MI Flashcards
Classifications
- Mount & Hume
- GV Black
Mount & Hume
Site 1: occlusal only
Site 2: involves proximal surface
Site 3: cervical margin
Size 0: initial demin. includes arrested lesions.
Size 1: minimal cavitation. dentine involvement.
Size 2: moderate dentine involvement, tooth strong enough to support restoration
Size 3: Large, tooth structure very weak, requires protection from restoration
Size 4: Bulk loss, extensive loss of tooth structure - loss of cusp/incisal edge.
- GV Black
Class I: occlusal only
Class II: proximal only
Class III: proximal of anterior teeth
Class IV: incisal edge of anterior teeth
Class V: cervical region
Class VI: cusp replacement
Materials
CR, Amalgam, GIC/RMGIC
CR
Good aesthetics
Can withstand occlusal load
Resistant to abrasion and fracture
Good longevity
Micromechanical bond to the tooth, prep can be conservative
Moisture sensitive
Not as strong as amalgam
Not biocompatible if unpolymerised
Amalgam
Best at withstanding occlusal load
Not moisture sensitive
Good longevity
Fractures if too thin
Conducts heat
Susceptible to corrosion
Environmental toxicity concerns
Aesthetics
Prep cannot be conservative - Requires extensive removal of tooth structure for adequate macromechanical retention
GIC/RMGIC
Biocompatible
Remineralising properties - F- reservoir
Not moisture sensitive
Chemical bond to E & D - true bond - (acid-base setting reaction) → must protect frm water during setting reaction as uptake/losing water reduces physical properties
Poor longevity
Cannot withstand occlusal loading
Aesthetics
Fuji
RMGIC
Fuji 2
Riva LC - slower setting
GIC
Fuji 7 - GIC - pink, easy to see and remove
High amts of F
f/s on primary dent, for partially erupted perm teeth
Fuji 9 - GIC
Base, cervical R: less F but stronger
Dentinal hypersensitivity - how it arises + causes
HYDRODYNAMIC THEORY:
Patent dentinal tubules - thermal stimulus causes fluid inside dentinal tubules to move, which is interpreted by mechanoreceptors in the pulp as pain
Requirements for sensitivity
Patent dentinal tubules
Exposed dentine
Vital pulp - mechanoreceptors for dentinal pain r in pulp!
Stimulus that causes dentinal fluid mvmt
Causes of dentinal hypersensitivity
Caries ingression, exposure of dentinal tubules
Erosion - acid wears away enamel, exposes dentinal tubules
Abrasion - mechanical tooth wear of the protective enamel
- ‘abfraction’ = teeth flexing under load causing breakdown of the CEJ → wedge-shaped lesion
Dentinal hypersensitivity - management
Chemical:
Occlude dentinal tubules - SnF2 (Arginine/Novamin/Strontium acetate)
Forms precipitate that seals tubules > interferes w stimulus ability to make dentinal fluids move → immediate relief
Block nerve activity - KNO3
Desensitisation of nerve fibres’ ability to conduct action potentials
Needs >2wks of continued use for effect - more for maintenance. - takes longer to take effect but lasts longer, will keep protecting after mechanical occluding agent wears off
Use both
Physical
Restoration
Protective covering
G bond/G coat, RMGIC lining
Unfilled resin not as suitable as Hphobic.
Remineralising agents - Duraphat, Tooth Mousse
Laser - low intensity blocks pain stimulation, high intensity occludes tubules
ADDRESS CAUSE.
Pulpal health
Stages
Reversible pulpitis
Sharp pain to mostly cold, very brief
Irreversible pulpitis
Can be localised or systemic to around surrounding tissues
Pain typically dull and aching esp to hot, lingers after removal of stimulus
Pulpal necrosis
Non-vital pulp - can be very tender, pain to pressure
Heat or cold does not exacerbate since its DEAD.
Could have abscess forming - ‘pimple’ on gingiva
Causes for pulp irritation/damage
Same: pH change from caries ingression, erosion
Attrition and erosion
Trauma
Iatrogenic - mechanical pulp exposure during cavity prep
Thermal irritation - friction from polishing, Light Cure
Poor biocompatibility - CR placed too close to pulp - HEMA toxicity
Pulp capping
Indirect pulp cap
Remove most of infected dentine, cleaning the DEJ completely, but leave some infected dentine behind where it is close to pulp
Risk of pulpal sequelae - depends on pt’s pulp ability to recover - inform pt
Leave for 6 weeks and observe production of reparative dentine/sclerotic dentine
If pulp has migrated apically, can remove rest of infected dentine
Old method: CaOH → IRM. Alkaline CaOH kills bacteria and causes necrosis of tissues, prompting pulp to release reparative dentine.
New method: RMGIC, forms chemical seal. F- release remineralises tissues and arrests caries. After 3 mths, cut back and restore w CR.
Direct pulp cap
With small pulpal exposure
High chance of success if pulp is not inflamed
Otherwise, have to stop bleeding w pressure w sterile cotton pellets +/- astringedent/hemodent (bleeding increases contamination risk)
CaOH cement
Stimulate calcific bridging (fibrous tissue produced by the pulp)
MTA (mineral trioxide)
Stimulate dentine bridging - fewer tunnel defects and higher success but more costly
=> Restore with RMGIC → then final restore.
Metals in dentistry
Pros
Pros of metals:
Withstands high stress day-to-day
Longevity - Resistant to wear, withstands effects of fatigue and accumulated stress cycles - very good service longevity
Osseointegration - titanium implants
Metals in dentistry
Cons
Thermal conduction → pulpal irritation
Corrosion
- Crevice corrosion - localised electrochemical process that occurs in narrow spaces because of changs in pH eg acidification from microleakages
- Galvanic Corrosion - corrosion of less noble metal in presence of more noble metal - occurs where electrochemically dissimilar metals are in contact through a corrosive liquid environment
When pt w amalgam bites down on aluminium foil - sharp pain - Tarnishing - surface of metal becomes dull due to formation of sulphide or oxide layer on surface
Consequences:
Roughening of surfaces
Weakening of restoration, release of elements from the dental alloy, like Ag which causes discoloration of soft tissue and allergies in certain pts
Fracture of implants
Protecting from corrosion
Highly polished restorations
Coating with non-conducive substance
Cover with layer of noble metal - gold, platinum
Passivating with protective layer of chromium
Electroplating with nickel, then chromium, to form stainless steel
Titanium implants
Titanium readily passivates to form stable TiO2 layer which protects it from corrosion
Titanium is inert and immune to attack from biological fluids, is not recognised as a foreign body by the immune system, allowing fo endo-osseointegration - compatible with bone growth
Titanium absorbs biological fluids (collagen, albumin, glycosaminoglycans, fibrinogens)
Strong and flexible, anchors implant firmly to the bone
