Anna Pogorzelska, Anna Stróżyńska-Sitkiewicz, *Kazimierz Szopiński
Orthodontically induced root resorption – a literature review
Resorpcja korzeni indukowana leczeniem ortodontycznym – przegląd piśmiennictwa
Department of Dental and Maxillofacial Radiology, Faculty of Medicine and Dentistry, Medical University of Warsaw
Head of Department: Professor Kazimierz Szopiński, MD, PhD
Częstym niepożądanym efektem ubocznym w leczeniu ortodontycznym jest resorpcja korzeni przesuwanych zębów.
Resorpcja jest obserwowana najczęściej w zębach stałych. Proces ten może dotyczyć każdej części korzenia, najczęściej jednak jego części wierzchołkowej lub okolicy szyjki zęba. Powstawanie i rozwój tych zmian jest procesem długotrwałym i zależnym od różnych czynników. Etiologia zmian resorpcyjnych związana z leczeniem ortodontycznycznym jest dyskutowana przez wielu autorów, a w literaturze występuje wiele jej klasyfikacji. Na szczególną uwagę zasługują prace dotyczące technik leczenia wad zgryzu i możliwych powikłań terapii. Dzięki nowoczesnej diagnostyce można wcześnie wykryć tę patologię i jej zaradzić. Do technik tych są zaliczane zdjęcia zębowe wykonane techniką kąta prostego w połączeniu z tomografią komputerową wiązką stożkową. Lekarze zauważają nie tylko potrzebę doprowadzenia zębów pacjenta do pięknego uśmiechu, ale także biorą pod uwagę ewentualne skrócenie długości korzeni. Proces ten nie jest do końca poznany, ale świadomość możliwości wystąpienia powikłań jest istotna przy planowaniu i prowadzeniu leczenia zarówno ortodontycznego, jak i ogólnostomatologicznego.
Root resorption in moved teeth is a common undesirable side effect of orthodontic treatment.
This pathology usually affects permanent teeth. Although any part of the root may be involved, the apical or cervical area is usually affected. The formation and development of these changes are a long-term process and depend on various factors. The etiology of resorptive changes associated with orthodontic treatment has been widely discussed by many authors, who proposed numerous classifications. Particularly noteworthy are the works on techniques for the treatment of malocclusion and their potential adverse effects. Modern diagnostic methods allow for an early detection of this pathology and the implementation of appropriate therapeutic measures. These techniques include periapical radiography (paralleling technique) combined with cone-beam computed tomography. Dentists not only notice the need to achieve a beautiful smile, but they also take into account possible root shortening. This process is not fully understood, but realizing its existence is important for planning and implementing both orthodontic and general dental treatment.
Orthodontic treatment is often associated with root resorption of the teeth being moved, leading to the loss of hard tissue (dentin, cement and/or alveolar bone). It is a long-term, painless process, which is usually revealed accidentally during a routine X-ray (1-3). The process may be either physiological or pathological. Physiological root resorption occurs in primary dentition as a result of biochemical reaction between permanent tooth follicle and the periodontium of the root of the primary tooth (4). This process begins at the age of about 4-5 years, i.e. 2-4 years before physiological tooth replacement (5).
Pathological resorption usually effects permanent dentition. Several classification systems for tooth resorption, depending on its location, causative factors and stage, may be found in literature. The simplest and the most common classification system used in clinical practice distinguishes external, internal and external-internal tooth resorption (5-7). External resorption may affect the cervical region, the mid or the apical portion of the root, beginning superficially and spreading towards the dentin and dental cavity. The most common factors responsible for external resorption include periapical tissue inflammation, trauma (8), ectopically erupting adjacent tooth (9), tumour invasion, a dentigerous cyst, chronic occlusal trauma and orthodontic treatment (10, 11). Internal root resorption is less common (12). It begins in the dentin and spreads towards the cement (5). The most common causative factors include chronic bacterial pulpitis and local circulatory impairment, which may be caused by an injury (6, 10). A simultaneous occurrence of these two processes is referred to as external-internal or perforating resorption (10).
The relationship between orthodontic treatment and root resorption was first described by Ottolengui in 1914 (13), and radiologically evaluated by Ketcham, who already in the 1920s noticed apical root reduction after orthodontic treatment (14). This way, the author drew the attention of future generations of orthodontists to root resorption, which is a complication of orthodontic treatment, as well as to factors promoting this process. The study presented by Ketcham also aimed to raise doctors’ awareness on the need for radiological evaluation both before and after orthodontic treatment (14, 15). The term “orthodontically induced inflammatory root resorption” (OIIRR) was introduced in terminology and literature by Brezniak and Wasserstein in 2002 (11).
The aim of this paper was to present aetiology, distinctive features and types of orthodontically induced root resorption and the proposed based on the available literature.
A systematic review of literature on orthodontically induced root resorption was performed using the following databases: PubMed/MEDLINE, Polish Medical Bibliography and widely available dental literature. The following keywords were used for creating literature database: external resorption, cervical resorption, root resorption. Both, English- and Polish-language literature was included. Papers published until December 31, 2017 were included in the study. Papers whose authors performed radiological assessment of root resorption during or after orthodontic treatment were included. Articles whose authors focused on other aspects of root resorption were excluded.
Brezniak and Wasserstein drew attention to important radiographic elements that should be analysed by an orthodontist before treatment initiation, such as the shape of roots, the presence of endodontically treated teeth, agenesis, aplasia, ectopy, replanted teeth, bone structure and malocclusions (11, 16). Many authors, e.g. Vlaskalic et al. (17) and Topkara et al. (18), classified aetiological factors into two groups: individual (patient-related) factors, and factors directly associated with orthodontic treatment (tab. 1).
Tab. 1. Aetiological factors in OIIRR
|Individual factors||Orthodontic factors|
|– Genetic factors|
– Group of teeth
– Root shape
– Systemic diseases
– Dental trauma
|– Age at treatment onset|
– Type of appliance
– Treatment duration
– Forces used
– Treatment mechanics
Individual factors include genetic factors (17-20), race (20), the group of teeth affected by resorption, root shape (2), type of malocclusion (18, 20), general diseases such as asthma and allergies (2), as well as previous damage of dental structure, e.g. cervical resorption induced by general factors: Paget’s disease (osteitis deformans), tuberous sclerosis complex, ectodermal dysplasia (21-23) and dental trauma (24).
The following orthodontic factors have been distinguished by authors: age (25, 26), type of appliance (removable or fixed), treatment duration, forces used, elastics and treatment mechanics (2, 25, 27) (tab. 1). OIIRR is less common in patents aged about 11 years (± 1), which is due to higher biological tolerance – undeveloped roots are protected by predentin and a wider layer of cementoid (25, 28, 29). Maxillary resorption usually affects lateral and central incisors, as well as canines, while the highest risk of mandibular resorption is reported for canines, central and lateral incisors, respectively (24, 30-33). The shape of the root is also important: roots with features of dilacerations, bottle-shaped or pointed roots are resorbed more often compared to normal-shaped roots, while short and wide roots are less likely to be resorbed compared to long and narrow ones (25, 29, 34). The duration of orthodontic treatment is another predisposing factor. Root resorption is very rarely detected in patients treated for 1.5 years. The risk of advanced root resorption is increased in patients treated for more than 2-3 years. The risk is reduced in patients with a 2-3-month interval after a 6-month therapy, followed by continued active treatment (18, 29). The risk of root resorption is also associated with malocclusions, with the highest prevalence seen in patients with an open bite (30). Various forces are applied during orthodontic treatment, depending on the chosen treatment approach. The use of large alternating forces and significant tooth shifting predispose to resorption (30, 32). Long-term use of class 2 elastics also increases the risk of resorption. The mechanics used during treatment is another aspect of orthodontic therapy. Intrusive mechanics combined with anterior retraction is associated with higher resorption compared to retraction alone (27, 32, 33). Intrusive mechanics causes more resorption than non-intrusive treatment (35). Another factor predisposing to OIIRR is the type of appliance used during treatment – fixed appliances increase the risk of resorption compared to removable appliances due to the continuity of forces applied (20, 34). The type of dentition is the last analysed aspect; Fiore et al. found that root resorption also affects primary teeth included in fixed appliance, but at sites untypical for physiological resorption (36). Furthermore, genes (TNFRSF11A, IL-1beta gene) and salivary biomarkers which may be assayed in orthodontically treated patients diagnosed with apical root resorption have been identified (tab. 2).
Tab. 2. Individual and orthodontic aetiological factors in OIIRR
|Age||over 11 years of age|
|Group of teeth (consecutively from the most vulnerable to OIRR)||maxillary: lateral and central incisors, canines mandibular: canines, central and lateral incisors |
|Root shape ||root deceleration, bottle-shaped root or pointed root|
|Treatment duration||more than 2-3 years|
|Type of malocclusion||an open bite|
|Forces||high alternating forces, large tooth shifts, class 2 elastics|
|Treatment mechanics ||intrusive mechanics combined with anterior retraction|
|Type of appliance||fixed |
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