Observations on the recurrence of destructive periodontal disease during a period of four years after treatment.

The upper and lower extreme percentiles of change in clinical variables were analyzed for a period of four years after completion of periodontal therapy in order to assess the patterns of disease recurrence after treatment. This analysis has demonstrated periods of healing and relapse of sites within individuals, among different individuals, and among different clinical assessment variables utilized. As not all of the sites within different individuals heal or relapse at the same rate, the random asynchronous burst model of pathogenesis seems appropriate to incorporate the different clinical assessment parameters and different sites in different individuals simultaneously. Long-term recession and pocketing, however, may demonstrate opposite trends, giving the erroneous interpretation that attachment levels remain constant with time, whereas, in fact, an active "dynamic equilibrium" of tissue remodeling is established. A statistical model based on the dynamic equilibrium concept would enable account to be taken of the multifactorial interactions that incorporate site and subject interrelationships between different clinical assessment parameters. The dynamic equilibrium model may be suitable therefore as the basis on which statistical analysis of the progression of periodontal disease may be considered. However, as the value of this or other models of the periodontal disease process have not been established, the analysis of data to derive meaningful conclusions from complex statistical techniques may be premature.