Azeri Orthodontic Society
Root resorption after orthodontic treatment (Literature review)
Yazan: Naphtali Brezniak, MD, DMD, MSD, and Atalia Wasserstein, DMD Tel Aviv, Israel

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Clinical diagnostic aids to root resorption

Radiographs are commonly used as a diagnostic aid for root resorption. Radiographic detection of apical root shortening requires a certain degree of resorption. It is difficult to develop a standardized technique to compare the same teeth at different times. Tooth movement makes it more difficult to assess the exact amount of root loss especially when the tooth is torqued or tipped. Commonly used radiographs are ineffective in assessing buccal and lingual root resorption.
Several radiographic techniques used include periapical bisecting angle, periapical paralleling, orthopantomogram, cephalogram, and lamiogram.
Despite its limitations, the radiographic technique that has the most favorable benefit to risk ratio in detecting and evaluating the degree of apical root material loss is the periapical paralleling technique. It provides the most appropriate information with the least irradiation to the patient when used for teeth that are most likely to exhibit blunting of roots: maxillary and mandibular incisors. The periapical technique provides less distortion and superimposition errors compared with the orthopantomogram or the lateral headfilm. By using the periapical paralleling technique for selected roots, up to 4 films enable absorption of lower radiation doses by radiosensitive tissues of the head and neck, according to measurements on the skin, compared with using the bisecting angle technique, orthopantomogram or lateral headfilm. This is of special importance in children, adolescents, and young adults whose radiosensitivity is higher than that of adults because of rapid growth of organs, thyroid position, and longer duration for the effects of radiation to be apparent.
Histologic studies are conducted for research purposes where all stages of resorption can be observed.

Clinical considerations related to root resorption

1. The patient or his parents must be informed that apical root shortening (root resorption) may be a consequence of orthodontic treatment. Its incidence is highly unpredictable.
2. Perapical radiographs: (a.) Periapical radiographs are an important part of complete orthodontic records as any pretreatment record, and are particularly useful to compare pretreatment and posttreatment root resorption. (b.) since it is impossible to predict the onset of root resorption, periodic control radiographs are indicated. Periapical radiographs of the incisors should be taken at least every year after appliance placement. (c.) Posttreatment radiographs are an essential part of complete records to assess the bone/root integrity after treatment, of which the patient must be informed.
3. Orthodontic treatment timing. Orthodontic treatment should begin as early as possible since there is less root resorption in developing roots and young patients show better muscular adaptation to occlusal changes. Adults have poorer adaptive ability and need more rigid and longer lasting mechanical forces.
4. The orthodontic force should be intermittent and light.
5. When root resorption is detected during active treatment, final goals must be reassessed. A decision should be made to terminate the treatment or to arrive at a treatment compromise. When necessary, applied forces should be stopped and/or a bite plane used to disocclude the teeth.
6. Habits such as nail biting or tongue thrust should be stopped, since it was shown that root resorption is more severe in such orthodontic patients.
7. All types of tooth movement can cause root resorption. It seems that intrusion is the most detrimental.
8. Occlusal traumatism and jiggling are potentially detrimental to the roots, and it is suggested to finish treatment with a correct occlusion.
9. It is essential to recognize that routine orthodontic tooth movement can have anatomic and physiologic limitations. If the objectives of treatment are beyond these limitations, surgical intervention may be required.
10. Teeth with resorbed roots can serve as abutments to bridges only when their root length exceeds the clinical crown length.
11. Orthopedic effect in the early treatment phase has less destructive potential on the roots compared with the dentoalveolar effect at a later treatment phase.
12. In choosing treatment appliances, the risk of root resorption should be weighed against appliance efficiency and individual treatment objectives.
13. Treatment time should be as short as possible while adhering to other important principles.
14. Traumatized teeth should be treated cautiously since they are more prone to root resorption during orthodontic treatment.
15. Medical examination and familial tendency records are of value especially in cases of severe or extensive root resorption.
16. If root resorption continues after appliance removal or during retention, seqeuntial root canal therapy with calcium hydroxide is advisable. Gutta-percha filling is the definitive therapy only after root resorption ceases.
17. It is advisable to take full-mouth radiographs when receiving a transfer case.

SUMMARY
All permanent teeth may show microscopic amounts of root resorption that are clinically insignificant and radiographically undetected. Root resorption of permanent teeth is a probable consequence of orthodontic treatment and active tooth movement. The incidence of reported root resorption during orthodontic treatment varies widely among investigators. Usually, extensive resorption does not affect the functional capacity or the effective life of the tooth. Most studies agree that the root resorption process ceases once the active treatment is terminated.
Root resorption of the deciduous dentition is a normal, essential, and physiologic process. Permanent teeth have the potential to clinically undergo significant external root resorption when affected by several stimuli. This resorptive potential varies in persons and between different teeth in the same person. This throws doubt on the role of systemic factors as a primary cause of root resorption during orthodontic treatment. Tooth structure, alveolar bone structure at various locations, and types of movement may explain these variations. The extent of treatment duration and mechanical factors definitely influence root resorption. In most root resorption studies, it is not possible to compare the results and conclusions because of their different methods. Further research in this field is necessary to advance the service of the specialty.
The question of whether there is an optimal force to move teeth without resorption or whether root resorption may be predictable remain unanswered.
This review indicates the unpredictability and widespread incidence of the root resorption phenomenon. In light of the orthodontists's liability of what is basically an unpredictable phenomenon, it is necessary that the specialty define this uncertainty and establish criteria of diagnosis, records, and informed consents to protect its members against unnecessary and unjustified litigation.

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