The implant quality scale: a clinical assessment of the health--disease continuum.

Implant success is as difficult to describe as the success criteria required for a tooth. A range from health to disease exists in both conditions. The primary criteria for assessing implant quality are pain and mobility. The presence of either one greatly compromises the implant, and removal is usually indicated. Probing depths may be related to the presence of local disease or pre-existing tissue thickness before the implant was inserted. An increasing probing depth is more diagnostic and signifies bone loss, gingival hyperplasia or hypertrophy. Bone loss is usually evaluated best with probing rather than with radiographs. The most common cause of bone loss during the first few years of function are exaggerated factors of stress. The bleeding index is easily observed and indicates inflammation of the gingiva. However, implant health status is not as related to sulcular inflammation as would be the case for a natural tooth. Implant failure is easier to describe and may consist of a variety of factors. Any pain, vertical mobility, uncontrolled progressive bone loss, and/or generalized periradiolucency warrant implant removal. Implant quality factors were established by James and modified by Misch into an implant quality scale which not only assesses the implant health-disease continuum, but relates treatment and prognosis to the existing conditions.