The ADA Practical Guide to Dental Implants. J. Anthony von Fraunhofer. Читать онлайн. Newlib. NEWLIB.NET

Автор: J. Anthony von Fraunhofer
Издательство: John Wiley & Sons Limited
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Жанр произведения: Медицина
Год издания: 0
isbn: 9781119630685
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. 2.1. Consequently, masticatory and other stresses were transmitted directly to the supporting bone rather than to the oral mucosa as with conventional CDs. This approach enabled the surgeon to trim the basal bone of any projections or spicules of residual bone to ensure a good fit for the framework but also, incidentally, could help reduce or eliminate any painful sore spots for the final CD.

Schematic illustration of the subperiosteal implant.

      Although subperiosteal implants were effective, the overall procedure was lengthy and involved a great deal of discomfort for the patient and often were subject to various complications [8, 9]. Further, a high degree of surgical skill was required and necessitated a close collaboration between the surgeon, prosthodontist, and the laboratory technician to ensure optimal clinical results. Provided care was exercised in patient selection, there was good overlying soft tissue and no residual alveolar bone, the prognosis could be very good with reasonably high short‐term success rates.

       Endodontic Implants

      For many years, the most established and longest established implant was the endodontic endosseous pin implant, also known as the endodontic stabilizer, and was particularly useful for rigidly anchoring a mobile tooth to bone. Tooth mobility can have many causes, including an unfavorable crown‐to‐root ratio, gum and alveolar recession, bruxism and an unbalanced occlusion.

      The basis of this approach was that a pin was inserted through the root canal into the underlying bone such that it was anchored in bone but with upper end projecting into the mouth and upon which, a crown or RPD was fabricated [10].

      Typically, the lower end of the pin did not penetrate the cortical plate of the mandible or the antral or nasal floors of the maxilla. Indications for endodontic implants included treatment of root fractures, external or internal root resorption and when better support and stability was required for FPD or RPD abutments.

       Endosseous Implants

      Endosseous implants, also known as intra‐osseous and endosteal implants, have been in clinical use since the 1960s [12]. There are four main categories of endosseous implant, namely pins, spirals, blades, and screws. Regardless of implant design, endosseous implants are used in edentulous areas where there is sufficient healthy bone to accommodate the implant. Selection criteria for the use of implants are discussed in later chapters of this book.

      The first successful endosseous implants were the Formiggini spiral screw implant and, subsequently, the Cherchève spiral‐post implant, the former dating from 1947 and the latter from the 1960s to 1970 [4, 12]. The most sophisticated, and successful, Cherchève implant consisted of a double hollow spiral mounted on a square post. After the bone was trephined to create a cavity, the implant was placed beneath the alveolar ridge with the shank or post extending into the oral cavity and, upon which, the final prosthesis was constructed. The problem with these early implants was that trephining of the bone created a gap or space between the abutment post and the host hard and soft tissues, and this could sometimes present problems.

      Many workers developed modifications of the spiral implant during the late 1960s and early 1970s. These largely comprised self‐tapping screw implants, often with a vent or port below the threaded portion to permit fibrous tissues and, hopefully, bone to grow through the aperture and promote retention. Although many of these screw implants were successful, numerous failures occurred as the result of tissue irritation, frank infection and epithelial downgrowth preventing adequate retention and sometimes complete evulsion of the implant. Commonly, poor bony attachment to these implants caused stability to be a problem.

      The implanted tripodal system could then be used as a bridge abutment or to support a single‐unit prosthesis. Although pin implants had certain applications, they did not possess long‐term retention, generally were not self‐supporting and the pins often were easily displaced or removed over time.

Schematic illustration of tripodal pin concept.

      Clinically, bone often grew through the vents of the blade implants so that the early success rate was very high although the long‐term prognosis was lower, especially with maxillary placements. Various problems were associated with blade implants, particularly the difficulty in achieving an ideal gingival relationship with that crown when used to support a single crown. There were also problems with thin ridges such that any bony destruction could result in implant loss. Apparently, fewer problems were found with blades used to support a denture base although stability was a problem with unilateral mandibular free‐end saddles.

      The modern “screw” implant derives from the pioneering work of Stefano Tramonte [15] in Italy and Per‐Ingvar Brånemark in Sweden [16, 17], both of whom advocated the use of titanium for dental implants.