Application of Ultrashort Implants in Posterior Maxilla With Insufficient Bone Height: A Finite Element Analysis

Implantation of the posterior maxilla with insufficient bone height faces challenges. Studies have shown that the use of ultrashort implants can avoid additional damage. This finite element analysis study aimed to evaluate the impacts of different lengths of ultrashort implants and three surgical approaches on stress, strain, and displacement in the posterior maxilla with varying bone heights. Twelve models of different lengths (3.0, 4.0, 5.0, and 6.0 mm) of ultrashort implants combined with unicortical fixation, bicortical fixation, and transalveolar sinus elevation were established, and conventional implants and short implants were considered as control models. Von Mises stresses within the implants and the sinus floor cortical bone, maximum and minimum principal stresses within the alveolar ridge cortical bone, and the maximum principal strain of the cancellous bone were determined using these models. Additionally, the displacement of the implants was analysed. Stress distribution range and peak values increased as implant length decreased. In the ultrashort implant group, H5L6 exhibited the smallest maximum and minimum principal stresses, 35.77 and 10.66 MPa, respectively. Among groups with different bone heights, 6 mm long implants presented the lowest maximum von Mises stress, whereas 3 mm long implants presented the highest. In the posterior maxilla with bone heights of 3, 4, and 5 mm, the stresses in different lengths of ultrashort implants and surrounding bone tissue were lower than the yield strengths in these areas, and the use of 6 mm-long ultrashort implants combined with osteotome sinus floor elevation can achieve lower stress distribution. This study provides important insights into the biomechanical properties of ultrashort implants combined with three different surgical procedures in severely atrophic maxilla. The 6-mm long implant combined with osteotome sinus floor elevation is most suitable for this area.