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International Poster Journal of Dentistry and Oral Medicine



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Int Poster J Dent Oral Med 6 (2004), No. 1     15. Mar. 2004

Int Poster J Dent Oral Med 2004, Vol 6 No 01, Poster 212

Bone Apposition under functional loading

Language: English

Dr. Helmut G. Steveling, Dr. Luis Gallardo Lopez, Dr. Armin Djamaseb,
Department of Oral and Maxillofacial Surgery Heidelberg University

Dezember, 4-7th, 2002
DGI Gemeinschaftstagung München
Arabella Sheraton Grand Hotel, München/Germany


Astra Tech Implants have been placed at the University of Heidelberg since 1992. The patients have been reexamined clinically and radiologically on a regular basis.
In the present clinical study the survival rate of enossal ASTRA TECH Implants as well as the bone situation after functional loading have been examined. The reexamined implants were inserted between 1992 and 2002 at the Clinic and Policlinic of Oral and Maxillofacial Surgery at the University of Heidelberg.

Material and Methods

A total of 258 patients (154 female and 104 male, age range 15 to 85 years) received 870 Astra Tech Implants and were annually examined. 455 implants were placed in the maxilla, 425 in the mandibula. After inserting the implants intraoral x-ray images of each patient were made in the right-angle technique. Further x-rays were made when the supraconstruction was placed, thereafter x-rays were made annually. Only x-ray images which clearly showed the outer thread were evaluated. All x-ray images were digitalized and evaluated by the program "Friacom Version 1.15" (standard deviation 0.1).
The change of the marginal bone level was calculated by measuring the difference between the reference point and the marginal bone ridge. The first implants were placed in June 1992. So we were able to observe the implants in situ for more than ten years.


According to the life-table analysis by Cutler-Ederer a survival rate of 97,8% results from this study.
We could make a division of all patients into 4 groups.

  • group 1 (31,5%) Patients showing no radiological change of the maginal bone level.
  • group 2 (15,9%) Patients showing isolated bone loss (-0,40 to -4,37mm) within the first and second year. Stability after the second year.
  • group 3 (10,5%) Patients showing isolated bone apposition.
  • group 4 (42,1%) Patients with a continuous change between bone loss and apposition.

Group 3 was the most surprising one, because these patients, after a bone loss within the the healing period of three months showed an increase of the marginal bone level after functional loading.
Some examples of this phenomenon are presented in the following pictures.

Case 1, female (33-35y)

Case 2, male (28-31y)

Case 3, female (16-22y)

Case 4, female (32-34y)

The Burn-out-effect (Case 4) shows the different x-ray behaviour of the fused aluminiumoxid ceramic step and the zirkonoxyd ceramic of the metal-free restoration.
Case 4, female (32-34y)

Case 5, female (71-73y)

Discussion and Conclusions

Although the thickness of the soft tissue has not been measured in many cases there is no marginal bone loss on the Astra Tech Implants in the sense of an establishment of the "biological width".
It is striking that the most part of the patients do not show any changes or, as demonstrated, apposition in the marginal bone.
At the moment we do not know the reason for this stable bone situation. A reason might be the design of the implant with the key features Conical SealIM TiOblastIM surface and Micro ThreadIM or the minimal-invasive surgical technique for the reentry and the installation of the self-finding abutments. We certainly should be able to find a clear answer to this question from animal experiments.


  • Norton, M., An in vitro Evaluation of the Strength of an Internal Conical Interface Compared to a Butt Joint Interface in Implant Desing, Clin Oral Impl Res 1997;8:260-298
  • Hansson, S., A Conical Implant-Abutment Interface at the level of the Marginal Bone Improves the Distribution of the Load into the Supporting Bone, Submitted for publication 2002
  • Hansson, S. et al., The relation Between Surface Roughness and Interfacial Shear Strength for Bone-Anchored Implants. A Mathematical Model, J Biomechanics 1999;32:829-836

This Poster was submitted by Dr. Helmut G. Steveling.

Correspondence address:
Dr. Helmut G. Steveling
Klinik und Poliklinik für Mund-, Kiefer- und Gesichtschirurgie
Department of Oral and Maxillofacial Surgery Heidelberg University
Im Neuenheimer Feld 400
69120 Heidelberg