Risk aspects of dental restoratives: From amalgam to tooth-colored materials

Dental materials' choice of patients has considerably changed. Whereas cast gold and amalgam have been the predominant biomaterials for decades, today toothcolored materials like resin-based composites and ceramics are more and more successful. However, are we going to replace a good but biologically questionable material(amalgam) with an equal material(resin composite) being more esthetic but also biologically questionable? For amalgam, long-term clinical studies reported some significant hints that in single cases amalgam may be a health hazard for patients, finally Norway banned amalgam completely. The main advantage of a resin-based composite over amalgam is its tooth-like appearance and more or less absence of extensive preparation rules. For many years it was believed that resin-based composites may cause pulpal injury. However, pulpal injury associated with the use of resin-based composites is not correlated with their cytotoxic properties. Nevertheless, resin-based composites and other dental materials require rigorous safety evaluation and continuous monitoring to prevent adverse events similar like with amalgam. Because of nonbiocompatible pulp responses to resin-based composites and amalgam, they should not be placed in direct contact with the dental pulp. The less dentin remaining in the floor of preparations between resin-based composites or other dental materials is more likely to cause pulpitis. Percentage of patients and dental practitioners who display allergic reactions is between 0.7% and 2%. The release of cytotoxic monomers from resin-based materials is highest after polymerization and much lower after 1 wk. Substances released from resin-based composites have been shown to be toxic in cytotoxicity tests. Nevertheless, in vitro cytotoxicity assays have shown that amalgam has greater toxic effects than resin-based composites, sometime 100-700-fold higher. Altogether, the risk of side-effects is low, but not zero, especially for dental personnel.

Electrochemical behavior of Co-Cr and Ni-Cr dental cast alloys

The cast structures influencing the electrochemical corrosion behavior of Co-Cr and Ni-Cr dental alloys were studied using potentiodynamic polarization and AC impedance in 0.9% (mass fraction) NaCl solution at (37±1) ℃. The phase and microstructure of the alloys that were fabricated using two different casting methods viz. centrifugal casting and high frequency induction casting, were examined using X-ray diffraction analysis, scanning electron microscopy and energy dispersive spectroscopy. The roles of alloying elements and the passive film homogeneity on the corrosion resistance of Co-Cr-Mo and Ni-Cr-Mo dental cast alloys were reviewed. The results of electrochemical study show that the dependence of corrosion resistance on the microstructure associated with the casting methods is marginal. The Co-Cr alloy exhibits more desirable corrosion resistance properties than the Ni-Cr alloy. There is severe preferential dissolution of Ni-rich, Cr and Mo depleted zones in the Ni-Cr alloy.

Electrochemical behavior of dental implant system before and after clinical use

Electrochemical behavior of dental implant system before and after clinical use(in vivo and in vitro) was researched by using abutment and titanium fixture.To simulate an oral environment,the samples of clinically used and non-used implant systems as a working electrode were exposed to artificial saliva at(36.5±1) ℃.Electrochemical tests were carried out using a potentiostat.After electrochemical test,the corrosion morphology of each sample was investigated by FE-SEM and EDS.The corrosion potential and pitting potential of clinically used implant system are lower than those of non-used implant system,and clinically used implant system exhibits a lower range of passivation,indicating a less degree of inherent resistance against chloride ion.The polarization resistance decreases in the case of clinically used implant system,whereas,Rp for clinically non-used implant system increases compared with clinically used implant system.

Synthesis of CaO-SiO₂Compounds Using Materials Extracted from Industrial Wastes

Mineral trioxide aggregate (MTA) cement is an attractive material in endodontic dentistry. The purpose of this study was to produce calcium silicate, which is a major component of MTA, from waste materials. A dental alginate impression gel and used chalks were selected and mixed in a suitable ratio (Code: EXP). As a control, CaCO3 and a commercial diatomite were used (Code: CON). Each powder was heated to 850。C and 1000。C, and then kneaded with water. TG-DTA, compressive tests, SEM observations, elemental mapping analyses, and XRD analyses were performed. TG-DTA indicated that weight reduction of CaCO3 started at 600。C, and it completely decomposed on heating at 850。C. The strength was affected by the temperature. After heating, CaCO3 was transformed into CaO and/or Ca2SiO4, and Ca(OH)2 was formed by mixing with water. There were no differences between EXP and CON. These data suggested that recycled wastes might be promising MTA sources.

Mouth shield to minimize airborne transmission risk of COVID-19 and other infectious diseases in the dental office

Transmission of coronavirus disease(COVID-19)and other infectious diseases is a significant risk during dental procedures because most dental interventions involve aerosols or droplets that could contaminate the surrounding environment.Current protection guidelines to address the high risk of droplets,aerosols,and airborne particle transmission of COVID-19 in the dental office recommend minimizing aerosol-generating procedures.In this paper,an innovative mouth shield is presented that should minimize water backsplash from the air-water syringe during dental treatment.The mouth shield can be added to the personal protective equipment to provide the dental team with extra protection.It can be made of different materials,is straightforward,inexpensive,and safe to fabricate,and is easy to use.

Chemical incorporation of SiO_(2) into TiO_(2) layer by green plasma enhancer and quencher agents for synchronized improvements in the protective and bioactive properties

This study explores the dynamic interaction between environmentally sustainable plasma enhancer and quencher agents during the incorporation of SiO_(2) into a TiO_(2) layer,with the primary objective of simultaneously augmenting protective and bioactive attributes.This enhancement is realized through the synergistic utilization of Tetraethyl orthosilicate(TE)and Stevia(ST)within a plasma-assisted oxidation process.To achieve this goal,Ti–6Al–4V alloy underwent oxidation in an electrolyte solution containing acetate-glycerophosphate,with the addition of TE and ST separately and in combination.TE,as a silicon oxide(SiO_(2))precursor,facilitates the creation of a calcium-rich,rough,porous layer by undergoing hydrolysis to generate silanol groups(Si–OH),which subsequently condense into silicon-oxygen-silicon(Si–O–Si)bonds,resulting in SiO_(2) formation.In contrast,ST acts as a plasma quencher,absorbing highly reactive plasma species during the oxidation process,reducing energy levels,and diminishing sparking intensity.The combination of TE and ST results in moderate sparking,balancing Stevia's quenching effect and TE's sparking influence.As a result,this coating exhibits enhanced corrosion resistance and bioactivity compared to using either ST or TE alone.The study highlights the potential of this synergistic approach for advanced TiO_(2)-based coatings.

Dedifferentiated fat cells: an alternative source of adult multipotent cells from the adipose tissues

When adipose-derived stem cells （ASCs） arc retrieved from the stromal vascular portion of adipose tissue, a large amount of mature adipocytes are often discarded. However, by modified ceiling culture technique based on their buoyancy, mature adipocytes can be easily isolated from the adipose cell suspension and dediffercn- tiated into lipid-frce fibroblast-like cells, named dediffercntiated fat （DFAT） cells. DFAT cells rc-establish active proliferation ability and undertake multipotent capacities. Compared with ASCs and other adult stem cells, DFAT cells showed unique advantages in their abundance, isolation and homogeneity. In this concise review, the establishment and culture methods of DFAT cells arc introduced and the current profiles of their cellular nature are summarized. Under proper inducti~,n culture in vitro or environment in vivo, DFAT cells could demonstrate adipogenic, osteogenic, chondrogenie and myogenic potentials. In angiogenie conditions, DFAT cells could exhibit perivascular characteristics antt elicit neovascularization. Our preliminary findings also suggested the pericyte phenotype underlying such cell lineage, which supported a novel interpretation about the common origin of mesenchymal stem cells and tissue-specific stem cells within blood vessel walls. Current research on DFAT cells indicated that this alternative source of adult multipotent cells has great potential in tissue engineering and regenerative medicine.

Nanostructure and corrosion behaviors of nanotube formed Ti-Zr alloy

In order to investigate the nanostructures and corrosion behaviors of Ti-Zr alloys,nanotube formed Ti-Zr(10%,20%,30% and 40% in mass fraction) alloys were prepared by arc melting and the condition of controlling nanostructure was at 1 000 ℃ for 24 h in argon atmosphere;formation of nanotubes was conducted by anodizing a Ti-Zr alloy in H3PO4 electrolyte with a small amount of fluoride ions at room temperature.The corrosion properties of specimens were examined through potentiodynamic test(potential range of -1 500-2 000 mV) in 0.9% NaCl solution by using potentiostat.Microstructures of the alloys were observed by optical microscope(OM),field emission scanning electron microscope(FE-SEM) and X-ray diffractometer(XRD).Diameter of nanotube does not depend on Zr content,but interspace of nanotube predominantly depends on Zr content,which confirms that ZrO2 oxides play a role to increase the interspace of nanotube formed on the surface.

Mechanical properties and corrosion resistance of low rigidity quaternary titanium alloy for biomedical applications

Electrochemical corrosion of Ti-35Nb-5Ta-7Zr alloy fabricated by arc melting and heat treatment process was studied in 0.9% NaCl at(37±1) ℃.Phase and microstructure of the fabricated alloy were investigated using X-ray diffractometer and scanning electron microscope.Mechanical properties such as yield strength and elastic modulus of the alloy were determined by tensile test.Potentiodynamic polarization technique and impedance spectroscopy were employed to study the corrosion behavior.The results of the study were compared with those obtained for Ti-6Al-4V commercial alloy.The result of the study supports feasibility of Ti-35Nb-5Ta-7Zr alloy for implant applications.

Influence of Fiber Reinforcement on the Properties of Denture Base Resins

Advances in the medical sciences along with rapid increase in the specialized and better treatment modalities, certainly prolonged the human life with a drastic increase in the number of elderly in the past few decades. Tooth loss is one of the manifestations of aging. Dentures and dental implants are the major prosthetic devices given to restore physiological and esthetic functions of oral tissues of edentulous or partially edentulous patients. Complete and partial dentures based on polymeric compositions are the most popular devices since the cost of dental implants and metal-base dentures are much higher. Among the polymers, poly (methyl methacrylate) (PMMA) is the most commonly used material for this purpose. Although, this material is not ideal in every respect, it is the combination of qualities rather than one single desirable property that accounts for its popularity and usage. One of the main drawbacks of this material is considered to be its poor mechanical performance. There have been several attempts in the recent past to address the problem of inferior mechanical properties of these materials. Generally, there are three ways which have been investigated to improve the mechanical properties of denture bases;search for or development of an alternative material to PMMA;chemical modification of PMMA;and the reinforcement of PMMA. Present article is a review of types of fibres reinforced in denture prosthesis and their effects on mechanical properties of denture prosthesis.

Effects of inorganic ions,organic particles,blood cells,and cyclic loading on in vitro corrosion of Mg–Al alloys

Recently,magnesium(Mg)alloys have attracted extensive attention as biodegradable implant materials.However,cyclic loading and the corrosive environment of the body are significant challenges for the practical use of alloys,and there are few studies on this topic.In this study,we conducted a four-point bending fatigue test for 86,400 cycles(12 h)in simulated body fluid(SBF),plasma,and whole blood with an AZ series alloy Mg-9Al-0.5Zn-0.27Mn-0.12Ag,to examine the effects of inorganic ions,organic particles,blood cells,and cyclic loading on Mg alloy corrosion.The Mg^(2+)concentration and solution pH were measured before and after experimentation,and the sample surfaces were characterized by 3D digital microscopy,scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDS),Fourier-transform infrared(FTIR)spectroscopy,Raman spectroscopy,and X-ray photoelectron spectroscopy(XPS).Our results showed that in the non-loading condition,a porous and weak inorganic product layer(mainly Mg/Ca phosphate and carbonate)formed on the surface of the Mg alloy sample immersed in SBF,which hardly had a protective effect on Mg alloy corrosion.For the samples immersed in plasma,the organic particles promoted the formation of an organic and more compact product layer,which protected the Mg alloy from severe corrosion.For the sample immersed in whole blood,the blood cells affected organic particle deposition on the product layer and thus interfered with the formation of an organic compact product layer,which slightly accelerated the corrosion process.Furthermore,cyclic loading damaged the layer integrity and significantly increased the corrosion rates of all the studied materials compared to the samples not subjected to cyclic loading.Nonetheless,under cyclic loading,blood cells adsorbed on the Mg alloy surfaces,and formed films,which protected the Mg alloy substrate and delayed Mg alloy corrosion.

Posterior partially edentulous jaws, planning a rehabilitation with dental implants

AIM: To discuss important characteristics of the useof dental implants in posterior quadrants and the rehabilitation planning. METHODS: An electronic search of English articles was conducted on MEDLINE(PubM ed) from 1990 up to the period of March 2014. The key terms were dental implants and posterior jaws, dental implants/treatment planning and posterior maxilla, and dental implants/treatment planning and posterior mandible. No exclusion criteria were used for the initial search. Clinical trials, randomized and non randomized studies, classical and comparative studies, multicenter studies, in vitro and in vivo studies, case reports, longitudinal studies and reviews of the literature were included in this review. RESULTS: One hundred and fifty-two articles met the inclusion criteria of treatment planning of dental implants in posterior jaw and were read in their entirety. The selected articles were categorized with respect to their context on space for restoration, anatomic considerations(bone quantity and density), radiographic techniques, implant selection(number, position, diameter and surface), tilted and pterygoid implants, short implants, occlusal considerations, and success rates of implants placed in the posterior region. The results derived from the review process were described under several different topic headings to give readers a clear overview of the literature. In general, it was observed that the use of dental implants in posterior region requires a careful treatment plan. It is important that the practitioner has knowledge about the theme to evaluate the treatment parameters. CONCLUSION: The use of implants to restore the posterior arch presents many challenges and requires a detailed treatment planning.

Effects of TiN film coating on electrochemical behaviors of nanotube formed Ti-xHf alloys

Ti-xHf(x=10%,20%,30% and 40%,mass fraction) alloys were prepared by arc melting,and the microstructure was controlled for 24 h at 1 000 ℃ in argon atmosphere.The formation of nanotube was conducted by anodizing on Ti-Hf alloys in 1.0 mol/L H3PO4 electrolytes with small amounts of NaF at room temperature.And then TiN coatings were coated by DC-sputtering on the anodized surface.Microstructures and nanotube morphology of the alloys were examined by field emission scanning electron microscopy(FE-SEM) and X-ray diffractometry(XRD).The corrosion properties of the specimens were examined through potentiodynamic test(potential range from -1 500 to 2 000 mV) in 0.9 % NaCl solution by potentiostat.The microstructure shows the acicular phase and α' phase with Hf content.The amorphous oxide surface is transformed to crystalline anatase phase.TiN coated nanotube surface has a good corrosion resistance.

Surface characteristics of HA coated Ti-Hf binary alloys after nanotube formation

Ti-Hf binary alloys contained 10%,20%,30% and 40%(mass fraction)Hf were manufactured in the vacuum furnace system.And then,specimens were homogenized for 24 h at 1 000 ℃ in argon atmosphere.The formation of oxide nanotubes was conducted by anodic oxidation on the Ti-Hf alloy in 1 mol/L H3PO4 electrolytes containing small amounts of NaF at room temperature.The hydroxyapatite(HA) coating made of tooth ash prepared by electron-beam physical vapor deposition(EB-PVD) method.The corrosion behaviors of the specimens were examined through potentiodynamic test in 0.9% NaCl solution by potentiostat.The microstructures of the alloys were examined by field emission scanning electron microscopy(FE-SEM) and x-ray diffractometer(XRD).It was observed that the lamellar structure translated to needle-like structure with Hf contents.Nanotube formed and HA coated Ti-xHf alloys had a good corrosion resistance.

Adaptation of a Biomineralization Strategy for Remineralization of Enamel and Dentin

The bio- inspired strategy of triggered release of Ca^2＋ , Pi, F from prosomal compartments was used to induce rapid formation of FHA for potential dental use ： Calcium and inorganic phosphate salts were separately loaded into temperature-sensitive liposome composed of 90% DPPC and 10% DMPC. When heated from the room temperature to 35- 37 ℃ , the entrapped calcium, inorganic phosphate and fl^rin released from the liposome,A mixture of Ca- Pi and F-loaded liposome formed apatite. The mineral was indicated by a rapid drop in suspension PH from 7.4 approximately 6. This was illustrated by applying a liposome suspension warmed human dentin and enamel surface which resulted in deposition of apatite onto the tissue substrates.

Monkeypox awareness,knowledge,and attitude among undergraduate preclinical and clinical students at a Malaysian dental school:An emerging outbreak during the COVID-19 era

Objective:To evaluate the awareness,knowledge,and attitude on monkeypox viral infection among preclinical and clinical dental students in Malaysia.Methods:A cross-sectional study was conducted among 229 preclinical and clinical dental students via an online self-reported questionnaire.The questionnaire included 3 items on awareness,15 items on knowledge,9 items on attitude and 2 open-ended questions.Data were presented as frequencies and percentages.Chi-square test was used to compare knowledge and awareness scores between preclinical and clinical dental students and content analysis was performed for open-ended responses.Results:Preclinical and clinical dental students were aware of the existence of monkeypox(89.5%and 94.4%,respectively),that the disease emerged in non-endemic countries(81.0%and 87.1%,respectively)and that it was declared a public health emergency of international concern by the World Health Organization(73.3%and 79.0%,respectively).Clinical dental students’overall knowledge level was significantly higher than preclinical dental students(P=0.014).Both preclinical(95.2%)and clinical(96.8%)dental students demonstrated positive attitudes toward monkeypox with no significant difference(P=0.736)noted between them.Three themes emerged from the open-ended questions:(1)reimplementation of nationwide lockdown,(2)impact on the economy and health,and(3)disruption to the educational system.Students also anticipated their face-to-face learning to be reduced should there be a new outbreak.Conclusions:Both preclinical and clinical dental students showed comparable awareness and attitudes,while the latter demonstrated greater satisfactory knowledge toward the re-emergence of monkeypox during the COVID-19 pandemic.Nonetheless,efforts to improve dental students’understanding of this alarming outbreak are required,to safeguard their health and minimise transmission.

Fluid filtration and dye leakage testing of Resilon/Epiphany and guttapercha/Pulp Canal Sealer root canal fillings

The aim of the present study was to compare sealing abilities of Resilon/Epiphany (R/E) with those of guttapercha and Kerr Pulp Canal Sealer EWT (GP/PCS). 50 single rooted teeth were randomly divided into 2 groups (n = 22) (R/E;GP/PCS), and 2 control groups (n = 3) (Positive, Negative). Fluid flow rate through the filled roots was measured using a fluid filtration device. The same specimens were immersed in a 2% Methylen Blue Solution. Roots were embedded in clear epoxy resin and cross sectionet at 1 mm intervals along the length of the root. Circumferential dye penetration was evaluated at 40× magnification. Fluid filtration of teeth obturated with the R/E system (0.085 [0.057, 0.113] μL·min-1), and dye penetration test showed no statistically significant difference compared to those obturated with GP/PCS (0.113 [0.057, 0.141] μL·min-1). Within the limits of the present study, there is no statistically significant difference between R/E and GP/PCS sealing abilities.

Late Regularization of the Alveolar Ridge in a Patient with a Prosthesis and Special Needs: A Case Report

Residual ridge shape is important for the seating of a prosthesis. The objective of this case report was to illustrate the importance of reduction maneuvers with regard to alveolar bone plates after multiple tooth extractions in patients with prostheses and special needs. In the current patient, there were difficulties during the adaptation and fitting of the upper denture. Bilateral bone resection was indicated in the molar buccal region. Late regularization of the alveolar ridge, which was accomplished in hospital, was necessary for the preparation, adaptation, and use of the denture. The general and systemic health care of the patient should be monitored throughout surgical intervention. Though tooth extractions are common procedures, particular attention is required to ensure adequate alveolar ridge remodeling that is conducive to oral rehabilitation.

A Case Report of Kissing Molars Class III

Kissing molars (KMs), first reported by Van Hoof in 1973, refer to molars with occlusal surfaces that contact each other in a single follicular space while their roots extend in opposite directions. This is a case of a 20-year-old male who presented with complaints of right mandibular molar pain with cold water contact and occlusion. Panoramic and cone-beam computed tomography (CBCT) images revealed impaction of the right mandibular third and fourth molars, with the occlusal surfaces contacting each other while the roots extended in opposite directions. KMs are classified according to the impaction of the mandibular first and second molars (Class I), second and third molars (Class II), and third and fourth molars (Class III). Our patient was considered Class III. Given the patient’s preference for surgical treatment, successful teeth extraction and extirpation were performed under intravenous sedation. The patient’s postoperative course was unremarkable. We describe a case of KMs Class III with a cystic variant assessed by panoramic and CBCT images. We additionally review all KMs Class III reported in the literature.

Cell Proliferation Ability of Mouse Fibroblast-Like Cells and Osteoblast-Like Cells on a Ti-6Al-4V Alloy Film Produced by Selective Laser Melting

Successful regeneration of tissues and organs relies on the application of suitable substrates or scaffolds in scaffold-based regenerative medicine. In this study, Ti-6Al-4V alloy films (Ti alloy film) were produced using a three-dimensional printing technique called Selective Laser Melting (SLM), which is one of the metal additive manufacturing techniques. The thickness of produced Ti alloy film was approximately 250 μm. The laser-irradiated surface of Ti alloy film had a relatively smooth yet porous surface. The non-irradiated surface was also porous but also retained a lot of partially melted Ti-6Al-4V powder. Cell proliferation ability of mouse fibroblast-like cells (L929 cells) and mouse osteoblast-like cells (MC3T3-E1 cells) on both the surfaces of Ti alloy film was examined using WST assay. Both L929 and MC3T3-E1 cells underwent cell proliferation during the culture period. These results indicate that selective laser melting is suitable for producing a cell-compatible Ti-6Al-4V alloy film for biomaterials applications.