TABLE I.

Elastic and Geometrical Properties of Dentin/Adhesive Interface Components

Interface Component	Elastic Modulus (GPa)	Thickness (μm)
Composite	~30
Adhesive	~5	2–5
Peritubular dentina	26–30	0.6–1
Intertubular dentinb	13–20	2–5
Graded hybrid layer/exposed collagenc	5–1	2–10

^aBased upon measurements by Kinney et al.¹⁸

^bBased upon measurements by Kinney et al.¹⁸ and Katz et al.¹³ The intertubular dentin modulus was measured to be 20 GPa by Kinney et al.¹⁸ Subsequently, Katz et al.¹³ found that the intertubular dentin close to the interface has a lower modulus of 13 GPa due to partial demineralization during etching. Therefore in the vicinity of the interface, the intertubular dentin is considered to have a modulus gradient from 13 GPa ramping up to 20 GPa.

^cBased upon measurements by Katz et al.¹³