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Endodontic retreatment with direct crown access is the main choice in cases of endodontic treatment failure, even if the practitioner`s effort and duration is significantly greater compared with other procedures. The retreatment with crown access repeats root canal treatment through direct access at the level of tooth crown. The objective is to clean up the canal from irritant agents, such as microorganisms, surviving from the previous therapy or passed through afterwards. Thus, a treatment restart is in accordance with the logics of root canal therapy and is preferred at any time if possible. The aim of this study was to observe, over a 4-year span, the efficiency of endodontic retreatment with direct coronary approach. From 2012 to 2016, 148 patients, with ages ranging from 18 to 65 years, were retreated endodontically. All patients were included in a regular monitoring plan of 3 months and 1-year post treatment. X-rays were performed during these observations, assessed with Orstavik criteria (1991), each radiography having assigned a periapical index (PeriApical Index – PAI). In conclusion, this study confirms that first choice of retreatment in case of endodontic treatment failure is restarting of the retreatment with direct crown access (91% success rate), failure of which leads to a surgical approach using endodontic microsurgery techniques.

Due to the lower opacity and translucency of many core materials, bilayered ceramic crowns were introduced to obtain sufficient veneer support and to improve aesthetics. Interfaces can have significant influence on the mechanical performance of layered structures. Veneer chipping and zirconia frameworks fractures are critical issues in all-ceramic restorations. The objective of this study was to assess failure analysis of bilayered all-ceramic molar crowns, evidenced by different type of fractures. Experiments were conducted on a right first maxillary molar. Bilayered all-ceramic crowns were obtained with a 0.5 mm thick zirconia milled framework and veneered with hot-pressed ceramics. The specimens were tested at compressive load until failure. The typical macroscopic crack pattern of all samples showed that crack propagation resulted in more broken pieces with sharp edges. Ceramic materials show considerable variation in strength due to their extreme sensitivity to cracks. Understanding the fracture behavior of dental ceramics and its relation to different materials and restorations is important from a clinical point of view.

Technological developments in the field of based metal alloys have led to the implementation of novel manufacturing processes in dental practice. The aim of the study was to evaluate surface characteristics of Co–Cr dental alloys fabricated via conventional casting, computerized milling, selective laser sintering and selective laser melting. The morphology and the topography of the samples were investigated by SEM / EDAX (Model INSPECT S) and AFM (Model Nanosurf® EasyScan 2 Advanced Research). Depending on the nature and chemical composition of the samples the morphology is different. The microstructure of Co–Cr dental alloys depends on the manufacturing technique. Given to the differences in microstructural properties among the tested specimens, further differences in their technological achievement and clinical behavior can be anticipated.

Magnesium and its alloys are one of the most used materials for bone implants and tissue engineering. They are characterized by numerous advantages such as biodegradability, high biocompatibility and mechanical properties with values close to the human bone. Unfortunately, the implant surface must be adequately tuned, or Mg-based alloys must be alloyed with other chemical elements due to their increased corrosion effect in physiological media. This article reviews the clinical challenges related to bone repair and regeneration, classifying bone defects and presenting some of the most used and modern therapies for bone injuries, such as Ilizarov or Masquelet techniques or stem cell treatments. The implant interface challenges are related to new bone formation and fracture healing, implant degradation and hydrogen release. A detailed analysis of mechanical properties during implant degradation is extensively described based on different literature studies that included in vitroand in vivotests correlated with material properties’ characterization. Mg-based trauma implants such as plates and screws, intramedullary nails, Herbert screws, spine cages, rings for joint treatment and regenerative scaffolds are presented, taking into consideration their manufacturing technology, the implant geometrical dimensions and shape, the type of in vivoor in vitrostudies and fracture localization. Modern technologies that modify or adapt the Mg-based implant interfaces are described by presenting the main surface microstructural modifications, physical deposition and chemical conversion coatings. The last part of the article provides some recommendations from a translational perspective, identifies the challenges associated with Mg-based implants and presents some future opportunities. This review outlines the available literature on trauma and regenerative bone implants and describes the main techniques used to control the alloy corrosion rate and the cellular environment of the implant.

The purpose of this study was to evaluate the biodegradability of some magnesium alloys, different both from the point of view of chemical composition and different system (Mg-Ca, Mg-Zn-Ag). Microstructural characteristics of experimental magnesium alloys were investigated using optical microscopy and scanning electron microscopy coupled with energy dispersive X-ray. The hydrogen evolution was analyzed using the method proposed by Song. The assessment was made through the evaluation of hydrogen released rate in simulated body fluid (SBF) as proposed by Kokubo and his colleagues, maintaining the temperature at 37 °C, for 240 hours. The studied samples showed different degradation rates depending on the chemical composition of magnesium based alloys and function of immersion time.

Bone cement has been used for over half a century, to successfully anchor artificial joints. From its emergence there have appeared a number of types of bone cement, with the 2 major classes being bone cement with or without active substances. The one with the added antibiotics is used primarily in the treatment and revision surgery of infected total hip arthroplasty (THA), as well as a prophylactic method in primary THA in patients with high risks for this complication. The purpose of this study is to determine the mechanical properties of bone cement with added antibiotics. Over a period of 2 years, a number of 41 cases were chosen for this study: 25 with revision surgery for THA, where bone cement with antibiotics was used, and 16 with primary THA, where regular bone cement was used. A number of studies have been performed on the mechanical properties of the 2 types of cement, which determined that the cement with antibiotics presents a slightly lower compressive strength, tensile strength, elastic modulus and fatigue strength compared with regular cement. These variations, however, become more pronounced as the quantity of the antibiotic goes up. The mechanical properties of the cement with antibiotics are similar with those of the regular cement, when low doses of antibiotics are used and become more evident as the doses go up. In conclusion, the antibiotic bone cement is a trustworthy tool in the surgeon’s arsenal against infection, with minimal detriments from the mechanical view.

Removable dentures aim to improve masticatory function, esthetics and phonetics. Different materials have been used as denture base materials but poly(methyl methacrylate) (PMMA) is most frequently used in most countries. Surface related properties of denture base materials (roughness, surface free energy, wettability, hydrophobicity, etc.) are of clinical importance since they affect plaque accumulation and staining. Surface roughness specifically influences the adhesion and retention of Candida Albicaans, which has a particular importance in denture-induced stomatitis pathogenesis. Bacterial plaque retention directly affects oral hygiene even if the patient achieves an appropriate cleaning of the denture. Ideally, denture base materials should be smooth so plaque adherence is reduced or even avoided. Test specimens of four heat polymerized materials were obtained by a classical press-pack dough molding technique of 1.5 mm thick wax-plate flasked in class III Moldano followed by the recommended polymerization regime. One of the materials was processed through a fast polymerization cycle. Injection-type materials were automatically produced using a dedicated injection unit. All plates were sectioned in 10 mm x 10 mm samples. No finishing protocol was applied. The selected specimens were examined under field emission scanning electron microscope (SEM). A large variation of surface topography was recorded between materials. There were visual differences between the four heat polymerized resins but also between the two injection-type materials. Surface topography was also influenced by the polymerization regime. Within the limitations of our study, we found that surface topography is influenced by the chemical composition of each material, the heat cure cycle and the processing method.

Advanced technologies and biocomplexity offer new dimensions for the development of novel medical products obtained from marine resources. Because several biomaterials can be derived from synthetic or natural sources, this area offers a very large variety of natural species that may be used for biomedical applications, including tissue engineering, drug delivery and surgery. The marine environment is a natural collector of porous materials the porosity of which varies from submicron to millimeter. The production of hydroxyapatite from synthetic chemicals can sometimes lead to a costly work and sea creatures may represent an alternative way to produce very fine and even nano-structured biomaterials. Rapana venosa is, in this sense, a study marine organism because its shell is made of aragonite that can be converted into bioceramic powder, which can subsequently be used for biomedical applications. The indirect use of marine organisms was tackled according to different routes: synthetic precursor casts using biomorphic moulds, chemical conversion of the inorganic marine matrix into a biomorphic substitute, and self-assembly of nanoparticles via chemical and molecular interactions. The chemical conversion is the most developed practice to obtain biomaterials for bone regeneration. It can be realized by hydrothermal synthesis or hydrothermal hot pressing. Both methods suppose a pre-treatment to remove the organic matrix of the skeleton. Hydrothermal synthesis involves heating the marine skeletons under alkaline conditions at a specific temperature pressure in either a reaction vessel or an autoclave. The temperature and pressure have an important significance concerning material structure properties of final product in terms of degree of crystallinity, grain size, and specific surface area. The temperature has an importance on the crystallite size (50-150 nm), and in general, the optimal temperature ranges between 200-250°C. Hydrothermal hot pressing is the process used in the fabrication of some commercial bone substitutes from coral sources and involves the solidification of synthetic hydroxyapatite powder. Some experimental results related to the processing of Rapana venosa snail shell in order to obtain hydroxyapatite for medical applications are presented at the end. In conclusion, preliminary results obtained by us show that this snail shell appears to be suitable to be used as raw material for obtaining hydroxyapatite.

The purpose of our study was to compare the mechanical properties of the different abutment under the static loading, aspect treated by many researchers [1-4], especially following the improvements given by the new proposed three-piece abutment, described below. We evaluated the effect of compression loading on the screw joint stability of the two-piece abutment and a new proposed three-piece abutment connected to an internal hexagon implant in vitro.The dental implant used was type AlphaBio SPI with an internal hexagon shape with following dimensions: length 13mm and diameter 3.75mm. The two types of abutment were used: the common type consisting of two piece straight titanium abutment and the second type consisting of three piece abutment (two titanium pieces and the third piece made of UHMWPE). For two-piece titanium implant/abutment systems with a screw-retained connection, the respective prefabricated straight abutments were tightened with a torque gauge using titanium abutment screws (type M-TLA) according to the manufacturer’s instructions. In the second case, the first titanium piece was a connector base between the implant and the UHMWPE abutment body which is assembled all together with the implant abutment fixation screw. The experimental systems were positioned in bovine cortical bone with a central hole (3.75 mm in diameter), and mechanical characteristics were evaluated using mechanical tensile tests. The mechanical tensile tests were carried out using INSTRON 3382 tensile test equipment. All tensile tests were performed at a constant strain rate of 1mm/min until a maximum elongation of 4mm. Stress-strain tensile curves were obtained for each experimental system.There were significant differences in the case of using the system with three piece abutment and we could conclude that this type of abutment assure a lower pressing on the entire system due to the shock absorbent properties of the piece made by UHMWPE.

The present study was conducted with the aim of evaluating and comparing the microleakage at the dentin and enamel/composite interfaces of two adhesive systems. The adhesives are: a new-developed experimental adhesive systems and OptiBond FL (Kerr Corp.) The new adhesive system was prepared for the composite material as three steps adhesive (etchant, primer and bonding). The bonding resin contains the base monomer that was present in the corresponding composite material, HEMA and TEGDMA as diluents. Twenty box-type Class V standardized cavities were prepared on the facial and oral surfaces of each tooth, with coronal margins in enamel and apical margins in cementum (dentin). The preparations were restored with two restorative materials a new experimental microfilled resin composites based on Bis-GMA analogue and hybrid resin composite Herculite XRV Ultra (Kerr Corp.). The teeth were thermocycled and immersed in 2% methyl blue solution for 24 hours. The specimens were sectioned buccolingually into 3 slices and the resulted sections were examined using a stereomicroscope under 40x magnification. The extent of dye penetration was measured in a quantitative manner. This measurement was converted into percentage using the formula described by Sano et al. I=p/Lx100. These percentage values were submitted to variance analyses (ANOVA) and t test at a p<0.05 level of significance. Scanning electron microscopy was used in order to see the interface between tooth and composite restoration. Significantly less microleakage was associated with the use of OptiBond FL adhesive system at the enamel surface. Between the enamel and the dentin margins no significantly statistical differences were found just for the experimental adhesive system. This adhesive containing water and ethanol as solvent performed significantly better at the dentin margins.

This study evaluated the hydrolytic degradation of two experimental (C1, C2) and two commercial composite (Tetric EvoCeram and Premise) prepared to be used in dental restorations. Two experimental composites and two commercial composites were undergoing hydrolytic degradation in three different medium: distilled water, artificial saliva and alcoholic solution (50/50). The samples were investigated immediately after polymerisation with halogen lamp Optilux 501 and after 33 days of immersion in all three medium, using Fourier transforms infrared analysis (FTIR). FT-IR spectra of samples from the same composite immersed in distilled water, artificial saliva and alcoholic solution, revealed mostly reducing the intensity of the characteristic peaks of Si-O-Si bond less Tetric composite immersed in artificial saliva, which peak intensity remains unchanged.

Full ceramic crowns are considered revolutionary in developing the concept of aesthetic dentistry. Appreciate their aesthetic appearance particularly raise the cost prices, they do not ensure the risk of fractures and cracks which sometimes face the clinician after their insertion directly into the mouth. As a result of the fracture may occur between disputes team dentist-dental technician. The purpose of this study was to identify flaws of material included in the pottery table analyzing the full ceramic crowns using non-invasive technologies. As materials we use 25 full ceramic crowns (e. max, IVOCLAR) obtained through the technology of pressing were used for this study. Non-invasive methods used for this study were OCT and Micro CT. The OCT technology works in Time Domain, at 1300 nm and scan angle at 18 degrees, and for each sample scans were carried out in areas of maximum voltage. After the scans, we have been obtained through the stack of 500 slicers at a distance of 10 microns each other. A number of 17 samples of the total samples obtained exhibited defects in areas of major stress corresponding to the crown considered. As a result of defects discovered using the technology OCT it has considered necessary for validation them by employing the Micro CT technology. In conclusion, we consider that OCT technology can be considered an early diagnosis method of faults contained in the table structure of the ceramic crowns before inserting them in the oral cavity, by reducing the risks of a prosthetic treatment.

New materials are required for bone healing in regenerative medicine able to temporarily substitute damaged bone tissues and to be subsequently resorbed and replaced by endogenous tissues. Taking inspiration from the basic composition of the mammalian bones, composed of collagen, apatite and a number of substitution ions in it, among them magnesium (Mg2+), in this work, novel composite scaffolds composed of collagen(10%)-hydroxyapatite (HAp)(90%) and collagen(10%)-HAp(80%)-Mg(10%) were developed. The lyophilization was used for composites preparation. An insight into the nanostructural nature of the developed scaffolds was performed by SEM-EDX and TEM-EDX. The HAp nanocrystallite clusters and Mg nanoparticles were homogeneously distributed within the scaffolds and embedded into the collagen fibrils. The samples were tested for degradation in Simulated Body Fluid (SBF) solution by soaking for up to 28 days. The release of Mg from collagen(10%)-HAp(80%)-Mg(10%) composite during the period of up to 21 days was attested, this composite being characterized by a decreased degradation rate with respect to the composite without Mg. The developed composite materials are promising for applications as bone substitute materials favouring bone healing and regeneration.