There are two stages of parenting that seem to bring the most angst: potty training, and teething. They're the worst! And they're the two stages that you really can't avoid. Obviously, you don't want to send your kid to school in a diaper or pull-up. And those teeth are going to come in regardless of what you do. When it comes to teething, it can be a real struggle, for kids and parents. There's not a whole lot you can do to make the process easier (even medicines don't seen to work very well!), and it lasts from roughly 4-5 months of age until your kids are well into toddlerhood.
While you may be able to provide some relief to teething infants, teething toddlers is a horse of a different color. At this age, they're trying to add some pretty major teeth to their mouths. If you've ever been through teething with a toddler, then you might have wondered by it gets so much harder at night. Turns out, there's a perfectly reasonable explanation.
Once your toddlers settle down for the evening, there are fewer distractions to take their mind off the pain in their mouth. Additionally, they're obviously tired! We all know that when you're not feeling well, it's always worse at night. So it's no wonder that toddler teething seems worse at night.
During the day, toddlers are go, go, go! Even if you don't manage their teething pain with medication, it's fairly easy to distract them with other activities (or snacks). There are actually studies that suggest that kids are less likely to perceive pain when they're distracted. It just hurts more when you're tired and there's nothing to catch your attention, and this applies regardless of age.
If you're dealing with a teething toddler, you have our sympathies. There's not much to be done to make the discomfort and pain better during this phase. You can try Motrin or Tylenol, and lots of parents have found success with home remedies like amber necklaces, oils, or cold therapy (ice packs or frozen foods).
But just remember: it's not going to last forever! Those teeth will break through eventually. And then you'll be dealing with other reasons for why your toddler won't sleep through the night.