Imagine a visit to a paediatrician. They weigh the baby, measure the baby, and plot one dot on a chart. A baby steady on the 30th percentile is well. A baby who slides from the 80th to the 30th since the previous visit needs looking at immediately. The dot tells you almost nothing. The line tells you everything. Dentistry has the same charts. We just don't always draw the line.
N=1
We typically don't make irreversible life decisions on a sample of one. You wouldn't sell your house on the first number a stranger shouted over the fence. You wouldn't amputate a leg because it ached on a Tuesday. We wait. We watch. We gather second, third and fourth data points, and crucially see where it's trending, before we do something we can't undo. We usually do this intuitively, subconsciously, and heuristically.
Bone loss, tooth wear, recession, erosion, caries, even oral cancer is a process. Sometimes it moves. Sometimes it stays still. A lesion is not a thing, it's a stage in a story, and the only honest question is which way the story is heading. And understanding how quickly a condition is changing is often more informative than simply determining whether change has occurred.
Signal or noise?
There is another reason why single observations can be misleading. Clinical measurements are never perfect. A radiograph may look different because of angulation. A periodontal measurement may vary between examinations. A lesion may appear larger or smaller because of lighting, photography, or examiner variability. The clinician is rarely observing disease directly; they are observing a measurement of disease. Longitudinal monitoring helps separate true biological change from measurement noise, allowing the signal to emerge from the background variability.
Iatrogenesis from residual risk
Every irreversible intervention starts a second act you can’t control. Not every lesion becomes disease. Not every disease becomes clinically significant.
No one ever looked at a hurricane and blamed a butterfly. The chain is too long, the steps too many, the cause too far back to see. By the time a tooth needs an extraction at fifty, nobody remembers the fissure sealant at twenty one. We feel the hurricane. All we can do is minimise the wing beats where appropriate.
No intervention?
This is not an argument for doing nothing.
Watching can be its own harm. Some conditions are not butterflies. They are gathering storms, and the data says so. This is where experience, judgement and sound decision making make human practitioners indispensable.
So do something when the benefit outweighs the long term, residual risk. The point is not less treatment. The point is treating the condition that is actually moving, and trending towards a disastrous outcome. Leave alone the conditions that are not moving, or likely to move.
Trust and persuasion
Showing that a condition is stable, and that you'll continue to monitor it, is one of the ways you build the most profound trust. Showing the condition is moving towards a very bad outcome, and being there with the options and solutions, is one of the easiest ways to earn case acceptance. The data does the work. You just point and be available for questions.
The data moat
Your past data can be one of the strongest reasons a patient comes back to you.‘Come back in six months and we'll see whether the wear is getting worse’. That sentence if repeated will improve your rebooking and recall attendance many fold. Remember though that this is conditional on regular gathering of photos, scans, and when indicated radiographs.
I’m a firm believer that If you treat your data as one of your most valuable assets, it will respond by becoming one of your most valuable assets.
Ergodic nature
Nassim Taleb, from whom I've borrowed from many times in this essay, calls ergodicity the most powerful concept he knows. There's a point where a condition no longer regresses ale stabilises, rather it pulls with increasing power towards a bad outcome. Get close enough and there is no path back. Taleb calls this an absorbing barrier. A condition near that edge travels one way quickly, toward full mouth rehab, clearance or in the case of oral medicine much worse outcomes. So past a certain point watching is not evidence based, it's the road to an absorbing barrier and great harm. Doing nothing becomes a severely iatrogenic act.
In summary
Great patient and commercial outcomes are built on judicious evidence and data analysis and should never be built on compromised ethics.
Longitudinal monitoring, with judicious data backed - watch and wait strategies and judicious data backed intervention, is the best way I know to achieve excellent patient outcomes.