A new 2-dimensional method for constructing Visualized Treatment Objectives for distraction osteogenesis of the short mandible

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Summary

Open bite development during distraction of the mandible is common and partly due to inaccurate planning of the treatment. Conflicting guidelines exist in the literature. A method for Visualized Treatment Objective (VTO) construction is presented as an aid for determining the correct orientation of monodirectional and multidirectional distractors. Distraction on the left and on the right side of the mandible takes place in a parallel manner in order to maintain intercondylar width. It follows that in the absence of marked asymmetry, the amount of mandibular body distraction, the amount of ramus distraction and (should it apply), the amount of closure of the gonial angle, can be derived from a simple 2-dimensional plan. After presurgical orthodontic treatment, a cephalogram is taken and a VTO is constructed, that aims at a good occlusion with the enhanced mandible in centric relation, with little or no change of the original position of the rami.

Introduction

Distraction osteogenesis of the mandible has a proven value in the treatment of severe craniofacial deformities. A myriad of distractor types is used. There are monodirectional, bidirectional, multidirectional and curvilinear distractors and distinction is made between extra-oral and intra-oral devices (Fig. 1). There are tooth-borne, bone-borne and hybrid distractors to gain mandibular length, dental arch length, or to widen the dental arch in the midline (Samchukov et al., 2001a, Samchukov et al., 2001b). Special distractors exist for ramus or body distraction. Currently, distraction is also applied to lengthen a short mandible in non-syndromic patients, as an alternative to a bilateral sagittal split osteotomy (BSSO). For this, monodirectional distractors are most commonly used, either for body lengthening, ramus lengthening or both. Proposed advantages would be: less nerve damage, fewer joint problems, greater advancement possibilities, better soft tissue adaptation and less relapse (Samchukov et al., 2001). All these advantages still require solid evidence, but the interest in the procedure seems to be growing (Peltomäki et al., 2002, Breuning et al., 2004a, Breuning et al., 2004b). Distraction osteogenesis of the mandible in Hemifacial Microsomia is deemed good practice, although some still doubt exists (Mommaerts and Nagy, 2002, Batra et al., 2006), but mandibular distraction in the non-syndromic patient is more controversial (Schreuder et al., 2007). In a recent extensive European survey, reported in this journal, a wide variety in treatment approaches to craniofacial anomalies was noted and disagreement with regard to ideal age for treatment, surgical technique, distraction device and retention period was pronounced (Nada et al., 2009). Consensus has been reached, though, on one serious disadvantage during distraction of a short mandible in non-syndromic patients: there is a strong tendency toward open bite development and facial height increase, to be counteracted only partly by strong intermaxillary elastics or a chin cup. For this reason, some clinicians prefer bidirectional or multidirectional distractors. Closure of the gonial angle might help to prevent an open bite. Still, functional and anatomical factors (tongue thrust, geniohyoid muscle traction) combined with flexibility of the distractors, render distraction less suitable for the open bite, long face patient (Breuning et al., 2004a, Breuning et al., 2004b). Sturdy distractors do not seem to solve the problem (Hoffmeister and Wangerin, 1997). However, it might be that incorrect placement of the device and the resulting direction (vector) of separation of the segments is to blame. In the literature, conflicting guidelines are presented without discussion (Grayson et al., 1997, Grayson and Santiago, 1999, Samchukov et al., 1999, Rubio-Bueno et al., 2001).

A cephalometric set-up or Visualized Treatment Objective (VTO) that is indispensable for the planning of orthognathic surgery is usually noticeably absent for mandibular advancement by distraction. With few exceptions, the planning of mandibular distraction is absent or poor with regard to distraction vectors. Since the treatment of severe facial convexity and open bite tendency is complex in any approach, it seems worthwhile to try and find possible solutions to this drawback of mandibular lengthening by distraction, that otherwise appears to be an effective procedure.

Section snippets

Open bite and mandibular distraction

An inventory was made of the most relevant factors that lead to open bite during distraction of the mandible.

In the literature, very few articles were found that address the vectors of mandibular distraction (Losken et al., 1995, Grayson et al., 1997, Grayson and Santiago, 1999, Gateno et al., 2000, Rubio-Bueno et al., 2001, Scolozzi et al., 2007). Open bite development during mandibular distraction is encountered by most authors and the origin is considered to be multifactorial. Apart from the

Discussion

Mandibular lengthening by distraction osteogenesis might have advantages over BSSO (less nerve damage, less joint problems, greater advancement possibilities, better soft tissue adaptation and less relapse). Moreover, mandibular distraction in non-syndromic patients could be applied to individuals that are still growing since the growth potential of the mandible in these patients is expected to be normal (Baccetti et al., 2009). However, problems arise in the same category of patients that is

Conclusions

  • Open bite development is a problem during mandibular distraction osteogenesis.

  • Intermaxillary elastics provide little control.

  • Deep bite cases are the least problematic.

  • Sturdy distractors that increase ramus height may alleviate the open bite problem.

  • High quality Presurgical Orthodontics to coordinate the arches is needed.

  • Fully adjustable distractors are no substitute for distraction planning.

  • For non-syndrome cases, a simple 2-dimensional VTO is probably sufficient, both for monodirectional and

References (23)

Cited by (2)

  • Maxillary-driven simultaneous maxillo-mandibular distraction for hemifacial microsomia

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    This can cause social problems, particularly for children and adolescents who may experience social problems at school during active treatment (Scolozzi et al., 2006; Padwa et al., 1999). To overcome these problems, small internal distraction devices have been developed and used (Satoh et al., 2002; Padwa et al., 1999; Scolozzi et al., 2006; van Beek, 2010). There is evidence in the literature that combined maxillo-mandibular distraction can be performed using two independent distractors (Scolozzi et al., 2006).

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