Mandibular molar uprighting using orthodontic miniscrew implants: a systematic review
Magkavali-Trikka et al. Progress in Orthodontics
Mandibular molar uprighting using orthodontic miniscrew implants: a systematic review
Panagiota Magkavali-Trikka 1
Georgios Emmanouilidis 0
Moschos A. Papadopoulos 0
0 Department of Orthodontics, School of Health Sciences, Faculty of Dentistry, Aristotle University of Thessaloniki , Thessaloniki , Greece
1 Hamdan Bin Mohammed College of Dental Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences , Dubai , United Arab Emirates
The purpose of this systematic review was to identify studies and present the use of miniscrew implants (MIs) as an alternative treatment to mandibular molar uprighting. An electronic search and handsearching were conducted by two independent reviewers to identify relevant articles, published up to January 27, 2017. In order to methodologically assess the eligible studies, a pilot checklist consisting of 22 items was also implemented. After exclusion of all the irrelevant papers, only 17 studies were included, presenting 27 cases of mandibular molar uprighting in all planes using both direct and indirect force traction by MIs. Regarding the quality evaluation, the mean score of the included studies was 13.2, indicating a rather poor methodology implemented in the majority of the included cases. Due to many advantages, MIs provide a unique treatment alternative and constitute a reliable solution for treating tipped or impacted molars. Regarding the force application, a direct method is simpler, as it requires one MI and a single bracket or button, minimizing the patient's discomfort and also reducing chair time compared to more complex indirect anchorage. It also eliminates the possibility of unwanted movement of the anchorage unit, which can occur even with indirect anchorage as a result of technical errors. However, direct anchorage has limitations in cases of lingually tipped or rotated molars because a single force may be insufficient to upright the tooth.
A tipped mandibular molar is a frequent situation
among orthodontic patients, which usually occurs after
premature loss of adjacent teeth leading to the
inclination of the molars [
]. Inadequate mandibular arch
length, excessive teeth size, loss of the adjacent first
molar, premature eruption of the mandibular third
molar, and unusually mesial eruption pathway of the
second molar can also cause its partial or total impaction
with a reported incidence of 0.03–0.3% of the general
population and 2–3% of orthodontic patients [
Tilted molars can cause numerous problems in a
patient’s mouth, especially if a prosthetic rehabilitation is
planned. According to Zachrisson, periodontal status
can be aggravated, with signs of inflammation, angular
bone loss, and an apparent pocket at the mesial surface
of a tipped mandibular molar [
]. In excessive
inclination, overeruption of the antagonist molar,
premature contacts, and occlusal interferences impede
prosthetic restoration [
]. However, molar uprighting into its
correct position leads to the normalization of the
functional and periodontal condition [
]. Finally, an impacted
mandibular second molar can lead to caries, periodontal
disease, or external root resorption of the adjacent first
Conventional methods for molar uprighting
Several orthodontic approaches are suggested for
mandibular molar uprighting, such as Australian uprighting
spring, cantilever spring, prefabricated Sander spring,
helical uprighting spring, NiTi coil spring, push spring
appliance, and traction from removable appliances are
few of the currently available options [
6, 8, 9
uprighting requires good anchorage control, and
subsequently, a full-arch fixed appliance is necessary.
Furthermore, ankylosed teeth, dental implants, and extraoral
appliances could also be effective, enhancing anchorage,
and protecting from undesirable tooth movements [
Among others, the Uprighter Jet developed by Carano
provides a complete control of molar uprighting,
minimizing extrusion, requiring no brackets, and no special
patient cooperation [
]. In another uprighting case of an
impacted molar, in combination with rapid maxillary
expansion (RME), vertical elastic forces were directed from
a hook on the RME device to an orthodontic attachment
bonded on the tooth to be uprighted. This method saves
time, requires no additional anchorage preparation, and
appears more physiologic as the force vector is in the
direction of normal eruption path [
]. According to
], surgical uprighting of lower second molars
is a quick procedure with minimal morbidity and
longterm prognosis. Most of the uprighted teeth remained
firm with excellent bone formation and periodontal
status after 18 months of follow up [
However, conventional treatment methods for molar
uprighting have some disadvantages, including
extrusion of the target molar, unwanted reciprocal
movement of the anchorage units, need for bulky
appliances, and longer treatment time [
1, 2, 12–15
In order to minimize the first two side-effects,
intraarch stabilization is usually needed [
2, 12, 13
is undertaken through the use of osseointegrated
implants. Yet, an osseointegrated dental implant is
costly, needs sufficient bone space, limiting our
choices, and is very difficult to be removed after the
treatment. It also requires osseointegration before
orthodontic force application, increasing the treatment
5, 10, 12
In addition, surgical uprighting should not be
considered as a routine method due to the possible pulp
necrosis, ankylosis, external root resorption, or even rupture
during the procedure. After treatment, occlusal
equilibration may be needed, and the post-surgical stability of
the tooth may be questionable [
]. Further, the
possibility of pulpal calcification and vitality loss is high [
Use of orthodontic miniscrew implants for molar uprighting
The development of orthodontic miniscrew implants
(MIs) provided solutions to most of the aforementioned
problems. MIs are fabricated from pure titanium or
titanium alloy with a diameter of 1–2 mm and length of
8–20 mm [
]. They remain stable during orthodontic
treatment with minimum anchorage loss and are more
effective than conventional anchorage means [
Their success rate ranges from 59 to 100% with an
average of 86.5% [
Their attachment to the bone is mechanical with no
intent to establish any form of osseointegration [
Therefore, after the treatment, when they are no longer
needed, they can be removed through a simple
procedure, with negligible risks for the patient .
This new type of skeletal anchorage is simpler, smaller,
less-invasive, and more economical than conventional
osseointegrated implants [
]. Moreover, MIs do not
require a long interval between placement and force
application since loading can occur immediately after
10, 16, 24
Their main advantage though is their ability to move
specific teeth or even the entire quadrants directly,
without involving other teeth or using inter-arch mechanics.
Thus, they eliminate the reaction forces usually applied
on the anchor teeth, leading to unwanted tooth
movement and anchorage loss [
5, 14, 15
]. Patients are also
more satisfied with the more invisible treatment
compared to conventional methods [
MI anchorage is preferable to conventional mechanics
when a third molar is in direct contact with the second
molar root [
]. In some cases, it is better from a
biomechanical perspective not to extract the third molar
bud, since its extraction can change the center of
resistance of the second molar and uprighting can be realized
with distal crown tipping. This is undesirable when the
second molar is planned to be uprighted mostly with
mesial root tipping [
Materials and methods
In order to find the appropriate articles to be included
in this systematic review, Medline was electronically
searched via PubMed on January 27, 2017, using the
following search strategy:
(mini implants OR mini-implants OR screw implants
OR miniscrew implants OR mini-screw implants OR
mini screw implants OR microscrew implants OR
micro-screw implants OR micro screw implants OR
microimplants OR micro-implants OR micro implants)
AND (orthodont*) AND ((molar) OR (“preprosthetic”)
OR (upright) OR (upright*) OR (tipped) OR (tipping))
Random searching on Google Scholar and other
databases was also held. All types of human studies
including case reports were selected for inclusion. The
reference lists of each article eligible for inclusion were
also manually reviewed.
In order to methodologically assess the eligible case
reports/series, we implemented a pilot checklist
including several aspects. This checklist consists of 22 items in
total, appropriately classified in seven domains: (1)
patient, (2).treatment providers, (3) diagnostic evaluation,
(4) appliance characteristics, (5) treatment procedure,
(6) validity of results, and (7) conflict of interest. Each
criterion could receive three possible ratings: 0 when the
criterion was not fulfilled, 1 when no clear judgment
could be reached, and 2 when the criterion was certainly
fulfilled, resulting on a maximum score of 44 points per
case. Finally, a judgment of the total quality of the
respective case reports was made, based on the following
interpretations: low quality when the total score was 0–
11, lower medium quality when the total score was 12–
22, upper medium quality when the total score was 23–
33, and high quality when the total score was 34–44.
Initially, 255 citations were found in total. Two hundred
thirty citations were excluded as non-relevant, and 25
articles remained for further evaluation using their
fulltext. Through handsearching, 7 more articles were
added. After excluding 15 non-relevant articles, only 17
papers remained for inclusion and their findings are
reported in this systematic review (Fig. 1).
There are two methods of application of orthodontic
forces when utilizing MIs: (a) using direct anchorage
and (b) using indirect anchorage. Direct anchorage
describes situations where the teeth desired to be moved
are directly pulled or pushed towards or against the MIs.
In contrast, indirect anchorage refers to the stabilization
of certain teeth via a rigid connection with the MI and
subsequent use of these stabilized anchors to move other
teeth in the dental arch.
According to the current literature search, 27 cases
were documented with both direct and indirect force
traction by MIs, although most of them used the direct
method (Table 1).
As far as the quality evaluation is concerned, the mean
score of the included studies was 13.2, indicating a
rather poor methodology implemented in the majority of
the included cases. In detail, 9 cases were judged with
low quality, 15 with lower medium quality, 3 with upper
medium quality while none of the investigated case
reports was found to present high quality (Table 2).
Molar uprighting using MIs with direct anchorage
Molar uprighting using MIs with direct anchorage was
the sole or partial subject of the 15 included papers. One
of these 15 papers [
] describes two cases treated with
direct use of MIs and one case with indirect use, and
this is why it will be discussed again in the following
Regarding the use of direct application of forces on the
MIs for the correction of molars on the sagittal plane, cases
of uprighting all three mandibular molars were found,
which were initially either mesially tilted or impacted. In
order to treat these cases, several options regarding the
insertion sites of the MIs were used: (a) in the retromolar area
2–5, 12, 15, 23, 25
] (Figs. 2 and 3), (b) vertically in the
alveolar ridge of a mesial edentulous molar site [
] (Fig 4),
or (c) mesial to the mandibular molar and between the
roots of the adjacent teeth [
4, 15, 27
] (Fig 5).
The origin of force differed also, as in several cases
uprighting was achieved (a) by using an open or closed
coil spring [
] (Fig 6) or (b) by using buttons and
elastomeric chains [
2, 4, 5, 25, 27
]. In a case of a mesially
Gracco 2007 
Mesially inclined #37
tilted second molar, buttons were placed on its labial,
lingual, and mesial surface, and uprighting force was
applied through three elastic chains, which were connected
to a MI in the retromolar area [
]. A distalizing and
uprighting movement was produced, which avoided
undesirable rotation of the molar [
] (Fig 7). Other
treatment options included uprighting springs [
], a small
], a sequence of archwires and a running
], and a modified version of the Uprighter Jet
called Uprighter Screw [
] (Fig 8).
As regards the direct force application on the MIs for
the correction of molars on the transverse plane, two
cases were reported [
], where there was a lingually
tilted second molar and a lingual crossbite of a second
mandibular molar, respectively. In the first case,
described by Sohn, the MI was inserted in the buccal
Rating was done according to the following: low quality when the total score was 0–11, lower medium quality for scores 12–22, upper medium quality for scores
23–33 and high quality for scores 34–44
alveolar bone and the force was applied through an
elastomeric chain to a buccal button for 3 months .
In the second case, two MIs were placed in both the
mandible and the maxilla in order to treat the crossbite
with elastomeric threads attached to buttons, by
producing a buccal and intrusive force on the lower molar and
a palatal and intrusive force on the upper one,
] (Fig 9).
Direct force application was also used in three cases,
where there was a correction of molars in more than one
planes of space. In the first case report [
], a second
molar was mesially and lingually tipped and was
simultaneously in crossbite with the maxillary molar. In this
specific case, the MI was placed distobuccally in the
retromolar region, and for the following 3 months, an
uprighting force was applied to a lingual button on the
mesiolingual surface of the second mandibular molar,
through an elastomeric thread. In the second case [
after the distal uprighting of a mesially tipped and
obliquely impacted molar via a removable appliance and an
uprighting spring, a MI was inserted buccally between the
roots of the maxillary molars. Force was applied via an
elastic chain placed between the buccal MI and a wire on
the occlusal surface of the mandibular molar in order to
upright the tooth buccally and vertically (Fig 10). The
third case [
] describes the simultaneous uprighting and
intrusion of a lingually tipped and supraerupted lower first
molar. The clinicians used elastomeric chains connecting
a lingual attachment on the molar and a MI placed in the
interradicular region. Buccolingual uprighting of 2.3 mm
and intrusion of 1.8 mm was achieved in 45 days.
Molar uprighting using MIs with indirect anchorage
Two out of the 17 included papers, which reported
only two cases, assessed molar uprighting using MIs
with indirect anchorage. As mentioned above, the
paper of Musilli et al. [
] presents cases treated with
both types of anchorage and will be described again
in the next paragraph.
The first case of a second mandibular molar tilted
on the sagittal plane was presented by Yun et al. [
A MI placed between the second premolar and the
first molar was connected to the tooth by a rigid
stainless steel wire serving as indirect anchorage. In
addition, a peerless single tube was bonded on the
first molar, and a metal button was attached on the
second molar, in order to achieve appropriate traction
with an uprighting spring. In the second case
presented by Musilli [
], two mesially tilted molars (teeth
#37 and #46) were simultaneously uprighted in
9 weeks using a long cantilever on each side. Two
MIs were used indirectly, locking the molars with
steel ligature in order to prevent molar’s extrusion
and distal tipping. Thus, the uprighting is mainly
achieved by mesial root tipping (Fig 11).
Molar uprighting using MIs both with direct and indirect anchorage
Finally, molar uprighting using MIs both with direct
and indirect anchorage was the subject of the one
There was one clinical trial included in the current
review in which 181 MIs were inserted in 102 patients and
were used both as a direct and indirect anchorage for
lower molar uprighting [
]. With regard to the direct
anchorage, 65 MIs were inserted in 31 patients using
two different options. The first option included two
vertically inserted MIs in the edentulous alveolar crest area
and a bracket that was bonded on a resin uniting the
two MIs. A segment of wire from this bracket to the
molar was activated to realize the uprighting. The
second option included the use of a cantilever directly
activated on a MI that was inserted perpendicular
to the buccal surface of the alveolar bone. With
regard to the indirect anchorage, 116 MIs were
inserted in the buccal surface of the alveolar bone
of 71 patients and were connected via a segment of
stainless steel wire with the canine and premolars.
Then, a single or a double cantilever system was
used to upright the molar. According to the
authors, MIs showed high success rates in both
anchorage methods with a slight superiority of the
direct anchorage. Only 18 MIs failed, including 15
that were used as indirect anchorage and 3 that
were used as direct anchorage.
Direct vs. indirect anchorage
According to Lee et al. [
], direct MI for molar
uprighting is simpler, as it requires one MI and a single bracket
or button attachment, minimizing patient’s discomfort
and also reducing chair time compared to more complex
indirect anchorage. Furthermore, direct MI connection
with the target tooth eliminates the possibility of
unwanted movement of the anchorage unit, which can
occur even with indirect MI anchorage as a result of
technical errors. However, direct anchorage has some
limitations and especially in cases of lingually tipped or
rotated molars because a single force may be insufficient
to upright the tooth. Usually, such cases require a
sequential application of different force systems and
repeated changes of appliances. Lee et al. also report that
direct MI application is not indicated in cases of
extruded molars since the force system lacks an intrusive
This systematic review presents evidence from 17
studies that included a total of 27 cases of mandibular molar
uprighting. From these 17 studies, 16 were case reports/
series and only 1 was a clinical trial.
A common point of these studies is that mandibular
molar uprighting is a frequent and complicated
procedure, which requires good anchorage control. Even a
small amount of anchorage loss can result in adverse
effects on other tooth units, extrusion of the molar, or a
compromised outcome. The introduction of MIs as
orthodontic anchorage auxiliaries provided orthodontists
with a very significant tool that will help them among
others to upright molars easier, faster, with less
sideeffects, and less inconvenience for the patient. Moreover,
in patients with many missing teeth or with periodontal
compromised teeth, when conventional full-arch
anchorage cannot be applied, MIs provide a unique treatment
alternative to molar uprighting.
The present review incorporated an innovative
pilotformed checklist in an effort to evaluate the
methodology followed in each of the included case reports/
series. Although the use of the aforementioned tool is
not evidence-based, it seems to provide a brief yet
adequate quality analysis in matters of case reports.
According to the results of the corresponding checklist,
most of the cases examined were judged with rather low
This paper presents a variety of clinical applications of
MIs in mandibular molar uprighting in all three planes
of space, both with direct and indirect anchorage. Due
to numerous advantages, MIs seem to constitute a
reliable solution for treating tipped or impacted molars.
However, since the majority of the included studies were
case reports/series, which were also judged with rather
low quality, the outcomes of the respective studies
should be interpreted with caution and probably cannot
be generalized to the average patient with similar dental
We thank Mr. Vasileios F. Zymperdikas, Resident, Department of
Orthodontics, Faculty of Dentistry, School of Health Sciences, Aristotle
University of Thessaloniki, for his invaluable assistance regarding the quality
assessment of the case reports/series.
MAP was responsible for the topic’s conception, correction of the draft, and
guidance of the flow of the subject matter. PM and GE collected,
interpreted, and analyzed the data; drafted the article; and critically revised
them. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
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