September 06, 2021

What is the best method of correcting increased overbite: Turbos or arch wires?

We use several methods to correct increased overbites. The most common practice is using archwires. However, recently bite turbos have become popular. These investigators did an excellent trial to look at the effectiveness of archwires and bite turbos in correcting increased overbites.

When we consider methods of overbite correction, it appears that the most likely tooth movement is extrusion of the mandibular premolars and molars with a small degree of lower incisor intrusion.  Although, it is usual to have some degree of lower incisor proclination.  This new study looked carefully at these tooth movements.

A team from Irbid, Jordan, did the study. The Angle Orthodontist published the paper. As usual, for the Angle, the article is open access.

A comparative study between the effect of reverse curve of Spee archwires and anterior bite turbos in the treatment of deep overbite cases: A randomised clinical trial

Ekram M. Al-Zoubi and Kazem Al-Nimri. Angle Orthodontist DOI: 10.2319/020921-117.1

What did they ask?

They did the study to:

“Compare the effects of 16×22 NiTi wires and anterior bite turbos in treatment increased overbites”.

What did they do?

The authors did a two-arm parallel-sided RCT with a 1:1 allocation.  They did the study at one site at a dental school.  The PICO was:

Participants: Orthodontic patients with an increased overbite (more than half of the lower incisors) treated non-extraction.

Intervention: Fixed metal anterior bite turbos bonded to the middle of the palatal surface of the upper incisors.

Comparator: Lower 016×022 NiTi archwires that they cinched back distal to the lower second molars.

Outcomes: A lot of cephalometric measurements. The primary outcomes were the AP and vertical changes of the lower teeth.  The cephalograms were taken at the post alignment and post-levelling stage of treatment.

The sample size calculation showed that they needed to enrol 48 participants in the study.  They used pre-prepared randomisation using blocks and concealed the allocation using sealed envelopes.  It was not possible to blind the clinician or patient during treatment. However, they recorded the data blind.  Finally, they used simple univariate statistics to measure any differences between the interventions.

What did they find?

The authors enrolled 48 participants into the study. Notably, they excluded six patients; this was because they corrected the overbite during the alignment stage.

There was no difference between the groups at the start of treatment.

The mean overbite change for the archwire group was 4.07 mm (SD=0.69), and for the turbos group, this was 3.87 (SD=0.72).  This difference was not clinically or statistically significant.

When they looked at the tooth movements, it appears that in the archwire group, there was greater lower incisor proclination than in the turbo group (mean difference 0.69mm).  There was also more lower molar extrusion in the turbo group than in the archwire group (mean difference 1.04mm).  Nevertheless, I found it challenging to interpret the details of their cephalometric measurements. However, this may also reflect my difficulty in understanding most cephalometric analyses.

When they looked at the time taken to reduce the overbite, the authors found that for the turbo group, this was 4.85 months (SD=1.56) and 3.15 months (SD=0.93) for the archwire group. This amount was statistically and clinically significant.

Their overall conclusion was

“Archwires result in lower incisor proclination with distal tipping of the lower molars, while bite turbos result in lower posterior tooth extrusion”.

What did I think?

Firstly, I thought it was great to see that they did this study as part of a Master’s project. This was an outstanding achievement, and I would like to congratulate the team.

I thought that they did this study nicely.  However, as with all trials, we need to look at it closely as part of critical appraisal.  I had the following concerns that we need to consider when we look at the findings.  These were:

The investigators only looked at the effect of a NiTi wire on overbite depression.  I would have liked to see the impact of stainless steel wires with a reverse curve.  This impression may be subjective, but I always felt that overbites reduced well in SS wires. This method would be accepted treatment mechanics.

The operator was not blinded. This issue is important in this study because it appears that the operator decided on when the OB was corrected.  This step means that the investigation is at high risk of bias.

While the investigators found a reduction in the duration of OB depression treatment, it would have been far more relevant to see if the interventions had any effect on total treatment time.  Furthermore, we also need to consider that any impact on tooth position at the end of OB depression are likely to be modified by the mechanics that they used to complete treatment.

Final comments

Suppose I consider these potential shortcomings. My feeling is that this study does add to our knowledge, to a degree. The findings are undoubtedly logical, and they tend to reinforce our understanding.  However, I am not sure that the results of this paper would persuade me to change my practice.  This paper is, perhaps, an example of a study that shows us that everything works in orthodontics?

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Have your say!

  1. A very good article to know about bite correction. Any way molar extrusion is better than lower incisors tipping forward..

  2. Yes. especially great work at Masters level! Well done.

  3. I like to use Bite Turbos early in treatment because it lets me bond the lower arch without the upper incisors biting the brackets. If I’m using archwires…I might not be able to bond the lower on day 1 and it’ll take me a few visits to get to the archwire that will actually reduce an overbite. I’ve no idea how the overbite was meant to reduce with a 016×022 niti – was it made with a reverse curve or was it just levelling an increased curve of spee in the arch? Does anyone else use this wire for this purpose?

    It doesn’t say if the Turbo group had archwires as well – I don’t think anyone I know would be using turbos alone, it would be along with lower wires (which might well include 016×022 niti, depending on the slot size) but I’m happy to hear otherwise.

    I’d be more familiar with the idea of bite opening curves in steel, or intrusion auxillary arches. But I don’t think there’s enough discussion/commentary on the difference between using these techniques in extraction V non extraction cases.

    Is there a paper that compares intrusion arches (be they blue elgiloy or otherwise) with steel reverse curves?

    Swords Ortho

  4. I find Tip-Edge is the fastest method to open bites and retract maxillary anterior teeth with the least negative effects on the mandibular incisors.

    • Jeffery, are you using anchor bends in one or both arches along with Class 2 elastics in a .016 SS wire to open bites? Do you see distal tipping of the first molars?

      • nice to ask. I have not used anchor bends in about 10 years. only times i consider is in phase 1 orthodontic cases which is rare for me.

      • nice to ask. I have not used anchor bends in about 10 years. only times i consider is in phase 1 orthodontic cases which is rare for me.
        but anchor bend with a wilcox wire also works

  5. In my clinical practice, a very effective approach was to use flat anterior bite plane with a lower fixed appliance.
    The bite plane ‘unlocked the occlusion’ and provided space for the lower arch mechanics to encourage molar extrusion.
    I would be interested to see this approach subjected to a clinical trail to see how effective it was compared to other approaches to OB reduction, for example, those mentioned in this particular Report.

  6. Clarification! that should be ‘an upper arch appliance with a flat anterior bite plane’

  7. Hello
    Thanks a lof for sharing.
    I normally like to use bite turbos in initial phase of treatment.
    Specially in class2-div2 case
    And later after proper alignment I would preffer to use reverse curve of speech 16*22 NITiin MBT 0.22 slot brackets
    This dormallt suffice my need for lower arch
    I also evaluates weather upper arch needed to be corrected for over bite correction?
    Than I go with mini implants with upper arch.
    I would really love to know the comparison between R.C.S of steel and NiTi.
    Thank you
    Smile centre dental clinic
    Surat India

  8. Bite turbos now have become an integral part of deep bite correction mechanics with the Damon system.. Early intervention using the lower appliance becomes possible and also the use of intrusion arches( RCS SS) is the mainstay of the treatment protocol in such cases ( barring vertically growing cases).
    In my opinion bite turbos cant be compared to intrusion arches as I believe a steep curve of Spee is usually resolved with Stainless Steel RCS wires , while bite turbos are there to facilitate early bonding and also supplements bite opening with the bite plate effect ( slight intrusion of lower anteriors and extrusion of posterior occlusal table)

  9. While we are all familiar with the many mechanics available to facilitate bite-opening, perhaps a more relevant question than rapidity is how stable these results are 5-10 years post treatment.

    • One way to facilitate stabilizing/maintaining the “opened” bite is to use a nocturnal removable Hawley w/an anterior
      bite plate or inclined plane. The reflex response from the PDL of the lower incisors will inhibit elevator muscle
      activity and stop molar intrusion thereby maintaining vertical stability.

    • Yes, a comparison of long-term stability between turbo’s and archwires would be a great question to have answered.

  10. This was a spurious study IMO. If the authors intend to study leveling efficiency, they need to compare the modes of application as they are actually used. A 16×22 Niti wire in a 022 slot is simply not the norm, nor does it have the requisite stiffness for arch leveling. Additionally, the significant 3rd order play anteriorly (>30 degrees) and the 2nd order play posteriorly means there will be significantly more proclination of the incisors, as well as distal tipping of the molars. That is only to be expected with this mode of application. The accepted standard is to work up to a 19×25 SS with or without a reverse curve. Thus, any findings for Group 1, only represent inappropriate application of leveling mechanics, and is not reflective of the typical leveling mechanics with 022 slot appliances.

  11. A more pertinent question is to make an accurate diagnosis prior to treatment which involves determining what is the approach needed to correct the deep overbite

    • An accurate diagnosis prior to starting any type of treatment is very critical. Knowing where to find accurate information that can be trusted is also key. A previous text titled (ORTHODONTIC and ORTHOPEDIC TREATMENT in the MIXED DENTITION – McNamara & Brudon Hardcover) published by Needham Press has
      a chapter that provides excellent information that provides “the numbers” to jaw lengths and facial height from
      a lateral ceph. This is excellent information for assessing facial growth patterns and what to use in treatment
      to achieve the best facial esthetics, smile and function. While the “numbers” are primarily of a caucasian base,
      they still help with knowing what type of treatment will affect the outcomes in other nationalities.

  12. I fully agree with John Pilley – I have routinely used a flat anterior bite plate on an upper removable appliance for many years. Facilitates the placing of lower incisor brackets.

    • I also have used this treatment modality for a number of years. To protect the brackets, in addition to reduce the overbite. I did suggest suggest this during treatment planning discussion with a younger colleague, only to be given a quizzical look.

  13. Can we use RCS round niti as the initial wire instead of straight round niti in cases of deep bite.

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