TREATMENTS

Tooth Fillings

There are many restorative materials to choice from when deciding which filling to place where.  Each restorative material has its good and bad aspects.   It is important for you to understand the advantages and disadvantages of each type of restorative material.  Below is a summary.

Advantages and Disadvantages of "Silver fillings":

Advantages of amalgam fillings are that they are inexpensive, are covered by most insurance plans and in some very limited instances, such as repairing a hole in a crown made to perform root canal therapy, they may be the best choice.

The term "silver" in silver fillings refers mainly to the color of the filling material when it is first placed.  The main ingredient in an silver filling is mercury.  Currently, silver fillings or amalgams are composed of 43% to 54% by weight of mercury and the remaining powder is made up of mainly silver (~20-35%) and some tin, copper (~10%), and zinc (~2%).  A controversy exists as to whether placing filling containing mercury in teeth is safe.  Some countries such as Norway, Denmark and Sweden have banned the placing of amalgam filling in teeth.   As of 2008, the use of dental amalgam has been restricted in Finland and a committee of the US Food and Drug Administration (FDA) has refused to ratify assertions of safety.  Scientists agree that mercury amalgam fillings expose the bearers to a daily dose of mercury, but the level and effects of the chronic exposure are disputed. In the 1990s, several governments evaluated the effects of dental amalgam and concluded that the most likely health effects would be due to hypersensitivity or allergy. Germany, Austria, and Canada recommended against placing amalgam in certain individuals such as pregnant women, children, those with renal dysfunction, and those with an allergy to metals.

Amalgam fillings have other issues.  By unavoidable design, silver/mercury fillings ultimately result in a weaker tooth structure because the tooth must be prepared (drilled) to accommodate the inability of silver/mercury fillings to hold together in small areas.  In addition, the amalgam fillings asymmetically expand or "creep" with age.  An expanding metal filling in a tooth combined with the heavy bite force of a tooth bruxer, for example, often split teeth. There is a cycle in dentistry that you may have experienced.  The cycle begins with a small amalgam filling, progresses to a large amalgam filling, a tooth fracture and ends in a crown.  If the fracture is severe the cycle continue on to an extraction, implant or bridge.  How does one interrupt this cycle?  The answer is to remove large old amalgam fillings before they fracture your tooth and have a restoration placed in your tooth that does not expand or contract.  The difficult part of the decision is to decide when to replace the amalgam.  The color of the restoration can give you a some indication of the age of the filling.  The darker the filling, the older it is.  Of course, crack lines radiating out from the amalgam or pain upon chewing are bad signs. Unfortunately, these are your only clues.  If you knew when the tooth would fracture, you could have the tooth restored just before the it broke.  Unfortunate, the decision on when is the best time to replace you amalgams is not so clear cut.  A rational approach for most people is to replace their oldest amalgams over time so that you never have to deal with having a crown when a smaller restoration would do or deal with the loss of a tooth.

Another problem with amalgam is that it does not seal to tooth structure.  Amalgan restorations are retained by "mechnical retention" much like a nail in wood.  Why then you may ask do amalgam filling last so long?  You may have amalgam fillings in your teeth that are twenty years old.  There are two answers to that question.  The first is that many people confuse the existance of a filling with a succeeding filling.  In other words, just because a filling has not fallen out, does not mean that it is succeeding.  The second part to the answer is that amalgam fillings corrode and bacteria cannot live in a corrosive environment.  It is not until the bacteria are in such a number that they overwhelm the corrosive layer that recurrent decay becomes a problem.  At first this may not seem to be a bad thing, however, the by-products of corrosion leach into your tooth and gums and stains them blue/gray.  This staining cannot be washed away and requires removal of the stained portion tooth or gum tissue to correct the problem.  For these reasons, we have not placed amalgam fillings in our practice for over twenty years.

Even though we are an amalgam-free practice, many people have silver/mercury fillings in their teeth from years past. These fillings are not particularly esthetic. Porcelain inlays and Tooth Colored Restorations (onlays) create fillings that are not only beautiful (or unnoticeable) but also add strength to weakened teeth. These restorations are esthetically pleasing and very strong thanks to new bonding techniques.

Advantages and Disadvantages of Tooth-Colored Restorations

There are two main types of tooth colored restorations.  The first type is a composite resin also known as "bonding".  The advantage of composite resins are that they may be placed in one visit, are bonded to your remaining tooth structure sealing out bacteria and are relatively economically priced.  The disadvantages are that they shrink when the are cured (placed), are difficult to shape anatomically when placed and do not have longevity when placed in large defects.

The second type of tooth-colored restoration is a porcelain or resin onlay.  Porcelain and resin onlays are very similar, only differing by the glass content of the restoration.  Advantages of porcelain or  Resin onlays are that they also are sealed to your tooth, do not expand or contract over time, are processed in a laboratory under high temperature and pressure and, therefore, are much stronger and long-lasting than directly placed composite resins.  Since they are processed on a die (tooth replicate) they can be created with ideal contours to avoid food impaction between your teeth fostering gum health.  If sufficient tooth structure exists, they are superior to a crown because they are more biologically conservative.  An onlay only replaces lost tooth structure leaving the balance of the tooth intact and stronger.  Since the bonding agent used to adhere in tooth-colored restorations contain fluoride.  This can help prevent decay. The restoration wears like natural teeth and does not require placement at the gum line, which is healthier for your gums. The disadvantage of onlays is that they are more expensive than composite resin.

Both composite resin and porcelain onlay require bonding to adhere to tooth structure.  Teeth have different layers.  The outer layer is enamel, the middle layer is dentin and the nerve resides in the inner layer.  The bond strength of resin to enamel is strong, however, the bond strength to dentin is not.  If the restoration needs to end on dentin, another restorative choice must be considered.

Which restoration is best for which tooth?

To begin, the difference between front and back teeth must be considered.  It is a basic law of nature that things do what they look like they do.  Front teeth have an edge and a single root.  Their function is to bite or tear like a scissors.  Back teeth have a large, flat biting surface and multiple roots.  Their purpose is to grind food like a mortar and pestle.  The mechnics of jaw closure are such that back teeth are subjected to alot more force per unit area than front teeth as you expect by their morphology.  Therefore, the further back in your mouth the restoration is, the more you will benefit from an indirect restoration (onlay).

The size of a defect also must be considered because the larger the restoration, the greater the impact of shrinkage during curing will have on the tooth.  Just curing a large composite in a small tooth can fracture the remaining walls of the tooth.  Therefore, the larger the restoration, the more you will benefit from an indirect restoration (onlay).

For examples,  if you have a small defect in a front tooth.  The ideal restoration would be a composite restoration because the tooth is not subjected to a heavy force load when chewing and a small restoration does not require great cohesive strength to succeed.  Also, a composite resin is the most economical choice.  There is no benefit in choosing a more expensive lab processed restoration.  On the other hand, if you had a large restoration on a back tooth, then a lab processed restoration such as an onlay would be required for long term success.  Other consideration are whether the restoration ends in enamel or dentin, whether the patient has any parafunction (bruxism) habits, among other things.  When an individual treatment plan is created for our patients, all these considerations are evaluated for each tooth and the optimal choice is presented.

Replacing Silver Fillings with a Tooth Colored Restoration

If you need your silver fillings replaced with tooth-colored restorations (onlays). This process requires two appointments.

Your First Appointment:

  1. The old filling is removed along with any additional decay.
  2. An impression is made of your teeth. A model of your teeth is made and sent to the lab.
  3. A temporary onlay is placed on the tooth.

At the dental laboratory a natural looking porcelain restoration is constructed to replace the damaged or lost tooth structure.

Your Second Appointment:

  1. The temporary onlay is removed.
  2. A conditioning gel is placed on your tooth to prepare it for the new onlay.
  3. Bonding agent is placed on the tooth and a high intensity light bonds the resin to the tooth.
  4. The tooth is then polished.

Your teeth are restored to a natural look and feel, they are stronger and the tooth is protected!