dentine - irregular structure
what should be considered when making the cavity?
> the effect on bonding to materials >enamel contamination >protection of pulpal theruapetuic agents >risks of micoleakage >risk of secondary caries
what should you check for when assessing the quality of the proposed dentine bond?
> dead tracts > secondary dentine >tertiary dentine >sclerosis >calcification
what are dead tracts in dentine?
when the dentinal tubules are opened / sufficiently irritated, their contents coagulate and die (degenerated odontoblastic processed
what is sclerosis in dentine?
abnormal hardening of body tissue
what is calcification in dentine?
the hardening of tissue or other material by the deposition of or conversion into calcium carbonate or some other insoluble calcium compound
what are the different types of dentine
primary
secondary
tertiary
where are the different locations of dentine?
intratubular
intertubular
peritubular
what should be considered when thinking about the nature of dentine?
different types different locations diameter density contents / mineralisation
what are the principles of preparation driven by?
- remove the caries
- necessary finishing of filling the cavity
2a maximising adhesion (so bond wont break)
2b occlusal relationship
2c ease of patient cleaning - so secondary caries is avoid
2d properties of the materials used (resilience, appearance, ease of use)
what are the situations when healthy tooth tissue may be removed?
> material used for the restoration requires it
(certain materials bond better with different parts of the tooth)
margins of the cavity are in contact with another tooth surface
the margins of the cavity cross an occlusal contact (may need to remove good tissue to access bad tissue)
name the 6 principles of cavity preparation
- find and remove carious enamel
- remove enamel to identify the maximal extent of the lesion at the ADJ and smooth enamel edges
- progressively remove peripheral caries in dentine (from the ADJ first and then circumferentially deeper)
- only then remove the caries over the pulp
- modify the outline shape of the cavity
- enamel finishing
- occlusion
- requirements for material - internal design modification
- internal line and point angles
- requirements for material
define cavosurface
relating to the wall of a cavity and the natural surface of a tooth
define line angle
between the wall and the floor of the cavity
what are the requirements of a final cavorsurface margin
> remove unsupported enamel
smooth cavosurface margins and line angles
outline form should be smooth and rounded
no excessively acute line angle transitions
check for stress concentrators
how should the final cavity design be completed?
> if there was an existing restoration ensure no traces of the restoration materials remain
smooth external sharp line or point angles
create an appropriate cavosurface margin angle
remove internal dentinal sharp line or point angles
check for stress concentrators
what points are included in the final seal of a restoration which are considered critical
- smooth margins
- appropriate CSMA
- no unsupported tooth tissue
- no stress concentrators
- internal anatomy that allows adaption of material
- clean cavity (free from debris)(should also be dry)
explain the first principle of caries removal
access
> remove overlaying enamel with a high speed bur to gain access to carious dentine
> follow caries at ADJ
> do not extend into non-carious areas
do you always have to remove hard discoloured dentine? h
why
don’t have to remove it if it is hard as you are still able to bond to it
consider properties of discoloured dentine
leaving this dentine can be a way to protect the pulp
explain the second principle of caries removal
extent
> caries spread at the ADJ determines outline form
> encloses extent of caries
> clear all caries at ADJ
> smooth enamel CSMA
> examine adjacent contact for caries
> avoid trauma / damage of adjacent tooth
what is the best way to remove an existing restoration
> use high speed bur
never remove by cutting at edges - this will increase the cavity size excessively
start at centre and cut towards edge
try to chip out chunks of restoration where possible
remove all the restoration and any underlying base material
explain the third principle of caries removal
remove dentinal caries
> caries will be detected as a brown stain or softened tissue when using a sharp probe
> anything sticking to the probe indicates residual carious dentine - this needs to be removed
> do not prove uncavitated carious enamel
> only leave stain if it is hard to probe
> remove from the ADJ first, then the peripheral dentine and lastly from the pulpal floor
what can caries be removed using
> hand held excavator > round bur > chemo-mechanical caries removal > caries detector dyes may be helpful > a chisel is slower but safer than using a slow speed bur when working at the pulp
how should caries on the pulpal floor be removed?
> remove last
use the largest instrument which will conveniently work in the cavity
- large round bur
- large hand held excavator
- chemo-mechanical caries removal
small burs and excavators will cut deeply more quickly so higher risk of pulp exposure
explain the 4th principle of caries removal
modifications >once caries removal is complete decide on material >modify the cavity as appropriate consider: - enamel margins - CSMA - occlusion - internal anatomy - dentine quality
what are your options of restorative materials for direct plastic restorations
- composite
- amalgam
what are advantages and disadvantages of composite
adv
- good appearance
- conserves tooth tissue
- supports remaining tooth tissue
- adhesion (bonds to etched enamel walls well)
- command cure
- low thermal conductivity
- elimination of galvanism
d-adv
- operator sensitive
what is galvanism
electricity produced by chemical action
how is amalgam held into the cavity?
by retention and resistance
what are the advantages and disadvantages of amalgam
adv
- strong under occlusal load
- less moisture and technique sensitive
- prevented from fracture by adequate bulk (at least 2mm deep)
d-adv
- does not bond to enamel / dentine
- does not support the tooth
- need to remove healthy tissue
- not tooth coloured
what is retention
features of the cavity which prevent the restoration from being dislodged in an occlusal direction
what are anatomical cavity design features of using amalgam
undercuts dovetail key isthmus these arent needed for adhesive restorations
what is an undercut?
internal dimensions of the cavity greater than access into it
needed for nonadhesive restorations
what is a bevel
a slope from the horizontal or vertical in carpentry and stonework; a sloping surface of edge
what is a line angle
the junction of 2 surfaces of the crown of the tooth or a tooth cavity
what is a point angle
formed by the junction of 3 surfaces
what are the requirements of a cavity margin in an amalgam restoration
all cavity margins should be
- caries free
- free of contact with the adjacent tooth
- accessible for cleaning
how should the cavity margin / restoration be designed?
be designed for maximum strength and minimum leakage
generally, what is the cavosurface angle for amalgam
90-120 degrees
Butt joint
(diagram is good to know in lecture xo)
explain high configuration factor
increased polymerisation contraction stress = bad
explain low configuration factor
reduced polymerisation stress = good
there are also diagrams to do with this but i don’t know how to Q them but it is to do with the restoration failing due to enamel and composite not adhesiving correctly
what will the cavity contain after prep
- loose enamel and dentine chippings
- organic and inorganic dentine debris smeared into the walls of the cavity
explain how to clean the cavity
wash cavity with a mix of air and water to remove the loose debris, rinse with chlorhexidiene and remove
rinse with water and leave surface moist
shouldn’t be dry
do you always have to remove all the caries?
no
- if it is very close to the pulp it can be left
- remove rest of caries
- treat with provisional restoration to see if pulpal caries will remineralise
- observe if the caries will cause patient pain / sensitivity
when do you decide on the material for the restoration
after caries removal
what do you consider when designing the cavity
the remaining tooth tissue
the quality
the choice of material
