Filling Options For Cavities

November 23, 2015 | Posted in Education


What material should we use to restore your damaged tooth?

How did you come to decide what type of material was to be used to restore your damaged tooth?  As a caring dental professional, we want you to be informed so that you can make appropriate decisions for your own dental health.

Classes of restorations

To give you more information on how to decide, let’s first of all discuss the various classes of restorations.  There are essentially 2 classes of restorations:  direct and indirect. 

Direct Restorations

Direct restorations, such as the silver mercury fillings and the new plastic fillings have certain characteristics on common.  They start out as soft materials, which are then stuffed directly into the prepared cavity to fill the hole.  They are then chemically hardened.  After they are hardened, they are carved to restore your tooth’s surfaces.

The advantage of direct restorations is their relative initial cost.  Silver mercury fillings are the least costly to use, which is why they have always been the most popular.  The newer tooth coloured plastic fillings are slightly more costly (as they require slightly more time, care, skill and judgement).  Direct restorations can be done in less time and in one appointment. 

Direct fillings impart no strength to the damaged tooth.  They simply fill the hole.
The disadvantage of direct restorations is their longevity.  Direct fillings break down faster.  If this simply meant having to replace them more frequently with a filling of the same size, it wouldn’t be too bad a thing (depending on how you see having treatment more frequently).  The real disadvantage is that the reason restorations need to be replaced is that, as they break down, they allow more disease to occur.  This necessarily means that the damage to the tooth is more extensive. 

The more damage a tooth has suffered, i.e. the larger the restoration, the more complex the treatment.  And the complexity of treatment and reduction of prognosis is an exponential relationship, not a linear one.  There is a truism in dentistry, that every small filling will grow up to be a big filling, and that every big filling will grow up to be a bigger one.  This will continue more and more quickly until the tooth can no longer be restored.

Sometimes, it is appropriate to use direct restorations to stabilize a dentition with a lot of disease (cavities, gum disease or biting problems).  Once the disease has been stabilized final restorations can be done in indirect materials.

Indirect Restorations

Indirect restorations, such as gold and the new ceramics also have certain characteristics in common.  At the mouth’s temperature, they are not soft or liquid so they cannot be simply stuffed into the hole of the prepared cavity.  This means that they must be made indirectly or outside of the mouth on some model or analog of the prepared tooth.  The disadvantage of indirect restorations is their initial cost.  They require more time, skill, care and judgement.  Up until recently, indirect restorations required two appointments, though we are now able to use CAD/CAM (see CEREC link) to do these restorations in 1 appointment.

Indirect materials, because of their physical properties, are better able to restore the diminished strength of a damaged tooth.

The advantage of indirect restorations is that the materials are much more robust and more similar to the tooth structure they are replacing or restoring.  This relates to a much longer life span especially when the restoration is larger.  This significantly reduces the vicious cycle of replacing larger and larger restorations mentioned under Direct Restorations above.  This means that while the initial cost may be greater, the long-term cost, intervention and prognoses are significantly better.  The choice is yours.

Size of Restorations

As the size of the filling or damage gets larger, less tooth structure remains.  This affects the health of the teeth in many ways.

First, the strength of the tooth is weakened.  It is easy to imagine that a whole, intact tooth is much less likely to break than a tooth that only has a thin wall of enamel left and is filled with a silver-mercury or plastic filling, which does not impart any strength.  Sometimes teeth can fracture in a way that is unrestorable.  This would necessitate losing the tooth.

Secondly the health of the tooth nerve is affected.  As the filling gets deeper, the nerve is more likely to be damaged to the point of needing a root canal. 

Thirdly, the health of the gums can be affected.  The best thing for the health of the gums is to have clean unadulterated tooth structure.  The health of the gums can be adversely affected by large fillings.  Some materials such as polished gold and polished ceramic are much healthier for the adjacent gums than the direct materials, which cannot be as easily polished. 

Larger restorations have a greater need to be made of the stronger indirect materials.  Again, because the direct materials are not as strong and long-lasting, they break down even faster when they start comprising larger parts of the tooth.

How do I decide what material is best for me?

Of course, the ultimate aim of comprehensive dentistry is to keep as much of your own tooth structure as possible in order to keep your teeth for a lifetime.  Consider your own goals for your teeth.  What do you expect for your teeth’s longevity?  Do you want them to still be present and healthy when you are a vibrant 85 year-old?  If so, then perhaps a proactive investment in your health today could ultimately be a better value.  Again the choice, now more than ever, is yours.
George W.S. Parry, DDS

If you have more questions related to filing options for cavities, or what we offer here at Rideau Dental Centre, give us a call at 613-230-7475.