Orthodontic Aligners and root resorption: A systematic review

Most orthodontic treatments or rather the process of orthodontic movement are frequently accompanied by their own assortment of problems. External apical root resorption (EARR) has been repeatedly mentioned superimposed with orthodontic movement as an iatrogenic side effect.

Early in the 1800s, dentists and researchers noticed that orthodontic treatment was capable of significantly shortening tooth roots. It wasn’t until 1932, that Beck and Marshall gave this peculiar phenomenon a technical name. It has since been known as “resorption”, often referred to as an induced inflammatory condition particularly instigated or aggravated by orthodontic forces. Experts confirm that a patient following orthodontic treatment is more likely to incur inevitable damage to the cementum, periodontal tissues, alveolar bone, and pulp.

Generally speaking, root resorption is of multifactorial aetiology. But, studies have narrowed down the probable causative agents to two types: biological factors and mechanical factors. Biological factors include genetics, chronological and dental age, gender, and ethnic variation with some predisposition to psychological stress. Mechanical factors for root resorption can be an orthodontic force, or type of force, the type of orthodontic appliance, or the duration of treatment.

Despite everything we know about root resorption and its possible connection to orthodontic treatment, there is still no robust scientific evidence regarding the severity and incidence of resorption with fixed appliances. A new study might be the gateway to open this can of worms.

A team from Morocco conducted this study. It was published by International Orthodontics.

Orthodontic aligners and root resorption: A systematic review.

Elhaddaoui R(1), Qoraich HS(2), Bahije L(2), Zaoui F(2).

Int Orthod. 2017 Mar;15(1):1-12. doi: 10.1016/j.ortho.2016.12.019. Epub 2017 Jan 26.

What they asked

The authors conducted this study:

“To assess the incidence and severity of root resorption following orthodontic treatment using aligners and associated factors.”

What they did

They conducted an electronic search for articles that were relevant to the present systemic review. The databases they consulted were: Medline, Pubmed, Embase, EBSCO Host, Cochrane Library, and Science Direct. The search was limited to French and English.

They included meta-analyses, randomized, and non-randomized controlled trials, cohort studies, and descriptive studies that were published before December 2015. A comparative analysis was also made with fixed multi-bracket treatments.

What they found out

Out of 93 articles that were selected, 48 references were excluded as they were opinion-based articles, case studies, studies dealing with fixed appliances alone, reviews of literature, or questionnaire-based studies. In the end, only 3 studies were able to meet their selection criteria.

They found that the incidence of root resorption ranged between 0% and 46%, of which 6% were severe cases. Relative to fixed multi-bracket non-extraction treatments to correct the same malocclusions, the incidence of resorption ranged between 2% and 50%, of which 22% were severe cases. They were able to conclude that in both techniques, the incidence of resorption was higher for the maxillary incisors. The rate of resorption was also not influenced by age or sex.

What we can conclude

The results of the study were underwhelming, to say the least. They found that root resorption could potentially result from orthodontic treatment. However, the incidence and severity of resorption in malocclusion cases not requiring extractions were both lower as compared to results reported for fixed multi-bracket systems.

However, these findings must be taken with caution since the two techniques differed vastly in a number of criteria (such as the need for extractions, duration of treatment, and the type and intensity of forces applied).