تقييم ثبات النهاية الانسية للتجعيدة الحنكية الثالثة كنقطة مرجعية في حالات القلع وامكانية استخدامها على الفك السفلي

Background & Objective: Cephalometric superimpositions are the most commonly means used to assess the orthodontic teeth movement – especially- in cases of extraction - with their attendant risks and difficulty, therefore dental casts were an alternative way for serial assessment. So the aim was to evaluate the stability of the medial end of the third palatal ruga as a landmark in maxilla in extraction cases, and the possibility of using it in the mandible. Material& method: The sample consisted of 120 dental casts and 120 lateral cephalometric of 40 patients ( pretreatment ,after leveling ,and after retraction) from the department of orthodontic,faculty of dentistry, Damascus University ,who received orthodontic treatment involved extraction of first premolars (17 bimaxprotrosion , 23 class II div1) .The mean age was 20.8 years . Three variables were measured on the cephalometric and dental cast of both jaws (distance of retraction, anchorage loss after leveling, and after retraction ). T-Student analysis was used. Results: there were no statistically significant differences between the mean distance of retraction(1.08±2.44 ،0.83±2.88mm) in mandible and maxilla, in sequence , and mean anchorage loss after leveling(0.36±1.44 ،57.±1.18) and after retraction (0.38±1.41 ،0.55±1.74)mm in both jaws Conclusion: The medial end of the third palatal ruga appears to be stable anatomic landmark in maxilla for construction stable reference plane , and we can rely on the vertical project of this plane to the lower cast as a stable reference plane in mandible, in patients who have bi-maxprotrosion or class II div1