Dental Restorations in AlexandriaThere 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, 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 a silver filling is mercury. Currently, silver fillings or amalgams are composed of 43% to 54% by weight of mercury and the remaining portion is made up of silver (~20-35%) and some other metals such as 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, 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 and then progresses to a large amalgam filling. The large filling predisposes the tooth to fracture which often must be repaired with a crown. If the fracture is severe enough, the tooth may have to be extracted and implant or bridge considered.
How does one interrupt this cycle? The answer is to remove large old amalgam fillings before they damage the tooth then 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 of when is the best time to replace amalgam fillings is not so clear cut. A rational approach for most people is to replace their oldest amalgams over time. This is often the best way to avoid having a crown or experiencing a fracture that may result in the loss of a tooth. Another disadvantage with amalgam is that it does not adhere to tooth structure. Amalgam restorations are retained by “mechnical retention” much like a nail in wood.
A question many patients ask is: If amalgam fillings have so many disadvantages, why do they seem to last so long? Many patients have amalgam fillings in teeth for more than twenty years. There are two answers to that question. The first is that many people confuse the existence of a filling with a succeeding filling. Just because a filling has not fallen out, does not mean that it is succeeding. The filling may be surrounded with caries and the tooth may be breaking apart but in the absence of pain many patients do not perceive a problem. The second part to the answer is that amalgam fillings corrode and bacteria cannot live in corrosion. 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 letting an amalgam restoration corrode 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. The result in gum tissue is called an “amalgam tattoo’. The result in enamel is dark or blue teeth. This staining cannot be washed away and requires removal of the stained portion tooth or gum tissue to correct the problem. For these reasons, most contemporary dentists do not place amalgam fillings. Our practice has not placed amalgam fillings in our patient’s teeth for over thirty years.
Not all amalgam filling need replacement, simply because they are made of amalgam. Small, polished amalgams in an unaesthetic zone can be left alone indefinitely. For large amalgam restorations, especially in areas that can be seen when smiling, Porcelain inlays and Tooth Colored Restorations (onlays) are often recommended as they create restorations that are not only natural looking (unnoticeable) but also strengthen compromised teeth. Porcelain inlays and onlays are esthetically pleasing restorations that are very strong due to their ability to be bonded into the tooth.
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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 advantages of composite resins are that they may be placed in one visit, are bonded to your remaining tooth structure sealing out bacteria and are 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 in the restoration. Advantages of porcelain or Resin onlays are the following:
- they also are sealed to the tooth
- they do not expand or contract over time
- they are processed in a laboratory under high temperature and pressure and, therefore, are much stronger and long-lasting than directly placed composite resins
- they can be created with ideal contours to avoid food impaction between your teeth fostering gum health since they are processed on a die (tooth replicate)
- if sufficient tooth structure exists, inlays or onlays are superior to crowns because they are more biologically conservative (an onlay only replaces lost tooth structure leaving the balance of the tooth intact and stronger)
- the bonding agent used to adhere tooth-colored restorations contain fluoride which can help prevent decay
- they wears like natural teeth and do 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 resins and require two visits to complete. Both composite resins and porcelain onlays require enamel in order to adhere the restoration to tooth structure. As you may know, 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 tooth preparation extends beyond the enamel layer and ends on dentin, another restorative choice such as a gold onlay or a crown must be considered.
Which restoration is best for which tooth?
To begin, the difference between front and back teeth must be considered. Often 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 mechanics of jaw closure are such that back teeth are subjected to a lot more force per unit area than front teeth as you would expect by their morphology. Therefore, the further back in your mouth the restoration is, the more the tooth will benefit from a stronger (indirect) restoration (onlay).
The size of a defect also must be considered. Composite resins (bonding) shrink when cured. The larger the restoration, the greater the impact of shrinkage during curing will have on the tooth. Rapid curing a large composite in a small tooth can fracture the remaining walls of the tooth. Therefore, the larger the restoration, the more the tooth will benefit from an indirect restoration (onlay).
For example, 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, a small restoration does not create significant internal stress on the walls of the tooth preparation when cured, and a composite resin is the most economical choice. There is little benefit in choosing a more expensive lab processed restoration.
Another example would be a large restoration on a back tooth. In this case, a lab processed restoration such as an onlay would be the best choice for long term success. Other considerations are whether the restoration ends in enamel or dentin and 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 presented.
Replacing Silver Fillings with a Tooth Colored Restoration
If you choose to have amalgam fillings replaced with tooth-colored restorations (onlays), the process requires two appointments.
- The old filling is removed along with any additional decay and unsupported tooth structure.
- An impression is made of your teeth and sent to our dental laboratory.
- A temporary onlay is placed on the tooth.
A natural looking porcelain or gold restoration is constructed to replace the damaged or lost tooth structure.
Your Second Appointment:
- The temporary onlay is removed.
- A conditioning gel is placed on your tooth to prepare it for bonding to the new onlay.
- Bonding agent is placed on the tooth and a high intensity light is applied to bond the onlay to the tooth.
- The bite is adjusted and the tooth is polished.