Scanning Electron Microscopy Analysis of the Adaptation of Single-Unit Screw-Retained Computer-Aided Design/Computer-Aided Manufacture Abutments After Mechanical Cycling

Abstract

Purpose: To measure the microgap between dental implants and custom abutments fabricated using different computer-aided design/computer-aided manufacture (CAD/CAM) methods before and after mechanical cycling. Materials and Methods: CAD software (Dental System, 3Shape) was used to design a custom abutment for a single-unit, screw-retained crown compatible with a 4.1-mm external hexagon dental implant. The resulting stereolithography file was sent for manufacturing using four CAD/CAM methods (n = 40): milling and sintering of zirconium dioxide (ZO group), cobalt-chromium (Co-Cr) sintered via selective laser melting (SLM group), fully sintered machined Co-Cr alloy (MM group), and machined and sintered agglutinated Co-Cr alloy powder (AM group). Prefabricated titanium abutments (TI group) were used as controls. Each abutment was placed on a dental implant measuring 4.1 × 11 mm (SA411, SIN) inserted into an aluminum block. Measurements were taken using scanning electron microscopy (SEM) (×4,000) on four regions of the implant-abutment interface (IAI) and at a relative distance of 90 degrees from each other. The specimens were mechanically aged (1 million cycles, 2 Hz, 100 N, 37°C) and the IAI width was measured again using the same approach. Data were analyzed using two-way analysis of variance, followed by the Tukey test. Results: After mechanical cycling, the best adaptation results were obtained from the TI (2.29 ± 1.13 µm), AM (3.58 ± 1.80 µm), and MM (1.89 ± 0.98 µm) groups. A significantly worse adaptation outcome was observed for the SLM (18.40 ± 20.78 µm) and ZO (10.42 ± 0.80 µm) groups. Mechanical cycling had a marked effect only on the AM specimens, which significantly increased the microgap at the IAI. Conclusion: Custom abutments fabricated using fully sintered machined Co-Cr alloy and machined and sintered agglutinated Co-Cr alloy powder demonstrated the best adaptation results at the IAI, similar to those obtained with commercial prefabricated titanium abutments after mechanical cycling. The adaptation of custom abutments made by means of SLM or milling and sintering of zirconium dioxide were worse both before and after mechanical cycling.

Influence of eccentric cyclic loading on implant components: Comparison between titanium and zirconia abutments

“…10A). This is also consistent with past reports which used the external joint system 18) . Zirconia is said to undergo sintering contraction as it is machined as semi-sintered blocks; these blocks are later subjected to a complete sintering in a high temperature furnace.…”

“…The marginal gap was measured by referring to past report 18) . The gap was captured at a magnification of 5,000 using a scanning electron microscope (SEM; SU6600, Hitachi, Tokyo, Japan) from a direction perpendicular to the long axis of the implant using the same platform, and the distance between the bottom edge of each abutment and the top edge of the implant was measured using a measuring tool in the SEM.…”

“…There are many reports on the effects of cyclic loading on implant components using the external joint system with zirconia abutments 6,7,[14][15][16][17][18] ; however, a very few studies used the internal joint system [19][20][21] . The paper that observed the inner surface of the implant body evaluated implant components with titanium and zirconia abutments only under an eccentric load 19) .…”

Model‐less digital workflow for the replication of an existing complete fixed implant‐supported prosthesis using an intraoral scanner

“…Dental CAD/CAM systems allow the prosthetic seating interface to be milled directly onto the prosthetic structure or by cementing on prefabricated titanium‐based abutments . The cement on strategy combines the strength and fit precision of a titanium dental implant‐abutment interface with the esthetics of shaded custom‐milled ZO and results in low wear to prosthetic abutments . An intraoral cementation of titanium interfaces was chosen in the present patient, as the cement could minimize some misfit, creating an accommodation layer between Ti‐base and prosthesis.…”

Accuracy of Original vs. Non‐Original Abutments Using Various Connection Geometries for Single Unit Restorations: A Systematic Review

“…Of the 12 studies measuring gap widths between OAs/NOAs and implants with an external connection, 4 studies found better precision of fit with OAs compared with NOAs. 1,[38][39][40] One study found that although the OAs statistically fit better than NOAs, both were within acceptable limits 33 ; 5 studies reported no differences between OAs and NOAs. 7,9,10,42,43 Two studies reported better fit when the NOAs were connected to the implants, compared with the OAs.…”