Sites charted in BOTH exams whose attachment worsened by at least
PROGRESSION_MM — the clinically meaningful subset of changed.
Every site whose probing depth or attachment level moved at all, including
sites charted in only one of the two exams. Tooth order is the clinical
ALL_TEETH order; sites follow PERIO_SITES.
Sites charted in both whose POCKET deepened by at least PROGRESSION_MM.
Sites charted now but not then, and the other way round.
…and improved by at least as much.