ISQ as a Diagnostic Tool in Implants Affected with Bone Loss: An In Vitro Experimental Study

To determine the relationship between bone loss that occurs during the peri-implantitis process and variations in implant stability using resonance frequency analysis (RFA) measurement methods.

Forty selftapping implants were placed in cow ribs, and study scenarios were established according to the affected implant side and bone loss depth (n = 10 implants per group): Case 1 = bone loss on one side (vestibular); Case 2 = bone loss on two opposite sides (buccal and lingual); Case 3 = bone loss on two adjacent sides (buccal and mesial); and Case 4 = foursided bone loss (circumferential). For each group of 10 implants, first a bone loss of 0 mm was evaluated, then 4-mm defects (simulating 1/3 of bone loss) were created and evaluated, and finally 8-mm defects (simulating 2/3 of bone loss) were created and evaluated. Osteotomy measurements were made with a periodontal probe. For each implant, RFA was measured by the same operator using the Beacon system (Osstell).

The initial implant stability quotient (ISQ) values of the 40 implants exceeded 70, reflecting an average of 73 in the buccolingual (VL) and 74.8 in the mesiodistal (MD) directions. ISQ measurements in the 10 implants in which bone dehiscence was performed on the vestibular aspect reflected a decrease in ISQ values as bone loss increased. When generating bone loss in two opposite sides (buccal and lingual), a greater decrease in ISQ values was observed when 2/3 of the implant were affected. The average VL ISQ measurement was less than 70 when at sites with 2/3 of bone loss.

When bone loss occurs on only one side of the implant, the ISQ values decrease, but the implant maintains good stability. The same occurs when two opposite sides of the implant are affected, as the unaffected side has the least decrease in ISQ value.