DOI: 10.1051/odfen/2015020 J Dentofacial Anom Orthod 2015;18:405 © The authors

Retained second molars: therapeutic approach

J. Vexiau1, B. Castaneda2,3,4 1 Dental surgeon, CECSMO 4 Paris VII, Pitié-Salpêtrière Hospital Group 2 Dentofacial Orthopedics Dept., Paris, France 3 Laboratory of Molecular Oral Pathophysiology, INSERM UMR 1138, Paris, France 4 Faculty of Odontology, University of Antioquia, Colombia

ABSTRACT Second eruption abnormalities are quite rare, and thus there is no precise consensus protocol for their setting. Several therapeutic solutions will be presented here: purely orthodontic, or associating orthodontics and surgery.

KEY WORDS Permanent second molar, primary failure of eruption, mechanical failure of eruption, treatment of retained molars

INTRODUCTION

Second molar eruption abnormality is In case of MFE, or when a diagnosis of fairly rare, but seems to be slightly increas- PFE is uncertain, several solutions may be ing (1% according to Cho, 20083). Several considered: orthodontic or surgical treat- etiologies have been suggested. Locally, a ment, a combination of the two, or absten- trend away from extraction and tion. Conversely, if the diagnosis of PFE is in favor of space-maintaining treatments certain, surgery is preferable, associated to could partly explain the increase14. orthodontic treatment or not. Various treatments are available for sec- Other factors are to be taken into account ond molar eruption pathology. Etiology in guiding treatment (see below). plays a role in determining treatment. As these abnormalities are not widespread, Primary failure of eruption (PFE), de- there is no well-defined therapeutic proto- fined by Proffit in 198112, is to be dis- col. Various solutions have been described: tinguished from mechanical failure of orthodontic, or combining orthodontics and eruption (MFE), defined by Suri in 200216. surgery, as with miniscrews or miniplates. Diagnosis, however, is often difficult, Although based on simple case reports or still and it is often attempted to position the in the experimental stages, they will be pre- retained . sented here, to help clinicians in their practice.

Address for correspondence: Article received: 3-05-2015. Juliette Vexiau – CECSMO4 Pitié-Sapêtrière, Accepted for publication: 1-06-2015. Bâtiment d’Odonto-Stomatologie 47-83 Boulevard de l’Hôpital This is an Open Access article distributed under the terms of the Creative Commons Attribution 75013 Paris, F rance License (http://creativecommons.org/licenses/by/4.0), E-mail: juliette. [email protected] which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1

Article available at https://www.jdao-journal.org or https://doi.org/10.1051/odfen/2015020 J. VEXIAU, B. CASTANEDA

FACTORS INFLUENCING THERAPEUTIC DECISION-MAKING

Retention is diagnosed on several dental apex), tooth inclination, pres- criteria, including progression of the ence of adjacent third molar, associ- contralateral tooth or occlusal level of ated first molar retention, intra-oral the second as compared to the first visibility, etc. molar if the tooth has emerged into The type of bone tissue around the the oral cavity without meeting the tooth also plays a part in choice of first molar occlusion plane. treatment: teeth retained or impact- Treatment is guided by several fac- ed in the are surrounded by tors, depending on patient age, root much denser bone tissue than in the edification stage (open or closed .

ORTHODONTIC SOLUTIONS

Many authors have described a Moreover, most reports concerned variety of means of positioning re- second molars in mesial inclination, tained or impacted second molars in although this is far from being the the arcade. Surgical exposure is usu- most frequent state of affairs (Fig. 1). ally required, to allow a button, tube Before detailing the various sys- or hook to be attached for traction. tems for setting retained or impacted In most cases, and especially in the second molars, some biomechanical mandibular arcade, the adjacent third reminders will be given. molar, when present, is extracted. When distalizing force is applied to There have been many more a mesially inclined molar, this induces reports of retained or iimpacted man- a momentum leading to distal ver- dibular than maxillary second molars. sion of the tooth. Figure 2 shows that

Figure 1 Panoramic view: Angélique, 15 years old. Class II divi- sion 1 associated with retention of mesially inclined Figure 2 mandibular second molars at an angle >25° to the Distalizing and extrusive force applied by the ortho- first molar axis (Thanks to Dr Sylvie Legris). dontic system, with anti-clockwise rotation.

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the force applied by the orthodontic moment tending to upright the mesi- system sets up an anti-clockwise ally inclined tooth; fixing the tube at moment that uprights the mesially 90° creates a much stronger moment inclined tooth; this also induces egres- and greater uprighting displacement. sion, which may need controlling. During treatment, the straight arch Lau et al.6 described what they does not include the first molar, so as called “routine” straight arch tech- to increase the flexibility of the arch niques for setting mesially inclined and reduce force so as to avoid un- retained mandibular second molars: wanted effects such as root resorp- after surgically releasing the dis- tion or problems at the attachment. tal side of the tooth, they insert an The authors add that the posterior compressed open spring between maxillary occlusion planes had to the first and second molars, with the be raised to enable molar uprighting tube glued to the latter at 90° to the without occlusal interference. In this occlusal plane so as to promote up- case, this did not impair the results of righting. If the tube were glued paral- treatment. lel to the occlusion plane, the tooth Elastic bands (e.g., criss-cross) would basically move backward, and may be used as back-up to complete the distalization force would induce a occlusion of the repositioned second molar. Elevation planes on the posterior teeth may, in some patients, espe- cially those with facial hyperdiver- gence, induce unwanted mandibular opening and/or gap.

Figure 4 Below, occlusal view of ring with welded spring and Figure 3 custom-made hook; above, occlusal view of system a) 37 and 47 retained despite extraction of 34 and 44. in position, with ring fixed to the molar mesial to the b) 8 months later, 37 and 47 well-positioned in the tooth to be uprighted, hook glued to tooth to be arcade. (Thanks to Dr Sylvie Legris). uprighted and spring in position.

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Ziegler18 likewise reported a sys- arcade, with a .016 × .022 or .019 × tem using a compressed open spring .025 steel bracket, depending on the between the first mandibular molars type of attachment. The reported cas- and the second, mesially inclined in es did not involve third molar germec- retention, onto which an attachment tomy to upright the second molar. system was fitted. He called this Another example concerns a young “versatile molar uprighting mechan- patient presenting with dentomaxil- ics” and developed it over a period lary dysharmony and retained second of some 15 years, ending up with a molars, managed by extraction of the system using self-ligating brackets. first maxillary and second mandibular A sectional bracket is placed be- . Resolution of posterior tween the first molar and the second crowding allowed spontaneous pro- molar, to be uprighted, (or between gression of both second molars. In the second and third, as Ziegler also other cases of dentomaxillary dys- applied this system for third molars), harmony, premolar extraction is not and a compressed screw uprights the enough to enable spontaneous pro- mesially inclined molar. In one of his gression. Such, for example, was the cases, like Lau et al., he did not include case of the patient shown in Figure 1, the first molar to help upright the sec- with retained second molars. ond. Anchorage involved the whole The first premolars were extracted. The second mandibular molars were in retention, but with the distal part of the vestibular side accessible, and could be managed by glued minitubes and a .014 copper NiTi arch. In a second step, a .018 steel arch with coiled loops was fitted between the first and second molars. This type of system has the same effect as a spring, but with better mechanical control. The entire arcade is included, Figure 5 ensuring anchorage while the second Modified Loca system. molars are uprighted (Fig. 3a and b).

Figure 6 Figure 7 Sawicka technique. a) Santoro et al., lingual view: b) occlusal view.

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Miao et al.8 and Ma et al.7 described that .019 × .025 steel would be better a technique applied essentially for than the .020 Australian wire, to opti- mandibular third molars but also mize anchorage and minimize sometimes successfully for mandib- vestibular drift. ular second molars (Fig. 4). Sawicka et al.14 described a system Miao et al. fitted a custom-made initially including just the mandibular hook to the molar to be repositioned, incisor-canine sector and 2 TMA sec- with a ring on the adjacent tooth and tional brackets fixed distally to the a .018 steel spring welded to the ring; canines and linked to the 2 mesially the spring exerted a distalizing but also inclined molars, creating a strong le- slightly extrusive force on the tooth. ver arm (Fig. 6). The 6 anterior teeth Ma et al. fitted a custom-made support a .017 × .025 steel sectional hook to the tooth to be uprighted bracket in .018 grooves; a figure-of- after surgical exposure; a ring with eight ligature connects them, and a .016 steel spring was fixed to the anchorage is completed by a glued adjacent molar, intended to exert a contention. Once the molars have be- purely distalizing force. In a second gun to straighten, the entire arcade is step, the tooth was extruded using included. a .017 x .025 TMA sectional bracket, Bach1 described a technique in with .019 × .025 steel anchorage on which a .013 copper NiTi arch is in- the 4 teeth anterior to the tooth to be serted distally, with a loop to the uprighted. Finally, the position of the tube on the adjacent tooth. This dis- tooth was adjusted. The technique tal insertion is intended to exert both was reported for third molars requir- distalizing and intruding force on the ing uprighting ahead of extraction, tooth, whereas many other systems but was also successfully used on that have been reported exert an ex- some mandibular second molars. truding force (which accounts for the Loca’s system, modified (Celli need for elevation planes on the pos- et al.2), and another system described terior teeth to enable distal rotation by Paik et al.10 use an NiTi arch with of the second molar, but with a risk of extra wire; as it tries to recover its ini- creating a gap, as mentioned above). tial shape, the arch uprights the molar Santoro et al.13 described a more (Fig. 5). This again concerns retained original system (Fig. 7a and b) using mandibular second molars with a commercial transpalatal bar modi- mesial inclination. fied to fit in a palatine/lingual sheath In the modified Loca system, an and to reach the distal side of the NiTi sectional bracket is positioned retained second molar. A chain con- between the first and second mo- necting the button to the hook on lars and the whole arcade, except the modified transpalatal bar enables the second molars to be uprighted, distalizing traction. Anchorage is pro- is included by a distally curved .020 vided by including the entire arcade Australian wire, and a glued lingual with a steel arch. The system is thus contention reinforces the anchor- said to be applicable to both maxilla age and focuses force on the molar and mandible, although the reported to be uprighted. The authors specify cases concerned mandibular molars.

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As there are few examples con- first molar, associated to orthodontic cerning maxillary molars in the lit- treatment. Such was the case for a erature, some unpublished cases of young patient presenting with a right treatment of retained maxillary sec- in occlusion ond molars will be described. and the left retained under the distal A patient presenting with a retained convexity of the first molar (Fig. 9a). maxillary second molar underwent Mucosal release was performed, surgical exposure of the occlusal side with reduction of first molar distal of the tooth, to which a tube was enamel. A minitube was fixed onto glued. A .017 × .022 sectional bracket 27, for intermaxillary traction. with blue elgiloy loops was positioned As the effect was insufficient, a to achieve occlusal traction, exert- sectional bracket was positioned ing a mainly extrusive force (Fig. 8a from the second premolar to the sec- and b). As soon as clinically possible, ond molar, with a compressed spring a tube was glued onto the vestibular to distalize the tooth, associated to side, with a sectional bracket to the gentle dislocation (Fig. 9b). The an- first molar including the tooth under chorage was reinforced by a transpal- traction (Fig. 8c). The atal Nance appliance linking the right germ was not removed at first, in to left second case there was ankylosis; once trac- premolar. A triangular vertical elastic tion had proved successful, germec- band was associated, so that egres- tomy was performed. sion was limited to the second molar, Setting a maxillary second molar without ingression of the first molar may in some cases require slight dis- (Fig. 9c). Egression was progressive, tal enamel reduction on the adjacent without side-effects (Fig. 9d and e).

SOLUTIONS COMBINING ORTHODONTICS AND SURGERY

Surgery may be considered: gentle applied directly by the miniscrew, dislocation (notably in PFE, where the which is in other cases used to rein- risk of ankylosis is high), or extraction force anchorage. if tooth positioning seems too com- In impacted or retained mandibular plicated or impossible. second molars, a miniscrew is often In other cases, treatment may as- fitted in the retromolar region, for sociate orthodontics to miniscrews tooth traction. or miniplates, or to dislocation. Nanda9, for example, described trac- tion of a Miniscrews and orthodontics impacted horizontally behind the first molar, using a bracket-headed minis- Many authors have reported use of crew in the retromolar region, with a miniscrews in impacted or retained button glued to the distal side of the sec- second molars. Traction is usually ond molar (the only accessible side at

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Figure 8 a, b) Traction of 17 by a tube glued to the occlusal side and a .017 x .022 sectional bracket with blue elgiloy loops. c) A tube is glued to the vestibular side, with a sectional bracket to the first molar including the tooth under traction. (Thanks to Dr A. Birgy).

Figure 9 a) Panoramic view, showing impaction of 27. b) Sectional bracket and spring to distalize 27. c) Trian- gular elastic to avoid side-effects on adjacent teeth. d and e) Progressive egression of 27: occlusal and lateral views. (Thanks to Dr S. Legris).

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Exposure and dislocation associated to orthodontics A 19 year-old patient presented with a totally edified right maxillary molar, without progression at end of ortho- dontic treatment; the adjacent third molar was extracted following itera- tive infection, but this did not enable spontaneous eruption of the second Figure 10 molar (Fig. 11a). Nanda device. Surgical exposure was associated to dislocation. At the time of writing, this stage) and a cantilever mechanism the tooth was under traction with between the miniscrew and an elastic a sectional .016 × .016 copper NiTi traction band connecting with the sec- overlay bracket, with anchorage by ond molar button (Fig. 10). a .018 × .025 steel sectional bracket Park et al.11 reported using a minis- (.022 × .028 attachments) connect- crew in the maxillary tubercle to up- ing the two premolars and the first right a maxillary second molar; but molar, plus a transpalatal arch fixed in their case the adjacent first molar to the two first premolars F( ig. 11b). was absent. This type of treatment, associating Sohn et al.15 stressed the drawbacks orthodontic traction to surgical dis- of applying distal force on the tooth to location of the suspected ankylosis be positioned: patient discomfort, and region, was described by Dr Cohen- poor efficacy of the system, which can Lévy4. rarely be applied to the maxilla. They recommended an alternative, using a miniscrew between the second pre- molar and first molar, fixed by a .016 × .022 steel wire and composite. The miniscrew serves as anchorage rather than for traction.

Miniplates and orthodontics Tseng et al.17 used a miniplate for trac- tion of a severely impacted mandibular second molar. Miniplates are harder to fit than miniscrews, and should be re- served for more complex cases in which miniscrews alone would not allow the impacted tooth to be positioned. Figure 11 Bone anchorage is of great interest, a) Cone-beam CT slice of impacted 17. b) Traction avoiding parasitic ingression in case of 17 by .016 x .016 copper NiTi sectional bracket. of ankylosis. (Thanks to Dr Sylvie Legris).

8 Vexiau, J. Castaneda B. Retained second molars: therapeutic approach RETAINED SECOND MOLARS: THERAPEUTIC APPROACH

Orthodontics after surgical setting for example, unduly lingual or vestib- ular positioning5; classic multibracket In some cases, orthodontic treat- systems, partial or otherwise, may ment is needed after surgery to correct, then be used.

CONCLUSION

The relatively low frequency of sec- being fully aware of the effects of the ond molar eruption disorder explains mechanical system used. Close mon- why treatment is so poorly standard- itoring is essential. Any tooth show- ized, without any large-scale studies. ing signs of ankylosis can thus be The present article shows the diver- detected before inducing side-ef- sity of methods: orthodontic and as- fects, which could be non-negligible sociated orthodontic/surgical, each and difficult to manage subsequently. with its advantages and drawbacks. The importance of good anchor- Conflicts of interest age should be kept in mind, to avoid The authors declare no conflicts of and anticipate parasitic movements, interest.

REFERENCES

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