Report Peer-reviewed paper. Submitted July 2012; accepted November 2012.

Transcription

1 Report Peer-reviewed paper. Submitted July 2012; accepted November Orthodontic tooth movement of traumatised or root-canaltreated teeth: a clinical review V J Beck, S Stacknik, NP Chandler and M Farella Orthodontic treatment planning for previously root-canaltreated teeth can be challenging. Patients may present with rootcanal-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 extraoral 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 moderateto-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 6 Orthodontic movement of teeth New Zealand Dental Journal March 2013

2 fragments has occurred, the displaced coronal segment will need to be repositioned prior to splinting; if this is not possible, the clinician may consider removing this fragment and extruding the apical segment for restorative purposes (discussed below). If the root fracture involves the middle third or apical third, any luxated fragments may be repositioned, splinted and reviewed radiographically after three to four weeks. The splint may be removed at this appointment, providing there is no sign of infection at the fracture site (Andreasen et al., 2011). Following a root fracture, if there is any sign of pulp necrosis with subsequent bacterial infection, root canal treatment must be carried out on the coronal fragment, with or without surgical removal of the apical fragment (Andreasen, 2003). A retrospective study of 34 root-fractured teeth showed good healing in 79% of the teeth, with the only significant factor contributing to healing being incomplete root development (where the tooth had an open apex), which accounted for 79.4% of the total sample (Feely et al., 2003). Interestingly, the site of the fracture did not significantly affect healing (74% of the fractures involved the apical third and 24% the middle third). Teeth requiring root canal treatment during orthodontic treatment If the trauma occurs during orthodontic treatment, it may be difficult to determine whether a patient s symptoms result from pulp inflammation due to the trauma or a transient, reversible pulpitis due to the normal physiologic pulpal response to the application of orthodontic force (Hamilton and Gutmann, 1999). If pulpal necrosis is suspected, it is prudent to check tooth vitality and look for any radiographic periapical changes while halting tooth movement for three months. If root canal treatment is required, patients must be made aware of the greater treatment time involved, due to tooth movement being discontinued during root canal treatment and the subsequent (and necessary) healing period. The timing of orthodontic tooth movement following root canal treatment is important. The tooth should be followed up after root canal treatment in order to assess the outcome and quality of the treatment. The European Society of Endodontology (2006) has published quality assurance guidelines, advising that endodontic treatment can be considered successful one year post-treatment if there is absence of pain, swelling or other symptoms, as well as no sinus tract, no loss of function, and radiographic evidence of a normal periodontal ligament space around the root. If the treatment was required secondary to dental caries, orthodontic tooth movement may commence immediately (Drysdale et al., 1996). If root canal treatment resulted from dental trauma which occurred during the period in which the patient was undergoing orthodontic treatment, that treatment should be postponed for one year to allow observation of healing and monitoring for ankylosis (Drysdale et al., 1996). If a tooth is deemed to have a poor prognosis, the patient (and his/her parents) should be informed of all possible options and consequences before continuing with any orthodontic treatment. Treatment planning must be reconsidered with respect to the short-, medium- and long-term goals of treatment (Day et al., 2008). Teeth requiring root canal treatment during (or prior to) orthodontic tooth movement may benefit from being initially prepared and dressed with calcium hydroxide (Steiner and West, 1997). Steiner and West recommended that dressings should be replaced every three to six months until the completion of orthodontic treatment, when final obturation with gutta percha can be completed. It is thought that calcium hydroxide may halt root resorption, because it is alkaline and believed to impede osteoclastic and cementoclastic activity (Bender et al., 1997), as well as encouraging apexification in incompletely formed roots (Steiner and West, 1997). More recently, a single-visit mineral trioxide aggregate technique has become a popular alternative for managing teeth with open apices (Rafter, 2005), especially in the light of later studies showing that prolonged calcium hydroxide dressings (for longer than 30 days) lead to a higher risk of cervical root fracture (Andreasen et al., 2002; Doyon et al., 2005; Rosenberg et al., 2007). Thus, if prolonged orthodontic tooth movement is planned, the definitive obturation and a well-sealed coronal restoration should be placed as soon as possible (Rosenberg et al., 2007), unless the calcium hydroxide is being used for apexification or disinfection. If a tooth is already well sealed with gutta percha and shows no signs of periapical radiolucency, no further root canal treatment is required (Hamilton and Gutmann, 1999). Tooth movement does not appear to impede the apexification process if a calcium hydroxide dressing has been placed (Steiner and West, 1997), and neither does it prevent periapical healing in animal models. It does delay the overall healing process, however, as shown in a dog study where 30 periapical lesions were created, followed six months later by root canal treatment of 20 of the teeth (the remaining ten were untreated controls). Ten teeth were then orthodontically moved, with the other ten used as comparisons. Both groups showed signs of healing, with the orthodontically moved teeth showing a slight delay, but no hindrance of the healing process (de Souza et al., 2006). Tooth isolation with a dental dam may be difficult due to the presence of bands and wires, and so root canal treatment may involve coordinated appointments with the orthodontist and general dentist or possibly the endodontist and/or paediatric dentist. Individualised adaptations of clamps and other retentive devices may be necessary to ensure that an adequate seal is achieved. Lingual orthodontic brackets can pose a problem when an access cavity is required, with one means to gain access being via the incisal edge (LaTurno and Zillich, 1985). It may be simpler and quicker to de-bond the tooth and replace the bracket following the endodontic appointment. Orthodontic treatment timing The severity of trauma affects the timing of orthodontic treatment. A post-trauma healing period for the periodontal ligament is highly recommended, so that no inflammatory stimulus can cause further damage to the protective cementum layer (Drysdale et al., 1996). A sound periodontal ligament is essential for orthodontic tooth movement (Wickwire, 1974), because this supporting tissue responds to the orthodontic forces placed upon the teeth; this, in turn, influences the osteoclastic and/or osteoblastic response leading to tooth movement. For teeth which have suffered mild-to-moderate trauma and have an intact periodontal membrane, it is suggested that a radiographic review to check for periapical pathology and root resorption be undertaken after four to five months, and prior to orthodontic tooth movement commencing (Malmgren et al., 1982). The orthodontic outcome for these teeth is generally expected to be similar to that for non-traumatised teeth (especially those with open apices), because the damage risk to the periodontal ligament is minimal (Andreasen et al., 2011). More severely traumatised teeth (such as those having suffered avulsion or extrusive luxation) undergoing orthodontic tooth movement have a poorer prognosis, especially if inflammatory or replacement root resorption occurs (Andreasen et al., 2011). A New Zealand Dental Journal March 2013 Orthodontic movement of teeth 7

3 rest period of at least one year is therefore recommended, in order to ensure that periodontal healing is complete and to avoid extra inflammatory stimuli, which may further damage the protective cementum layer and increase the risk of ankylosis (Kindelan et al., 2008). Mild damage to periodontal tissues (such as a concussion injury causing inflammation of the periodontal ligament) requires approximately three months of follow-up, whereas moderate damage requires twelve months of follow-up, in order to discount the possibility of ankylosis. Root fractures require an observation period of up to two years prior to orthodontic treatment, because the associated movement may contribute to the separation of segments (Zachrisson and Jacobsen, 1974; Kindelan et al., 2008). A case report on orthodontic movement of two maxillary central incisors which had sustained apical-third root fractures two years previously showed that tipping movements did not affect the vitality of the pulps, which were monitored at threemonthly intervals. There was also no increase in root fragment separation, despite the apical fragment angulation not closely following the angulation change in the coronal fragment. At the conclusion of treatment, the overjet had been reduced by 9mm and there was a slight reduction in vitality testing responses, but tooth mobility and colour were unchanged (Healey et al., 2006). Effect of orthodontics on root-canal-treated teeth There is very little literature on the orthodontic movement of root-canal-treated teeth, and most clinical recommendations are opinion-based. The consensus appears to be that root-canaltreated teeth can be moved as readily (and for the same distance) as vital teeth, providing ankylosis has not occurred (Huettner and Young, 1955; Spurrier et al., 1990; Mirabella and Artun, 1995). Normal force levels can be applied to root-canal-treated teeth during orthodontic tooth movement, providing the periodontal ligament is healthy. This was demonstrated in a retrospective study of endodontically-treated incisors using an untreated, vital contralateral incisor as control (Spurrier et al., 1990). Root-canaltreated teeth should be checked clinically and radiographically six months after orthodontic treatment commences, and, if there are signs of resorption, the patient should be informed and a rest period of three months observed before reassessment for further treatment (Andreasen et al., 2007). Traumatic intrusions treated via spontaneous eruption and/or orthodontic traction may lead to discrepancies in gingival height and incisal edge levels due to ankylosis (Flores et al., 2007a). There are conflicting reports in the literature on the risk of root resorption in root-canal-treated teeth during orthodontic treatment (Wickwire et al., 1974; Spurrier et al., 1990). This may be due to differences in pulp death aetiology, such as necrosis of the pulp due to periodontal disease, deep caries, or crown/root trauma that may be simple, complex, horizontal or vertical. These factors may not always be specified in studies, yet they can affect the outcome of orthodontic tooth movement. Orthodontically induced inflammatory root resorption (OIIRR) is a pathologic process due to localised injury of the periodontal ligament and resorption of cementum and dentine that occurs in conjunction with removal of hyalinised bone during tooth movement (Brudvik and Rygh, 1993). OIIRR occurs in most patients that undergo comprehensive orthodontic treatment, yet it is estimated that only 5% of these patients will experience more than 5mm of root shortening (Killiany, 1999), with permanent mobility of the coronal fragment expected when the root is less than 9mm in length (Levander and Malmgren, 2000). Despite this, the literature is yet to report the loss of a tooth due to OIIRR. Teeth with blunt or pipette-shaped roots subjected to heavy orthodontic forces (especially intrusive or tipping forces) are at a significantly greater risk than teeth with normally-shaped roots (Reitan, 1974; Levander and Malmgren, 1988). Thus, previously traumatised teeth with blunt apices may be at a higher risk (Levander and Malmgren, 1988). Conversely, it has been proposed that root-canal-treated teeth may be more resistant to root resorption (Spurrier et al., 1990; Bender et al., 1997). The hardness and density of dentine may be greater (Brezniak and Wasserstein, 1993), and this could render them more resistant to the resorption process (Graber and Swain, 1985). Bender and co-workers (1997) have suggested that another explanation may be the lack of neuropeptide release from pulpal tissue which would cause inflammatory reactions that contribute to root resorption. Recently, a small retrospective study compared 16 traumatised maxillary central incisors with vital controls. All had undergone orthodontic treatment for at least 20 months and had intact periodontal ligaments, with the root canal treatment undertaken at least one year prior to tooth movement commencing. Upon completion of orthodontic tooth movement, comparison of preand post-treatment periapical radiographs found no difference between the two groups in apical resorption (Esteves et al., 2007). If external apical root resorption of previously root-canaltreated teeth occurs during or after orthodontic tooth movement, the integrity of the apical seal may be violated. However, it is believed that the seal should not be compromised if the root canal has been adequately cleaned, shaped and obturated (Hamilton and Gutmann, 1999). In the clinical setting (as stated above), this means that previously root-canal-treated teeth can be moved as easily and as far as non-root-canal-treated teeth, providing there has been no ankylosis from previous trauma. It also means that those teeth are not more prone than vital teeth to root resorption, as long as the roots are of normal shape. Clinicians must ensure that a thorough informed consent process is undertaken when orthodontically treating traumatised or root-canal-treated teeth to ensure that patients and their parents are aware of possible sequelae. Orthodontic movement of apicected teeth Little is known about the potential problems and long-term prognosis of moving teeth which have had previous endodontic surgical intervention (Hamilton and Gutmann, 1999). Early application of orthodontic force following an apicectomy has been shown to delay the healing process, through the tooth mobility impacting on the ossification process (Baranowskyj, 1969). Periapical lesions should show good radiographic healing one year following apicectomy treatment. If a radiolucency persists, further endodontic attention is required (Drysdale et al., 1996). Orthodontic extrusion In some clinical situations, orthodontic extrusion is required to allow functional restoration of a tooth. Such cases include fracture of the tooth below bone level, subgingival carious margins on teeth requiring root canal treatment, and resorptive perforations (Hamilton and Gutmann, 1999). The objective of orthodontic extrusion in such cases is to expose a sound tissue margin for future restoration, and to prevent violation of the biologic width (Hamilton and Gutmann, 1999). An example might be orthodontic extrusion combined with crown lengthening surgery prior to restoration of a traumatised incisor. 8 Orthodontic movement of teeth New Zealand Dental Journal March 2013

4 Many procedures have been suggested for extrusion. For example, following a fracture of a maxillary incisor below bone level, a pulpectomy is performed and root filling placed, followed by the cementation of a post. A sectional archwire is then attached to orthodontic brackets on adjacent anterior teeth, with twist-flex wire attached to lightly extrude the apical segment over approximately four weeks. This is followed by retention for approximately six weeks to stabilise the periodontal fibres. Finally, after cementation of the final crown, a removable retainer should be worn for six months to further stabilise the periodontal fibres and prevent re-intrusion (Heithersay, 1973). Biggerstaff and colleagues (1986) suggested that 20-30g of extrusive force results in eruption with new crestal bone which, when combined with biologic width realignment, may lead to a better aesthetic outcome than that attainable with crown lengthening procedures alone. Autotransplantation Autotransplantation of premolars can be used to treat premolar agenesis, extraction spaces due to the removal of teeth of poor prognosis, or the traumatic loss of anterior teeth. This involves extraction of the premolar and its transplantation into a surgically prepared socket elsewhere in the mouth. It can be a useful shortterm treatment to provide an aesthetic, functional tooth and may be used to preserve bone levels in a growing patient until an implant can be placed if or when the autotransplant fails. Andreasen and colleagues studied 370 autotransplanted premolars in 289 patients and observed that only three teeth were subsequently extracted; two extractions were due to external root resorption and one resulted from the non-eruption of the transplanted tooth germ (Andreasen et al., 1990a; Andreasen et al., 1990b; Andreasen et al., 1990c). Tooth survival rates (irrespective of whether the tooth required subsequent root canal treatment) up to 13 years post-transplantation were over 95% in both teeth with incompletely formed roots and in those with completely formed roots. A high survival rate (98%) was also shown in a 17-year follow-up of 40 consecutive patients with autotransplanted premolars (Jonsson and Sigurdsson, 2004). Damage to the periodontal ligament during the procedure (through accidental severance or compression) can lead to root resorption, which can be diagnosed radiographically and/ or clinically four to eight weeks after autotransplantation. Subsequent orthodontic treatment of such teeth with complete root development resulted in a slight increase in the occurrence of both surface and inflammatory root resorption (Andreasen et al., 1990c). Further clinical studies have shown that mature teeth with closed apices can be autotransplanted with good success, providing that root canal treatment is commenced within 7-14 days of the surgery in order to prevent inflammatory root resorption due to pulp necrosis (Day et al., 2008). Teeth with an apical foramen narrower than 1mm in diameter should be carefully monitored. Autotransplanted teeth have been shown to be successfully moved, because they heal with a functional periodontal ligament (Trope, 2002) and may provide an often overlooked treatment option in hypodontia cases requiring orthodontic treatment. Orthodontic tooth movement following autotransplantation should start approximately eight weeks after surgery, once the periodontal ligament has healed, but prior to complete alveolar healing. Orthodontic treatment must be aimed at minimising any inflammatory stimuli which could damage the root surface during healing (Day et al., 2008). Conclusions When considering the endodontic-orthodontic case, the clinician must consider the prognosis of any compromised tooth. Treatment considerations include the quality of previous root canal treatment, the health of the periodontal membrane, and making provision for careful application of orthodontic forces. Even if a root-canal-treated tooth has a poor prognosis, the clinician may choose to continue treatment to ensure a favourable base for future autotransplant or implant treatment. From the evidence available, there seems to be no clinically significant difference in root resorption during orthodontic tooth movement between root-canal-treated teeth and vital teeth. However, if root canal treatment is required subsequent to trauma, an observation period, to monitor pulp and periodontal healing, of three months (in cases of mild trauma) or up to two years (where there has been severe trauma) should be allowed prior to orthodontic tooth movement. Root-canal-treated teeth can be moved orthodontically to the same extent as vital teeth, providing force levels are controlled to avoid the risk of inflammatory root resorption. Good clinical and radiographic assessment is important prior to planning any orthodontic treatment. Informed consent is also important. To ensure the best treatment outcome, it is essential to have good interdisciplinary communication with the orthodontist, endodontist, general dentist and/or paediatric dentist. References American Association of Endodontists (2012). Glossary of Endodontic Terms. 8th ed. Chicago, IL: American Association of Endodontists (pages 4, 45). Andersson L, Blomlöf L, Lindskog S, Feiglin B, Hammarström L (1984). Tooth ankylosis: clinical, radiographic and histological assessments. Int J Oral Surg 13: Andersson L, Andreasen JO, Day P, Heithersay G, Trope M, DiAngelis AJ et al. (2012). 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5 Andreasen JO (2003). Traumatic dental injuries : a manual. 2nd ed. Malden, MA: Blackwell Munksgaard, (page 35). Andreasen JO, Andreasen FM, Andersson L (2007). Textbook and color atlas of traumatic injuries to the teeth. 4th ed. Oxford, UK ; Ames, Iowa: Blackwell Munksgaard, (pages ) Andreasen JO, Bakland LK, Flores MT, Andreasen FM, Andersson L (2011). Traumatic dental injuries : a manual. 3rd ed. Chichester, West Sussex, U.K.: Wiley-Blackwell, (pages 12, 29, 35, 63, 72) Baranowskyj GR (1969). A histologic investigation of tissue response to an orthodontic intrusive force on a dog maxillary incisor with endodontic treatment and root resection. Am J Orthod 56: Bender IB, Byers MR, Mori K (1997). Periapical replacement resorption of permanent, vital, endodontically treated incisors after orthodontic movement: report of two cases. J Endod 23: Biggerstaff RH, Sinks JH, Carazola JL (1986). 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Eur J Orthod 10: Levander E, Malmgren O (2000). Long-term follow-up of maxillary incisors with severe apical root resorption. Eur J Orthod 22: Majorana A, Pasini S, Bardellini E, Keller E (2002). Clinical and epidemiological study of traumatic root fractures. Dent Traumatol 18: Malmgren O, Goldson L, Hill C, Orwin A, Petrini L, Lundberg M (1982). Root resorption after orthodontic treatment of traumatized teeth. Am J Orthod 82: Mirabella AD, Artun J (1995). Prevalence and severity of apical root resorption of maxillary anterior teeth in adult orthodontic patients. Eur J Orthod 17: Rafter M (2005). Apexification: a review. Dent Traumatol 21:1-8. Reitan K (1974). Initial tissue behavior during apical root resorption. Angle Orthod 44: Orthodontic movement of teeth New Zealand Dental Journal March 2013

6 Rosenberg B, Murray PE, Namerow K (2007). The effect of calcium hydroxide root filling on dentin fracture strength. Dent Traumatol 23: Rotstein I, Engel G (1991). Conservative management of a combined endodontic-orthodontic lesion. Endod Dent Traumatol 7: Spurrier SW, Hall SH, Joondeph DR, Shapiro PA, Riedel RA (1990). A comparison of apical root resorption during orthodontic treatment in endodontically treated and vital teeth. Am J Orthod Dentofacial Orthop 97: Steiner DR, West JD (1997). Orthodontic-endodontic treatment planning of traumatized teeth. Semin Orthod 3: Trope M (2002). Root resorption due to dental trauma. Endodontic Topics 1: Wickwire NA, Mc Neil MH, Norton LA, Duell RC (1974). The effects of tooth movement upon endodontically treated teeth. Angle Orthod 44: Zachrisson BU, Jacobsen I (1974). Response to orthodontic movement of anterior teeth with root fractures. Trans Eur Orthod Soc 50: Authors Victoria Beck BDS Suzan Stacknik DDS, MS Discipline of Orthodontics, School of Dentistry, University of Otago; PO Box 647, Dunedin, New Zealand. Nicholas P. Chandler BDS (Lond), MSc (Manc), PhD (Lond), LDSRCS (Eng), FDSRCPS (Glas), FDSRCS (Edin), FFDRCSI Department of Oral Rehabilitation, School of Dentistry, University of Otago; PO Box 647, Dunedin, New Zealand Mauro Farella DDS, Dottore di Ricerca, SpecOrthodontics, SpecMedStat Discipline of Orthodontics, School of Dentistry, University of Otago; PO Box 647, Dunedin, New Zealand. Address correspondence to: Victoria Beck, Sir John Walsh Research Institute, School of Dentistry, University of Otago, PO Box 647, Dunedin, New Zealand. becvi843@student.otago.ac.nz Why publish? in the New Zealand Dental Journal The Journal is an internationally-recognised, fully peer-reviewed publication. It directly reaches well over 90% of New Zealand dentists, as well as an international audience. The Journal has a policy of nurturing talented new researchers and authors. It is indexed in MEDLINE, PubMed and other highlysearched data-bases. Unrestricted dissemination of electronic PDF versions of your article. The availability of colour illustrations. Your work will contribute to the vitality, rigour and development of the dental profession in New Zealand. New Zealand Dental Journal March 2013 Orthodontic movement of teeth 11