Functional and Esthetic Considerations for Single-tooth Ankylos Implant-crowns: 8 Years of Clinical Performance
Problem: Following the loss of an anterior natural tooth, the mucogingival complex begins to collapse. The early placement of endosseous dental implants can prevent or reduce the extent of this collapse. If there is a long interval between the loss of the natural tooth and the placement of the implant prosthetic replacement, this collapse tends to increase significantly. Purpose: This paper will report on the clinical success of this implant product in the fabrication of esthetic, functional, and harmonious replacements for missing single, natural teeth for a period of 8 years. Method: A total of 275 single Ankylos implant tooth restorations in the anterior and posterior jaw regions were placed and monitored for 8 years. Of these, 264 implants were restored using the titanium Balance abutments, and only 11 were restored using ceramic abutments. The final restorations were either metal-ceramic or full-ceramic crowns and were cemented with glass ionomer cement. Results: The survival rate was 98.2%, with only 5 implants being lost during the healing phase. There were no other implant losses in the postloading period that averaged 3.2 years. To date, there have been no mechanical complications associated with the prosthetic components (ie, screw loosening, screw breaking, or crown breaking) for either the titanium or the ceramic abutments. Conclusions: Experience with the Ankylos system with single-tooth replacement indications may be considered positive with regard to the esthetic and functional results of the treatment. The lack of mechanical complications and problems with the hard and soft tissue in the loading phase of the implants suggests the functional safety of the tapered connection between implant and abutment.Abstract
The new Ankylos implant design. The innovative features of this implant include a progressive thread design, a surface that is slightly roughened, and a coronal portion that is machined and does not have threads; this directs the functional stresses away from the crestal bone and onto the trabecular bone. Trabecular bone is more resilient and resists damage due to repetitive microstains and, if damaged, repairs more rapidly than crestal bone
Precision-machined, internal-tapered abutment connection (Morse Taper) provides effective “anti-rotation” and eliminates micromovement during clinical function. The precise fit of this connection eliminates the microgap found in most 2-stage implant systems as well as food debris and bacteria that are often found in this microgap. Bacteria and micromovement are believed to be associated with crestal bone loss
Schematic drawing of the Ankylos implant and its relationship to the hard and soft supporting tissues. Note: The narrow tapered design of the implant abutment from the crown restoration to the integrated implant body—this allows a dense layer of soft tissue to form around the neck of the abutment. This dense tissue prevents food debris from accumulating in this region, and it eliminates the “gray discoloration” in the cervical region that is common with other abutment designs
(A) Surgical stent aids in the correct positioning of the implant. (B) The implant is placed slightly below the crestal bone level. (C) A sulcus former can be placed and used to support any augmentation materials. (D) A larger sulcus former is in place, following uncovering, to establish the emergence profile within the soft tissue. (E) “Balance Anterior Abutment.” The thin neck of the abutment and the preformed margin can be modified for custom crowns. (F) Customized balance abutment modified on laboratory cast so that final restoration provides a harmonious relationship with natural teeth. (G) Precise fit of crown on customized Balance abutment. (H) Relationship of customized abutment and crown to be transferred to mouth with customized transfer stent (key). Transfer stent is made of self-curing acrylic resin. (I) Balance abutment has been seated in implant. (J) The final esthetic crown is cemented to the customized Balance abutment. (K) Excessively wide space evident between natural right cuspid (tooth #6) and implant-supported crown (#7). (L) Adhesive composite material is applied to the mesial surface to eliminate the gap; note the natural esthetics and healthy tissue around restoration and the interdental papillae.
(A) Small sulcus former (incisal view). (B) Small sulcus former (frontal view). (C) Pressure shaping of emergence profile within soft tissue with large sulcus former: note blanching of tissue. (D) Shaping of tissue margin: note healthy tissue color. (E) Emergence profile formed within soft tissue: note that thick dense tissue covers the coronal portion (shoulder) of implant. (F) Healthy, well-formed soft tissue following removal of sulcus former. (G) Esthetic crown cemented on abutment. (H) Final esthetic crown closely follows the patient's “smile line.”
(A) Implant following uncovering: note sulcus former. (B) The soft tissues have been shaped to provide natural contours. (C) Ankylos implant with the Cercon ceramic abutment. (D) Cercon abutment has been customized on laboratory cast. (E) Cercon abutment with full-ceramic crown. (F) Esthetic ceramic crown: note the emergence profile from shoulder of implant analog. (G) Cercon abutment in place (tooth #8). (H) Cemented final crown. (I) Patient's high smile line: note healthy soft tissue around implant-crown restoration
(A) Implant restoration (tooth #8): note the healthy tissue and contours around implant restoration. (B) Implant restoration after 5 years of clinical function: note that there is no detectable loss of crestal bone surrounding implant restoration
(A) Bone response to mandibular posterior molar Ankylos implant-crown at time of uncovering. (B) Bone response, 2 years postinsertion of crown. (C) Bone response 7 years, postinsertion of crown. Crestal bone has remained at the same level at all stages of implant treatment
(cont.) (M) Lack of symmetry is evident on study cast. (N) Esthetic and functional restoration blends well with natural teeth. (O) A close-up view of implant restoration (tooth #7) demonstrating excellent esthetics. (P) Crestal bone level at time of insertion of final restoration. (Q) Crestal bone level after 2 years of clinical function: note that crestal bone level does not show any loss. (R) Crestal bone level after 4 years of clinical function: note that crestal bone level does not show any reduction in height
Contributor Notes
Katrin Döring, DMD, and Eduard Eisenmann, DMD, are at the Department of Restorative Dentistry and Michael Stiller, DMD, MD, is at the Clinic for Maxillofacial Surgery, Department of Oral Surgery, University Hospital Benjamin Franklin, Free University of Berlin, Assmanshauser Str. 4-6, 14197 Berlin, Germany