Juergen Geis-Gerstorfer

A Review on the Wettability of Dental Implant Surfaces II: Biological and Clinical Aspects

Dental and orthopedic implants have been under continuous advancement to improve their interactions with bone and ensure a successful outcome for patients. Surface characteristics such as surface topography and surface chemistry can serve as design tools to enhance the biological response around the implant, with in vitro, in vivo and clinical studies confirming their effects. However, the comprehensive design of implants to promote early and long-term osseointegration requires a better understanding of the role of surface wettability and the mechanisms by which it affects the surrounding biological environment. This review provides a general overview of the available information about the contact angle values of experimental and of marketed implant surfaces, some of the techniques used to modify surface wettability of implants, and results from in vitro and clinical studies. We aim to expand the current understanding on the role of wettability of metallic implants at their interface with blood and the biological milieu, as well as with bacteria, and hard and soft tissues.

Cellular Reactions of Osteoblasts to Micron- and Submicron-Scale Porous Structures of Titanium Surfaces

Osteoblast reactions to topographic structures of titanium play a key role in host tissue responses and the final osseointegration. Since it is difficult to fabricate micro- and nano-scale structures on titanium surfaces, little is known about the mechanism whereby the topography of titanium surfaces exerts its effects on cell behavior at the cellular level. In the present study, the titanium surface was structured in micron- and submicron-scale ranges by anodic oxidation in either 0.2 M H3PO4 or 0.03 M calcium glycerophosphate with 0.15 calcium acetate. The average dimensions of pores in the structured surface were about 0.5 and 2 µm in diameter, with roughness averaging at 0.2 and 0.4 µm, respectively. Enhanced attachment of cells (SaOS-2) was shown on micron- and submicron-scale structures. Initial cell reactions to different titanium surfaces, e.g. the development of the actin-containing structures, are determined by the different morphology of the surfaces. It is demonstrated that on either micron- or submicron-structured surfaces, many well-developed filopodia were observed to be primary adhesion structures in cell-substrate interactions, and some of them entered pores using their distinct tips or points along their length for initial attachment. Therefore, porous structures at either micro- or submicrometre scale supply positive guidance cues for anchorage-dependent cells to attach, leading to enhanced cell attachment. In contrast, the cells attached to a smooth titanium surface by focal contacts around their periphery as predominant adhesion structures, since repulsive signals from the environment led to retraction of the filopodia back to the cell bodies. These cells showed well-organized stress fibres, which exert tension across the cell body, resulting in flattened cells.

A review on the wettability of dental implant surfaces I: Theoretical and experimental aspects

The surface wettability of biomaterials determines the biological cascade of events at the biomaterial/host interface. Wettability is modulated by surface characteristics, such as surface chemistry and surface topography. However, the design of current implant surfaces focuses mainly on specific micro- and nanotopographical features, and is still far from predicting the concomitant wetting behavior. There is an increasing interest in understanding the wetting mechanisms of implant surfaces and the role of wettability in the biological response at the implant/bone or implant/soft tissue interface. Fundamental knowledge related to the influence of surface roughness (i.e. a quantification of surface topography) on titanium and titanium alloy surface wettability, and the different associated wetting regimes, can improve our understanding of the role of wettability of rough implant surfaces on the biological outcome. Such an approach has been applied to biomaterial surfaces only in a limited way. Focusing on titanium dental and orthopaedic implants, the present study reviews the current knowledge on the wettability of biomaterial surfaces, encompassing basic and applied aspects that include measurement techniques, thermodynamic aspects of wetting and models predicting topographical and roughness effects on the wetting behavior.

Optical properties of Au−Pt−Pd-based high noble dental alloys

The effects of the addition of various alloying elements (In, Sn, Zn) of up to 4 mass % on the optical properties of Au-Pt-Pd-based high noble dental alloys were investigated by means of spectrophotometric colourimetry. Spectral reflectance data from the mirror-polished flat samples were collected at 10 nm intervals in the wavelengths ranging from 360 nm to 740 nm under the CIE standard illuminant D65 and the observer of 10 degrees. Three dimensional colour coordinates in the CIEL*a*b* andL*C*h colour spaces were also obtained to specify the alloy colour. The alloying addition of a small amount of Sn and/or In increased the reflectance in the long-wavelength range and decreased the reflectance in the shortwavelength range. As a result, the maximum slope of the spectral reflectance curve at the absorption edge near 520 nm apparently increased with the additions of Sn and/or In. This change in shape of the spectral reflectance curve caused the increased chromaticity indices,a*, b*, and chroma,C*. On the other hand, the hue angle was not greatly affected by the alloying elements, with the exception of the alloy containing 4 mass % Sn showing a slightly lower hue angle. It was evidenced that in the single-phase structured alloys the average number of valence electrons per atom,e/a, in an alloy is a controlling factor of the colour of Au−Pt−Pd-based high noble dental alloys. That is, by increasinge/a-value,a*-, b*-, C*- coordinates systematically increased, giving a slight gold tinge to the parent Au-Pt-Pd alloy within the limitation that the structure of an alloy is a single phase. The addition of Sn of 2 mass % or more produced a small amount of the second phase of possible intermetallic compounds between Sn and Pd or Pt. The coexistence of a small amount of the second phase of possible intermetallic compounds further increased a gold tinge. However, the inclusion of 4 mass % Sn to the parent Au-Pt-Pd alloy gave a very light tint of red to the alloy. Results of the present study are expected to be useful in controlling colour of Au-Pt-Pd-based high noble dental alloys.

The influence of chlorine ions and pH value on the cation release from Ni20CrMo alloys

Abstract The release of cations from six highly pure Ni20CrxMo alloys (x = 0, 2, 4, 6, 8, 10), caused by corrosive processes, was studied in artificial saliva as a function of the chlorine ion concentration from 0·01 to 1·0 m NaCl and as a function of the pH value from 1 to 7, using a graphite furnace atomic absorption spectrometer. With increasing chloride ion concentrations, substance losses were recorded with gradients from 25μg cm −2 m (NaCl) −1 for Ni2OCr to 3μg cm −2 m (NaCl) −1 for Ni20Cr10Mo. In a pH range from 3 to 7 the substance loss varied for Ni20Cr between 100μg cm −2 at pH 3 and 5 μg cm −2 at pH 7, whereas the substance loss for Ni20Cr10Mo lay between 8μg cm −2 at pH 3 and 4μ cm −2 at pH 7. The addition to the Ni20Cr alloy of a mere 2% wt molybdenum increased the corrosion resistance as measured by cation release in the clinically relevant pH range between 4 and 7 by a factor of approximately 3, whereas at pH values smaller than 4, greater molybdenum content is necessary in order to guarantee a sufficient corrosion resistance. Additions of higher molybdenum content in the alloy was found to stabilize in saline environments in the passive layer. Additionally, increasing the molybdenum content also served to decrease the observed grain boundary corrosion. This leads to the observation that for NiCr alloys with higher molybdenum content (for instance, Ni20Cr10Mo) no increased corrosion is recognizable even at a pH value of 1.

Compatibility of a Silicone Impression/Adhesive System to FDM-Printed Tray Materials—A Laboratory Peel-off Study

Computer-aided design (CAD) and additive manufacturing (AM) have shown promise in facilitating the fabrication of custom trays. Due to the clinical requirements, custom tray materials should achieve good bonding to the impression/adhesive systems. This study evaluated the retention of three fused deposition modeling (FDM) custom tray materials to a silicone impression/adhesive system before and after gritblasting (GB) by peel-off test. CAD-designed experimental test blocks were printed by FDM using acrylonitrile butadiene styrene (ABS), polyethylene terephthalate glycol copolyester (PETG), and high impact polystyrene (HIPS), and the reference test blocks were made of a conventional light-curing resin (n = 11). Before and after GB, the surface topography of all tray materials was analysed, and the maximum strength of the test block peeled off from a silicone impression/adhesive system was measured. After GB, the arithmetic mean height (Sa) and the valley fluid retention index (Svi) of the four material groups declined (p < 0.05). The peel-off strength of each of the four material groups significantly decreased by GB (p < 0.05), but no statistical difference could be found among them before or after GB. In all peel-off tests, adhesive failure occurred at the adhesive-impression material interface. The results indicated ABS, HIPS, and PETG could provide sufficient adhesion to the adhesive as the conventional light-curing resin, and GB could reduce the roughness generated by FDM and weaken the bonding between the adhesive and the silicone impression.

Objects build orientation, positioning, and curing influence dimensional accuracy and flexural properties of stereolithographically printed resin

OBJECTIVE To evaluate the influence of printing parameters on flexural properties and accuracy of SLA-printed standard objects. METHODS Thirty specimens were printed in 0°, 45° and 90° orientation. Fourth nine more specimens were printed evenly on the build platform. forty more specimens were printed and polymerized with three curing unit. Length, height and width was measured three times for each specimen and compared to the original dimensions. Afterwards all specimens underwent a three-point-bending test to assess their flexural properties. One way ANOVA and the Post-Hoc all pairs Tukey-Kramer HSD test were used for data evaluation. RESULTS The print orientation influences the printing accuracy. The parameters printed along the Z-axis are particularly prone to inaccuracies. Specimens with 45° orientation were found to be the most accurate. Object printed on the borders of build platform a rather prone to inaccuracies than those in the center. The 90° specimens with layer orientation parallel to the axial load showed the superior flexural strength and flexural modulus. The use of different curing unit is unlikely to affect the objects printing accuracy and flexural properties. SIGNIFICANCE The anisotropical behavior of printed specimens with regards to build orientation and positioning was revealed. The understanding of how the adjustable printing parameter influence the printing outcome is important for a precise fabrication of surgical guides. Inaccuracies up to 10% along the Z-axis, as revealed in the present study,may restrict an accurate implant placement.

Influence of Different pH and Fluoride Addition on the Corrosion Behavior of the Sintered CoCr Alloy Ceramill Sintron Compared to the Cast Alloy Girobond NB

In addition to conventionally casting, dental metallic framework can be manufactured using different CAD/CAM technologies (selective laser melting, milling). The milling of porous CoCr blanks followed by sintering under protective gas is a new 2012 introduced dental technology called Ceramill Sintron. For this new material so far, there exist few studies on the corrosion behavior. The aim of this study was to investigate the influence of different pH values as well as fluoride additions on the corrosion behavior of the sintered CoCr alloy compared to the cast condition by electrochemical corrosion measurements according to ISO 10271.