On the solubility of zinc in the gamma-phase of the silver-mercury system.

By measuring lattice constants of a number of Ag-Hg-Zn alloys with gamma-phase structure, it has been shown that apart from a possible two-phase field there exists a continuous solid solution between gamma (Ag-Hg) and gamma (Ag-Zn). A correlation between the Zn-content in the gamma 1 phase in set dental silver amalgam and the Zn-content in the corresponding alloy has been determined.     

Twinning in γ-crystals of the silver-mercury system

abstract – This X-ray diffraction study of γ(Ag-Hg)-crystals formed by the reaction between an aqueous solution of silver nitrate and mercury has shown that the crystals are twinned and that the most common form of twinning can be described either as a reflection across the cubic (2     )-plane or as a 180° rotation around the [2     ]-direction.     

The effect of topically applied fluorides on the surface free energy of human dentin

The surface free energy γ_s of human dentin treated with sodium fluoride, acidulated phosphate fluoride, and aminfluoride solutions has been determined by means of contact angle measurements. Application of an aminfluoride solution slightly increased the total surface free energy from 75 to 80 erg. cm⁻². The γ_s values of dentin after a neutral sodium fluoride application decreased to 62 erg. cm⁻². APF solutions hardly influenced the surface free energy γ_s. This study showed that fluoride applications change the surface free energy of human dentin.
Extrapolation of the results of this study and the in vitro results on cell spreading indicated that aminfluoride applications might be favorable for the reattachment of periodontal tissues.     

Improvements of in vitro cell-material adhesion measurements

The in vitro measurement of gingival cell-bacto agar substratum adhesive-bonding strength (γ_a) is described as it relates to cell- concentration, cell-substratum contact time and serum concentration. These three factors are critical in obtaining reprocible γ_a's for gingival cell-test substratum interactions.
Cell concentrations of less than 35 × 10³ cells per cm² gave low γ_a's (70–75 ergs/cm²) whereas 90–130 × 10³ cells/cm² resulted in γ_a's of 109–119 ergs/cm², respectively. Maximum γ_a's (123 ergs/cm²) resulted after the cells had been in contact with the agar substratum for 24 hours. The adhesive-bonding strenth after eight housrs of contact time, however, was not statistically different from the 24 housr readings and has the advantage of decreasing the test duration. Serum, and important factor for optimum adhesion measurements, produced a peak γ_a at the 10 % concentration.     

Neutron diffraction study of the γ-phase in the silver-mercury system

abstract – A neutron diffraction study of the γ-phase in the Ag-Hg system has given atomic coordinates in agreement with previous X-ray work. The Ag₁₁Hg₁₅-model with disorder in the 24-fold position has been confirmed.     

Electron microprobe analysis of the γ2 phase in dental amalgam

A bstract — The microstructure and composition of the γ₂ phase in four conventional lathe-cut or spherical amalgams were investigated using an electron microprobe.
In addition to its presence in the matrix, γ₂ phase was found, in lathe-cut amalgams, in contact with ε (Cu₃Sn) phase, separated from γ (Ag-Sn) phase by a thin band of γ₁ phase and, rarely, in direct contact with γ phase, and, in spherical amalgams, within the relict of partly reacted spherical particles. Inclusions of γ, γ ₁ and Cu-Sn phase were occasionally identified within regions of γ₂ phase. The major element composition of the γ₂ phase was similar in all amalgams (83.0 to 83.2 per cent Sn, 17.0 to 16.8 per cent Hg).     

Creep of dental amalgam

abstract — The steady-state creep rates of dental amalgams were measured and the creep rates were correlated with the microstructure of the amalgams. The influence of manipulation variables on creep rate and microstructure was evaluated. The samples were either mechanically or hand triturated, hand condensed, and stored at 20°C for 7 d. The specimens were subjected to a constant tensile load for 24 h, and the elongation was measured with a displacement transducer. The smallest creep rate was found on a spherical amalgam, and the highest on an amalgam made from a preamalgamated fine grain alloy. A correlation between microstructure and creep rate could be demonstrated. The amount of γ₂ phase did not seem to influence the creep rate. Amalgams that had large closely packed γ particles surrounded by a small volume fraction of γ₁ phase exhibited a low creep rate. Amalgams that had small broken up γ particles surrounded by a large volume fraction of γ₁ exhibited a high creep rate. Abusive manipulation of lathe-cut amalgam alloys resulted in high creep rates, small broken up γ particles and a high volume fraction of γ₁.     

Chemical composition and crystal structure of the γ-phase in the silver-mercury system

abstract – Chemical analysis, density measurement, determination of lattice constant, and X-ray diffraction analysis have been performed on crystals of the γ-phase in the silver-mercury system (γ1 in dental silver-amalgam). A chemical composition corresponding to Ag₁₁Hg₁₅ seems the most probable. The atomic coordinates are in accordance with previous work. The X-ray analysis shows that a disorder in the 24-fold position is probable.     

Intraepithelial lymphocytes bearing the γ/δ receptor in the oral and jejunal mucosa in patients with dermatitis herpetiformis

Lymphocytes bearing T cell receptor (TcR) γ/δ are increased in the jejunal mucosa of patients with dermatitis herpetiformis (DH) and coeliac disease. In this study, we examined whether increased numbers of γ/δ TcR positive lymphocytes occur in the oral mucosa of patients with DH. Oral and jejunal rnucosal biopsies were taken from 13 newly diagnosed and 13 gluten free diet (GFD)-treated patients with DH. Monoclonal antibodies and avidin-biotin peroxidase method was used for staining, and TcR positive cells were counted from the buccal and jejunal epithelium. Very few γ/δ TcR positive lymphocytes were seen in the buccal epithelium of untreated or GFD-treated DH patients (median 0.4 and 0.3 cells/mm²), whereas α/β TcR positive lymphocytes were frequent in both groups of DH patients (154 and 250 cells/mm²) and healthy controls (135 cells/mm²). The numbers of γ/δ TcR positive intraepithelial lymphocytes were significantly increased in the jejunum of both untreated (43 cells/mm) and GFD-treated (27 cells/mm) DH patients compared to control patients (2.2 cells/mm). The present study did not, therefore, disclose any evidence for active recruitment of γ/δ TcR positive lymphocytes in the oral epithelium, but showed substantial amounts of intraepithelial γ/β TcR positive lymphocytes both in DH patients and healthy controls.     

Phase content of a high copper dental silver amalgam

abstract – The phase content of a conventional zinc-free silver amalgam and a high copper silver amalgam has been determined by X-ray diffraction and by stoichiometric calculation. The γ2 content in the high copper amalgam is zero for low mercury contents and increases with rising mercury concentration. The γ2 content also rises with prolonged annealing of the alloy.     

Accelerated corrosion analysis of dental amalgams

Abstract – The corrosion of powdered conventional and high Cu dental amalgam was studied in vitro under fixed conditions (100% oxygen, pH 4, and constant weak mechanical action). Results were retrieved from X-ray diffraction of samples of amalgam and solid corrosion products Formed, in combination with recording of the HC1 consumed to maintain the fixed pH. In the conventional amalgam no corrosion of γ₁ occurred until all γ₂ had corroded, whereas in the high Cu amalgam corrosion of γ₁ occurred from the beginning, concurrent with corrosion of ε and ń. Corrosion products found were AgCl, Hg₂Cl₂, CuCl₂-3Cu(OH)₂, and SnO₂. The results may be interpreted as follows: in the conventional amalgam the matrix phase γ₁ is anodically protected against corrosion as long as any γ₂ remians; in the high Gu amalgam the least noble phases ε and ń do not protect γ₁ in a similar way.     

Stoichiometric and X-ray diffraction analysis on the γ2→η' transformation in a dispresant phase silver amalgam

Abstract— Phase composition of an amalgam prepared from a two-particle alloy was determined over a 2-year period by X-ray diffraction. The γ₂content decreased from 3.6% to 0.3%, and η' increased from 3.9% to 10/0%. These alterations in ph content agreed with stoichiometric calculations performed on the basis of the solid state reaction: γ₂+Ag/Cu→η'+γ₁     

Effect of inhibition of inducible nitric oxide synthase (iNOS) on the murine splenic immune response induced by Aggregatibacter (Actinobacillus) actinomycetemcomitans lipopolysaccharide

Animal studies suggest that inducible nitric oxide synthase (iNOS) may be associated with destructive periodontal disease. l- N ⁶-(1-Iminoethyl)-lysine ( l -NIL) has been shown to inhibit iNOS in a selective manner, and hence the aim of the present study was to test the hypothesis that treatment with l -NIL may induce a T-cell helper 1 (Th1)-like immune response by Aggregatibacter ( Actinobacillus ) actinomycetemcomitans lipopolysaccharide (LPS)-stimulated murine spleen cells in vitro . BALB/c mice were either sham-immunized or immunized with A. actinomycetemcomitans LPS. Spleen cells were stimulated with A. actinomycetemcomitans LPS in the presence or absence of l -NIL. Nitric oxide (NO), iNOS activity, specific IgG subclass antibodies, interferon- γ (IFN- γ ), and interleukin-4 (IL-4) levels and cell proliferation were determined. The results showed that treatment with l -NIL suppressed both NO production and iNOS activity but enhanced specific IgG2a, IFN- γ levels, and increased cell proliferation following stimulation with A. actinomycetemcomitans LPS-stimulated cells. The results of the present study suggest that inhibition of iNOS activity by l -NIL may skew the A. actinomycetemcomitans LPS-stimulated murine splenic immune response towards the Th1-like immune profile in vitro .     

The location of zinc in dental silver amalgam

abstract — The phases in amalgams prepared from alloys of varying zinc content and with varying alloy-to-mercury ratios have been determined by means of X-ray diffraction. By measuring lattice constants of the phases in these amalgams it has been established that the major part of the zinc, is dissolved in the γ₁ phase.     

Some observations on the fluids of odontogenic cysts

Abstract. The fluids of 44 dental cysts, 19 dentigerous cysts, 36 odontogenic keratocysts, and 12 ameloblastomas have been investigated. The incidence of epithelial cells, inflammatory cells, cholesterol crystals and bacteria was recorded in smears. There was a high incidence of epithelial cells in odontogenic keratocysts and not in other lesions. Cholesterol crystals had a similar incidence in all lesions. The proportion of the soluble proteins and total protein content was determined from cellulose acetate electrophoresis. Dental cysts contained an average of 51.19 % albumin, 17.52 %β globulin, 22.04 %γ globulin, and 6.30 g/100 ml protein. Dentigerous cysts contained an average of 61.35 % albumin, 13.98%β globulin, 12.70%γ globulin and 5.40 g/100 ml protein. Odontogenic keratocysts contained an average of 78.03 % albumin, 7.51 β globulin, 7.91 γ globulin, and 2.09 g/100 ml protein. Ameloblastomas contained an average of 67.38% albumin, 12.83%β globulin, 12.60 γ globulin and 4.86 g/100 ml protein. The immunoglobulin content was determined by single radial immunodiffusion. Dental cysts contained an average of 488.9 mg/100 ml IgA, 2535.4 mg/100 ml IgG, and 135.6 mg/100 ml IgM. Dentigerous cysts contained an average of 308.4 mg/100 ml IgA, 1618.2 mg/100 ml IgG, and 155.6 mg/100 ml IgM. Odontogenic keratocysts contained an average of 135.6 mg/100 ml IgA, 491.9 mg/100 ml IgG, and 54.1 mg/100 ml IgM. The significance of these findings in the pathogenesis and diagnosis of these lesions is discussed.     

Proteins in fluid from non-keratinizing jaw cysts.

Abstract. Fluid from 39 non-keratinizing jaw cysts was examined for protein and nitrogen by chemical methods. Follicular cyst fluid showed significantly lower concentrations of protein than did autologous serum. No statistically significant differences were found between fluid from apical periodontal and residual cysts on the one hand and autologous serum on the other, or between the different types of cyst fluids. Three non-odontogenic cyst fluids showed relatively lower quantities of protein than did most fluids from odontogenic cysts. Often cyst fluid exhibited higher ratios of nitrogen:total protein than did autologous serum. Scanning of cyst fluid cellulose acetate membrane electrophoretograms and the calculation of the protein content of the separated fractions revealed significantly higher amounts of γ-globulins, but lower levels of albumin, α₁ and α₂-globulins in cyst fluid than in autologous serum. The β-globulin fraction approximated that of autologous serum. No statistically significant differences between electrophoretically separated protein fractions in fluid from apical periodontal, follicular and residual cysts could be established. A statistically significant negative correlation between γ-globulins and other protein fractions in apical periodontal and in follicular cyst fluid was found. With the exception of the contents of the solitary bone cyst which may have been caused by diffusion of plasma proteins, the results indicate that fluid from non-keratinizing jaw cysts was primarily an exudate, with subsequent admixture of nitrogenous substances other than proteins. Locally produced immuno-globulins may contribute to the high γ-globulin content of many cyst fluids.     

Immunohistochemical study of neuronal markers in human gingiva with phenytoin-induced overgrowth

Abstract – The immunohistochemical occurrence of several different neuronal markers has been investigated in human gingiva with phenytoin-induced overgrowth. The material was compared to gingival material taken following surgical orthodontic treatment. Gingiva obtained from the phenytoin-treated groups seemed to have a reduced number of neurofilament (NF) immunoreactive nerve fibers in the propria compared to control material. In both phenytoin as well as control gingiva sparsely distributed, thin, calcitonin gene-related peptide (CGRP) and substance P (SP) immunoreactive fibers were found in the propria. No obvious differences between the two groups could be observed for CGRP and SP. Immunoreactive cells for somatostatin (SOM) with a dendritic cell shape were found in the propria in both groups, sometimes in densely packed clusters. A tendency for increase of SOM-immunoreactive cells in the phenytoin-treated gingiva was observed. A few γ-melanocyte stimulating hormone (γ-MSH)-immunoreactive cells with a round appearance were found in control as well as phenytoin-affected gingiva. In one instance, however, a heavy γ-MSH-immunoreactive cell infiltration was seen in the phenytoin sample. No immunoreactivity in either the phenytoin-treated group or in the control group was seen for proctolin or galanin. The results indicated that gingiva with phenytoin-induced overgrowth has a reduced innervation density revealed with NF immunohistochemistry.     

γ2 phase in conventional dental amalgams — discrete clumps or continuous network? A review

A bstract — Six different types of sources of evidence are examined to study the controversy of whether the γ ₂ phase in conventional dental amalgams occurs in discrete clumps or as a continuous network.
Evidence obtained from corrosion studies, volume-fraction analysis studies and amalgam microstructure studies and evidence associated with the alloy type, the structure of the γ ₂ phase and manipulative techniques are investigated.
Although, under certain conditions, the γ ₂ phase may form a continuous network there is evidence to indicate that, using a conventional Ag₃Sn-based alloy and techniques providing adequate mercury removal, the γ ₂ phase occurs in discrete clumps.