Failure Modes and Survival of Anterior Crowns Supported by Narrow Implant Systems

Abstract

The reduced hardware design of narrow implants increases the risk of fracture not only of the implant itself but also of the prosthetic constituents. Hence, the current study is aimed at estimating the probability of survival of anterior crowns supported by different narrow implant systems. Three different narrow implant systems of internal conical connections were evaluated (Ø3.5×10 mm): (i) Active (Nobel Biocare), (ii) Epikut (S.I.N. Implant System), and (iii) BLX (Straumann). Abutments were torqued to the implants, and standardized maxillary incisor crowns were cemented. The assemblies were subjected to step-stress accelerated life testing (SSALT) in water through load application of 30 degrees off-axis lingually at the incisal edge of the crowns using a flat tungsten carbide indenter until fracture or suspension. The use level probability Weibull curves and reliability for completion of a mission of 100,000 cycles at 80 N and 120 N were calculated and plotted. Weibull modulus and characteristic strength were also calculated and plotted. Fractured samples were analyzed in a stereomicroscope. The beta (β) values were 1.6 (0.9-3.1) and 1.4 (0.9-2.2) for BLX and Active implants, respectively, and 0.5 (0.3-0.8) for the Epikut implant, indicating that failures were mainly associated with fatigue damage accumulation in the formers, but more likely associated with material strength in the latter. All narrow implant systems showed high probability of survival (≥95%, CI: 85-100%) at 80 and 120 N, without significant difference between them. Weibull modulus ranged from 6 to 14. The characteristic strength of Active, Epikut, and BLX was 271 (260-282) N, 216 (205-228) N, and 275 (264-285) N, respectively. The failure mode predominantly involved abutment and/or abutment screw fracture, whereas no narrow implant was fractured. Therefore, all narrow implant systems exhibited a high probability of survival for anterior physiologic masticatory forces, and failures were restricted to abutment and abutment screw.

Comparison of De-Torque and Failure Load Evaluation of Selective-Laser-Sintered CoCr, CAD-CAM ZrO, and Machined Implant Abutment/Restoration

“…This study's findings are in line with the existing literature on the failure modes of implant abutments. For instance, a study on the failure modes and survival of anterior crowns supported by narrow implant systems reported that the failure mode predominantly involved abutment and/or abutment screw fracture, highlighting the relevance of understanding specific failure patterns for different implant components [26]. Additionally, research on the effect of fatigue loading and the failure mode of different ceramic implant abutments provides insights into the failure modes of specific abutment materials, which is relevant to the observed distinctive failure patterns in the present study [27].…”

Reliability and Failure Mode of Ti-Base Abutments Supported by Narrow/Wide Implant Systems

“…Three stress profiles for step stress accelerated-life testing (SSALT), based on the fatigue behavior of narrow implant systems previously published by our group [ 34 ], were used in the present study. Eighteen specimens per experimental group were distributed in a 3:2:1 ratio to mild (n = 9), moderate (n = 6) and aggressive (n = 3) stress profiles, named based on its step-wise load increase, as detailed elsewhere [ 24 , 29 , 31 , 33 ].…”