Long-Term Effects of Mandibular Distraction Osteogenesis

Distraction osteogenesis (DO) has become a reliable technique for correcting craniofacial deformities by skeletal expansion. Osteotomies and devices used for mandibular DO are often adjacent to developing or erupted teeth which can be displaced and/or damaged.¹  Few studies specifically characterize the effects of mandibular DO on the dentition.  In addition, controversy exists as to whether the distracted mandible continues to grow.²  The purpose of this study is to determine the effects of mandibular DO on the dentition and on subsequent mandibular growth in children.

This is a retrospective cohort study assessing all pediatric patients (<15 years old) in the Massachusetts General Hospital DO registry who underwent mandibular DO between 1998-2015.  Those with greater than 1 year follow-up post device removal and complete radiographic records were included. Adverse effects on the development, eruption, and morphology of the dentition were quantified by comparing panoramic radiographs at the following time points: pre-operative (T0), at device removal (T1), and longest follow-up (T2). 

Post-treatment mandibular growth was quantified by comparing lateral cephalograms at device removal (T1) with 1 year (T2) and longest follow-up (T3).  If the osteotomy had occurred in the mandibular body, gonion to gnathion was measured. For distraction of the ramus, articulare to gonion was measured. 

A total of  71 pediatric patients underwent DO during the study period. Twenty-five children with a mean age of 8.13±2.35 years met the inclusion criteria and were the subjects of the dentition assessment. Unresolved adverse effects on the dentition were present in 22/25 (88%) patients at the time of the longest follow-up (4.75±3.15 years).  Mandibular molars (36/86, 42%) in distraction areas were adversely affected by DO:  15 molars had damage to the crown or root at time of osteotomy; 10 first and second molars failed to erupt/develop normally; and 18 had increased space between the teeth.

Thirty subjects with a mean age of 8.94±3.04 years were included in the mandibular growth assessment with 12 and 18 subjects undergoing mandibular body and ramus DO, respectively.  After completion of mandibular body DO (T1, Table 1), there was relapse of 2.36±7.61 mm in mandibular body length at T2 (1.13±0.30 years) followed by an increase of 2.40±5.13 mm at T3 (5.37±3.14 years).  After mandibular ramus DO (T1, Table 2), there was relapse of 4.37±6.91 mm in mandibular ramus length at T2 (1.22±0.24 years) and an increase of 1.87±7.70 mm at T3 (7.16±3.70 years).

The results of this study suggest mandibular DO in children has adverse long-term effects on the developing dentition in proximity to the osteotomies and distractors. This study also suggests that after a period of relapse in elongation along the vector of distraction, there is continued growth of the both the mandibular body and ramus after DO. Patients and caregivers should be counseled about the risks of DO with regard to the developing dentition.

Table 1

Mandibular Body Distraction Osteogenesis
Measurement	T1-T0	T2-T1	T3-T1
Ramus Height	-1.65±2.77 mm	0.88±3.34 mm	1.41±3.87 mm
Mandibular Body Length	11.23±7.44 mm	-2.36±7.61 mm	2.40±5.13 mm
SNB Angle	5.11±4.60	-0.91±3.42	-2.91±7.04
Mandibular Unit Length	12.04±7.66 mm	-1.01±7.27 mm	3.34±6.08 mm

                

             Table 2

Mandibular Ramus Distraction Osteogenesis
Measurement	T1-T0	T2-T1	T3-T1
Ramus Height	9.25±7.44 mm	-4.37±6.91 mm	1.87±7.70 mm
Mandibular Body Length	1.47±7.44 mm	-0.21±6.92 mm	8.82±6.34 mm
SNB Angle	3.74±4.68	0.06±2.56	0.81±3.77
Mandibular Unit Length	9.62±7.17 mm	-2.61±4.69 mm	11.19±9.86 mm

1.  Da silva freitas R, Tolazzi AR, Alonso N, Cruz GA, Busato L. Evaluation of molar teeth and buds in patients submitted to mandible distraction: long-term results. Plast Reconstr Surg. 2008;121(4):1335-42.

2.  Al-daghreer S, Flores-mir C, El-bialy T. Long-term stability after craniofacial distraction osteogenesis. J Oral Maxillofac Surg. 2008;66(9):1812-9.