I tried to collect the most important information’s about dental implants.
A dental implant is a “root” device, usually made of titanium, used in dentistry to support restorations that resemble a tooth or group of teeth to replace missing teeth. Virtually all dental implants placed today are root-form endosseous implants, i.e., they appear similar to an actual tooth root (and thus possess a “root-form”) and are placed within the bone (endo- being the Greek prefix for “in” and osseous referring to “bone”). The bone of the jaw accepts and osseointegrates with the titanium post. Osseointegration refers to the fusion of the implant surface with the surrounding bone. Dental implants will fuse with bone, however they lack the periodontal ligament, so they will feel slightly different than natural teeth during chewing. Prior to the advent of root-form endosseous implants, most implants were either blade endosseous implants, in that the shape of the metal piece placed within the bone resembled a flat blade, or subperiosteal implants, in which a framework was constructed to lie upon and was attached with screws to the exposed bone of the jaws. Dental implants can be used to support a number of dental prostheses, including crowns, implant-supported bridges or dentures. They can also be used as anchorage for orthodontic tooth movement. The use of dental implants permits undirectional tooth movement without reciprocal action.
Prior to commencement of surgery, careful and detailed planning is required to identify vital structures such as the inferior alveolar nerve or the sinus, as well as the shape and dimensions of the bone to properly orient the implants for the most predictable outcome. Two-dimensional radiographs, such as orthopantomographs or periapicals are often taken prior to the surgery. Sometimes, a CT scan will also be obtained. Specialized 3D CAD/CAM computer programs may be used to plan the case.
Whether CT-guided or manual, a ‘stent’ may sometimes be used to facilitate the placement of implants. A surgical stent is an acrylic wafer that fits over either the teeth, the bone surface or the mucosa (when all the teeth are missing) with pre-drilled holes to show the position and angle of the implants to be placed. The surgical stent may be produced using stereolithography following computerized planning of a case from the CT scan. CT guided surgery may double the cost compared to more commonly accepted approaches. In its most basic form, the placement of an implant requires a preparation into the bone using either hand osteotomes or precision drills with highly regulated speedto prevent burning or pressure necrosis of the bone. After a variable amount of time to allow the bone to grow on to the surface of the implant (osseointegration), a crown or crowns can be placed on the implant. Unlike conventional dental implants, Mini dental implants may be loaded immediately and still have a high survival rate (94%). The amount of time required to place an implant will vary depending on the experience of the practitioner, the quality and quantity of the bone and the difficulty of the individual situation.
At edentulous (without teeth) jaw sites, a pilot hole is bored into the recipient bone, taking care to avoid the vital structures (in particular the inferior alveolar nerve or IAN and the mental foramen within the mandible). Drilling into jawbone usually occurs in several separate steps. The pilot hole is expanded by using progressively wider drills (typically between three and seven successive drilling steps, depending on implant width and length). Care is taken not to damage the osteoblast or bone cells by overheating. A cooling saline or water spray keeps the temperature of the bone to below 47 degrees Celsius (approximately 117 degrees Fahrenheit). The implant screw can be self-tapping, and is screwed into place at a precise torque so as not to overload the surrounding bone (overloaded bone can die, a condition called osteonecrosis, which may lead to failure of the implant to fully integrate or bond with the jawbone). Typically in most implant systems, the osteotomy or drilled hole is about 1mm deeper than the implant being placed, due to the shape of the drill tip. Surgeons must take the added length into consideration when drilling in the vicinity of vital structures. Traditionally, an incision is made over the crest of the site where the implant is to be placed. This is referred to as a ‘flap’. Some systems allow for ‘flapless’ surgery where a piece of mucosa is punched-out from over the implant site. Proponents of ‘flapless’ surgery believe that it decreases recovery time while its detractors believe it increases complication rates because the edge of bone cannot be visualized. Because of these visualization problems flapless surgery is often carried out using a surgical guide constructed following computerized 3D planning of a pre-operative CT scan.