January 18, 2021

Incisal trauma is related to large overjets.

A child with an increased overjet maybe at risk of incisal trauma. This has led to suggestions that we should treat children early to avoid trauma.  The association between trauma and overjet was looked at in this new study.

Several studies have shown that increased overjets are susceptible to trauma. However, others do not support this concept.  Furthermore, most of the studies are cross-sectional. As a result, they simply represent a “snapshot” of this problem.  This new study was longitudinal, and it provides us with useful information on this critical issue.

A team from Geneva, Switzerland, did the study. Progress in Orthodontics published the paper.

What did they ask?

They did the study to ask:

“Are children with large overjets at greater risk of incisal trauma compared to children with smaller or normal overjets”?

What did they do?

They did a longitudinal observational study of a sample of 1900 children aged 6-12 years in Geneva. They examined the children in their schools and collected the following data.

  • Demographics: Age, Gender, grade level and living conditions.
  • The type of any dental injury
  • The overjet measured in mm.

They then collected the data again a year later.  Some of the children had moved to secondary schools after this time, and they had to exclude 372 of them from the second data collection stage. As a result, they had longitudinal data on 1413 (including absences from school). This was a dropout rate of 7.4%.

They divided the trauma data into hard tissue or luxation injuries.  Each maxillary and mandibular tooth was scored for its presence and type of injury. Importantly, they based the data on clinical non-radiographic information.  Finally, they calculated the frequency of subjects with and without dental injuries for different overjets with a cut-off point of 6mm.

They analysed the data with the relevant univariate and multivariate statistical tests.

What did they find?

They collected data on 1413 children (723 males and 690 females).  This was 5.6% of all children in Geneva’s primary public schools.  Their ages ranged from 7 and 14 years.

At the first data collection point, they found that trauma had occurred for 172 children  (16% of the boys and 12% of the girls.  Of the children that had experienced trauma, 53 had an overjet greater than 6mm.  This meant a 4.03 times higher risk of trauma compared with children with a normal overjet.

At the follow-up data collection, they found 104 additional injuries.  The total sample of children had 98 with an overjet greater than 6mm, and 14 of these had suffered incisal trauma.  This meant a significantly increased risk of trauma if the overjet was greater than 6mm. The Relative risk being 3.37 (95% CI, 1.81-6.27).

Their overall conclusion was:

“Increased overjet is a risk factor for traumatic dental injuries in children”.

“Early correction of increased overjets to reduce the chance of trauma should be considered”.

What did I think?

I thought that this was a very worthwhile research project.  The authors selected a representative sample of children from schools in Geneva. Their methodology was sound. One criticism was that they recorded the trauma from clinical examinations and structured questions.  Importantly, this avoided the need for a radiographic examination. Which would have been unethical. Nevertheless, this does mean that there is potentially some inaccuracy in the data.  However, I think that this should be expected.

I was not sure why they presented the data for each stage of the data collection differently.  Unfortunately, they did not provide information on the number of children with overjets greater than 6 mm at baseline. As a result, I could not calculate the Relative Risk for this group.

Nevertheless, they did show that increased overjet of greater than 6mm was associated with a 3 fold increased risk of trauma compared to when the overjet was less than 6mm.

This then brings us to the clinical relevance of these findings.  The authors suggest that we should consider early treatment to reduce the chance of trauma.  This is a compelling suggestion, and I would like to refer to the early treatment Class II studies results.  I have posted about this before when we looked at trauma in our Cochrane Systematic Review.  This showed that if we were treated early, then there was a potential for a 12% reduction in trauma episodes. However, we also showed that we needed to treat 10 children to avoid one episode of trauma.  This means that this decision needs to be taken carefully because the treatment does not entirely avoid trauma.

In summary

When I consider all the research done in this area. I think that there are three main points.

  • Trauma is related to Class II increased overjet.
  • Overjets can be corrected, and this may help, but the effectiveness of treatment is not high.
  • We can provide important information to patients about this treatment. As a result, they can make a well-informed decision on whether to have treatment.

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Have your say!

  1. Avatar

    Was there any effect on trauma incidence from age or sex? Both may effect whether you consider treatment on a specific patient at a specific time. Eg if trauma is not more common in girls then there is no need for early intervention. It’s complicated

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    Dr, O’Brien, thank you for this study. As a pediatric dentist and orthodontist and one who instructs both residents, I have been very interested in this subject. The conclusions of the Class II studies at UNC and UF did not support routine treatment of patients with increased overjets. They did suffer a great deal of trauma but seemed to have equal amounts of trauma. I have read your Cochrane Studies and the NTT numbers. The one variable you leave out in this analysis is the type of trauma sustained. The difference in treatment of an uncomplicated crown fracture in enamel only is vastly different from an avulsion yet they are both categorized as dental trauma. I believe you NTT would change from 10 for 1 to maybe 20 for 1 if you factored in periodontal or severe dental injuries. There is also some evidence on how behavior and activity factor in as well. This field is open for investigation.

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    Dear Prof

    If you might agree that the Class II malocclusion phenotype (distal occlusion) is initially observable under the age of 71 months old, will always persist and worsen beyond without appropriate intervention (Bishara, McNamara et al), and, the associated excessive overjets in these kids can often predispose them to otherwise preventable traumatic dental/soft tissue injury, etc., what might be your explanation for why parents of such afflicted children are frequently instructed (by orthodontists, pedodontists and/or GDP’s) to wait for more permanent teeth to erupt before beginning treatment?

  4. Avatar

    Great job!
    We have performed a research en 2004 about this issue. Unfortunetely, it was published in Portuguese language.

    • Avatar

      Dear Liana

      The English translation of the abstract (below) is interesting ; will you please post some images from the paper here or maybe to me personally([email protected])?

      Thank you for considering,


      The purpose of this study was determine the incidence of fractures in the permanent upper incisors in relation to the Rh-P line (fracture line).A sample of 40 cephalometric lateral teleradiographies of patients with fracture incisors, in which it was determined the distance between the incisal of the upper permanent incisors and the fracture line, was used. The results showed that 100% of the fracture upper teeth were set ahead of this line, which stressed the importance of an early orthodontic treatment and the use of mouth protectors in children who present upper incisors set ahead of the fracture line, as a preventive measure against the fracture of these dental elements

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