Impact of High Insertion Torque on Implant Surface Integrity

Abstract

Introduction: The long-term success of dental implants depends on the preservation of supporting tissues over time. Recent studies have highlighted the release of titanium particles as a potential etiology for the onset and progression of peri-implant diseases modulated by inflammatory biomarkers. This study provides a comprehensive analysis of surface changes associated with high insertion torque placement.

Methods: Three groups of cylindrical threaded dental implants, each representing different surface topographies produced by anodization or a combination of grit-blasting and acid-etching processes, were inserted into fresh cow rib bone blocks used to mimic human jaws. Individual bone blocks were fabricated with a dimension of 20 × 15 × 15 mm, randomly assigned to the three implant groups. Prior to dental implant placement, the bone blocks were divided in half to facilitate implant removal without introducing additional damage. The drilling protocol was modified, excluding the final drill recommended by the manufacturer to ensure higher insertion torque values during the procedure. Dental implants were removed from the bone blocks and processed for analysis. Surface roughness was characterized using interferometry on the same area before and after insertion. Scanning electron microscopy (SEM) with a back-scattered electron detector (BSD) was employed to identify the implant surface and loose particles at the bone block interface.

Results: The high insertion torque protocol used in this study resulted in higher insertion torque values compared to manufacturers' protocol, but no difference was observed when comparing the three implant groups. Surface roughness characterization revealed that amplitude and hybrid roughness parameters for all three groups were lower after insertion. The surfaces exhibiting a predominance of peaks (Ssk [skewness] > 0) associated with higher structures (height parameters) showed greater damage at the crests of the threads, while no changes were observed in the valleys of the threads. SEM-BSD images revealed loose titanium particles at the bone blocks interface, predominantly at the crestal cortical bone level.

Conclusions: High insertion torque resulted in surface damage at the crests of threads, which subsequently led to the release of titanium particles primarily at the bone crest. The initial release of titanium particles during implant insertion at the bone-implant interface warrants further exploration as a potential cofactor for marginal bone loss.

Keywords: biomaterials; implant design; implant surface; surface properties; surface topography.

FIGURE 1

Implant was stabilized with a mounter attached to a slide to ensure exact alignment (a). An indent was created to adjust the implant position during the before and after measurement (b).

FIGURE 2

Recommended insertion torque and high insertion torque were obtained using an undersized host bone. Variations of the recommended and high torque values indicated similar changes in absolute values (Ncm) but higher proportional (%) changes for OS > TU > OS implants.

FIGURE 3

Surface roughness S _a, S _dr, and S _sk parameters (mean and SD) and material volume of the implants before and after insertion into bone (*p < 0.05 and **p < 0.01, ***p < 0.001). Data reported from measurements at the thread crest and valley. OS = OsseoSpeed TX; S _a = average height deviation; S _dr = developed interfacial area ratio; SL = SLA Active Bone Level; S _sk = degree of symmetry of the surface heights about the mean plane; TU = TiUnite MkIII.

FIGURE 4

The surface functional height (S _vk + S _k + S _pk) of implants before and after insertion into bone (*p < 0.05, **p < 0.01, ***p < 0.001). OS = OsseoSpeed TX; S _k = core roughness height of the surface with the predominant peaks and valleys removed; SL = SLA Active Bone Level; S _pk = peak height above the core roughness; S _vk = valley depth below the core roughness; TU = TiUnite MkIII.

FIGURE 5

The average roughness (S _a) and developed surface interfacial area ratio (S _dr) variation (Δ) on each individual thread after insertion along the: TU (11 threads), OS (9 threads and 11 microthreads), and SL (8 threads) implants.

FIGURE 6

Scanning electron microscopy images of TU, OS, and SL implant thread located below the crestal cortical bone. TU implant (A, B) after insertion into bone revealing surface damage as observed by chipping of the porous structures and cracks at the oxide layer. OS (C, D) and SL (E, F) exhibited flattened regions with wear marks at the crest of the thread as a result of the damage to the surface during implant insertion. Magnification 200x and 1000x.

FIGURE 7

Scanning electron microscopy—back‐scattered electron detector (SEM‐BSD) images of the implantation sites at the crestal cortical bone showed titanium loose particles (white shiny spots) along all implantation sites after the removal of (TU) (A), OS (G), and SL (M) implants. The elemental content of the particles (Ti) and the surrounding bone was confirmed through energy‐dispersive x‐ray spectroscopy (EDS) mapping of the surface: Titanium (B, H, and N), calcium (C, I, and O), oxygen (D, J, and P), and phosphorous (calcium yellow, oxygen purple, and phosphorous (F, L, and Q).

FIGURE 8

Surface roughness S _{a and} S _dr, and material volume (V _m) proportional difference ((Final value/Initial value)/Initial value) of the implants before and after insertion comparing normal and high torque protocols. Data reported from measurements at the crest of the thread. OS = OsseoSpeed TX; S _a = average height deviation; S _dr = developed interfacial area ratio; SL = SLA Active Bone Level; TU = TiUnite MkIII.