Assessment of stress distribution pattern in mandibular buccal shelf area during retraction with different angulation using buccal shelf screws — A 3d finite element study

Abstract

Orthodontics in its century of existence have had a lot of landmarks in its evolution, but very few can match the clinical impact made by micro-implants and the recently introduced infra-zygomatic crest & buccal shelf orthodontic bone screws. Micro-implants and extra-radicular BS have brought about a renaissance to the field of orthodontics with its concept of absolute anchorage in the past decade. It is an added armamentarium in the hands of an experienced clinician to overcome new clinical challenges and convert even borderline surgical cases to nonsurgical without, compromising with the results achieved. Aim It is a FEM study in which buccal shelf screws are inserted in buccal bone lateral to the distal root of the 2nd molar and 4 mm buccal to the CEJ with different retraction forces and various angulation to study stress pattern in MBS area. Material and Method CBCT 3D image of the study mandible is made and the image transfer to the software. A FEM is created using a dedicated software. Orthodontic buccal shelf screws which is made of titanium alloy (diameter, 2 mm; length, 12 mm; thread ridge height, 0.2 mm; thread pitch, 0.6 mm). Miniscrew implant insertion is designated at 30°, 40°, 60°, 70°, and 90° angulations, and at each angulation a horizontal load of 150, 200, and 250 g is applied. Results BSS when inserted in buccal bone 60-70 degree angulation showed the least stress pattern in mandibular buccal shelf area and 40 – 50 degree angulation showed maximal stress distribution pattern.