Indications, limitations, and outcomes of clear aligners in orthodontic treatment

Abstract

Clear aligners have gained popularity in orthodontic treatment as a comfortable and aesthetically pleasing alternative to traditional braces. The use of clear aligners has increased due to their advantages, including improved aesthetics, easy removability, and minimal soft tissue irritation. The treatment process involves sequential aligners custom-made for each patient, using computer-aided design and manufacturing technology. Clear aligners employ controlled forces to gradually move teeth into proper alignment. However, clear aligners have limitations, such as the need for patient compliance and their effectiveness in addressing complex malocclusions. Clinical considerations include thorough assessment, regular follow-up visits, and patient education. Treatment outcomes vary depending on the specific malocclusion characteristics. Clear aligners have demonstrated benefits in treating mild malocclusions, spacing issues, and certain types of malocclusion corrections. Treatment duration may be shorter compared to fixed appliances in mild cases. Stability and periodontal health can be influenced by clear aligner therapy, which has effects on plaque levels and gingival inflammation. Root resorption is a concern, but aligners have shown a lower prevalence compared to fixed appliances. Compliance, eruption of permanent teeth, and limitations in visualizing hard and soft tissues are important considerations. Overall, clear aligners offer an aesthetic orthodontic treatment option for a variety of dental abnormalities and mild to moderate orthodontic issues.

Full text

International Journal of Community Medicine and Public Health | July 2023 | Vol 10 | Issue 7 Page 1
International Journal of Community Medicine and Public Health
Alangary MA et al. Int J Community Med Public Health. 2023 Jul;10(7):xxx-xxx
http://www.ijcmph.com
pISSN 2394-6032 | eISSN 2394-6040
Review Article
Indications, limitations, and outcomes of clear aligners
in orthodontic treatment
Mohammed Abdullah Alangary*, Adel Nedal Radwan, Mohammed Omar Alshehri,
Anwar Hassan Alzahrani, Ahmed Tarik Himdi, Mohammad Ahmad Alturkestani,
Mohammad Musallam Alsaedi, Mohunned Abdulkareem Alghamdi, Zyad Ahmed Hassanein
INTRODUCTION
The study of orthodontics focuses on the identification,
avoidance, and treatment of dental problems like
misaligned teeth, misaligned jaws, and problems with the
mastication process. Because thermoformed splints are
more comfortable and aesthetically pleasing than
conventional fixed orthodontic equipment, the use of
aligner therapy has increased in recent years. The term
"clear aligner therapy" (CAT) covers a broad range of
dental appliances with varying mechanisms of action,
building techniques, and suitability for different
malocclusion therapies. At the end of the 1990s, the
company align technology (Santa Clara, CA, USA)
developed the Invisalign® system, and clear aligners first
became popular there. Starting in 2001, they spread to
Italy and other European nations.1 Since then, there has
been an exponential rise in interest in and adoption of this
therapeutic alternative to conventional multibracket
orthodontic therapy, taking into account the demands and
aesthetic preferences of orthodontic patients. 2-4 Nearly 20
years later, there are numerous brands of aligners
available commercially throughout the world (nearly 20
just in Italy), and their prescriptions, applications, and
fundamental characteristics have changed.6,7 The
materials used to produce the aligners on the market
nowadays vary in terms of thickness and construction.
ABSTRACT
Clear aligners have gained popularity in orthodontic treatment as a comfortable and aesthetically pleasing alternative
to traditional braces. The use of clear aligners has increased due to their advantages, including improved aesthetics,
easy removability, and minimal soft tissue irritation. The treatment process involves sequential aligners custom-made
for each patient, using computer-aided design and manufacturing technology. Clear aligners employ controlled forces
to gradually move teeth into proper alignment. However, clear aligners have limitations, such as the need for patient
compliance and their effectiveness in addressing complex malocclusions. Clinical considerations include thorough
assessment, regular follow-up visits, and patient education. Treatment outcomes vary depending on the specific
malocclusion characteristics. Clear aligners have demonstrated benefits in treating mild malocclusions, spacing
issues, and certain types of malocclusion corrections. Treatment duration may be shorter compared to fixed
appliances in mild cases. Stability and periodontal health can be influenced by clear aligner therapy, which has effects
on plaque levels and gingival inflammation. Root resorption is a concern, but aligners have shown a lower prevalence
compared to fixed appliances. Compliance, eruption of permanent teeth, and limitations in visualizing hard and soft
tissues are important considerations. Overall, clear aligners offer an aesthetic orthodontic treatment option for a
variety of dental abnormalities and mild to moderate orthodontic issues.
Keywords: Orthodontics, Orthodontic treatment, Cosmetic, Clear aligners
Department of Dental, King Abdulaziz University Dental Hospital, Jeddah, Saudi Arabia
Received: 28 May 2023
Accepted: 13 June 2023
*Correspondence:
Dr. Mohammed Abdullah Alangary,
E-mail: md.angary@gmail.com
Copyright: © the author(s), publisher and licensee Medip Academy. This is an open-access article distributed under
the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial
use, distribution, and reproduction in any medium, provided the original work is properly cited.
DOI: https://dx.doi.org/10.18203/2394-6040.ijcmph20231793

Alangary MA et al. Int J Community Med Public Health. 2023 Jul;10(7):xxx-xxx
International Journal of Community Medicine and Public Health | July 2023 | Vol 10 | Issue 7 Page 2
Clear aligners have developed into a key aesthetic
alternative in orthodontic treatment as a result of the
rising demand for orthodontic treatment among adult
patients. While many varieties use clear thermoformed
plastic aligners to cover some or all of the teeth, there are
other important and substantial distinctions that affect
each kind of aligner’s capacity to handle a variety of
orthodontic issues.8 The purpose of this review article is
to discuss the benefits, drawbacks, and results of using
clear aligners in orthodontics.
LITERATURE RESEARCH
The database used the medical subject headings (MeSH)
and a combination of all related titles to do a review
article search on May 15, 2023, in the PubMed, Medline,
and Cochrane databases as well as the Wiley online
library. The reference lists of the previously mentioned
studies were used as a starting point for a manual search
for publications through Google Scholar in order to avoid
missing any different studies. In studies that explored the
uses, restrictions, and results of clear aligners in
orthodontics, we looked for useful information, date,
participant age, language, and publication kind were all
free.
DISCUSSION
Most patients can benefit from using clear aligners, which
have been indicated to be successful. On the basis of the
most recent evaluation, this critical appraisal, however,
advises that transparent aligners should only be used in
certain situations.
Indications
Treatment options include lateral and/or antero-posterior
expansion, minimal interproximal tooth reduction, or
extraction of a lower incisor for issues with slightly
crowded and misaligned areas (1-5 mm).9 Additionally,
clear aligners can be used to correct spacing issues (1-5
mm). The overbite can be treated by incisor intrusion and
advancement in cases of class II, division 2 malocclusions
accompanied by a deep bite. Clear aligners may also be
used for the treatment of narrow arches that can be
expanded without tilting the teeth. Clear aligners can also
be used to address cases of relapse following fixed
orthodontic treatment, small rotations, flaring,
distalization, and closure of space after the extraction of a
lower incisor.9
Factors consideration
Success with Invisalign therapy depends heavily on
patient compliance. At least 20 hours per day should be
spent wearing the aligners.10 Successful clear aligner
therapy necessitates extensive clinical knowledge of
various orthodontic techniques, accurate diagnosis and
treatment planning, and a solid understanding of
biomechanics. In any event, fixed appliances will likely
be required to straighten the teeth if they tip more than 5
degrees during space closure. If the tipping is greater than
10 degrees, the dentist should either use full fixed
appliances to complete the therapy or add a fixed
appliance section to straighten the tipping teeth. Nelson
recently listed a number of aligner software benefits that
were distilled from a meeting. The set-up can be used for
diagnosis and treatment planning, evaluating the need for
IPR, expansion, extraction, distalisation, or proclination,
as well as verifying that the technician has performed
modifications, using a consultation device to show
treatment limits to the patient, verifying that the aligner is
tracking, evaluating anchorage with the superimposition
or surgical simulation tools and staging, addressing the
patient’s chief concern (anterior tooth alignment) at the
beginning of the series, and applying simultaneous
movements to reduce the overall number of aligners.10
Treatment outcomes
Individual malocclusion characteristics and overall
combined malocclusion correction can be taken into
account when evaluating treatment outcomes. The
evidence had a moderate risk of bias when it came to
certain malocclusion traits. The anterior crowding is
corrected using aligners. In non-extraction circumstances,
they are successful in achieving tipping movements.11-13
According to several studies, aligners are less predictable
and effective at controlling physiological tooth
movement, especially at extraction sites.14-18 Aligner
therapy appears to achieve efficient (2.25 mm) maxillary
molar distalization, without significant molar tipping or
extrusion, with minimal impact on vertical skeletal
relations.18,19 Aligners do not appear to be clinically
effective in their rotational correction and demonstrate
low predictability of response for canines and premolars
(39%), while incisors achieve a better response rate
(60%).18 Strategies that have been suggested to improve
the rotational efficiency of aligners include the use of
attachments (>15°), interproximal reduction, and
reducing the aligner staging to 1.5° per aligner.14 Aligners
do not appear to be clinically effective in achieving
maxillary incisor extrusion and should therefore be
avoided in anterior open bite correction, where this is
deemed to be the treatment mechanic of choice. In
contrast, aligners appear to be equally effective at
achieving mild degrees of maxillary incisor intrusion as
continuous fixed arch mechanics.20 Aligners could be an
effective tool for producing arch expansion, being more
effective in the premolar region and less effective in the
canine and second molar areas. Predictability appears to
be reasonable for expansive movement.21 With respect to
open bite correction, a recent study compared fixed
appliances and clear aligner therapy in correcting the
anterior open bite and controlling the vertical dimension
in adult patients with hyperdivergent skeletal patterns.22
The authors reported that anterior open bite correction
and changes in the mandibular plane angle, associated
with the use of clear aligners and fixed appliances, did not
demonstrate any statistically significant differences in

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adult hyperdivergent patients. In terms of overall
malocclusion correction, the present evidence base would
lead us to recommend that, when compared to fixed
appliance therapy, aligners perform equally well in mild,
non-extraction cases.17 However, they should be used
with greater care in the treatment of more difficult
malocclusions, requiring extraction therapy, due to their
reported inherent difficulties in achieving torque control,
optimal root approximation, and contact point
relations.14,16 The evidence base for these
recommendations is at low to moderate risk of bias.
Treatment duration
The available evidence would lead us to suggest that in
terms of optimal treatment duration for mild
malocclusions, treated on a non-extraction basis, aligner
therapy results in clinically significant shorter treatment
duration (range: 3-6 months) compared to conventional
fixed appliance treatment and could be the appliance of
choice.8 The evidence base for this recommendation is at
moderate risk of bias. For more severe malocclusions,
particularly those requiring premolar extractions,
conventional fixed appliance therapy results in shorter
treatment durations and would be the system of choice.15
The evidence base for this recommendation is at low risk
of bias.
Chair-side clinical time
There is moderate quality evidence to suggest that aligner
therapy is more clinically time efficient as a result of
fewer follow-up appointments, less emergency
appointment time (7 min), and less chair-side adjustment
time (93.4 min).8
Post orthodontic treatment stability of clear aligners
Stability is one of the key topics to go over with clear
aligners, as it is with all types of orthodontic treatment.23
One study used the objective grading system of the
American board of orthodontics to analyse the post-
retention stability outcomes of cases treated with clear
aligners and fixed orthodontic appliances. There were no
fixed retainers employed; only detachable thermoplastic
retainers were used for retention. Both groups' overall
alignment relapsed three years following the retention
period, although the maxillary anterior levelling in the
fixed appliance group seemed stable whereas it relapsed
in the Invisalign group.23
Limitations for the study can be as follows-
Effects of clear aligners on periodontal status and oral
health
As more individuals started utilising transparent aligners,
the research found that this treatment had detrimental
periodontal effects.24,25 The use of clear aligners also
enhances periodontal health by decreasing plaque levels,
gingival inflammation, bleeding upon probing, and
pocket depth.24,26 Fixed equipment and wires make it
difficult to control plaque and have harmful effects on
periodontal tissues, making orthodontic therapy a risk
factor for periodontal diseases.27 However, Han et al
study discovered that with careful oral hygiene education
and consistent plaque management, patients treated with
fixed equipment and transparent aligners both
demonstrated equivalent gingival and plaque indices.24
Root resorption and clear aligners
One of the main issues with orthodontic treatment is root
resorption, which is known to be exacerbated by fixed
appliances by applying too much pressure at the apical
level, which can lead to external apical root
resorption.28,29 Nevertheless, only a few studies have
examined the impact of thermoplastic aligners on root
resorption. Aligners may potentially result in root
resorption at the conclusion of orthodontic therapy,
according to a thorough analysis from 2017 that could
only include three studies.30 The prevalence and severity
are lessened, nonetheless, when compared to stationary
equipment. According to a different study.6 The
frequency of root resorption brought on by aligners is
comparable to that brought on by mild orthodontic
pressure. This situation is explained by the root structure
and the great extent of movement shown by the incisors.30
The fact that existing clinical studies are based on data
obtained from various time periods and thus combine
treatments carried out in accordance with various aligner
protocols or are based on outdated protocols may be a
potential limitation of the current investigation.
Compliance is the most important.10 The orthodontist
must depend on the patient's drive and reliability to get
the desired outcomes because the aligners are not fixed.
Prior to employing this appliance for treatment, all
permanent teeth must be fully erupted. Basal orthopaedic
change cannot yet be incorporated through this appliance
system. Major restorative work should be finished before
treatment begins since it is impossible to change the
surface architecture of the teeth during therapy because
doing so will affect how well the aligners fit. Lastly, it is
not possible for the dentist to accurately determine how
the teeth relate to the basal bone, the lips, or other soft
tissues of the head using Invisalign scanning, as it is
unable to visualize the hard and soft tissues of the skull.
CONCLUSION
For many people who desire to straighten their teeth and
enhance their bite, clear aligners are a common and
popular orthodontic treatment choice. They can straighten
teeth without the agony and inconvenience of
conventional braces because they are practically
undetectable and detachable. A variety of dental
abnormalities, such as crowding, spacing, over- or
underbite, cross-bite, open bite, and mild to moderate
orthodontic issues, can be treated using clear aligners.

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International Journal of Community Medicine and Public Health | July 2023 | Vol 10 | Issue 7 Page 4
Funding: No funding sources
Conflict of interest: None declared
Ethical approval: Not required
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Cite this article as: Alangary MA, Radwan AN,
Alshehri MO, Alzahrani AH, Himdi AT, Alturkestani
MA et al. Indications, limitations, and outcomes of
clear aligners in orthodontic treatment. Int J
Community Med Public Health 2023;10:xxx-xx.