Buying Dental insurance on your own is very challenging to find real value. Dental "insurance" is not really insurance to begin with as it has yearly maximums that can be as little as $400 and usually maxes out at $1000-1400. These policies often have many restrictions that insure you from not getting your desired coverage as well.
Interesting to note that the first policies were in 1968 and paid an average of $1000 per year --you could buy a new car in 1968 for less than $2000!
If you are on your own -look for pre tax dollars to pay for your dental care with FSA's or medical savings plans.
Otherwise just find a way to make payments and get it in your budget just like any other major purchase--Good Luck!