Abstract: Objective: To explore the effects of short implants on the displacement of implants and the stress and strain of bone tissue under insufficient bone mass in maxillary posterior region based on biomechanical analysis. Methods: A prospective trial was used. A total of 65 patients with missing maxillary posterior teeth who were admitted to our hospital from January 2016 to January 2021 were included as the research subjects. They were divided into research group (n=35) and control group (n=30) according to the bone mass at their implantation sites. Short implants were used for patients with mild osteopenia in the study group, while conventional implants were used for patients with adequate bone mass in the control group. The success rate, retention rate, implant displacement, bone resorption at the neck edge, and bone tissue stress and strain of the two implants in the two groups were compared five years later, and the incidence of complications after restoration was calculated. Results: The success rate and retention rate of implants in the study group were lower than those in the control group (P>0.05). There was no significant difference in the results of re-examination of bone resorption at the neck edge between two groups at different follow-up stages (P>0.05). The maximum displacement of the implant and the maximum stress of the cortical bone in the short implant model were lower than those in the long implant model, and the maximum stress of the cancellous bone was higher than that in the long implant model. The maximum displacement value of the implant, the maximum strain value of the cancellous bone, and the maximum stress value of the cortical bone will be decreased with the increase of the reduction ratio of the crown. The crowns of the patients in the two groups had no loose, collapse porcelain, and fall off during the follow-up period. There were no complications such as swelling of the implant neck membrane and no bone destruction around the implant. Conclusion: Short implants have the same curative effect as conventional implants, but short implants can reduce the difficulty of implant surgery in the posterior maxillary area to a certain extent. From the biomechanical point of view, proper reduction of crown diameter can promote the reduction of implant displacement and the change of stress value of bone tissue.

Key words: biomechanical properties, insufficient bone mass, short implants, implant displacement, bone tissue stress, strain