6 New Zealand Dental Journal – March 2013 Orthodontic treatment planning for previously root-canal- treated teeth can be challenging. Patients may present with root- canal-treated teeth secondary to deep carious lesions or trauma. The need for orthodontic treatment may develop following dental trauma or when adult patients seek rehabilitation of their dentition. Clinicians can sometimes be unsure of how, or when, to proceed with orthodontic tooth movement of traumatised or root-canal-treated teeth, or about the risks involved. This article considers the current recommendations for orthodontic tooth movement of such teeth. Previously traumatised teeth The literature is sparse on the influence of previous trauma during orthodontic treatment, yet it has been reported that more than one in ten patients have experienced dental trauma prior to orthodontic treatment (Chadwick and Pendry, 2004). The prognosis of traumatised teeth plays a role in orthodontic treatment planning. The chance of pulpal healing following a luxation injury is strongly related to the dimension of the apical foramen, with clinical and radiographic diagnosis of pulpal necrosis sometimes occurring years after a luxation injury (Andreasen and Pedersen, 1985). An analysis of 637 luxated teeth revealed that only the type of injury and stage of root development were important determinants of pulpal survival. The chance of pulpal necrosis following a lateral luxation injury (which had occurred in 19% of the sample) was 9% in teeth with open apices, whereas 77% of the teeth with closed apices had pulp necrosis (Andreasen and Pedersen, 1985). A 2004 meta-analysis found that, following a moderate intrusion injury, nearly half (45.5%) of teeth with open apices remained vital, yet no teeth with closed apices did so (Chaushu et al., 2004). If a traumatic injury has led to pulp necrosis and bacterial infection, toxins within the pulp space can track through the dentinal tubules and cause external inflammatory resorption unless the infected pulp is removed and root canal disinfection carried out (Andreasen et al., 2011). If there is evidence of pulp necrosis and bacterial infection, endodontic management is required prior to orthodontic treatment. It must also be remembered that adjacent or opposing teeth may have also experienced trauma at the time of the accident (Majorana et al., 2002). When avulsion of a permanent tooth has occurred, important prognostic factors include the time the tooth is outside the mouth, and the medium in which the tooth is stored prior to replantation (Steiner and West, 1997). Immediate replantation is ideal, because it has been shown that, after 60 minutes of extra- oral time (even when stored in a physiologic medium such as milk) or 30 minutes of dry time (Andreasen et al., 1995; Gregg and Boyd, 1998; Kinirons et al., 2007; Flores et al., 2007b), the periodontal ligament cells may be viable but compromised (Day et al., 2008), leading to unavoidable ankylosis (Andersson et al., 2012). If the tooth needs to be cleaned, it can be gently rinsed under cold water for less than 10 seconds (Flores et al., 2007b), then replanted, without any contact with the root surface. The patient can gently bite to keep the tooth in place until emergency dental treatment can be sought. If the tooth cannot be replanted, storage in water must be avoided; the tooth can be stored in milk, saline solution or special storage solution such as “Hank’s Balanced Salt Solution” or it can be placed in the patients’ buccal vestibule until the dentist can replant it. Replacement root resorption can result from trauma to the protective cementum layer of the tooth; it is a pathologic process involving cementum, dentine and periodontal ligament being replaced with bone. Ankylosis is the “clinical diagnosis for the end result of replacement resorption, whereby the tooth is no longer capable of normal physiologic movement due to the fusion of bone to the root surface” (American Association of Endodontists, 2012). There is a higher likelihood of replacement resorption following severe trauma, such as extrusive luxation or avulsion injuries. It has been asserted that ankylosis will occur if 20% or more of the root surface is affected (Andersson et al., 1984). Ankylosis can generally be detected two to 12 months after injury, and its signs may include a high, metallic tone upon percussion, infra-occlusion and the radiographic appearance of an obliterated periodontal ligament (Andersson et al., 1984). If this occurs, teeth will not move through bone upon application of orthodontic force. Such teeth may, however, be used to enhance anchorage during orthodontic treatment. At this stage, there is insufficient evidence to conclude whether or not orthodontic tooth movement of traumatised teeth increases the risk of pulp necrosis above that of uninjured teeth undergoing orthodontic tooth movement (Rotstein and Engel, 1991; Hamilton and Gutmann, 1999; Healey et al., 2006). However, if endodontic treatment is required following moderate- to-severe dental trauma, the additional inflammatory stimulus from orthodontic tooth movement may prolong the destructive phase acting on the cementum, thereby increasing the risk of ankylosis. Orthodontic treatment should therefore be postponed for up to one year in order to enable observation of healing and monitoring for ankylosis (Drysdale et al., 1996). Some patients requiring orthodontic treatment may present with teeth which have previously sustained root fracture, whether at the level of the apical third, middle third or cervical third. In cases of a cervical-third root fracture without separation of fragments and which has a positive response to sensibility testing from the coronal portion, the tooth may need to be splinted for up to four months (Flores et al., 2007a), and the fracture must be observed for at least two years prior to orthodontic tooth movement (Zachrisson and Jacobsen, 1974). If separation of the Orthodontic tooth movement of traumatised or root-canal- treated teeth: a clinical review V J Beck, S Stacknik, NP Chandler and M Farella Report Peer-reviewed paper. Submitted July 2012; accepted November 2012. Orthodontic movement of teeth