Introducing Teddy to next door's puppy

Teddy is 19 months and there has been a recent arrival next door in the form of a bichon frise puppy. I look in on puppy during the day and now she is about 4 months old I have been trying to introduce the two of them. My heart is in my mouth though as there is a big difference in size and although their tails are wagging I think Teddy is too rough with the little one. She sometimes tries to hide under a chair but most times she goes after him even when I think things are getting out of hand. I keep the meeting to about 10 minutes or so for the time being. They do seem to miss each other at times and I have seen Teddy and Lola on either side of the fence crying to get together. Anyone got any tips? I would love them to be friends but want to the introductions properly. Any advice welcome.