The Addition of Hydroxyapatite Nanoparticles on Implant Surfaces Modified by Zirconia Blasting and Acid Etching to Enhance Peri-Implant Bone Healing

Abstract

This study investigated the impact of adding hydroxyapatite nanoparticles to implant surfaces treated with zirconia blasting and acid etching (ZiHa), focusing on structural changes and bone healing parameters in low-density bone sites. The topographical characterization of titanium discs with a ZiHa surface and a commercially modified zirconia-blasted and acid-etched surface (Zi) was performed using scanning electron microscopy, profilometry, and surface-free energy. For the in vivo assessment, 22 female rats were ovariectomized and kept for 90 days, after which one implant from each group was randomly placed in each tibial metaphysis of the animals. Histological and immunohistochemical analyses were performed at 14 and 28 days postoperatively (decalcified lab processing), reverse torque testing was performed at 28 days, and histometry from calcified lab processing was performed at 60 days The group ZiHa promoted changes in surface morphology, forming evenly distributed pores. For bone healing, ZiHa showed a greater reverse torque, newly formed bone area, and bone/implant contact values compared to group Zi (p < 0.05; t-test). Qualitative histological and immunohistochemical analyses showed higher features of bone maturation for ZiHa on days 14 and 28. This preclinical study demonstrated that adding hydroxyapatite to zirconia-blasted and acid-etched surfaces enhanced peri-implant bone healing in ovariectomized rats. These findings support the potential for improving osseointegration of dental implants, especially in patients with compromised bone metabolism.

Keywords: bone regeneration; hydroxyapatite; osseointegration.

Figure 1

Topographical characterization of Zi and ZiHa surfaces. (A,B) Photomicrographs related to the analysis of scanning electron microscopy (SEM) (magnification of 1000× and 2000×) of the surface of Ticp discs treated with Zi and ZiHa. (C) Graphical representation of the mean surface roughness (Ra) of the Ticp alloy as a function of surface modifications in both experimental groups. (D) Graphical representation of the mean surface free energy concerning the contact angle for water and diiodomethane of the Ticp alloy, as a function of surface modifications for the Zi and ZiHa groups) (N = 10 discs per group).

Figure 2

Visual and graphical representation of the histological analysis. (A) Photomicrographs for the representation of bone tissue maturation of each experimental group at 14 and 28 days post operation. The black arrows represent the osteocytes in the bone matrix. (B) Graphical representation of inflammatory cell count, showing statistical differences between the Zi and ZiHa groups at 14 (p = 0.036) and 28 days (p = 0.019), as well as for the ZiHa group in both periods (p < 0.001). (C) Graphical blood vessel count representation, demonstrating an intergroup difference at 14 (p = 0.010) and 28 days (p = 0.001). (n = 6 tibiae per group). Original magnification: 1000×. BT: Bone tissue; CT: connective tissue.

Figure 3

Representative images of immunohistochemical analysis. (A) Photomicrographs representing immunostaining for vascular endothelial growth factor (VEGF) at the 14-day time point. (B) Photomicrographs representing immunostaining for osteocalcin (OCN) at the 28-day time point. The black arrows represent the cells labeled by the primary antibodies in all images (regions of brown staining). Original magnification: 1000×.

Figure 4

Visual and graphical representation of histometric analysis. (A) Representative images of peri-implant bone tissue on calcified slides, 12× objective. (B) Graphical representation of the reverse torque analysis, showing superiority in the ZiHa group (p = 0.030). (C) Demonstration of neoformed bone area values, highlighting greater neoformation in the ZiHa group (p = 0.003). (D) Representation of bone-implant contact, registering higher values in group ZiHa (p = 0.011) (n = 6 tibiae per group).

Figure 5

Representative image of the two discs used for surface characterization analysis with their surfaces corresponding to the respective implants.