Gray, 22, and fly-half Finn Russell, 23, were being monitored following last Saturday's 29-18 win over France.
A scan showed Gray had partially torn a pectoral muscle while Denton, 26, sustained a groin injury before last month's 36-20 defeat of Italy.
Russell was withdrawn early against France after suffering a concussion.
He is undergoing the graduated return-to-play protocol.
Scotland lock Jonny Gray and back-row forward David Denton have been ruled out of Saturday's Six Nations match against Ireland in Dublin.