essay 16 - characteristics of the cavity as a dentin wound: status of the dental pulp, smear layer, medicatio cavi dentis - medicaments and properties (pharmacodynamics)

describe the characteristics of the cavity as a dentin wound

• a prepared cavity is considered a wound to the dentin as it involves the mechanical removal of tooth tissue

• This ‘wound’ affects the odontoblastic processes in the dentinal tubules and may result in pulp inflammation is not properly managed

• The dentin-pulp complex should be protected during and after cavity preparation to prevent irreversible pulp damage

describe the status of the dental pulp

• the pulp is highly vascular and innervated. It responds to injury with inflammation and if the injury is significant or prolonged, necrosis may occur

• Remaining dentin thickness is critical: thinner the remaining dentin, the greater the risk to pulp vitality

describe the smear layer

• it is a microscopic debris layer created during tooth preparation, composed of hydroxyapatite, denatured collagen and cutting debris

• It partially blocks the dentinal tubules, which can be beneficial (reducing sensitivity), but also harbours bacteria and reduces bond strength

• Its removal or modification is important in adhesive procedures as it can impede bonding

what does medicatio cavi dentis (cavity medication) involve?

• it involves disinfecting and protecting the cavity prior to restoration. This application of medicaments before restoration of a cavity. Although not a part of tooth preparation itself, cavity medication plays a key role in adapting the cavity for restoration, especially in:

— deep cavities

— situations with minimal remaining dentin

— cases where thermal, mechanical or chemical irritation could occur

what is the goal of medicatio cavi dentis (cavity medication)?

• to protect the pulp

• to promote pulpal healing

• to reduce bacterial load

• to create a suitable biological environment for restoration

what are the types of cavity medicaments used?

• liners

• bases

describe liners

• thin coatings (aqueous or volatile suspensions) applied to dentin to:

— Stimulate the pulp to protect itself. (e.g produce reparative dentin)

— form a barrier agent against irritants (thermal, chemical, bacterial)

— offer electrical insulation

examples:

• calcium hydroxide - stimulates reparative dentin, antibacterial and anti inflammatory

• Zinc oxide suspensions - soothing effect on pulp, bacteriostatic (stops bacteria multiplying), NOT used under resin

For composite restorations, a liner (often RMGI) may also:

• reduce gap formation at root margins

• minimise microleakage and recurrent caries (release fluoride)

• serve as a stress breaker

what are liners and what do they help with?

• thin coatings (aqueous or volatile suspensions) applied to dentin to:

— Stimulate the pulp to protect itself (e.g producing reparative dentin)

— form a barrier agent irritants (thermal, chemical, bacterial)

— offer electrical insulation

what may a liner also help with in composite restorations?

• reduce gap formation at root margins

• minimise microleakage and recurrent caries (release fluoride)

• serve as a stress breaker

give examples of liners and their purpose

• calcium hydroxide - stimulates reparative dentin, antibacterial and anti inflammatory

• Zinc oxide suspensions - soothing effect on pulp, bacteriostatic, NOT used under resin

describe bases

• thicker materials placed under permanent restorations to protect the pulp against:

— condensation forces

— thermal changes

— chemical irritation

• examples:

— zinc phosphate

— zinc oxide-eugenol (ZOE)

— calcium hydroxide (in thicker, settable form)

— polycarboxylate cement

— glass ionomer cement (GIC) and RMGI - most commonly used

Bases also help build bulk between pulp and final restoration (ideally -2mm of dentin + liner/base)

what are bases and what do they protect the pulp from?

• thicker materials placed under permanent restorations to protect the pulp against:

— condensation forces

— thermal changes

— chemical irritation

• Bases also help build bulk between pulp and final restoration (ideally -2mm of dentin + liner/base)

examples of bases

• examples:

— zinc phosphate

— zinc oxide-eugenol (ZOE)

— calcium hydroxide (in thicker, settable form)

— polycarboxylate cement

— glass ionomer cement (GIC) and RMGI - most commonly used

what does the cleaning and disinfection prior to medication consist of?

• gross debris is removed during cavity prep, but fine debris may remain.

• Irrigation and cleaning protocol:

1. warm water, 3% hydrogen peroxide, or 70% alcohol for short-term disinfection

2. gently dry with air (avoid desiccating the dentin - means: drying the dentin too much)

3. clean residual debris using explorer or cotton pellet

4. perform final visual inspection of cavity

what are the requirements of disinfectant agents?

1. must be effective

2. must maintain disinfection over time

3. must not harm the pulp

Warm sterile distilled water or saline (37 degrees Celsius) - especially useful in deep preparations