All studies assessed periodontal regeneration, root resorption and ankylosis by means of histological assessment [17,33,34] while in one study, immunohistochemistry was used to analyze osteoprotegerin (OPG), collagen III synthesis and laminin synthesis, and tartrate-resistant acid phosphatase (TRAP) was used to assess osteoclast activity [33]. The gene discussed is ACP5; the disease is ankylosis.