Thanks for your response!!
It is true that temporary crowns do not have a long life. The life is usually ranging from 2 weeks to 2 months.Temporary crowns tend to fracture when placed over the long span bridges.They also wear easily.They tend to have marginal leakage.They have inadequate bonding to the tooth structure. Moreover, the material used is usually porous and absorb the oral fluid which lead to bad odour.It also has a poor tissue response which could result in tissue irritation.So, it is important to remove the temporary crown.
Once the permanent crown is fabricated in the lab, it is not possible manipulate it.However, it could be adjusted to remove high points ( trimming of occlusal surface in case you feel the bite is high or the vertical length of the crown is more leading to inability to close the teeth properly ).It is the least possibility for a dentist with such an experience to take improper impressions. Failure of fixed prosthesis could be due to many reasons such as improper / insufficient tooth reduction, improper preparation of the gingival margin, undercuts, improper flaring, failure to include certain features like radial shoulders, bevels, chamfer finish etc which helps in periodontal preparation, structural durability and marginal integrity of the crown.
As mentioned above, once permanent crown is fabricated in lab, it cannot be manipulated to great extent. I would advise you that if you doubt the outcome of the treatment, it is better not to invest further. I would suggest you to visit a ' Prosthodontist ' who specializes in preparation of prosthesis.
Any Further Questions, Revert and i would be glad to Answer.
Bonuses would be Appreciated.