Nataliya Donskaya, DDS

Although a 3D Scan is the ideal way. As mentioned by Dr. Dushyanth, an experienced oral surgeon can determine bone width without it. Getting a 2nd opinion is also recommended. 

That is not necessarily true about the temporary crown being a mold of the old tooth. There is a possibility that your dentist did not have the correct shade for the temporary crown. Keep in mind temporary crowns are prefabricated and permanent are custom made. I'm sure your permanent one will look amazing. 

Excessive preparation may expose regions of tooth dentin, which is the hard tooth tissue under enamel. Resin would help the over prepped tooth but it all depends on how close the dentist got to the root of the tooth.

After root canal therapy, the tooth no longer has a root and is dead. It is recommended to have crowns placed on RCT teeth for extra protection since it loses structure, and also for cosmetic purposes. 

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If you don’t have enough bone, the bone can be rebuilt. It may be possible to have a bone graft placed to create a better structure for a new implant. Do keep in mind that there are other predictors for implant success and failure which are generally divided into patient-related factors (e.g., general patient health status, smoking habits, oral hygiene maintenance, etc). 

Based on my experience, darkening around a porcelain crown is  more likely to be present whenever metal is used as a substructure for the crown ( PFM or porcelain fused to metal / gold crowns).   PFM crowns have an opaque “non-precious metal” , “semi-precious metal” or “high noble metal” alloy substructure that seals the tooth and offers  support for the tooth colored ceramic that is stacked on top.  Low gold content metal is a dark gray and is easily seen if not covered over.  Even 14 carat gold alloys have a gray color.  PFM crowns can be made beautifully by a skilled dentist-technician team but this type of crown is much harder to make attractive long term than all porcelain crowns or veneers.  Metal is used to give the crown strength.  PFM crowns are also used by dentists that have not been trained on the newer bonding procedures necessary for the all porcelain restorations.  Black areas at the gum-line can also be present if the border or margin of the crown is exposed and there is a difference in brightness between the restoration and the root.  All porcelain crowns made with high translucency material, do not have any metal and  can be the most aesthetically pleasing of all of the different types of dental crowns.

It is possible that the crown was not properly cemented or may have an air bubble. My recommendation is to go see a dentist before the situation gets worst or you end up losing the crown. 

Yes, you can get immediate dentures after extraction. The process of an immediate denture will require several adjustments; you should keep in mind that this means that you will have to come back to your dentist's office for this adjustments. After six months, as soon as the healing process is complete a reline will be done to compensate for the shrinking of the gum and to assure that the denture has the right fit.

There are several treatments available such as fillings crown and veneers, but you teeth have to be evaluated closer to determine if root canal treatment will be required prior to restoration. X-rays have to be taken to determine how deep the cavities are and if root canal is really necessary. You should visit a dentist as soon as possible to prevent fracture or infection development.  

It definitely looks like the area is infected. Bone loss is not a good sign. Most likely the implant will have to be removed and the area cleaned. It is ideal to have a 3D scan taken to have a more accurate diagnosis of bone loss. Then have the bone graft placed again and let the area heal to make sure the infection is gone. After that a new implant can be placed. Getting a second opinion is always a good idea.