Search

The cyclic resistance of ProTaper Universal (size 25/08) and ProTaper Next (size 25/06) instruments was compared in artificial canals with different curvatures in this study. A total of 30 ProTaper Universal and 30 ProTaper Next instruments were divided into 6 groups (n = 10) and were operated into artificial canals with 3 different angles of curvature (45°, 60°, 90°). The canal length was kept consistent in this study. The number of cycles to fracture (NCF) was counted until file fracture occurred, at which point, the length of the fragment was measured. The data were analyzed statistically using ANOVA complemented by the Tukey test (p < 0.05). Cross sections of the fractured files were scanned by an electron microscope. In the fatigue test, the ProTaper Next displayed more resistance in 45° and 60° canals (p < 0.05), whereas ProTaper Universal exhibited a better operability in 90° canals (p < 0.05). The average length of the fragments from ProTaper Next was significantly shorter than that from ProTaper Universal in 90° canals (p < 0.05). The cross sections of the fractured surfaces became flatter when the curvature angles decreased from 90° to 45°. ProTaper Next was more reliable when shaping in curved canals, whereas ProTaper Universal was more sui for the preparation of root canals with severe curvatures.

Introduction and objective: Cast post and cores are an important tool in the reconstruction of a dental crown. This article analyzes the state of cast metallic posts, made of alloys with high silver content, in cases where the restoration failed. Our aim is to point out the risks associated with the use of these alloys. Material and methods: A group of patients, based on a variety of dental indications, to whom it was necessary to extract either teeth with cast post and core or remove cast metallic posts or crowns. Overall, we analyzed 23 prosthetic works that have been exposed to the oral environment for 10 to 29 years, and discuss seven cases with a known history. The state of extracted samples was investigated by scanning electron microscopy and the elemental composition was determined by X-ray energy dispersive analysis (EDS / EDAX). Results and conclusion: The analysis showed that the corrosion problems of cast post and cores relate to the inner wire component as well as cast metallic post. In a situation when the corrosion environment penetrates to the core area, the corrosion process can lead to the formation of bulky iron corrosion products or ions of soluble silver compounds. This results in a strain, which may cause a longitudinal fracture of the tooth root and tissue pigmentation. Since alloys with high silver content are still part of the inventory of dental laboratories and the silver-tin alloy is still offered in the dental market, we felt it nece-ssary to highlight the risk aspects associated with manufacturing root extensions from these materials.

Background: The second part of the literature review on the biocompatibility of dental alloys is focused to their possible sensibilizing effects, mutagenicity and carcinogenicity and the methods of their testing. The condition of an allergic reaction to the metal alloy is releasing its components (metal ions) by corrosion processes. From the general mechanisms of allergic reactions is well known that metal ions alone can not be allergens. However, they may play a role of haptens, where they bind to certain body molecules (proteins, nucleic acids, carbohydrates) or modified. Tests allergenic properties of metals can only be performed in vivo, in animals or humans, and commonly used patch tests are both far from the situation in the mouth, and secondly, their explanatory power is ambiguous. It is often difficult to determine whether an inflammatory reaction to the metal ions is mediated by allergic mechanism or is a toxic reaction, or combination of both mechanisms. Mutagenicity is usually tested in bacterial cultures and carcinogenicity in long-term exposure studies in laboratory animals. Direct evidence of mutagenicity and carcinogenicity of the real dental alloys are not available, however potential of some metals from dental alloys in this regard this admits. Alloys for dental amalgams have among the other dental alloys exceptional position in the evaluation of their biocompatibility,w as the usual tests address the final product, ie dental amalgam, which is produced by mixing the alloy powder with mercury under specified conditions. The vast majority of studies dealing with the corrosive properties of amalgam, its biocompatibility and methods of testing is therefore focused on the impact of mercury release. Technical standards EN ISO 10993 together with EN ISO 7405, regarding the evaluation of biocompatibility of medical devices and therefore dental alloys give a set of tests, the implementation of which should be considered before a new product is introduced into use. The results of these preclinical tests in vitro and in vivo have only limited value and can not replace long-term clinical experience.

Background: Dental alloys are widely used in applications where they come for a long time into contact with oral epithelium, connective tissue or alveolar bone. Hence their biocompatibility is one of the critical requirements for use in clinical dentistry. This review of literature is intended as an overview of the risk exposure of the human body to metals from dental alloys and the possibility of examining the model conditions in vitro and in vivo before placing them on the market and put into use. Dental alloys are metallurgically complex ones and with regard to their composition. They are divided into gold, silver and palladium based alloys and non-precious alloys (cobalt, chromium, nickel). Crucial features of alloys in terms of their biocompatibility are their corrosion properties. The individual components of alloys released into the oral environment and the organism due to the in situ corrosion processes can cause local and systemic toxicity, and therefore it is necessary the alloys in the preclinical stage to properly investigate. Attention is focused especially on local toxicity, since systemic toxicity from dental alloys has not been demonstrated. Standard contact cytotoxicity tests whether performed in vitro in cell cultures or in vivo in laboratory animals simulate the situation in the clinical use only partially, and therefore it is necessary to take into consideration the general toxicological properties of the individual metals in dental alloys. Conclusion: In the first part of the literature review of the dental alloys biocompatibility and its testing the data gained from the last fifteen to twenty years are summarized.

Copyright of Journal of Zhejiang University: Science B is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of the present study is to analyze the electrochemical behavior of five different dental alloys: two cobalt-chromium alloys (CoCr and CoCr-c), one nickel-chromium-titanium alloy (NiCrTi), one gold-palladium alloy (Au), and one titanium alloy (Ti6Al4V), and the galvanic effect when they are coupled to titanium implants (TiG2). It was carried out by electrochemical techniques (open circuit measurements, potentiodynamic curves and Zero-Resistance Ammetry) in artificial saliva (AS), with and without fluorides in different acidic conditions. The studied alloys are spontaneously passivated, but NiCrTi alloy has a very narrow passive domain and losses its passivity in presence of fluorides, so is not considered as a good option for implant superstructures. Variations of pH from 6.5 to 3 in artificial saliva do not change the electrochemical behavior of Ti, Ti6Al4V, and CoCr alloys, and couples, but when the pH of the artificial saliva is below 3.5 and the fluoride content is 1000 ppm Ti and Ti6Al4V starts actively dissolving, and CoCr-c superstructures coupled to Ti show acceleration of corrosion due to galvanic effects. Thus, NiCrTi is not recommended for implant superstructures because of risk of Ni ion release to the body, and fluorides should be avoided in acidic media because Ti, Ti6Al4V, and CoCr-c superstructures show galvanic corrosion. The best combinations are Ti/Ti6Al4V and Ti/CoCr as alternative of noble gold alloys. [ABSTRACT FROM AUTHOR]

Background: This study aimed to assess and compare the shear bond strength of self-etch and self-adhesive resin cement to nickel-chromium-cobalt alloy with different surface treatments. Materials and Methods: In this in vitro study, a total of 120 disks were fabricated of VeraBond II base metal alloy. Specimens were divided into 15 groups of 8 based on the type of cement and surface treatment. The five surface treatments studied included sandblasting alone, application of Alloy Primer with and without sandblasting, and application of Metal Primer II with and without sandblasting. The three cement tested included Panavia F2.0, RelyX Unicem (RU), and G-Cem (GC). After receiving the respective surface treatments, the specimens were thermocycled for 1500 cycles and underwent shear bond strength testing. Data were analyzed using SPSS 20.0 and three-way analysis of variance. P values of the significant level of 0.05 were reported. Results: The results exhibited that the mean bond strengths in sandblasted groups were higher than nonsandblasted one. These differences were significantly higher in the sandblasted groups of Panavia F2.0 and RU cement (P < 0.05).The mean bond strength values between GC and Panavia F2.0 were not statistically significant (P > 0.05). The highest bond strength was recorded for Panavia F2.0 with the surface treatment of both sandblasting and Metal Primer II. Conclusion: Based on the results, sandblasting improves the shear bond strength of self-etch and self-adhesive resin cement to base metal alloys. The best results can be achieved with a combination of sandblasting and metal primers. The performance of resin cement depends on to their chemical composition, not to the type of system. [ABSTRACT FROM AUTHOR]

Background and Aims: Poor adhesion between porcelain and some of the dental alloys is one of the most challenges to select the desirable alloy in dental restorations. Therefore, the aim of this study was to evaluate the bond strength of porcelain to some of the commercial alloys. This can help in selection of desirable alloy. Materials and Methods: The shear bond strength of porcelain to the three of the most widely used nickel-base dental alloys commercially named as: Verabond, Damcast and Noritake were evaluated according to standard ASTM E4. The results were analyzed based on the statistical method of independent t with the meaningful level of P<0.05. Then, the bonding interface of the fired samples was evaluated using SEM equipped with EDX analyzer and X-ray diffractometry. Results: The average bonding strength of porcelain to each of the above mentioned alloys were determined as: 27.545.48, 22.464.99 and 26.184.27 MPa, respectively. Due to the existence of Be and Al in the chemical composition of Verabond and Damcast and their higher appetencies to form the different surface oxides in preference to Cr2O3, not only the bond strength of porcelain to two these alloys was increased about 20 percent (compared with the Noritake), but also the color of their porcelain was not changed. Conclusion: To replace the replacing of deleterious elements from the chemical composition of dental alloys. The added new elements should control through the oxide layer and the formation of Cr2O3 in porcelain-alloy interfaces for adequate bond strength. [ABSTRACT FROM AUTHOR]

Background and Aims: Poor adhesion between porcelain and some of the dental alloys is one of the most challenges to select the desirable alloy in dental restorations. Therefore, the aim of this study was to evaluate the bond strength of porcelain to some of the commercial alloys. This can help in selection of desirable alloy. Materials and Methods: The shear bond strength of porcelain to the three of the most widely used nickel-base dental alloys commercially named as: Verabond, Damcast and Noritake were evaluated according to standard ASTM E4. The results were analyzed based on the statistical method of independent t with the meaningful level of P<0.05. Then, the bonding interface of the fired samples was evaluated using SEM equipped with EDX analyzer and X-ray diffractometry. Results: The average bonding strength of porcelain to each of the above mentioned alloys were determined as: 27.545.48, 22.464.99 and 26.184.27 MPa, respectively. Due to the existence of Be and Al in the chemical composition of Verabond and Damcast and their higher appetencies to form the different surface oxides in preference to Cr2O3, not only the bond strength of porcelain to two these alloys was increased about 20 percent (compared with the Noritake), but also the color of their porcelain was not changed. Conclusion: To replace the replacing of deleterious elements from the chemical composition of dental alloys. The added new elements should control through the oxide layer and the formation of Cr2O3 in porcelain-alloy interfaces for adequate bond strength. [ABSTRACT FROM AUTHOR]

BACKGROUND: Magnesium alloy is a material that is easily degradable and has good mechanical properties. OBJECTIVE: To study the effects of the two kinds of magnesium alloy materials (AM50 and WE43) on proliferation and morphology of human umbilical vein endothelial cells. METHODS: Human umbilical vein endothelial cells at logarithmic phase were cultured in 100%, 50%, 10% extracts of AM50 and WE43 or directly seeded on the surface of AM50 and WE43 for 24 hours to study the morphological effect of magnesium alloys on the cells. Human umbilical vein endothelial cells cultured routinely served as negative controls. Relative growth rate of the cells was detected at 12, 24, 48 hours after culture. Cell morphology was observed using immunofluorescence staining at 24 hours after culture, and pH and element levels in the cell supernatant were measured. RESULTS AND CONCLUSION: (1) AM50 and WE43 extracts showed no effects on the proliferation of human umbilical vein endothelial cells in comparison with the negative control group. (2) Compared with the negative control group, reduced area of human umbilical vein endothelial cells was found on the surface of AM50 or WE43 alloy by the immunofluorescent staining, and the cytoskeleton of the cytoplasm was blurred. However, after 24 hours of culture, morphological changes of the cells cultured in 10%, 50% and 100% AM50 or WE43 extracts were consistent with those cultured routinely. The cytoskeleton of the cytoplasm was clearly visible. (3) Compared with the negative control group, the pH values of 100% AM50 and WE43 extract groups were significantly upregulated, and the level of magnesium element was also increased remarkably. In summary, AM50 and WE43 alloys possess good cytocompatibility with human umbilical vein endothelial cells, and have no influence on the cell proliferation and growth. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of the study was to evaluate corrosion resistance of Wirobond C® alloy after chemical passivation treatment. Methods: The alloy surface undergone chemical passivation treatment in four different media. Corrosion studies were carried out by means of electrochemical methods in saline solution. Corrosion effects were determined using SEM. Results: The greatest increase in the alloy polarization resistance was observed for passive layer produced in Na2SO4 solution with graphite. The same layer caused the highest increase in corrosion current. Generally speaking, the alloy passivation in Na2SO4 solution with graphite caused a substantial improvement of the corrosion resistance. The sample after passivation in Na2SO4 solution without graphite, contrary to others, lost its protective properties along with successive anodic polarization cycles. The alloy passivation in Na3PO4 solution with graphite was the only one that caused a decrease in the alloy corrosion properties. The SEM studies of all samples after chemical passivation revealed no pit corrosion - in contrast to the sample without any modification. Conclusions: Every successive polarization cycle in anodic direction of pure Wirobond C® alloy enhances corrosion resistance shifting corrosion potential in the positive direction and decreasing corrosion current value. The chemical passivation in solutions with low pH values decreases susceptibility to electrochemical corrosion of Co-Cr dental alloy. The best protection against corrosion was obtained after chemical passivation of Wirobond C® in Na2SO4 solution with graphite. Passivation with Na2SO4 in solution of high pH does not cause an increase in corrosion resistance of WIROBOND C. Passivation process increases alloy resistance to pit corrosion. [ABSTRACT FROM AUTHOR]

Cobalt-based metal alloys are often used in dentistry for prosthetic restorations because of their considerable wear and corrosion resistance. For this reason, the effect on the human body of three Co–Cr based alloys, named "Co–Cr", "C" and "L", differing in their concentrations, for subsequent use as dental materials, has been studied and compared. Metallographic observations of the microstructure, electrochemical and three-point bending tests were performed. The metallographic investigations showed similar dendritic microstructure of the Co–Cr and L dental alloys, as well similar porosities and defects. From the corrosion and pitting potential tests, it was found that the samples show surface passivation, reaching closed corrosion potential values from −0.280 V vs SCE to −0.250 V vs SCE. The Pitting Resistance Equivalent Number (PREN) values are above 38 for all the samples, which means that the studied alloys have a high resistance to pitting corrosion. Likewise, when applying the Electrochemical Impedance Spectroscopy technique, a slightly higher corrosion resistance was observed for sample L, since corrosion resistance tends to increase as the applied potential is more positive and as the impedance and phase angle values are higher. Moreover, in the three-point bending test, the alloy C presents the lowest values of the elastic modulus of 134 ± 13 GPa. The analyzed Co–Cr alloys are recommended for the efficient treatment of patients with dental prostheses that have metal frameworks, as shown by all of the obtained results. • Dental alloys undergo spontaneous passivation due to a passive film on their surface. • The passive potential range is large and the samples showed a good pitting corrosion resistance. • The thickness of the passive film increases with the potential, with a capacitive response over a wide frequency range. • Young's modulus was lowest for tungsten-rich sample with 3 points bending test. [Display omitted] [ABSTRACT FROM AUTHOR]

Introduction: The objective of this study was to determine and compare the moment-to-force (Mc/F) ratio and the type of tooth movement generated in the anterior and posterior segments in orthodontic space closure with stainless steel and titanium-molybdenum alloy loop archwires., Methods: Three-dimensional model of the maxilla from which the first premolar was extracted, 18 × 25-mil slot stainless steel brackets, and 16 × 22-mil stainless steel and β titanium-molybdenum alloy (TMA) closing loop archwires with anterior gable bend of 15° and posterior gable bend of 25° were constructed. The archwires were engaged in the brackets, and 1-mm activations were carried out, which were repeated 5 times. The anterior and posterior segment Mc/F ratio and the type of tooth movement generated by the 2 wires were compared., Results: It was found that the Mc/F ratio for the anterior segment was approximately 5 mm, and for posterior teeth was approximately 10 mm for both stainless steel and TMA closing loop archwire. The anterior teeth exhibited controlled tipping, whereas the posterior teeth showed bodily tooth movement, which was in accordance with the Mc/F ratio that was obtained., Conclusions: The Mc/F ratio and the type of tooth movement exhibited by stainless steel and TMA closing loop archwires were similar in both anterior and posterior segments., (Copyright © 2023 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

This study evaluated a method to determine the spatial geometry of root canal preparation (RCP) using navigation dynamics and a specific algorithm from a new CBCT software (e-Vol DX). CBCT scans of 168 root canals of mandibular molars were acquired before and after RCP, using nickel-titanium (NiTi) instruments (ProTaper Next, BioRace, Reciproc Blue, and WaveOne Gold). The spatial geometry of the root canals and the operative risk of disproportional wear of dentinal walls after RCP were evaluated using a new CBCT software. A 3-point scoring system was used after the measuring of cementum/dentin thickness before and after RCP in all root thirds. The root thirds were distributed into three parts of similar sizes, and the scores were categorized at three levels: 1. mild risk (1/3), 2. moderate risk (2/3), 3. severe risk (3/3). These levels were proposed according to the risk of creating disproportionate shapes, thin walls, or perforations. The data were analyzed statistically by Fischer's exact test (α = 5%). There were no significant differences in operative risk among the NiTi engine-driven systems, for the distal or mesial walls of all the root canal thirds (p>0.05). The spatial geometry method to assess operative risk allows clinical planning for a predictable enlargement of the root canal in all root thirds. Based on using a map-reading strategy on root canals in CBCT scans, NiTi engine-driven instruments did not present an increased operative risk during RCPs.

Background: The purpose of the current in vitro study was to evaluate the surface roughness and hardness of three brands of as-received esthetic coated NiTi archwires and compare them with the same parameters after immersion in artificial saliva., Methods: Three groups of 0.016 × 0.022 inch epoxy-coated NiTi orthodontic wires [Tooth tone coated NiTi (Ortho Technology, West Columbia, USA), EverWhite NiTi (American Orthodontics, Wisconsin, USA) and Nitanium Super Elastic Tooth Tone Plastic coated (Ortho Organizers, San Marcos, CA, USA)] were compared. Each group was subdivided into five as-received archwire specimens and five archwire specimens retrieved following immersion in artificial saliva for 28 days. Atomic force microscopy was used for analysis of average surface roughness (Sa). Hardness testing was performed using Digital Vickers hardness tester. ANOVA and Kruskal-Wallis tests were used for comparing the wire groups., Results: The ranking of (Sa) values was as follows: Nitanium Ortho Organizers > Everwhite American Orthodontics > Tooth tone Ortho Technology (P > 0.05). Nitanium Ortho Organizers archwires showed significantly greater (Sa) than both other groups following immersion in saliva (P < 0.001). The coating hardness of as-received and post-immersion archwires from Tooth tone Ortho Technology was significantly lower than the other groups (P < 0.001). For all the three types of archwires, the mean hardness of immersed wires was significantly lower than that of the as-received archwires (P < 0.001)., Conclusions: Esthetic coated archwires have shown unpleasant surface changes following exposure to artificial saliva. These surface changes are affected by physical characteristics such as surface roughness and hardness of the coating., (© 2023. The Author(s).)

The present work describes green-mediated copper oxide nanoparticles as a potential corrosion inhibitor for the dental alloy Ti-6Al-4V. The salt of copper was reduced to metal nanoparticles using Murraya koenigii leaves, which helps with the agglomeration and nanocluster formation through a reduction mechanism. The current synthesis is a single-step process and is cost-effective. The synthesized nanoparticle was characterized using UV, FTIR, XRD, Zeta potential and Particle size analyzer, SEM, and EDX. The particles were then electrodeposited on Ti-6Al-4V alloy, and the corrosion resistivity in the dental medium was analyzed using Electrochemical parameters such as Corrosion current, Corrosion potential, and anodic and cathodic intercepts through the Tafel and Nyquist plots. The synthesized nanoparticles showed characteristic absorbance at 359 nm. FTIR peaks confirm the phytochemical constituents present in the Murraya koenigii that accounts for the formation of nanoparticles. The XRD predicts the crystalline nature, which is further studied using SEM and EDX. The Zeta potential and Particle size analyzer confirms the negative-negative interactive nature of the synthesized CuO NPs. The NPs showed explicit corrosion inhibition properties with an overall inhibition efficiency of 58.15% and 25.6%, respectively. The study confirms the advantage of using Copper Oxide nanoparticles as a potential coating agent in dental implant alloys in increasing its corrosion efficiency., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Background: Rotary nickel-titanium (NiTi) instruments are made to exacting standards and are costly to manufacture, and quality control is paramount. Consequently, unauthorized factories make counterfeit instruments that are less expensive and may therefore be attractive to dentists. Little information exists about the metallurgy and manufacturing quality of such instruments. There is the potential for counterfeit instruments to be at higher risk of fracture during treatment, thereby compromising clinical outcomes. The aim of this study was to evaluate physical and manufacturing properties of genuine and counterfeit ProTaper Next™ and Mtwo® rotary NiTi instruments., Methods: This study investigated the metallurgical properties, manufacturing quality, microhardness and number of cycles to failure of two commonly used rotary NiTi systems and compared them with counterfeit products purporting to be genuine articles., Results: Counterfeit instruments were found to be inferior in manufacturing standards and were less resistant to cyclic fatigue when compared to genuine instruments., Conclusions: Counterfeit rotary NiTi instruments may be less efficient at preparing root canals and may be at higher risk of fracture during endodontic treatment. Dentists must be aware that, although less expensive, counterfeit instruments may be of dubious manufacturing quality and at higher risk of fracture if used in patients. © 2023 Australian Dental Association., (© 2023 The Authors. Australian Dental Journal published by John Wiley & Sons Australia, Ltd on behalf of Australian Dental Association.)

Objectives: To compare between two archwire (AW) sequences in terms of alignment speed and root resorption (RR)., Materials and Methods: Fifty-four patients (14 males, 40 females) requiring orthodontic treatment were randomly allocated into two groups; in group A (mean age 18.3) treatment started with 0.014″ nickel titanium (NiTi) followed by 0.019″×0.025″ NiTi AW while group B (mean age 18.9) the AW sequence was 0.014″ NiTi, 0.018″ NiTi, 0.016″×0.022″ NiTi, 0.019″×0.025″ NiTi. The primary outcome was to compare the alignment speed of the crowded upper and lower teeth between the two different AW sequences. The secondary outcome was to assess the magnitude of upper and lower incisors' root resorption (RR) measured by digital periapical radiographs taken at the start of treatment and 1 month after the placement of the working AW. t-test was used to compare the alignment speed and RR between the two groups. Statistical significance was predetermined at the P ≤ 0.05 level for all tests., Results: The 54 patients were randomized in a 1:1 ratio to either group. Seven patients were excluded and complete data were obtained for 47 patients; 24 and 23 patients in group A and group B, respectively. There was no significant difference between the two groups in the alignment speed in the lower arch (P>0.05, mean difference=-0.44, 95% CI=-0.9 to 0.03) and root resorption (P>0.05). Alignment of upper arch was faster in group A (P < 0.0001, mean difference= - 0.9, 95% CI =-1.4 to -0.5)., Conclusions: There is no significant difference between the two groups in the alignment speed in the lower arch and incisors' RR. Upper arch alignment was faster in group A., Trial Registration: Not registered., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

We evaluated in vitro the influence of nickel-titanium instruments kinematics on the accuracy and variation of root canal working length measurements, performed with an integrated apex locator, at glide path and at the end of shaping. Forty-four mandibular incisors, included in an alginate model, were allocated at random to two groups: reciprocating and rotary. Working length was determined at glide path stage and at the end of shaping. Measurements given by the integrated apex locator were matched with visual measurements. The apex locator accuracy was based on inter-group comparison. The variation in working length was based on intra-group comparison. Kinematics influenced the accuracy of measurements only after shaping (p < 0.05), and not in the glide path (p > 0.05). Rotary had values closer to the visual measurements. Diminishing of measures occurred after shaping for reciprocating (p < 0.05); and at glide-path stage for rotary (p > 0.05). The integrated apex locator was more accurate with rotary kinematics., (© 2022 Australian Society of Endodontology Inc.)

Objective: This study evaluated the effect of three metal conditioners on the shear bond strength (SBS) of a prosthetic composite material to cpTi grade I having three surface treatments. Material and Methods: One hundred sixty eight rivet-shaped specimens (8.0x2.0 mm) were cast and subjected to polishing (P) or sandblasting with either 50 mm (50SB) or 250 mm (250SB) Al2O3. The metal conditioners Metal Photo Primer (MPP), Cesead II Opaque Primer (OP), Targis Link (TL), and one surface modification system Siloc (S), were applied to the specimen surfaces, which were covered with four 1-mm thick layers of resin composite. The resin layers were exposed to curing light for 90 s separately. Seven specimens from each experimental group were stored in water at 37ºC for 24 h while the other 7 specimens were subjected to 5,000 thermal cycles consisting of water baths at 4ºC and 60ºC (n=7). All specimens were subjected to SBS test (0.5 mm/min) until failure occurred, and further 28 specimens were analyzed using scanning electron microscope (SEM) and X-ray energy-dispersive spectroscopy (EDS). Data were analyzed by 3-way ANOVA followed by post-hoc Tukey's test (α=0.05). Results: On 50SB surfaces, OP groups showed higher SBS means than MPP (P

W pracy przedstawiono wyniki badań mikroskopowych dwóch stopów: Co-Cr-Mo i Co-Cr-W-Mo wraz z ilościową ana- lizą punktową składu chemicznego przy wykorzystaniu mikroanalizatora rentgenowskiego EDS. W ramach pracy wykonano również badania odporności korozyjnej stopów w środowisku sztucznej śliny. Mikrostruktura badanych stopów miała budowę dendrytyczną. W przestrzeniach międzydendrytycznych występowała eutektyka składająca się z węglików stopowych i auste- nitu kobaltowego. Osnowę dendrytyczną stanowił roztwór stały chromu, molibdenu i węgla w kobalcie (yCo), zaś wydzielenia występujące w obszarach międzydendrytycznych były bogate w Cr i Mo - w przypadku stopu Co-Cr-Mo oraz W i Mo - w przypadku stopu Co-Cr-W-Mo. Analizowane materiały wykazywały zbliżone przebiegi krzywych polaryzacji. Z otrzymanych wartości potencjału bezprądowego oraz na podstawie szerokiego obszaru pasywacji tych stopów można wnioskować o ich wysokiej odporności korozyjnej w badanym środowisku.

The aim of this study was to evaluate the quality of casting produced in an experimental short-term heating-cycle investment. Thus, reaction layer and castability of titanium casting using an experimental spinel-based investment (VR) with short heating cycle were compared with the commercial short-heating-cycle spinel-based investment Trinell (TR), the silica-phosphate-based investment Rematitan Plus (RP), and the conventional spinel-based investment Rematitan Ultra (RU). VR has polymeric fibers added to inorganic particles. Reaction layer assessments were carried out using Vickers hardness and elemental analysis using dispersive X-ray microanalysis (EDX). Mesh patterns were used for castability test, and powder characterization was made by scanning electron microscopy (SEM). Hardness evaluation showed no difference among the investments between 100 and 200 µm. The most important contaminant element for VR, TR, and RU was oxygen. Higher levels of mold filling were found for TR, VR, and RU compared with that obtained with RP. The quality of castings, characterized by means of the assessments of reaction layer and castability, made from the VR was similar to the commercial investments TR and RU but superior to the RP.

Introduction: Macrophages, the cells of the innate immunity play the significant role in immune reactions. In the early stages of inflammatory processes they are the main source of pro-inflammatory cytokines. Cytokines are produced during the interaction of cells with antigen and play an important role in the activation and regulation of immune response. Aim and Method: Our study aimed at exploring their production in a cell line THP1 (monocyte-macrophage cell line of human origin), cultivated for five days with an addition of salts of titanium, mercury, chromium, cobalt, nickel and palladium, which are frequent components of dental alloys. In the case of corrosion in the oral cavity environment these alloys can evoke in some patients a hypersensitive response. Results and Conclusion: The ions under study were found to affect the cells of the THP1 line to different extents, giving rise to a lowered but also enhanced production of chemotactic factors, pro-inflammatory cytokines and also cytokines participating in the regulation of the immune response. The influence of their production after exposition to metals can then lead to the development of an undesirable response to dental alloys.

In this work galvanic corrosion potentials and currents were measured usingpolarization curves of some dental alloys (amalgam, Co-Cr-Mo, Ni-Cr-Mo, SS 316L, Ti-6Al-4V alloys) in artificial saliva containing citric acid with three concentrations 3,6 and9 g/l at 37oC. All galvanic corrosion data were measured to coupling of amalgam andother alloys to investigate the galvanic corrosion between filling and other dental devicessuch as partial-denture framework, crowns, bridges, and endodontic instruments.The results of galvanic corrosion show that the coupling between amalgam and Ni-Cr-Mo alloy gives higher galvanic corrosion current than other metallic contact, and thenthe contact between amalgam and Co-Cr-Mo alloy was heavier compared with couplingof SS 316L and Ti-6Al-4V alloy with amalgam. The increasing of corrosion for alloyscontaining chromium due to rapidly converting of Cr6+ to Cr3+ and this phenomenondecreases the concentration of chromium ions at surface and then increases thedissolution of metal atoms, while decreasing of galvanic corrosion of Ti-alloy coupledwith amalgam due to the passive oxide surface layer (TiO2).

Bacground/Aim. Retentive force of removable partial denture (RPD) directly depends on elastic force of stretched retentive clasp arms (RCAs). During deflection RCA must have even stress distribution. Safety factor is the concept which can be applied in estimating durability and functionality of RCAs. This study was based on analyzing properties of clasps designed by conventional clasp wax profiles and defining the optimal shapes of RCAs for stress distribution and safety factor aspects. Methods. Computer-aided-design (CAD) models of RCAs with simulated properties of materials used for fabrication of RPD cobalt-chromium-molybdenum (CoCrMo) alloy, commercially pure titanium (CPTi) and polyacetale were analyzed. Results. The research showed that geometrics of Rapidflex profiles from the BIOS concept are defined for designing and modeling RCAs from CoCrMo alloys. I-Bar and Bonihard clasps made from CPTi might have the same design as Co- CrMo clasp only by safety factor aspect, but it is obvious that CPTi are much more flexible, so their shape must be more massive. Polyacetale clasps should not be fabricated by BIOS concept for CoCrMo alloy. A proof for that is the low value of safety factor. Conclusion. The BIOS concept should be used only for RCAs made of CoCrMo alloy and different wax profiles should be used for fabricating clasps of other investigated materials. The contribution of this study may be the improvement of present systems for defining the clasps shapes made from CoCrMo alloys. The more significant application is possibility of creating new concepts in defining shapes of RCA made from CPTi and polyacetale.