Bodily labializing lateral incisors: 3D analysis using finite element method

Among all tooth types and movements, bodily labializing the upper lateral incisors is a challenging one. The main goal of this study is to introduce and analyze a method to labialize palatally erupted lateral incisors.

Five three dimensional finite element models were designed in SolidWorks 2010 of a segment of maxilla containing the upper left anterior teeth (with the lateral incisor in palatal position), their brackets, their PDLs, the spongy and cortical bone. A segment of 0.016 wire passing through the central incisor and canine brackets (bypassing the lateral incisor bracket) and a designed hook in the lateral incisor bracket (which comprises an inventory approach/design to treat a palatally erupted tooth). The hook and vertical bypassed segment height were 8, 10, 11.5 (stage 1), 9.5 (stage 2) and 9.45 mm (stage 3). Two equal forces (0.15 N each) were applied. Tooth displacements were recorded.

A hook length of 8 mm resulted in a tipping movement (apical = -7.78 × 10(-5) mm; incisal = 3.8 × 10(4) mm). The other two caused root movement. Stage 2 (hook = 9.5 mm) resulted in root movement (-1.4 × 10(-4) mm in incisal; 1.58 × 10(4) mm in apical area). Hook length = 9.45 produced bodily movement (incisal = 7.1 × 10(5) mm; apical = 6.9 × 10(5) mm).

A definite length of the hook was shown to produce bodily movement. This definite length of hook in combination with the same length of bypassed wire can be applied to produce bodily movement of the lateral incisor. An intrusive component can also be added.