Reasons Why A Filling May Need To Be Replaced

Fillings are never as strong as unfilled teeth, and rarely will a filling last a lifetime. Thus they will occasionally need replaced, and there are a variety of reasons for needing to do so. Some of these reasons will be obvious to you, for example if a filling is broken or unsightly.  Other reasons for replacing a filling, such as decay under the filling may not be obvious.  Decay and damage can usually only be spotted by your dentist at your check-ups.


Replacing a Filling: Reasons Why a Filling Can Fail

There are lots of reasons why a filling can fail. Here are the main factors:

Tooth with decay under a filling

Decay Under a Filling: Replacing this filling sooner would have stopped this decay from spreading.

Tooth Decay

“But my tooth is filled, how can it decay again?”  If you do not look after your teeth in terms of your oral hygiene and diet, decay can set in.  This is just as likely under an existing filling, if not more so, as in a tooth that doesn’t have any work done.  This can occur whether or not there is a problem with the filling.  But if a restoration cracks or leaks, decay can set in very quickly.  This can spread to cause a lot of damage before you become aware of it.  Getting any fillings checked is an important reason for visiting the dentist regularly.  The sooner decay is found and the restoration replaced the better!


Physical Damage to a Filling

If a filling is exposed to certain forces this can cause it to wear down, crack or fall out.  Such forces may include:

  • Normal chewing forces.  Chewing forces are quite large and over time these can wear down fillings.
  • Clenching and grinding.  These habits can lead to excessive forces on fillings.  If you clench or grind your teeth you are more likely to have problems, as well as other dental treatments such as crowns.
  • Trauma from outside sources such as a sports injury, chewing fingernails or pens.  Front fillings are more at risk from this.
  • Biting down hard on a filling may break it, especially if it is large.


Very Large Fillings

If a filling is very large, it is more at risk of failing and therefore need replacing.  There are a variety of reasons for this:

  • Large fillings may be unable to withstand physical forces in the mouth.
  • Teeth that have large restorations are more likely to be weak and therefore at risk of fracturing.  If a tooth fractures the filling often falls out also.
  • There may not be enough tooth substance left to fold the filling in place.  Here a crown will usually be needed.



White fillings can gather staining, especially at the edges.  This is usually treated by smoothing down the edges but sometimes replacement is needed to get an acceptable result.

White fillings may also change color over time.  This is more likely with older materials.

Another reason for replacing white fillings is after whitening.  Here the teeth will brighten but any composite will not change color.  Therefore they may need to be replaced to match in with the new shade.


Leaking Fillings

A filling ‘leaks’ if a gap has opened up between it and the tooth.  Even small leaks will allow food debris, saliva and plaque bacteria into the gap.

White leaking filling

This tooth has an old leaking white filling, with a stained margin as a result

Leaking fillings can lead to sensitivity and decay.  White fillings may become discolored around the edges.

Amalgam fillings may leak a little in the first few weeks before they naturally expand and micro-corrode to fill the space.

White fillings are more at risk of leaking, due to the fact that they shrink a little when they set.  This can lead to gaps, especially if the restoration is not placed correctly in the first place.
If there is a problem with a filling, sometimes a repair can be enough to fix it.  Your dentist will discuss this with you.

If the whole filling needs replacing, your dentist may use a different material based on why it failed and/or your preferences.



There are many reasons why the treatment can fail over time, they will rarely last for a lifetime!  So there are many reasons why replacing a filling will be needed.  It might be obvious to you when you need one replaced, for example if it falls out.  But sometimes there can be problems that you are unaware of.  This is one reason for attending your dentist for regular check-ups!


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