The Biomechanical Impact of Loss of an Implant in the Treatment with Mandibular Overdentures on Four Nonsplinted Mini Dental Implants: A Finite Element Analysis

Abstract

The aim of this study was to evaluate the biomechanical impact, in terms of stress and displacement, at the level of a mandibular overdenture, on four mini dental implants (MDIs) after the loss of an implant. A three-dimensional virtual model was obtained by scanning the overdenture, and a biomechanical analysis was carried out, using the finite element method (FEM). The displacements of the overdenture and the equivalent von Mises stresses were evaluated using logarithmic scales. In the case of a mandibular overdenture on four MDIs inserted in the interforaminal area, the frontal loading generated the lowest values for the von Mises stresses, and the bilateral loading generated the least displacement when two implants were inserted in the canine area and two in the molar area. The highest von Mises stress was observed during frontal loading in the situation of the mandibular overdenture on four MDIs, two of which were inserted in the canine area and two in the molar area, following the loss of an implant in the canine area. The largest displacement was noted in the mandibular overdenture on four interforaminal MDIs during unilateral loading, following the loss of a distally inserted implant. The FEM analysis showed aspects that correlated with clinical observations, with predictive value. The concentration of von Mises stresses, and the occurrence of some displacements of the prosthodontic restoration, can explain the emergence of some complications in the overdenture’s biodynamics, and the increased risk of fracture. Complications can be prevented by choosing a certain number of implants and a topographical distribution correlated with biomechanical aspects, and by proposing a correct occlusal scheme with optimal functional loading.

Influence of Implant Number on Peri-Implant and Posterior Edentulous Area Strains in Mandibular Overdentures Retained by the New Ti–Zr (Roxolid®) Mini-Implants as Single-Units: In Vitro Study

“…The differences between the results of this study and other studies on biomechanical behavior [37,38,[47][48][49][50][51][52][53][54] may be due to different mini-implant materials (Ti-Zr vs. Ti-Al6-V4), different retention mechanisms (Optiloc ® Retentive System vs. "O"-ring), different implant designs and neck widths [55], different dimensions of implants [56,57], small differences in strain measurements and different residual ridge forms. We bonded strain gauges as close as possible to the implant-bone interface due to the assumption that stress and strains would be highest where two materials with different stiffnesses meet.…”

Patients’ Satisfaction with Mandibular Overdentures Retained Using Mini-Implants: An Up-to-16-Year Cross-Sectional Study

“…Still, the primary disadvantage of this approach is the reduced surface contact with the surrounding bone (i.e., lesser mechanical strength to functional loading) [42,43] and the limited surface area of small-diameter implants (i.e., less resistance to occlusal forces) [44,45]. However, Teodarescu et al demonstrated that a sufficient number of mini-implants and a functional topographical distribution based on biomechanical masticatory forces could prevent these mechanical challenges [46]. Also, Chatrattanarak et al found that the configuration of two mini-implants supporting mandibular overdentures with an immediate loading approach had a significantly higher success rate, cost effectiveness, and patient satisfaction after eight years of follow-up compared to four mini-dental implant-retained mandibular overdentures [7].…”

Toward Digital Twin Development for Implant Placement Planning Using a Parametric Reduced-Order Model

“…Therefore, many studies used FEA to reduce overload before implant placement. Most studies conduct stress analysis based on new implants [48,49], changes in implant materials [50][51][52], and various variables [53]. Although this can achieve better implants and placement plans, it does not help with real-time placement depending on the condition of the patient.…”