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BIOMECHANICAL ANALYSIS OF SMALL DIAMETERAND SHORT DENTAL IMPLANTS

Christoph Bourauel (1), Maria Aitlahrach (1), Ludger Keilig (1),Susanne Reimann (1), Friedhelm Heinemann (2), Istabrak Hasan (1)

1. Department of Prosthetic Dentistry, Preclinical Education and Material Science,

Oral Technology, University of Bonn, Germany;2. Dep. of Prosthodontics, University of Greifswald, Germany.

Introduction

In recent years, Mini and Short dental implantsbecame more and more popular as treatmentalternatives in clinical cases with critical bonysituations. So-called Minis have a reduceddiameter of about 2.5 mm and are designed to beinserted in the anterior region of the maxilla or

mandible. Extremely short implants, called Shor-

ties, have a length of 5 to 7 mm and are commonlyused in the posterior region after severe boneatrophy. A profound scientific analysis of themechanical and biomechanical impact of thereduced diameter and length of these implants hasnot been published yet. A combined experimentaland numerical study was performed in order to

determine whether ultimate dimensions withrespect to length and diameter can be defined fordental implants.

Methods

21 commercially available mini (13) and short (8)

implants have been analysed with respect tomaterial behaviour and load transfer to the alveolarbone using a specialised biomechanical set-up[Keilig, 2004] and finite element (FE) analysis. Theimplants were inserted into bovine rib segments andloaded with forces up to 100N.Following CT scanning and geometry

reconstruction, FE models of Minis and Shortieshave been inserted in idealised bone segments.

Minis were analysed in the anterior mandibular jawregion at a force of 150N under immediate loadingconditions using the contact analysis option in

MSC.Marc/Mentat. Shorties were inserted inposterior bone segments and analysed in the osseo-integrated state at an occlusal force of 300N.Force/deflection characteristics of the experimental

specimens were compared with the results of theFE simulations. Load transfer to the bone, i.e.

stresses in the cortical and strains in the cancellousbone, as well as von Mises stresses in the implantswere analysed to characterise the implantbiomechanical behaviour.

Results

Measured implant deflections of 0.5 mm (Minis) upto 1.2 (Shorties) at the implant abutment have beenregistered. These extreme deflections are either dueto the reduced diameter of the Mini implants or to

the extremely long abutment of the Shorties. Agood correlation could be determined between

calculated and measured implant deflections.High von Mises stresses of up to 1,150MPa arecombined with these deflections in the Miniimplants (Figure 1). These partly exceeded theultimate strength of the material (titanium Grade 4or 5). Implant diameter and geometry had a pro-

nounced effect on stresses in the cortical plate (upto 266MPa). Strains in spongy and stresses incortical bone around Short implants increasedmarkedly compared to standard implants.

DiscussionAn increased risk of bone damage or implantfailure may be assumed in critical clinical situationswhen using Mini or Short dental implants. Clinicalapplication of especially Short implants shall be

reconsidered. Controlled, long-term clinical studiesare essential to prove the clinical success rates of

Minis and Shorties.

References

Keilig et al, Biomed Tech, 49:208-215, 2004.

Figure 1: von Mises stress distribution of selectedMini implants. Obviously, the ultimate strength isexceeded in most cases.

S178 Presentation 1543 Topic 15. Dental biomechanics

Journal of Biomechanics 45(S1) ESB2012: 18th Congress of the European Society of Biomechanics