Effects of implant tilting and the loading direction on the displacement and micromotion of immediately loaded implants: an in vitro experiment and finite element analysis

Abstract

PurposeThe purpose of this study was to investigate the effects of implant tilting and the loading direction on the displacement and micromotion (relative displacement between the implant and bone) of immediately loaded implants by in vitro experiments and finite element analysis (FEA).MethodsSix artificial bone blocks were prepared. Six screw-type implants with a length of 10 mm and diameter of 4.3 mm were placed, with 3 positioned axially and 3 tilted. The tilted implants were 30° distally inclined to the axial implants. Vertical and mesiodistal oblique (45° angle) loads of 200 N were applied to the top of the abutment, and the abutment displacement was recorded. Nonlinear finite element models simulating the in vitro experiment were constructed, and the abutment displacement and micromotion were calculated. The data on the abutment displacement from in vitro experiments and FEA were compared, and the validity of the finite element model was evaluated.ResultsThe abutment displacement was greater under oblique loading than under axial loading and greater for the tilted implants than for the axial implants. The in vitro and FEA results showed satisfactory consistency. The maximum micromotion was 2.8- to 4.1-fold higher under oblique loading than under vertical loading. The maximum micromotion values in the axial and tilted implants were very close under vertical loading. However, in the tilted implant model, the maximum micromotion was 38.7% less than in the axial implant model under oblique loading. The relationship between abutment displacement and micromotion varied according to the loading direction (vertical or oblique) as well as the implant insertion angle (axial or tilted).ConclusionsTilted implants may have a lower maximum extent of micromotion than axial implants under mesiodistal oblique loading. The maximum micromotion values were strongly influenced by the loading direction. The maximum micromotion values did not reflect the abutment displacement values.

Micromotion analysis of different implant configuration, bone density, and crestal cortical bone thickness in immediately loaded mandibular full‐arch implant restorations: A nonlinear finite element study

“…We previously demonstrated that the maximum micromotion of axial and tilted implants was very similar under vertical loading in the single implant model. 19 However, the effect of tilting the distal implants on micromotion in multipleimplant restorations has been unclear. The present findings indicate that tilted implant may have similar effects on micromotion compared with axial implant in a multiple-implant prosthesis.…”

“…37 In this study, contact interfaces with friction were simulated in the similar manner as previously published reports. 7,[11][12][13]17,19 Because material properties also have an important influence on the outcome, 38 Young's modulus for low-density cancellous bone was defined from preoperative patient data. 29 Implant configuration had a limited effect on micromotion.…”

“…9,18,19 Of these factors, inadequate bone quantity and low bone density have been identified as increasing the risk for immediate loading of implants. 20 However, only single implants have been investigated in previous studies, so the influence of bone quantity and bone density on micromotion of multiple-implant restorations have not yet been clarified quantitatively.…”

“…The friction coefficient was set at 0.6. 19,31 The material properties of the model were set as homogeneous and isotropic with linear elasticity. The finite element model was constructed from 4-node tetrahedral elements and it incorporated approximately 814 000 elements and 161 000 nodes.…”

Principles of biomechanics in oral implantology

“…ISO 14801 (Dynamic loading test for endosseous dental implants) is currently the accepted standard for these tests, although it has severe limitations [6]. More and more authors suggest using Fine Element Analysis (FEA) as a substitute or in conjunction with the classical means of testing, as it can provide supplemental information and reduce testing time and costs [7,8]. Even the best results in laboratory testing and FEA cannot guarantee clinical success, if the basic biomechanical principles are not taken into consideration during insertion and loading.…”