What a dental cleaning removes, what it measures, and what it cannot do
Patients used to leave my chair and say "my teeth feel so clean," and I would smile and not say what I was thinking, which was: for about six hours. A cleaning is a useful, necessary thing. It is also widely misunderstood, and the misunderstanding leads people to think the twice-a-year visit is what keeps their mouth healthy. It is not. It is the inspection and the reset. The other 363 days are what keep your mouth healthy. Let me walk through what actually happens in that chair.
Plaque and tartar are not the same thing
Plaque is soft. It is a film of bacteria, their byproducts and bits of food that forms on every tooth surface within hours of brushing. You can remove it yourself with a brush and floss, and you need to, every day, because if you leave it alone for a day or two it starts to absorb minerals from your saliva and harden.
Once it hardens, it is tartar, or calculus, which is what we call it in the office. Calculus is rough, porous, and stuck to the tooth. You cannot brush it off. It also gives new plaque a perfect rough surface to grab onto, so a tooth with calculus on it builds plaque faster than a clean one. The MouthHealthy page on plaque and tartar from the ADA explains the cycle in plain terms.
Removing calculus is the main physical job of a cleaning. It is the thing you cannot do at home.
The instruments, and what each one is doing
The ultrasonic scaler, which most people know as the thing that whines and sprays water, vibrates a metal tip thousands of times per second. The vibration shatters calculus off the tooth and the water washes it away and keeps the tip cool. It is fast and it is good at the big deposits, especially along the lower front teeth where the saliva glands empty and calculus builds fastest.
The hand scalers and curettes are the small hooked instruments. After the ultrasonic, I would go around every tooth by hand, feeling for roughness with the tip. Calculus under the gumline is often invisible, so this part is done by feel. A good hygienist has fingertips that can detect a deposit smaller than a grain of sand. This is also where the appointment either goes quickly or does not: a mouth with a little calculus takes fifteen minutes of hand scaling; a mouth with a lot takes forty-five and we may need two visits.
The polisher, the rubber cup with the gritty paste, comes after. I will be honest about polishing: it is mostly cosmetic. It removes surface stain and leaves the teeth smooth, which feels wonderful and makes it slightly harder for plaque to stick for a day or two. It does not remove calculus. Some practices have started skipping it when there is no stain, and that is defensible.
Fluoride varnish at the end, for patients who need it, is a sticky coating painted on that releases fluoride into the enamel for several hours. The ADA's summary on topical fluoride is the professional reference. For adults with dry mouth, exposed roots or a history of decay, I thought it was the most useful two minutes of the visit.
The numbers we call out
If you have heard your hygienist reading numbers to an assistant, "three, two, three, four, three, three," that is periodontal charting. We slide a thin probe with millimeter markings into the groove between the tooth and gum at six points around each tooth and read how deep it goes.
One to three millimeters is healthy. The gum is tight against the tooth. Four is a warning: the tissue has started to pull away and a pocket is forming where plaque can hide and you cannot reach. Five and above means bone has been lost and the pocket is deep enough that a regular cleaning will not get to the bottom of it. That is when the conversation shifts to scaling and root planing, the "deep cleaning," usually done with numbing, one quarter of the mouth at a time.
We also note bleeding on probing, which is the single most useful sign of active inflammation, and recession, where the gum has moved down the root. Comparing this chart to the last one is the real purpose of the visit. The scraping is the maintenance. The chart is the diagnosis.
What a cleaning cannot do
It cannot stop plaque from coming back. Within four to twelve hours of leaving the office, a new film is forming. That is biology, not a failure of the cleaning.
It cannot change which bacteria live in your mouth. Everyone's mouth has hundreds of species, and the balance between the ones that cause trouble and the ones that do not is set by what you eat, how dry your mouth is, how often you clean, and some luck. A cleaning removes the mass of bacteria but the population that regrows is the same population. The Harvard Nutrition Source page on the microbiome is about the gut, but the principle that the resident community rebuilds itself applies in the mouth as well.
It cannot fix a dry mouth, undo a sugary diet, or make up for the days you did not floss. Those are the 180-day problems, and they are yours.
The 180 days
Twice a year is a convention, by the way, not a finding. It came from mid-century toothpaste advertising and stuck because it is easy to schedule. Some people with healthy gums could come once a year. Some with periodontal disease need to come every three months. Your chart, not the calendar, should decide.
Between visits, the things that moved the chart in the right direction, in my experience, in order of how much they mattered: flossing every day, brushing properly twice a day with a fluoride paste, keeping the mouth moist, cutting the number of times per day you eat or sip something sweet, and cleaning the tongue. Nothing else came close to those five.
Patients asked about add-ons constantly. Water flossers: genuinely helpful for people with braces, bridges or dexterity problems, and a fine addition for anyone. Electric brushes: yes, if you have a heavy hand or a short attention span; the two-minute timer alone is worth it. Alcohol mouthwash: no, it dries the mouth. Oral probiotics: a qualified maybe, which I take up in the next article.
The short version on probiotics, since it belongs here too: the idea is to tip that resident population toward the species that do not cause odor and inflammation, using live bacteria that you let dissolve in the mouth. The trials on specific strains, especially Lactobacillus reuteri, show small improvements in gum bleeding and plaque in people who are also brushing and flossing. ProDentim's chewable tablet is the one patients ask about most, and it contains reuteri along with two other strains. I would not expect it to replace a single one of the five habits above. As a sixth, for someone who has the five in place and still has stubborn bleeding or breath, I thought it was worth a try.
How to get more out of your next visit
Ask for your numbers. Ask whether any of them changed since last time. Ask which areas had the most calculus, because those are the spots you are missing at home, and ask the hygienist to show you how to reach them. Ask whether you need fluoride varnish and why.
And do not apologize for your mouth. We have seen worse, every day, for decades. The patients I worried about were not the ones with calculus. They were the ones who cancelled.
If you want a plain description of what the office is checking for, MedlinePlus has a dental health overview that covers the basics without selling anything. And if you decide to try a probiotic alongside the habits, prodentim-buy.net has the ingredient list and the strain names so you can compare them against the trials before you spend anything.