PRL and periodontitis: On unadjusted analysis, individuals with very severe periodontitis had thinner PRL (severe periodontitis: 164.3 ± 9.0 μm vs. unaffected: 165.2 ± 8.8 μm, P < 0.001) but did not differ significantly in RPE–BM thickness (severe periodontitis: 23.0 ± 2.1 μm vs. unaffected: 22.9 ± 2.5 μm, P = 0.40, Table 1).