In vitro assessment of connection strength and stability of internal implant-abutment connections

Abstract

Background: Various connections have been machined to improve the fit between the dental abutment and implant. In vivo, the instability created by imprecisely fitting components can cause soft tissue irritation and bacterial colonization of the implant system. The aim of this study was to quantify abutment stability under in vitro force applications. Methods: Abutment stability and fit were quantitatively measured after application of rotational, vertical, and horizontal forces. Findings: The abutment connection held by friction (Friction-Fit) was the only group to have 0°angular rotation. A significantly greater vertical force was required to pull the abutment from the implant for the Friction-Fit connection as compared to all other experimental groups. The abutment connection held by a mechanically locking friction-fit with four grooves (CrossFit) and Friction-Fit demonstrated significantly lower lateral movement as compared to all other connections. The remaining connections evaluated included two hexagon connections that rely on screw placement for abutment fit (Conical + Hex #1 and Conical + Hex #2), one connection with protruding slots to align with recessed channels inside the implant (Conical + 6 Indexing Slots), and an internal connection that allows for abutment indexing every 120°(Internal Tri-Channel). Interpretation: Internal connection geometry influenced the degree of abutment movement. Friction-Fit and CrossFit connections exhibited the lowest rotational and horizontal motions. Significant differences were found between Friction-Fit and CrossFit following the application of a vertical force, with the Friction-Fit requiring a significantly greater pull force to separate the abutment from the implant.

Radiographic Assessment of Accuracy of Fit for Different Conical Connection Abutments on Tapered Implants

“…(31,32) The internal implantabutment design resulted in better occlusal forces distribution and improved abutment stability in consequence of lowering of the rotational centre and protection of the retention screws, thus, resisting excessive lateral forces. (2,33) Moreover, this internal connection confirms appropriate abutment seating that ensures better microbial seal as well as better aesthetic outcomes. (32) On the top of that and in an attempt to decrease the micro-gaps between implants and abutments as much as possible, a superior type of internal connection was introduced depending on a premachined base with significant friction offered at the abutment-implant interface.…”

“…(1) Two-piece implant system involves an implant placed in the bone with an abutment connected to it by a screw and the final prosthesis will be constructed over the abutment. (2,3) Accordingly, these units end up with a lot of interfaces between implant system parts. (3) A great attention must be paid to the connection between the implant and the abutment as it is considered a critical interface that will affect the long-term survival rate of the implantsupported prosthesis.…”

“…(18) All these complications are considered mechanical failure. (2) In attempt to prevent all the aforementioned failures that are related to micro-gaps between abutment and implant, the ongoing development of more dependable implant-abutment connections with several evolution in materials and precision manufacturing of implant parts has gained popularity at the present time. (19)(20)(21)(22) Precise and passive fit between different implant parts in conjunction with biocompatibility and sufficient mechanical properties are listed among the most important properties that must be present in implant abutments to fulfill biological, mechanical and esthetic requirements and avoid further complications within the implant system.…”

Influence of Implant Connection, Abutment Design and Screw Insertion Torque on Implant-Abutment Misfit

“…To overcome some of the design limitations and bone loss of the external hexagonal connection, internal connection with a wide variety of shapes was introduced [12]. Internal connections provide better esthetics, better joint strength, an improved microbial seal, better long-term stability of the implant-abutment complex and better crestal bone levels in the short-medium term as compared to external connection [9,12,13]. Morse taper connection is a conical internal connection that creates a friction between the surfaces that result in cold-welding [14,15].…”

The importance of implant-supported overdentures in a bimaxillary complete edentulous patient – case report

“…The Straumann BLT implants are supplied with the Loxim Transfer Piece that is connected by a snap-in mounting to the implant. The 15° conical-cylindrical CrossFit® connection presents 4 internal grooves, which offer a mechanical locking friction fit, with long-term stability under loading conditions and minimization of screw loosening [11][12][13][14][15][16].…”