Monoplane Non-anatomic teeth are also known as flat plane teeth, 0 degree teeth, monoplane teeth or Rational posteriors. They have flat occlusal surfaces. Their mesio-distal inter-digitations are therefore not as critical as those for teeth with cuspal inclines. They are arranged to contact a flat plane, that is, the maxillary and mandibular teeth must contact each other evenly. Special care must be taken to achieve this result.