Comparison Between Lingual and Labial Orthodontics Based on Treatment of Overbite by Using Rocking Chair Archwire-a Biomechanic.pdf

1、Introduction– Lingual orthodontics (LiO) has developed rapidly in recent years; however research on treatment of overbite by using Rocking chair arch wire (RCA) of different curve depths in both lingual and labial orthod

2、ontics is still limited, especially studies with 3- dimensional (3D) Finite element (FE) models. The main objectives of this study is to compare the biomechanical differences i.e. stress-strain, displacement of maxillary

3、 anterior teeth between lingual and labial orthodontics and additionally observe the lingual mechanics on different inclinations of teeth.
　　Materials and Methods- The force produced by various Nickel- Titanium (NITI)

4、, Stainless Steel (SS) standard and mushroom shaped arch shaped RCA of curve depth 2,4,6 mm was measured using Electromechanical Universal Testing Machine. A 3 dimensional (3D) Finite element model (FEM) of the maxilla a

5、nd the maxillary teeth was made with nodes and elements. 12 FE models were constructed and divided into 4 groups according to NITI and SS wire of 0.016x0.022 inch standard and mushroom arch shaped RCA of curve depth 2, 4

6、, 6 mm. Additional 9 FE models were constructed and divided into 3 groups based on Retroclination(-5degree,-10 degree) and Proclination（5degree). The study of distribution of the stress- strain on the tooth, PDL, bone; t

7、he vertical displacement of the maxillary anterior tooth were analyzed and compared between lingual and labial orthodontics.
　　Results–Use of Rocking chair arch wire (RCA) of different curve depths produces more stres

8、s- strain, displacement of tooth in lingual mechanics than in labial mechanics. . Also, stress-strain, displacement increased with increasing RCA curve depth. In LiO, intrusion of normally inclined or proclined teeth are

9、 accompanied by little or no labial tipping whereas that of retroclined teeth is accompanied by further lingual tipping.
　　Conclusion – Lingual appliance is a viable option if the magnitude and direction of required a

10、mount of force are carefully applied. In the intrusion using Lingual RCA, to avoid the traumatic force to teeth, the curve depth should be lesser than Labial RCA or apply more elastic arch materia l e.g. NITI or β- Ti (B