Underprepared sites and primary stability

The primary aim of this study was to compare the impact of two different drilling methods on primary stability of implants inserted in three different polyurethane blocks. The secondary aim was to analyse the indications provided by pIT, RFA, and ILP when evaluating the same implant insertions.
The study was performed on 2 artificial bone blocks of solid rigid polyurethane without cortical layer with densities of 0.32 g/cc and 0.16 g/cc, respectively simulating D3 and D4 bone densities, and one block with density of 0.24g/cc laminated on one side with 2mm solid foam of 0.64g/cc simulating D2 bone density. For the experiment a total of 48 implants with 3.5mm of diameter and 9.5mm of length were used . For each polyurethane block, 8 implants were inserted following a regular drilling protocol (RDP) that contemplates the use of a 2mm diameter twist drill, followed by a Tri-Spade 2.9mm diameter drill for the site preparation. Another 8 implants were inserted following an adapted drilling protocol (ADP) that contemplates the use of a 2mm diameter twist drill, followed by a Tri-Spade 2.4mm diameter drill. Implant sites were prepared without irrigation and synthetic bone chips were removed with compressed air prior to implant insertion. The implants were placed 1.5mm below the polyurethane block surface, at least 20mm from the edge of the blocks and between each other; furthermore, in absence of a randomization, the same placement sequence was used for each block: first the 8 RPS implants, then the 8EPS implants. Immediately after implant placement, Immediate Loading Probability (ILP) indication of immediate loading feasibility, expressed as percentage, and peak insertion torque (pIT) expressed in Ncm were documented. Finally, Resonance Frequency Analysis (RFA) values expressed in Implant Stability Quotient (ISQ) were recorded with the average of two measurements performed with the probe in two perpendicular directions.In order to analyse the measurement methods outputs, the values recorded were grouped as suitable (specifically AIT > 65%; pIT > 25 Ncm, RFA>65 ISQ) or not suitable (specifically AIT < 65%; pIT < 25 Ncm, RFA<65 ISQ) for immediate loading of a single crown by bone density and drilling protocol.