What are the cons of extraction of last upper molar compared with root canal and crowning crown ?

Tooth migration: The root canal and crown are the way to go! losing the molar will long term cause the lower molar that opposes the extracted tooth to extrude or over-erupt, causing your bite to be off. Also, always save a good tooth so that your dentition remains complete for proper chewing!

Risk losing more : Generally, when a molar tooth is removed, the risk of losing adjacent and functioning teeth increase. Teeth need each other to prevent them from shifting and drifting. Once that occurs, bone loss accelerates and increased mobility increases the probability of further tooth loss. Much better choice to save the molar with root canal and crown.

One tooth less : Apart from having one less tooth to chew with, the lower molar may supra erupt and interfere with the rest during chewing cycles or during sleep.

Tooth: Is the tooth in function, meaning does it have a tooth on the bottom to bite against? If so, does your dentist think you will get more than 5 yrs out of RCT and Crown, if not may be better to extract and place an implant, especially as you are a young guy..

Tooth extraction: will remove a tooth from your mouth leaving a gap that could reduce the functionality of your bite and can impair the cosmetic appearance of your face. Alsocomplications may occur during or after tooth extraction is done.

Depends which molar: If the "last upper molar" is a wisdom tooth, it can be tough to do a good root canal and crown lengthen. Any extraction can have a complication (usu dry socket). It's usually good to try to save the tooth and only extract as a last resort. If you have the money, try saving it especially if it is a first molar