The long-term success of Ti alloy dental implants largely depends on rapid healing with safe integration into the jaw bone (osseointegration) . The surface topography of the Ti alloy is crucial for the long term success of dental implants. Treatments for Ti implant materials have been developed in the last decade in a concentrated effort to improve the osseointegration process . Recently, it has been shown that changes in the physicochemical properties of Ti alloy implants results in significant modulation of cell recruitment, adhesion, inflammation and bone remodeling activities, in addition to regulation of the bone formation response . The use of dental implants has been in general highly successful with around 96 % of them remaining in the patient more than 10 years. Figure 1 shows a basic description of how dental implants, with the abutement and crown, are typically placed into the jawbone of the mouth.
In recent years, several treatment strategies (mechanical, chemical, physicochemical, etc.) have been proposed for the infection of the dental tissue around an implant (peri-implantitis) . Peri-implantitis is an "inflammatory process around an implant, characterized by soft tissue inflammation and loss of supporting bone" . After a healing time is allowed for re-osseointegration, the dental implant is loaded with a prosthetic abutment and crown in order to replace the missing teeth. However, bone loss is a potential complication for dental implants once inflammation of the gum and dental tissue around the implant sets in due to bacterial infection. The advantageous dental implant surface properties, i.e. the high reactivity of the oxidized titanium that allows cellular adhesion, is altered by the presence of bacteria and the residues of their metabolic activity. Thus, the contaminated surface acts as a foreign body and can lead to more inflammation of the soft tissue and bone loss surrounding the implant. The treatment of peri-implantitis involves surface decontamination and cleaning. These different treatments for peri-implantitis could possibly be used in a strategic way to modify the Ti alloy surface and cause an improvement in the host-to-implant response . This report discusses the effect of the different dental treatments on the Ti alloy implant material’s surface properties and whether these may accelerate the re-osseointegration of dental implants during healing after peri-implantitis. The osseointegration of dental implants is relatively long (3–6 months), therefore, surface modifications that can accelerate this phenomenon will lead to shorter healing times, lower failure rates, and minimization of discomfort for the patient .
Fig. 1A–D: Schematic demonstrating the placement of titanium (Ti) dental implants into the jawbone: A) typical Ti implant which is placed into the jawbone; B) osseointegrated implant with fixed abutment (to hold the dental crown) inserted; C) and D) examples of implants with abutments and cemented dental bridges replacing missing teeth.
Effect of surface roughness
Enhanced titanium implant surface topography improves the bone-to-implant contact and the mechanical properties of the enhanced interface [8–11]. In the absence of controlled comparative clinical trials, the aggregate experimental evidence supports the use of titanium implants with enhanced surface topography .
Surface roughness has been identified as an important parameter concerning the capacity of implant materials to be anchored into bone tissue . There are a variety of methods to increase the surface roughness of the implant material, where the most commonly used are: machining, sandblasting, acid etching, anodic oxidation, laser modification, or a combination of these techniques. Furthermore, commercially available implants have been categorized according to their average surface roughness value (Sa), the mean height of the peaks and mean depth of the valleys on the surface, into 4 groups: smooth (Sa < 0.5 μm), minimally rough (0.5 μm < Sa < 1.0 μm), moderately rough (1.0 μm < Sa < 2.0 μm) and rough (Sa > 2.0 μm) . Another important parameter is Sdar which represents the developed surface area of a rough surface in comparison to a perfectly flat, smooth surface. According to Teughels et al.  roughness of the implant surface, as well as its chemical composition, has a significant impact on the amount and quality of plaque formation. Finally, there is no existing evidence that implant surfaces exposed to the oral cavity show the development of biofilms having compositions which depend on the surface roughness [16–17]. How can implant topography be represented and categorized? Wennerberg concisely reviewed topographic measurement methods that are applicable to dental implants. Three-dimensional (3D) measurements are needed to account for the isotropic deviations of topographic elements from the mean surface plane . Contact instruments, such as profilometers, can underestimate the surface feature dimensions. Optical instruments are preferred for the evaluation of screw shaped implants of soft materials, such as titanium alloys . The limitations of 2D surface measurement and characterization have motivated the development of efficient and practical 3D surface measurement and characterization. Three dimensional techniques give a better understanding of the surface in its functional state.
Titanium alloy modification processes
A total of 25 cylindrical implants (5 per sample, control sample + 4 treatment processes) made from grade 5 CP (commercially pure) titanium (Ti) alloy (PM international suppliers, LLC, EEUU), i.e. Ti-6Al-4V (TAV) with a composition of 90 % Ti, 6 % Al (aluminum), and 4 % V (vanadium), were analyzed. The samples were 10 mm in diameter and 5 mm in length. The implant samples were surface-treated by several different processes typically used in dentistry:
- chemical: tetracycline and photosensitizer exposure;
- physical: ultrasonication and
- physicochemical: bicarbonate jet polishing;
which will be explained in more detail below.
The following types of microscopy were used:
- Confocal Microscopy (CM): CM provides a convenient means of acquiring 3D images of an object. The Leica DCM 3D dual system was used to measure the surface topography and calculate the surface roughness parameters. Images were taken with a confocal objective with a magnification of 20x and a numerical aperture (NA) of 0.50.
- Atomic Force Microscopy (