| Objective To analyze the stress of single crown supported by short implant and ultra-short implant in different bone types via using finite element modeling and to evaluate its clinical applicability.Methods Twelve groups of bone models were established, including two diameters (4.1 mm and 4.8 mm), three lengths (4 mm, 6 mm, 8 mm) and two bone types (typeⅡ and type Ⅲ). The crown of mandibular first molar was selected as the upper prosthesis, axial (152.8N), mesiodistal (31.2N), and buccal-lingual (22.8N) loads were applied to calculate the strain and stress of cortical and cancellous bone, and the displacement of implants. Results The maximum strain of cortical bone and cancellous bone decreased with the increase of diameter in typeⅡand typeⅢ bones, the strain of cortical bone decreased by 22% and 16% respectively, and the strain of cancellous bone both decreased by 14%. Strain of cortical bone decreased by 7% and 17%, while strain of cancellous bone decreased by 29% and 27%, respectively. In typeⅡbone, the maximum strain of cortical bone and cancellous bone was within the physiological limit. In typeⅢ bone, the maximum strain of cancellous bone was above the physiological limit except for group 4.8 mm×8 mm. Except for the 4.1 mm×4 mm group, the strain of cortical bone in other groups was within the physiological limit. There was a positive relationship between stress and strain in each model, and the total displacement of implant was lower than 50 μm. Conclusions When considering the stress in different bones of mandibular molars, short and ultra-short implants can be used in typeⅡ bone. In type Ⅲ bone, short implants should be carefully selected and measures to reduce bite force should be taken, and ultra-short implants should not be recommended. |
