Dr Wu is very enthusiastic about his CEREC, understandibly so. It is great technology. There are however a couple of minor mis-statements in his post. First, the tooth colored material these crowns are milled from is in fact a metal even though they are tooth colored. The materials used are either dilithium silicate or zirconia, both of which are metals on the periodic table. Picky, I know but true. The fit between the crown and the tooth, while very good and totally acceptable, is far greater than the gap between a conventionally cast crown and the tooth. Both gaps are filled with cement but the CEREC gap is approximately 8 times greater.