Laser-Induced µ-Rooms for Osteocytes on Implant Surface: An In Vivo Study

Abstract

Laser processing of dental implant surfaces is becoming a more widespread replacement for classical techniques due to its undeniable advantages, including control of oxide formation and structure and surface relief at the microscale. Thus, using a laser, we created several biomimetic topographies of various shapes on the surface of titanium screw-shaped implants to research their success and survival rates. A distinctive feature of the topographies is the presence of "µ-rooms", which are special spaces created by the depressions and elevations and are analogous to the µ-sized room in which the osteocyte will potentially live. We conducted the comparable in vivo study using dental implants with continuous (G-topography with µ-canals), discrete (S-topography with μ-cavities), and irregular (I-topography) laser-induced topographies. A histological analysis performed with the statistical method (with p-value less than 0.05) was conducted, which showed that G-topography had the highest BIC parameter and contained the highest number of mature osteocytes, indicating the best secondary stability and osseointegration.

Keywords: biocompatibility; in vivo; laser texturing; osseointegration; rabbit tibia; titanium implants; topography.

Figure 1

Design of topographies on the titanium implants’ surface of: irregular topography (I-topography) and two variants of topographies with μ-rooms (S-topography with μ-cavities and G-topography with μ-canals). This paper poses a question of what type of topography is the most preferable for osteocytes.

Figure 2

Schematic representation of the laser processing process. (A) Illustration of the laser titanium surface treatment at the optical system focus with a laser spot of 50 μm diameter with a Gaussian intensity distribution over the beam cross section; scheme of surface scanning by laser pulses and a model of the resulting topography of (B) “irregular structure” I-topography, (C) “slots” S-topography, and (D) µ-room-shaped “grooves” G-topography.

Figure 3

The histological preparation steps: 1—extraction of an implant with bone fragment; 2—cross-section of an implant with a bone fragment embedded in methylmethacrylate; 3—the sample after polishing; and 4—toluidine-blue-stained sample.

Figure 4

Images of implants. (A) Implant before and after laser texturing; SEM-images of the laser-textured implants: the profile, magnified view, and cross-section of (B) untextured control group, (C) “irregular structure” I-topography and µ-rooms-shaped (D) “slots” S-topography and (E) “grooves” G-topography.

Figure 5

Optical images of histological sections of untextured (control) and laser-textured implants: 1.5-month-old (1st column) and 3-month-old (2nd column). White arrows point to the osteocytes in the μ-cavities and μ-canals.

Figure 6

(A) Osseointegration parameters BIC (bone-to-implant contact) and FIC (fibrous-to-implant contact) for 1.5- and 3-month results (B) the control group and (C) the G-topography; yellow line is the length of the areas at the site of implant surface contact with the bone tissue, blue line is the implant surface contact with granulation tissue, and red line is a distance of 800 µm for each sample.

Figure 7

Osseointegration parameters for 1.5- and 3-month results: (A) images of bone tissue and the corresponding processed images of osteocyte; (B) the number of cells; (C) the area occupied by cells (cell area); and (D) average cell size; (*) indicates p-value < 0.05, (**) indicates p-value < 0.01.

Figure 8

Results of assessing the stability of the implants using the Osstell ISQ device: distribution of the stability index of implants for 1.5 and 3 months.