title: The effect of using layered specimens for determination of the compressive strength of glass-ionomer cements.
abstract: Compressive strength is widely used as the criterion of strength of glass-ionomer dental cements, despite the difficulties in interpretation of the findings. With the introduction of light-cured glass-ionomer cements, which can be used only in thin layers, the question arises of how test specimens should be prepared for the measurement of compressive strength. A suggested method has been to prepare test pieces by building them up in layers, an approach which is examined critically in the current paper. Two different conventional (acid-base) glass-ionomers were studied with the use of layered and unlayered specimens of dimensions 6 mm (height) x 4 mm (diameter) and 12 mm (height) x 6 mm (diameter). While smaller samples gave the same value of compressive strength as larger specimens, layered specimens gave significantly lower values of compressive strength for both sizes. In view of these findings, and since the layered specimens are tedious to prepare, we conclude that compressive strength is unsatisfactory as a criterion of strength for light-cured glass-ionomer cements.
authors.affiliation: Materials Technology Group, Laboratory of the Government Chemist, Teddington, Middlesex, United Kingdom.
authors.forename: H M
authors.initials: HM
authors.lastname: Anstice
authors.forename: J W
authors.initials: JW
authors.lastname: Nicholson
authors.forename: J F
authors.initials: JF
authors.lastname: McCabe
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D003799:Dental Stress Analysis; D004548:Elasticity; D005899:Glass Ionomer Cements / Q000138:chemical synthesis / Q000737:chemistry*; D008422:Materials Testing; D011208:Powders; D011336:Probability; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D000180:Acrylic Resins; D000538:Aluminum Silicates; D005899:Glass Ionomer Cements; D011208:Powders; C006903:carbopol 940