I think you are confusing two different meanings of consider.

1. If you consider X Y or consider X to be Y (these expressions are equivalent), consider means "believe" or "maintain": you hold or express the opinion that X is Y.

   I consider Sartorius a fool.

2. If you consider X as Y, consider means "take under consideration" or "discuss": you discuss X as if it were Y, or engage with X in its aspect as Y.

   Until now we have been analyzing this as a practical problem; let us now consider it as a moral problem.

It is not clear in your examples which you mean; but picking one or the other will pin it down.

"is considered a " is more correct. Your sentence means the following:

"The reconstruction of object models is performed using a graph matching approach. This approach is considered a corner fixing dilemma."

I get the impression that you this is not what you are trying to say. How can an approach be a dilemma?

In University, I was taught that you can never "consider as". You always "consider something to be".

• Correct:

  I consider my dad to be the greatest man on earth.

• Incorrect:

  I consider my dad as the greatest man on earth.