In vitro differences of stress concentrations for internal and external hex implant–abutment connections: a short communication

Abstract

The aim of this study was to clarify the difference in the stress distribution patterns between implants with external-hex or internal-hex connection systems using in vitro models. Three 13 mm fixtures with external-hex and internal-hex connections were installed into an acrylic bone analogue. One piece abutments of 7 mm height was connected. Strain gauges were attached to the abutment surface, and the cervical and fixture tip areas of the bone analogue surface. Vertical and horizontal load applied was 30 N. Data were normalized for each model by obtaining values relative to the sum of the three values. Almost the same force distribution pattern was found under vertical load in both systems. Fixtures with external-hex showed an increase in strain at the cervical area under horizontal load, while in internal-hex fixtures the strain was at the fixture tip area. Within limitations of our model study, it was suggested that fixtures with internal-hex showed widely spread force distribution down to the fixture tip compared with external hex ones.

Biomechanical evaluation of internal and external hexagon platform switched implant-abutment connections: An in vitro laboratory and three-dimensional finite element analysis

“…Concerning the geometry of implant connection (internal vs. external), higher reliability was observed in specimens with internal connection regardless of the abutment diameter. These findings are in agreement with other studies that pointed that deep joints show increased stability favoring structural strength of implant systems [24,32,48]. It should be noted, however, that due to engineering design constraints such as minimum wall thickness for proper mechanical performance of each of the different connection systems, differences in both external and internal features of the implant, abutment, and screw designs will exist.…”

Effect of Different Abutments and Connections in Deformation Crestal Bone

“…6,7 Studies compared external and internal hexagon type prosthetic connections and noted that the internal design has a larger contact area that extends deeper into the implant, which leads to greater stability of the connection and better load distribution around the bone. 5,[8][9][10] The implant design biomechanically influences the distribution of loads only in cases of implants fitted immediately after extraction and does not affect cases of late loading. 11 …”

Zirconia ceramics in metal-free implant dentistry

“…With the internal connection system, the connection formed through inserting the extending part of the abutment into the interior of the implant. The internal connection is more popular than the external one because it better distributes the load and thereby provides higher fracture strength [56,62]. In the internal connection system, the abutment connector can have various geometries, including hexagonal, octagonal, and conical (Morse taper) shapes.…”