Signs of Tooth Decay: How to Tell If a Tooth Is Rotting

Nearly one in three Australian adults has at least one tooth with untreated decay right now. Most of them don't know it. That's the frustrating part of tooth decay: the early signs are quiet, and by the time a tooth actually hurts, the damage has usually been building for months. Bradbury Dental Surgery, your trusted dentist in Campbelltown, sees this pattern every week in Campbelltown. Here's how to spot the signs of tooth decay early, while the fix is still small.

What Are the First Signs of Tooth Decay?

The first sign of tooth decay is usually a chalky white spot on the enamel, most often near the gum line. It's not pain. It's not a hole. Just a dull, matte patch that looks slightly different from the glossy enamel around it.

That white spot is demineralisation, which means acid from plaque bacteria has started pulling minerals out of the enamel surface. At this stage the tooth is weakened but not yet cavitated. No hole has formed.

Other early signs to watch for:

• A brief twinge when you eat something sweet (sweet sensitivity often shows up before hot or cold sensitivity)

• A rough spot you can feel with your tongue where the tooth used to be smooth

• Slight darkening in the grooves of your back teeth

• Food catching in the same spot between two teeth, again and again

  
  

We often pick up early decay on an x-ray or during a check-up before the patient has felt a single thing. The digital OPG we use at our Bradbury clinic shows decay between teeth that's invisible from the surface. That's the whole point of six-monthly checks: catching decay at the stage where it can still be reversed.

How Can You Tell If Your Teeth Are Rotting?

You can tell your teeth are rotting if you notice brown or black discolouration, a visible hole or pit, persistent bad breath, a bad taste that won't go away, or pain when biting down. "Rotting" is really just advanced decay, and by this stage the signs are much harder to miss.

Run through this quick self-check:

1. Look. Brown, grey or black spots that don't brush off, especially in the grooves of molars or along the gum line.

2. Feel. Slide your tongue over each tooth. A catch, a rough edge or a soft spot where enamel should be hard is worth getting checked.

3. Bite. Sharp pain on pressure often means decay has reached the softer dentin layer under the enamel.

4. Smell. Decay traps food and bacteria, so persistent bad breath or a sour taste can point to a cavity you can't see.

5. Temperature. Lingering pain after hot or cold drinks (not just a flash, but an ache that hangs around) suggests the decay is getting close to the nerve.

   
   

One thing worth saying plainly: a tooth can look fine and still be rotting from the inside. Decay that starts between two teeth or under an old filling often shows nothing on the surface until it's quite advanced.

The Stages of Tooth Decay: What You'll Notice at Each Point

The signs and symptoms of tooth decay change as it moves through the layers of the tooth. Here's how the stages line up, including what we can see clinically versus what you'll actually feel.

Stage	What you feel	What we see	Reversible?
1. Demineralisation	Nothing	Chalky white spot on enamel	Yes, with fluoride and better hygiene
2. Enamel decay	Usually nothing, maybe sweet sensitivity	Brown spot, early cavity forming	No, but a small filling fixes it
3. Dentin decay	Sensitivity, twinges when biting	Visible cavity, decay on x-ray	No, needs a filling
4. Pulp involvement	Toothache, lingering pain, night pain	Deep cavity approaching the nerve	No, often needs root canal treatment
5. Abscess	Throbbing pain, swelling, sometimes fever	Infection at the root tip	No, urgent treatment needed

In our experience, most patients first book in somewhere around stage 3 or 4. The tooth has started talking to them. The problem is that stages 1 and 2 were the cheap, easy stages, and they passed by silently.

Why Doesn't Early Tooth Decay Hurt?

Early tooth decay doesn't hurt because enamel has no nerves. Pain only starts once decay breaks through into the dentin, which connects to the nerve inside the tooth. So no pain doesn't mean no decay.

This is why waiting for pain is such an expensive strategy. Australian data backs this up: adults who only visit the dentist when something's wrong are nearly twice as likely to have untreated decay as those who go for regular check-ups (44% compared with 24%, according to the Australian Institute of Health and Welfare).

And the national picture isn't improving. The proportion of Australian adults with untreated decay has climbed from roughly one in four in 2004-06 to almost one in three in 2017-18. Cost is a big part of that, with nearly four in ten adults delaying dental visits because of it. A small filling costs far less than a root canal and crown, which is exactly what early decay becomes when it's left alone.

Can Slight Tooth Decay Be Reversed?

Yes, slight tooth decay can be reversed, but only at the white spot stage, before a cavity forms. Once there's a hole in the enamel, the tooth can't repair itself and needs a filling.

Here's the decision rule we use, and you can apply a rough version of it at home:

• Chalky white spot, surface still smooth: reversible. Professional fluoride, a high-fluoride toothpaste and cutting back on sugary drinks can remineralise the enamel over 3 to 6 months.

  
  

• Brown spot, or a catch your tongue can feel: past the point of reversal. It needs assessment and probably a small filling.

  
  

Living in Campbelltown helps here, since Sydney's water supply has been fluoridated for decades and that gives your enamel a constant low-dose repair supply. It's not enough on its own, though. If we spot early demineralisation at your check-up, our fluoride treatment at Bradbury Dental Surgery can concentrate that repair effect exactly where it's needed.

What Happens If Horrible Tooth Decay Is Left Untreated?

Untreated tooth decay progresses in one direction: deeper. Left alone, a cavity grows through the dentin, infects the pulp, and can form an abscess at the root. At that point the options narrow to root canal treatment or extraction.

We treat advanced decay at our Bradbury clinic regularly, and the pattern is nearly always the same. The tooth hurt for a while, then the pain stopped, and the patient assumed it had healed. It hadn't. The nerve had died, and the infection kept spreading quietly. If you've been told you need root canal treatment, our guide to pain after root canal explains what recovery actually looks like.

Decay in one tooth also raises the risk for its neighbours, since the same bacteria and the same habits are working on every tooth in your mouth.

When Should You See a Dentist About Tooth Decay?

See a dentist as soon as you notice any sign of a decaying tooth: a spot that won't brush off, new sensitivity, food trapping, or a rough patch. Don't wait for pain, because pain means the cheap window has closed.

For kids, decay moves faster because baby teeth have thinner enamel. Parents across Campbelltown and the Macarthur region should know that eligible children can have examinations and fillings covered under the Child Dental Benefits Schedule, which takes cost out of the decision. Our post on tooth decay in baby teeth covers the warning signs specific to little ones.

If it's simply been more than six months since your last visit, a dental check-up at our Campbelltown clinic is the reliable way to catch decay you can't see or feel.

Frequently Asked Questions

Does tooth decay always show visible signs? 

No. Decay between teeth or under existing fillings can be completely invisible from the surface. That's why dentists use x-rays at check-ups, since they reveal decay long before it's visible or painful.

Can tooth decay spread to other teeth? 

The bacteria that cause decay live throughout your mouth, so the conditions that rotted one tooth put every tooth at risk. Decay doesn't "jump" between teeth directly, but neighbouring surfaces often decay together, especially where food gets trapped.

How fast does a cavity form? 

It varies with diet, hygiene and saliva, but decay typically takes months to years to progress from a white spot to a cavity. In children and people with dry mouth it can move much faster, sometimes within six months.

What does tooth decay smell like? 

Advanced decay often causes a persistent sour or foul smell that brushing doesn't fix, because bacteria and trapped food sit inside the cavity where your toothbrush can't reach. Bad breath that won't go away is worth a dental check.

Worried About a Spot or a Twinge?

Early tooth decay is one of the easiest things we fix, and one of the most expensive things to ignore. If you've noticed any of the signs of tooth decay covered here, a short appointment will give you a clear answer. And if a filling is needed, you can read about our white filling options at Bradbury Dental Surgery before you come in.

Call us on (02) 4628 2151 or book online. We check for decay at every examination, and catching it early is the whole game.