To Evaluate the Favourable Distribution Pattern of Stress in Maxilla and Mandible during Maxillary Protraction Using Miniplates of Varying Diameters and Thread Pitches under Different Levels of Inter Maxillary Forces: A Study Using Finite Element Analysis

Abstract

Introduction The aim of the study is to compare the stress distribution pattern by three different diameters of miniplate (1.5 mm, 2 mm, 2.5 mm) of three different mini- implant thread pitches (0 .5 mm, 1 mm, 1.5 mm), in the maxilla and mandible during maxillary protraction using different inter-maxillary elastic force of (2 N,4N,6N,8 N).  Materials and Methods Using Autocad software and plate geometry, a 3D finite element model of the maxilla was made with a miniplate at the infrazygomatic buttress and a mandibular miniplate at the mandibular parasymphysis. Stress distributions and displacements were analyzed in Von Mises stress form using Ansys software.  Results In the implant study, the Von Mises stress in bone (Mpa) was 142 Mpa for the 1 mm diameter implant, which was the lowest compared to 170 Mpa for the 0.5 mm pitch and 233 Mpa for the 1.5 mm pitch. Whereas in skull study when 2N elastic force was applied for a 2 mm diameter minimplant, the maximum Von Mises stress at 0.5mm,1mm and 1.5mm thread pitch was (18.454 Mpa, 18.47 Mpa, and 18.344 Mpa. For elastic force of 4N was (18,465 Mpa, 18.492 Mpa and 18.244 Mpa), for 6N elastic force was 18.388 Mpa, 18.43 Mpa and 18.086 Mpa), and for 8N was (18.272 Mpa, 18.324 Mpa and 17.883 Mpa), which was similar compared from other two diameters.  Conclusion When comparing 1.5 mm, 2 mm, and 2.5 mm diameter implants with 0.5 mm, 1 mm, and 1.5 mm pitch thread , the 2 mm diameter at 1 mm pitch thread shows the least strained bone in the implant study. Whereas,in the skull study, 2 mm diameter mini-implants had similar stress distribution in the maxilla and mandible,in all the thread pitches and elastic force which shows pitch variants and different force application is not a factor for stress distribution in the bone.