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

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

AIM

This study aimed to compare the torque loss, fracture load, compressive strength, and failure types of selective-laser-sintered cobalt chromium (SLM-Co-Cr), computer-aided design and computer-aided manufacturing zirconium oxide (CAD-CAM-ZrO), and machined titanium (Ti) implant abutments.

METHODS

Thirty endosseous dental implants were vertically embedded with machined Ti (control group), CAD-CAM-ZrO, and SLM-Co-Cr abutments. Abutment fabrication involved CAD-CAM milling and SLM technology. The de-torque assessment included preload reverse torque values (RTVs), cyclic loading, and post-RTVs using a customized protocol. Fracture load assessment employed ISO-14801 standards, and statistical analysis was conducted using ANOVA and Tukey Post hoc tests (p < 0.05).

RESULTS

In pre-load RTVs, SLM-Co-Cr showed the lowest mean torque loss (24.30 ± 2.13), followed by machined Ti (27.33 ± 2.74) and CAD-CAM-ZrO (22.07 ± 2.20). Post-load RTVs decreased for all groups. Fracture load and compressive strength were highest for SLM-Co-Cr, with significant differences among groups (p < 0.001). Fracture types included abutment failures in SLM-Co-Cr and machined Ti, while CAD-CAM-ZrO exhibited crown separation with deformation.

CONCLUSION

SLM-Co-Cr-fabricated implant abutments exhibited superior stability and resistance to rotational forces, higher fracture loads, and greater compressive strength compared to CAD-CAM-ZrO and machined Ti.

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

To assess the reliability and failure modes of Ti-base abutments supported by narrow and wide-diameter implant systems. Narrow (Ø3.5 × 10 mm) and wide (Ø5 × 10 mm) implant systems of two different manufacturers with internal conical connections (16°) and their respective Ti-base abutments (3.5 and 4.5 mm) were evaluated. Ti-base abutments were torqued to the implants, standardized metallic maxillary incisor crowns were cemented, and step stress accelerated life testing of eighteen assemblies per group was performed in three loading profiles: mild, moderate, and aggressive until fracture or suspension. Reliability for missions of 100,000 cycles at 100 and 150 N was calculated, and fractographic analysis was performed. For missions at 100 N for 100,000 cycles, both narrow and wide implant systems exhibited a high probability of survival (≥99%, CI: 94-100%) without significant differences. At 150 N, wide-diameter implants presented higher reliability (≥99%, CI: 99-100%) compared to narrow implants (86%, CI: 61-95%), with no significant differences among manufacturers. Failure mode predominantly involved Ti-base abutment fractures at the abutment platform. Ti-base abutments supported by narrow and wide implant systems presented high reliability for physiologic masticatory forces, whereas for high load-bearing applications, wide-diameter implants presented increased reliability. Failures were confined to abutment fractures.

Comparative assessment of the primary stability of Straumann® BLX implant design using an in-vitro sinus lift-simultaneous implant insertion model

Straumann ®  BLX is a novel implant system, which has been proclaimed to provide an ideal primary stability in all types of bone. In the current study, the primary stability of Straumann ®  BLX implant systems with Straumann ®  tapered effect (TE) implants have been comparatively assessed in bovine ribs by using a simultaneous sinus elevation and implant insertion model.  In the study group, BLX (4.0 x 12 mm), TE (4.1 x 12 mm), BLX (4,5 x 12 mm) and TE (4.8 x 12 mm) were placed in each bony window, which resembles sinus maxillaris. As a control, BLX and TE implants with same sizes were inserted into the proximal diaphysis of the bovine ribs. A total of 40 implant insertions were performed. The stability was measured with resonance frequence analysis. In the study group, TE implants of 4.8 mm showed significantly higher values compared to 4.5 mm BLX implants (p=0.116). However, BLX implants of 4.0 mm in the control group showed higher stability compared to TE with 4.0 mm diameter. (p=0.014).  The primary stability of BLX implants in the control group was significantly higher compared to the experimental group in both widths (p=0.018 for BLX 4.0 and p=0.002 for BLX 4.5 respectively). The use of TE design with wide diameter in simultaneous implant placement with sinus lift could present higher ISQ values and might be more appropriate option for implant recipient sites with poor bone volume and quality. However, the advantage of BLX design in standard implant insertion protocols could be precious.