Fundamental Concepts of Tooth Adhesion

Adhesion

State in which two surfaces are HELD TOGETHER by INTERFACIAL FORCES.

Adhesion

May consist of VALENCE forces or INTERLOCKING forces or BOTH (Packman).

Mechanical - Adsorption - Diffusion - Combination of 3

4 adhesion mechanisms in dentistry.

Adhesive

Joins two substrates together and SOLIDIFIES and is able to TRANSFER a load from one surface to the other.

Mechanical Adhesion

Interlocking of adhesive with irregularities in the surface of substrate of adhered.

Adsorption

CHEMICAL bonding between the ADHESIVE AND ADHEREND.

Adsorption

Forces involved may be PRIMARY (ionic and covalent) or SECONDARY (hydrogen bonds, dipole interaction or van der Walls) valence forces.

Diffusion

The INTERLOCKING between MOBILE molecules.

Smear Layer - Dentinal Tubules

Acid etching removes the _____ _____ from the dentin surface as well as plugs of material forces into ________ _______ during cavity preparation.

Overetching

Results to formation of CRYSTALS (PRECIPITATES) that INHIBITS BONDING.

85%

BUONOCORE began with the use of this concentration.

(Phosphoric) Forms precipitates.

50%

(Phosphoric) RESULT: formation of MONOCALCIUM PHOSPHATE MONOHYDRATE precipitates that CAN BE RINSED.

Less than 27%

(Phosphoric) RESULT: Created a dicalcium phosphate monohydrate precipitates. CANNOT BE REMOVED EASILY which can interfere with adhesion.

30%-40%

(Phosphoric) Silverstone, et. al. observes a MORE RETENTIVE ENAMEL SURFACE.

Enamel Tufts

Defects caused by hypomineralization of enamel rods near DEJ.

Enamel Lamellae

Dentin cracks and defects present at the enamel.

Enamel Spindles

Dentinal tubules near DEJ created by odontoblasts crossing basement membrane.

Type I

(Etching Pattern) Prism core dissolution, honeycomb-like appearance.

Type II

(Etching Pattern) Dissolution of prism peripheries, cobblestone appearance.

Type III

(Etching Pattern) Mix of types I and II.

Type IV

(Etching Pattern) Pitted enamel surfaces as well as structures that look like unfinished puzzle.

Type V

(Etching Pattern) Flat, smooth surface.

Smear Layer

Decreases dentin permeability by 86%.

Smear Layer - Smear Plug

Removal of ______ _____ and _____ ______ with acid solution results in an increase of the fluid flow onto the exposed dentin surface.

DEJ - Pulp

Tubules occupy 1& of total surface near ___, and 22% near ____.

Sclerotic Dentin

Type of dentin that is resistant to acid etching.

Microleakage

Unrelieved stresses at the composite contribute to internal bond disruption and marginal gap around restoration increases ___________.

17 Mpa

To prevent debonding, __ ___ is necessary to resist the contraction stresses that develop on the composite during polymerization.

2%

Cure = _% polymerization.

Cyclic Loading

Tooth substrate itself might be weakened by?

Sevitron Cavity Seal

Combination of sulfinic acid and GPDM.

1st Gen

(Gen) Can chelate with calcium on tooth surface to generate a water resistant chemical bond of resin to dentinal calcium. 2-3 MPa. Cervident.

2nd Gen

(Gen) Phosphate-ester material. Smear layer was the weakest link in the system.

2nd Gen

(Gen) Polar interaction between negatively charged phosphate group in resin and positively charged calcium ions in smear layer.

3rd Gen

(Gen) In 1979, the concept of phosphoric acid etching of dentin before application of a phosphate ester-type bonding agent

3rd Gen

(Gen) Dentin etching didn’t improve its strength due to the hydrophobic nature of the bonding resin.

3rd Gen

Effectiveness of this system was questionable due to the manufacturer’s recommendation of placing composite over uncured resin.

4th Gen

(Gen) Thee step, total etch adhesives. Removal of smear layer using acid etch.

4th Gen

(Gen) Etching step not only alters the mineral content of dentin substrates, but also changes the surface free energy.

5th Gen

(Gen) One bottle, total etch adhesives. Combine the primer and bonding agent in a single solution.

6th Gen

(Gen) Self-etching primer system, non-rinsing conditioners.

6th Gen

(Gen) First toral etch adhesive system included acidic etchants with a conc. lower than tradition 30%-40% phosphoric acid.

Mild - Moderate - Aggressive

3 categories of SEP.

Mild

This SEP category tend to provide excellent dentin bond strengths and poorer enamel bonds, vice versa.

7th Gen

(Gen) All-in-one adhesive. Incorporate the classic steps of etching, priming, and bonding.

7th Gen

(Gen) Behave as semipermeable membranes, resulting in a hydrolytic degradation of the resin-dentin interface.

7th Gen

(Gen) Resin monomers might be too hydrophilic, making them liable to water degradation. May not coat dentin uniformly.