A finite element analysis of the stress distribution to the mandible from impact forces with various orientations of third molars

Abstract

High-impact forces are more likely to cause condylar rather than angular fracture when IM3s are missing. The risk of mandibular fracture is higher for partially than fully impacted third molars, with the angulation of impaction having little effect on facture risk.

Edentulous mandible with four splinted interforaminal implants exposed to three different situations of trauma: A preliminary three‐dimensional finite element analysis

“…Thus, the initial hypothesis that the site of direct force application will also represent the site of the increased fracture risk has been confirmed again and the characteristics of an edentulous mandible without implants may thus also be used for edentulous mandibles with four interforaminal implants 23,43,48 . In accordance with previous findings of de Santos et al, 23 the results showed that a direct force application in the region of the mental foramen and in the region of the mandibular angle will invariably induce increased stress levels in the edentulous mandible with or without implants and be associated with an increased fracture risk in these regions 42–44 …”

“…Strikingly, no increased stress levels at the site of force application could be seen with a frontal force application on the edentulous mandible with interforaminal implants as compared to edentulous mandibles without any implants 23 . In the event of a frontal force application, the impacting kinetic forces will be absorbed in the region of the interforaminal blocking and transmitted to the neighboring regions 40–42 . Therefore, no increased cortical stress levels at the site of direct force application will develop, but much rather the increased stress levels as well as the fracture risk will be transferred to the adjacent region of the mental foramen 41,43,44 .…”

“…23 In the event of a frontal force application, the impacting kinetic forces will be absorbed in the region of the interforaminal blocking and transmitted to the neighboring regions. [40][41][42] Therefore, no increased cortical stress levels at the site of direct force application will develop, but much rather the increased stress levels as well as the fracture risk will be transferred to the adjacent region of the mental foramen. 41,43,44 It can be assumed that the external implant transducer and that the external stabilization will counteract the initial weakening of the mandible by the implants.…”

“…23,43,48 In accordance with previous findings of de Santos et al, 23 the results showed that a direct force application in the region of the mental foramen and in the region of the mandibular angle will invariably induce increased stress levels in the edentulous mandible with or without implants and be associated with an increased fracture risk in these regions. [42][43][44] As a striking feature, the area of particular risk in the case of a frontal application of force is shifted away from the symphyseal region toward the region of the mental foramen. 44 With this obvious shift, the virtually identical site-namely the region of the mental foramen-could be identified as the site with increased stress levels and as the region of risk with both frontal symphyseal and lateral parasymphyseal force application.…”

“…[20][21][22][23]47,51,52 Considering the limitations of the study, it must be pointed out that the present study had an experimental design that represented only changes in the objects being evaluated. 20,41,42 As the risk for mandibular fracture is predominantly also influenced by the varying degree of mandibular atrophy and mandibular bone quality, a detailed quantitative statement as to what extent implant placement and, consequently, implant splinting may protect or negatively affect several regions cannot be made. 53,54 In summary, the findings showed that in the case of frontal trauma, four splinted interforaminal implants as being used clinically in the "All-on-4" concept will reduce the stress levels and the fracture risk in the area of the anterior implants and the mandibular neck and may increase the same in the region of the mental foramen.…”