Abstract
Statement of problem
Information regarding the rotational freedom of internal connection implants is sparse.
Purpose
The purpose of this in vitro study was to compare the rotational freedom of different
internal conical and internal nonconical connections.
Material and methods
Thirty implants, 30 straight manufactured standard abutments, and 30 standard abutment
screws were obtained for each of the 5 implant systems tested. Three implant systems
had indexed internal conical connections with different antirotational geometries:
hexagon (Naturall+), cam-groove (ID CAM M), and octagon (Bone Level). Two implant
systems had internal nonconical connections with hexagonal antirotational geometry
(Tapered Screw-Vent and Seven). The implants were mounted in a steel plate, and a
metal reference arm was attached to the abutment. Before tightening the standard abutment
screw, a modified torque wrench was used to rotate the abutment clockwise until reaching
the clockwise rotational endpoint. This modified torque wrench was connected to the
abutment's outer surface. It allowed free access to the standard abutment screw for
a second torque wrench, specific to each implant system. The modified torque wrench
applied a controlled torque of 5 Ncm, which held the abutment at the clockwise rotational
endpoint. The standard abutment screw was then tightened to the manufacturer’s specified
torque value with the second torque wrench. Angle value corresponding to the clockwise
endpoint was measured microscopically between a fixed reference point on the steel
plate and the reference arm. The abutment was then unscrewed and removed. The same
procedure was carried out to rotate the abutment counterclockwise and measure the
angle value corresponding to the counterclockwise rotational endpoint. The rotational
freedom was finally determined from the differences in the angles between the clockwise
and counterclockwise rotational endpoints. Rotational freedom angle values were summarized
as descriptive statistics (means, standard deviations). The normality test (Kolmogorov-Smirnov)
was applied, and the Kruskal-Wallis test was performed. The Wilcoxon signed-rank test
was used to isolate the implant system differences from each other (α=.05).
Results
The lowest mean rotational freedom angles were obtained for Bone Level (conical connection,
0.17 degrees) and Tapered Screw-Vent (nonconical connection, 0.05 degrees). These
systems were followed in increasing order by ID CAM M (conical connection, 0.50 degrees),
Seven (nonconical connection, 1.98 degrees), and Naturall+ (conical connection, 2.49
degrees). Compared with each other, all implant systems had significant statistical
differences in rotational freedom angles (P<.05).
Conclusions
Significant differences were found among the 5 implant systems. The lowest mean rotational
freedom angles were obtained both with a conical connection (Bone Level) and a nonconical
connection (Tapered Screw-Vent).
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Article info
Publication history
Published online: July 05, 2021
Footnotes
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Identification
Copyright
© 2021 by the Editorial Council for the Journal of Prosthetic Dentistry.
