Prevention of distal extension cantilever fracture in mandibular overdentures

Abstract

1.-Effect of bar design and dimensions on bar extension fracturePrevention of distal extension cantilever fracture in mandibular overdentures. Materials and methods:The 2 nd moment area and static strength were calculated for 11 frequently used bar designs using finite element analysis (FEA). For two specific designs (Ackermann round ∅ 1.8 mm and Dolder Y-macro, the former with and without a support rib) additional physical static and fatigue strength tests were included. Results:The FEA static strength data corresponded well to the 2 nd moment area (a similar ranking when maximum allowed force was considered). The application of a rib support (Ackermann ∅ 1.8 mm) and limitations of the bar extension length (6 mm for the Ackermann ∅ 1.8 mm, 8 mm for the Dolder Y-macro) allowed the bars to exceed 5x10 6 cycles of 120 and 250 N respectively, before fracture. The region of highest stresses in FEA corresponded well with the locations of the fractures observed in static-and fatigue testing. Conclusions:With some simple guidelines/modifications, the number of bar extension fractures can be reduced significantly. Clinical significanceThis study focusses on distal bar extensions which improve the positioning of an implant supported overdenture. By combining laboratory testing and finite element simulations we aim to: (1) explain why fractures occur (dependent on physical characteristics of the bar), and (2) give clinical guidelines on how to prevent such fractures. 2.-Effect of bar design and dimensions on bar extension fracture

Mandibular two‐implant overdentures with CAD‐CAM milled bars with distal extensions or retentive anchors: A randomized controlled trial

“…In most complete denture cases, this is located between the second premolar and the first molar. With 15 mm extensions, the superstructures used in the EG of this trial reached almost to this point, thus providing a sound support during mastication (Katsoulis et al., 2015; Quirynen et al., 2015; Semper et al., 2010). Since all the EG dentures were equipped with brand‐new occlusal surfaces, it might have supported the faster improvement of the subjective chewing ability.…”

New Dental Implant with 3D Shock Absorbers and Tooth-Like Mobility—Prototype Development, Finite Element Analysis (FEA), and Mechanical Testing

“…Other studies suggest using this method to replace physical testing [54] in the early phases of implant development, in order to evaluate fatigue resistance, with reduced costs and time. Physical testing in conjunction with FEA are also recommended by some authors, proving the similitude of their results during implant [55] and even prosthetic restorations testing [56].…”

Clinical applications of occlusion principles in implantology - Narrative review

“…A disadvantage of using a distal cantilever is the outcome of its location and intensity of masticatory forces. 36 Contact must be avoided at the distal aspects of cantilever during lateral excursions. 32 Cantilevers over 15 mm have a greater probability of failure.…”