Toddler teeth grinding at night only & frequent, upset night wakings

Wondering if anyone else’s child has experienced this?

Our toddler has never been a “good sleeper” and has always woken through the night but lately is waking more frequently and is crying when waking. When he is sleeping he is <b>grinding his teeth pretty bad !! <\b>

What is going on? Does anyone have answers from if their toddler experienced this?