Complete set of upper teeth as viewed from below.

Complete set of lower teeth as viewed from above.

    Other conditions which might affect whether an implant is the right choice include the health of the gum tissue around the teeth on either side of the space. These conditions along with the amount of bone available for the correct placement of the implant must be analyzed.

    The most challenging tooth to replace with an implant is an upper front tooth. Both aesthetics and function come into play here. The implant must be precisely placed so that it appears as natural and lifelike as possible. This entails careful evaluation by the oral surgeon and general dentist with attention to the cosmetic needs of the patient as well as the functional requirements of the tooth to be replaced. Both bone and soft tissue must be adequate or the position of the implant will be wrong and it may not appear as though it is emerging from (or growing out of) the gum tissue. Sometimes it is not possible to achieve an ideal match of the implant tooth to the teeth on either side. Most of the time, however, an excellent result can be obtained if there is adequate pre-surgery planning and attention to detail.

Replacing Posterior Upper Teeth

    Replacing upper molars and bicuspids presents the greatest surgical challenge for the oral surgeon. Here, aesthetics is secondary since these teeth are not usually visible. Of primary concern is the quality and quantity of the bone and the oral surgeon's ability to precisely place the implant for best function. Because the bone in the back of the upper jaw is less dense and usually limited because of the sinuses in the upper jaw, the highest failure rate exists with upper posterior implants. Many times the sinuses must be filled with a bone graft in order for the oral surgeon to place implants in the back of the upper jaw. This is a technically difficult surgical procedure but has a very good success rate and allows the oral surgeon to place implants long enough to withstand the bite forces generated in the back of the upper jaw. They must be accurately placed and of a large enough size to withstand the bite forces placed upon them.

Replacing Lower Front Teeth with Implants

    Replacing lower front teeth requires attention to aesthetics and detail. Adequate bone height and density are usually available. Problems placing implants in the front of the lower jaw surface because the bone width can be minimal and the space between the teeth is usually very small. Proper work-up with a wax model is of paramount importance. Good x-rays and plaster casts of the teeth are necessary to evaluate the bite.

  
Surgical template fabricated to place the implant precisely in between the lower canine and central incisor

    Lower back teeth are very commonly replaced with implants(when the other teeth in the area are sound). Although every effort is made to replace the missing tooth with an implant that appears as natural as possible, the emphasis is, once again, on making the implant functional.

    Of primary concern is placing an implant restoration that can withstand the bite forces of the jaws. Fortunately, in the lower jaw, the bone is usually dense. Adequate thickness of the bone must be carefully evaluated since it is recommended that the larger diameter implant be placed in this region. Special x-rays called CT DentaScans are sometimes used to better delineate the thickness and height of bone. It is important to place the largest diameter and longest implant possible in this region. Compromise here may spell premature failure of the implant.

    Anyone who has experienced the embarrassment of loose fitting dental plates appreciates the options implant dentistry can provide. Replacing partial dental plates with implant supported teeth which are fixed and stable is more healthy for the remaining teeth and functionally a quantum leap for the patient. Dental implants can be used to anchor removable dental plates or can replace them altogether. Removable plates are designed to replace multiple missing teeth. In the past they have been the only option for the dentist. They must fit accurately. Ill-fitting partial dental plates can irritate the gum tissue and the jaw bone causing ulcerations. They can also cause bone loss and even lead to the premature loss of the teeth they are fastened to.

    Replacing the partial dental plate with implants or supporting the partial dental plate with an implant can counteract the forces on the remaining natural teeth and protect the jaw and gum tissue from injury. Additionally, better comfort and function is achieved when the plate is fastened to the jaw or replaced entirely with dental implants.

    No other use of dental implants has such a profound impact upon function and quality of life as replacing a poor fitting, poor functioning full denture with teeth that are fixed to the jaws. The most appreciative patient is the one who can again smile with confidence, talk with confidence and chew with the function of an implant retained set of teeth.

    Replacing upper dentures with implants differs from replacing lower dentures with implants. Because the bone quality (and sometimes quantity) is less, implants in the upper jaw are not as predictable as implants in the lower jaw. Many times more implants are needed to support the denture. Although it is true that teeth can be made to fix directly to the implants, many times the teeth are made to look like a partial plate which snaps over a bar that is secured to the implants.

    This type of dental implant appliance gives excellent functional aesthetics and still allows the patient and the dentist to clean the implants. Sometimes additional acrylic is added to the appliance so that support can be obtained from the upper jaw itself. This helps to stabilize the implants in the bone and guards against overloading of the implants. Remember, the bone is not as dense in the upper jaw as it is in the lower jaw, so greater attention to diagnosis and treatment planning is needed. Additionally, patients must understand that implants in the upper jaw do not last as long as implants in the lower jaw. Additional attention to stability of the implant system is needed.

    No matter what type of denture or bridge is made, the function of the appliance is greatly improved. Long term aesthetics is also enhanced with implant supported dentures. It is a known fact that bone resorbs and jaws shrink after teeth are extracted. When teeth are replaced with implants, the bone is preserved. Over the patients lifetime this can significantly enhance their appearance. Preserving the bone prevents chin protrusion, lip shrinkage and sagging of the face around the mouth. Appliances fabricated to fit over the dental implants support the face and lips. They also help to improve chin position by increasing the vertical height of the face. More importantly, though, the implant supported denture vastly improves function and speech.

    Very successful dental implant appliances can be made to replace missing lower teeth. Many patients cannot tolerate lower dentures due to tongue movement and inadequate bony support. Some patients do not adapt well to lower plates. Some patients experience pain with their lower plate due to a poor fit and movement during chewing.
    Lower jaw implants are the most successful of all implants. Placed correctly, implants in the lower jaw may last 15 years or more and provide a stable foundation for complete lower dental plates or fixed bridges. Many times there is abundant bone in the lower jaw for the placement of implants. When this is the case as few as two implants can be used to secure the lower plate. Up to six implants can be placed to dramatically increase the fit of a lower dental plate or to replace the lower dental plate altogether with a fixed bridge. The fixed bridge screws into the dental implants and cannot be removed from the mouth. The options for the patients are many when adequate bone is available.
   Replacing missing lower teeth with implant supported appliances can be accomplished by several different treatment alternatives all of which offer advantages and disadvantages and all of which are tailored to meet the functional and cosmetic needs of the patient. In determining the best solution to the patient's prosthetic needs the clinician must take into consideration the presenting anatomy, opposing dentition, and functional requirements of the system being considered to replace the patients missing teeth.
    Treatment of the edentulous mandible can be classified into four possible different methods according to work done by Branemark and reported by the noted implantologist Hubertus Spiekermann M.D., D.D.S., Ph.D. in his Color Atlas of Dental Medicine entitled Implantology:

• Method 1: Removable, mucosa-borne complete denture, retained in the anterior mandible by 2 to 4 implants
• Method 2: Removable, mucosa-borne complete denture, retained in the anterior region on 3 to 5 implants
• Method 3: Removable, implant-borne prosthesis or bridge, retained and supported on 4 to 7 implants in the anterior mandible
• Method 4: Screw-retained (sometimes referred to as a "fixed or fastened" appliance) implant-borne bridge retained on 4 to 7 implants in the anterior mandible

    Today there are variations and hybrids of these four methods of treatment for missing lower teeth. Once again, the final treatment plan individualized to fit the patient's needs and presenting anatomy.

Case 1.

Method 4 was used to treat this patient who presented with lower teeth which could not be restored and saved. The teeth were removed and a fixed bridge fastened to the implants was fabricated.