Final answer:
The one invalid reason for a dental hygienist to have knowledge of dental materials is the creation of these materials. However, they need to understand materials for proper care, patient recommendations, and handling toxicity concerns, for example mercury in dental amalgams.
Step-by-step explanation:
Understanding dental materials is crucial for dental hygienists for several reasons, but not all reasons are valid for their need for this knowledge. One reason that is not a valid reason for a dental hygienist to have knowledge and understanding of dental materials is the creation of these materials, as this typically falls under the purview of dental material manufacturers and researchers rather than dental hygienists. However, dental hygienists do need to understand dental materials to ensure proper care of dental apparatus, to make appropriate recommendations to patients, and to handle concerns about the toxicity of materials such as the mercury found in dental amalgams. Due to concerns over mercury toxicity, the choice of dental fillings and understanding the composition, manipulation, and safety of various materials used in the clinic are all important aspects of a dental hygienist's role.