P. Pallav, PhD

The word abrasion is often used as a synonym of wear. In engineering science, abrasive wear is defined as a cutting material removal like machining, filing, grinding. This is a major component of the wear at occlusal contacts, but it also occurs at contacts with anchor elements of partial dentures, etc. 

Abrasion is caused by sharp roughness asperities of the antagonist, which should at least be some 50 % harder than the wearing substrate. 

When the contact moves, the roughness protrusion at A in the figure will plough through the protrusion at B. Damage to the surface in this case depends among others on the ratio of the radius of the sphere (R) and the depth of indentation (d).
In the engineering field experiments have been carried out in which hardened spheres with various radii (R, in the order of millimeters) were slid over surfaces of various materials, while the depth of indentation (d/R) was maintained at a constant value.

d/R < 10-4	10-4 < d/R < 0.3	d/R > 0.3
If the penetration depth ( d/R) is very small (left) no damage is caused when the sphere moves over the surface. Up to d/R ≈ 0.3 a furrow is created. Above this value more substrate material packs up in front of the sphere than can escape at the sides and the sphere in fact cuts a chip from the surface.

Wear at the abrasively wearing surface is inversely proportional to its hardness (BHN, VHN) in fully work hardened condition, because an abrasive particle always pushes a fully work-hardened zone ahead of it.
The Wear Control Handbook (ASME - Peterson and Winer, 1980) also reports of a fairly successful attempt to describe abrasion statistically in terms of roughness height and wave length, the associated penetration depth distribution, and the chances of a wear particle to be created at a micro contact.
If the wear particles accumulate between the surfaces, the wear rate may decrease as these particles take over an increasing part of the normal force (a difference between single- and multi-pass sliding wear).
Abrasive wear may cause substantial changes in surface texture (roughness, smear layer etc.), which can influence the wear rate, usually yielding a distinction between initial and steady state wear rate.
In dental literature sometimes the word attrition (wear) is used for this type of wear.