Traumatic dental injury (TDI) is common in children with studies suggesting that prevalence ranges between 15-30 %. An association between TDI and increased overjet was suggested in the 1950s but findings from observational studies have been inconsistent.
The aim of this review was to assess the association between overjet and TDI.
Searches were conducted in the Medline/PubMed, SCOPUS and Google Scholar databases. Cross-sectional or case-control studies published between 1990-2014 were considered. Selected primary studies were divided into subsets: ‘primary teeth, overjet threshold 3-4 mm’; ‘permanent teeth, overjet threshold 3-4 mm’ (Permanent3); ‘permanent teeth, overjet threshold 6 ± 1 mm’ (Permanent6). The pooled odds ratio (ORs) for TDI due to large overjet with 95% CIs were estimated for each study subset.
- 54 studies involving >10,000 patients were included from Africa, America, Asia and Europe.
- Most studies included children and adolescents but 3 included adults.
- Pooled odds ratios
- Primary teeth with 3-4 mm overjet = 2.31 (95%CI; 1.01 – 5.27)
- Permanent teeth with 3-4 mm overjet = 2.01 (95%CI; 1.39 – 2.91)
- Permanent teeth with 6 ± 1 mm overjet = = 2.24 (95%CI; 1.56 – 3.21)
- The population attributable fraction (PAF)
- 3-4 mm overjet = 21.76% (95%CI; 9.70 -34.46%)
- 6 ± 1 mm overjet = 10.17% (95%CI; 4.86 – 16.79%)
The authors concluded
The present meta-analysis of observational studies showed that large overjet may double or even triple the risk for TDI to anterior primary and permanent teeth and that, at global level, large overjet is partly responsible for 100–300 million TDIs. These figures do not require further comments and corroborate the idea that the global burden of TDI is very high and that large overjet has a significantly high impact on this figure. The reported pooled ORs help assess the patients’ risk for TDI and, therefore, to decide whether preventive measures must be taken to decrease such a risk. These measures may range from orthodontic treatment to mouth protection for exposed individuals at high TDI risk and tutors’ counselling to increase their awareness towards their children proneness to TDI while they are playing or are at home. Well-designed clinical trials and good-quality systematic reviews are necessary to assess the effectiveness of these measures to decrease the risk for dental injuries in subjects with large overjet.
This interesting meta-analysis of observational studies suggests that a large overjet may double the risk of a TDI and estimates the global impact of this problem. Although many The PAF estimates suggest that approximated 22% of TDIs are attributable to large overjet in patients with overjet of 3-4 mm and 10% in those with 6 ± 1 mm overjet which is perhaps counterintuitive as you might think that the larger overjet posed a larger risk?
TDIs are left untreated the potential initial and ongoing treatment costs are high. The 2014 Cochrane review by Thiruvenkatachari et al (Dental Elf – 7th Jan 2014) note that the only benefit for providing early orthodontic treatment for patients with class II malocclusions was a reduction in the incidence of incisal trauma but here again there are treatment costs and potential for other adverse outcomes.
Petti S. Over two hundred million injuries to anterior teeth attributable to large overjet: a meta-analysis. Dent Traumatol. 2015 Feb;31(1):1-8. doi: 10.1111/edt.12126. Epub 2014 Sep 27. PubMed PMID: 25263806.
Dental Elf – 7th Jan 2014 – Early orthodontic treatment may reduce incisal trauma in children with class II malocclusions
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Indeed, it might seems counterintuitive that overjet >6mm is responsible for “only” 10% TDI’s while overjet >3mm is responsible for 26% TDI’s. But this is due to the fact that the number of subjects with overjet >6mm are few, while those with overjet 3-6mm are many.
Thus, remembering the unforgettable lesson of Geoffrey Rose “a large number of people at a small risk may give rise to more cases of disease than the small number who are at a high risk” (Rose G. Sick individuals and sick populations)
This is pivotal in disease prevention: if we have ten patients with overjet 3-6mm and one patient with overjet >6mm the (counterintuitive) epidemiology suggests that the next TDI will occur in one of the ten with overjet 3-6mm. But if we have one patient with overjet 3-6mm and one patient with overjet >6mm the (intuitive) epidemiology suggests that the next TDI will occur in the patient with overjet >6mm.
Few thing are more counterintuitive than this…