2025 Volume 38 Issue 1 Pages 43-51
Purpose : This study aimed to investigate the influence of the cusp angle on the implant superstructure on the strain at the implant collar.
Materials and Methods : Experimental implants were fabricated from titanium with a diameter of 6 mm, which had been subjected to severe plastic deformation. The experimental implants were fixed perpendicular to the jig of a universal testing machine, and a superstructure with a cusp angle of 15° (denoted as C15) or 30° (denoted as C30) was attached to each implant. The strain was measured by applying a strain gauge to the tip of the collar on the apical side of the experimental implants and applying a load from 50 N to 800 N. After the strain measurements, the residual strain with no load and the deflection amount were read from the recording paper. The width of the connection gap was measured using a CT. Five specimens were used for each condition, and the measured values were tested by one-way analysis of variance (risk rate: 5％).
Results : The strain at 0.1％ was 250 N for C15 and 150 N for C30. The strain of C30 was about twice that of C15 at loads of 750 N and 800 N, with a significant difference (p＜0.001). The deflection up to 800 N was 0.76±0.05 mm for C15 and 1.43±0.10 mm for C30, showing a significant difference (p＜0.001). After the measurement, the residual strain of the collar section under no load was 0.03±0.01％ for C15 and 0.21±0.02％ for C30, indicating that the permanent deformation of C30 was larger than that of C15. The width of the gap at the connection of C15 after strain measurement was 16.4±4.7 µm and that of C30 was 38.2±3.8 µm, showing a significant difference (p＜0.001).
Conclusion : C30, with a large cusp angle, has a larger strain and gap than C15, suggesting a risk of biological and mechanical accident symptoms.
