Siakam crossed over and went baseline, leaving Bucks defender Ersan Ilyasova behind him. The Raptors forward continued his drive to the hoop and threw down a huge dunk in the face of Lopez.
Siakam's thunderous jam was part of a nine-point first quarter for the forward. He helped the Raptors grab an early 11-point lead in the first frame.
The Raptors held an 83-76 lead after the third quarter. Siakam had 14 points (6-of-17 shooting), five rebounds and an assist in 30 minutes.
Giannis Antetokounmpo led the Bucks with 21 points and 11 boards entering the fourth quarter. Lopez had 16 points (7-of-14 shooting), seven rebounds and two assists.