Three-dimensional assessment of mandibular advancement 1 year after surgery

The three-dimensional evaluation of positional change in mandibular condyle after intraoral vertical ramus osteotomy

OBJECTIVES

The purpose of this study was to compare the changes of the condylar axis, the anteroposterior condylar position relative to the glenoid fossa, after intraoral vertical ramus osteotomy (IVRO).

STUDY DESIGN

21 patients diagnosed as skeletal class III malocclusion underwent IVRO and were followed according to the authors' postoperative management regimen. The three-dimensional positions of the condyles were evaluated by cone-beam computerized tomography (CBCT) at pre-op, post-op, and at follow-up. CBCT images were referenced to assess the condylar axis change and the anteroposterior condylar position in the glenoid fossa. A repeated-measures analysis of variance (P<0.05) also was performed.

RESULTS

After surgery, both the axial condylar angles and the anteroposterior condylar position were significantly different (P<0.05). The coronal condylar axis rotated outwardly. The anteroposterior condylar position in the glenoid fossa had moved from the concentric to the anterior position. But the condyle changes between post-op and follow-up (P>0.05) were insignificant.

CONCLUSIONS

With postoperative intermaxillary elastic traction, the condyles changed their positions physiologically for newly established jaw movement after IVRO.

Temporomandibular joint condylar changes following maxillomandibular advancement and articular disc repositioning

PURPOSE

To evaluate condylar changes 1 year after bimaxillary surgical advancement with or without articular disc repositioning using longitudinal quantitative measurements in 3-dimensional (3D) temporomandibular joint (TMJ) models.

METHODS

Twenty-seven patients treated with maxillomandibular advancement (MMA) underwent cone-beam computed tomography before surgery, immediately after surgery, and at 1-year follow-up. All patients underwent magnetic resonance imaging before surgery to assess disc displacements. Ten patients without disc displacement received MMA only. Seventeen patients with articular disc displacement received MMA with simultaneous TMJ disc repositioning (MMA-Drep). Pre- and postsurgical 3D models were superimposed using a voxel-based registration on the cranial base.

RESULTS

The location, direction, and magnitude of condylar changes were displayed and quantified by graphic semitransparent overlays and 3D color-coded surface distance maps. Rotational condylar displacements were similar in the 2 groups. Immediately after surgery, condylar translational displacements of at least 1.5 mm occurred in a posterior, superior, or mediolateral direction in patients treated with MMA, whereas patients treated with MMA-Drep presented more marked anterior, inferior, and mediolateral condylar displacements. One year after surgery, more than half the patients in the 2 groups presented condylar resorptive changes of at least 1.5 mm. Patients treated with MMA-Drep presented condylar bone apposition of at least 1.5 mm at the superior surface in 26.4%, the anterior surface in 23.4%, the posterior surface in 29.4%, the medial surface in 5.9%, or the lateral surface in 38.2%, whereas bone apposition was not observed in patients treated with MMA.

CONCLUSIONS

One year after surgery, condylar resorptive changes greater than 1.5 mm were observed in the 2 groups. Articular disc repositioning facilitated bone apposition in localized condylar regions in patients treated with MMA-Drep.

Three dimensional quantification of mandibular bone remodeling using standard tessellation language registration based superimposition

OBJECTIVE

The aim of this study was to evaluate a new method to quantify longitudinal mandibular bone remodeling three-dimensionally by superimposition of cone beam computed tomography images.

MATERIALS AND METHODS

This method is used to quantify the treatment effects of implant-retained overdentures in 20 patients aged 52-79 at recruitment after 1 and 2 years post treatment. Three dimensional models of pre- and post-treatment were reconstructed for each patient and superimposed using Standard Tessellation Language registration method and segmentation.

RESULTS

Color maps of the differences generated by superimposition allow detailed examination and quantification of the progressive dimensional changes of bone in a three-dimensional manner and enable the visualization of the apical displacement and thinning of the cortical layer of bone underneath the denture base. Most of the remodeling changes took place during the first year with a mean decrease in volume of 3.7% (SD = 4.4%; range = +3.7% to -15.9%, median = -3.7%). This remodeling pattern continued during the second year, but at a reduced rate of 2.5% per year (SD = 4.2%; range = +2.1% to -11.3%, median = -3.9%).

CONCLUSION

Standard Tessellation Language registration based superimposition of cone beam computed tomography images may be considered an objective and reproducible method to three-dimensionally quantify mandibular bone remodeling.