The Journal
Invisalign was also successful with
straightening teeth by rotation, and the
alignment by Invisalign had the same OGS
points with fixed braces 4.
According to Nguyen and Chang, the mean
accuracy of the incisor rotation was 60%, the
molar rotation was 50%, the premolar rotation
was 47% and the rounded teeth (canine and
premolar) was 39% 5.
G. Translation
Although the translational movement is
programmed, the results still showed the
uncontrolled tipping that created some clinical
implications 12. Because translational
movements with aligners are difficult with
aligners.
The translational movement used to close
extraction spaces is poorly predicted 1. None of
the patients completed the initial treatment with
two or more extractions of premolars because
of the excessive tooth tipping in the locations of
extractions 3.Although the gap caused by tooth
extraction may be closed completely, achieving
the parallelism of the roots is still a major
challenge, especially in the lower jaw 3.
3] Efficacy of clear aligners depends upon;
A] Patient Compliance
Patients are advised to wear aligners for at least
20 hours per day . The compliance of patient is
critical factor to the treatment of Invisalign. To
control for the patient's compliance, a
compliance indicator can be used . However,
there is currently no clinical studies on this
issue.
B] Activation time
Currently, the majority of patients are
recommended to change aligners every two
weeks ever though there is not enough
evidence for this. There were no significant
differences between the change of aligners
every week or two weeks. Orthodontic teeth
movement during the first week is more than 4.4
times the second week for two- weeks
prescribed wear time 12.
8
Successful rate of completing the initial set of
aligners is higher at two-weeks activation time
(37%) than one-week activation time (21%) 3.
C]Materials
There were no significant differences between
hard and soft materials in the completion of
series of aligners (2, 3) . However, in four
different groups of treatment protocols, the
combination of hard materials and two-weeks
activation times had the best results in all the
measurements of occlusal improvement and
alignment 2.
Although, the aligner degradation has not been
fully studied, it seems that the aligner‟s ability of
force magnitude is reducing over time.
Research on material fatigue did not detect any
difference in tooth movement between the two-
weeks activation time group and the group who
wore a new aligner after one week of two weeks
prescribed activation time 12.
Discussion
So which tooth movements are possible using
clear aligners?
The study of Vlaskalic (et al) was concluded that
although Invisalign can be an alternative for
removable or fixed orthodontic appliances in
select cases, by comparing the results and the
effectiveness of Invisalign treatment with
traditional orthodontic treatments, it is clear that
more studies are needed that have further
clinical prospective, controlled studies with
appropriate sample sizes and the use of
assessment objective methods to evaluate the
results 1.
There are three studies about the accuracy of
tooth movements (5,8, 9). The study by Nguyen
and Cheng concluded that clinicians should use
overcorrection and refinement to complete
treatment goals. In this study, the mean
accuracy of anterior tooth movement was
56%5. On the other hand, in the study of
Kravitz, the mean accuracy of anterior tooth
movement was lower at 41%.
Vol. 14 No. 1
Jan-Apr 2018