When a patient presents with a cavity, we face several decisions: 1) What is the best way to restore the affected tooth to proper form and function? 2) Is one option more predictable in terms of long term reliability and strength? 3) Are there any economic or insurance factors that will affect the treatment decision? 4) Are cosmetics an influencing factor?
As we explore the options, we need to consider such issues as the size of the cavity, the strength of the remaining healthy tooth structure, the position of the tooth in the mouth, the presence of parafunctional habits such as clenching or grinding, and the overall treatment plan for the patient.
Assuming a full coverage restoration, such as a crown or bridge, is not indicated, it is likely that the tooth will be restored with some type of "filling." Fillings consist of direct or indirect restorative materials that are either condensed into or bonded to the affected tooth. These restorative materials are generally classified as porcelains, resins (composites), and amalgam (silver) alloys. In the past, gold was also a popular option, but now has been all but abandoned due to high cost.
Porcelains can be used indirectly to fabricate tooth colored inlays and onlays which are then bonded into the prepared tooth. These restorations are strong, show excellent esthetics and color stability, and excellent wear resistance. The only downsides of porcelain inlays and onlays are increased time involved for fabrication and higher cost.
Resins (composites) are tooth colored polymers that are directly placed, usually light cured, and bonded to the prepared tooth. They are highly esthetic, but fall back in terms of wear resistance and strength from porcelains. In my experience, it is rare to see a 15 or 20 year old composite, especially in the posterior areas of the mouth, that does not show significant microleakage or wear. When composite restorations are used, it is normal to need replacement more frequently than porcelain or metal restorations.
Amalgam, or "silver", fillings consist of a mixture of silver (65% or more), tin (up to 29%), copper (6 to 13%), and zinc (up to 2%), all bound together with mercury. In an amalgam restoration, the mercury is bound in the alloy, and thus rendered inert. It is no longer poisonous, as it is in free, elemental mercury that you might find in a thermometer. The different metals in amalgam restorations are introduced to provide specific properties to the restoration. The American Dental Association's team of biomaterials researchers have been studying the safety and effectiveness of amalgam materials for decades. All studies to date have found that amalgam is safe and effective, and no scientific links have been found to MS or any other systemic diseases, disorders, or syndromes. This is not some government or political coverup. Amalgams simply will not hurt you. It is my opinion, as well as that of the ADA, that removal of amalgam fillings to "cleanse" the body and cure systemic disease is contraindicated and unnecessary. If someone wishes this treatment for esthetic reasons, that is a different issue entirely, but for a practitioner to recommend this treatment in the name of systemic "cleansing" borders on malpractice.
This having been said, let's discuss the benefits and downfalls of amalgam restorations. I think it is fair to say that amalgams last longer than composites, and are definitely more resistant to wear. I think it is also obvious that amalgams do not look good. They are without a doubt the most unesthetic of all the dental restoratives. They also corrode and stain the surrounding tooth structure, and can be a significant contributor to tooth fracture due to the significant difference in thermal expansion between amalgam and natural tooth structure. The key, however, is that they last, and are less expensive. This is why many dental insurance carriers consider them their restoration of choice and often will only cover the cost of an amalgam, even if another restorative material is chosen. If a patient chooses to have a tooth restored with composite or porcelain, often the cost difference is passed to the patient by the insurance company.
Given all of this information, how do we determine which restoration is right for a given situation? We do it by following a few simple rules:
1) If the cavity involves 2 surfaces of the tooth or less, and is not deep, composite can be sucessfully used. Amalgam is also an option if cost or insurance is an issue.
2) If the cavity involves 3 or more surfaces of the tooth or is deep, either a porcelain restoration, such as a crown, inlay, or onlay must be used, or else amalgam. Composite is too weak and is not a good choice in this situation.
Each situation is different, so we need to examine the tooth and apply the rules before determining the best course of treatment. See you at the office!!