The mean setting time of MTA is:: (A) 135 ± 5 min, (B) 145 ± 5 min, (C) 155 ± 5 min, (D) 165 ± 5 min
Answer is D. The setting time for MTA is lengthy, about 165 minutes for the initial set and less than 6 hours for the final set, which is a major drawback of using this cement.
Phillip's science of dental material 12th edition page 332