Clinical course of chronic periodontitis. III. Patterns, variations and risks of attachment loss

The purpose of this study was to assess the rate of attachment loss during various stages of adult life in a well-maintained middle-class population. The data originated from a 26-year longitudinal study of Norwegian males who had received regular and adequate dental care and practised daily oral home care. The initial examination in 1969 included 565 individuals aged between 16 and 34 years. Subsequent examinations took place in 1971, 1973, 1975, 1981, 1988 and 1995. Thus, the study covers the age range of 16-59 years. The rate of the annual attachment loss was calculated as the difference between the individual mean attachment loss between two examinations divided by the years between examinations. The mean annualized relative risk of attachment loss was calculated as the frequency distribution of sites with initial periodontal attachment loss (loss of attachment at the first time of occurrence > or = 2 mm) and healthy sites (loss of attachment always < 2 mm). For comparison of significant changes in annual attachment loss rates between the age groups and mean annualized relative risks of attachment loss as they proceeded through adult life, the Wilcoxon Mann-Whitney U-test was used. The mean overall individual attachment loss during 44 years (between 16 and 59 years) totaled 2.44 mm (range 0.14-2.44 mm), averaging an annual mean rate of 0.05 mm/year. The highest annual rate of attachment loss occurred before 35 years of age (0.08-0.1 mm/year), after which the mean annual rate decreased to about 0.04-0.06 mm/year for the next three decades of life leading to 60 years. The mean annualized relative risk of initial attachment loss increased significantly from adolescence (1.2%) to the maximum at 30-34 years of age (6.9%). After the age of 34 years, the risk of initial attachment loss decreased again, but after the age of 40 years, another continuous increase was observed. Over a 26-year period, 25% of the subjects went through adult life with healthy and stable periodontal conditions. The remaining 75% developed slight to moderately progressing periodontal disease with progression rates varying between 0.02 and 0.1 mm/year with a cumulative mean of loss of attachment of 2.44 mm as they approached 60 years of age. The annual mean rate and the mean annualized risk of initial attachment loss were highest between 16 and 34 years of age. Only 20% of the sites continued to lose further attachment during the remainder of the observation period, and less than 1% of