Root surface biomodification has been used to treat periodontitis and gingival recession. The rationale for this procedure is that removing the smear layer from the root surfaces exposes collagen fibers, which leads to improved healing. Although animal studies have shown promising results, human studies have been disappointing. Some experts claim that the use of low-pH biomodification agents may cause necrotizing effects, and the use of neutral-pH agents does not. However, clinical investigations generally have failed to find any improvement in clinical parameters when using such agents.