Are Increased Masticatory Forces Risk for Primary 2nd Molars without Successors? A 3D FEA Study

Persistent primary teeth with healthy crown-root structures and acceptable functional and esthetic properties may be preserved over a long-term period if needed. However, they may experience root resorption, ankylosis or infraocclusion especially in the second or third decades of life. Despite a lack of sufficient detailed data, increases in occlusal forces by age are known to cause destructive stresses on root surfaces and periodontal tissue. The aim of this study was to evaluate the effect of increasing occlusal forces on mandibular persistent primary molars by using 3D finite element analysis. The impact of increased masticatory forces on compressive and tensile stresses in tooth and surrounding tissue was simulated in two different models (simulating child and adult mouths) by using 3D finite element analysis. In both models, the stress values increased by age and compressive stresses were seen on internal root surfaces, while the tensile stresses focused on the furcation area and external root surfaces. It was concluded that practices such as reducing occlusal surface width may be used to diminish the occlusal forces for long-term tooth survival in persistent primary molars.