The infl uence of thread geometry on biomechanical load transfer to bone: A fi nite element analysis comparing two implant thread designs

Manisha G Herekar, Viraj N Patil, Shahnawaz S Mulani, Megha Sethi, Omkar Padhye


Background: The success of dental implants depends on the manner in which stresses are
transferred to the surrounding bone. An important consideration is to design an implant with a
geometry that will minimize the peak bone stresses caused by standard loading. The aim of this
study was to assess the infl uence of implant thread geometry on biomechanical load transfer and
to compare the difference between two different thread designs.
Materials and Methods: A three-dimensional fi nite element model of D2 bone representing
mandibular premolar region was constructed. Two implants of differing thread geometries, 13-mm
length, and 4-mm diameter along with superstructures were simulated. One design featured fourfold
microthread of 0.4-mm pitch, 0.25-mm depth in the crestal one-third; 0.8-mm pitch, 0.5-mm depth
in the apical two-third. The other design had a single-pitch microthread of 0.8-mm pitch, 0.25-mm
depth in the crestal one-third; 0.8-mm pitch, 0.5-mm depth in the apical two-third. A static axial
load of 100-N was applied to the occlusal surface of the prosthesis. ANSYS CLASSIC 9.0 (PA,USA)
software was used for stress analysis as von Mises stresses.
Results: A comparison of von Mises stresses between two thread designs revealed that fourfold
microthread allows better stress distribution within the implant body by 43.85%, abutment by 15.68%, its
superstructure by 39.70% and 36.30% within cancellous bone as compared to single-pitch microthread.
The effective stress transfer to the cortical bone is lowered by 60.47% with single-pitch microthread.
Conclusion: Single-pitch microthread dissipates lesser stresses to cortical bone while the implant
body, abutment, and superstructure absorb more stress. This will have a positive infl uence on the boneimplant
contact and contribute to preservation of crestal bone. Implant with single pitch microthread
will thus be preferable to be used in areas where the amount of cortical bone available is less.
Key Words: Implant, implant design, microthreads, thread design, thread pitch

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