Possible Clues:

• Some pearls, perhaps, available for really desirable swap?
• Exchange for something very valuable
• Canines watch over force
• Do they look better after a brushing?
• Canines from particular force accompanying detective
• Valuable things to give?
• Does one need these to see what one is eating?
• Can such canines see to bite?
• Canines in upper jaw, under the optics
• Sounds like it's impossible for the dog to bite his lips with these