A photoelastic study on the stress distribution of the upper anterior teeth when retract with high pull J-hook headgear

Lee, You Jin; Park, Soo Byung

Abstract

This study was designed to inveatigate the stress intensity and distribution produced by 1mm activation of retraction archwire with 0degrees, 7degrees, 14degrees torque and application of high pull J-hook headgear during retraction of four maxillary incisors using the photoelatic stress analysis. The photoelastic model was made with a PL-3 type epoxy resin which was substituted by alveolar bone portion. Each retraction archwire was fagricated from .020" x .025" stainless steel wire which had vertical loops in 7mm height and hook for high pull J-hook headgear between central and lateral incisors. The high pull J-hook headgear was applied 35 degree backward and upward to occlusal plane with 200mg per each side. The findings of study as follows : 1. In case of 0degrees torque, the stress was distributed from cervical 1/3 to apex of root of central and lateral incisors which were the froms of arc mode. When the high pull J-hook headgear was applied, the stress disrtrbuted by following by arc mode was presented from cervical 1/2 to apex of roots of central and lateral incisors. And the stress distributed by following the root surface was presented from alveolar crest to cervical 1/2 of central and lateral incisors. The stress between apecies of central and lateral incisors was presented also. 2. In case of 7degrees torque, the stress distributed by arc mode was presented from cervical 1/2 to apex of roots of central and lateral incisors. And the stress distributed by following the root surface was presented from alveolar crest to cervical 1/2 of roots of central and lateral incisors. When the hight pull J-hook headgear was applied, the stress distributed by following the root surface was presented more apically than without headgear. The stress between apecies of central and lateral incisors was presented also. 3. In case of 14degrees torque, the stress distributed by following the root surface was presented from alveolar crest to apex of roots of central and lateral incisors. When the high pull J-hook headgear was applied, the stress distributed by following the root surface was presented stronger than without headgear. The stress between apecies of central and lateral incisors was presented also.