Stress and Strain Distribution Patterns in Bone around Splinted Standard and Short Implants Placed at the Crestal Level and Subcrestally using Three- Dimensional Finite Element Analysis.

Abstract

Short implants can be used as alternatives to standard implants to prevent invasive surgical procedures. However, due to concerns about complications caused by less bone-implant contact area, researchers have focused on biomechanical properties of short implants and methods to promote them. Splinting has been suggested to decrease the limitation of short implants. This study compared the pattern of stress and strain distribution in bone supporting splinted standard and short implants positioned at crestal and subcrestal levels. An edentulous posterior mandible was made using computer-aided design. Five models of different combinations of splinted short (4 × 6 mm) and standard (4 × 10 mm) implants placed at the level of crestal bone or subcrestally mesial and distal to the edentulous region with a pontic between them were designed using the CATIA software program. ANSYS software was used for finite element analysis (FEA). In each model, 100 and 300 N loads at zero (parallel to the long axis of implants) and 30° angles were applied to implants. Maximum stress and strain for each of the five models, including equivalent stress, shear stress, and strain in peri-implant cortical and cancellous bone, were calculated and stress distribution pattern in different models were recorded. The highest stress was caused by the 300 N load applied at a 30° angle, followed by the 300 N load applied axially and the 100 N load applied at 30°. This order changed in model 1, where the highest stress was noted under the 300 N load at 30°, followed by the 100 N load at 30°. Maximum stress in peri-implant bone occurred under oblique (30°) load. Maximum stress was noted when two splinted short implants were placed subcrestally. In addition, stress in bone around crestal-level splinted short implants was lower than that around standard implants. Combination of short and standard implants had no biomechanical advantage. Application of load parallel to the long axis can significantly decrease stress in peri-implant bone. Although the combination of short and standard implants has no biomechanical advantage, crestal-level placement of splinted short implants is a suitable treatment plan.