Surface Modification of 3D Printed PLA Objects by Fused Deposition Modeling: A Review

Polylactic acid (PLA) filaments are very popular as a thermoplastic source used in the 3D printing field by the “Fused Deposition Modeling„ method in the last decade. The PLA market is expected to reach 5.2 billion US dollars in 2020 for all of its industrial uses. On the other hand, 3D printing is an expanding technology that has a large economic potential in many industries where PLA is one of the main choices as the source polymer due to its ease of printing, environmentally friendly nature, glossiness and multicolor appearance properties. In this review, we first reported the chemical structure, production methods, general properties, and present market of the PLA. Then, the chemical modification possibilities of PLA and its use in 3D printers, present drawbacks, and the surface modification methods of PLA polymers in many different fields were discussed. Specifically, the 3D printing method where the PLA filaments are used in the extrusion-based 3D printing technologies is reviewed in this article. Many methods have been proposed for the permanent surface modifications of the PLA where covalent attachments were formed such as alkaline surface hydrolysis, atom transfer polymerization, photografting by UV light, plasma treatment, and chemical reactions after plasma treatment. Some of these methods can be applied for surface modifications of PLA objects obtained by 3D printing for better performance in biomedical uses and other fields. Some recent publications reporting the surface modification of 3D printed PLA objects were also discussed

Diyot Lazerle Yapılan Ofis Beyazlatma Tedavisi Sonrası Ozon Uygulamasının Sınıf V Kavitelerde Mikrosızıntı Üzerine Etkisi

Objective: This study investigated the effect of ozone treatment on the microleakage of class V composite restorations after using two different bleaching agents with laser activation. Materials and Methods: Forty non-carious maxillary central incisor teeth extracted for periodontal disease were used and randomly divided into two main groups. Group 1: Bleaching agent including 40% H2O2 was activated with laser (Diode 980 nm, Gigaa Dental Laser Cheese, China). Group 2: Bleaching agent including 35% H2O2 was activated with the same laser. Then, the teeth were randomly divided into two subgroups (n=10). Ten specimens in each subgroup were subjected to ozone treatment (Ozonytron XP-OZ, MIO International, Germany) for 30 seconds, while the remaining left untreated/remainings were control group. After class V cavity preparation on the buccal surfaces, all cavities were filled with composite resin (Filtek Z550, 3M ESPE, USA). Following thermal cycling (5–55°C, 5000×), the specimens were subjected to dye penetration within 0.5% basic fuchsine for 24h. Then, the teeth were sectioned longitudinally to evaluate staining and the depth of staining along with the tooth-restoration interface was recorded with a stereomicroscope.  Results: There were no significant differences between the two bleaching agents in microleakage of restorations (p > 0.05). The ozone treatment didn’t decrease the microleakage values (p > 0.05). There were significant differences among the scores of microleakage at the enamel and gingival margins  (p < 0.05). Conclusion: Ozone treatment did not affect microleakage values of class V composite restorations after dental bleaching

Diyot Lazerle Yapılan Ofis Beyazlatma Tedavisi Sonrası Ozon Uygulamasının Sınıf V Kavitelerde Mikrosızıntı Üzerine Etkisi

Objective: This study investigated the effect of ozone pretreatment on the microleakage of class V composite restorations after using two different bleaching agents with laser activation. Methods: Forty non-carious maxillary central incisor teeth extracted for periodontal disease were included and randomly divided into two main groups (n=20). Group 1: Bleaching agent including 40% H2O2 was activated with laser (Diode 980 nm, Gigaa Dental Laser Cheese, China). Group 2: Bleaching agent including 35% H2O2 was activated with the same laser. Then, the teeth were randomly divided into two subgroups (n=10). Ten specimens in each subgroup were subjected to ozone treatment (Ozonytron XP-OZ, MIO International, Germany) for 30 s, while the remaining untreated specimens were left as control group. Class V cavities were prepared on the buccal surfaces and restored with composite resin (Filtek Z550, 3M ESPE, USA). Following thermal cycling (5–55°C, 5000×), the specimens were kept in 0.5 % basic fuchsine for dye penetration within a period of 24h. Then, the teeth were sectioned longitudinally. The depth of staining along with the tooth-restoration interface was examine under a stereomicroscope and recorded. Results: There were no significant differences between the two bleaching agents in terms of microleakage of restorations (p > 0.05). The ozone pre-treatment didn’t decrease the microleakage values (p > 0.05). Significantly higher microleakage scores were determined at gingival margins compared to occlusal margins (p 0,05). Ozon tedavisi mikrosızıntı değerlerini azaltmadı (p> 0,05). Okluzal marjinlerde, gingival marjinlere oranla anlamlı düzeyde daha fazla mikrosızıntı tespit edildi (p <0,05). Sonuç: Beyazlatma sonrası ozon tedavisi sınıf V kompozit restorasyonların mikrosızıntı değerlerini etkilemedi

Bir yüzbaşının gözünden Kıbrıs Barış Harekâtı

Ankara : İhsan Doğramacı Bilkent Üniversitesi İktisadi, İdari ve Sosyal Bilimler Fakültesi, Tarih Bölümü, 2015.This work is a student project of the The Department of History, Faculty of Economics, Administrative and Social Sciences, İhsan Doğramacı Bilkent University.by Özer, Abdürrahim

Salt-driven deposition of thermoresponsive polymer-coated metal nanoparticles on solid substrates

Here we report on a simple, generally applicable method for depositing metal nanoparticles on a wide variety of solid surfaces under all aqueous conditions. Noble-metal nanoparticles obtained by citrate reduction followed by coating with thermoresponsive polymers spontaneously form a monolayer-like structure on a wide variety of substrates in presence of sodium chloride whereas this phenomenon does not occur in salt-free medium. Interestingly, this phenomenon occurs below the cloud point temperature of the polymers and we hypothesize that salt ion-induced screening of electrostatic charges on the nanoparticle surface entropically favors hydrophobic association between the polymer-coated nanoparticles and a hydrophobic substrate