Ten-year changes of periodontitis grading using direct and indirect evidence: a retrospective evaluation.

Objective: To evaluate two methods for assessing the changes in periodontitis grading in patients undergoing supportive periodontal therapy (SPT) ten years (T10) after retrospective baseline (BL) grading.

Materials and methods: The periodontitis grade of 51 SPT-patients was assessed using indirect evidence as the primary criterion for periodontitis progression at BL and T10 (radiographic bone loss/age index, periodontitis phenotype). Grading at T10 was also performed using the direct evidence for periodontitis progression (clinical attachment loss over the previous five years). The use of indirect evidence for periodontal progression at BL and T10 was defined as method 1 (M1) to assess the changes in periodontitis grading. The use of indirect evidence at BL and direct evidence at T10 was defined as method 2 (M2). Changes in periodontitis grading using M1 and M2 were evaluated (Wilcoxon signed-rank test). Agreement between M1 and M2 was assessed (Cohen's kappa).

Results: Indirect BL-grading revealed five grade B and 46 grade C patients. The indirect grading at T10 revealed 17 grade B and 34 grade C patients. The direct T10-grading classified all patients as grade C. M1 led to an overall improvement in periodontitis grading after ten years of SPT (p=0.00297), whereas M2 led to a deterioration (p=0.0369). The comparison between M1 and M2 showed that they lead to different results in terms of grading (Cohen's Kappa=0.116208).

Conclusions: Periodontitis grading may change during SPT. Using indirect or direct evidence as the primary grading criterion during SPT may lead to different results.