Frequently Asked Questions (FAQs): Fillings

Several factors affect how long a filling can last.

These are:

• The Material used- Resin composites are not as durable as amalgam (silver) fillings.  However, the strength of resin composites have improved over time and some studies have shown that the durability of resin composites is similar to amalgam fillings when the right technique is used for placement.
• Size of the filling- the larger a filling is, the higher the likelihood of failure or other complications as a large filling means that there was a large amount of decay in the tooth to start with. With extensive decay, a tooth is more likely to develop further issues such as nerve inflammation. A larger filling is also more likely to chip or fracture. 

• The location of the tooth in the mouth affects the likelihood of the filling failing. A filling in a back tooth that does most of the chewing can wear down or chip more easily than a filling in a front tooth.

• Oral hygiene level will affect the lifetime of a filling. With poor oral hygiene, there is a higher likelihood of decay developing again under or around an existing filling, causing failure.

• A diet high in sugary and acidic foods can also lead to increased rates of decay under and around existing fillings.

The higher the number of fillings a person has, the more important it is to have good oral hygiene, avoid frequent sugary foods, have regular checks and cleans at the dentist in order to maximise the lifetime of the fillings.

Biocompatibility
All materials used in the dental setting have been approved by the Australian TGA (therapeutic goods administration)

Resin composites
Resin composites are commonly used routinely as a tooth-coloured filling material. There is concern from members of the public that they contain bisphenol A (BPA) which is thought to have oestrogenic effects on cells. The evidence comes from studies showing that BPA binds to oestrogen receptors in vitro. However, the oestrogenic effect of BPA is 1000-fold less potent than the native oestrogen hormone.

All current resin composites consist of methacrylate monomers (such as Bis-GMA) and DO NOT contain BPA. However, BPA is a synthetic chemical starting point from which all methacrylates are derived – in dentistry as well as many other plastics.

No evidence exists that dental composites have estrogenic effects in vitro or invivo.

Dental ceramics
Dental ceramics are very chemically inert materials and remain stable over very long periods of time. They therefore have excellent biocompatibility.

They furthermore exhibit excellent flexure strength, fracture toughness, wear resistance and colour stability. The ceramics can also be formed into precise shape to replace missing parts of a tooth.

They are an excellent material where a substantial part of a tooth is missing or for crowns.

However, in order to be held onto the tooth, the ceramic restoration has to be bonded to the tooth surface with a cement.  The cement in some cases has to be a resin cement in order to provide the best adhesion.  Resin cements have chemical similarities to resin composites which have been described above.

Reference: Phillips’ Science of Dental Materials, Kenneth J. Anusavice 2007.