Porcelain leaks some aluminum, and most composite fillings will leak some BPA, but these are much less dangerous than mercury. There is no perfect filling material. I have a mixture of porcelain inlays and onlays and composites. The larger fillings are inlays or onlays, and the smaller ones composites. It is not a good idea to use composites for large cavitities, especially if they are on the biting surfaces of rear teeth.