The Journal
According to the study of Kravitz (et al.), only 13
of the 64 teeth that protruded was greater than 1
mm and none protruded more than 2 mm. It was
interesting that the accuracy of posterior
extrusion was 52%, which is higher than the
5
prediction .
The alignment of the marginal tooth edges that
requires vertical control of tooth movement in
the Invisalign group and fixed braces was
equivalent. This suggests that Invisalign can
actually level arches as successfully as fixed
braces. But Invisalign can not create a proper
occlusion compared to fixed braces. Perhaps
this is due to the fact that aligner has a limitation
to extrude the teeth, unless there is a significant
undercut. Besides, Invisalign covered occlusal
surfaces of teeth preventing the settling of the
occlusion 4 .
D. Tipping
In Pavoni‟s study, Invisalign showed the ability
to tip crowns easily . Invisalign can easily tip
crowns but cannot tip roots because of the lack
10
of control of teeth movement . The tipping
movement can be done with Invisalign readily 1.
The removable aligners showed the ability to
move teeth up to 6mm by tipping incrementally
into the spaces 4 . The role of uncontrolled
tipping and loss of anchorage complicate the
progression of programmed aligners.
The accuracy of tipping for Invisalign was found
to be range from 40.5% to 55%.
AUTHOR INTRUSION
Nguyen and Cheng[5] Canine tipping 44%
Premolar tipping 55%
Kravitz et al.2009
6
According to Nguyen and Cheng„s study, the
mean accuracy of premolar tip was 55% and of
5
canine tip was 44% .
Clear Aligner is not effective in controlling
mesiodistal tipping unless being used with
special attachments. There are two types of
attachments: Clear Aligner power grip 2 (MDI-
mesial / distal inclination) to help move the
crowns mesially and move the roots distally;
and power grip 3 (DMI - distal / mesial
inclination) to move the crowns distally and
move the roots mesially .
The average accuracy of anterior mesialdistal
tip was 40.5%. The highest accuracy was
achieved by the maxillary lateral incisors
(43.1%) and the lowest was achieved by the
mandibular canines (26.9%) 9.
Boyd reported a case of distalization more than
3 mm in Class II division 2 patient (Boyd), but
Djeu (et al) and Clements (et al) concluded that
it was difficult to use invisalign to correct
anteroposterior discrepancies (4, 2).
The accuracy of labiolingual tip was evaluated
according to two groups: labial crown tip and
lingual crown tip. Only the labial crown tip of the
mandibular canines had a higher accuracy
(44.8) than lingual crown tip (42.5%), while the
other anterior labial crown tips were was less
accurate than the lingual crown tip. The average
accuracy of anterior lingual crown tip was
53.1%, while labial crown tip was only 37.6%.
The pretreatment malocclusion affected the
accuracy of the labiolingual crown tip 9.
Mesiodistal tip
Anterior 40.5%
Labiolingual tip
Anterior 44.7%
Vol. 14 No. 1
Jan-Apr 2018