S O Hondrum1. 1. US Army Dental Laboratory, Fort Gordon, Ga 30905-5661, USA. SHondrum@aol.com
Abstract
STATEMENT OF PROBLEM: Mechanical properties are considered to be important to the clinical success of dental cements. Storage time of dental luting agents (dental cements) before use and at the manufacturer may have substantial effects on their properties. PURPOSE: This study observed and investigated the changes in the properties of water-based dental luting agents over time and on exposure to various environmental conditions. METHODS AND MATERIAL: Properties of zinc phosphate, zinc polycarboxylate, and glass-ionomer luting agents were recorded at baseline and at intervals past 84 months, whereas the materials were exposed to controlled storage conditions as well as various conditions typical of clinical situations. Tests included viscosity, diametral tensile strength, ultimate compressive strength, rigidity, hardness, and working/setting times. RESULTS: Viscosity increased over 24 to 60 months for the acidic polymer liquids (zinc polycarboxylate and glass ionomer). Tensile and compressive strengths began to decrease after 36 months for all cements, most acutely for glass ionomer. CONCLUSION: Changes in critical properties on aging may not be noticed by the clinician and yet may impact clinical success. These data emphasize the importance of storage stability for perishable dental materials and portend the need for standardized tests.
STATEMENT OF PROBLEM: Mechanical properties are considered to be important to the clinical success of dental cements. Storage time of dental luting agents (dental cements) before use and at the manufacturer may have substantial effects on their properties. PURPOSE: This study observed and investigated the changes in the properties of water-based dental luting agents over time and on exposure to various environmental conditions. METHODS AND MATERIAL: Properties of zinc phosphate, zinc polycarboxylate, and glass-ionomer luting agents were recorded at baseline and at intervals past 84 months, whereas the materials were exposed to controlled storage conditions as well as various conditions typical of clinical situations. Tests included viscosity, diametral tensile strength, ultimate compressive strength, rigidity, hardness, and working/setting times. RESULTS: Viscosity increased over 24 to 60 months for the acidic polymer liquids (zinc polycarboxylate and glass ionomer). Tensile and compressive strengths began to decrease after 36 months for all cements, most acutely for glass ionomer. CONCLUSION: Changes in critical properties on aging may not be noticed by the clinician and yet may impact clinical success. These data emphasize the importance of storage stability for perishable dental materials and portend the need for standardized tests.