An innovative self‐tapping underprepared implant‐ in vivo histologic and histomorphometric analysis

Abstract

Background The bone site preparation plays a key role in osseointegration development because it allows to obtain an implant bone bed adequately adapted to the implant geometry thus ensuring sufficient primary implant stability without excessive bone compression. Surgical trauma and bone temperature raise during standard drilling procedures are other crucial factors. Recent studies showed improved healing and biomechanics by preserving the bone bulk using osseodensification drills. Aim/Hypothesis The working hypotheses of the present study is that a specifically designed self-tapping implant may be placeed in an extremely underprepared low-density trabecular bone site may achieve the same histologic and biomechanical results as a standard implant placed with adequate preparation. Material and Methods Two female sheep, 4–5 years old, were included in the study. After dissection of the soft tissues, iliac crests were exposed and five osteotomic sites were prepared in each (left and right) side. In the right side of each animal (test group) implant bone sites were prepared using only the pilot drill 1.8 mm in diameter. Ten Expander® 3.8 × 10 mm implants (NoDrill®, Milano, Italy) were inserted. In the left side of each animal (control group) implant bone sites were prepared using the following burs sequence- pilot drill 1.8 mm in diameter, twist drill 2.8 mm in diameter and the final drill 3.2 mm in diameter. Ten 3.8 × 10 mm Dynamix® implants (Cortex, Shlomi, Israel) were used. After 2 months of healing, biomechanical (micromotion under later forces (VAM), reverse torque (RT) and ISQ) and histomorphometrical data (BIC% and BV%) of test and control group were calculated and statistically compared by the T-test. Results No implant failure was recorded. The host bone density (basal %Bone Volume) measured 26.17% ± 2.35%. Implants in the test group showed a bone-to-implant contact percentage (%BIC) of 70.91% ± 7.95%, while control group implants showed a BIC value of 49.33% ± 10.73%. The peri-implant Bone Volume measured 41.83% ± 6.30% in test group and 29.61% ± 5.05% in control group. These parameters were statistically different between the two groups. The biomechanical analysis of secondary implant stability revealed a VAM value of 82.6 ± 23.27 μm in test group and 60.5 ± 16.58 μm in control group. The reverse torque (RT) was 98.2 ± 16.81 N cm in test group and 98.8 ± 24.40 N cm in control one. The condensation phenomenon characterized by a higher bone volume percentage around implant than in the neighboring areas, caused by implant threads geometry, was evident at low magnification. The preservation of the peri-implant bone bulk during drilling procedures resulted in high new bone apposition. Conclusion and Clinical Implications Results from the present study show that it is possible to insert a self-tapping implant using a single drill protocol in low density bone achieving a histologic and biomechanical integration comparable to the standard implants placed using standard drilling sequence. This innovative fixture geometry (coupled with minimum bone removal) was able to achieve higher osseointegration value than control group and to cause a bone corticalization around implant threads.