Search

Search Results

• Comparative Study of Surface Treatment Procedures for Dental Implants

  12-32

  Alexandra Bereczki

  Péter Ficzere

  Views:

  271

  Nowadays, the most common type of implant in dentistry is a partial tooth replacement, such as a crown, or a complete tooth replacement. Today, many manufacturers offer implants made of a wide variety of materials and designs. These restorations must meet strict standards, one of the most stringent being surface roughness. Since proper bone-to-implant contact only occurs with adequate surface roughness, several methods are used to achieve the correct value. After reviewing the results of experiments carried out by several research groups, it is concluded that the surface roughness, the shape of the implant fixation screw, the shape of the thread and the thread elevation used to achieve the desired roughness together determine the success of the implantation. The average surface roughness required for osseointegration is considered to be optimal for values between 1 and 100 µm. In most cases, the surface roughness of commercially available dental prostheses is Ra 1-2 µm, but this can be modified by various grinding, acid etching and polishing processes to suit the application. Acid etching is a common technique for roughness reduction, which is the most effective in reducing surface roughness of dental restorative materials (mostly titanium alloys), thus bringing the roughness within the desired range. The result of acid etching is influenced by the concentration of acid, the temperature of the acid bath and the time spent in the acid. The acid used for the surface treatment is important and is most commonly sulphuric acid, hydrochloric acid or hydrogen fluoride (HF) and combinations of these. The study shows that the most optimal results are obtained with HF. Replacements are nowadays largely made by additive manufacturing, which allows for customised replacements and, due to dimensional accuracy, reduces the time and cost of post-processing, i.e. the surface treatment can be used to achieve the desired surface roughness and size at the same time. As a result, newer materials are being used for clinical prostheses and surface treatment should be applicable to all materials. The most optimal solution is a combination of grit blasting and acid etching. With this technology, the surface roughness for all materials reaches the optimum value of 1-100 µm, sometimes 1-2 µm, but can be further reduced below 1 µm by polishing. The study investigates the role of surface roughness, the surface roughness should only be reduced up to a certain value, approximately 0.5 µm, as smooth surfaces have limited or no potential for osseointegration.

• Study of Rotating and Jet Plasma Treatments on Surface Wettability of Glass

  67-79

  Miklós Berczeli

  Zoltán Weltsch

  Views:

  70

  This work investigates the wettability properties of a glass surfaces by using atmospheric pressure cold plasma systems. Treatments were performed by using a rotating-head unit and a jet-type torch during the plazma treatments. The nozzle-to-surface distance (8–15 mm) and the feed rate (50–400 mm/s) were modifying. The untreated glass showed limited wetting, with average water and ethylene glycol contact angles (WCA and EGCA) of 64.7° ± 1.8° and 45.2° ± 1.5°, respectively. After plasma treatment, both systems showed clear improvements, although their efficiency profiles were different. Using the rotating plasma head at 8 mm and 100 mm/s speeds, the WCA decreased to 9.3° ± 0.8°, indicating almost complete wetting. Jet plasma achieved similar results (WCA = 14.1° ± 1.2°), but slightly less uniformly. Changes in wettability were closely related to the exposure time determined by the feed rate: slower movement increased activation, while overexposure occasionally resulted in small thermally induced surface marks that were visible under an optical microscope. As the results showed the rotating plasma reached more homogeneous activation, while the jet system provided stronger local effects at a lower energy input. Based on these results the atmospheric plasma is effective in increasing the surface energy. Rotating systems appear to be advantageous for large, flat areas, while jet plasma is better suited for localized surface modification aimed at improving adhesion or coating performance.