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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.

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Dental Instruments
The other main category of implant type are Subperiosteal implants, which lie on top of the bone below the gum tissue and have posts that project through the gun tissue into the oral cavity. These are custom fabricated implants that are made from an impression of the patients jaw bone. Ball attachments or other retaining devices are placed on the posts that project through the gum tissue and are used to retain a removable prosthesis (denture). Subperiosteal implants are utilized when insufficient bone is present to accommodate either a root form or a blade implant and anatomical structures limit endosseous implant placement.

An alternative treatment for the severely resorbed mandible is the ramus frame implant. This is a cross between a subperiosteal and a plate form implant and is designed to engage the posterior ramus bilaterally and the anterior symphysis when anatomic features permit placement. The ramus frame implant is a prefabricated implant that is bent to fit the mandible. The portion shown that has openings is within the bone and a bar secures the denture. This implant has been used in treatment of the resorbed mandible since 1970 and has shown long term success.

Types of human bone
There are four types of bone in the human face and the length of treatment for placing and restoring implants with a “Tooth” and crown depends on which type of bone the implant is placed in. Implants have to integrate with the surrounding bone before a tooth and crown is placed on it.four types of bone in the human face

Four types of bone in the human face
• Type I bone is comparable to oak wood, which is very hard and dense. This type of bone has less blood supply than all of the rest of the types of bone. The blood supply is required for the bone to harden or calcify the bone next to the implant. Therefore, it takes approximately 5 months for this type to integrate with an implant as opposed to 4 months for type II bone.
• Type II bone is comparable to pine wood, which isn’t as hard as type I. This type of bone usually takes 4 months to integrate with an implant.
• Type III bone is like balsa wood, which isn’t as dense as type II. Since the density isn’t as great as type II, it takes more time to “Fill in” and integrate with an implant. Six months time is suggested before loading an implant placed in this type of bone. Extended gradual loading of the implant can, however, improve the bone density.
• Type IV bone is comparable to styrofoam, which is the least dense of all of the bone types. This type takes the longest length of time to integrate with the implant after placement, which is usually 8 months. Additional implants should be placed to improve implant/bone loading distribution. Incremental loading of the implants over time will improve bone density. Bone grafting or augmentation of bone are often required.