Effects of Drilling Technology on Mini-Implant Primary Stability: A Comparison of the Mechanical Drilling and Femtosecond Laser Ablation

Objectives: Primary stability is a fundamental prerequisite in predicting the prognosis of a mini-implant (MI) as a skeletal anchorage. This study aims to evaluate the influence of implant site preparation technology on the primary stability of MI.Methods: A total of 108 bovine cortical bone samples were fabricated to three thicknesses (0.5, 1.0, and 1.5 mm). For each thickness group, the samples were divided into three subgroups: I (without site preparation), II (site preparation with a mechanical drill), and III (site preparation with femtosecond laser ablation). After MI insertion into these samples, the pull out strength of MI was measured by lateral pull out tests.Results: For the 0.5 mm thickness samples, the lateral pull-out strength was 9.9 +/- 2.7 N in subgroup I, 6.7 +/- 2.1 N in subgroup II, and 15.2 +/- 2.6 N in subgroup III. For the 1.0 mm thickness samples, the lateral pull-out strength was 39.3 +/- 2.5N in subgroup I, 38.2 +/- 2.7N in subgroup II, and 46.3 +/- 1.7 N in subgroup III. For the 1.5 mm thickness samples, the lateral pull-out strength was 73.9 +/- 4.8 N in subgroup I, 70.1 +/- 2.8 N in subgroup II, 75.0 +/- 2.2 N in subgroup III. No signs of carbonization or substantial cracking were visible in any of the bone samples.Conclusion: Site preparation with laser ablation significantly improved the lateral pull-out strength over mechanical preparation and control (no site preparation) in thinner cortical bone samples (1.0 and 0.5 mm). Such improvement in lateral pull-out strength decreases as the samples become thicker and diminishes in thick (1.5 mm) cortical bone samples.

Automated summary

The study suggests that using femtosecond laser ablation for implant site preparation can significantly improve the lateral pull-out strength of mini-implants in thinner cortical bone samples (1.0 and 0.5 mm).