Influence of thread pitch, helix angle, and compactness on micromotion of immediately loaded implants in three types of bone quality: a three-dimensional finite element analysis.

Pan Ma,Weihong Li,Baosheng Tan,Wei Xiong,Dehua Li,Jiaqiang Liu,Wei Geng

doi:10.1155/2014/983103

Abstract

This study investigated the influence of thread pitch, helix angle, and compactness on micromotion in immediately loaded implants in bone of varying density (D2, D3, and D4). Five models of the three-dimensional finite element (0.8 mm pitch, 1.6 mm pitch, 2.4 mm pitch, double-threaded, and triple-threaded implants) in three types of bone were created using Pro/E, Hypermesh, and ABAQUS software. The study had three groups: Group 1, different pitches (Pitch Group); Group 2, same compactness but different helix angles (Angle Group); and Group 3, same helix angle but different compactness (Compact Group). Implant micromotion was assessed as the comprehensive relative displacement. We found that vertical relative displacement was affected by thread pitch, helix angle, and compactness. Under vertical loading, displacement was positively correlated with thread pitch and helix angle but negatively with compactness. Under horizontal loading in D2, the influence of pitch, helix angle, and compactness on implant stability was limited; however, in D3 and D4, the influence of pitch, helix angle, and compactness on implant stability is increased. The additional evidence was provided that trabecular bone density has less effect on implant micromotion than cortical bone thickness. Bone type amplifies the influence of thread pattern on displacement.

Highlights

In the conventional protocol for implant-based dental repair, an undisturbed 3- to 6-month healing period is suggested for successful implant osseointegration [1,2,3]
The resonance frequency analysis (RFA) method has been adopted in previous micromotion research [24, 25], which obtains an RFA value, which is sensitive to changes in bone type and reflects micromotion changes indirectly
These results suggest that the influence of thread pitch, helix angle, and compactness on implant stability is limited in D2 but that, in D3, which had a reduction in the thickness of the cortical bone, the influence of thread pattern on implant stability was increased under horizontal load

Summary

Introduction

In the conventional protocol for implant-based dental repair, an undisturbed 3- to 6-month healing period is suggested for successful implant osseointegration [1,2,3] This approach has been shown to be highly predictable and successful, the extended treatment period may be perceived as a considerable inconvenience. Studies have found that the survival rate of immediately loaded implants is acceptable [5, 6], for single-tooth restorations, an immediately loaded implant is still considered to have a higher risk of failure and a lower success rate [7, 8] These drawbacks might be due to increased micromovement at the bone-implant interface (BII), which leads to fibrous encapsulation around the implant rather than full

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Discussion

Conclusion