Which of the following factors could lead to moisture contamination during a restoration?

Moisture contamination during a dental restoration is significantly influenced by salivary flow. When a patient has excessive salivary flow, it can interfere with the bonding and setting of dental materials, leading to compromised restorations. An effective seal is critical for restorative materials to bond properly; moisture can disrupt this seal, leading to microleakage and potential failure of the restoration.

While factors like improper storage of materials and inadequate patient management can contribute to other issues in the dental practice, they don't directly cause moisture contamination in the same way that salivary flow does. Effective management of salivary flow is essential during procedures to maintain a dry field, which is key to ensuring the successful placement of restoratives.