E.C. Combe

Studies on polycarboxylates and related cements

Abstract Ten polycarboxylate cement powders have been analysed for their major constituents and have been classified into four main categories. Zinc oxide appears to be the principal component of all the powders. Some contain magnesium oxide up to about 10 per cent. One material contains alumina, and three of the powders contain polyacrylic acid.

The Use of Additives to Improve the Mechanical Properties of Gypsum Products

The effects of adding a combination of calcium oxide and gum arabic additives to calcium sulfate hemihydrate have been determined. It has been found possible to produce gypsum products with properties superior for dental applications. In particular, formulations are suggested for die, model, and flasking materials.

Further studies on radio-opaque denture-base materials☆

Abstract The effects of the addition of a number of radio-opaque inorganic salts to poly(methyl methacrylate) have been investigated. Of the additives tested, barium fluoride appears to be the additive of choice; it can be incorporated into acrylic to form a denture-base material which meets specification requirements, and which is aesthetically superior to commercial products containing barium sulphate.

Factors affecting the adhesion of polycar☐ylate cement to enamel and dentin

The adhesive bond strength of polycarboxylate cement with enamel and dentin and the factors affecting the adhesion of the cement to both structure were studied. A thick cement film reduced the tensile and shear bond strengths of the cement. Although surface roughness reduced the tensile bond strength of the cement, it significantly increased the shear bond strength. The application of the cement under pressure increased its shear bond strength. Surface treatment with 4% sodium fluoride solution for 5 minutes, 4% stannous fluoride solution for 2 minutes, and a 10% suspension of calcium hydroxide for 5 minutes significantly increased the shear bond strength of the cement with dentin.

Dental materials: 1982 literature review Part 1

Objectives: Leptin is a hormone-like protein produced by the adipose tissue. It plays an important role in protection of host against inflammation and infection. Some studies have reported changes in leptin levels in the gingival crevicular fluid (GCF), saliva and blood serum of patients with periodontal disease compared to healthy individuals. The aim of the present study was to compare the salivary leptin levels in patients with advanced periodontitis and healthy individuals. Materials and Methods: In this case-control study, the salivary samples of healthy individuals and patients with advanced periodontitis with clinical attachment loss >5mm were obtained using a standardized method and the leptin levels were measured in the salivary samples by means of ELISA. The effects of the periodontal status and sex on the salivary leptin levels of both groups were statistically analyzed by two-way ANOVA. Results: The means ± standard deviation (SD) of salivary leptin levels in healthy subjects and patients with advanced periodontitis were 34.27±6.88 and 17.87±5.89 pg/mL, respectively. Statistical analysis showed that the effect of sex on the salivary leptin levels was not significant (P=0.91), while the effect of advanced periodontitis on the salivary leptin levels was significant compared to healthy individuals (P<0.0001). Conclusions: In patients with advanced periodontitis, the salivary leptin levels were significantly lower compared to healthy individuals. Thus, assessment of salivary leptin can be done as a non-invasive and simple method to determine the susceptibility of patients to advanced periodontitis.This report, which is to be presented in two parts, reviews published papers on dental materials, based on literature for 1982. In this part the following topics are considered: metals, including dental amalgam and casting and wrought alloys; ceramics, implants and aspects of dental biomechanics.

Hardening of model and die materials by an epoxy resin

By use of epoxy resin impregnation, it has been found possible to improve the mechanical properties of gypsum-based model and die materials.

Dental materials: 1992 literature review

This review of the published literature on Dental Materials during 1992 has been compiled by the members of the Dental Materials Panel of the United Kingdom. Please note that the views expressed in this review are those of the individual authors and not of the Dental Materials Panel. The contribution of each author has been clearly identified with each topic. Therefore, if there is anything in the review you disagree with or dislike, or possibly even like, then put pen to paper and write to the editor, who will be happy to pass these comments to the appropriate contributor for reply. Both the original letter and the author’s response will be published together in a later issue of the Journal, but only if the views expressed add to the scientific argument. As this will be my last review as editor I would like to thank all the contributors, as without their cooperation

Reaction of the exposed pulps to new cements containing calcium hydroxide

The biologic properties of three newly developed cements containing calcium hydroxide were evaluated and compared with those of polycarboxylate cement and Dycal by application of the cements in direct contact with rat pulps. The newly developed cements were biologically acceptable and induced pulpal healing by formation of secondary dentin. Dycal elicited mild pulp inflammation, followed by slow dentin formation. Although polycarboxylate cement induced a very mild pulpal reaction, healing took place via the formation of thin irregular, poorly formed dentin bridges over a long period.

Studies on polycarboxylates and related cements 4. Properties of cements

Abstract The mechanical properties, setting times, apparent pH of setting cements, solubility, film thickness and adhesion to enamel and dentine have been determined for a range of zinc polycarboxylate cements. The properties are discussed in relation to the suitability of the cements as linings and luting agents. The effect of composition on properties is also discussed.

A comparison of some polymercontaining die materials

Abstract The properties of three polymer-containing composite die materials have been determined and compared with those of a die stone. Apart from contraction during setting, the polymer-containing products appear to be similar in properties to the gypsum product, though better in terms of abrasion resistance.