My dd has tried this a couple of times. I believe it was at 13 months and again at 15 months, and then at 18 months. It's not easy to deal with, but if you deal with it right away when it happens, they get back on track.
If my dd did it during the night, I would keep putting her back and stand over the crib if I had to to make sure she laid down and went to sleep. I wouldn't give up until she went to sleep, because if I did, I'm looking at losing a lot more sleep in the future if she develops that habit! Also I was careful not to talk to her and to avoid eye contact and just be like a robot putting her down. Of course I did check her diaper! A couple of times she woke up with poopy pants and that's why she couldn't sleep.
I should also mention that while sometimes there is no apparent reason, sometimes the odd waking is because of a change in the household. In my case, the first two times it was nothing I could discern, but in the last case, there were a lot of house visitors who were causing disturbances in her sleep.
Teething can definitely cause unusual sleep patterns, but if you encourage her to get back on track, she should go back to the usual schedule within a week or so. In other words, don't let it be an excuse to lose good habits!
During the day, the main problem we have been having is she climbs out of the crib now. But even this can be overcome with the force of good habits. I make sure she sleeps by standing over the crib if she repeatedly climbs out. I don't reward it. I make sure she knows I'm going to enforce nap time and nighttime sleep. She stopped trying to pull this after a few days, but those few days were quite chaotic. Now she knows I mean business and she goes to sleep just fine. It also helps to do a lot of good energetic activities when she is awake, too, such as playing outside or playing with other kids.
It's interesting that we've also been having a little testing behavior regarding her climbing on tables lately. I've been using a one minute time-out for that. She has to be in her playpen with no toys and not climb out. We use a timer also. I wonder if maybe your 19 month old is doing the same thing and testing the limits a little. She may be trying to find out if you mean what you say, and how you'll deal with it when she wants to do something different than you want.
It's tough, but I guess this is the age where enforcement begins. I had two little sisters so I remember this distinctly. What I never realized before is just how tiring being consistent is. I now understand why my parents would get angry and yell! They were tired, poor things!
