Experimental Study on the Mechanical Behavior of Orthodontic Arches Exposed to the Environment in the Oral Cavity

Background. The arches used in orthodontic therapy are subject to increasing physical and chemical stresses. Purpose of the study: This in vitro experimental study aims to highlight and compare the main mechanical properties of orthodontic arches. Materials and Methods: We used 40 springs, 2 materials, 20 of Ni-Cr and 20 of Co-Cr, of different diameters, 0.7 mm 0.8 mm and 1.2 mm, subjected to the environment of artificial saliva and artificial saliva with cola for one month and two months, respectively. Five springs of each material were tested at different times: T0, before application in the oral cavity, then at time T1, T2, T3, T4. Three lengths of the lever arm were considered for bending forces acting on the springs (dental wires). These lengths were 15, 10 and 5 mm. The wires were tested under the action of bending forces on a Hans Schmidt HV 500N stand, obtaining the characteristics of the wires: deformation-force-time. Results: Graphical determinations show that the degree of deformation of the wires is influenced by the applied force, diameter and obviously by the immersion time, respectively by the type of solution in which the springs were immersed. Conclusions: The final degree of bending is higher for Co-Cr arcs than for Ni-Cr at all three dimensions.

Spectral image contrast-based flow digital nanoplasmon-metry for ultrasensitive antibody detection

Background Gold nanoparticles (AuNPs) have been widely used in local surface plasmon resonance (LSPR) immunoassays for biomolecule sensing, which is primarily based on two conventional methods: absorption spectra analysis and colorimetry. The low figure of merit (FoM) of the LSPR and high-concentration AuNP requirement restrict their limit of detection (LOD), which is approximately ng to μg mL−1 in antibody detection if there is no other signal or analyte amplification. Improvements in sensitivity have been slow in recent for a long time, and pushing the boundary of the current LOD is a great challenge of current LSPR immunoassays in biosensing. Results In this work, we developed spectral image contrast-based flow digital nanoplasmon-metry (Flow DiNM) to push the LOD boundary. Comparing the scattering image brightness of AuNPs in two neighboring wavelength bands near the LSPR peak, the peak shift signal is strongly amplified and quickly detected. Introducing digital analysis, the Flow DiNM provides an ultrahigh signal-to-noise ratio and has a lower sample volume requirement. Compared to the conventional analog LSPR immunoassay, Flow DiNM for anti-BSA detection in pure samples has an LOD as low as 1 pg mL−1 within only a 15-min detection time and 500 μL sample volume. Antibody assays against spike proteins of SARS-CoV-2 in artificial saliva that contained various proteins were also conducted to validate the detection of Flow DiNM in complicated samples. Flow DiNM shows significant discrimination in detection with an LOD of 10 pg mL−1 and a broad dynamic detection range of five orders of magnitude. Conclusion Together with the quick readout time and simple operation, this work clearly demonstrated the high sensitivity and selectivity of the developed Flow DiNM in rapid antibody detection. Spectral image contrast and digital analysis further provide a new generation of LSPR immunoassay with AuNPs. Graphical Abstract

Causation of Oxidative Stress and Defense Response of a Yeast Cell Model after Treatment with Orthodontic Alloys Consisting of Metal Ions

Misaligned teeth have a tremendous impact on oral and dental health, and the most efficient method of correcting the problem is orthodontic treatment with orthodontic appliances. The study was conducted to investigate the metal composition of selected orthodontic alloys, the release of metal ions, and the oxidative consequences that the metal ions may cause in the cell. Different sets of archwires, stainless steel brackets, and molar bands were incubated in artificial saliva for 90 days. The composition of each orthodontic material and quantification of the concentration of metal ions released were evaluated. Metal ion mixtures were prepared to determine the occurrence of oxidative stress, antioxidant enzyme defense system, and oxidative damage to proteins. The beta titanium alloy released the fewest metal ions and did not cause oxidative stress or protein damage. The metal ions from stainless steel and the cobalt-chromium alloy can cause oxidative stress and protein damage only at high concentrations. All metal ions from orthodontic alloys alter the activity of antioxidant enzymes in some way. The determined amounts of metal ions released from orthodontic appliances in a simulated oral environment are still below the maximum tolerated dose, and the concentrations of released metal ions are not capable of inducing oxidative stress, although some changes in antioxidant enzyme activity were observed at these concentrations.

Effect of pediatric drugs on solubility of restorative materials used in primary teeth

Background: Pleasant tasting syrups have a long history of use in pediatric practice to aid compliance with medication. Pharmaceutical firms sweeten liquid drug preparations with sucrose to increase the palatability which causes dental caries and erosion in children. In pediatric population, the commonly used esthetic restorative materials are glass ionomers, compomers or composites. Hence solubility of dental restorative materials are of considerable clinical importance and cannot be overlooked. Aims and objectives of current study were to evaluate the effect of commonly used pediatric drugs on the surface solubility of pediatric restorative materials.Methods: The study was conducted on 40 disc shaped specimens of GIC and composite immersed in artificial saliva and pediatric drugs, at 370C for 7 days to determine the solubility in pediatric drug formulations. The solubility of the specimens was calculated by a given formula by comparing the initial and final masses of the specimens.Results: In both GIC and Composite groups higher solubility was seen with paracetamol drug formulations. The mean solubility value of GIC was 0.14±0.02 and that of composite was 0.07±0.035, in paracetamol drug formulations.Conclusions: From the above experimental study it can be concluded that the solubility of restorative materials were comparatively higher in pediatric liquid medications with low pH. Among the drugs paracetamol showed increased erosive effects leading to solubility.

Bisphenol A Release from Dental Composites and Resin-Modified Glass Ionomers under Two Polymerization Conditions

Bisphenol A (BPA)-based monomers are commonly contained in dental resin-based materials. As BPA is an endocrine disruptor, its long-term release from restorative composites and resin-modified glass ionomers (RM-GICs) under two polymerization conditions was measured in this study. Specimens of two conventional composites containing BPA-based monomers, two “BPA-free” composites, and two RM-GICs were polymerized from one side for 20 s at 1300 mW/cm2 or for 5 s at 3000 mW/cm2. The amounts of BPA released in artificial saliva and methanol after 1, 4, 9, 16, 35, 65, 130, and 260 days were measured using liquid chromatography–tandem mass spectrometry. The highest amounts of BPA were released from conventional composites, followed by RM-GICs, while the least was released from “BPA-free” composites. Amounts of released BPA were significantly higher in methanol and decreased gradually after the first day. Fast polymerization (5 s at 3000 mW/cm2) resulted in a significantly higher release of BPA after 1 day, but the effect of polymerization conditions was not significant overall. In conclusion, fast polymerization increased the initial release of BPA, but the released amounts were significantly lower than the current tolerable daily intake (4 μg/kg body weight/day) even in methanol, representing the worst-case scenario of BPA release.

Effect of Water-Based Disinfectants or Air-Drying on Dimensional Changes in a Thermoplastic Orthodontic Aligner

The polymer structure of thermoplastic materials currently used to make aligners is altered by the oral conditions and this negatively affects their capacity to move teeth. This study aimed to compare different options for storing aligners when not in use by superimposing successive 3D images to identify which storage method least affects material shape and weight. Fifty PET-G aligners, produced using the CA Digital method, were divided into four groups (1A, 1B, 1C, and 2D) and were stored for 18 h a day in artificial saliva at 37 °C. Then, to mimic their storage conditions when not in use, aligners in group 1A were immersed for the remaining 8 hours a day in bicarbonate solution, those in group 1B in chlorhexidine solution, those in group 1C in distilled water, and those in group 2D were stored dry. The samples were scanned at the baseline (before the immersion cycles began) and again two weeks later. The digital scans were superimposed and the median deformation, its variability, and weight differences were recorded for each group. Statistical analysis showed aligner deformation (expansion) in all three groups stored in wet conditions, with a statistically significant difference between groups 1A and 1C. Aligners in group 2D shrank slightly, and to a significantly greater degree with respect to group 1C. Variability in the degree of deformation was similar among the three groups stored in wet conditions, but significantly greater in group 2D. Weight gains were recorded in all four groups, the smallest in group 2D and the largest in group 1A. Storing aligners in dry conditions promoted lower deformation in the material, involving a slight shrinkage, whereas wet storage conditions caused an expansion of the aligner, especially when distilled water is used.

Preliminary study into the effects of tobacco smoke on Candida albicans

Background: Denture-stomatitis (DS) is the most common form of oral candidosis with increased prevalence in cigarette smokers (Akram et al. 2018). Interestingly, tobacco condensate (TC) increases Candida albicans adhesion, growth, biofilm-formation, virulence gene expression (Semlali et al. 2014)and hyphal production (Awad and Karuppayil 2018). We hypothesised that TC-treated denture acrylic would therefore affect C. albicans within acrylic biofilms. Methods: Acrylic discs (pre-conditioned with TC, artificial saliva (AS) or water) were incubated at 37°C with C. albicans (n=6) for 90 min or 24 h. Adherent Candida were stained with calcofluor white and confocal laser scanning microscopy (CLSM) used to assess levels of adherence, biofilm and hyphal numbers. Expressed virulence genes (n=7) were measured by qPCR. Results: CLSM showed that effects of TC-treatment were strain dependent. Adherence of C. albicans PTR/94 to TC-treated surfaces was significantly (P<0.002) lower than on the untreated control. Biofilm levels of PTR/94 after 24 h were found to be significantly higher on AS-treated acrylic than the TC-treated and untreated control. Five strains had significantly fewer filamentous forms after 90 min on TC-treated surfaces. TC-treatment promoted hyphal levels for strain 705/93 after 24h. Conclusion: TC pre-conditioning altered adherence and biofilm coverage of C. albicans to acrylic surfaces and influenced hyphal development. Work is ongoing to ascertain the significance of these effects on C. albicans pathogenicity. Akram et al. (2018). Journal of Oral Science 60(1):115–120. Awad and Karuppayil (2018). American Journal of Clinical Microbiology and Antimicrobials1(3):1–6. Semlali et al. (2014). BMC Microbiology. 14:61

Comparative Evaluation of the Amount of Sorption and Solubility Seen in Soft Liner with Herbal and Commercially Available Denture Cleanser - An In vitro Study

Aims: the aim of the current study is to assess the quantity of sorption and solubility seen in the soft denture liner with herbal (neem) and commercially (clinsodent) available denture cleanser. Materials and Methods: The cross sectional study was carried out in the Department of Prosthodontics at Sharad Pawar Dental College And Hospital between February 2021 and July 2021. 52 samples of heat cured acrylic resin of circular shape were prepared using a stainless steel mould. The resilient liner was applied to all the samples using a denture adhesive. All samples will then be desiccated for 24 hours to get a stable or conditioned weight W1. The samples will then be divided into 2 groups namely: Group A (clinsodent group) and the Group B (herbal denture cleanser group). All the samples were immersed daily in cleanser for 8 hour and then transferred to artificial saliva for rest 16 hours of the day. Solutions of artificial saliva and denture cleanser was changed daily for the entire period of study that is 7 days. Later, all the test samples were removed from saliva, wiped dry, weighed for saturated weight W2. - After desiccating again for 24 hours the samples were again assessed for renovated weight that is W3. Results: With respect to sorption and solubility it was found that the clinsodent group exhibited greater percentage of sorption when compared to the neem denture cleanser group after a period of 7 days, p-values of 0.0001,S. Conclusion: It can be established that the solubility and sorption values of clinsodent group were higher when compared to the herbal denture cleanser group. Overall, neem in the form of denture cleanser performed better than clinsodent.

COMPARISON OF THE CORROSION PROPERTIES OF CoCrMo DENTAL ALLOYS IN ARTIFICIAL SALIVA

CoCrMo alloys are known for their biocompatible properties, which, together with their favorable mechanical properties, mean they can be efficiently used in dentistry. With the development of selective laser melting for the fabrication of 3D printed objects, interest in the corrosion properties of this alloy has risen in the field of prosthodontics. In the study, CoCrMoW dental alloys were studied in artificial saliva at body temperature i.e. 37 °C. Different forms of CoCrMoW alloy were selected: a reference sample, i.e. original material as-received from the supplier, a casted sample acquired from an ordinary procedure in a dental laboratory, and two 3D printed samples made from CoCrMoW powder using the selective laser melting method (SLM). Electrochemical, spectroscopic and hardness measurements were conducted. It was shown that the reference and cast samples have similar microstructural and electrochemical properties, while the electrochemical properties of the 3D printed samples differ, most probably due to the effect of the higher micro porosity and chemical composition of the alloys.

Characteristics of respiratory microdroplet nuclei on common substrates

To evaluate the role of common substrates in the transmission of respiratory viruses, in particular SARS-CoV-2, uniformly distributed microdroplets (approx. 10 µm diameter) of artificial saliva were generated using an advanced inkjet printing technology to replicate the aerosol droplets and subsequently deposited on five substrates, including glass, polytetrafluoroethylene, stainless steel, acrylonitrile butadiene styrene and melamine. The droplets were found to evaporate within a short timeframe (less than 3 s), which is consistent with previous reports concerning the drying kinetics of picolitre droplets. Using fluorescence microscopy and atomic force microscopy, we found that the surface deposited microdroplet nuclei present two distinctive morphological features as the result of their drying mode, which is controlled by both interfacial energy and surface roughness. Nanomechanical measurements confirm that the nuclei deposited on all substrates possess similar surface adhesion (approx. 20 nN) and Young's modulus (approx. 4 MPa), supporting the proposed core–shell structure of the nuclei. We suggest that appropriate antiviral surface strategies, e.g. functionalization, chemical deposition, could be developed to modulate the evaporation process of microdroplet nuclei and subsequently mitigate the possible surface viability and transmissibility of respiratory virus.