Four upper front teeth are missing. Would it possible to have four distinct implants?

Yes, it is possible to place 4 individual implants in the front to replace 4 teeth. But it is usually not necessary to do that. Doing two implants and a bridge works very well for most patients.

one most important fact about implant is its width and not number of implants so for eg. if possible to place 4 implants with thin diameter, thn better to go with thick implants with less numbers.

It sounds as if you could have 4 narrow body implants with abutments and crowns placed.  Do you have an x ray you could post.  If it is not possible to place 4 implants, you could have 2 implants placed and a 4-unit bridge could be placed.

When you treatment plan the number of implants to fill a certain space you must always keep in mind that each implant needs to be 3 mm away from any other implant and at least 1-1.5mm away from any tooth.
Therefore if you have 4 implants (2 with 3mm diameter and 2 with 4 mm diameter) and the appropriate spacing between these implants your total space will exactly be 27mm therefore it is possible. 
However, study's will show that when you have two implants next to each other it is more difficult to mainatain the papilla or pink triangle that is in between the teeth. Often times a "black triangle" or space appears between these teeth and the results are not ideal.
As a result, a situation where a patient is missing their front four teeth is often treatment planned to have 2 implants and a bridge not just for reduction in costs but to increase in "pink esthetics"
This does not mean that 4 implants cannot be placed (as there is room although it is very tight). I would recommend seeing an implant specialist who understands both the restorative and surgical aspects to get the best results.
Try searching AAID and ABOI for best results.

Hi:It is very likely that you can have four possibly narrow implants in the space you have described.  I would like to see a photo of the missing teeth to give you more accurate advice.Best,Dr. Maddahi

Hello,
Dental implants come in different lengths and diameters. if there is enough bone it is ideal to place 1 implant per missing tooth, however sometimes due to bone quality, limited space or budgeting you can place fewer implants and connect with a bridge.
Dr. Mazaheri

yes you can place 4 dental implants in that area and yes you can certainly replace individually the 4 teeth, now the situation is that this will depend a lot on the amount of bone, width and height.if this is good, yes we can get that solution of 4 dental implants.

There are a large number of factors, both aesthetically and anatomically that have to be taken into account to answer your questions. While theoretically it is possible to replace missing teeth with individual implants it is not always the best solution or the possible solution for your situation,
Being your anterior front teeth they are obviously front and centre when you talk and smile. It is one of the most challenging areas to provide aesthetically acceptable and functional Implants that are not going to cause issues a few years down the road. 
I would highly recommend that you have a proper diagnostic work up that will include a CBCT (cone beam computer tomography ) and study models to determine the amount of bone you have remaining in the front area (3D anatomy of remaining bone) and correct positioning of the implants. If aesthetics are a concern for you then an aesthetic analysis is also important to identify challenges the may be to treatment. As important as the bone is to Implant treatment the soft tissue (gums) around the implants in the front of your mouth are equally important.
Sometimes you can get a better looking result with two implants and have the two other teeth bridged onto those implants. It all depends on your specific situation. 
If you are going to commit to such a treatment you deserve to get the best possible , long term, treatment. That is going to require proper diagnostic records and understanding the benefits and risks associated with such treatment. 
Dr. Paul Newitt D.M.D. A.F. AAID