Principles of cavity preparation and pulp protection Flashcards
Prevention is better than protection and we can cause trauma by..
Direct trauma - to odontoblasts cell processes during drilling
Indirect trauma - to odontoblasts due to dedication (drying)
Indirect trauma - to pulpal tissues due to temperature increase (burning)
Prevention vs protection - how to prevent damage
- light pressure
- low speed vs high speed
- sharp burs
- maintained handpiece
- water coolant
- rubber dam / isolation
- great care, especially with deep lesions
Why restore teeth?
- remove diseased tooth tissue (caries)
- restore integrity of tooth
- restore function
- restore appearance
The general principles of tooth preparation are determined by
Nature and extent of lesion - determined clinically/radiographically
Quantity and quality of the tooth tissue remaining after preparation
Functional load
Nature and properties of the restorative material used
Pulp protection following cavity preparation
3 different concepts
Protection from THERMAL stimulus with a BASE
- metal restorations
- fluid movement, not conduction causes pain
Protection from CHEMICAL stimulus with a LINER
- etched / bonded restorations
- prevention of micro leakage is important
More recent protection from BACTERIAL stimulus with a SEALANT
- inflammation due to micro leakage (bacteria) not the restorative material itself
- presence of bacteria is the single most important determinant factor of pulpal inflammation
Micro leakage
The passing of fluids, microorganisms or ions between the restoration and the adjacent preparation walls
Occurs around all restorations, including those that are adhesive lay bonded to enamel and dentine (due to hot cold)
Can result in a variety of clinical conditions
- marginal discolouration
- pulpal irritation
- necrosis
- sensitivity
- recurrent caries and eventual failure of restorations
Bacterial contamination
- initial various lesion
- during cavity prep
- during restoration placement
- smear layer
- micro leakage - after restoration placed
Pulpal sensitivity arises due to?
Changes in fluid flow !!
Normally slow outflow of fluid from dentine tubules
Change in temperature causes fluid flow changes
Brannstorms hydrodynamic theory
Cold / hot application = increase in flow and pain
Deeper dentine has more tubules = more permeable = more susceptible to changes causing change in fluid = more pain
Pulp protection
Aim is to prevent pain/sensitivity how?
Prevent micro leakage and thus bacterial induced inflammation and dental fluid movement and associated pain
Achieved by sealing dental tubules with a LINER / SEALER
Ideal properties
- pulp insulator
- infinite compressive strength
- biocompatibility with oral environment
- cost effective
- adheres to tooth - improve seal / prevent leakage
- expand and contract in harmony with tooth
- does not corrode or degrade
- not technique sensitive
Liners
Cement or resin coating applied as a thin layer
Less than 0.5mm to provide a physical barrier to the penetration of bacteria and their toxins
Seal cavity and have additional benefits eg, fluoride releases adhesion to tooth structure, anti bacterial
Provide a physical barrier to the penetration of bacteria and their toxins
More to treat dentine rather than protect the pulp
Calcium hydroxide and glass ionomer (resin modified)
Resin modified light activated glass ionomer
- ease of placement
- command set
- early resistance to moisture contamination
Calcium hydroxide
Has stimulators effect on odontoblasts
- useful for deep cavities (les than 2mm dentine remaining) encourages tertiary dentine formation
- bactericidal
- weka and soluble thus needs covering / protecting
Sealer
Seals dentinal tubules and provides a protective coating for freshly cut tooth structures of the prepared cavity
Amalgam restoration
Composite restorations
