Recovery bone formation over radiographic lingual bone dehiscence after mandibular molar distalization with microimplants.

Objectives: To assess mandibular lingual bone thickness changes after molar distalization with microimplants and during retention.

Materials and methods: Twenty-one patients (10 men, 11 women; mean age: 20.5 ± 4.9 years) who underwent mandibular molar distalization with microimplants were included. Cone-beam computed tomography images at pretreatment (T0), posttreatment (T1), and retention (T2) were used to measure posterior space available and lingual bone thickness distal to the mandibular second molar at 0-, 2-, 4-, and 6-mm levels apical to the root furcation. Repeated measures analysis of variance with Bonferroni correction was applied to compare T0, T1, and T2 measurements. Pearson's correlation analysis assessed the relationship between lingual bone thickness change and other variables.

Results: The mandibular second molar moved distally by 3.0 mm at crown level, and 1.2-1.8 mm at root level, after treatment. Posterior space available decreased significantly with root-cortex contact or radiographic lingual bone dehiscence observed at 6-mm root level. After retention, reduced cortical bone thickness increased significantly; however, T2 lingual bone thickness was less than T0. Although the decrease in lingual bone thickness at 6-mm root level correlated with crown and root distal movement after treatment, the increase in bone thickness during retention was not associated with tooth movement, patient age, or retention duration.

Conclusions: Mandibular lingual bone thickness noticeably decreased after molar distalization with microimplants. After retention, significant bone recovery formation was observed at the thinned lingual cortex or radiographic bone dehiscence.