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Cavities and Broken Teeth
WHAT ARE CAVITIES? Teeth can suffer damage from a variety of things. The most common damage is that caused by cavities. Bacteria, which occurs naturally in the mouth, feeds on sugar in food particles trapped in the teeth and produces an acidic waste product which can destroy the hard material of the tooth. This creates a soft area which, if left untreated, will continue to grow until the entire tooth is destroyed. HOW ARE CAVITIES PREVENTED? There are many things which can be done to help prevent the formation of cavities. Proper daily flossing and brushing help remove the food particles which fuel the process of decay. Bacteria feeds on sugar so it is especially important to brush after consuming foods with high sugar content. Reducing the intake of these foods can also be helpful. Regular dental exams are the best way to prevent major problems with cavities. An examination and x-rays can diagnose cavity formation when it is still in its early stages, thus reducing the extent of the restoration required. HOW DOES A DENTIST FIX CAVITIES? When treating cavities, the procedure includes removing the softened material and the bacteria within. The resulting hole is then lined with a protective material and filled with a restorative material. This stops the process of further decay. Cavities represent only one of several ways a tooth may be damaged. Teeth can become worn, broken, chipped or cracked from age or unnatural stress placed on them (such as using your teeth to open things). HOW IS A BROKEN TOOTH FIXED? The process to repair a broken tooth is similar to the process of repairing cavities. The dentist prepares the tooth to receive the filling, fills the prepared area, and then shapes the surface of the filling to ensure proper function and comfort. This will correct whatever problem is being treated and restore the tooth to its original health and function. DO FILLINGS HAVE TO BE REPLACED? Yes. Several things might indicate the need to replace an old filling, including: a new cavity on a tooth. If a cavity touches an existing filling or needs support from an area where a filling exists, it will require replacement of the old filling; fracture of a tooth or a filling itself; breakdown of filling material, similar to metal rusting, which may allow food to be trapped and a cavity to be formed; or, excessive wear of the filling which may interfere with proper function. WHAT IF A TOOTH IS TOO WEAK TO SUPPORT A FILLING? WHAT IS A CROWN? A crown is a special method used to restore weak teeth. The crown surrounds and supports tooth structure which is not strong enough to support itself. The tooth is reduced and shaped around the outside and across the top so a crown can fit tightly over it. Crowns are sometimes referred to as "caps" and the terms are interchangeable. WHAT ARE POSTS AND PINS? Pins provide additional support for very weak teeth. Pins are placed one to two millimeters into sound tooth structure. A small hole is drilled and the pin is carefully screwed into it. Filling material is then placed around the pin and against the tooth. If a crown is necessary, the crown then surrounds the pin (or pins), the filling material and the remaining tooth structure. Posts are used in much the same way, but are used when the tooth has had a root canal performed. Posts are placed in the root canal and are cemented to the root structure. They extend above the gums and support a crown. Posts may be cast in one piece or combined with filling materials and pins to obtain the best support. Occasionally, especially if minimal tooth structure remains, a root canal may be intentionally done so a post can support the crown. DO CROWNS TAKE LONG TO MAKE? Crowns require two or more appointments. At the first appointment, precise drilling is done, impressions are taken to make plaster models and a temporary crown is placed. The permanent crown is fabricated in a dental laboratory through a series of complicated procedures and is then returned to the dentist. At the second appointment, the permanent crown is tried in the mouth, checked to ensure proper health, function and aesthetics and is then cemented into place. Occasionally crowns need adjustments which may require additional appointments. BONDING Bonding is a technique, rather than a material, used in restorations. At a microscopic level, organic material is removed from the surface of the tooth creating a honey-comb effect. Special materials fill in the honey-comb and adhere to a filling material (usually composite or porcelain). Bonding can accomplish several things. It can be used to lighten the color of teeth, fill in missing tooth structure or rebuild fractured teeth. It can also fill spaces between teeth or reshape teeth to look straighter or more pleasing. ARE THERE DIFFERENT TYPES OF FILLINGS? Yes. All materials used in dental restorations have unique advantages and disadvantages based on a wide variety of characteristics. When choosing the appropriate material for a filling, the dentist considers the different strengths of the material, what color it is, how workable it is, how long it takes to apply , how well it will wear, and how expensive it is. All these actors must be considered relative to the type of restoration being done, its location and the health of the affected tooth. The following is a list of the different materials used in restorations. Weighing good and bad characteristics most often determines whether or not the material can be used in a given situation. Your dentist can define the alternatives for you in any situation, and will advise you on the relative advantages in choosing a material for your specific restoration. AMALGAM (SILVER) Amalgam is an alloy (mixture) of silver, copper, tin, zinc and mercury. Mixing these elements results in a soft material which is easily worked. Initial hardness occurs within minutes but full hardness requires hours. For that reason, a patient can not chew on an amalgam filling right away. Strong compressive strength make it an ideal restorative material but low shear and tensile strength mean it must be surrounded by strong tooth structure. This material is easy to use and relatively inexpensive. There is controversy surrounding health consequences of filling materials that contain mercury. It is considered a safe restoration in the United States but has been banned in many foreign countries. The material should not be used in areas where the remaining tooth structure is weak. It can not be used on teeth where aesthetics is a concern due to the color. The material will deteriorate with age which may require replacement. Amalgam may lead to cusp fracture which results from wedging effects from mechanic forces and expansion with heat.
COMPOSITE Composite is white plastic material mixed with fillers to increase strength and wear. Microfil composites have less filler with smaller particle size and are used for front teeth. Macrofil composites have more filler and larger particle size and are used primarily for back teeth. Composites are used in any area where aesthetics is a primary concern and there is minimal tooth destruction. They require less drilling to produce good retention and the color is excellent. Cost is relatively low, although composites on back teeth may be more expensive than on front. Composites require strong tooth structure to support the filling because the tensile and shear strength is low. Under certain conditions they do not wear well, and the placement technique of the material is critical for long term success.
A thirteen year old girl fell and fractured her right central incisor. The tooth is restored with bonded composite to produce superior esthetics with limited strength. The tooth will be crowned when the patient is older.
HEAT PROCESSED COMPOSITE Composite restorations are stronger when thoroughly cured with heat, pressure and nitrogen. A heat processed composite restoration is stronger than a directly placed composite, but weaker that a crown. A heat processed composite restoration does not destroy as much tooth structure as a full crown and therefore, is less traumatic to a tooth. Heat processed composites require two or more appointments. At the first appointment, precise drilling is done, impressions are taken to make plaster models and a temporary crown is placed. The permanent restoration is fabricated in a dental laboratory through a series of complicated procedures and is then returned to the dentist. At the second appointment, the heat processed composite is tried in the mouth, checked to ensure proper health, function and aesthetics and is then cemented into place. Occasionally heat processed restoration need adjustments which may require additional appointments.
GOLD Gold has modifiers added to it which increase hardness. Harder gold may be required in a filling designed to support weak tooth structure. Softer gold can be used in small restorations where the tooth can support itself. Most gold restorations are cast in a laboratory which increases the work, time and cost. Strong compressive, shear and tensile strength make it the ideal restoration for any operative treatment. Gold can be used in any situation because of its strength, wear, non reaction to surrounding tissue and longevity. It is not commonly used because of the color, time for construction and cost. Gold requires two appointments, laboratory time and the cost of constructing a temporary restoration for use while the laboratory makes the gold restoration.
PORCELAIN Porcelain is glass with modifiers added to increase strength. Porcelain is used when aesthetics is the primary consideration and wear may be a factor. It provides excellent color, and good strength and wear. Porcelain restorations require laboratory work, extra appointments and the construction of a temporary restoration for use while the laboratory constructs the permanent restoration. For all of these reasons, porcelain is more expensive than most other fillings.
Copyright 2001 www.dentaleducator.com
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Old
amalgams show breakdown and leakage at the edges of the fillings on the
left picture. They are replaced with the new amalgams to the
right. 
The
teeth in the top picture reveal caries and tooth fracture. The teeth
are restored with direct composite on the first bicuspid, and stronger
heat processed composite restorations on the second bicuspid and the first
molar (the two teeth to the left). 
Gold
covers tooth structure to prevent fracture, however, esthetics often
limits its use.