The Wellington Dental School Clinic, Willis Street, circa 1940s or 1950s.
The only reason this young lad could be smiling is the nurse just gave him a blast of the old laughing gas or she just gave him a clean bill of health.
And it wouldn't hurt you to obtain a mouth guard to protect your teeth if you are going to play contact sports or engage in extreme sports like walking through the centre of town in the wee hours on a Sunday morning...