All oral implant systems rely on the abutment part of the implant to provide stability for the dental prosthetic. The concial cone connection of the Ankylos implant offers precisely machined, tapered-cone abutment (Morse taper) connection. This tapered abutment connection provides high resistance to bending and rotational torque during clinical function, which significantly reduces the possibilities of screw fracture or loosening. This increased stability of the abutment/implant interface is critical in the stability of the hard and soft tissues and thereby providing predictability with esthetics.
The loss of a natural tooth is often followed by the collapse of the hard and soft tissues that make up the mucogingival complex. This results in hard and soft tissue relationships that are rarely favourable for the insertion of a single-implant restoration. The esthetics associated with the final implant restoration are greatly affected by both the shrinkage of the adjacent interdental papillae and the loss of the scalloped tissue contour around the implant restoration. These structures are very important to the esthetics of the final restoration because of the visibility of the mucogingival complex during a full smile. The shape, color, and surface structure of any replacement for missing natural teeth must be optimal. The extensive loss of supporting tissue contours may require grafting of the hard and/or soft tissue in order to achieve a restoration that is symmetric and harmonious with its neighbouring teeth and the contralateral tooth. The definition for success differs from the patients to the clinician perspective. The patient is primarily concerned with that which is most apparent: the function of the final restoration and the appearance of the prosthesis, especially if it is in the anterior esthetic zone. The clinican, while also concerned about these two issues, also weighs concerns regarding:1 The biology of the immediate surrounding tissues (no loss of hard or soft tissues).2 Mechanical stability of the implant and abutment unit, providing long term security against fracture or other problems. And3 The ability of the patient to maintain cleanliness (hygienic) around the restoration. The ultimate goal in all implant dentistry is to satisfy all the criteria of both the patient and the clinician. It is with this in mind that the Ankylos system was developed, with the conical cone connection being the cornerstone of this philosophically different implant system.
The conical cone connection is the design feature which singularly makes the Ankylos implant unique. The Ankylos implant system has a unique transition from the implant body to the prosthetic abutment. The cross section of the abutment is smaller than the width of the top of the implant because of the tapered implant abutment connection, this feature is often referred to as a Platform Switch. (Figure 1). The conical male component of the abutment is attached to the female (internal cone matrix) by a central screw (a Woodruff screw), thus achieving precise mating of the surfaces within the tapered connection. The Morse taper, a precise 4 taper of the cone produces a considerable amount of frictional retention between the tapered abutment and the implant. This friction is more than adequate to provide antirotation properties for the abutment during clinical use. The abutment fixation screw, which is the generally the weakest component of other implant systems, is completely protected against overloading. If horizontal forces are transferred over absolutely form-fitting joint surfaces of this precision-tapered conical abutment connection, any strain on the central running fixation screw is eliminated. In engineering, the conical connection is among the most preferred connections for applications requiring the transfer of high transverse forces. The Ankylos implant capitalizes on conical technology to maximize the advantages of this new implant design over the more conventional implant abutment designs. These advantages include1 the precision-machined conical taper connection of the implant abutment joint produces a high level of mechanical stability under all clinical loading conditions that involve nonaxial loads applied to the abutment1;2 horizontal bending forces are evenly distributed over the entire abutment connection;2 and3 the strain on the central fixation screw is significantly reduced when the implant-abutment is loaded3 .
The following points must be carefully considered in order to achieve maximum esthetics and function for single-implant tooth restorations:1 every case must be precisely diagnosed and the treatment procedures planned;2 tissue deficits must be analyzed before placement of the implant, and these deficits must be satisfactorily corrected-using hard or soft tissue grafts, if necessary;3 the implant must be inserted in the correct position to allow the fabrication of an esthetic and functional single tooth implant restoration;4 the implant components must be mechanically stable and biocompatible; and5 the abutment must be anatomically shaped to allow for each specific clinical situation (anterior versus posterior positioning and cross sectional diameter of the tooth being replaced) so that a natural emergence profile for the crown can be formed within the peri-implant soft tissue.
The spatial position of an implant is determined by the angulation, inclination, and depth (Three-Dimensional Placement) that the implant is placed in the crestal bone when compared with the adjacent natural teeth. Vertically, the Ankylos implant must be positioned with reference to system-specific requirements of the internal tapered connection between the implant and the abutment. Because the emergence area of the shoulder region of the Ankylos implant is considerably less than that in other implant systems that use conventional implant-abutment connections, the shoulder is positioned 1.5 to 2 mm deeper into the bone to produce an optimal emergence profile. This subcrestal positioning (Figure 2) is contrary to the definitive positioning in all other implant systems which are recommended to be either crestal or supra crestal at the shoulder of the implant body. The crestal bone in the region of the implant shoulder generally remains in place during the functional loading phase (Figure 3) or may even increase in density, as confirmed by various reproducible X-ray exposures. Therefore, the Ankylos implant can be set slightly deeper into the bone, or bone can be grafted above the level of the implant shoulder to achieve an esthetically favourable emergence profile. (Figures 4-14)
Experience with the concial cone connection and 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. OH
Dr. E. Dwayne Karateew, Dip. Periodontics, Dip. Prosthodontics, maintains a high-end boutique-style solo practice in Vancouver, Canada concentrating on implant-assisted dental rehabilitation and aesthetics. He is a contributing consultant to Oral Health.
Oral Health welcomes this original article
1. The influence of implant diameter and length on stress distribution of osseointegrated implants related to crestal bone geometry: A threedimensional finite element analysis. Baggi L., et al. Prosthet Dent 2008;100:422-431.
2. New prosthetic restorative features of the Ankylos Implant system. Wigel, Paul. J Oral Imp 2004; Vol 30 No 3: 178-188.
3. Influence of Implant/Abutment Joint Designs on Abutment Screw Loosening in a Dental Implant System. Kitagawa T. et al. J Biomed Mater Res Part B: Appl
Biomater 75B: 457-463, 2005.
4. Histologic and Histomorphic Evaluation of Peri-Implant Bone Subjected to Immediate Loading: An Experimental Study with Macaca Fascicularis. Romanos and Toh et al. IJOMI 2002; 17:44-51
@ARTICLECATEGORY:587;
