Resonance frequency analysis of implants placed with osteotome sinus floor elevation in posterior maxillae

To test the reliability and validity of implant stability quotient (ISQ) values used for assessment of the condition of bone-to-implant interface in the osteotome sinus floor elevation (OSFE) model and to evaluate the influence of residual bone height (RBH) on ISQ values.

Forty-six Straumann(®) tissue-level SLA implants (Φ4.8 mm*8 mm, wide neck, standard plus) placed in 39 patients applying OSFE without grafting were included in the study. Patients were assigned to three groups based on the RBH with one implant per patient randomly chosen: (1) 2 ≤ RBH < 4 mm (n = 14); (2) 4 ≤ RBH < 6 mm (n = 15); (3) 6 ≤ RBH < 8 mm (n = 10). ISQ values were determined with Osstell ISQ(®) at 0, 2, 4, 8, 12, 16, and 20 weeks postoperation. The reliability of RFA measurements was tested by the degree of dispersion of ISQ values at each time point, and the validity was tested by linear correlation between ISQ and RBH. ISQ values were then compared among groups at all observed time points.

The implants achieved a mean ISQ value of 63.6 immediately after surgery and reached a higher ISQ level of 70 after 20 weeks with a dip at 4 weeks. A higher degree of dispersion of ISQ values was observed immediately after surgery compared to the other time points. No significant correlations were found between RBH and ISQ values and no significant difference in ISQ values among groups at all the time points.

Within the limits of the study, it may be implied that ISQ values are not able to assess the condition of bone-to-implant interface and the role of single RFA measurement in determining loading protocol is questionable.