It is difficult to answer this question without examining your teeth and smile.   You need to realize that you are asking your dentist to do the hardest treatment in dentistry. Let me ask you, do you want to improve the appearance of this one tooth or the appearance of your smile?  Without seeing your teeth the answer could be different depending on what you would like to achieve.  If you want to improve just the appearance of this one tooth than simply put, yes, you can treat the one tooth. However, is this the best treatment and will it have the best outcome?  What you need to understand is that this may be a simple answer but not a simple solution. To achieve an exact match and create a single restoration that blends perfectly with your other natural teeth is not a simple task.  It is due to this challenge that we often recommend treating more teeth to create the illusion of all the teeth blending naturally in the smile.  Treating more teeth may be more predictable than treating one and you may find an improvement in your smile not just one tooth.  I would recommend you discuss this with your dentist and express what you want to achieve and allow him to explain why more teeth are being recommended. Perhaps together you can reach a compromise of treating your two front teeth.                                                
Dr. Lemongello