Evaluation of Stress Distribution on Mandibular Implant-Supported Overdentures With Different Bone Heights and Attachment Types: A 3D Finite Element Analysis

Abstract

The biomechanical behavior of the edentulous mandible with bone irregularities that has been rehabilitated with implant-supported overdentures has become an important factor for treatment planning. Restorative options, including dental implants with various attachments, affect the stress distribution. The purpose of this study was to evaluate the stress distribution of cortical bone around the implant neck and implant structures in overdentures with two different attachment types at the edentulous mandible and with different bone heights using three-dimensional finite element analysis. Five three-dimensional models of an edentulous mandible were designed and implemented. Ten models were constructed with ball and locator attachments. Static bilateral and unilateral vertical and oblique occlusal loads with magnitudes of 100 N were applied to the overdentures. The principal stresses were higher in the presence of oblique loads compared to vertical loads in all the analyzed models. Maximum principal stresses were observed around the mesial side of the contralateral implant, and the minimum principal stresses were noted around the distal side of ipsilateral implant during unilateral vertical loading. These patterns were reversed during oblique loadings. The ball attachment models yielded lower von Mises stress values than the locator models at all the loading conditions, while the stress distributions were similar in the models with the same and different bone levels. Correspondingly, bone corrections due to irregularities may not be necessary in terms of biomechanics. The results of this study may provide clinicians a better understanding for the mandibular overdenture design in the cases at which different bone heights exist.

The effect of attachment types and implant level on the stress distribution in a mandibular overdenture: a 3D Finite Element Analysis

“…In the bilateral posterior loading condition, the difference between stress values in the cortical bone surrounding the implants was lower than in other loading conditions. This finding was similar to the study of Unsal et al [25]. The stress distribution pattern in the cases of bilateral loading was more evenly, so it could be recommended to consider bilateral balanced occlusion in overdentures [2,25].…”

Effects of overdenture attachment systems with different working principles on stress transmission: A three-dimensional finite element study

“…El-Anwar et al 33 stated that Locator attachments cause less stress than ball attachments. Unsal et al 10 reported that better biomechanical results were obtained in models with ball attachments. However, in both studies, the loading conditions were not suitable and the applied forces were far from imitation of the oral environment.…”

“…16,24 At different angles of load, the behavior of an attachment in stress transmission may be different. 10,35 Therefore, in the comparison of different attachment types, occlusal forces should be applied in a way to realistically simulate chewing.…”

“…The current knowledge in the literature also supports this. 10,38 It has been reported in the literature that the rate of the situations such as dental implant neck fractures, attachment screw fractures, or excessive bone resorption is low in the two dental implantretained overdenture prostheses. 39 The stresses transmitted to the attachment structure were evaluated by various authors in terms of the quicker deformation of the attachments.…”

“…The prognosis of dental implants greatly depends on the stress and load distribution of occlusal loads transferred via the attachment systems to the dental implants; in the dental literature, there are numerous studies that have evaluated the stress and occlusal load distribution on the dental implants and supporting tissues transferred via the attachments. 9,10 Daas et al 11 investigated the rigid and resilient attachment configurations, and they concluded that "resilient attachments allowed for an increase of the mastication load transiting through denture bearing surface". Due to various deficiencies in existing attachments and certain commercial concerns, new dental systems are being introduced to the dental market day by day.…”