How long does it take for a cavity to form? –

Cavities take time to form.

A person doesn’t just get a cavity overnight. It typically takes months, or possibly even years, before the decay process has advanced to a point where it requires attention. (That’s why your dentist feels comfortable enough only examining you every 6 months.)

It takes that long because conditions aren’t always right for the continued progress of the demineralization process (the action that actually causes cavities).

Reasons why it takes time for cavities to form. –

A) Decay formation is a cumulative process.

The process of tooth demineralization (cavity formation) takes place whenever an acidic oral environment exists. (This state is created by acids produced by bacteria living in dental plaque as they consume sugars, use link above for more details.)

• Fortunately, an acidic environment isn’t usually the norm for a person’s mouth. “Normal” values usually lie around pH 7 (this is considered “neutral”).
• But every instance when a person’s mouth’s pH drops to a level of around 5.5 or below (considered acidic conditions and referred to as the Critical pH), some tooth damage occurs.

  (The precise cutoff point varies according to conditions in the person’s mouth. This includes the amount of calcium and phosphate in their saliva, and the level of resistance of their teeth to the decay process.)

▲ Section references – Fejerskov, Dawes

A tooth can only withstand for so long.

After innumerable cycles of acidic attack, a point may finally be reached where the cumulative effect of each small episode of demineralization has finally resulted in the formation of a cavity (a hole and associated tooth damage) that has advanced to the point where the person’s dentist determines that it’s now in need of repair.

Animation #1.

Our first graphic illustrates the scenario that takes place during the time frame when a cavity develops.

Animation #1

Cavity formation is the cumulative effect of repeated acid attacks stemming from dental plaque accumulation.

• When dental plaque accumulates on a tooth’s surface, the acids produced by the bacteria that live within it as they consume their available sugary food supply cause damage (demineralization) to the tooth surface that lies underneath.
• When the plaque is brushed or flossed away, the current attack is stopped. But the damage it has already caused still remains.
• If plaque reforms, the acid attack will resume. And this adds further to the damage that occurred previously.
• If plaque is allowed to persist on the tooth’s surface often and long enough (such as the case where a person doesn’t brush as frequently or as thoroughly as they should), a full-fledged cavity will ultimately form.

Extensive tooth decay.

B) Tooth surface characteristics that affect a cavity’s timeline.

1) Dentin vs. enamel.

The surface of a tooth is composed of either enamel (which is white in color) or dentin (the hard, light-yellow tissue that makes up the roots of teeth).

• Dentin contains about a quarter less mineral content than enamel. And with all other factors being equal, it’s the one that’s more prone to the effects of the demineralization process and thus cavity formation.
• This difference means that cavities will form more easily, and advance more quickly, on areas of dentin (like exposed root surfaces) than on comparatively harder enamel-covered regions.

2) Enamel thickness.

One of the criteria that a dentist uses in determining if a developing cavity requires repair is if it has yet penetrated through the tooth’s enamel layer.

• Portions of the tooth where its enamel covering feathers down from full-thickness to a micro-thin edge down by its gum line.
• The thickness of enamel on deciduous (baby) teeth is about 1/2 that of permanent ones (Mortimer).

▲ Section references – Mortimer

3) Enamel quality.

Variances in the composition or status of a tooth’s enamel surface can affect how quickly a cavity will form.

• Tooth enamel can contain porosities, which may affect how prone it is to tooth decay.
• Mortimer determined that the degree of mineralization of the enamel of baby teeth was lower than that of permanent ones (on the order of 10%), and therefore could be a factor in the speed with which cavities form and spread.
• The tooth enamel molecule hydroxyapatite can, and frequently does, contain impurities (like fluoride) that makes it more resistant to the demineralization process.

Months are usually involved.

The actual amount of time that it takes for any one cavity to form will probably lie on the order of at least many months, and quite possibly (even probably) longer.

Summitt’s textbook of operative dentistry (the repair of teeth) states that it may take 4 to 5 years before the demineralization process has progressed through a tooth’s enamel. Considering the perpetual back and forth nature of cavity formation (repeating cycles of demineralization vs. remineralization), one would have to assume that even that range could be exceeded.

▲ Section references – Mortimer, Dawes, Hilton

C) Remineralization – Another reason why cavities take time to form.

Cavity formation isn’t a straight-line event.

Beyond just demineralization, there’s another important dynamic that takes place with teeth. If conditions are right, a tooth can undergo “remineralization.”

This process is somewhat like tooth decay in reverse. And in effect, it counteracts the damage that has occurred during tooth demineralization (in both enamel and dentin).

How does remineralization reverse cavity formation?

When conditions at a tooth’s surface return toward neutrality (above the Critical pH), the process of remineralization has a chance to take place.

[Historically this has sometimes been stated as pH 7.5 or above. But in reality, and as with the Critical pH itself, the actual number varies according to current conditions in the mouth.)

When it has, minerals drawn from the oral environment (saliva, the fluid in plaque, foods & beverages, oral rinses, toothpaste, etc…) are re-deposited onto the tooth. As they are, they’re able to repair and rebuild the tooth’s damaged apatite crystals (the main calcified component of teeth).

• Until the repair is complete, or at least completed to the highest degree possible, thus reversing the damage that was caused by the demineralization process.
• Or until the pH of the mouth drops back down below the Critical pH (such as the case where dental plaque has reformed, the bacteria in it feed on dietary sugars, and as a result start producing acidic waste products again).

▲ Section references – Pitts, Dawes

It’s a constant tug-of-war.

This back-and-forth action between demineralization and remineralization (both can take place several times a day) is one reason why cavities typically take many months, or even years, to form.

Animation #2

Minor damage caused by the tooth decay process (demineralization) can be repaired by remineralization.

• In some cases, the remineralization process will be able to balance out the damage created by demineralization.
• However in those cases where there’s heavy plaque accumulation or the person has a high or frequent sugar intake, the balance between the two processes will likely tip to the side that favors decay formation.

Animation #2.

But then if the tooth’s surface is kept plaque-free, remineralization has a chance to take place and repair at least some of the damage that’s occurred.

D) Signs that a full-fledged cavity has finally formed.

The constant back and forth between demineralization and remineralization can continue on indefinitely. (In fact, it will continue to occur on various aspects of your teeth throughout your entire life.)

As it does, one of three scenarios will ultimately play out. Although how long this takes is entirely indefinite.

• In the case where conditions primarily favor remineralization, the tooth will remain intact and healthy.
• If demineralization tends to predominate, decay formation will advance. The earliest sign of an actual cavity forming is termed a “white-spot lesion.” We discuss their formation and appearance here.
• Over time, if local conditions remain favorable for demineralization, an outright cavity will finally form. This will typically take a few months or even years.

  Frank cavities frequently involve the situation where softened, demineralized tooth structure is lost. So if the affected surface of your tooth is one you can visualize, you’ll likely see that a portion is missing (hence the term “cavity,” as in hole).

  Of course, you can’t see what’s going on in between your teeth. Fortunately however, your dentist can. Here’s how they check for cavities using x-rays.

E) All cavities require prompt attention.

Just because cavities can take a long time to form, doesn’t mean that once they’ve been diagnosed they don’t need immediate attention.

If you have the situation where tooth damage is readily visible, or your tooth experiences sensitivity due to the presence of decay, it must be resolved promptly. Delaying treatment will only worsen the outlook for your tooth’s repair and health.