However, no arrests have been made so far, police said.
The cases were registered for cheating and endangering lives (of patients), they said.
The complainant Dr P Saravanan of Saravana hospital, the dealer - Ramasubbu of Tiruppalai, his sons, Amar Karthik and Sundareswaran, and their employee, Raja, had supplied stents to him in May. The expiry date in the delivery challan had been covered up. The difference in the expiry dates in the challans and stent packet came to light during auditing.
Meanwhile the dealer alleged that the doctor was trying to pin the blame on them for the 'failure' of angioplasty cases performed in their hospital and said he was prepared to face the case legally.
Police had also registered a case against Dr Saravanan and his staff on Amar karthik's son complaint that he (and others) had trespassed into their house and threatened them.