Orthodontics and root resorption part 2

Orthodontically-induced inflammatory root resorption (OIIRR) occurs when orthodontic forces are applied to the dentition (Figure 1). This results in the induction of a local periodontal inflammatory process. This inflammation, which is essential for tooth movement, is the fundamental component of the root resorption process and causes remodelling of both cementum and dentine of the roots.¹ During periods of relative quiescence, the cementum undergoes repair such that, for most teeth in most patients, the changes in root length are so small as to be difficult to detect and are often clinically insignificant.² Different treatment modalities have been implicated in the development of OIIRR and the extent to which this affects the dentition.

Although there is not a large body of evidence linking the length of treatment to an increased risk of root resorption, Brin et al³ examined the effect of 2-phase vs 1-phase treatment of Class II cases on root resorption. They suggested that those children who underwent a 2-phase treatment, using a Bionator functional appliance followed by fixed appliances, had the fewest incisors with moderate to severe OIIRR. They also demonstrated that, as treatment time increased, so did the odds of OIIRR. The odds of a tooth experiencing severe root resorption were greater with a large reduction in overjet during phase 2.