**4. Classification peri-implantitis**

Currently, there is no standard classification system to classify the parameters and the severity of the peri-implant disease. Froum and Rosen [10] proposed a classification for peri-implant disease based on the disease severity. This classification includes three clinical stages:

**Early**: Pocket depth (PD) ≥ 4 mm (bleeding and/or suppuration on probing) Bone loss <25% of the implant length.

**Moderate**: PD ≥ 6 mm (bleeding and/or suppuration on probing) bone loss 25–50% of the implant length.

**Advanced**: PD ≥ 8 mm (bleeding and/or suppuration on probing) bone loss >50% of the implant length.

Bleeding on probing should be noted on two or more aspects of the implant, and bone loss is measured on the radiographs from the time of prosthetic loading to the current time. If the radiograph at prosthetic loading is not available, the earliest available radiograph following loading should be used [11].
