Fig. 3

Minimum and maximum principal stress distribution on aligners and PDL in mandibular advancement with AMS. Compressive and tensile stress was distributed on the aligners. The closer to the button, the greater the stress. Compared with the stress on the aligners, lower stress acted on PDL. A In the upper dentition, compressive stress mainly acted on the aligner distal to the button. In PDL of anterior(posterior) teeth, slight compressive stress was on the apical 1/2 on the labial(mesial) side and cervical 1/2 on the palatal(distal) side. B In the lower dentition, compressive stress mainly acted on the aligner mesial to the button. In PDL of anterior(posterior) teeth, slight compressive stress was on the cervical 1/2 on the labial(mesial) side and apical 1/2 on the lingual(distal) side. C In the upper dentition, tensile stress mainly acted on the aligner mesial to the button. In PDL of anterior(posterior) teeth, slight tensile stress was on the cervical 1/2 on the labial(mesial) side and apical 1/2 on the palatal(distal) side. D In the lower dentition, tensile stress mainly acted on the aligner distal to the button. In PDL of anterior(posterior) teeth, slight tensile stress was on the apical 1/2 on the labial(mesial) side and cervical 1/2 on the lingual(distal) side