Evaluation of surface characteristics of Ti-6Al-4V and Tilite alloys used for implant abutments

Physicochemical and microscopic characterization of implant-abutment joints

Objective:

The purpose of this study was to investigate Morse taper implant–abutment joints by chemical, mechanical, and microscopic analysis.

Materials and Methods:

Surfaces of 10 Morse taper implants and the correlated abutments were inspected by field emission gun-scanning electron microscopy (FEG-SEM) before connection. The implant–abutment connections were tightened at 32 Ncm. For microgap evaluation by FEG-SEM, the systems were embedded in epoxy resin and cross-sectioned at a perpendicular plane of the implant–abutment joint. Furthermore, nanoindentation tests and chemical analysis were performed at the implant–abutment joints.

Statistics:

Results were statistically analyzed via one-way analysis of variance, with a significance level of P < 0.05.

Results:

Defects were noticed on different areas of the abutment surfaces. The minimum and maximum size of microgaps ranged from 0.5 μm up to 5.6 μm. Furthermore, defects were detected throughout the implant–abutment joint that can, ultimately, affect the microgap size after connection. Nanoindentation tests revealed a higher hardness (4.2 ± 0.4 GPa) for abutment composed of Ti6Al4V alloy when compared to implant composed of commercially pure Grade 4 titanium (3.2 ± 0.4 GPa).

Conclusions:

Surface defects produced during the machining of both implants and abutments can increase the size of microgaps and promote a misfit of implant–abutment joints. In addition, the mismatch in mechanical properties between abutment and implant can promote the wear of surfaces, affecting the size of microgaps and consequently the performance of the joints during mastication.

Nano-scale modification of titanium implant surfaces to enhance osseointegration

The main aim of this review study was to report the state of art on the nano-scale technological advancements of titanium implant surfaces to enhance the osseointegration process. Several methods of surface modification are chronologically described bridging ordinary methods (e.g. grit blasting and etching) and advanced physicochemical approaches such as 3D-laser texturing and biomimetic modification. Functionalization procedures by using proteins, peptides, and bioactive ceramics have provided an enhancement in wettability and bioactivity of implant surfaces. Furthermore, recent findings have revealed a combined beneficial effect of micro- and nano-scale modification and biomimetic functionalization of titanium surfaces. However, some technological developments of implant surfaces are not commercially available yet due to costs and a lack of clinical validation for such recent surfaces. Further in vitro and in vivo studies are required to endorse the use of enhanced biomimetic implant surfaces. STATEMENT OF SIGNIFICANCE: Grit-blasting followed by acid-etching is currently used for titanium implant modifications, although recent technological biomimetic physicochemical methods have revealed enhanced osteoconductive and anti-microbial outcomes. An improvement in wettability and bioactivity of titanium implant surfaces has been accomplished by combining micro and nano-scale modification and functionalization with protein, peptides, and bioactive compounds. Such morphological and chemical modification of the titanium surfaces induce the migration and differentiation of osteogenic cells followed by an enhancement of the mineral matrix formation that accelerate the osseointegration process. Additionally, the incorporation of bioactive molecules into the nanostructured surfaces is a promising strategy to avoid early and late implant failures induced by the biofilm accumulation.

Stress Over Implants of One-Piece Cast Frameworks Made With Different Materials

This study aims to compare stress transmitted to implants and passive fit of one-piece cast frameworks fabricated with 3 different materials: commercially pure titanium (G1-CP Ti), cobalt-chromium alloy (G2-Co-Cr), and nickel-chromium-titanium alloy (G3-Ni-Cr-Ti). In total, 12 frameworks simulating bars for fixed prosthesis in a model with 5 implants were fabricated. The passive fit of the framework interface was measured using an optical microscope and the stresses transmitted to implants were measured using quantitative photoelastic analysis. Data were statistically analyzed by analysis of variance (ANOVA) and least significant difference (LSD) tests (α = 0.05). Mean and standard deviation values of passive fit and stress over implants are presented, respectively: G1 [472.49 (109.88) μm and 11.38 (9.23) KPa], G2 [584.84 (120.20) μm and 15.83 (9.30) KPa], and G3 [462.70 (179.18) μm and 16.39 (9.51) KPa]. For stress over implants, there were significant differences between G1, G2, and G3 (P = 0.035), being the lowest values for the G1. There were no significant differences for passive fit between G1 and G3 (P = 0.844), but both were statistically different from G2 (P = 0.028 and P = 0.035, respectively), which showed the worse results. It may be concluded that the stress over implants was affected by the tested materials. The CP Ti presented the best values for the evaluated items.

Implant/abutment vertical misfit of one-piece cast frameworks made with different materials

This study compared vertical and passive fit of one-piece cast frameworks made with 3 different materials: commercially pure titanium (CP Ti - G1), cobalt-chromium alloy (Co-Cr - G2) and nickel-chromium-titanium alloy (Ni-Cr-Ti - G3). Fifteen frameworks were obtained simulating bars for fixed prosthesis in a model with 5 implants. The passive and vertical fit of the framework interface was measured using an optical microscope at ×30 magnification. Data were statistically analyzed by ANOVA and LSD tests (α=0.05). Mean and standard deviation values for passive fit and vertical fit were, respectively: G1 [472.49 (109.88) µm and 29.9 (13.24) µm], G2 [584.84 (120.20) µm and 27.05 (10.30) µm], and G3 [462.70 (179.18) µm and 24.95 (11.14) µm]. For vertical fit, there were no significant differences among G1, G2 and G3 (p=0.285). There were no significant differences for passive fit between G1 and G3 (p=0.844), but both differed significantly from G2 (p=0.028 and p=0.035, respectively), which showed the highest misfit values. It may be concluded that the vertical fit of frameworks was not affected by the tested materials, and that one-piece cast frameworks resulted in inadequate passive fit. The Co-Cr alloy presented the worst values for passive fit.