Wadid Castillo, DDS

Permanent crowns can be made from stainless steel, all metal (such as gold or another alloy), porcelain-fused-to-metal, all resin, or all ceramic.
Porcelain crowns can be color matched to your adjacent teeth (unlike the metallic crowns). However, more wearing to the opposing teeth occurs with this crown type compared with metal or resin crowns. The crown's porcelain portion can also chip or break off. Next to all-ceramic crowns, porcelain-fused-to-metal crowns look most like normal teeth. However, sometimes the metal underlying the crown's porcelain can show through as a dark line, especially at the gum line and even more so if your gums recede.

I hope it can help you!

Your case sound so weird. We have to see if your dentist took the panoramic before put the crown. I recomended you to removed the one who is causing your problem, evaluate your case and put on another ones. Maybe it weren´t insert correctly, so go to another dentist to evaluate your case. 

Dental implants may be an option for people who have lost a tooth or teeth due to periodontal disease, an injury, or some other reason.

The ideal candidate for a dental implant is in good general and oral health. Adequate bone in your jaw is needed to support the implant, and the best candidates have healthy gum tissues that are free of periodontal disease.
Dental implants are intimately connected with the gum tissues and underlying bone in the mouth. Since periodontists are the dental experts who specialize in precisely these areas, they are ideal members of your dental implant team. Not only do periodontists have experience working with other dental professionals, they also have the special knowledge, training and facilities that you need to have teeth that look and feel just like your own. Your dentist and periodontist will work together to make your dreams come true.

In the other hand, i would like to see a picture about your case. Dentis might provide you with an specific result.

I hope it can help you with yor problem.