Very interesting stuff is said in this video:
My dentist says to avoid offices that have their crowns, etc. fabricated in China. Says that some Chinese labs will substitute base metals for gold, causing issues with the crown or implant.
In this piece, Dr. Mark Burhenne says the following:
Quality matters here. Some dentists will charge less ($600-800) but get crowns from labs overseas from places like the Philippines. Unfortunately, this often results in contaminated products. Many of these factories also use generic materials rather than brand-name ones that have consistent results over years.