Strictly speaking, there's no-one in the UK alive today that's been given pure nitrous oxide as a dental induction agent.
Pure nitrous oxide drives out oxygen from the body, leading to a condition called hypoxia, which can be fatal. To prevent this happening, nitrous oxide has been mixed with oxygen for anaesthesia since the late 19th century. The mixture is usually 50% nitrous oxide and 50% oxygen and in essence, the mixture is the same as Entonox which is provided for women during childbirth. A specialised piece of equipment known as the Walton Apparatus to deliver the gaseous mixture was in service with dentists' until the mid 1970's - I remember the horrible contraption in the school dental clinic myself.
In the mid 1950's, two other gases were introduced for induction of anaesthesia. These were halothane and a related gas called methohexitone. They were quickly adopted by dentists' as they were found not to cause hypoxia and recovery was more rapid. Methoxexitone ceased to be manufactured in 1998, but halothane remained popular until the mid 1990's. Two other gases called isoflurane and enflurane have also been used for dental induction when combined with oxygen and presently, a popular gas is sevoflurane.
In some countries, xenon, cycloproprane, trichloroethylene and ethyl chloride have been used with varying success for this purpose.
I would add that there were always some die-hard dentists around that failed to move with the times in the 1950's, 1960's and 1970's and stuck to using the nitrous oxide/oxygen mixture. Personally, I've got a vivid recollection of my parent's dentist, who had his "surgery" in the front room of his house, disappearing in and out of the room countless times for a tot of whisky whilst giving my mother the nitrous oxide. Those were the days!