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Robert W. Corsello, DMD
Robert W. Corsello, DMD

Martha D. McCarthy, DMD
Martha D. McCarthy, DMD

Locust Place
Sewickley, PA 15143
(412) 741-6350

Tooth Anatomy
Restorative Dentistry Crowns, Implants, and Dentures

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Each tooth has a crown visible in the mouth above the level of the gums (gingiva) and a root which is embedded in a socket in the jawbone. The crown is protected by a covering of enamel, the hardest tissue in the body. The bulk of the tooth is made up of dentin. Softer than enamel, dentin is made up of millons of cells arranged in tubules. The pulp chamber occupies the space in the center of the crown and the canal which runs through the root canal. This chamber contains the nerves and blood vessels that supply the tooth. The outside of the root is covered with a hard bone-like substance which attaches the tooth to the bony socket. There are 4 different types of teeth.
  • Incisors in the front which have sharp chisel-like edges that cut food
  • Canines (cuspid) with their sharp single-pointed crown that tears food
  • Pre-molars (bicuspid), located behind the canines, are used to crush and tear food
  • Molars, located at the back of the mouth, have multiple cusps to grind the food. The last molar is called the wisdom tooth.
Why replace any teeth if the space doesn't show?

If back teeth are lost, adjacent teeth can shift into vacant spaces causing a change in tooth alignment. Plaque builds up more easily increasing the risk of decay and gum disease. This shifting of teeth may result in upper and lower teeth meshing together in a way that impairs chewing and creates stress on other teeth and the jaws. The lips may thin and straighten, the chin may jut out and upward, and pouches may appear on the sides of the cheeks. Replacing a single tooth or multiple teeth shortly after extractions can prevent these problems. If a long period of time elapses between the time of the extractions and the attempted replacements the teeth may have "drifted" resulting in the above problems. Then further tooth removal may be required to accomplish good esthetics and function. Several kinds of tooth replacements are possible including fixed and removable bridgework, dentures, dental implants, and crowns. Hopefully, the following information will offer answers to some of the most common questions concerning tooth replacement.

Fixed Bridgework

A bridge is a device used to replace one or a few missing teeth and can either be applied permanently (fixed) or they can be removable. With a fixed bridge, the artificial teeth are attached to the adjacent natural teeth, called abutment teeth. Sometimes crowns are placed on the abutment teeth on each side to provide support for the bridge. Sometimes, the bridge is simply cemented, or bonded, directly to the abutment teeth. Both methods require that the adjoining teeth are healthy and have adequate gum and bone support. Fixed bridgework can be used to replace both teeth in the front and back of the mouth. Fine esthetics can result because the metal substructure is covered with porcelain which matches the natural teeth. In certain cases, all porcelain bridges can be fabricated as well.

Complete Dentures

A complete set of dentures is the only solution when all teeth are lost in the lower or upper dental arches. Dentures are formed from acrylic resin and can be made to closely resemble your natural teeth. Complete dentures are either "conventional" or "immediate." Conventional dentures are made and inserted after the remaining teeth are removed and the tissues have healed. Healing may take several months. An immediate denture is placed as soon as the teeth are removed. The obvious advantage is that you don't have to go without teeth during the healing process. The main drawback behind an immediate denture is that it may require more adjustments after the healing has taken place.

New denture wearers need time to get used to their new "teeth" because even the best fitting dentures will feel awkward at first. . The dentures may feel loose and slip while the muscles of your cheek and tongue learn to keep them in place. While most patients can begin to speak normally within a few hours, many patients report discomfort with eating for several days or a few weeks. To get accustomed to chewing with a new denture, start with soft, easy-to-chew foods. In addition, denture wearers often notice a slight change in facial appearance, increased salivary flow, or minor speech difficulty. Over time most individuals adapt to their dentures and do well. Dentures should be removed at night. Studies have shown that removing dentures for at least eight hours each night allows gum tissue to rest and allows normal stimulation and cleansing by the tongue and saliva which promotes better long-term health of gums.

Dentures do require some maintenance. Dentures may lose their shape if they are allowed to dry out. When they are not worn, dentures should be placed in a denture cleanser soaking solution or in water. Like natural teeth, dentures must be brushed daily to remove food deposits and plaque. Brushing helps prevent dentures from becoming permanently stained and helps your mouth stay healthy. Dentures are very delicate and may break if dropped. They should not be sterilized with boiling water because this will warp them. It's best to use a brush designed for cleaning dentures or a toothbrush with soft bristles. Ultrasonic cleaners are also used to care for dentures. However, using an ultrasonic cleaner does not replace a thorough daily brushing. To maintain a proper fit over time, it may be necessary to adjust dentures or possibly remake them periodically. One should never attempt to adjust a denture and should not use denture adhesives for a prolonged period because it can contribute to bone loss. When in doubt, consult your dentist.

Removable Partial Dentures

Removable partial dentures work best for those who have several or more missing teeth or adjacent teeth which are compromised. Clasps fit onto natural teeth and the framework fits directly on the gums for support in chewing. Using hidden clasp techniques and tooth colored clasps, today's partial dentures can be made to almost disappear in one's smile.

Dental Implants

Dental implants are artificial tooth supports surgically set in the jawbone. Replacement teeth are permanently attached to the part of the implant that projects through the gums. This anchors the new tooth the same way roots support natural teeth. A single tooth can be replaced without altering the adjacent natural teeth or implants can be used in combination with bridges, dentures, and crowns to replace any number of teeth.

Dental implants are not for everyone. Candidates for these are adults in general good health who have healthy gums, adequate healthy bone to support the implant, and a commitment to meticulous oral hygiene and regular dental visits. Implants are made from bio-compatible materials are not rejected by the body. With over 20 years of clinical experience, dental implants provide a long-lasting alternative to removable dentures that may wobble, click, or cause pain.

The main disadvantages of dental implants would be the greater investment in time and money and the fact that significant surgery is involved. The entire three-step process may take up to 9 months to complete. With any surgery, there is always some operative and anesthetic risk as well as some postoperative discomfort during healing.

Step 1
The first step is surgically placing the metal anchors into the jawbone. This procedure can take several hours and can be done under general or local anesthesia. Pain medicines, antibiotics, and a soft diet are usually prescribed for about a week after surgery. Gradually, bone attaches to the implants holding them firmly in place. This process of attachment called osseointegration can take from three to six months.
Step 2
During a second surgical procedure, small metal posts are attached to the base. These project upward through the gums. (With some implants the anchor and post are already attached and placed at the same time.)
Step 3
After several weeks of healing, replacement teeth are created and securely attached to the small metal posts. Because several fittings may be required, this step can take one or two months. When the process is completed, the implants are as strong as the original teeth and appear very natural.

Dental Crowns

Dental crowns (also knowns as caps) are used in a variety of situations. A crown is used when a large cavity or a fracture has destroyed one or more cups (corners) of a tooth. Large fillings can be placed, but most likely will not be as durable as a crown. A posterior tooth which has undergone a root canal should be crowned to prevent fracture of the tooth root which nearly always results in tooth removal. Crowns are often used for esthetic treatment of front teeth as well. An example would be placing a crown over a tooth that became dark after an old injury. This would return the tooth to its natural color.

To prepare a tooth for a crown, the dentist removes enough tooth structure and/or filling to make room for the crown to fit over the tooth like a thimble. When done, the tooth should be restored to its original size and shape.

Dental Crown Procedure
Step 1
The process usually involves at least two visits. During the first visit, the dentist removes any decay and reshapes the tooth to make room for the crown. Then a mold, or impression, is made for the dental lab so that new crown will fit exactly. A temporary crown is then placed over the bare tooth to protect it.
Step 2
On the second visit, the temporary crown is removed and the permanent crown is cemented into place. Once a crown is placed, most patients soon become totally unaware of them. With proper care, they can last for years.

Types of crowns include the all-metal crown, the porcelain over metal crown, and the all-porcelain crown. All metal crowns do not match the original teeth and are only used in the back of the mouth. Porcelain is most often used since it can be dyed to match the original teeth. Porcelain crowns with a metal base sometimes causes a grey color or dark line to form at the gumline and some individuals develop an allergy to the metal base. A new advance is the use of all-porcelain crowns which do not have this metal substructure. These new materials provide a very natural look, replicating the natural shading and translucency found in your own teeth.

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