Aim: The aim of the study was to evaluate disease progression during supportive periodontal therapy in (i) a group of 225 subjects with "normal" (NG) and (ii) a group with high susceptibility (HSG; n= 109) to periodontal disease (based on their baseline disease status).
Material and methods: The following variables were recorded at the baseline examination (1 year after they received non-surgical periodontal therapy) and at the re-examination after 12 years of maintenance: number of teeth, plaque, probing pocket depth, probing attachment level, bone level in full mouth radiographs. All assessments were performed in a standardized manner and by well-trained and calibrated examiners. Supportive periodontal therapy was delivered 3-4 x per year and included repeated oral hygiene instruction and debridement. In addition, sites that bled on probing and had a PPD value of > or = 5 mm received subgingival instrumentation.
Results: A comparison between the findings at baseline and after 12 years revealed that in the NG, most subjects maintained their periodontal condition unchanged during the maintenance period; only a few subjects experienced tooth loss and the figures describing the mean amount of bone and attachment loss were small (0.5 mm and 0.3 mm respectively). The HSG patients experienced some tooth loss and also lost significant amounts of bone and attachment during the 12 years of SPT. Thus, in this group of subjects, the mean overall PAL loss amounted to 0.8 mm, i.e., 0.06 mm/tooth surface/year. In the NG, the overall attachment loss was significantly smaller: 0.5 mm, i.e. 0.04 mm/tooth surface/year.
Conclusion: In subjects with a high susceptibility for periodontal disease who had been treated for this condition by non-surgical means, an SPT program including regularly repeated oral hygiene instruction and subgingival debridement, made it possible to maintain bone and attachment levels at a reasonably stable level over a 12-year period. A similar SPT provided to a group of subjects with normal susceptibility to periodontal disease, on the other hand, prevented almost entirely major tooth, bone and attachment loss.