Frequently Asked Questions About Restoring Teeth

Cavities in teeth can be restored directly into the tooth, or indirectly by fabricating a filling (restoration) in the laboratory, then cementing it to the tooth. The material choices are:

Direct restorations

• Silver amalgam
• Composite resin
• Glass ionomers

Indirect restorations

• Composite resin
• Porcelain
• Ceramics
• Gold and non-precious alloys
• Porcelain fused to metal alloys

The choice of filling (restorative) material will depend on the:

• Biting force applied to the area to be restored
• Depth and extent of the cavity
• Importance you place on having a tooth-coloured restoration
• Cost - indirect restorations cost more than direct restorations
• Longevity of each type of restoration

Discuss the choice of the materials used with your dentist. To help you make an informed decision, a brief summary of the features of each type of filling material is described below:

Silver amalgam

Silver amalgam has proven its durability and has been in use for over a century as a filling material to restore cavities in teeth. It is a combination of mercury and a silver alloy which when initially mixed becomes a plastic mass that can be adapted into the cavity before it sets hard.

Now and again, some groups have raised health concerns regarding the use of mercury in silver amalgam fillings. Numerous health authorities around the world (including an independant scientific review by the Life Sciences Research Office, USA, 2004) have examined the available scientific evidence and all have unanimously concluded that silver amalgam is safe to use.

Silver amalgam is still the most cost-effective and durable of all the filling materials.

Advantages:

• Very durable
• Good wear resistance
• Not technique-sensitive
• Cost-effective

Disadvantages:

• Colour does not match teeth. Therefore, usually used for posterior teeth only
• Requires mechanical retention to stay in position
• May conduct hot/cold sensation to teeth in deep cavities
• Environmental concerns with use of mercury
• Allergy in a extremely small percentage of the population

Composite Resins

This tooth-coloured filling is now very popular. It consists of inert inorganic fillers in a resin matrix. It is usually hardened by initiating polymerization with a blue light. They are available in different shades and opacities to match teeth. They can be used for use both anterior and posterior teeth.

Advantages:

• Excellent colour match possible
• Adheres to tooth structure
• Cavity shape conserves tooth
• Does not transmit heat/cold to the tooth

Disadvantages:

• Technique sensitive
• Does not last as long as silver amalgam in posterior teeth
• Discolours after many years
• Allergy in a small percentage of the population

Glass-ionomer

This is another tooth-coloured restoration, consisting of fine glass particles in a matrix. However, it is less esthetic than composite resins, as well less resistant to wear than the others. Therefore, it is usually used to restore cavities in non-load bearing areas like the root surfaces of teeth.

Advantages:

• Acceptable colour match
• Adheres to tooth structure
• Cavity shape conserves tooth
• Leaches fluoride which is anti-cariogenic
• Doesn't transmit heat/cold to tooth

Disadvantages:

• Quite technique sensitive
• Insufficient strength to use on the biting surfaces of teeth
• Surface stains more easily than composite resin
• Surface dehydrates in smokers and mouth breathers, causing surface break down

Porcelain/Ceramic

Requires to be fabricated or milled in the laboratory, hence will usually require two visits. Can be used for fillings, crowns and short span bridges (fixed partial dentures). They have to be cemented to the tooth. As the physical properties of ceramics keep improving, ceramic crowns are becoming increasingly more popular as they look very aesthetic.

 

Advantages:

• Excellent match possible
• Stable colour
• Wear resistant
• Doesn't transmit heat/cold to tooth

Disadvantages:

• Brittle — weak in tension. May chip or crack.
• Potentially it could wear opposing teeth if the porcelain/ceramic surface is rough

Gold and Base Metal Alloys

Like porcelain, it requires to be fabricated in the laboratory, hence will usually require two visits. These very versatile restorations need to be cemented to the tooth. Gold and semi-precious alloys are easier to work with but their price swings with the vagaries of the global economy. They wear at approximately the same rate as tooth enamel. While base metal alloys are more economical, they are harder, consequently, they tend to wear down the opposing tooth.

Advantages:

• Very durable
• Strong - can be used in thin sections
• Gold alloys wear at same rate as tooth enamel

Disadvantages:

• Does not match tooth colour
• Gold alloys are relatively expensive
• Base metal alloys are hard and wear away opposing teeth
• Nickel containing base-metal alloys may cause allergic reactions in some people

Porcelain Fused to Metal

This combines the strength of metal with the esthetics of porcelain. Usually used for crowns and bridges that are cemented to the tooth. This is probably the most commonly used type of crown though increasing the ceramic crowns are becoming popular as their physical properties have been improving through the years.

This simple question has a very complex answer! The quality of different brands and types of materials, the manipulation and the different oral environments each filling is subject to all have a bearing on the longevity of the restoration. A guide* to the expected longevity of different types of dental fillings is:

Material	Tooth Type	Median Survival Time
* Downer et al. How long should routine dental restorations last? A systematic review. British Dental Journal 1999; 187:432-9.
Amalgam	Posterior	6-20 years
Composite	Anterior	6-10 years
	Posterior	6 years
Cast gold	Posterior	10-20 years

Silver amalgams remain the most cost-effective restoration. The very popular tooth-coloured composite resin restorations, are between 2 to 3.5 times more expensive then the longer lasting amalgam restorations.

The answer is it all depends! Let's try to be a little more helpful

The World Health Organization considers 20 teeth the minimum required from a functional point of view. So if you have at least 20 teeth, functionally you're still OK. This is especially so when the last teeth in the arch are lost — for example, when wisdom teeth are removed, its lost has no detrimental effect and they need not be replaced. However, as teeth tend to keep erupting till they find the opposing teeth to function against, the remaining opposing tooth may end up biting on the gums of the opposite jaw.

When an intermediate tooth is lost, the adjacent teeth remaining may drift and tilt into the space, and sometimes the opposing tooth may over-erupt into the opposing gap. (See rollover image left for original intact set of teeth). Sometimes, there may not be any changes either. Which of these occurs depend on how the upper and lower teeth meet.

The narrow gaps that open out because of drifting teeth could become food traps — if not diligently cleaned each day, the food that is trapped could lead to both gum problems and tooth decay. Therefore, it is best to restore the gap caused by tooth loss before these complications set in.

In the front of the mouth, this space will also spoil your smile. Missing teeth only look cute in babies and young children!

The available options to replace lost teeth are:

Fixed methods

• Bridge
• Implant retained crown

Removable methods

• Acrylic denture
• Cobalt-chromium denture

Bridge

Also known as a fixed partial denture. The replacement tooth is most commonly anchored in place on opposite ends by a crown, which is cemented onto the teeth on either side of the gap. This usually takes two visits to complete. The disadvantage is that the teeth that anchor the replacement tooth has to be shaved to provide space for the porcelain and/or metal of the bridge. Long term, replacement cost of the bridge is higher than implant-retained crowns as the bridge will need to be renewed.

Implant Retained Crown

A titanium implant that integrates with bone, is placed into the space. A crown is then cemented or screwed into the implant. The treatment is more complex and the placement cost is higher than a conventional bridge. The advantage is adjacent teeth are not involved, and therefore, over the long term, replacement cost for the single unit crown is lower than a bridge.

Acrylic denture

This removable option is the most economical method. As the plastic plate that holds the replacement teeth has to be sufficiently thick to prevent breakage, it intrudes into the tongue's space, which initially may affect speech. Most people, however, are able to adapt with time. Food tends to get between the denture and the gums, therefore, the denture will need to be removed after meals to clean out the food particles. Wires to hold it in place may sometimes be visible.

Cobalt-chromium denture

As this base metal is far stronger than acrylic, the plate that holds the replacement teeth can be thinner and less extensive, providing more flexibility in design. Consequently it is more comfortable to wear. Like the acrylic denture, food tends to get between it and the gums, therefore, the denture will need to be removed after meals to clean out the food particles. Wires to hold it in place may sometimes be visible.