Causes Of Discoloration Research Articles

Color-Stable Formulations for 3D-Photoprintable Dental Materials.

Color stability is crucial for dental materials to ensure they perfectly match a patient's tooth color. This is particularly challenging in photoresist-based additive manufacturing. Although some studies have addressed this issue, the exact causes of discoloration and ways to minimize it remain unclear. In this study, the intrinsic causes of discoloration in materials intended for 3D printing are investigated by examining thin-film samples (1200 µm) of various compositions, which are stored under different conditions. The samples are evaluated by measuring the UV-Vis absorption spectra at regular intervals to monitor changes. The findings reveal that both the composition of the formulations and the storage conditions significantly influence the discoloration behavior. Furthermore, methods have been developed to reduce or completely prevent discoloration. The use of photoinitiators with sterically demanding benzoyl moieties, as well as the addition of stabilizers, effectively decreases the intensity of emerging discoloration. Furthermore, incorporating the oxidizing agent cumene hydroperoxide (CHP) results in materials that maintain color stability.

Characteristics of the Discoloration Switching Phenomenon of 4H-SiC Single Crystals Grown by PVT Method Using ToF-SIMS and Micro-Raman Analysis.

The discoloration switching appearing in the initial and final growth stages of 4H-silicon carbide (4H-SiC) single crystals grown using the physical vapor transport (PVT) technique was investigated. This phenomenon was studied, investigating the correlation with linear-type micro-pipe defects on the surface of 4H-SiC single crystals. Based on the experimental results obtained using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and micro-Raman analysis, it was deduced that the orientation of the 4H-SiC c-axis causes an axial change that correlates with low levels of carbon. In addition, it was confirmed that the incorporation of additional elements and the concentrations of these doped impurity elements were the main causes of discoloration and changes in growth orientation. Overall, this work provides guidelines for evaluating the discoloration switching in 4H-SiC single crystals and contributes to a greater understanding of this phenomenon.

Causes of Discoloration of Dental Fillings in Adults: A Systematic Review

The purpose of this investigation was to carry out an exhaustive review of the relevant previous research in order to ascertain the underlying causes of the observed discoloration and determine which component, if any, was to blame. A number of phrases taken from previously conducted systematic reviews were used in the search conducted in PubMed. There were a total of 389 teeth treated across eleven different trials that were discovered. Although it was seen more often with the use of the triple antibiotic paste that included minocycline, discoloration was shown to be substantially associated with the utilisation of other components as well. It is strongly suggested that you reevaluate your decision to use minocycline as the intracanal drug in conjunction with the other two antibiotics in the paste. The use of calcium hydroxide or an antibiotic paste containing both metronidazole and ciprofloxacin could be necessary in order to achieve the desired level of discoloration control. The presence of mineral trioxide aggregate was also associated with the discoloration. On the other hand, there is little evidence to suggest that any other material could possibly function as an acceptable coronal barrier. Because discoloration is a result that has a direct impact on patients, further research is required to determine the underlying causes of discoloration.

Drug induced tooth discoloration in pediatric group: a review

Teeth stains and discoloration are regular occurrences that can arise for a variety of causes. What we eat /drink, ageing and tooth trauma are the most common causes of discoloration. Medications can also cause tooth discoloration, either directly or indirectly. It is our job as health professionals to be aware of the therapeutic treatments that have the potential to stain teeth and to enlighten the general public on how to take the required steps while administering the drugs. This article discusses some of the most common drugs that cause tooth discoloration in children.

Assessment of clinical and etiological factors in nail dyschromias

Healthy nails appear smooth and have consistent coloring. Nail dyschromias have a wide variety of presentation. There are numerous causes of discoloration of the nail affecting the nail plate, nail attachments, or the substance of the nail. Different pattern of nail dyschromias can point out certain dermatological or systemic diseases. To evaluate the causes of nail dyschromias in our clinical setting. Cross sectional observational study. 200 patients presenting with nail dyschromias were included in the study from April 2015 to July 2015. Detailed history was taken and cause for nail dyschromias was evaluated. 115(57.5%) were males and 85(42.05%) were females. The most seen nail dyschromia in this study was melanonychia (86.5%) followed by leukonychia (5%), blue chromonychia (5%), brown chromonychia (2%) yellow chromonychia (1.5%). The cause of nail dyschromias were:60 cases(33.33%) were due to antiretroviral drugs, 25(12.5%) due to HIV, 30(15%) physiological melanonychia, 7(3.5% of onychomycosis, 8(4%) of lichen planus, 7(3.5%) of eczema, 15(7.5%) vitamin B12 deficiency, 10(5%) chemotherapy induced blue chromonychia, 3(1.5%) haematoma, 10(5%) leukonychia, 3(1.5%) jaundice 2(1%) Addison’s disease induced, 3(1.5%) cosmetic induced and 17(7.5%) due to other dermatological and systemic conditions. Examination of nail should always be a part of routine cutaneous examination and presentation with nail dyschromias should be worked up with the help of a good history and examination. Careful examination of the nail may help in identifying the root cause and many a times unravels some underlying systemic disorder

Management of the single discoloured tooth. Part 1: Aetiology, prevention and minimally invasive restorative options.

The single discoloured tooth is commonly encountered in general practice. This is the first of two articles covering the broad range of management options for the single discoloured tooth. This first part outlines the common causes of discoloration and possible methods of prevention. Minimally invasive techniques are covered. Clinical procedures are outlined and clinical cases used to demonstrate outcomes that can be achieved. The single discoloured tooth is a commonly encountered clinical problem in general dental practice. A wide variety of management options exist and any one in particular may be most appropriate given the clinical scenario. It is therefore essential that general dental practitioners are familiar with the range of options that exist, as well as their indications, and consider adopting minimally invasive techniques in the first instance before moving to more invasive therapies.

Nail dyschromias

Nail dyschromias have a wide variety of presentation. There are numerous causes of discoloration of the nail affecting the nail plate, nail attachments, or the substance of the nail. The chromonychia may also be caused due to the exogenous deposition of pigments over the nail plate. Careful examination of the nail and few bed side tests may help in identifying the root cause of the nail dyschromia and many a times unravels some underlying systemic disorder too.

In vivo measurements of daily UV exposure of human anterior teeth using CaF2:Tb,Sm as a thermoluminescence dosimeter

Abstract Ultraviolet radiation (UV) has been indicated as one of the causes of discoloration of dental materials yet the ISO 4049 (2009) standard requires that dental polymers be irradiated with light from a xenon lamp, which includes UV, to evaluate their color stability. It is doubtful that dental polymers in the mouth are exposed to large energy of UV on a daily basis, but there have been no reports concerning exposure. In the present study, we used thermoluminescence (TL) from sintered CaF 2 :Tb,Sm, which is highly sensitive to UV, to measure the daily energy of UV exposure to the labial surface of the maxillary anterior teeth, which are regarded as receiving the maximum exposure among oral tissues. We produced disks of CaF 2 co-doped with Tb 4 O 7 and Sm 2 O 3 (sintered CaF 2 :Tb,Sm) that were 5 mm in diameter and 1 mm thick, and placed them inside glass cases that had a 7-mm external diameter, 3-mm height, and 1-mm thickness of glass made of synthetic silica with ≥90% UV transmittance. These glass cases were fixed in dental mouthpieces in a position corresponding to the central maxillary incisors. These mouthpieces were worn by 11 subjects and UV measurements were carried out over a 24-h period in a uniform environment. The results of these TL measurements showed a TL glow peak in the region of 430 K. This was the same as that seen with irradiation from a xenon lamp as basic illumination. The daily UV radiant energy was 72.2 mJ/cm 2 (32.7–143.8 mJ/cm 2 ), calculated from the relationship between TL intensity and UV radiant energy. This corresponded to 0.02% of the UV radiant energy contained in the light irradiation specified by ISO 4049.

Colour alteration and chemistry changes in oak wood (Quercus pedunculata Ehrh) during plain vacuum drying

The formation of chromophore groups from a phenolic compound oxidized with air and the formation of dark materials from hydrolysable extractives are considered as causes of discoloration. In this work, the colour changes, antioxidant capacity, and Fourier Transform Infrared Spectra of dust-wood are investigated in European oak wood under different plain vacuum drying conditions. The conductive heat source is maintained at four temperatures (46, 61, 70 and 80°C), and vacuum in the chamber is controlled at three different intervals (60–100, 150–200, and 250–300 mbar). Drying kinetics and temperature profiles are presented. The results suggest that degradation of extractives allows yellowing in wood and temperature improves lightness under these special drying conditions (plain vacuum). Furthermore, the presence of carbonyl groups in surfaces is related to the loss in antioxidant potency.

TYPES OF TOOTH DISCOLORATION IN ADULTS OF RAMADI CITY, AL-ANBAR PROVINCE, IRAQ: STATISTICAL STUDY

: During the period June 2005 to June 2006, 158 patients with teeth discoloration were interviewed regarding the causes of discoloration. Most common cause of discoloration teeth in females was the caries, whereas trauma and dentin development problems were the most common two causes of teeth discoloration in males.

Susceptibility of oat cultivars to groat discoloration: causes and remedies

AbstractFungal isolations and fungicide efficacy trials were carried out to determine the possible causes of discoloration in oat groats and potential control measures. Alternaria species and Microdochium nivale were isolated from field samples, and Fusarium poae was found in glasshouse tests. Symptoms could be induced reliably in the field through the use of a mist irrigation system. The cultivar ‘Gerald’ was most resistant followed by ‘Jalna’. Cultivar ‘Image’ was most severely affected by discoloration and ‘Millennium’ was of intermediate susceptibility. None of the 28 fungicide‐timing combinations used in the field trials affected the occurrence of discoloured groats. It was concluded that the best strategy for minimizing risk of discoloured groats would be screening new cultivars or breeding material in mist‐irrigated field trials for genetically based resistance.

Dişlerde oluşan renk değişiklikleri ve bunların giderilmesi

SUMMARY In this article, the causes of discoloration has been discussed. The technique of bleaching and effects of hydrogen peroxide as a bleaching material has been illustrated.

Internal Protective Coatings for Latex Containers. Investigations of Internal Protective Coatings for Latex Containers and Their Value in Minimizing Discoloration in Preserved Latex

Abstract In a previous publication (cf. J. Rubber Res. Inst. Malaya, 5, 176 (1934); Rubber Chem. and Tech., 7, 433(1934) the present authors have discussed fully the causes of discoloration in preserved latex and have shown that the iron drum which is in common use as a latex-shipment vessel is in itself a predisposing factor in the discoloration of latex. Users do not however look with favor on the substitution of a non-metallic container for the steel drum, and since suitable alternative metallic containers are prohibitive in cost, there remains little alternative but to endeavor, by the internal application of some protective medium, to reduce to a minimum the objectionable effects of the iron drum on its contents. Since discoloration is due to the formation of dark-colored colloidal and amorphous sulfides of iron, a satisfactory drum-coating medium should prevent contact of the latex with the iron of the drum, and also if possible react with any sulfur compounds which may be liberated in the latex, to form sulfides which are either white in color or so nearly white that when present in latex they are not detectable by the eye. It is essential that the coating should not be so brittle as to crack or flake away from the metal when drums are roughly handled in transit. If flaking occurs, serious contamination of the latex may result. The requirement is a tough, elastic film which will adhere well to the metal and which will not be appreciably affected by long contact with ammoniated latex, except in so far as it may combine with sulfur compounds to produce a white product.