What are Fillings & Bonding

The Term “Bonding” Actually Has Two Meanings

First, bonding is the method of attaching artificial tooth material to natural tooth structure at the molecular level. Second, the common term “bonding” outside of dental jargon usually refers to cosmetic modern dentistry using tooth-colored filling materials. The fact of the matter is that bonding, whether for cosmetic or functional purposes, has revolutionized dentistry during since the 1960’s, and the application of material engineering and the science of color and light perception by the human eye continue to enhance what modern dentistry can offer in the form of artificial tooth materials.

The History of Bonding

Prior to the 1950’s, it was not possible to actually attach restorative dental materials to natural tooth structure. All fillings and crowns had to utilize mechanical retention components like stainless steel and titanium pins screwed into dentin, slots drilled in teeth, and “pot holes” drilled in teeth to wedge filling materials into. It is easy to understand that these mechanical retentive features caused tooth injury and fracture, but they allow teeth that had decay to be saved for a period of time. In 1955, a follow by the name of Dr. Michael Buonocore introduced the concept of adhesive dentistry by presenting a scientific paper about using acid to etch enamel so that resin could attach to it. Since then, dental bonding agents have been continually improved to the point where it is now possible to reasonably bond to even dentin, which is the fluid-laden inner layer of a tooth.

Bonding adhesives are now used virtually in every aspect of restorative dentistry. These are just some of the uses for adhesive dentistry today:

• Ceramic crowns, onlays, and veneers are often bonded to the tooth.
• Sensitive areas on exposed roots of teeth can be sealed with dental adhesive.
• Deep grooves on the chewing surfaces of teeth are sealed with dental adhesive material to prevent decay (sealants).
• Metal fillings can be bonded to tooth structure.
• Tooth-colored fillings can greatly enhance ethetics with predictable outcomes.

Dental composite resin, the material used for “tooth colored fillings,” is simply dental bonding adhesive resin that has particles of glass, silica, and porcelain embedded into it for color and three-dimensional effect.

Dental composites, often referred to as bonding, come in many shades that correspond to natural tooth structure. Placing aesthetic bonding requires the clinician to have advanced skills like:

• Understanding tooth anatomy, not only in exterior form but also in 3-D architecture
• Understanding the science of adhesive dentistry
• Understanding color science so that the right hue, chroma, and value are created to mimic tooth structure
• Having the hand skills to put all of the above knowledge together to deliver a beautiful, natural restoration that cannot be discerned from natural tooth structure by the naked eye.

Cosmetic bonding is one way of creating a beautiful smile by artificial means.

Since the dental composite resins are softer than dental ceramics and because they are directly placed in the mouth by freehand, they are commonly used as a transitional restoration until a more definitive solution becomes possible. For example, cosmetic bonding may be used as a diagnostic tool to develop a prototype for future ceramic veneers. While dental composite resin restorations can be beautiful, they typical do not have the optical characteristics of ceramic restorations fabricated by a master ceramist in a dental laboratory under the skilled direction of a dentist, and they tend to have a shorter duration of service.

This patient desired to restore her worn front teeth.

“Bonding” was done to create a prototype of future ceramic veneers.

Cosmetic bonding with direct composite resin was done in one visit to replace the unsightly older resin restorations.

More About Fillings & Bonding

Facts about Fillings!

A dental filling fills a hole in a tooth that used to have natural tooth structure. That hole can be created by tooth decay or even when part of the tooth breaks off. While “fillings” can be made of tooth-colored ceramic or plastic, they can also be made from metal like gold or silver-colored dental amalgam. Most of the time, when dentists talk about fillings, we are talking about composite resin (“plastic”) and dental amalgam that are placed directly into the tooth while it is in the mouth, or direct restorations. In contrast, gold or ceramic “fillings” are referred to as indirect restorations, a term that also applies to crowns, onlays, and bridges.

Direct restorations are best used to address minor problems in teeth, like minor cavities or chips. Some of the problems with plastic or amalgam fillings are that they tend to be weaker than indirect restorations, may not have optimal shape and contours, may have incomplete seals against the tooth, and may not be as durable as indirect restorations. The bigger the filling, the less likely a direct restoration is to succeed for more than a few years.

Amalgam and composite fillings are typically less costly than indirect restorations. Sometimes, dentists will repair teeth with large direct restorations as an economical alternative to indirect restorations, but the compromises should be clearly understood by the patient. It may actually make more financial sense to invest money in optimal treatment than to patch and repair several times over several years, causing some degree of injury to the tooth multiple times. Sometimes, however, direct restorations may be the most appropriate treatment, even if they are large. For example, if a person is very prone to dental disease, then the investment in direct restorations may not be wise until the disease process has been controlled.

The choice of whether a filling should be a direct restoration or indirect restoration should be made after a thorough discussion between the patient and the dentist about the benefits and risks of each option. Unfortunately, many insurance companies will only pay for “the lowest costly alternative” rather than for the best treatment option. Fortunately, modern filling materials often can provide very nice restorations when used appropriately.

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Will My High Filling Wear In?

It is very common for new tooth-colored fillings, and temporary crowns, to be “high” after the numbness wears off. Usually, this is accompanied by “sensitivity” to cold foods or drink that disappears as soon as the tooth warms up to body temperature again. The same problem can also occur when new crowns are placed, depending on when the dentist records the way the teeth come together. Although a small percentage of this may be attributed to the physical properties of the filling material during their setting from a paste to a solid, most of these post-operative problems can be attributed to the way the muscles of the jaw respond to the mouth being open for extended periods of time.

The jaw is a complex appendage, held in place solely by muscles and ligaments. Between the jaw and the base of the skull, just in front of the ear, is a cartilaginous disc that is shaped sort of like a doughnut. A relatively small muscle, called the lateral pterygoid muscle, attaches to that disc and the jaw bone and pulls the disc forward and downward when the mouth opens. If overworked, this muscle can go into spasm, much like a Charlie-horse occurs in the calf muscles. Sometimes a spasming lateral pterygoid muscle can cause pain, but usually after a lengthy dental appointment it keeps the disc slightly forward of its relaxed position. This “opens” the bite on the back teeth slightly until the muscle completely relaxes, which may be hours or days after the appointment.

Since all of the contouring and adjusting of fillings and the making of temporary crowns occurs after the mouth has been opened for a time, it is often unavoidable for a dentist to leave them inadvertently “high”. Some dentists choose to record the way that teeth come together at the end of a crown appointment before making a temporary crown. This technique may inadvertently cause the permanent crown to be made “too high”. Regardless of how it occurs, most “high bite” cases can be attributed to a fatigued and spasming lateral pterygoid muscle.

The good news is that usually only a minor adjustment is needed to get the tooth comfortable again. However, larger pre-existing problems can become evident after even “simple” dental procedures that may otherwise have gone unnoticed until much more painful or uncomfortable symptoms arose. As examples, the tooth may be dying and beginning to abscess or the early stages of TMJ problems and headaches are beginning to appear. Older-style amalgam fillings tended to “wear in” for the first 24 hours after placement because they were not completely hardened immediately after placement; however, the new tooth-colored composite resins are just about as hard as they will get when the appointment is over. They will not “wear in”. This is why it is so very important to contact your dentist whenever a tooth is not comfortable after a dental appointment.

Why are my fillings turning black?

Amalgam Fillings Turning Black

Dental amalgam is the filling material that has been used by most dentists for many, many years to fix cavities in teeth. Essentially, it is a blend of metals like silver, copper, and tin. In order to make it moldable, a small amount of mercury is incorporated into the filling material, which allows it to be placed into a prepared tooth, sculpted, and then set up hard over the next 24 hours. When the mercury is bound with these other metals, it becomes an inactive substance, according to the American Dental Association.

During the past few years, dental amalgam has come under severe scrutiny by some groups who contend that dental amalgam is poisonous, unsafe, etc. However, there is currently no supported and refereed research to support this claim. Despite attempts by groups to blame various conditions and disorders on dental amalgam, there is absolutely no scientific proof. In fact, the American Dental Association, the Academy of General Dentistry, and the Food & Drug Administration maintain that dental amalgam causes no demonstrated clinical harm to patients when it is used appropriately and that dental amalgam in many situations is still the best material of choice for filling cavities.

Be that as it may, dental amalgam does have one noted and documented disadvantage. With time, the chemicals in the mouth cause the metals in amalgam to corrode. It has been suggested that this corrosion may be somewhat beneficial in sealing the cavity from further decay as the amalgam ages. However, many times, amalgam tends to “shrink” with time, or separate from the tooth, allowing a pathway for sugars, food, and bacteria to invade the tooth and cause recurring tooth decay alongside an old filling. This corrosion also causes the amalgam filling, which originally was a very clean-looking silver filling to turn black. Unfortunately, the natural tooth structure surrounding the enamel often is stained black by this discoloring as well, which is often irreversible.

Therefore, many dentists have opted to learn the proper techniques for using other dental materials for fillings instead of dental amalgam. These include bonded tooth-colored composite resins, porcelain, and gold. Each has its own unique advantages and disadvantages. Resin and porcelain are tooth-colored and do not usually “turn black” with time. Gold is usually considered to be the most durable filling material in the right mouth, but it is not very cosmetic unless it is covered with porcelain.

The fact of the matter, though, is that no one material is universally “the best.” An astute dentist will educate you on the materials available and help you select the one that is best for you. If your fillings seem to be turning black, it may very well be in your best interest to inquire about one of these other filling materials.