key Rx things to learn Flashcards
determinants of cavity design
structure and properties of dental tissues
diseases
properties of Rx materials
principles of cavity design
1 - identify and remove carious E
2 - remove E to identify max extent of lesion at ADJ and smooth E margins
3 - progressively remove peripheral caries in D - from ADJ first and then circumferentially deeper
4 - only then remove caries over pulp
5 - outline form mod: E finishing, occlusion, requirements of Rx material
6 - internal design mod: internal line and point angles, requirements of Rx material
in what instances can you leave a small amount of carious D overlying the pulp?
risk of pulpal exposure high
good Rx seal can be achieved
pulp asymptomatic
affected D
softened
various levels of demineralised D that is not yet invaded by bacteria
inner carious D (does not require removal)
has sensitivity more pulpally
does not stain acid red with propylene glycol
should be left to remineralise
infected D
outer carious D, bacterial plaque softened and contaminated with bacteria highly demineralised, lacks sensation stains acid red colour with propylene glycol should be excavated
when to intervene in a lesion
if cavitated pt can't access it for prevention aesthetics causing pulpitis into D on xray
aims of cutting through E to gain access to carious D
1 - gain visual access to carious D requiring removal
2 - remove demineralised and often unsightly carious E
3 - create a sound peripheral E margin to which adhesive Rx can form seal
composite cavity design
no US E
no sharp internal LAs
bevel CSMA to increase area for bonding - composites adhere and support E
- so a light bevel increases SA for bonding and removes any US E at cavity edge
2 types of extent of D caries
anatomical extent of lesion - peripheral caries to caries overlying pulp at level of ADJ
histological depth of lesion - collagen and mineral content of carious D
peripheral caries and why should you never leave necrotic D at ADJ?
prevention of secondary caries entirely dependent on seal between Rx material and tooth at cavity periphery
should never leave necrotic D at ADJ - can’t be adhered to
configuration factor
ratio of bonded to unbonded surfaces
high = increased polymerisation contraction stress
contraction stress consequences
poor E prep margin
composite dimensional change
etch bond stronger than interstitial E strength
composite will fracture with weak E and D attached
cavity toilet phenomenon
cavity will contain loose E and D chippings following prep
wash out mix air, water, CHX
rinse and leave moist
CSMA
angle of tooth structure formed by the jct of a prepared (cut) wall and the external surface of a tooth
- jct - CSM
line angle
jct of 2 surfaces
point angle
jct of 3 surfaces
hybrid layer
resin impregnated D layer
5 requirements of occ stability
1 - stable contacts on all teeth of equal intensity and centric relation
2 - anterior guidance in harmony with envelope of fct
3 - disclusion of all posterior teeth during mandibular protrusive movement
4 - disclusion of posterior teeth on NWS during mandibular lat movement
- disclusion of posterior teeth on WS during mandibular lat movement
subalveolar fracture makes tooth unrestorable
lack of coronal tissue to bond to/support/retain Rx
inability to achieve moisture control for Rx
inability to take imp for indirect Rx
hard to establish marginal integrity
difficulty cleaning
causes of secondary caries
marginal failure of an existing Rx poor adaptation of Rx material fracture of US E leaving exposed area amalgam ditching of margins failure to remove all of initial lesion
reasons Rx fail
poor material selection
- e.g. amalgam and gold Rxs near each other can cause corrosion due to galvanic activity
incorrect cavity rep
material manipulation
oral env
- access, thermal changes, forces, microbes, aq
manifestations from a traumatic occlusion
fracture of Rxs/teeth mobility odontogenic pain not from infection TW may be associated with TMD
Nayyar core
retention obtained from the UCs in the divergent canals and pulp chamber
2-4mm GP removed from canal and replaced with amalgam
immediate placement and coronal prep can be done at same appt
methods for fractured post removal
US masseran kit cut out for fibre posts stieglitz forceps eggler post remover sliding hammer
3 types of contact
cusp tip to base of fossa
tripod contacts
- 3 points on the cusp engage 3 points around the fossa
unfavourable contacts
- on cuspal inclines (induces unfavourable lateral forces on teeth)
- none at all
options for immediate anterior tooth replacement
adhesive cantilever with fractured tooth as pontic
provisional overdenture
provisional post-crown
vacuum formed splint w tooth
what is cracked tooth syndrome
tooth cracked but nothing has broken off
technically a type of GS fracture
S+S of cracked tooth syndrome
sharp pain when biting rebound pain when pressure released pain when in occlusion and excursion pain to cold but not to heat eating/drinking sugary not always able to localise to one tooth
cracked tooth syndrome investigations
tooth sleuth
gentian violet/methylene blue stain (2-5 days to work)
transillumination
radiographs - not v beneficial but good for pulpal and perio
cracked tooth syndrome tx
composite Rx/bond fixed ortho band round tooth core build up and crown RCT XLA
why obturate?
seal remaining bacteria
provide apical and coronal seal
prevent reinfection
primary D
laid down during development
good for bonding
open tubules
secondary D
laid down during fct
ok to bond to
tertiary D
reactionary due to mild stimuli and reparative due to intense stimuli
poor for bonding due to poorly organised/sclerosed tubules
transient sensitivity to thermal stimuli and pain on biting after large composite Rx
polymerisation contraction stress soggy bottom insufficient coolant on prep uncured resins entering pulp and causing irritation high in occlusion no lining pulp exposure fluid from tubules occupying space under Rx
debonded post
post fracture core fracture root fracture at post level when not attributed to trauma (stress release) untreatable caries traumatic fracture inadequate moisture control furcation perforation (due to D pins)
fracture at jct of post and core
tooth structure loss age induced changes in D biocorrosion of metallic post-core Rxs and restorative procedures loss of free water from RC snd dentinal tubules effects of endo irrigants and medicaments on D bacterial interaction inadequate ferrule trauma - bruxist pt
criteria before obturating
asymptomatic
canal must be able to be dried
full biomechanical cleaning
composite techniques
flowable at base to reduce contraction stress
incremental placement - low CF
2mm or less increments to avoid soggy bottom
amalgam cavity
UCs for retention other retentive features e.g. lock and key, grooves, dovetail, isthmus >2mm depth for sufficient strength flat occlusal floor CSMA 90 degrees no US enamel
causes of debonded post
incorrect cement
contamination during cementation
unfavourable occlusion
inadequate or over-tapered post prep
detecting debonded bridge
check visually
floss
probe
push on it and check for movement/bubbles
may see secondary caries/demineralisation
core fractured from post
casting error
inadequate ferrule
trauma
parafct
Hanau’s quint
used for setting teeth
handpiece safety
check backcap secure
tug tubing
pull bur hard
no lat movement/wobbliness of bur
smooth and no friction
run for 5s - sound
why not ledermix for direct pulp cap?
devitalising agent
consequences of high polymerisation contraction stress composite and how to avoid
shrinks
etch bond is stronger than interstitial E strength - leads to E fracture and failure
successive increments touching as few surfaces as possible - note final increments do not join E margins
CF
ratio of bonded to unbonded surfaces
stepwise
remove caries at periphery and ADJ remove infected D if you can give pulp time to repair and lay down D RMGI/GI over caries 6m later re-enter, remove hardened D (caries arrested as good seal), restore
why place flowable at base?
good adaptation and mediate contraction stresses
advantages of composite inlays/onlays
avoids open/poor contacts and poor proximal/occlusal morphology
avoids polymerisation contraction and stresses
avoids cuspal flexure
disadvantages of composite inlays/onlays
more destructive - UCs must be removed/blocked out
astringent
ferric sulphate
how to differentiate the 2 layers of dentine caries
solution of basic fuchsin
if pulp exposed?
caoh
if pulp not exposed?
RMGI
aims of caries removal
maintain pulp vitality
eliminate D infections by removing, deactivating or sealing in bacteria
conservation of intact tooth structure
should you bevel boxes for amalgam?
no
should you probe uncavitated carious E?
no
when can you leave a stain?
only if hard to probe - but must remove from ADJ
where is tubule density higher?
by pulp
composite where should you avoid CSMs?
in areas of occlusal contact
removing a Rx
never remove by cutting around the edges - excessively increase size of cavity
start from centre of Rx and cut towards edge
never remove healthy tooth tissue unless:
material for Rx requires it
margins of cavity in contact with another tooth surface
margins of cavity cross an occlusal contact
which fibres are stimulated in reversible pulpitis?
A fibres
which fibres are stimulated in irreversible pulpitis?
C-fibres
how do D tubules change as they approach the pulp
they increase in number and diameter
so deeper cavity = increased D permeability
