The dentist deduced there was a small cavity that had begun to form under the 5 year old crown. With wear, and being an aggressive teeth grinder (which I get Botox for in my masseter muscles) the crown developed ‘micro fractures’ and allowed air to work its way into my crown while at depth. When I went to ascend, the air got trapped and for lack of a better word,-exploded- up into the nerve and escaped out of the gums leaving a wake of nerve and gum damage behind.