Abstract
Statement of problem
The output torque delivered by a dental implant toggle-style torque wrench is known
to be affected by activation rate. The International Organization for Standardization
(ISO) established the ISO 6789-1 standard to provide guidance on activation rates
relative to desired output torque in the Nm torque range. Whether the ISO 6789-1 standard
applies at the relatively lower dental torque ranges is not known, and little information
is available on the activation rates that clinicians use and how this may affect output
torque.
Purpose
The purpose of this in vitro study was to determine how output torque values vary
with the activation rates used by clinicians at dental implant-relevant target torque
values.
Material and methods
To determine clinically relevant activation rates, a new adjustable dental implant
toggle-style torque wrench was activated from 0 to 25 Ncm target torque by 5 prosthodontists
by using a custom mandibular and maxillary typodont model containing implants and
abutments with screws. This provided a baseline of activation rates (mm/sec). Data
were transferred to a computerized numerical control model incorporating a variable
speed linear motor, which was used to drive a dental implant toggle-style torque wrench
attached to an electronic torque measuring device. Constant speed and a regulated
dual-speed-assigned 80/20 rate group, where 80% of target torque value was delivered
first, then a pause, and the final 20% at different speeds as suggested by the ISO
6789-1 standard, were evaluated. Fast, medium, and slow rates were categorized and
applied with target torque values of 10, 25, and 35 Ncm, respectively, for n=12 activations.
The output torque values were recorded for both constant and 80/20 groups and compared
with the desired target torque values. Data were statistically analyzed with 1-way
ANOVA and the Scheffé post hoc paired t test (α=.05).
Results
The clinicians’ activation rates from 0 to 25 Ncm on the typodont model converted
into linear speeds resulted in fast =24.19 mm/sec, medium =14.5 mm/sec, and slow =7.25
mm/sec. When actioned at a constant rate, the mean output torque values were generally
in the order of slow > medium > fast in activation rates. Generally, precision output
torque decreased as target torque increased, especially when slow and medium rates,
either constant or regulated 80/20 were used. All mean output torque for slow, medium,
and their 80/20 variants were greater than target torque. Fast and 80/20 fast produced
the lowest mean output torque values for all torque settings, and at the 35 Ncm setting,
the dental implant toggle-style torque wrench output torque mean values were lower
than target torque. Statistically significant differences (P<.05) were found among groups, most notably in the 80/20 dual-speed groups, especially
in comparisons with the 80/20 fast rate group. When the target torque value was 10
Ncm with the 80/20 fast rate, the output torque value deviated from the maximum ISO
limit by more than 6%.
Conclusions
The rate of actioning a dental implant toggle-style torque wrench influenced the delivered
torque value, with fast rate actioning producing lower and less precise output torque
values.
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Article info
Publication history
Published online: September 02, 2021
Footnotes
All authors contributed in equal amounts to this article.
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.
