The jaws are composed of alveolar bone which supports the teeth and the cortical bone that lies below. The alveolar bone’s sole purpose is to support teeth. When the teeth are lost the alveolar bone shrinks (resorbs) leaving less support to stabilize a denture. Studies have shown that patients can lose 5mm of bone during the first few years. After the tooth is lost and this continues throughout the remaining years.
As individuals, we all resorb at different rates and some patients may suffer severe bone atrophy leaving a flat ridge that is unable to retain a denture without it floating. Then, the maxillary sinus enlarges as we age and this may create a paper thin bone in the upper jaw. Osseous (bone) grafting can be used to raise the floor of the sinus and create adequate support to place root form implants. In the lower jaw as the bone resorbs, the inferior alveolar nerve (a large nerve running through the mandible) may interfere with implant placement. To circumvent this problem, the inferior alveolar nerve can be repositioned to allow implant placement.
Implants are constructed of titanium or titanium alloy. Extensive studies have demonstrated that titanium is completely biocompatible, causes no allergic reactions and is completely accepted by the body. During the fabrication of the implant, an oxide layer forms on the titanium surface upon which the bone will fuse (Osseointegrate). Additionally, the surface of the titanium can be treated with hydroxyappatite or sprayed with titanium (TPS) to improve the osseointegration.
Dental implants are divided in two categories based on whether they are placed within the bone (Endosseous) or on top of the bone (Subperiosteal).
Endosseous implants are placed within the bone and are subdivided into two groups, root form and blade form. These types of implants are placed to secure either single crowns, fixed bridges or to retain removable prosthesis (dentures).
Root form implants are cylindrical in shape and are available in various widths (3.2mm to 7mm) and lengths (10mm to 18mm) to accommodate varying amounts of available bone. This type of implant requires adequate width as well as depth of bone to provide a secure foundation. This implant form has been used in its current Instruments form since 1970 for treatment of edentulous jaws. Variations of the root form design date back into the late 1800’s with clinical success. Blade form implants, also known as plate form, are flatter in appearance and are utilized when there is insufficient width of bone but adequate depth is present. They are available in various shapes to fit in and around anatomical structures such as the maxillary sinus and inferior alveolar nerve. Blade implants have been used to treat edentulous jaws since 1960.