Dental Conservation PDF Print E-mail

Dental restorations are used to restore damaged or decayed teeth. They can frequently save teeth that would otherwise need to be extracted. Restorations include fillings, inlays and onlays, veneers, crowns, implants, bridges, and dentures. Dental restorations can be described as direct and indirect restorations. Some restorations require multiple visits to the dentist (e.g., crowns, bridges). Restorations can be made from a number of different materials, including amalgam, composite resin, ionomers, metal alloys, porcelain and porcelain fused to metal.

Before the dental restoration procedure begins, patients need to see a dentist for a dental examination to determine what type of restoration is right for them. The dentist may also evaluate the patient's medical and dental history. The general process for dental restorations is similar for all types of restoration. The tooth is first prepared for the restoration. Any tooth decay is removed and the tooth may be reshaped. If an indirect restoration is to be used, the dentist will take an impression to make the restoration. The restoration can then be placed and adjusted as needed. Once placed, restorations do not usually cause discomfort.

The longevity of a dental restoration depends on many factors, including the patient's health, dental hygiene, type of restoration, material and the location in the mouth. In general, dental restorations require the same care as natural teeth. However, it is typically recommended that patients with restorations avoid placing unnecessary stress on the restoration. Dental restorations can chip, fracture, break, come loose, fall off or become stained.

Types and differences of dental restoration

Dental restorations include direct and indirect restorations. Direct restorations are made in the dental office directly in the patient's mouth. Indirect restorations are created in a dental laboratory using impressions made of the patient's teeth. These usually require multiple visits to the dental office. Typically, a temporary restoration is placed in the patient's mouth between these visits. Indirect restorations tend to be more expensive than direct restorations, even when they are made from similar materials.

Only a dentist can decide what type of dental restoration is right for a particular patient. The different types of restorations include:
Fillings. These direct restorations are used to repair teeth that have been damaged by tooth decay and cavities. They can be used for the repair of very small or moderately sized areas of decay in primary or permanent teeth. Fillings can be made from amalgam, composite resin, or glass or resin ionomers. The longevity of a filling depends on several factors, such as the material, location, patient circumstances and skill of the dentist placing it.

Inlays and onlays. These indirect restorations can cover some or all of the chewing surface of molars or premolars. They are larger than fillings, but do not cover as much of the tooth as a crown. Inlays lie entirely within the contours of the tooth, between the cusps. Onlays cover at least one cusp. Both inlays and onlays can restore a tooth too badly damaged for a filling. The choice depends on how much of the tooth needs to be restored. For example, onlays are generally preferred when more than half of the chewing surface needs restoration. Inlays and onlays can be made from gold or other metal alloys, composite resin or porcelain and usually last for decades.

Veneers. Indirect restorations that are extremely thin shells placed on the front side of teeth. They are primarily used for cosmetic purposes (e.g., stained teeth, chipped teeth, gaps between teeth) and may be crafted from porcelain or composite resin. The lifespan of veneers is similar to crowns but depends on patient maintenance.

Crowns. These indirect restorations cover the entire visible portion of a tooth. Crowns can restore severely damaged teeth that other restorations cannot. They are also frequently used with bridges and implants. Crowns may be made from gold or other metal alloys, porcelain, porcelain fused to metal or composite resin. Crowns will usually last seven years or longer.

Implants. An implant is an indirect restoration made of an artificial tooth root that supports an artificial tooth or teeth (e.g., crown, bridge, dentures) surgically placed in the jaw. Implants are used to replace missing or lost teeth with stable, well-anchored, natural-looking artificial teeth. Implants are usually made of titanium metal alloy.

Dentures. A type of indirect restoration made of a removable dental appliance to replace missing teeth with artificial teeth attached to a gum-like denture base. Preparation and placement requires multiple visits to the dental office. impressions of the mouth and gums are taken and the materials are designed to look like natural teeth. They are usually made of porcelain or acrylic resin.

Surgical restoration. Teeth and gums damaged by accidental injury or disease may be repaired using different types of restorations depending on the damage. Surgery to repair the initial trauma and to restore and maintain teeth and gums may be necessary.

Types of Dental Restoration

There are two types of dental restorations: direct and indirect.

Direct restorations are fillings placed immediately into a prepared cavity in a single visit. They include dental amalgam, glass ionomers, resin ionomers and some resin composite fillings. The dentist prepares the tooth, places the filling and adjusts it during one appointment.

Indirect restorations generally require two or more visits. They include inlays, onlays, veneers, crowns and bridges fabricated with gold, base metal alloys, ceramics or composites. During the first visit, the dentist prepares the tooth and makes an impression of the area to be restored. The impression is sent to a dental laboratory, which creates the dental restoration. At the next appointment, the dentist cements the restoration into the prepared cavity and adjusts it as needed.

Amalgam Fillings

Used by dentists for more than a century, dental amalgam is the most thoroughly researched and tested restorative material among all those in use. It is durable, easy to use, highly resistant to wear and relatively inexpensive in comparison to other materials. For those reasons, it remains a valued treatment option for dentists and their patients.

Dental amalgam is a stable alloy made by combining elemental mercury, silver, tin, copper and possibly other metallic elements. Although dental amalgam continues to be a safe, commonly used restorative material, some concern has been raised because of its mercury content. However, the mercury in amalgam combines with other metals to render it stable and safe for use in filling teeth.

While questions have arisen about the safety of dental amalgam relating to its mercury content, the major U.S. and international scientific and health bodies, including the National Institutes of Health, the U.S. Public Health Service, the Centers for Disease Control and Prevention, the Food and Drug Administration and the World Health Organization, among others have been satisfied that dental amalgam is a safe, reliable and effective restorative material.

Because amalgam fillings can withstand very high chewing loads, they are particularly useful for restoring molars in the back of the mouth where chewing load is greatest. They are also useful in areas where a cavity preparation is difficult to keep dry during the filling replacement, such as in deep fillings below the gum line. Amalgam fillings, like other filling materials, are considered biocompatible-they are well tolerated by patients with only rare occurrences of allergic response.

Disadvantages of amalgam include possible short-term sensitivity to hot or cold after the filling is placed. The silver-colored filling is not as natural looking as one that is tooth-colored, especially when the restoration is near the front of the mouth, and shows when the patient laughs or speaks. And to prepare the tooth, the dentist may need to remove more tooth structure to accommodate an amalgam filling than for other types of fillings.

Composite Fillings

Composite fillings are a mixture of glass or quartz filler in a resin medium that produces a tooth-colored filling. They are sometimes referred to as composites or filled resins. Composite fillings provide good durability and resistance to fracture in small-to-mid size restorations that need to withstand moderate chewing pressure. Less tooth structure is removed when the dentist prepares the tooth, and this may result in a smaller filling than that of an amalgam. Composites can also be "bonded" or adhesively held in a cavity, often allowing the dentist to make a more conservative repair to the tooth.

The cost is moderate and depends on the size of the filling and the technique used by the dentist to place it in the prepared tooth. It generally takes longer to place a composite filling than what is required for an amalgam filling. Composite fillings require a cavity that can be kept clean and dry during filling and they are subject to stain and discoloration over time.

Ionomers

Glass ionomers are translucent, tooth-colored materials made of a mixture of acrylic acids and fine glass powders that are used to fill cavities, particularly those on the root surfaces of teeth. Glass ionomers can release a small amount of fluoride that may be beneficial for patients who are at high risk for decay. When the dentist prepares the tooth for a glass ionomer, less tooth structure can be removed; this may result in a smaller filling than that of an amalgam.

Glass ionomers are primarily used in areas not subject to heavy chewing pressure. Because they have a low resistance to fracture, glass ionomers are mostly used in small non-load bearing fillings (those between the teeth) or on the roots of teeth.

Resin ionomers also are made from glass filler with acrylic acids and acrylic resin. They also are used for very small, non-load bearing fillings (between the teeth), on the root surfaces of teeth, and they have low to moderate resistance to fracture.

Ionomers experience high wear when placed on chewing surfaces. Both glass and resin ionomers mimic natural tooth color but lack the natural translucency of enamel. Both types are well tolerated by patients with only rare occurrences of allergic response.

Indirect Restorative Dental Merials (Two or more visits)

Sometimes the best dental treatment for a tooth is to use a restoration that is made in a laboratory from a mold. These custom-made restorations, which require two or more visits, can be a crown, an inlay or an onlay. A crown covers the entire chewing surface and sides of the tooth. An inlay is smaller and fits within the contours of the tooth.

An onlay is similar to an inlay, but it is larger and covers some or all chewing surfaces of the tooth. The cost of indirect restorations is generally higher due to the number and length of visits required, and the additional cost of having the restoration made in a dental laboratory. Materials used to fabricate these restorations are porcelain (ceramic), porcelain fused to a metal-supporting structure, gold alloys and base metal alloys.

All-Porcelain (Ceramic) Dental Materials

All-porcelain (ceramic) dental materials include porcelain, ceramic or glasslike fillings and crowns. They are used as inlays, onlays, crowns and aesthetic veneers. A veneer is a very thin shell of porcelain that can replace or cover part of the enamel of the tooth. All-porcelain (ceramic) restorations are particularly desirable because their color and translucency mimic natural tooth enamel.

All-porcelain restorations require a minimum of two visits and possibly more. The restorations are prone to fracture when placed under tension or on impact. The strength of this type of restoration depends on an adequate thickness of porcelain and the ability to be bonded to the underlying tooth. They are highly resistant to wear but the porcelain can quickly wear opposing teeth if the porcelain surface becomes rough.

Porcelain-fused-to-Metal

Another type of restoration is porcelain-fused-to-metal, which provides strength to a crown or bridge. These restorations are very strong and durable.
The combination of porcelain bonded to a supporting structure of metal creates a stronger restoration than porcelain used alone. More of the existing tooth must be removed to accommodate the restoration. Although they are highly resistant to wear, porcelain restorations can wear opposing natural teeth if the porcelain becomes rough. There may be some initial discomfort to hot and cold. While porcelain-fused-to-metal restorations are highly biocompatible, some patients may show an allergic sensitivity to some types of metals used in the restoration.

Gold Alloys

Gold alloys contain gold, copper and other metals that result in a strong, effective filling, crown or a bridge. They are primarily used for inlays, onlays, crowns and fixed bridges. They are highly resistant to corrosion and tarnishing.

Gold alloys exhibit high strength and toughness that resists fracture and wear. This allows the dentist to remove the least amount of healthy tooth structure when preparing the tooth for the restoration. Gold alloys are also gentle to opposing teeth and are well tolerated by patients. However, their metal colors do not look like natural teeth.

Base Metal Alloys

Base metal alloys are non-noble metals with a silver appearance. They are used in crowns, fixed bridges and partial dentures. They can be resistant to corrosion and tarnishing. They also have high strength and toughness and are very resistant to fracture and wear.
Some patients may show allergic sensitivity to base metals and there may be some initial discomfort from hot and cold. However, due to their metal color, gold alloys do not look like natural teeth.

Indirect Composites

Crowns, inlays and onlays can be made in the laboratory from dental composites. These materials are similar to those used in direct fillings and are tooth colored. One advantage to indirect composites is that they do not excessively wear opposing teeth. Their strength and durability is not as high as porcelain or metal restorations and they are more prone to wear and discoloration.