Principles of cavity preperation and pulp protection Flashcards
Direct trauma-
Indirect trauma (Dentine)-
Indirect trauma (pulp)-
Direct Trauma- to odontoblasts cell process during cutting (drilling)
Indirect trauma- to odontoblasts due to desiccation (drying)
Indirect trauma- to pupal tissues due to temperature increases (burning)
Basic principle of pulp protection
Light pressure Low speed vs high speed Sharp burs maintained handpieces Water coolant Rubber dam/ isolation Great care, especially with deep lesion Isolation- rubber dam
Why restore teeth?
Remove diseases tissue (caries)
Restore the integrity of the tooth surface
Restore the function of the tooth
Restore the appearance of the tooth
Blacks cavity-
Based on the principle-
Key feature-
Cavity design was based on amalgam, relied on mechanical retnetion= undercuts, divergent walls, slots, grooves etc.
To achieve this the cavities tended to be large
Based on the principle of removing caries then running out all fissures and pits ( prevent spread) extension for prevention
Very prescriptive - almost identical cavities
Current philosophy
General principle of cavity prep are determined by:
The nature and extent of the lesion ( clinical and radiograph)
The quantity and quality of the tooth tissue remaining after the preparation
Functional load
The nature and properties of the restorative material used
Current Philosophy step by step:
Key feature:
Step by step
Gain access- high speed
Remove caries- slow speed and hand instruments
Remove infected dentine but may leave affected dentine must clear the ADJ first
Stop, look and think!
Consider materials/aesthetic/occlusal load ect
Complete cavity form to required specifications
Non prescriptive- cavities all different
Amalgam will require…..
The choice of material will influence……
If a non-adhesive restoration is to be placed
If an adhesive restoration is to be placed
….. more cavity modification than adhevsive materials, but with improved amalgams and modern retentive techniques (ie bonded amalgam) not as much as black method
……. the final form of the cavity preparation, particularly the Cavo-surface angle (more critical with amalgam restoration) and presence of retentive features (more required with non-adhesive restoration)
………. some additional mechanical retention must be included in the preparation- theses include undercuts, grooves, boxes etc. Beware involve removing sound tissue
………….much less modification is required. Conserve sound tissue
Pulpal protection 3 concepts
Protection from thermal stimulus with a base- metal restoration
Protection from chemical stimulus with a liner- etched/bonded restoration
More recent protection from bacterial stimulus- well-sealed restoration
History - Direct thermal shock to the pulp
Use to think that temperature changes in the oral cavity transmitted to the pulp through restorative material, especially when remaining dentine is thin, therefore need to place and insulting base, but it was thought the presence of large bases weaken the overlying restoration
Present knowledge- Direct thermal shock to the pulp
Fluid movement, not conduction causes pain
Occlusion of open dentine tubules becomes the operative factor in protecting the pulp and reducing thermal pain, rather than a thick insulating base
Prevention of microleakage is very important
History of chemical
Now known as….
Initially though that primary cause of pulpal inflmation was related to the cytotoxic effect of the restorative material
Therefore protective liner to prevent effect of material
Now known as mild and transitory
Chemical- what is the most important factors
The remaining dentine thickness is the most important factor
0.5mm-1mm remaining dentine reduces toxicity levels of materials by 75% and 90% respectively
Dental materials may cause verying degress of irritation to the pulp, the pulp can usually recover provided bacteria and their toxin are excluded
Again - prevention of microleakage is very important
History- bacteria
Inflammtion due to microleakage (bacteria) not the restorative material itself
Presence of bacteria is the single most important determinant factor of pupla inflammation
Causes of Batcerial contamination:
Initial caries lesion During cavity preeration During restoration placement Smear layer microleakage
Microleakage is
the passing of fluids, microorganisms or ions between the restoration and the adjacent preparation walls
Occurs around all restorations, including those that are advisedly boned to enamel and dentine
Can result in a variety of clinical condition- marginal discolouration, pulpal irritation and necrosis, postoperative sensitivity, recurrent caries and eventual failure of the restoration
Reducing microleakage is key
Hydrodynamic theory
Normally slow outflow of fluid from from dentinal tubules, change in temperature causes fluid flow changes
Pulpal sentivity arises due to changes in fluid flow
Cold/hot application leads to increases flow and pain
Hydrodynamic theory- Dentine
Deeper dentine has more tubules, more permeable, more susceptible to changes causing changes in fluid flow, resulting in more pain
Dentine is the most effective base and should not be removed to accommodate a cement
Conservative dentistry- keep preparations as minimal as possible
Amalgam restoration (just a guide) Minimum (just in to dentine)=
Moderate ( more than 2mm of dentine remaining) =
Deep (less than 2mm of dentine remaining)=
sealer dentine sealer/bond
sealer and liner, resin modified GIC and/or dentine sealer/bond
sealer and liner Ca(OH)2 if v deep. Resin modified GIC and/or dentine sealer/bond
Bonded amalgam
Composite Restoration (just a guide) Minimum (just in to dentine)=
Moderate (more than 2mm of dentine remaining)=
Deep (less than 2mm of dentine remaining) =
sealer dentine bonding agent
sealer and liner Resin modifed GIC? Dentine bonding agent
sealer and liner Ca(OH)2 if v deep, resin modified GIC, dentine bonding agent
Stepwise managment
Sealing the cavity has additional benefits, such as….
Lining materials still have……..
…fluoride release, adhesion to tooth structure, antibacterial
Provide a physical barrier to the penetration of bacteria and their toxins
……….. therapeutic effect that can be useful
More to treat dentine rather than protect pulp
Calcium hydroxide and glass ionomer (resin modified)
Resin modified light acitived glass ionomer….
Calicium hydroxide………
…Gained increase popularity, ease of placement, command set, easily resistance to moisture contamination
……Has stimulatory effect on odontoblasts
Useful for deep cavities (less than 2mm dentine remaining) to encourage the formation of tertiary dentine
It is also bactericidal
Is weak and soluble, thus needs covering/protection
Define Base
- a material usually a type of cement, used in a prepared cavity before the insertion of a permanent restoration, to protect the pulp
Define Liners
Liners- cement or resin coating applied in thin layers (<0.5mm) to provide physical barrier to the penetration of the bacteria and their toxins with certain therapeutic benefits
Define sealers
Sealers- material, typically film forming agent, which seals the dentinal tubules and provide a protective coating for freshly cut tooth structure of the prepared cavity
Pulp protection- 3 types
Bases (historic)
Liners
Sealers
Ideal properties of pulp protector material:
Pulp insulator Infinite compressive strength Biocompatibility Cheap? Adheres to tooth surface- improved seal Expands and contracts in harmony with the tooth Dies not degrad or corrode in the oral enviroment Not technique sensitive
5 Key Principles
There is no material that can protect the pulp as well as dentine
The most adverse consequences to the pulp occur as the result of pulpal invasion by bacterial and/or their toxins
The most significant causative factor of pulpal pain is the hydrodynamic movement of pulpal fluids
No two clinical situations are identical: therfore apply basic prinicpples and apply to the specific circumstance
Prevention is better than protection, a large amount of pulpal inflammtion arises during cavity preperation, remeber dentine is a vital tissue
