The Ankylos Implant System: Concept and Clinical Application
Problem: The Ankylos system was developed in 1985 and has been in clinical use since 1987. Some of its significant design features include (1) a progressive thread structure of the endosseous implant body for targeted load distribution to the apically positioned spongy bone; and (2) the gap-free subgingival tapered connection to the abutments. Purpose: The purpose of this report is to demonstrate that the Ankylos Implant System meets both the patients' and the dentists' standards of success and is suitable for use as single tooth replacements, bridge abutments, and retention elements for all regions and prosthetic indications. Method: The data from 5439 implants were evaluated between October 1991 and October 2002. The implants were considered successful if the following criteria were met: (1) clinical stability and function; (2) no inflammation of the peri-implant hard and soft tissue; (3) no progressive loss of the peri-implant bone; (4) no progressive loss of the peri-implant mucosa; and (5) satisfaction of the patient. All implants placed during this period were included in the evaluation as a prospective study. The average loading period was 56.8 months. Postoperative follow-ups were made once a year by a standardized protocol. The results were classified by prosthetic application in Table 1. A total of 943 implants were placed as single tooth restoration and were followed for the duration of the study. Results: The success rate for this type of restoration was 98.7%. For free-end implant restorations, there were 1679 implants placed with a 97.9% success rate. When the edentulous area involved a large gap, a total of 805 implants were placed with a 97.3% success rate. For cases involving reduced dentition, 606 implants were used with a 95.8% success rate. Another significant finding was that the success rates classified by maxilla and mandible showed no differences.Abstract
(A) Technical drawing of Anklyos implant. (B) Varying thread design on apical portion of implant. To reduce the stresses on the crestal bone during clinical function, no threads are machined on the cervial collar of the implant. (C) Photoelastic model of Anklyos implant showing only minimal stress concentrations in the area of crestal bone, with maximal stress concentrations shifted to the area of flexible trabecular bone. (D) Photoelastic model of convential screw implant design with similar stress for the entire length of the implant and at crestal bone. (E) Clinical case showing uncovered implant after removal of the sulcus former. Note the access to submerged implant fixture and the healthy emergence profile in the soft tissue. The top of the implant fixture is not visible but is covered by a dense layer of soft tissue. (F) Clinical case after insertion of the final crown. Note the excellent soft-tissue response in the cervical area
Ankylos implant that has been in clinical function for 56.8 months. Note the lack of (saucer shaped) bone loss around the implant in the area of the crestal bone. Note also that in this case the Ankylos implant is replacing a molar tooth and the bridge is attached to a natural tooth, without evidence of negative clinical complications. In response to clinical loading, a dense layer of bone is forming around the implant
(A) Photomicrograph showing the variations in the thread design and surface roughness (×50). FIGURE 3. (B) Photomicrograph of surface roughness of the Anklyos implant (×2000)
(A) Three different types of abutment connections for implants (from left to right): tapered connection, external hex, and internal hex. (B) Bone-spreading and -condensing instruments for preparing the implant site. (C) Clinical case showing the use of the instruments after the use of the pilot drill. (D) Clinical case after bone condensation with bone-spreading instruments. (E) Clinical case; placement of Ankylos implant. (F) Ankylos implant placed in poor-quality bone density in a monkey (healing stage). (G) Anklyos implant after progressive loading (bone training) and final loading of restoration in a monkey. Note the dense bone formation around the Anklyos implant
Precision fit of the tapered implant–abutment connection in the Anklyos implant. Note the lack of a gap between the implant fixture and the abutment, which is often found in other implant-abutment connections
Instruments used in the placement of the Anklyos implant (from left to right): round bur to prepare for the pilot drill, the pilot drill, enlarging the implant site to the depth and width required, reaming the bone to provide tapered-implant site, tapping the implant site, and the final insertion of the implant
(A) Clinical case; free-end saddle, 2 Anklyos implants replacing mandibular molars, prosthesis is attached at anterior end to natural teeth as abutments. Period of clinical function is 56.8 months, and bone is healthy. (B) Clinical case; single Ankylos implant replacing a mandibular molar. Period of clinical function is 56.8 months. Note excellent bone response around implant and lack of evidence of crestal bone loss. (C) Clinical case; 1 Anklyos implant is replacing a missing maxillary central incisor. Period of clinical function is 56.8 months. Note excellent bone response around implant and lack of crestal bone loss
Contributor Notes
Georg-H. Nentwig, DMD, is a professor in the Department for Oral Surgery and Implant Dentistry at the University of Frankfurt, D-60590 Frankfurt, Germany.