Clinically Commonly Used Dental Cements and Their Main Uses

(I) Zinc Phosphate Cement
Function: Thermal insulation (thickness >1mm), insulation against electrical stimuli to the pulp.
Applications:

1. Temporary restoration of tooth defects

2. Intermediate filling restoration of tooth defects

3. Bonding inlays, crowns, bridges, and orthodontic attachments

4. Indirect base for deep caries

5. Direct liner/base for moderate caries

Freshly mixed zinc phosphate cement is acidic (pH 1–2). pH rises to 4.2 after 3 minutes, to 6 after 1 hour, and approaches neutral after 48 hours. Not suitable for direct basing in deep caries due to significant irritation to dentin and pulp; only used as an indirect base to provide thermal and chemical insulation.

(II) Zinc Oxide-Eugenol Cement
(Detailed in a prior section)
Applications:

1. Lining and basing for deep cavities near the pulp (Note: Requires a layer of zinc phosphate cement over it)

2. Temporary cavity sealing

3. Root canal filling

4. Periodontal surgical dressing
   Luting-type zinc oxide-eugenol cement is used for cementing fixed prostheses.

(III) Calcium Hydroxide Cement
Applications:

1. Indirect pulp capping

2. Direct pulp capping

3. Base for root canal fillings
   Note: Softened dentin need not be fully removed during indirect pulp capping due to its antibacterial/antimicrobial effects.

(IV) Zinc Polycarboxylate Cement
Composition: Zinc oxide (powder) + Polyacrylic acid solution
Characteristics:

1. Excellent adhesion: Bonds well to tooth structure and metal restorations.

   • Tooth bonding: Mechanical interlocking + ionic bonding with surface Ca²⁺ + hydrogen bonding between -COOH and dentinal -OH.

   • Adhesion strength: Enamel 3–10 MPa, Dentin 2–6 MPa.

   • Chemical interaction with metal surfaces.

2. Low pulp irritation

3. Low water solubility

4. Insulates against thermal/electrical pulp stimuli
   Applications:

5. Luting cement for prostheses

6. Direct liner/base for deep caries and amalgam restorations (single layer suffices)

7. Not suitable for load-bearing areas due to susceptibility to deformation

8. Filling deciduous tooth caries (low solubility + low pulp irritation)

9. Base for resin fillings

(V) Glass Ionomer Cement (GIC)
Characteristics:

1. Fluoride release (caries prevention)

2. Slight water absorption
   Bonding Mechanism:
   (1) Carboxyl groups form chemical bonds with tooth Ca²⁺;
   (2) Hydrogen bonding between carboxyl groups and dentinal collagen;
   (3) Micromechanical interlocking.
   Note: Ion exchange occurs between GIC carboxylate ions and tooth phosphate ions. Enamel contains more phosphate groups than dentin, resulting in stronger GIC adhesion to enamel.
   Applications:

3. Filling tooth defects; cementing fixed/orthodontic appliances

4. Cavity liner/base

5. Partial pit and fissure sealing
   Note: Specific applications depend on GIC subtype properties.
   Traditional GIC: Lower strength → used for deciduous teeth, Class III/V cavities, and wedge-shaped defects in permanent teeth.

GIC vs. Composite Resin:

• GIC has lower bond strength to tooth structure than composite resin but exhibits similar microleakage.

• GIC’s significantly lower setting shrinkage compensates for its lower bond strength.
  GIC Disadvantages: Inferior aesthetics, lack of translucency, difficult polishing.

Summary of Key Properties:
Pulp Irritation (Low → High):
Zinc oxide-eugenol < Zinc polycarboxylate < Glass ionomer < Zinc phosphate

Adhesion Strength (High → Low):
Glass ionomer > Zinc phosphate / Zinc polycarboxylate
(Clinically, zinc polycarboxylate is often preferred for prosthesis cementation)

Temporary Sealing Material Requirement: Low solubility.