April 15, 2019

Orthodontic treatment does not reduce the chance of dental decay?

We are still unsure whether providing orthodontic treatment can reduce the chance of dental decay. This new study gives us some interesting information on this question.

One long-standing belief about orthodontic treatment is that by reducing dental crowding, we may reduce the plaque accumulation that could lead to caries. However, there is no reliable evidence that dental crowding is related to caries. As a result, it does not necessarily follow that orthodontic treatment may reduce the incidence of decay.

A team of Australian investigators looked at this question in this ambitious study. Community Dentistry Oral Epidemiology published this paper.

The influence of orthodontic treatment on dental caries: An Australian cohort study

Esma J. Doğramac David S. Brennan

Community Dent Oral Epidemiol. 2019;1–7.

DOI: 10.1111/cdoe.12446

What did they ask?

They did this study to answer this question;

“Is there an influence of orthodontic treatment on dental caries experience in a cohort of 30-year-old adults”?

What did they do?

They did a cross-sectional review of participants who had enrolled in a longitudinal study.

The study started In 1988-89 when the team screened 3925 13-year-old children who had not received orthodontic treatment. In 2005-6 they identified 1859 of the original sample and invited them to take part in this study.

At the start of the study, they collected the Dental Aesthetic Index (DAI) data on the sample of children.

When they saw them for the follow-up investigation, they collected the following data;

  • Decayed missing and filled teeth (DMFT)
  • Their sociodemographic status
  • Information on their tooth brushing frequency, orthodontic treatment experience and their dental attendance from questionnaires.

This was a complex dataset, so they analysed this with relevant multivariate statistics that took the effect of cofounders into account.

What did they find?

They obtained data on 448 participants. This was 24% of the original sample.  As a result, of this response rate, they compared the recalled sample with the original sample. They found that more of the follow-up participants were female and had both parents tertiary educated.

They presented a large amount of data. I thought that the most important findings were:

  • Approximately one-third of the participants had received orthodontic treatment.
  • 46% brushed their teeth twice a day
  • There was no effect of orthodontic therapy on caries experience.
  • Socio-demographic and dental health variables were associated with caries.
What did I think?

Firstly, this was an ambitious and complex study. As with all studies, there are some limitations. The investigators drew attention to these, and they pointed out:

  • The final response rate was low. Nevertheless, I thought that they included a large number of participants. Unfortunately, there was some difference between the original sample and the final respondents and we have to consider if this could lead to bias.
  • They relied on self-report data from questionnaires. This may be inaccurate.

I am also concerned about the use of the DAI. While the DAI is a good measure for the need for orthodontic treatment. It is a composite measure and does not always record crowding. For example, a person may have well-aligned arches with a large overjet. This will score high on the DAI, but they will not have crowding.

This is important because if we want to measure the relationship between crowding, orthodontic treatment and caries,  we need to measure individual tooth crowding at baseline. We can then test if the crowding was related to caries at the follow-up, with or without orthodontic treatment. Unfortunately, the DAI does not have sufficient accuracy to enable this to be done for every case.


I think that this study was very interesting. However, we should think about whether the issues that I have highlighted influence the conclusions.

I feel that this study provides us with some of the best evidence that we can get on this question. The finding that dental care behaviour and socio-demographic factors are more relevant to caries experience than orthodontics is logical. As a result, I cannot help thinking that orthodontic treatment does not prevent dental caries in a population of children. However, this is still up for debate?


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Have your say!

  1. I agree that orthodontic treatment does not prevent dental caries in children. But, surely, the best way to decide whether a well-aligned arch is more prone to decay compared to a poorly aligned arch would be to measure just that in orthodontically untreated arches. I am assuming that someone will have done this at some time – but I haven’t checked. Forget orthodontically-corrected arches – there would appear to be too many variables here – use what nature has gifted to compare! We know that decalcification is a big risk during treatment, but perhaps they should check whether individuals are more prone to Cl2 and ClV cavities following treatment.

  2. We have argued (Benson PE, Javidi H and DiBiase AT. (2015) What is the value of orthodontic treatment? British Dental Journal 218: 185-190) that it is unlikely we will show orthodontic treatment improves dental health at the population level, although in some individuals it will help. I do believe that orthodontic treatment improves social and emotional well-being and this can be demonstrated at both individual and population levels. We should not be shy about declaring this.

  3. I know some of us, if not all of us, would love there to be some health benefit from braces, which would then mean we are doing stuff for reasons other than appearance. We now have sleep apnoea and breathing as reasons, to add to caries, perio and TMD. But there are no other reasons discovered as yet and are unlikely to be. I think we need to be honest to ourselves and to our patients (more importantly) that treatment is almost exclusively cosmetic.
    The fact appears to be that teeth aren’t all that bothered about their appearance and just want to achieve some sort of fit when possible. Even when they don’t people can usually eat ok. Crookedness of teeth is not an illness to be cured, it’s often a way to achieve an occlusion when either the teeth are odd (shapes or sizes or number) or the top and bottom jaws don’t perfectly line up; it’s a natural phenomenon and changes with age as the face changes a bit. Please lets stop pretending otherwise.

  4. As a general dentist I am a little surprised and think orthodontists should be happy that there seems to be no difference in caries experience at least at this population level.

    Orthodontic treatment is seen as a risk factor for caries and we know there is a shift in the biome with fixed appliances toward bacteria associated with caries.

    Presumably orthodontics to reduce caries is aimed at reducing areas of thick plaque accumulation which is a risk factor but this would be very much secondary to changing patient level factors such as diet, OH and fluoride use.

    To increase caries risk of someone ( by initiating orthodontic treatment) on presumably a high risk individual to lower their caries risk seems circuitous and unlikely to be effective.

    Two things of interest, and I don t have access to the original article at the moment to check, most caries data is based on restorations or cavities and without good diagnostic coding we are including the very varied restorative decision making of dentists.

    Secondly orthodontic treatment will be one of an individuals most intensive oral health experiences and as such provides a very significant teachable moment. How many orthodontists do a recognised caries risk assessment?

    Treating caries by risk assessment is a paradigm with a very large translational gap and with all the responses regarding screening for OSA, the worlds most common chronic disease seems to be of relatively little interest.

    White spot lesions (around brackets or elsewhere) have one of the highest odds ratios as predictors of future caries. ( NB They are actually caries they just aren’t cavities or restorations yet.)

    Orthodontists have a very important role to play in reducing caries and the surprising finding that those who have had orthodontic treatment don’t have an increased caries experience warrants a closer look to find out why this is.

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