Influence of Diameter in the Stress Distribution of Extra-short Implants

Objectives: The use of extra-short dental implants (ESDI) with wide diameter (WD) could decrease the consequences of the higher crown-to-implant ratio (C/I) in rehabilitation of severely atrophic mandibular ridge. This study evaluated the influence of WD on stress distribution of ESDI as support for single implant-supported crowns in the posterior region of atrophic mandible, under axial (AL) and inclined load (IL).
Methods: Four models of an atrophic mandible rehabilitated with a single implant-retained crown in a C/I of 3:1 were created for finite element analysis. Two study factors were evaluated: implant diameter (ID) and load angulation. ID was represented either by Ø4mm or Ø6mm, both with 5mm length. The load (200N) either by AL or IL (30°). The Equivalent von Mises stress (σ_vM) was used for both abutment and implant evaluation, and minimum principal stress (σ_min) and shear stress (τ_max) was used for both cortical and cancellous bone.
Results: Overall, the IL increases the stress on all components studied compared to AL. Regardless of load direction, little effect is observed on the σ_vM on the abutment. On the other hand, the greater diameter decreases the σ_vM around 40% in both AL and IL. For the bone, the results showed different behavior in cortical and cancellous bone related to ID. For both AL and IL, Ø6mm exhibited better results for cancellous bone (decreased the σ_min in at least 45% and τ_max in 56%). However, in the cortical bone, the σ_min was at least 66% greater for Ø6mm than Ø4mm and the τ_max more than 100% greater. The use of ESDI with WD reduces the stress on the implant and cancellous bone, under AL and IL, but increases in the cortical bone.
Conclusions: Therefore, ESDI with WD may promote better mechanical behavior of the implant but should be used with caution in complex occlusal conditions.