Received date: December 19, 2016; Accepted date: December 27, 2016; Published date: December 30, 2016
Citation: Vijaya Sankar Yadav V, Sesha Reddy P, Swaroop Kumar Reddy A, Jain AR (2016) Evaluation and Comparison of Surface Roughness Levels, Surface Wettability, and Surface Configuration of Commercially Pure Titanium Surface. Biol Med (Aligarh) 9:390. doi:10.4172/0974-8369.1000390
Copyright: © 2016 Yadav et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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The bonding between the living bone and the surface of the load-bearing implant is believed to be an important factor in the success of implants. A major consideration in designing implants has been to produce surfaces that promote desirable responses by the cells and tissue-contacting implants. The aim was to evaluate different methods of modification of titanium surface and to compare surface roughness levels, surface wettability, and surface configuration of various treated surfaces of commercially pure titanium. Commercially pure titanium (Grade I) sheets of 0.2 mm thick and 10 × 10 mm were used. Total specimens were divided into six groups (Groups A–F) according to the surface modification. And 10 samples were included in each group. Group F showed the highest mean roughness value among the tested samples of all groups (Mean Ra-3.231 μm). Group C showed the lowest contact angle (mean contact angle—59°). Surface roughness measurement with the help of surface profilometer revealed that samples treated with blasting with alumina (50 μ) blasting followed by acid etching with 2% hydrofluoric acid showed the highest mean roughness value.
Surface roughness; Surface wettability; Surface configuration; Titanium
The goal of placement of endosseous dental implants is to achieve osseointegration or biointegration of the bone with the implant. Titanium and titanium alloy (Ti6A14V) have been the most widely used of these materials. Branemark reported a scientific transition in the nature of interfacial implant–host bone behavior involving commercially pure titanium implants in 1977, and the field of dental implants entered the new era of therapeutic possibilities. Titanium encourages the formation of bone and it’s bonding directly to the implant. Commercially pure titanium is material of choice for implants because it is biocompatible, has high corrosion resistance, is light weighted and durable, and can be easily prepared in different shapes and textures without affecting its biocompatibility [1-5].
The properties of the implant depend in part on its chemical composition and on surface properties that affect both osteoblasts and chondrocyte metabolism and phenotype expression. Surface morphology and bone implant interaction determines the predictability of endosseous dental implant/bone integration [6,7]. Morphometric analyses have shown differences in bone–implant contact percentages with varying surface characteristics as well as sensitivity of cells to surface microtopography. Cellular behaviors such as adhesion, morphologic change, functional alteration, and proliferation are greatly affected by surface properties, including hydrophilicity, roughness, texture, and morphology. The effects of surface topography on cell adhesion vary with the type of the cell [8-12]. Human gingival fibroblasts attach more to an electro-polished surface than to etched or blasted surfaces. In contrast, osteoblasts like cells demonstrate significantly a higher level of attachment to rough surface than a smooth surface. The surface modification of titanium materials has been shown to improve bony apposition, tissue adhesion, and migration [13-17].
There are two ways to modify the surface layer: creation of convex texture or concave texture. Additive treatments such as plasma spray coating of hydroxyapatite particles or titanium beads or physical or chemical vapor deposition are performed to create convex surface morphology. It is possible that deposited particles can fracture from the surface. In contrast, mechanical treatments such as sand blasting or chemical treatments with acid or alkaline can create a concave surface [18-22]. It may not be possible to study commercially available implants’ surfaces and their influence on wettability. It may be prudent to create the different surfaces on the flat plane to study its characteristics and influence on wettability. To facilitate this, a study was conducted with the following aims.
1. To evaluate different methods of surface modification of the titanium surface
2. To compare the surface roughness level of variously treated surfaces of the titanium
3. To measure the surface wettability of the variously treated surfaces of the titanium
4. To determine the surface configuration variously treated surfaces of titanium
Commercially pure titanium, ASTM grade I (99.7% Ti, 0.2% Fe, 0.1% O2, 0.05% N) sheet, (Mishra Datu Nigam Ltd, Hyderbad) of 0.2 mm thickness and 10 × 10 mm diameter was used for this study. For the mechanical group, the blasting of the titanium substrates with various blasting materials is done using alumina and tricalcium phosphate. For the chemical group Acid and etching was done: hydrofluoric acid 2% (Group), hydrochloric acid 10%, and sulfuric acid 10%. Surface roughness levels were measured with the help of surface profilometer. Surface wettability was measured with the help of contact angle measurement using contact angle measurement setup, and surface configuration was determined with the help of scanning electron microscopy. All the 60 plates were standardized to 10 mm length × 10 mm wide and 0.02 mm thick and were ultrasonically cleaned before being subjected to following surface modifications.
Group A: AL2Os blasted with 50 m and 80-psi pressure
Group B: Blasted with commercially pure TCP blasted
Group C: Hydrofluoric acid 2% for 10 min
Group D: HCL+H2SO4 20% for 10 min
Group E: AL2O3 blasting + hydrofluoric acid 2%
Group F: AL2O3 blasting + HCL + H2SO4 20%
Mechanical treatment group (Group A and Group B)
Alumina of 50 μ and tricalcium phosphate (120 μ). size particles were filled in the conventional sandblasting machine. A titanium sheet of 0.2 mm thickness and 10 × 10 mm diameter is fixed in the wooden frame that is specially made to hold the specimen. The wooden frame along with the specimen are held 5 cm away from the blasting tip, blasting of the surface is done on both sides for 2 min at 80 Lb pressure, and also for 10 min at 80 Lb pressure.
Chemical treatment group (Group C and Group D)
2% of hydrofluoric acid and 10% of HCL and H2SO4 are prepared by diluting 2 ml of concentrated acid with 98 ml of distilled water. A titanium sheet of 0.2 nm thickness and 10 × 10 mm diameter is fixed in the wooden frame and etched on both sides by placing it in the beaker containing 2% of hydrofluoric acid for 10 min.
Mechanico-chemical group (Group E and Group F)
Alumina (50 μ) blasting of the surface is done on both sides for 2 min at 80 Lb pressure, followed by ultrasonic cleaning of the sample. The cleaned sample is etched with 2% hydrofluoric acid and 20% of hydrochloric acid and sulfuric acid for 10 min by placing it in the beaker containing acid for 10 min.
The surface topography of all the surface-modified samples is studied by coating them with gold and scanning them under the scanning electron microscope at high magnification (500x, 2000x) (Figures 1-6). The total specimens were divided into 6 groups according to the surface modification, and 10 samples were done for each group. Roughness average (Ra) and contact angle were totally measured for 60 samples.
The mean values of all the samples in each group calculated along with their standard deviation and the obtained values were as follows.
Group F showed the highest mean surface roughness value (3.231 μm) of all the groups, and the least was Group C (0.558 μm) (Graph 1). Group F showed the highest mean contact angle value (98°) of all the groups, and the least was Group C (59°). The mean values of all six groups were statistically analyzed using the Pearson correlation test (nonparametric) with the corresponding contact angles (θ).The mean values of all samples in Group A, Group B, Group E, and Group F have a positive correlation with their corresponding contact angles. But, Group C and Group D have a negative correlation with their corresponding contact angles. None of the groups have shown any statistical significance with their corresponding contact angles (Graph 3). The mean surface roughness value was compared within the groups according to the surface modification, namely, mechanical (Groups A and B), chemical (Groups C and D), and mechanico-chemical (Groups E and F) groups. Statistical significance was observed only among the mechanical group, i.e., Group A and Group B (Table 1). The mean Surface Contact angle value was compared within the groups according to the surface modification, namely, mechanical (Groups A and B), chemical (Groups C and D), and mechanico-chemical (Groups E and F) groups. Statistical significance was observed among all the groups compared (Table 2). Group A was compared with all other groups using ANOVA. Statistical significance was observed only between Group A vs Group D (0.007*). All other values were nonsignificant (Table 3).
|Group A vs Group B||2.033||0.8022||0.000*|
|Group C vs Group D||0.3270||0.7102||0.179|
|Group E vs Group F||0.822||1.3149||0.079|
Table 1: Mean surface roughness value comparison Paired sample test
|Group A vs Group B||17.50||3.536||0.000*|
|Group C vs Group D||7.50||4.249||0.000*|
|Group E vs Group F||8.00||9.775||0.029*|
Table 2: Mean contact angle value comparison Paired sample test
|Groups||Mean Ra Value (μm)||Significance|
|Group A vs B||0.974||0.180|
|Group A vs C||0.175||0.775|
|Group A vs D||0.228||0.007*|
|Group A vs E||1.420||0.053|
|Group A vs F||0.543||0.059|
Table 3: Comparision of Group A with all other groups
The objective of this study was to evaluate different methods of the surface modifications of titanium surfaces and comparing the roughness value and surface wettability of variously treated samples.
1. Increased surface area of the implant adjacent to the bone
2. Improved cell attachment to the implant surface
3. Increased bone present at the interface
4. Increased biomechanical interaction of the implant with the bone (surface area reduces stress next to the implant)
An increase in surface area is one mechanism to reduce stress next to the implant because stress equals force divided by the area. However, increasing surface area as a goal of engineering may represent a limited approach to improving the implant–bone relation available. Clinical evaluations do not indicate the negative effects of rough surface implants on clinical or radiographic measures of performance. Changes in topography affect cell adhesion to the surfaces of similar chemistry. Types of cells that adhere to the surfaces are red blood cells and platelets within fibrin-rich matrix. Platelets play an important role as a carrier of abundant growth factors to direct wound healing [5-7,11,13,17,19]. Davies hypothesized that improved wettability and increased clot retention were measured at acid-etched implant surfaces, resulting in improved osseointegration [18,19,22]. The surface roughness and wettability can be altered or modified by modifying the surface of the titanium. This research project dealt mainly with concave surface modification.
Tomas Albrektsson studied bone–metal interface and stated that implant characteristics are very important for osseointegration. Carl E Misch stated that an increase in the surface area of implants would allow the use of shorter implants especially in posterior regions [2,3]. Maurizio Piattelli and coworkers studied the effect of blasting the surface of titanium with resorbable blast material and concluded that there was an increased implant contact for these surfaces when compared to machined surfaces . Young Jun Lim and coworkers concluded that when contact angles were greater than 45°, they increased linearly with roughness average (Ra) and when they were less than 45°, they decreased linearly with Ra to determine the relationship between the contact angle and roughness average [26-28]. The contact angles of all the specimens were measured with distilled water, and it was observed that the contact angles decreased with the and increase in roughness average. The measurement of wettability of a surface, expressed by the contact angle, might be the predictive index of cyto-compatibility. Cell adhesion to and spreading on a biomaterial are dependent, among other factors, on the surface wettability of the biomaterial; therefore, the surface roughness affects wettability [29,30].
W. Aubreysoskolne stated that cell adherence to rough titanium surfaces is greater than to machine surfaces, and Lyndon F. Cooper stated that increased titanium surface topography improves the bone– implant contact and the mechanical properties of the enhanced interface, and growing clinical evidence for increased bone–implant contact at an altered implant surface confirms the advantages of the increased functional area. The surface modifications of the titanium are found to increase the surface area of titanium that would result in greater surface coverage by bone. The contact angle representing the surface wettability also affects the bone–implant contact [17,19,21,25,29].
Acid etching is a subtractive method to texture titanium implant surfaces have been documented to lead to more bone apposition. The etching process corrodes the titanium surface greatly; it clears the irregular pits of varying depth and produces a microroughness of 0.5-3 μm, depending on the etching conditions; a macroroughness of 10-20 μm is superimposed on top of the microroughness. Sandblasting prior to etching led to an anchorage increase of 75.4% after 4 weeks and 111.4% after 12 weeks. SLA surface, micromechanical anchorage might have been achieved by bone in growth into the macrorugosities of the SLA surface obtained by sandblasting rather than by the pits created by etching [31,32]. In the present study, mechanico-chemical groups (SLA) have shown the highest roughness values (3.231 μm, Group F, and 2.24 μm, Group E. The acid etching technique has been used with the goal of avoiding the disadvantages of the sand blasted, i.e., the contamination of the titanium by the materials used in the blasting, the nonhomogeneous treatment of the surface, and the risk of loss of the metallic material, which could reduce the mechanical resistance of the implant. AL2O3 used in the blasting procedure is biocompatible and does not interfere with the osseointegration process; the etching phase could help to remove the contaminants of the surface and increase the reactivity of the metal.
The sandblasted acid etch (SLA) surface was demonstrated to be more powerful in enhancing the interfacial shear strength of implants than the acid etching surface. In comparison with the acid etching surface implants, the SLA-surfaced implants showed approximately 30% higher RTVs at the healing periods, 4, 8, and 12 weeks, and also more than 5% higher interfacial stiffness. The preprocessing by sandblasting before acid etching accounts for these difference and therefore before the acid etching is necessitated as well from the viewpoint of biomechanics [29-32].
The surface roughness measurement with the help of surface profilometer revealed that samples treated with blasting with alumina (50 μ) blasting followed by acid etching with 2% hydrofluoric acid showed the highest mean roughness value.