HELSINKI, Finland: The prevalence of adult periodontitis continues to pose a major global public health challenge, highlighting the need for evidence on the effectiveness of periodontal treatment. According to the Finnish Health 2011 survey, 74% of adults had gingivitis, 64% had periodontitis and 21% had severe disease. Since these figures showed no improvement compared with those recorded in 2000, researchers at the University of Helsinki undertook a follow-up study to better understand how periodontal health evolves after treatment.