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Conventional Braces and Clear Aligners: An Evaluation of Outcome and Treatment
Ana Kublashvili
Roosevelt High School
I. Introduction
Conventional orthodontic treatment to treat a variety of
malocclusions using wires, brackets, or ligatures has been
around since 1770. Orthodontic materials were first
developed in 1887 by Dr. Edward Angle, who used nickel
alloy for its flexibility in wires. Different materials like
copper, zinc, and 14-karat gold became more prominent
and widely used for traditional orthodontic treatment.
Stainless steel was introduced in 1929 and it gained
popularity for its fracture resistant property under stress,
and less costly than gold(1). In 1944, removable
appliances started being used for mild and moderate tooth
movements. Development of new research and technology
in the late 20th and early 21st century brought CAD/CAM
manufacturing, which has allowed the development of
plastic orthodontics including Invisalign. ALIGN
technologies, the proprietary company of Invisalign, was
founded in 1997 and the FDA approval for Invisalign was
presented in 1999(2).
There are many options of clear aligners available
currently. Invisalign is the most popular clear aligner
company and is unique due to their Smart track polymer
system. This multi-layered polymer system replaces
traditional aligner materials with a more elastic material,
enhancing fit, comfort, efficiency. Invisalign aims to speed
up tooth movement by 50% and increase precision by 75%
compared to other materials(3). Furthermore, Invisalign
also claims to resolve rotations of 40 degrees in upper and
lower central incisors, 45 degrees in canines and
premolars, 30 degrees in lateral incisors, and 20 degrees in
molars. SureSmile, another aligner brand, uses Essix ACE
Plastic, a thinner, singled layered material (4). SureSmile
has shown studies that illustrate a reduced treatment time
than the traditional, wire approach with improved quality.
Another aligner brand is ClearCorrect, made out of a tri-
layer material, two layers of polymers with an elastomeric
inner layer. ClearCorrect aligners have shown force
retention overtime, have kept its shape throughout the
wear, and have exhibited durability and demonstrated 4x
better tear resistance than single layer polymers(5).
Traditional orthodontic treatment usually consists
of NiTi (nickel titanium) and Stainless steel wires.
Stainless steel alloys offer resistance to corrosion, greater
rigidity, and reduced friction. Stainless steel alloys also
come in multi-stranded variations, which exhibit lower
rigidity that allows them to be used in the early stages of
treatment. NiTi alloys differ from stainless steel in their
flexibility and shape memory, which allows them to revert
to their original shape even with significant force(6).
Thermodynamic NiTi alloys become activated under a
certain temperature so it becomes easier to insert NiTi
wires into bracket slots during application. Many
activations under a specific temperature provide different
advantages. For example, alloys activated under 27°C
exert greater loads, working well in the oral cavity, where
the temperature is around 36-37°C. Wires activated at
40°C are well-fit for patients with high sensitivity, as the
wires undergo minimal activation during warm salt water
mouth rinses(7).
Braces and clear aligners, both effective in orthodontic
treatment, use different approaches to get desired
outcomes.Orthodontic treatment seeks to correct
malocclusions or bite problems. There are 2 common types
of malocclusion, overbite and underbite. Overbite is a
clinical condition where the maxillary teeth are angled
forward covering the mandibular teeth(8). In an underbite,
the mandible is extended out covering the tip of the
maxillary teeth(9). Intrusion and extrusion are additional
malocclusion issues that can be present. Intrusion refers to
the downward movement of the tooth into the alveolar
bone, and extrusion displacement of a tooth out of its
alveolar housing(10). Additionally, there are 3 different
types of malocclusion classes. Class 1 is crowding around
2
or spacing issues around the teeth. Class 2 is an overbite
when the maxillary front teeth are positioned too forward
protruding over the lower incisors. Class 3 is an underbite
where the lower front teeth are positioned in front of the
top front teeth(11). Figure 1 below demonstrates the three
malocclusion classes discussed above. Overall gingival
health is a big reason why orthodontic treatment is needed,
as gingivitis and periodontal disease are common in
patients before getting treatment (12) . In extreme cases
orthognathic jaw surgery is needed for malocclusions,
facial asymmetry, and problems with jaw growth(13).
.
.
Figure 1- Illustration of class I, class II, and class III malocclusions. In
Class II, maxillary teeth are positioned more anteriorly in comparison to
mandibular teeth. In Class III, maxillary teeth are positioned more
posteriorly in comparison to mandibular teeth.
During orthodontic movement the body goes through
biological changes. During the initial phase, the teeth
begin to shift, affecting the tissue around it and forcing the
periodontal ligament surrounding the tooth to stretch and
compress, which causes the blood vessels to leak, attract
inflammatory cells, and recruit cells that help with bone
remodeling(14). Throughout this process, gingival
inflammation is present because of plaque build-up as
wearing orthodontic devices makes it difficult to clean,
especially in interproximal spaces. (15). Additionally, the
dental pulp is affected during orthodontic treatment as
pulpal tissue sits in hard tooth structure that is dependent
on blood vessels passing through, any problem with blood
flow and tissue pressure can affect dental pulp (16). As a
result of orthodontic force, the periodontal ligament is
affected as it undergoes a remodel with the breakdown of
bone on the compressed side and the buildup of bone on
the tension side (17). The metabolic state of the bone is
influenced during orthodontic treatment, as bone turnover
affects the rate of tooth movement(18).
II. Materials/Methods
This systematic review focused on the following question:
In young adults in need of orthodontic treatment, which
orthodontic appliance, traditional braces or clear aligners,
will have the best outcome and treatment in the most
effective way possible?
The definitions of population, intervention, comparison,
and outcome (PICOs) were developed based on the
focused question as follows:
Population: Young adults needing orthodontic treatment
Intervention: Traditional braces
Comparison: Clear aligners
Outcomes: Best outcome in the most effective way
possible
Search strategies
An electronic search without time or language restrictions
was conducted using Pubmed, Google Scholar, and other
published articles. The reference lists of included studies
and relevant reviews were also searched for other potential
studies. The detailed search strategies were as follows:
Orthodontics AND wires, wires AND brackets, clear
aligners AND braces, Invisalign AND efficiency,
periodontal status AND aligners, braces AND force, cost
WITH clear aligners, oral hygiene AND traditional braces,
mechanism AND clear aligners, ‘Quality of life’ with
braces AND aligners, treatment AND braces,
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III. Discussion
Orthodontic treatments, including clear aligners and braces
use distinct mechanisms to straighten teeth. A major
difference in mechanism between clear aligners and
traditional wire is the force, elasticity, and angulation used.
The force used with traditional orthodontic wire and clear
aligners differs significantly. Clear aligners have two
different systems, the displacement driven system and the
force-driven system, as shown in figure 2. The
displacement driven system is a method orthodontics uses
to create a custom set of aligners to apply gentle pressure
and shift the teeth overtime. The system guides simple
movements of the teeth such as minor rotations or tipping.
The system is less effective in complex movements and
root adjustments. The force-driven system designs the
aligners so they are able to apply force in targeted areas. In
certain cases, the aligners will be altered with pressure
points for more difficult tooth movements, such as
intrusion and uprighting. In some cases, power ridges,
which are strategically placed bumps on the aligner to
exert precise forces on specific teeth will be used to
control root torque and to get desired force on the specific
area (19) (20). Additionally, the force and magnitude is
determined on the configuration of the aligners, with each
tooth receiving a certain magnitude and a type of force.
Aligners designed with specific intrusion patterns show
force exerted on different types of teeth such as, incisors,
canines, and premolars. This variety of force application is
helpful in correcting deep bite issues, as it affects how
effectively aligners achieve the desired outcome for the
teeth. Most aligners are made from a polyurethane plastic
material which severely influences their mechanical
properties and force distribution(21). Comparing elasticity,
clear aligner materials have viscoelastic properties which
have viscous and elastic materials. Invisalign uses a
polymer called SmartTrack, which gives the aligners
elasticity and produces constant forces which improves
overall efficiency.
Figure 2: An illustration describing clear aligner force systems, the force
driven system and displacement-driven system. The displacement driven
system relies on physically moving teeth into new positions. The force
driven system uses precise forces to move teeth in the desired position.
Orthodontic wires such as Nickel-Titanium and
Stainless steel exert a great amount of force once applied.
Friction is very influential on the force applied because it
can determine the amount of force the wires exert. For
example, stainless steel wires have lower friction rates
which allows greater force to be released. Additionally, the
low friction rates for stainless steel wires allows them to be
less resistant to tooth movement compared to other
alloys(22). Orthodontic treatment utilizes NiTi wires to
achieve optimal results, considering factors like the degree
of deflection, ligation techniques, and frictional forces to
ensure the most effective force application for desired
outcomes(21). A study done by Garner et al (22) observed
that frictional forces between brackets and wires are
greater with NiTi wires compared to stainless steel wires,
but lower than those with beta-titanium wires, especially in
zero torque or angulated brackets. Orthodontic wires like
Niti and stainless steel have lower stiffness, making them
flexible and more elastic. Due to the high yield strength
and elasticity of stainless steel, stresses can severely
impact the wire's elastic properties after bending.
Therefore, heat treatment is used to relieve stress in
stainless steel wires bent into arches, loops, or coils,
thereby enhancing their elasticity. In NiTi the most
beneficial characteristics are its springback and flexibility.
NiTi’s high springback is used in cases that need low
forces but large elastic deflections. Also, it is commonly
observed that NiTi wires exhibit more pronounced
springback and higher revocable energy compared to
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stainless steel or beta-titanium wires(22). Zirconia brackets
are a type of orthodontic bracket made from zirconium
oxide and gained its popularity because of its durability
and appearance. They are mainly used when strong
movements are needed but patients would like a more
aesthetic treatment option. Zirconia brackets are highly
resistant to staining and discoloration, making them a good
option for patients who want them to be more discreet.
They also exhibit superior mechanical properties such as
higher fracture toughness and better performance under
stress compared to ceramic brackets. Although, one of the
challenges with zirconia brackets is their higher friction
with orthodontic wires which can affect the efficiency of
tooth movement(41).
During orthodontic treatment, the quality of life
and pain throughout is a key factor orthodontists need to
look for. For patients who need orthognathic surgery,
studies show that clear aligners have a better quality of life
outcome, and lower amount of pain after surgery than
traditional braces. In the study by Patricia de Leyva (23),
2023, patients with dental deformities who underwent
orthognathic surgery randomly received post-orthodontic
treatment of either traditional braces or clear aligners.
Quality of life was assessed through the Orthognathic
Quality of Life Questionnaire and the Oral Health Impact
Profile (23). Additionally, another study by Paula
Coutinho Cardoso had a group of patients use invisalign
and traditional braces(24). This study agrees with the most
recent studies showing a greater incidence of pain when
fixed appliances are used.
A key factor in orthodontics is the time the
treatment takes to get the desired outcome. In many cases,
aligners were effective in rapid orthodontic treatment.
Rapid orthodontic treatment is an accelerated approach to
straighten teeth and fix misalignments. A study by Dr.
Edmund Khoo (25) shows a case of 3 patients who got
micro-osteoperforation (MOPs) done, a technique to
accelerate ortho movement. MOPs are created with tiny
openings in the alveolar bone requiring movement
typically under local anesthesia, without the necessity of
lifting a tissue flap. These patients were treated with
Invisalign. All three patients were satisfied with the
outcome and stated that there was very little pain and felt
mild gingival inflammation a day after the procedure(25).
Three clinical studies showed that PAOO resulted in faster
leveling and alignment compared to traditional orthodontic
treatment, with accelerated percentages of 39%(246 days
versus 402), 46% (171.9 versus 314 days), and 47% (74.5
versus 141.7 days) respectively for each study.
Furthermore, two investigations demonstrated that PAOO
accelerated the retraction of upper interior teeth, with
acceleration rates of 44% (156 versus 441 days) and 61%
(130.5 versus 234.1 days) (26) respectively. To achieve the
desired outcome, it is very important to know which
treatment with time efficiency is better. In cases not
requiring rapid orthodontic movement, similar results are
found in terms of timing for case completion. A study by
Buschanga et al showed that during traditional treatment
aligners took 11.5 months to achieve desired outcome
while traditional braces took 17 months to fix
malocclusions in the teeth (27). The factors included chair
time, doctor time, and overall patient compliance. The time
for the clear aligners was most likely shorter as it does not
need a detailing or finishing phase, while traditional braces
take up to 6 months for it. However, the American Board
of Orthodontics objective grading system showed that the
aligners did not correct malocclusions as well as braces
did. During orthodontic treatment it is very common
for overall oral hygiene to be affected. In clear aligners
compared with traditional braces, clear aligners facilitate
better oral hygiene which improves periodontal status,
decreases bleeding on probing and gingival
inflammation(19). Traditional braces make it harder to
clean those hard to reach spaces causing more problem
areas(28). Clear aligners are significantly better at
improving gingiva health, and more specifically
periodontal disease, as patients have a greater ability to
clean their teeth when the appliance is removed. However,
traditional braces affect plaque removal, gingival heath,
and makes gingivitis more prominent. The bands, elastics,
brackets and wires in traditional orthodontic treatment
carry bacteria which can then cause periodontal disease.
5
Studies have shown it is best to perform orthodontic
movement after active periodontal disease has been
treated. Orthodontic movement can enhance bacteria and
cause periodontal inflammation. In clear aligners, caries
can be affected as well. The biomaterials in clear aligners
can result in a growth of bacteria associated with caries
and the emergence. In traditional braces as stated before
braces make it harder to clean the teeth, which causes
caries to become more prominent from the bacteria in the
mouth. White spot lesions are common to show up during
orthodontic treatment in both clear aligners and traditional
braces. Again comparing the two, many cases show that
patients who have traditional braces get white spot lesions
because fixed appliances promote bacteria, plaque build up
and limit the ability to clean the teeth. Compared to
aligners they have a much better success rate with white
spot lesions, since they are more accessible to clean and
bacterial plaque doesn't get missed while brushing. A study
by de Leyva et al (23) compared bleeding on probing and
probing depth. Clear aligners had significantly lower
probing depth compared to traditional braces, and
comparing bleeding on probing clear aligners only had 1
where traditional braces had 8 (23). Another study by Luca
Levrini et al (28) compares bleeding on probing between
clear aligners and traditional braces, which concluded that
clear aligners had less bleeding on probing compared the
fixed appliances(28).
After orthodontic treatment, patients with
malocclusions treated with aligners showed significantly
better results in treating the malocclusions compared to
traditional braces. However, in a 6-month post-treatment
period for aligners, more relapse was shown compared to
traditional braces. Data gathered by Kaklamanos et al (29)
showed that aligners for treatment may offer further
advantages to the improved Oral Health-Related Quality of
Life (OHRQoL) seen with orthodontic correction,
compared to traditional treatment using conventional metal
fixed appliances. These advantages could include
enhanced comfort during sleep, eating, and social
interactions, as well as increased self-esteem and overall
satisfaction with oral health(29).Another study was done
by Qiuying Li et al, yielding similar results on the Qol of
braces and aligners(30). A study done by Di Spirito et al
(31) showed after a 6 month period, clear aligners had a
better periodontal status compared to traditional
braces(31). Studies about rebound percentage of clear
aligners and traditional braces are very limited. However, a
study done by Papadimitriou et al,(32) shows how teeth
alignment with clear aligners deteriorate quicker than with
braces.This implies that the rebound rate would be higher
in aligners than in braces(32).
The total material cost for clear aligners is calculated
differently. The price range for aligner systems in the
United States range from $2,650 and $7,000. More
specifically, in Invisalign, the cost varies depending on
how long the treatment will be. If the patient's treatment
plan is 6-12 months, the average cost would be $2,650 –
$6,000 (33). Traditional braces on the other hand are
calculated with more specifics. For example, a big part in
the cost is what type of braces the patient needs, traditional
metal braces average cost is $3000-$5000, for ceramic
braces average cost is $4000-$7000, and for lingual braces
the average cost is $5000-$8000. In addition, home care
throughout orthodontic treatment is essential to the success
of treatment. In this study by Peter H. Buschang et al (27),
he compared the time efficiency of aligners and braces.
Aligners had 14 total appointments while braces had 19
(27). In the same study, the aligners group averaged one
emergency visit while traditional braces averaged 3.5. In
another study traditional braces took more chair time
compared to aligners. And keeping in mind during this
chair time the material costs also increase. On the other
hand, total doctor time was more in aligners than
traditional braces. As 25% of doctor time was over 33
minutes while traditional braces had 26 minutes. After
finishing treatment, the corrections in the teeth were the
patients who had aligners(19). Post Treatment after 3 years
show how the alignment of teeth were worsening in the
patients with clear aligner treatment compared to
traditional braces(34).
IV. Conclusion
6
Clear aligners and traditional braces yield many
differences in outcomes. In orthognathic surgery clear
aligners demonstrated superior quality of life (Qol)
outcome and reduced pain levels compared to braces(23).
Regarding time efficiency, clear aligners had quicker
results than braces, although after post treatment the
alignment of teeth tended to deteriorate in patients who
underwent clear aligner treatment (27)(34). In overall
hygiene clear aligners had better outcomes with
periodontal status, bleeding on probing, and
inflammation(19). Traditional braces also promoted white
lesions during treatment(23). In treating malocclusions
clear aligners tend to yield better results than braces(29).
Periodontal status was achieved in both braces and clear
aligners, but clear aligners yielded better results. Caries
were more prominent in traditional braces compared to
clear aligners. Both braces and clear aligners offer
effective solutions for orthodontic treatment, although
clear aligners have several advantages. Clear aligners
provide greater comfort, are less visible and are easier to
maintain. Additionally, they result in quicker treatment
times with better periodontal status compared to traditional
braces. Also complying with patients' satisfied outcome.
Therefore, those seeking a convenient and aesthetic
orthodontic solution, clear aligners are the preferable
choice. A new method for making clear aligners by 3D
printing them offers many benefits.3D printing allows for
highly precise aligners, better fit, higher efficacy, and
reproducibility.The process includes high-process 3D
models creating aligners with a smooth surface finish,
which is important for transparency and patient comfort.
Companies like Modern Clear utilize advanced 3d printing
technology to maintain quality and consistency. To add on,
the ability to control the thickness and design of aligners
allow for more customized treatment plans, which leads to
better orthodontic outcomes(35). A study by Gianluca M.
Tartaglia et al shows that 3D printed aligners offer superior
accuracy, load resistance, and reduced deformation
compared to traditional thermoformed aligners(37). A
study by James Grant et al measures the amount of force
and movement with 3D printed aligners(38). The study
proposes one of the key benefits of 3D printed aligners is
increased precision in manufacturing, allowing for better
predictability of movement. Also, agrees with the previous
study that 3D printed aligners achieved greater accuracy
and load resistance(37). Despite the advantages of 3D
printing aligners, there is not enough technical and clinical
data regarding these aligners(38).
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