The result of a study of the effectiveness of treatment of chronic periodontal disease in a general dental practice using CPITN and the time required to treat patients with differing CPITN scores indicated that although there were significant reductions in calculus and shallow pockets, the treatment did not eliminate positive CPITN scores; 41% scored 1, 24% scored 2, and 34% scored 3 or 4 after treatment. Very few patients had 'healthy' periodontal sextants at the first visit; the most frequent CPITN category was 3. Patients in this category took up most of the treatment time. The treatment times per patient were much lower than the estimates of the World Health Organisation for similar treatments.