Acid-resistant Enamel Research Articles

Avitaminosis A y trastornos de desarrollo dentoalveolar

Numerosas investigaciones han demostrado los efectos adversos de la hipovitaminosis A en el campo estomatológico, caracterizados por atrofia de las células ectomesenquimales y desordenada hiperactividad osteoblástica durante la fase del desarrollo embrionario; sin embargo, es limitada la información acerca de las manifestaciones histológicas por deficiencia en etapas posteriores al nacimiento; teniendo en cuenta que somos un país en desarrollo con problemas nutricionales no resueltos. El presente estudio se realizó con el objetivo de establecer los cambios morfológicos del complejo dentoalveolar presentes, después del nacimiento, por deficiencia de vitamina A; para lo cual, se empleó 20 ratas Holstman, de 21 días de edad, alimentados con dieta carente de vitamina A. El grupo control en adición recibió semanalmente una dosis de 100 V.L de retinol a fin de completar el balance dietético normal. Los cortes histológicos obtenidos por métodos convencionales, después de 7 y 8 semanas de fase experimental, de incisivos de rata con avitaminosis A, mostraron en la base odontogénica, aposición adamantina ácido resistente, que va de O a 3 M de espesor (Fig.3), con ameloblástos cilindricos funcionalmente inhibidos; en algunos casos, con pérdida de sus conexiones plasmáticas laterales. Además, presenta diferenciación de odontoblastos bucales con reducida producción de matriz dentinaria y ausencia de odontoblastos linguales (Fig.3). La pulpa dentaria adyacente a las células especializadas es mesenquimatosa y vascularizada (Fig.3). Los cortes longitudinales y transversales coronarios de molares de rata con avitaminosis A, muestran un complejo dentinopulpar con escasa producción de predentina, en algunos casos no existe. El complejo periodontal mostró un aparente engrosamiento de la cresta alveolar, sin muestras de remodelación (Fig.4). Los cambios morfológicos del complejo dentoalveolar presente en la avitaminosis A, probado con chi cuadrado a un nivel de confianza del 99%, es altamente significativa (ver gráficos 1-7).

Effect of alkali metal oxides on the properties of titanium containing glass enamels

The effect of the ratio of three alkali oxides on the physical and chemical properties of titanium-containing enamels has been investigated and their optimal concentrations have been determined. Acid resistant enamel for steel utensils has been developed.

Resistance of an enamel-bonding agent to saliva and acid exposure in vitro assessed by liquid scintillation

Objectives: To determine the leakage and resistance of a bonding agent and a light-curing fine hybrid composite when exposed to saliva or lactic acid (pH 4) in vitro. Methods: Twenty discs in each of four groups of selected irradiated bovine lower central incisors were treated with one of three sealing options: an enamel bond (Heliobond, Vivadent, Schaan, Liechenstein) in a single-step application; Heliobond in a two-step application; and Tetric Flow (Vivadent) as the negative control. One group served as the positive control and remained unsealed. Loss of apatite was determined using the radiochemical method of liquid scintillation. The Cherenkov radiation was assessed in order to evaluate the acid resistance and leakage of smooth surface enamel bonding after exposure to saliva and lactic acid. In addition, replicas were made for SEM analysis of micromorphologic surface changes. Results: A mean loss of 416.5 μg (s.d. 57.0) apatite was observed over the unsealed sites following 14 days of exposure to lactic acid. The application of Heliobond in a one- and two-step application still revealed a remarkable degree of leakage, and substance losses of 196.5 μg (s.d. 38.9) and 161.8 μg (s.d. 39.7), but a protective potential was evident. In saliva, untreated, as well as sealed teeth, showed a modest leakage that was less than 20 μg. When Tetric Flow was used (negative control) leakage was reduced to a minimum of 2.4 μg (s.d. 1.0) in saliva and 12.8 μg (s.d. 19.6) in lactic acid. These results were confirmed by SEM analysis. Significance: The method of liquid scintillation was revealed to be of considerable value in evaluating leakage and acid resistance of potential smooth enamel sealing options. Sealing with an unfilled resin still demonstrated remarkable levels of acid dissolution, although a protection tendency could be observed. This leads to the conclusion that there is a need for further investigation to establish more acid-resistant enamel sealing agents.

Glass enamel and glass-ceramic coatings for chemical apparatus

Among the known anticorrosion coatings used in chemical engineering, glass enamel base coatings are distinguished by such advantages as a high degree of continuity and chemical resistance. The paper describes basic principles for the creation of acid and alkali resistant glass enamel and ceramic coatings for chemical apparatus. As the result of investgations, glass enamel coatings with increased electrical conductivity and also experimental production compositions of chemical, temperature and radiation resistant coatings for protection of chemical equipment of 12Kh18N10T stainless steel have been developed. The coatings have successfully passed testing under service conditions. A new type of coating is short-term glass enamel, which may be recommended for use in chemical machinery manufacturing and other branches of industry in oxidation-free heating and forming of stainless steels.

Effect of sitallization on the chemical stability of acid-resistant titanic enamel

Effect of sitallization on the chemical stability of acid-resistant titanic enamel

Composition and structure of dental enamel: Elemental composition and crystalline structure of dental enamel as they relate to its solubility

The same elements, 21 in number, were found in both acid-resistant and acid-susceptible enamel specimens by ion microprobe analyses. However, there were differences in the concentrations of 14 elements between groups. Of the 16 trace elements found in enamel, the concentrations of K, F, and Na in parts per million were the greatest. Enamel surface analyses showed V and Zn were more concentrated in acid-resistant specimens by factors of 7.4 and 6.1 respectively, followed by nine other elements, the last molybdenum, that were just slightly more prevalent in acid-resistant enamel. Four elements were equally concentrated in both groups of samples, and only one trace element, B, was more abundant in the acid-susceptible samples by a factor of ten. Ca and P were predominantly more abundant in acid-resistant speciems, and C, H, and O were more concentrated in acid-susceptible samples. The enamel substance in acid-resistant and acid-susceptible groups was found to be similar by these methods. --Ion microprobe: the same elements were detected in both groups. Four trace elements (titanium, lead, Cl, and lithium) were equally abundant in the two groups. --Electron diffraction: the crystal structure type was the same in both groups of samples. --Infrared absorption: the crystalline substance showed the same spectra in both groups. The enamel substance in the two groups of specimens was found to be dissimilar by these methods. --Ion microprobe: the concentrations of 11 trace elements as well as Ca and P were greater in acid-resistant enamel. The concentrations of C, H, O, and B were greater in acid-susceptible enamel. --X-ray diffraction: crystallites in the acid-resistant specimens were larger by a factor of more than two. Enamel solubility appears not to be related to atomic species but associated with one, some, or all elements quantitatively and also with its physical form (crystallite size and probably density).

The stability of acid-resistant enamel coatings at high temperatures and pressures

The stability of acid-resistant enamel coatings at high temperatures and pressures

Improving the thermal and mechanical properties of highly acid resistant enamel coatings by controlled crystallization

Improving the thermal and mechanical properties of highly acid resistant enamel coatings by controlled crystallization

COMPARISON OF VARIOUS ANTIMONATES AS OPACIFIERS IN DRY‐PROCESS ENAMELS FOR CAST IRON*

AbstractAntimonates of potassium, lithium, barium, calcium, magnesium, strontium, zinc, aluminum, lead, and tin were substituted for sodium antimonate in an acid‐resisting dry‐process enamel for cast iron. The sodium antimonate content of this high‐lead enamel was also varied to permit comparisons of all antimonates with sodium antimonate, as a standard, on an equivalent antimony pentoxide basis. Reflectance, color, and acid‐resistance data on all enamels are presented.A number of the antimonates were compared as replacements for sodium antimonate in non‐acid‐resisting enamels of the lead‐bearing and leadless types. Reflectance and color data are given.In acid‐resisting enamels, antimonates of potassium and barium compared reasonably well with sodium antimonate in opacifying power without introducing objectionable colors. Barium antimonate also produced improved acid resistance.In non‐acid‐resisting enamels, only barium antimonate produced results approaching sodium antimonate in both leadless and lead‐bearing types.The data indicate that the antimonates do not contribute equally to opacity and color, even though all contain antimony in pentavalent form. Barium antimonate most closely approaches sodium antimonate in effectiveness. The behavior of the antimonates suggests an explanation for the variations often encountered with antimony oxide enamels.

PRACTICAL THICKNESS OF PARTIAL COATINGS OF ACID-RESISTANT ENAMEL*

The effect of the firing cycle, fluidity of enamel glasses, water content of enamel slips, method of application, fineness of grind, and opacifiers on the actual thickness of partial acid-resistant enamel coatings, measured by the Shartsis and Harrison method, is discussed. The results of this study appear to explain the failure of highly acid-resistant enamels to produce satisfactory acid resistance in some enameling plants.

ELECTROLYTES IN ACID-RESISTING ENAMELS*

The effect of various electrolytes on the acid resistance, “set,” and defects of acid-resisting enamels was studied. The defects encountered were scumming, pitting, and shorelining. It was found that (1) insufficient set caused scumming which was aggravated by aging the enamel; this defect may be eliminated by increasing the set of the enamel; (2) one of the enamels studied had a marked tendency to shoreline whenever a sulfate or an electrolyte containing the sulfate radical was used; and (3) the pitting tendency of one enamel was traced to the high soluble salt content of the mill liquor; this defect was eliminated by spraying the enamel at a high gravity or by applying the acid-resisting enamel in a heavier coating. Some of this work has been continued in regular plant practice, and a discussion of this phase of the work is included.

RELATION OF PARTICLE SIZE AND CHARACTERISTICS OF LIGHT REFLECTED FROM PORCELAIN ENAMEL SURFACES*

Various opacifiers were added in increasing percentages to clear, regular white, very opaque white, and acid-resisting enamels. These were ground to various degrees of fineness from coarse down to a few microns or finer; they were applied to sample plates and their reflectances were measured. Increased opacity is obtained by extremely fine milling because of the excellent dispersion of the opacifiers.

SOME FACTORS INFLUENCING PROPERTIES OF ACID-RESISTING ENAMELS *

The effect of metal gage, firing treatment, drying method, application methods, and base-coat compositions upon acid resistance and other physical properties, both alone and in combination, was determined upon three acid-resisting enamels of widely varying types. The firing treatment and application method, especially in combination with the metal gage, were found to affect acid resistance, while all of the other factors affected physical characteristics. The type of enamel and application method controlled the degree of the effect of the factors. Dust coats were found to be more sensitive to variable factors of production than heavier applications.

A PECULIARITY OF SHEET-IRON ACID RESISTING COVER COAT ENAMELS*

It has been demonstrated that the small bare spots evident in the first coat of acid-resisting enamel applied directly upon the ground coat are not necessarily the result of a process fishscaling in the ground coat during the firing operation, but are more often the result of reboiling of the ground-coat enamel and lack of film strength in the yet unfused layer of acid-resisting enamel. Reboiling, or other mechanical movements of the ground coat, may promote defects in acid-resisting enamels which would not be visible in those of the nonacid-resisting type, particularly when these enamels are applied directly upon the ground coat. The electrolytes used with acid-resisting enamels are directly connected with the popping condition noted. A choice of the proper kinds and amounts of electrolytes for “setting-up” the enamel can, in some cases, eliminate or minimize this trouble. The use of a nonacid-resisting enamel, properly set up as an intermediate layer between the ground coat and the finish coat of acid-resisting enamel, will also prevent troubles of this kind. The tendency for this peculiar defect to occur depends also upon the type of enameling base metal used and its tendency to reboil.

ACID-RESISTING WHITE DRY PROCESS CAST-IRON ENAMELS1

Beginning with simple compositions containing only those constituents necessary to make a glass, additions were systematically made in the development and study of acid-resisting enamels. It was found that the acid resistance depends on the proper combination of constituents rather than the presence or absence of any particular material. It was shown that all fluorine compounds are detrimental to acid resistance but experience shows that some form of fluorine is necessary to obtain good quality opacity. Smelting, if properly done, milling, and firing have practically no effect on the acid resistance.

THE DEVELOPMENT OF ACID-RESISTING WHITE SHEET STEEL ENAMELS1

Many of the commercial sheet steel enamels are readily attacked by such weak acid solutions as fruit juices and are stained by milk and by some city waters. This paper gives the development of a number of acid-resisting enamels. It shows that acid resistance is the result of the right combinations of raw materials rather than the presence or absence of any particular constituent. Acid resistance is not affected by fineness of grinding or by the smelting conditions if the enamel is properly smelted. Mill additions of clay reduce the acid resistance but opacifiers added in this manner have no effect. Temperature and time of firing may or may not affect the acid resistance depending on the composition of the enamel.

ACID-RESISTANT ENAMELS1

The qualities of an acid-resisting enamel are enumerated. Kerstan's formulas are given and results of tests made on the enamels of these formulas are discussed.

SOME RELATIONS OF COMPOSITION TO SOLUBILITY OF ENAMELS IN ACIDES1

Review of literature.—The literature on acid resisting enamels and glasses is reviewed. Acid resisting powers produced by different oxides.—When substituted one for another, in each case in equal percentage amounts, various oxides and minerals increased the resistance of various enamels to the action of boiling 20 per cent hydrochloric acid in the following order of effectiveness: Al2O3, cryolite, Na2O, PbO, BaO, Li2O, MgO, CaF2, ZnO, SrO, CaO, B2O3. The first five mentioned were especially effective. The remainder are undesirable materials from the standpoint of acid resistance. Effect of the enamel base.—The relative effects of the materials were the same for various base enamel compositions. Effect of ZrO2 and TiO2.—ZrO2 and TiO2, when substituted for small amounts of SiO2, increased the resistance of various enamels to attack by acids, ZrO2 being most effective in this respect. The favorable action of ZrO2, is offset by a tendency to produce excessive chipping. Rutile gives less chipping than either zirconia or silica and greater acid resistance than silica. Best compositions.—Enamels 2,17,19,26,27, and 33 of table 1 showed resistance to action of the acid equivalent to that of the original competitions based on the analysis of a French acid-resisting enamel. By use of the data developed in this investigation other highly acid-resisting compositions can readily be formulated.