If you cannot wear braces and want quick results then go for cosmetic dentistry in which various options are available depending on the gap type. If the gap is less then it can be built with composite filling which is quite cheap and can be done only in one sitting but if gap is more then you have to go for either veneers or crowns which are costlier than composites and take aroudn 2-3 visits. For more info on cosmetic dentistry you can read this article... http://www.identalhub.com/dental-dealing-with-a-gap-tooth-566.aspx