Evaluation of Positional Variability in Surface Roughness in Orthodontic Mini-Implants Using Confocal Microscopy: A Multi-Manufacturer Comparative Study
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Alessandro Antonelli1,2, Till Augustinowitz1, Giulia Brunello1,3
1Department of Orthodontics and Dentofacial Orthopaedics, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Objective:
To compare the surface roughness of orthodontic mini-implants (OMIs) from seven manufacturers at standardized positions, since positional variability in OMI topography has not been systematically investigated but may influence healing and stability.
Materials And Methods:
Seven OMI systems (n = 5 per system, total n = 35) were analyzed using 3D confocal laser scanning microscopy. Four locations per OMI were assessed (apex, mid, top, neck). Roughness parameters included Sa and Sz (µm), Sdr (%), Str (dimensionless), and Spc (1/mm). Linear mixed-effects models were fitted for each parameter with Manufacturer and Location as fixed effects and Implant ID as a random intercept. Fixed effects were evaluated by Type III ANOVA; estimated marginal means (EMMs, 95% CIs) and Tukey-adjusted pairwise contrasts summarized differences.
Results:
Manufacturer, location, and their interaction were significant for all parameters (p < 0.0001). Dentaurum consistently showed the highest mean roughness values, especially at the neck, with an overall average value for Sa ≈ 0.81 µm compared to 0.20-0.39 µm for others, Sz ≈ 9.5 µm (others 2-3 µm), and Sdr ≈ 6%-7% (others ≤ 2%). The mean Spc at the neck reached ≈65,000 1/mm for Dentaurum, while OBS showed markedly lower mean values (< 10,000 1/mm). Ortholox Plus (TigerDental) showed intermediate increases at the neck, while OBS presented the smoothest surfaces, particularly at the neck. Str indicated manufacturer-specific isotropy: American Orthodontics and Forestadent demonstrated higher Str mean values (≈0.7-1.0) at the top and neck, whereas AbsoAnchor, Dentaurum, DualTop, OBS, and Ortholox Plus showed lower Str.
Conclusions:
OMI surface roughness is strongly manufacturer- and position-dependent, with the neck region amplifying inter-system differences. Selecting OMIs from the market or customizing their design based on anatomical considerations and applied forces may optimize osseointegration and peri-implant soft tissue health. Adjusting roughness profiles may help reduce implant migration. While long smooth necks might be advantageous in cases of extended transmucosal path.
