Editorial Type:
Article Category: Research Article
 | 
Online Publication Date: 01 Jun 2004

AICRG, Part I: A 6-Year Multicentered, Multidisciplinary Clinical Study of a New and Innovative Implant Design

DDS, MS,
PhD,
DDS, MPA,
DDS, and
DDS
Page Range: 125 – 133
DOI: 10.1563/1548-1336(2004)30<125:APIAYM>2.0.CO;2
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Abstract

Problem: Repetitive microstrains, which occur at the bone-implant interface during function, can lead to implant loss. In an attempt to improve survival by directing the stresses during function away from the dense cortical bone and toward the resilient trabecular bone, the Ankylos implant was developed with a roughened, progressive thread and a smooth cervical collar. The highly polished collar reduces the stresses in areas of the crestal bone. A precisely machined Morse taper prevents rotation of the abutment on the implant and eliminates the microgap present in many 2-stage implant systems. Clinical studies of other implants at different clinical research centers have demonstrated varying degrees of survival. Purpose: The purpose of this paper was (1) to assess the overall clinical survival of this new implant design and (2) to compare implant stability (ie, Periotest values [PTVs]) over time with other implants. Method: The investigation represented a comprehensive, multicentered, international clinical study conducted over a period of 6 years. It was conducted under an Investigational Device Exemption (IDE) protocol that was reviewed and accepted in the United States by the Food and Drug Administration (FDA). Over 1500 implants were placed and restored, and follow-up data were gathered for a period of up to 3 to 5 years. Results: Over 44% of the clinical research centers reported no failures (100% survival). A total of 63% of the centers had none or only 1 failure during the study. One center reported 6 failures in 1 patient, which were not related to the implant design. Overall survival for implants in function for 3 to 5 years was 97.5%. Using failure criteria of earlier studies of other implants, 5-year survival was 98.3%. Higher handpiece speeds were associated with an increase in the number of failures. This new design produced a slightly more resilient trabecular bone-implant complex with a difference of about 1 PTV in all bone densities when compared with other implants. Conclusions: The following conclusions can be made: (1) the implant design was effective under all clinical conditions; (2) no significant and unexpected complications or risk factors were evident; (3) survival was found to be excellent; and (4) this implant is well suited for use in the restoration of masticatory function and esthetics in patients with missing natural teeth.

Copyright: American Academy of Implant Dentistry
<sc>Figure</sc>
1.
Figure 1.

(A) Ankylos implant. Note roughened progressive threads and lack of threads at coronal portion of the implant. (B) Drawing of Ankylos implant in bone. Note the threads and the polished coronal portion of the implant. (C) Tapered abutment connection that virtually eliminates any abutment-implant gap for food debris and bacteria to collect in. (D and E) Clinical cases showing excellent results obtained with this implant


<sc>Figure</sc>
2.
Figure 2.

(A) Photoelastic stress analysis model of the basic implant design. Note the higher levels of stress at the coronal (crestal bone) portion of the implant. The stresses are generally evenly distributed along the entire length of the implant to both the crestal and trabecular bone. (B) Grit-blasted, progressive threads characteristic of this implant design. Each thread has a different size and pitch. (C) Photoelastic stress analysis model of an Ankylos implant design. Note the lower stress accumulation at the coronal portion of the implant adjacent to the crestal bone and the gradual increase is stresses toward the apical end. (D) Stability (Periotest values [PTVs]) of both another screw implant design (shown in yellow) and the Ankylos implant (shown in red). Since the implant is designed to engage flexible trabecular bone, there is about 1 PTV difference in each bone density for Quality-1 and Quality-2 bone. This difference becomes less as the bone density decreases


Contributor Notes

Harold F. Morris, DDS, MS, is codirector of the Dental Clinical Research Center (DCRC) and project codirector of the Ankylos Implant Clinical Research Group (AICRG), Department of Veterans Affairs Medical Center (VAMC), Ann Arbor, Mich. Correspondence should be addressed to Dr Morris at the DCRC (154), VA Medical Center, 2215 Fuller Road, Ann Arbor, MI 48105.

Shigeru Ochi, PhD, is codirector of the DCRC and project codirector of the AICRG, VAMC, Ann Arbor, Mich.

Patricia Crum, DDS, MPA, is chief of Dental Service in the VAMC, Ann Arbor, Mich.

Ira H. Orenstein, DDS, is a staff dentist in the VAMC, Bronx, NY.

Sheldon Winkler, DDS, is a professor in the Department of Restorative Dentistry, Temple University School of Dentistry, Philadelphia, Penn; and a senior executive editor for the Journal of Oral Implantology

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