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. 2025 Aug 6:13:1640122.
doi: 10.3389/fbioe.2025.1640122. eCollection 2025.

Effects of sandblasting and acid etching on the surface properties of additively manufactured and machined titanium and their consequences for osteoblast adhesion under different storage conditions

Affiliations

Effects of sandblasting and acid etching on the surface properties of additively manufactured and machined titanium and their consequences for osteoblast adhesion under different storage conditions

Osman Akbas et al. Front Bioeng Biotechnol. .

Abstract

Introduction: Additive manufacturing (AM) enables the production of complex, patient-specific titanium implants. However, the as-built surfaces of AM parts often require postprocessing to enhance surface properties for optimal osseointegration.

Methods: This study investigates the effects of varying sandblasting pressures (2 bar vs. 6 bar) and subsequent acid etching (SAE) on the surface properties of additively manufactured and machined titanium (Ti-6Al-4V and commercially pure titanium (cp-Ti), respectively). While changes in surface roughness and morphology were assessed at different process stages using optical profilometry and scanning electron microscopy, the analyses of surface wettability (contact angle measurement) were focused on effects after SAE and during different storage conditions (ambient air vs. NaCl). The resulting differences in material properties were then evaluated for their biological impact on osteoblast compatibility. For this purpose, the parameters cell adhesion, morphology, and membrane integrity were investigated using confocal laser microscopy and LDH assay.

Results: Initial high roughness of AM titanium surfaces was decreased by sandblasting, while initial smooth machined surfaces (MM) increased in roughness. Acid etching introduced characteristic irregular patterns on the surface with only marginal consequences for the resulting overall roughness. While all surfaces demonstrated high hydrophilicity directly after etching, storage under ambient air increased hydrophobicity over time, while NaCl storage preserved hydrophilicity and improved biocompatibility marginally. Osteoblast adhesion and morphology were optimal only under no storage condition, with uncompromised membrane integrity.

Discussion: Notably, the biological consequences observed for MM and AM titanium were rather similar, considering the differences in used materials, production techniques, and subsequent surface morphologies. Carefully applied SAE can also optimize the surface characteristics of additive manufactured titanium for an improved implant performance, with storage conditions critically influencing surface wettability and bioactivity.

Keywords: SAE; SLA; additive manufacturing; contact angle; cytocompatibility; dental implants; sandblasting and acid etching; surface wettability.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Macro image of (a) AM sample, (b) MM sample.
FIGURE 2
FIGURE 2
Surface morphology of AM surface (a) as-built state, (b) after sandblasting with 2 bar (SB2), with remnants of the initial spherical structures marked in red, (c) after sandblasting with 6 bar (SB6), (d) after SB2 and acid etching (AE), with embedded corundum artefacts marked in yellow and (e) after SB6 and AE, with embedded corundum artefacts marked in yellow.
FIGURE 3
FIGURE 3
Surface morphology of AM surface after SAE for (a) AM-SB2-AE, (b) AM-SB6-AE.
FIGURE 4
FIGURE 4
Surface morphology of the MM surface (a) as-machined, (b) after sandblasting with 2 bar (SB2), (c) after sandblasting with 6 bar (SB6), (c) after sandblasting with 2 bar and acid etching (SB2 and AE), with embedded corundum artefacts marked in yellow, and (e) after after sandblasting with 6 bar and acid etching (SB6 and AE), with embedded corundum artefacts marked in yellow.
FIGURE 5
FIGURE 5
Surface morphology of AM surface after SAE for (a) AM-SB2-AE, (b) AM-SB6-AE.
FIGURE 6
FIGURE 6
Development of the contact angle over 42 days of storage under ambient air conditions for AM-SB2-AE, AM-SB6-AE, MM-SB2-AE, and MM-SB6-AE. Representative data of mean values and error bars based on three measurements. The errors bars have been slightly shifted relative to the data points to reduce overlap, achieving a better visibility.
FIGURE 7
FIGURE 7
Primary osteoblast cell behavior on AM and MM titanium surfaces after SAE under different storage conditions (a) Representative CLSM images showing cell morphological changes in nuclei (blue) and actin (green) cytoskeleton organization. Scale bar 15 μm. (b) Bar graph displaying mean differences in cell adhesion. (c) Bar graph for loss in cell membrane integrity. Data is represented as mean ± SD. The results were statistically analyzed using two-way ANOVA with post-hoc analysis. P < 0.001 (***); P < 0.01; (**); P < 0.05 (*).

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