Dental implant designs and surgical techniques, healing times, and restorative procedures have continued to improve since Brand introduced titanium implants in the 1950s. Previous implant designs included the blade vents, subperiosteal, and transmandibular implants. Biomechanical issues presented a challenge, especially with multiple posterior implants. With the lack of predictability, these types of dental implants are no longer used. Most of the studies reported <50% success rate after 5 years, with pocket formations exceeding 6 mm and significant alveolar bone loss around the implants.2,29
In the mid-1970s Schroeder contributed to the success of endosseous implants. This type of implant was more predictable. The procedure included preparing a hole in the bone without overheating or traumatizing the tissues. This type of procedure achieved the implant-bone apposition needed for success, as long as micromovements at the interface of the implant and bone were prevented during early healing. Currently, most endosseous dental implants have a tapered or cylindrical, screw-type design.29,43 The components of dental implants include the abutment, screw, and restoration. The threaded implant design has been preferred due to primary stabilization and bone apposition. The use of tapered designs has been utilized for areas with less space between roots and in narrow anatomic regions and extraction sockets.29-44
Today, the majority of dental implants are made from commercially pure (CP) titanium or titanium alloys. Titanium continues to be used in dentistry because of its reactive metal properties where the implant oxidizes within nanoseconds when exposed to air. This oxide layer then becomes resistant to corrosion in its CP form. Dental implants are treated with a variety of surface characteristics that have been shown to produce a better result in the process of osseointegration46 (Figure 1). A recent systematic review in the Journal of Prosthetic Dentistry conducted by Oh et al found a significantly higher survival rate for rough-surfaced implants than smooth-surfaced dental implants (90% vs. 68.7%).56 Manufacturers use additive materials or chemicals, such as inorganic mineral coatings, biocoating with growth factors, fluoride, plasma spraying, and other particulates containing calcium-phosphates, carbonates, and sulfates.45,47 Additive surface modifications have been shown to produce better results than subtractive modifications, where dental implants have rougher surfaces.32 Disadvantages of subtractive processes include an increased ion leakage and increased adherence of macrophages resulting in subsequent bone resorption.29
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