Final answer:
Low solubility in a hardened dental cement is essential for keeping a gold crown in place for a long time in the wet environment of the mouth.
Step-by-step explanation:
A hardened cement having "low" solubility can firmly hold a patient's gold crown in place for years in a wet environment. Cement solubility is a critical factor in dental applications as the material must withstand saliva and other fluids present in the oral cavity. When a dental cement has low solubility, it means it will not dissolve easily over time, which is essential to maintain the integrity of the crown and its bond to the tooth. In contrast, if the cement has high solubility, it could degrade, and the crown might become loose or fall out. Therefore, using a cement with low solubility is vital to ensure the long-term success of dental restorations like gold crowns.