Teeth needing simple or small restorations for repair of decay, tooth fracture, or to possibly replace a failing restoration are candidates for a dental filling. A dental filling replaces lost or removed tooth structure with another material which then fills or restores a defect, returning it to function and stopping further tooth breakdown. Today’s advancements in dental restorative materials have provided the prosthodontist with many options with which to repair singular and simple dental needs. There are two categories of materials, metals and synthetics, offering the most routine and accepted methods for simple dental restorative procedures.
Dental silver amalgam filling material has been the staple of dental filling materials for well over 100 years. Amalgam is composed of varying amounts of silver, copper, tin, and zinc bound by inorganic mercury (For the American Dental Association position paper on the safety of dental amalgams see the web site link under Patient Care Information). Dental amalgam has proven to be a long lasting and durable filling material serving many patients 30, 40, and even 50 years as a restorative material. Amalgams are comparatively inexpensive for the patient and require a single visit for placement. In areas of the mouth where esthetics are not of primary concern and where strength and endurance are, dental amalgam is often the restoration of choice for patients concerned with cost and longevity of the restoration.
Like dental amalgams, both cast gold and direct gold placement fillings have been a long serving and reliable dental filling material. Direct gold fill is the practice of placing 100% gold leaf into a prepared tooth cavity, compacting each layer and thus forming a restoration meticulously adapted to and filling the tooth preparation. Because of the ever-rising cost of gold and the time and technique require to place a direct gold filling, this restoration has fallen out of practice. Cast gold, however, is still a viable and desirable dental restorative material. Depending upon the quantity of gold in the alloy used, dental gold can manifest identical wear and thermal response properties as enamel and because of this gold remains the material of choice for the posterior tooth restoration.
Dental composite filling material has been available since the mid 1970’s and has quickly become a highly used material because of its tooth coloration and the ability to bond it to prepared tooth structure. Dental composite is composed of varying mixtures of a plastic resin and finely ground glass, or quartz, particles. For small anterior tooth fillings dental composite has proven to be unsurpassed in its acceptability to both the patient and restorative dentist. Composite use in filling posterior teeth is more limited, however, due to its lack of strength in large restorations and its abrasiveness against enamel. Bonding of the filling material to enamel lends greatly to its overall strength in anterior and small fillings, however as the prepared dental cavity increases in size the amount of enamel is small compared to the exposed dentin which has a much less predictable bonding strength and longevity. This makes the composite filling material much less desirable for large posterior tooth restorations as compared to metal or porcelain materials.
Dental composite may be directly placed into the cavity preparation by the practitioner or a denser and stronger restoration may be fabricated by a dental laboratory for placement into the cavity preparation which has improved clinical properties but still carries many of the poorer characteristics of the composite materials.
Dental ceramic materials, or dental porcelain, are the most esthetic of all dental materials. Manufacturers have produced many different types of dental porcelains to satisfy the demands restorative dentistry has placed for use of the material. Porcelain may be used from simple posterior tooth cavity fillings to anterior tooth veneers or full tooth covering crowns. Dental technicians have become very skilled at utilizing fabrication techniques and materials to gain lifelike appearance of porcelain restorations. Use of fabricated porcelain as a simple cavity restorative material has been limited, however, due to the added office visit for placement and technique sensitivity of the material; dental porcelains are also very unforgiving in their use as they are susceptible to chipping and fracture during placement and lack the bonding ability to enamel that other materials exhibit.
Dental zirconia, specifically yttria tetragonal zirconia polycrystal (Y-TZP ), has been available in dentistry for several years but has seen greater use in the last few years with developing technologies and computer milling techniques. Zirconia has the benefit of increased strength and fracture resistance over many metals used in dental restorations and, having no glass matrix, it is resistant to cracking failure often seen in dental ceramics. Zirconia also has the ability to be used as a single monolithic filling material or as a substrate or matrix onto which dental porcelain can be bonded thus providing the great benefits of both an extremely strong and very esthetic restoration. As with dental ceramics, zirconia often is not the material of choice for simple tooth cavity restoration due to added technical requirements and time of fabrication as compared to metal or composite fills.
Metal Free Fillings
The last decades have seen a rise in practitioners offering metal free dental restorations as an alternative to traditional metal based restorations. This is a false declaration as virtually all synthetic dental filling materials contain some percentage of a metal or various metals in their formulation. These metals are included to affect the physical and mechanical properties of the material, to influence the color of the material, and often to provide radiopacity, or the ability to see the material in dental x-rays. Though some manufacturers offer completely metal free materials, those materials offer poor esthetics or unsatisfactory clinical properties. Manufacturers make efforts to keep the metal content to a minimal but the case remains that metals are used in the production of all currently used and common dental materials so that a truly “metal free” dental restoration has yet to be provided to the dental community acceptable for routine use.