Metal Restorations Research Articles

Microdroplet-Based In Situ Characterization Of The Dynamic Evolution Of Amorphous Calcium Carbonate during Microbially Induced Calcium Carbonate Precipitation.

Amorphous calcium carbonate (ACC) plays an important role in microbially induced calcium carbonate precipitation (MICP), which has great potential in broad applications such as building restoration, CO2 sequestration, and bioremediation of heavy metals, etc. However, our understanding of ACC is still limited. By combining microscopy of cell-laden microdroplets with confocal Raman microspectroscopy, we investigated the ACC dynamics during MICP. The results show that MICP inside droplets can be divided into three stages: liquid, gel-like ACC, and precipitated CaCO3 stages. In the liquid stage, the droplets are transparent. As the MICP process continues into the gel-like stage, the ACC structure appears and the droplets become opaque. Subsequently, dissolution of the gel-like structure is accompanied by growth of precipitated CaCO3 crystals. The size, morphology, and lifetime of the gel-like structures depend on the Ca2+ concentration. Using polystyrene colloids as tracers, we find that the colloids exhibit diffusive behavior in both the liquid and precipitated CaCO3 stages, while their motion becomes arrested in the gel-like ACC stage. These results provide direct evidence for the formation-dissolution process of the ACC-formed structure and its gel-like mechanical properties. Our work provides a detailed view of the time evolution of ACC and its mechanical properties at the microscale level, which has been lacking in previous studies.

Biochar, Ochre, and Manure Maturation in an Acidic Technosol Helps Stabilize As and Pb in Soil and Allows Its Vegetation by Salix triandra

Past mining extraction activities still have a negative impact in the present time, the resulting metal(loid) contaminated soils affecting both the environment and human health. Assisted phytostabilization technology, combining soil conditioner application to immobilize metal(loid)s and plant growth to reduce erosion and leaching risks, is a useful strategy in the restoration of metal(loid) contaminated lands. However, contaminants will respond differently to a particular amendment, having their own specific characteristics. Therefore, in multi-contaminated soils, soil conditioner combination has been suggested as a good strategy for metal(loid) immobilization. In the present study, in a mesocosm experiment, organic (biochar and manure) and inorganic (ochre) amendments were evaluated in single and combined applications for their effect on metal(loid) stabilization and Salix triandra growth improvement, in an arsenic and lead highly contaminated soil. Specifically, the effects of these amendments on soil properties, metal(loid) behavior, and plant growth were evaluated after they aged in the soil for 6 months. Results showed that all amendments, except biochar alone, could reduce soil acidity, with the best outcomes obtained with the three amendments combined. The combination of the three soil conditioners has also led to reducing soil lead availability. However, only ochre, alone or combined with the other soil fertilizers, was capable of immobilizing arsenic. Moreover, amendment application enhanced plant growth, without affecting arsenic accumulation. On the contrary, plants grown on all the amended soils, except plants grown on soil added with manure alone, showed higher lead concentration in leaves, which poses a risk of return of lead into the soil when leaves will shed in autumn. Considering that the best plant growth improvement, together with the lowest increase in lead aerial accumulation, was observed in manure-treated soil, the addition of manure seems to have potential in the restoration of arsenic and lead contaminated soil.

Prosthodontic Rehabilitation

Amelogenesis imperfecta is a genetically determined inherited disorder characterized by abnormal formation of tooth enamel leading to esthetic, functional, and psychological impact on the patient. If teeth affected are not treated early; the existing condition will further deteriorate, leading to injury to the attachment apparatus complicating the proposed treatment plan and future prognosis. The definitive objectives of this rehabilitation were to eradicate tooth sensitivity while restoring masticatory function and enhancing esthetics. Treatment plan included root canal treatment of the decrepit teeth followed by porcelain fused to metal restoration. This case report highlight the prosthodontic management of a patient diagnosed with hypomaturation type amelogenesis imperfecta.

Toxic Metals in a Paddy Field System: A Review.

The threat of toxic metals to food security and human health has become a high-priority issue in recent decades. As the world’s main food crop source, the safe cultivation of rice has been the focus of much research, particularly the restoration of toxic metals in paddy fields. Therefore, in this paper, we focus on the effects of toxic metals on rice, as well as the removal or repair methods of toxic metals in paddy fields. We also provide a detailed discussion of the sources and monitoring methods of toxic metals pollution, the current toxic metal removal, and remediation methods in paddy fields. Finally, several important research issues related to toxic metals in paddy field systems are proposed for future work. The review has an important guiding role for the future of heavy metal remediation in paddy fields, safe production of rice, green ecological fish culture, and human food security and health.

Dental management in head and neck cancers: from intensity-modulated radiotherapy with photons to proton therapy.

Despite reduction of xerostomia with intensity-modulated compared to conformal X-ray radiotherapy, radiation-induced dental complications continue to occur. Proton therapy is promising in head and neck cancers to further reduce radiation-induced side-effects, but the optimal dental management has not been defined. Dental management before proton therapy was assessed compared to intensity-modulated radiotherapy based on a bicentric experience, a literature review and illustrative cases. Preserved teeth frequently contain metallic dental restorations (amalgams, crowns, implants). Metals blur CT images, introducing errors in tumour and organ contour during radiotherapy planning. Due to their physical interactions with matter, protons are more sensitive than photons to tissue composition. The composition of restorative materials is rarely documented during radiotherapy planning, introducing dose errors. Manual artefact recontouring, metal artefact-reduction CT algorithms, dual or multi-energy CT and appropriate dose calculation algorithms insufficiently compensate for contour and dose errors during proton therapy. Physical uncertainties may be associated with lower tumour controlprobability and moreside-effects after proton therapy. Metal-induced errors should be quantified and removal of metal restorations discussed on a case by case basisbetween dental care specialists, radiation oncologists and physicists. Metallic amalgams can be replaced with water-equivalent materials and crowns temporarily removed depending on rehabilitation potential, dental condition and cost. Implants might contraindicate proton therapy if they are in the proton beam path. Metallic restorations maymore severely affect proton than photon radiotherapy quality. Personalized dental care prior to proton therapy requires multidisciplinary assessment of metal-induced errors before choice of conservation/removal of dental metals and optimal radiotherapy.

Effect of scanning-aid agents on the scanning accuracy in specially designed metallic models: A laboratory study.

The advent of intraoral scanning methods has caused a paradigm shift in dentistry. However, despite their many advantages, intraoral scanners cannot accurately recognize the metallic surfaces of prothesis. Therefore, this experiment was designed to verify the effect of scanning-aid agents on the scanning accuracy using metallic reference models. Three different types of metallic reference models (inlay, onlay, and bridge) were specially designed and produced using a milling machine to simulate intraoral dental restorations. Three experimental groups (application of ScanCure, IP Scan Spray, and VITA Powder Scan Spray) were set up and scanned images (each n = 5) were acquired using the I500® intraoral scanner. The reference datasets were established by a 3D design that reflected the deviations between the measured distances and previously planned distances on the reference models. All acquired experimental datasets were digitally superimposed and compared with the reference datasets. Intragroup comparisons (precision, n = 10) were also performed. The root mean square (RMS) values of trueness in the ScanCure and IP groups were significantly more accurate than those of the VITA group in the inlay and onlay reference models (p < 0.05). Notably, in the bridge reference model, the liquid-type ScanCure group showed the highest accuracy of trueness, with statistical significance (p < 0.05). However, the RMS values of precision were not significantly different among the groups. These findings suggest that liquid-type scanning agents can be effectively used to obtain more accurate scan images of intraoral metallic dental restorations.

Solubility of Dental Ceramics in Electric Fields

Combining dental ceramics with other prosthetic metallic restorations might release metal ions, thus affecting the oral tissues of the patients. In this study, we evaluated the electrochemical solubility of various dental ceramics in a galvanic experimental setup in vitro. Smooth and rough feldspathic and zirconium dioxide ceramics (at pH 5.5 and pH 3.0) were exposed to an electric field. Calcium, barium, and zirconium were selected as parameters to determine the solubility of both types of ceramic materials. Among all test groups, feldspathic ceramics were more soluble than zirconium dioxide ceramics at low pH. The results indicated that the solubility of zirconium dioxide was not significantly affected by the presence of an electric field, although the solubility was higher when the pH was relatively lower. The feldspathic material had a higher sensitivity to acids and electrogalvanic processes. We found that the galvanic process increases the solubility of feldspathic ceramics. The surface quality is important in an acidic medium, especially for feldspathic ceramics. Zirconium dioxide ceramics are more resistant to an acidic medium and exposure to a clinically relevant electric field.

MRI and Its Implications in Dentistry

Magnetic Resonance imaging (MRI) has become one of the most powerful diagnostic tools in radiology and diagnostic sciences. It is non-invasive and non-ionizing and the images are highly sensitive and specific with excellent soft tissue contrast. It gives excellent images of anatomic structures differing in proton density and other tissue characteristics. It can be used to assess intracranial and extracranial lesions particularly those involving the soft tissues.&#x0D; MRI has the shortcoming of being prone to magnetic susceptibility difference artefacts, caused by the presence of metallic materials such as dental restorative materials, implants and orthodontic appliances. All substances when placed in a magnetic field are magnetized to a degree which varies according to their magnetic susceptibility. Non precious dental alloys have the potential of causing image deformation or image voids. &#x0D; Dentists are not the only professionals implanting metal devices. Heart pacemakers and defibrillators, aneurysm clips, cochlear implants, insulin pumps, vascular stents and artificial joints are widely used in various branches of medicine. In some cases, it is not possible to carry out MRI due to extensive dental hardware with a high ferromagnetic content. Severe image distortion or an inability to perform the MRI scan due to dental restorations is a rare problem, but cannot be completely eliminated. This article has been written to educate the dentists on the implications of metallic dental restorations on MRI scans.&#x0D; Keywords: Magnetic resonance imaging, MRI, Dentistry, Dental materials, artefact, artifacts.

Esthetic and functional rehabilitation of mutilated maxillary anterior teeth: A case series

An endodontically treated anterior tooth requires extracoronal restoration when the tooth structure is weakened or lost due to caries, placement of previous restorations and/or discoloured. The reduced tooth structure makes retention of extracoronal restoration difficult. The purpose of post is to provide retention for the core restoration, which replaces lost coronal structure. This article describes restoration of mutilated maxillary anterior teeth by using cast post and core, followed by porcelain fused to metal restorations.

Biochar fungal pellet based biological immobilization reactor efficiently removed nitrate and cadmium

To efficiently and simultaneously remove nitrate (NO3−-N) and Cd(II) from aqueous solution, a novel type of biochar fungal pellet (BFP) immobilized denitrification bacteria (Cupriavidus sp. H29) composite was used in a bioreactor. The removal performance of the bioreactor R1 for the initial concentration of 27.7 mg L−1 nitrate and 10.0 mg L−1 Cd(II) reached 98.1 and 93.9% respectively, and the inoculation of strain H29 in bioreactor R1 significantly enhanced the removal efficiency of contaminants. The 3D-EEM spectra analysis showed that the activity of microorganisms in the bioreactor was higher at a lower concentration of Cd(II). FTIR indicated the effect of functional groups in BFP in bioadsorption of Cd(II). In addition, high-throughput analysis of species composition of the microbial community in the bioreactors at different levels demonstrated that strain H29 played a significant part in the bioreactor. This research provided a perspective for simultaneous restoration of nitrate and heavy metals in wastewater, and also enriched the application of fungal pellet (FP) in reactors.

Application of Biochar for the Restoration of Metal(loid)s Contaminated Soils

Biochar has recently aroused great interest for the restoration of contaminated soils since it improves soil properties and induces the immobilization of pollutants. This study evaluates the use of biochar from plant pruning, applied as an amendment, for immobilizing metal(loid)s in a highly contaminated soil as well as for reducing the phytotoxicity of these pollutants by promoting natural revegetation. For this purpose, a bioassay with Trifolium pratense L. was used to test the effectiveness of the soil amendment in greenhouse conditions. Three treatments were carried out including soil contaminated with metal(loid)s (RA), and this soil was amended with biochar at different dosage: 4% (RA4B) and 8% (RA8B). A non-contaminated soil (NC) from a nearby area not affected by contamination was used as a control. The results show that biochar increased soil pH by several units depending on the dose used, 8% being the most effective one. Biochar treatments also reduced soluble and bioavailable forms of Zn and Cu. Likewise, phytotoxicity was significantly reduced, promoting seed germination and biomass with plant growth values similar to the non-polluted soil. In light of the results obtained, the evaluation of the bioremediation potential of biochar under field conditions can be considered.

Combined application of marble waste and beneficial microorganisms: toward a cost-effective approach for restoration of heavy metals contaminated sites.

Heavy metal (HM) pollution and the need to preserve the environment have gathered increasing scientific attention. The immobilization of HMs into less-soluble, less mobile, and less toxic forms in addition to the improvement of Medicago sativa L. growth and HMs accumulation were evaluated after the application of marble waste (MW) and/or beneficial PGP rhizobacteria and mycorrhizae to the mining soil compost. A greenhouse assay was conducted to elucidate the influence of both amendment and beneficial microorganisms. The application of marble waste to the soil-compost resulted in decreasing the bioavailability of metals (Cu, Zn, Pb, and Cd), thus ameliorating the installation of the vegetal cover for 6months of culture. Cultivation of M. sativa under 5% MW-amended soil for 6months increased the shoot dry weight by almost twofold, while the inoculation with rhizobacteria-mycorrhizae combined with the application of 15% MW resulted in an improvement of 3.5-fold in case of shoot dry weight. In addition, the application of marble waste amendment or their combination with metallo-resistant bacteria resulted in decreasing HM accumulation leading to HM content below the threshold recommended for animal grazing. Thus, the application of amendments and beneficial microorganisms appeared to guarantee the safe cultivation of alfalfa for 6months of culture. The dual combination amendments and beneficial microorganisms showed the good potential to restore HM polluted soils and could stand as a novel approach for restoration of HM-contaminated soils.

Dental resin composites: A review on materials to product realizations

Dental resin composites have revolutionized dental care and enabled minimally invasive dentistry to preserve healthy tooth structure and provide natural-appearing esthetic results; these materials are now good alternatives to metal and amalgam restorations. Nevertheless, dental composites are being further developed to enhance their long-term clinical performance and longevity. With a complete understanding of the various material characteristics and design strategies of dental composite systems, frontiers of dental restoration research can aim towards creating novel materials that can produce very similar properties, functionalities, and internal structures as hard dental tissues. In this review article, the authors present an overview of the synthesis of the advanced dental composite systems with the recent research and development fields over the last 5 years. This review also explores how to control and optimize the required properties of the composites, ideally to increase the longevity/durability of restorations preventing recurrent caries. Research studies and commercial products are introduced to forecast the demands and trends of resin-based dental composites, in order to assist clinicians and researchers in optimal selection of materials to fulfill mechanical, physical, biological, and functional requirements.

Development of an artificial intelligence-based algorithm to classify images acquired with an intraoral scanner of individual molar teeth into three categories

Forensic dentistry identifies deceased individuals by comparing postmortem dental charts, oral-cavity pictures and dental X-ray images with antemortem records. However, conventional forensic dentistry methods are time-consuming and thus unable to rapidly identify large numbers of victims following a large-scale disaster. Our goal is to automate the dental filing process by using intraoral scanner images. In this study, we generated and evaluated an artificial intelligence-based algorithm that classified images of individual molar teeth into three categories: (1) full metallic crown (FMC); (2) partial metallic restoration (In); or (3) sound tooth, carious tooth or non-metallic restoration (CNMR). A pre-trained model was created using oral-cavity pictures from patients. Then, the algorithm was generated through transfer learning and training with images acquired from cadavers by intraoral scanning. Cross-validation was performed to reduce bias. The ability of the model to classify molar teeth into the three categories (FMC, In or CNMR) was evaluated using four criteria: precision, recall, F-measure and overall accuracy. The average value (variance) was 0.952 (0.000140) for recall, 0.957 (0.0000614) for precision, 0.952 (0.000145) for F-measure, and 0.952 (0.000142) for overall accuracy when the algorithm was used to classify images of molar teeth acquired from cadavers by intraoral scanning. We have created an artificial intelligence-based algorithm that analyzes images acquired with an intraoral scanner and classifies molar teeth into one of three types (FMC, In or CNMR) based on the presence/absence of metallic restorations. Furthermore, the accuracy of the algorithm reached about 95%. This algorithm was constructed as a first step toward the development of an automated system that generates dental charts from images acquired by an intraoral scanner. The availability of such a system would greatly increase the efficiency of personal identification in the event of a major disaster.

Measurement Accuracy in Cone Beam Computed Tomography in the Presence of Metal Artifact.

Cone beam computed tomography (CBCT) image quality is known to be affected by artifacts produced by metal restorations, causing image deterioration via bright streaks and loss of gray values in the vicinity of the metallic structure. The aim of the study was to determine the impact of progressively increasing metal artifacts on the measurement accuracy of commonly evaluated points in implant treatment planning. Holes were drilled into porcine mandibles at known distances from the alveolar crest on the buccal and lingual surfaces and filled with gutta-percha. Repeated CBCT images were taken, with progressively increasing amalgam restorations and stainless steel crowns (up to a total of eight restorations per jaw). The imaging field of view (FOV) was of a single site (5 × 5 cm2) in two different locations in the mandible, as well as a full-arch FOV (10 × 5 cm2). Images were taken using clinical settings, and with increased kVp and exposure time, without metal artifact reduction (MAR) corrections. Measurements between the buccal and lingual gutta-percha points on the mandible were performed using a digital caliper and compared to the same measurements taken digitally on the CBCT images. Measurements were obtained with no restorations (baseline) and compared with increasing number of restorations. Comparison between caliper measurements and baseline CBCT with no metal artifact demonstrated differences ranging from 0 to 1.7 mm, with no clear detectable pattern of change related to the restorations. Compared to baseline measurements, scans with amalgam and stainless steel restorations showed a maximum difference of 0.54 ± 0.64 mm and 0.62 ± 0.64 mm, respectively, with no significant differences with increasing metal restorations. There may be a variation of up to 1.7 mm between measured anatomical points and CBCT imaging under commonly used settings. While this result may be clinically important, it does not appear to be affected by increasing metal artifact due to amalgam restorations or stainless steel crowns. The findings of this study support current clinical practices accounting for a safety margin of up to 2 mm with any CBCT image, and not limiting CBCT scans for patients with multiple metal restorations.

The effect of metallic dental restorations and implants in causing patient discomfort and artefacts during magnetic resonance imaging of the head and neck.

Patients with metallic dental objects in their oral cavity are often associated with discomfort or artefacts during magnetic resonance imaging (MRI) of the head and neck. This study was conducted to evaluate the effects of metallic dental objects in causing patient discomfort and artefacts during MRI of the head and neck region. This is an observational study including 538 participants from various specialized MRI centres in Kozhikode. MRI records of 538 participants who underwent head and neck MRI as a part of their medical treatment were collected. With the help of questionnaire and clinical examination, the type of metallic dental object in the patient's oral cavity was identified. After examining the MRI images, four categories of artefacts were established. In MRI brain, artefacts in three different sequences were also studied. The significance of the difference between proportions was analysed by the Chi-square test. Artefacts were found in 65 cases with metallic dental objects but none of the participants had experienced any kind of discomfort. The artefact formation significantly depended on the type of metallic dental restoration in the patient's oral cavity. Orthodontic braces and titanium bone plate created severe artefacts in head and neck MRI making interpretation almost impossible. In the MRI brain, diffusion-weighted imaging is most sensitive to artefact followed by fluid-attenuated inversion recovery. Artefacts were found in 65 cases with metallic dental restorations but none of the participants had experienced any kind of discomfort.

Metal ceramic restorations for full mouth rehabilitation in amelogenesis imperfecta

Amelogenesis imperfecta (AI) is a clinical condition of natural teeth in which enamel fails to mature due to which the patient faces sensitivity, attrition and poor aesthetics. The condition is genetically inherited and requires multidisciplinary treatment planning to achieve effective success. Treatment ranges from individual crowns to fixed partial dentures or implant-supported single crowns and is related to multiple factors like age and condition of remaining natural teeth. The use of metal and ceramic restorations in such cases requires knowledge and understanding of basic material science, which helps to improve the efficiency of the treatment. This article presents a case of a young adult male patient who presented with AI with a chief complaint of poor esthetics. Maxillary and mandibular teeth had undergone attrition with concomitant loss of anterior guidance. The occlusion was successfully established after restoring anterior guidance which was determined by the use of temporary crowns. Porcelain fused to metal restorations was given and the patient was put on a long-term follow-up. The patient was highly satisfied with the outcome of the rehabilitation.

THE RESTORATION OF AN AESTHETIC AND FUNCTIONAL ABUTMENT UNDER AN EXISTING CAST PARTIAL DENTURE - A SIMPLE TECHNIQUE.

The restoration of edentulism through cast partial denture is one of the important goals of prosthodontics. The caries destruction of an abutment tooth supporting a Cast Partial Denture (CPD) is commonly associated with the loss of retention of the prosthesis, making it non-functional. Even though the literature discusses many techniques for the prosthodontic restoration of destructed abutment tooth supporting a CPD, none of them explains a simple method which incorporates the retentive features as well as aesthetics on the definitive restoration. This article discusses an innovative yet simple technique for the fabrication of a provisional crown as well as a definitive porcelain fused to metal restoration, which can maintain the aesthetics and retentive features of the abutment. This technique enables the patient to continue wearing the existing prosthesis.

EVALUATION OF THE MARGINAL ACCURACY IN PORCELAIN FUSED TO METAL COPINGS FABRICATED IN TWO DIFFERENT FINISH LINES USING THREE DIFFERENT DIE MATERIALS -A STEREOMICROSCOPIC ANALYSIS AS A COMPARATIVE STUDY

Introduction: In the 20th century itself innovative techniques and materials were introduced for the fabrication of restorations that accurately fit over the prepared surface of the tooth. To fabricate these restorations, various materials like metals, alloys, resins, and ceramics were used. Regarding the different materials, metals and alloys have the advantage of superior strength, but for color, it is esthetically not acceptable. Due to a lack of esthetic value metals are replaced by ceramics.&#x0D; Objective: To compare the effect of two different marginal geometries shoulder and deep chamfer on metal-ceramic copings fabricated with the use of three different die materials Conventional Type IV Gypsum, epoxy resin, resin-modified Gypsum (Synthetic Gypsum).&#x0D; Methods: Two ivorine mandibular first molars were prepared using diamond points for receiving Full veneer porcelain fused to metal restorations. The two designs of circumferential finish evaluated in this study were shoulder and deep chamfer.&#x0D; Results: Tests specimen fabricated on 3 groups of die material each having shoulder and deep chamfer finish line were analyzed under a stereomicroscope at four points, following results of vertical marginal gaps in μm were recorded.&#x0D; Conclusion: It is thus concluded from the above study that dies fabricated using three different materials in two different finish lines i.e shoulder and deep chamfer did not exhibit a statistically significant difference in terms of marginal accuracy and either of these finish lines can opt for fabrication of metal-ceramic restorations.

Replacement of Two Failed Indirect Restorations with Direct Bonded Restorations Using Minimally Invasive Strategy

Deciding on what treatment (repair or replacement) to provide for a failed indirect restoration can be challenging. Notably, the strength of the residual tooth structure could be improved after replacing the failed indirect restoration using a minimally invasive strategy. Objective: To describe the use of a minimally invasive strategy for the successful clinical replacement of two failed indirect metal restorations with direct composite restorations and the attainment of bonded restoration. Case Report: Case 1. A 52-year-old male patient came to the dental hospital complaining of discomfort when drinking cold beverages and food impaction on the proximal area of the upper left first molar. Case 2. A 45-year-old female patient complained about her debonded metal onlay and secondary caries in the upper right second molar. Both of these indirect restoration failures were treated with direct resin composite restoration. Both patients were highly satisfied with the results. Conclusion: This report presents the benefits of adopting a minimally invasive strategy approach for replacing failed indirect restorations (inlays and onlays) with direct-bonded composite restorations. Minimally invasive direct restorations are designed to maximize the preservation of tooth structure, thereby ensuring a long-term bonded restoration and leaving future options open when a failure occurs.