My DD (11 months) has always been a super happy, smiley, content little bubba with the exception of when she's teething.
She has her 8 incisors already. Her sleep regressed (from sleeping through the night) each time she was cutting a new tooth.
No her first molars are coming through and she's really struggling. She was up most of last night and howled for at least 2 hours when I took her out today (which she would absolutely never normally do - she normally loves being out and about). It was a combination of being tired and pain preventing her from napping.
I give her calpol and use teething gels but she has definitely inherited my low pain threshold!
Please share and let me know what helped your little ones when their molars were coming through!