Stage 3 periodontal disease is defined by which combination of furcation involvement and attachment loss?

• A. Stage 3 with stage 2 furcation and 25-50% attachment loss
• B. Stage 2 with stage 1 furcation and less than 25% attachment loss
• C. Stage 4 with furcation stage 3 and more than 50% attachment loss
• D. Stage 1 with gingivitis only

Answer: (A)

Stage 3 periodontal disease reflects moderate destruction of the tooth-supporting structures, shown by 25–50% attachment loss and a notable furcation involvement. For multi-rooted teeth, furcation involvement graded as stage II means horizontal bone loss into the furcation area that the probe can enter, but it does not pass completely through to the opposite side. So having 25–50% attachment loss together with stage II furcation fits the moderate, mid-range severity characterized as stage 3. The other scenarios describe either milder disease (less than 25% attachment loss with minimal furcation involvement), more advanced disease (more than 50% attachment loss with a through-and-through furcation), or gingivitis-only, which is not periodontitis.