Load-bearing capacity of screw-retained CAD/CAM-produced titanium implant frameworks (I-Bridge®2) before and after cyclic mechanical loading

Abstract

Implant-supported screw-retained fixed dental prostheses (FDPs) produced by CAD/ CAM have been introduced in recent years for the rehabilitation of partial or total endentulous jaws. However, there is a lack of data about the long-term mechanical characteristics.ObjectiveThe aim of this study was to investigate the failure mode and the influence of extended cyclic mechanical loading on the load-bearing capacity of these frameworks.Material and MethodsTen five-unit FDP frameworks simulating a free-end situation in the mandibular jaw were manufactured according to the I-Bridge®2-concept (I-Bridge®2, Biomain AB, Helsingborg, Sweden) and each was screw-retained on three differently angulated Astra Tech implants (30º buccal angulation/0º angulation/30º lingual angulation). One half of the specimens was tested for static load-bearing capacity without any further treatment (control), whereas the other half underwent five million cycles of mechanical loading with 100 N as the upper load limit (test). All specimens were loaded until failure in a universal testing machine with an occlusal force applied at the pontics. Load-displacement curves were recorded and the failure mode was macro- and microscopically analyzed. The statistical analysis was performed using a t-test (p=0.05). ResultsAll the specimens survived cyclic mechanical loading and no obvious failure could be observed. Due to the cyclic mechanical loading, the load-bearing capacity decreased from 8,496 N±196 N (control) to 7,592 N±901 N (test). The cyclic mechanical loading did not significantly influence the load-bearing capacity (p=0.060). The failure mode was almost identical in all specimens: large deformations of the framework at the implant connection area were obvious. ConclusionThe load-bearing capacity of the I-Bridge®2 frameworks is much higher than the clinically relevant occlusal forces, even with considerably angulated implants. However, the performance under functional loading in vivo depends on additional aspects. Further studies are needed to address these aspects.

Edentulous Ridges treatment with a CAD/CAM-Milled Screw-Retained Framework and possibility of Individually aligned Screw Channels: A Clinical Case Report and Review

“…However, researchers expect large stresses in the screw and connection area to cause deformation, which may affect the mechanical properties of these restorations. Dittmer et al [11] evaluated the effects of artificial aging on the load-bearing capacity of three implants-supported titanium frameworks using a cyclic mechanical loading test. No screw loosening or structure failure was reported during the cyclic mechanical loading; they suggest that this may be due to the passivity of the CAD/CAM-milled system.…”

Comparison of access-hole filling materials for screw retained implant prostheses: 12-month in vivo study

“…Screw-retained implant restoration has also some disadvantages including the difficulty to get a right positioning of the access-hole compatible with a suitable aesthetic appearance and the aesthetic result of the access-hole restoration [16]. Inclined abutment or angling the screw channel can be an option to ameliorate the aesthetical outcomes [17, 18]. Moving the access hole to an occlusal or palatal/lingual zone would increase the indication of screw retained implant restoration.…”

Untitled

“…FCDs can be connected to implant fixtures in two ways: 1) by placing a screw-retained abutment onto the dental implant and fixing it with the FCD retaining screw; and 2) by directly screwing the superstructure to the implant [11]. Angled screwretained abutment options can compensate for misaligned implants to a certain degree; however, in complex situations, angled abutments do not produce a natural-looking emergence and can thus adversely affect esthetics [11].…”

“…The angulation allows the screw channels to be angled into the lingual side, making it possible to create multi-unit FCDs and achieve satisfactory esthetics at the same time. Additionally, this technology is compatible with various implant systems [11].…”