3M acquired Unitek Corp. from Bristol-Myers.

Minnesota Mining & Manufacturing Co. did not disclose terms of the transaction, which it termed one of the biggest acquisitions in its history. The Monrovia-based company is a supplier of orthodontic appliances. The purchase will increase the medical products operations of 3M. Unitek’s main products are braces and other orthodontic appliances. It has about 1,200 U.S. employees and was acquired by Bristol-Myers in 1978.