Effect of mandibular distraction osteogenesis on developing molars

Objective -To observe the effect of mandibular distraction osteogenesis (DO) on developing molars. Design - Descriptive clinical study. Setting - University hospital setting. Seventeen children (mean age 7.6 years) with various syndromes (hemifacial/craniofacial microsomia, Goldenhar syndrome, Treacher Collins syndrome, Nager syndrome and Pyle-Bakwin-Krida syndrome) participated. Experimental variable - Severely retrognathic lower jaws were distracted (mean 30 days) with an extraoral bicortically fixed DO device. Outcome measure - Consecutive panoramic tomograms were analysed after a mean follow-up period of 3.6 years, range 1-6.9 years. Results -The mandibular molars were affected by DO in 13 of the 17 patients which included 18 of 63 mandibular molars studied. Structural changes included root malformations, hindered tooth development and the destruction of tooth follicles. Positional changes such as shifted and tilted teeth were also found. Three injured teeth failed to erupt. These changes were because of splitting of the tooth follicle during the osteotomy (22%), piercing of the tooth follicle by the pin (39%) or migration of tooth germ towards the newly created bone (39%). Fifteen per cent of first molars, 43% of second molars and 31 % of third molars were affected during the distraction process. Of all dental injuries, 44% were noticed while the appliance was in place. A further 17% of injuries were noted between 3 months and 1 year postoperatively and 33% during the second postoperative year. Conclusions - Although dental injuries are a minor disadvantage compared with the vast benefits offered by DO, focusing on these drawbacks might lead to re-consideration of the type of the device as well as the timing of DO.