"They Found Five Cavities — Do They All Need Filling? A Changdong Station Dentist's A-to-Z on Cavities to Watch vs. Cavities to Treat"

Hello. I am Dr. Oh Ji-hwan of Yonsei The Strong Dental Clinic.

Let me begin with the conclusion. Not every cavity is the same cavity. Early decay that stays within the outer shell (enamel) can be stopped and monitored; decay that has reached the dentin beneath it only grows the longer you wait. What matters isn't the number "five" — it's how deep each one is.

This is the season when people arrive holding a school screening slip. A mother from Ssangmun-dong startled by "caries: 5" on her child's form, and a commuter riding up one stop from Changdong Station, asked the same thing: "Do these all need filling? One place said three, another said five." The reason counts differ between clinics is usually not skill — it's whether early lesions are counted at all.

Today I'll walk through that standard from the beginning: how decay progresses, where the line falls between monitoring and treating, what a clinic uses to draw that line, what to do at home if you're monitoring, and how treatment methods and insurance work if you treat. By the end you'll be asking not "how many" but "what stage."

How decay grows — depth is everything

Decay is acid made by bacteria dissolving minerals from the tooth surface. While it stays in the outer shell it can still be reversed; once it breaks through, there's no going back.

The enamel is the hardest tissue in the body. When bacteria feed on sugar and produce acid, minerals leach out of that surface little by little — a stage called demineralization. It shows as a chalky white spot or a brown line, and it isn't yet a hole. What matters is that at this stage, saliva and fluoride can put minerals back. That's called remineralization.

The problem is that with a steady supply of acid, demineralization outpaces remineralization. The moment enamel is breached and decay reaches the dentin below, everything changes. Dentin is far softer, threaded with tiny tubules running toward the nerve, so once in, decay spreads wide and fast. That's why the inside is often much larger than the hole you see.

What differs by stage

As the table shows, the option to monitor exists only in the top two rows. From the third row on, waiting is a loss. So if you've been told "five cavities," the real question is how many are in those top rows and how many are below.

Signs that need checking now

• A specific tooth twinges briefly with sweets
• Floss keeps shredding or catching at the same spot
• The grooves of a molar's chewing surface have gone dark brown
• The edge of an old filling has turned black
• Cold water stings, then settles quickly
• Food packs into the same spot repeatedly

Any one of these suggests the tooth may be at row three or below. Conversely, decay found only at a screening with no symptoms is more likely in the top two rows — though early dentin decay can also be symptom-free, so symptoms alone can't set the stage.

Even at the same depth, location matters

After depth, the next factor is location. Decay occurs in three main places, each with a different margin for monitoring.

Be especially careful with gum-line decay. Enamel there is thin or absent, so what looks early is often already into dentin. It favours people with receded gums and exposed roots, and people with dry mouths, and it moves fast. By contrast, early decay in a chewing-surface groove is one of the easier sites to halt — a sealant closes it off from bacteria.

Decay between teeth is the hardest to judge. Detection itself depends on X-rays, and whether it's enamel or dentin is read from the depth of the shadow on the film. So if you've been told "several between the teeth," you're entitled to ask to see those images. A shadow confined to enamel can be monitored with floss and fluoride; one crossing into dentin is treatment.

Now that depth is everything, let's look at what a clinic uses to confirm it.

How a clinic draws the line — not by eye alone

The stage of a cavity is judged by combining three things: looking, probing, and X-raying the inside.

1. Looking. We examine color and texture with the tooth dried. A white spot invisible when wet appears once dry — the hallmark of early demineralization.
2. Probing. A fine-tipped explorer checks whether the surface is hard or soft. Pressing hard on an early lesion can actually break the surface, so today it's used only gently.
3. X-rays. Decay between teeth is nearly invisible from the outside. Bitewing films taken from the side show the contact surfaces and depth — and whether these were taken is the biggest reason counts differ between clinics.
4. Transillumination, when needed. Strong light passed through the tooth casts shadows where decay sits, a useful adjunct for early lesions between teeth.
5. Activity. Two early lesions at the same depth differ if one is rough and chalky (progressing) and the other smooth and brown (arrested). Arrested decay is left alone as a rule.

One point worth making here. Neither the clinic that counts early lesions nor the one that doesn't is wrong. But from your side, asking "of those, how many need treatment now?" makes the answer far sharper.

Questions that come up in the chair

Q. Does monitoring an early cavity just mean leaving it? A. No. It means monitoring with care — fluoride, adjusting diet, correcting brushing, then re-checking in 3–6 months, and treating then if it has progressed. That's different from doing nothing.

Q. If it'll need filling eventually, isn't now better? A. Filling means removing tooth structure. Monitored at an early stage and arrested, a tooth may never be drilled at all; and if it does progress, the amount removed then is often little different from now. Dentin decay, by contrast, clearly needs more removal the longer it waits. So the answer differs by stage.

Q. Is it the same standard for a child's baby teeth? A. The principle is the same, but baby-tooth enamel is thin, decay moves faster, and the permanent tooth developing underneath can be affected, so observation intervals are shorter. A baby tooth close to falling out may simply be watched rather than treated. Age and tooth type are read together.

Q. Another clinic said three; here it's five? A. Usually the difference is whether early lesions were counted or X-rays taken. Rather than the number, look at each tooth's stage on the images together — the two clinics are often saying the same thing.

Q. Do early cavities arrest in adults, or only in children? A. Adults too. Remineralization happens at any age given saliva and fluoride. Adults are simply more likely to take mouth-drying medications or have entrenched snacking habits, which makes changing conditions harder — not impossible.

Q. Will the white spot go away? A. The white mark itself often remains after arrest. But if the surface becomes smooth and stops growing, that is success. If it's a front tooth and bothers you, surface treatments can be discussed separately — but that's an esthetic matter, not a decay matter.

Q. If it progresses while monitoring, won't treatment be bigger by then? A. Not if the re-check interval is kept. Enamel decay rarely reaches the nerve within 3–6 months; it's usually caught as a "small filling." The cases that grow are the ones where re-checks were skipped for a year or two. That's why the date matters.

With the method understood, here's what to do at home if you're monitoring.

If you're monitoring — the conditions that arrest it

The power to arrest early decay comes not from the clinic but from the daily environment of your mouth. Fluoride, how often sugar hits the teeth, and whether the brush actually reaches — those three are the core.

First, fluoride. Fluoride helps lost minerals return and makes the newly formed surface more acid-resistant. Use a toothpaste with adequate fluoride, and the trick is not rinsing repeatedly with water afterward — every rinse washes fluoride away. High-concentration varnish applied at the clinic adds to this.

Second, the frequency of sugar exposure. Frequency over quantity. The same amount of sweets eaten at once versus nibbled all day is completely different for teeth: each acid event dissolves the surface, and saliva needs time to reverse it. Simply fixing snack times has a large effect.

Third, does the brush actually reach? Early decay forms where the brush doesn't reach — inner molar surfaces, between teeth, the gum line. Having someone check at the mirror how you'll clean that spot is worth more than a hundred words. Decay between teeth makes floss essential.

Care checklist

• Fluoride toothpaste twice daily; rinse only once, lightly
• Sweets and fizzy drinks at set times, followed by a sip of water
• Nothing but water after the bedtime brush
• Know where the decay was and brush that spot deliberately
• Floss daily if the decay is between teeth
• Sugar-free gum boosts saliva and helps (a supplement, not a substitute)
• Book the 3–6 month re-check before leaving
• Photograph the site and compare from the same angle at the re-check (change becomes visible)

If your mouth is dry, one more thing applies. Saliva is the biggest force washing acid away and returning minerals; when blood-pressure medication, antidepressants or antihistamines reduce it, the same habits let decay progress faster. If you take such medication, drink water often and ask about sugar-free gum or saliva-stimulating products — and a shorter three-month observation interval is safer.

At the re-check, a smooth surface hardened to brown means it has arrested. Rough or larger means moving to treatment. Skip this re-check and "monitoring" becomes "neglect." I've discussed what happens when decay is left untreated in an interview with Ziksir; the difference between monitoring and neglect is exactly one thing — whether a date was set.

If you're treating — methods, cost and insurance

Decay that has reached the dentin is removed and the space filled, with the method depending on size and location, and coverage varying accordingly.

Cost depends on method, material and size. Broadly, fillings in covered materials run about ₩10,000–30,000 out of pocket, adult resin fillings about ₩50,000–150,000, and inlays about ₩150,000–400,000 depending on material. Standards vary by clinic and site, so treat these as reference ranges and confirm after examination.

What I want to stress is that five cavities don't all get the same treatment. Two may be monitored, two filled small in covered materials, one may need an inlay. Get the plan broken down by tooth and both cost and visit count become far more accurate.

Where costs actually come down

• Catch it early. The cheapest treatment is the one where nothing gets drilled.
• Don't skip the re-check. Monitoring turned neglect grows a filling into an inlay, an inlay into a root canal.
• Check between teeth with X-rays. Decay growing unseen between teeth is the most regrettable kind.
• If under 12, use the covered resin option for permanent teeth. The same treatment costs far less.
• Know you don't have to do everything at once. Ordering by urgency spreads the burden.
• Don't choose non-covered materials where covered ones suffice. On an unseen inner molar surface, covered materials function the same. Choose material by position and size.

Choosing where to be assessed

In cavity treatment, a clinic's skill shows first not in the filling hand but in the eye that separates what to treat from what to watch.

• Do they explain each tooth's stage on the images? "Five cavities" versus "this one early, this one dentin" is the standard.
• Do they offer the monitoring option first? A clinic that wants to treat everything now differs from one that separates out what can wait.
• Do they use X-rays for between the teeth? Counting by eye alone misses interproximal decay or overcounts it.
• Do they set a re-check date? "Let's watch it" must not be the end; when to look again belongs in the plan.
• Do they actually watch you brush? Arresting early decay comes down to daily brushing.
• Do they separate covered from non-covered? The same cavity's coverage depends on material; check that they tell you in advance.

Clinician credentials can be verified through public records even at a community clinic. Our team is on the doctors page; apply the same standard elsewhere.

Common failure patterns

First, hearing "let's watch it" as "it's fine." Monitoring only works with a date attached. Let it drift and the stage will have changed by the next visit.

Second, panicking at the number and filling everything at once. Drilling early lesions that could have been monitored shortens the tooth's life by that much.

Third, not coming because nothing hurts. Even early dentin decay can be symptom-free. Symptoms are a late signal.

Fourth, treating while leaving the brushing unchanged. With the cause intact, new decay appears next to the filling.

Fifth, parents getting frightened by a child's slip first. Treating "five cavities" as a crisis in front of a child files the dentist away as a place of punishment. The slip is just a prompt to go and check; "the dentist wants to count your teeth" is enough for a child.

Reading a screening slip

School and national screening slips usually show only "caries: n," "suspected caries: n," "filled: n." Three things worth knowing:

• "Caries" and "suspected caries" differ. Suspected often means an early lesion or a spot needing confirmation — that number is not a treatment count.
• A screening is a quick visual look, so decay between teeth is sometimes missed and stains are sometimes flagged as decay. The slip is an instruction to get checked, not a diagnosis.
• "Filled" is the count of existing fillings — history, not a problem.

Bring the slip and we'll re-sort those numbers into stages per tooth. The count may rise or fall in that process; neither is cause for alarm.

In closing

Three things to take away. First, cavities are judged by depth, not count, and early decay confined to enamel can be monitored with care. Second, dentin decay only grows with waiting, so confirming that boundary on imaging comes first — differing counts between clinics are usually differing standards for where that line falls. Third, monitoring is only monitoring when it has a date; without one it's neglect — book the 3–6 month re-check before you leave.

If the number on a screening slip startled you, ask at your next visit not "how many" but "what stage is each one." That one question changes the plan. Decay progression and remineralization vary between people, so we'll give you a precise judgment after examination.

One-line summary: Cavities are about depth, not count. Separate what can be watched from what needs treating now — and if you're watching, set a date.

We are open until 9 p.m. on weekdays and 365 days a year, so re-check dates are easy to set after work or on weekends. After hours, our clinic's AI phone guidance runs 24 hours. We are about a 5-minute walk from Exit 1 of Dobong Station (toward the Dobong 1-dong post office), two stops from Changdong Station on Line 1, so patients from Ssangmun-dong and Chang-dong in Dobong-gu come without difficulty. If you are driving, see our parking guide.