Table 1 Summary of histological classification by Petty et al.[24]

0

Often absent; if present, laminated and limited to 1 to 2 thin layers; eccentric and often related to off-center drill defect

Haversian canals small and repair rate slow; polymorphonuclear leukocytes not in granulation tissue; occasional subperiosteal resorptive pockets, but no polymorphonuclear leukocytes

Quick repair with woven bone; inflammatory cells range from none to foci of many intact polymorphonuclear leukocytes; these leukocytes associated with macrophage clean-up; diffuse process

1

Usually laminated with 1 to 2 layers; often eccentric but not related to off-center drill defect

Occasional polymorphonuclear leukocytes in Haversian canals

Subtle, diffuse increase in polymorphonuclear leukocytes; microabscesses present, but hard to find

2

Sunburst type; often nearly circumferential; no apparent cause

Focally enlarged Haversian canals filled with granulation tissue and fragmented polymorphonuclear leukocytes; occasional microabscess

Definite diffuse increase in polymorphonuclear leukocytes with fragmented forms; several definite microabscesses

3

Florid, always sunburst type; circumferential

Subperiosteal, endosteal, and intracortical resorption associated with fragmented polymorphonuclear leukocytes; microabscesses

Many microabscesses or great increase in polymorphonuclear leukocytes diffusely

4

As above, but with sinus-tract formation and soft-tissue microabscesses