Comparative Study of Acid Etching and SLA Surface Modification for Titanium Implants

Abstract

The dust generated during the sandblasting process of the sandblasted and acid-etched (SLA) method, commonly used to treat the surface of Ti dental implants, poses significant challenges in maintaining a clean manufacturing environment and ensuring safe working conditions. Nevertheless, surface modification remains crucial for improved performance of Ti dental implants. To address this problem and propose a clean and simple surface modification process to potentially replace SLA modification, this study aimed to characterize the surfaces of commercially pure Ti (cp-Ti) samples treated by acid etching and compare them with SLA-treated samples in terms of surface roughness (R_q), wettability (assessed through contact angle measurements), mineralized matrix deposition (evaluated through simulated body fluid [SBF] soaking), cell viability, cell differentiation (assessed based on alkaline phosphatase activity), and mineralization (assessed using MTT assay). Acid-etched surfaces exhibited nano- and micro-roughness and higher hydrophilicity than SLA surfaces, which is conducive to forming a highly bioactive TiO₂ surface. Moreover, acid-etched samples exhibited earlier hydroxyapatite deposition after SBF soaking than SLA samples. Furthermore, the acid-etched surfaces were nontoxic and displayed significantly higher cell viability and differentiation after seven days than SLA surfaces. These findings suggest that acid etching is a viable alternative to the SLA method, likely offering superior surface bioactivity and biocompatibility.

Keywords: cell adhesion; dental implants; osseointegration; surface-active agents; titanium.

Figure 1

Schematic of the experimental work carried out in this study. (a) Ti samples; (b) SLA surface; (c) surface obtained after first acid etching; (d) surfaces obtained after second acid etching for 10, 20, and 30 s. SLA, sandblasted and acid-etched; 1AE, single-acid-etched; DAE, double-acid-etched.

Figure 2

Atomic force microscopy three-dimensional semi-contact-mode topographic images of all sample groups. (Left) 100 µm² images and (right) 50 µm² images.

Figure 3

Roughness parameter R_q for all sample groups. # p < 0.05 vs. SLA; @ p < 0.05 vs. 1AE.

Figure 4

Scanning electron microscope images of the surfaces of the (a) SLA, (b) 1AE, (c) DAE-10, (d) DAE-20, and (e) DAE-30 samples.

Figure 5

SEM images of different regions of a Ti dental implant treated with the same protocol as that of DAE-30. (a) Upper region of the implant-screw thread with a 30× magnification, (b) 50,000× magnification, and (c) 100,000× magnification and (d) lower region of the implant-screw thread with 30× magnification, (e) 50,000× magnification, and (f) 100,000× magnification. SEM—scanning electron microscope.

Figure 6

EDS spectra of all sample groups at a 15 keV Cu Kα energy beam; (a) SLA, (b) 1AE, (c) DAE-10, (d) DAE-20, and (e) DAE-30 samples. EDS—energy-dispersive X-ray spectroscopy.

Figure 7

Contact angles based on the sessile water drop method for all sample groups.

Figure 8

SEM images of all sample groups after 3, 7, 14, 21, and 28 days of SBF soaking. White arrows indicate spots that suggest an initial formation of a hydroxyapatite layer. SBF—simulated body fluid.

Figure 9

X-ray diffractograms of all sample groups after different periods of soaking. (a) 3 days, (b) 7 days, (c) 14 days, (d) 21 days, and (e) 28 days. (I) SLA, (II) 1AE, (III) DAE-10, (IV) DAE-20, and (V) DAE-30.

Figure 10

Images on the left show SEM images of sample surfaces after 28 days of SBF soaking, and images on the right show EDS spectra and the semi-quantitative analysis of atomic percentage for the (a) SLA, (b) 1AE, and (c) DAE-30 surfaces.

Figure 11

(a) MTT assay showing the viability of MC3T3-E1 cells after 24 and 48 h. (b) Extracellular matrix mineralization after 10, 14, and 21 days of culture. (c) ALP activity measured after 3, 7, and 14 days. * p < 0.05 vs. viability control; # p < 0.05 vs. SLA; @ p < 0.05 vs. 1AE. ALP, alkaline phosphatase.