PULP PROTECTION [RDT |Cavity Sealers|Liners|Bases]

REMAINING DENTIN THICKNESS-

Thickness of healthy dentin between floor of tooth preparation and pulp chamber.

RDT	Effect of toxic substances on pulp
0.5 mm	25 %
1 mm	10 %
2mm	Minimal of nil

RDT

CAVITY SEALERS

Materials that provide a protective coating to the walls of the prepared cavity and a barrier to leakage at the interface of the restorative material and the walls. 

a] Varnish

A natural rosin or gum (such as copal), or a synthetic resin, dissolved in an organic solvent such as acetone, chloroform, or ether that evaporates leaving a thin film

Varnish is applied to all the walls of cavity preparation

Properties- 

• Film thickness - 2 to 5 μm.

• Low solubility 

• Physical Barrier  against - bacteria & products, irritants , oral fluid

• NO mechanical strength , NO thermal insulation

Applications-

1. Amalgam- 

1.   microleakage —     postoperative sensitivity.

2.   tooth discoloration — from corrosion products

2. Passage of irritants into DT from restoration or base, e.g. silicate.

3. Surface coating over restorations -

a] prevent dehydration/contact with oral fluids, e.g. silicate and GIC.

b] metallic restoration  - temporary protection from galvanic shock.

4. Fluoride containing varnishes  

Contraindications-

• Composite resins - Varnish may react with the resin.

• GIC - chemical bond with tooth.

• ZOE and CaOH - therapeutic action 

b] Adhesive Sealers

• Provide sealing as well as bonding at the interface between restoration and cavity-preparation walls.

• Have more/less replaced varnishes.

CAVITY LINERS

Cement or resin coating of minimal thickness (usually less than 0.5mm) to -

• physical barrier to bacteria and their products 

• therapeutic effect - Antibacterial, pulpal anodyne effect, fluoride release, dentinal seal 

• NO mechanical strength 

• NO significant thermal insulation. 

Liners are applied only to Dentin cavity walls that are near the pulp

a] Calcium Hydroxide

Main Composition-	Ca(OH)₂ in various vehicles
Advantages-	protective barrier - blocks DT high pH[12.5-13] - stimulate Reparative dentin OH ions — antibacterial
Limitations-	Dentin Bridge with tunnel defects Initial Necrosis then healing Poor sealing, poor mechanical properties
	Availability- Paste [base + catalyst] Or light cured

b]Glass Ionomer Cement:

Main Composition-	Fluoroaluminosilicate glass + polyacrylic acid
Advantages-	Chemical bond  Fluoride release Excellent mechanical properties  [MOE similar to Dentin] [COE similar to Dentin] [MAN-MADE DENTIN]
Limitations-	Limited bioactivity - no hard tissue formation Moisture sensitivity
	Prefer RMGIC/light cured GIC -Not sensitive to water, Easy handling.

b]Calcium Silicate based Liners:

	MTA [Mineral Trioxide]	Biodentine
Main Composition-	75% Portland cement, 20% Bi₂O₃, 5% CaSO₄	Tricalcium silicate, CaCO₃, ZrO₂
Advantages-	Organised Dentin Bridge Good mechanical properties Good sealing ability	Organised Dentin bridge Good mechanical properties Good sealing ability Fast setting [12 min] Excellent handling
Limitations-	Long setting time [2.5-3hrs] Poor handling  High cost Potential discoloration	High cost

CAVITY BASES

Materials to replace missing dentin, used for bulk buildup and/or for blocking out undercuts in preparations for indirect restorations.

Base is applied only on pulpal & axial walls near pulp

Base is applied only on plural and axial walls

a,b] Zinc Phosphate and Zinc Polycarboxylate cements 

	Zn Phosphate	Zn Polycarboxylate
Main Composition-	ZnO + orthophosphoric acid	ZnO + polyacrylic acid
Pulp protection-	Highly acidic [1.5 - 2 pH] -  pH increases in 24 hrs [always place liner beneath]	Acidic [but pH inc. with time] BUT larger molecular weight [so, less penetration in DT]
Advantages-	Excellent thermal insulation High compressive Strength	Chemical bond to tooth [1st adhesive cement]
Limitations-	No adhesion Initial highly acidic Potential microleakage Brittle	Inadequate thermal protection Lower mechanical properties than ZP

c] Glass Ionomer Cement:

Main Composition-	Fluoroaluminosilicate glass + polyacrylic acid
Advantages-	chemical bond  Fluoride release Excellent mechanical properties [Excellent compressive strength] [MOE similar to Dentin] [COE similar to Dentin] [MAN-MADE DENTIN] Thermal insulation
Limitations-	Limited bioactivity - no hard tissue formation Moisture sensitivity
	Prefer RMGIC/light cured GIC -Not sensitive to water, Easy handling.

Guidelines

Restoration	Shallow cavity  [RDT >2 mm]	Moderately deep cavities   [0.5mm to 2mm]	Deep cavity  [0.5mm]
Amalgam	Varnish / DBA	Varnish + Base	Varnish + Liner + Base
Composite resin	DBA	DBA ± Base	Liner + DBA + Base
Cast Restorations	Luting cement	Base + Luting cement	Liner + Base + Luting cement

Effective pulp protection requires understanding the properties and appropriate applications of various protective materials. The integration of cavity varnishes, liners, bases, and modern dentin bonding agents, when used judiciously based on cavity depth and clinical conditions, ensures optimal pulp health while achieving durable, well-bonded restorations. Success depends on proper material selection, technique execution, and long-term monitoring of pulp vitality.