Reproducibility of asymmetry measurements of the mandible in three-dimensional CT imaging

Description of Mandibular Improvements in a Series of Infants With Congenital Muscular Torticollis and Deformational Plagiocephaly Treated With Physical Therapy

BACKGROUND

Many infants with congenital muscular torticollis (CMT) have deformational plagiocephaly (DP), and a small cohort also demonstrate mandibular asymmetry (MA). The aim of this retrospective study was to evaluate mandibular changes in these infants with previous computed tomography (CT) scans who underwent physical therapy (PT) to treat CMT.

METHODS

A retrospective study included patients presenting to a pediatric plastic surgery clinic from December 2010 to June 2012 with CMT, DP, and MA. A small subset of these patients initially received a 3D CT scan due to concern for craniosynostosis. An even smaller subset of these patients subsequently received a second 3D CT scan to evaluate for late-onset craniosynostosis. Patients were treated with PT for at least 4 months for CMT. Initial CT scans were retrospectively compared to subsequent CT scans to determine ramal height asymmetry changes. Clinical documentation was reviewed for evidence of MA changes, CMT improvement, and duration of PT.

RESULTS

Ten patients met inclusion criteria. Ramal height ratio (affected/unaffected) on initial CT was 0.87, which significantly improved on subsequent CT to 0.93 ( P < .05). None of the patients were diagnosed with craniosynostosis on initial CT. One patient was diagnosed with late-onset coronal craniosynostosis on subsequent CT.

CONCLUSIONS

We identified a small cohort of infants with MA, CMT, and DP. These patients uniformly demonstrated decreased ramal height ipsilateral to the affected sternocleidomastoid muscle. Ramal asymmetry measured by ramal height ratios improved in all infants undergoing PT.

Quantitative and perceived visual changes of the nasolabial fold following orthodontic retraction of lip protrusion

OBJECTIVES

The objectives of this study were to evaluate the quantitative and perceived visual changes of the nasolabial fold (NLF) after maximum retraction in adults and to determine its contributing factors.

MATERIALS AND METHODS

A total of 39 adult women's cone-beam computed tomography images were collected retrospectively and divided into the retraction group (age 26.9 ± 8.80) that underwent maximum retraction following 4 premolar extraction and the control group (age 24.6 ± 5.36) with minor changes of the incisors. Three-dimensional morphologic changes of hard and soft tissue including NLF were measured by pre- and posttreatment cone-beam computed tomography. In addition, perceived visual change of the NLF was monitored using the modified Global Aesthetic Improvement Scale. The influence of age, initial severity of NLF, and initial soft tissue thickness was evaluated.

RESULTS

Anterior retraction induced significant changes of the facial soft tissue including the lips, perioral, and the NLF when compared with the controls ( P < .01). Perceived visual changes of the NLF was noted only in women younger than age 30 ( P < .05), with the odds ratio (95% confidence interval) of 2.44 (1.3461-4.4226), indicating greater possibility for improvement of NLF esthetics in young women of the retraction group when compared with the controls.

CONCLUSIONS

Orthodontic retraction induced quantitative and perceived visual changes of the NLF. For adult women younger than age 30, the appearance of the NLF improved after maximum retraction despite the greater posterior change of the NLF.

Comparison of volume and position of the temporomandibular joint structures in patients with mandibular asymmetry

OBJECTIVE

To evaluate the volume and position of the temporomandibular joint structures, specifically the glenoid fossa and the condylar head, in patients with facial asymmetry.

STUDY DESIGN

Fifty-six adult patients were divided into two groups-asymmetry group and control group-based on the severity of the mandibular asymmetry, as seen on their orthopantomograms. The volumes and positions of the bilateral temporomandibular joint components were measured by using computed tomography images and a three-dimensional analysis program. Each of the variables was compared between and within the groups.

RESULTS

The volumes of the condyle and the glenoid fossa on the side of the smaller condyle were significantly smaller in the asymmetry group (P < .05) than in the control group. The volumetric ratios of the glenoid fossa and the joint space to the condyle were also significantly higher on that side (P < .001). The distance of the uppermost point of the glenoid fossa from the midaxial plane in the smaller condyle was significantly shorter (P < .05) only in the asymmetry group.

CONCLUSIONS

When evaluating mandibular asymmetry, the volume of the glenoid fossa and the volume and vertical position of the condylar head need to be considered in addition to length or width of the condylar head.

The evaluation of the nasal morphologic changes after bimaxillary surgery in skeletal class III maloccusion by using the superimposition of cone-beam computed tomography (CBCT) volumes

BACKGROUND

The purpose of this study was to evaluate nasal morphologic and maxillary skeletal changes occurring after bimaxillary surgery in skeletal class III patients, using a new method entailing superimposition of cone-beam computed tomography (CBCT) volumes.

MATERIALS & METHODS

The subjects consisted of 30 adults (15 males and 15 females) who had presented with skeletal class III deformities. The subjects underwent Le Fort I advancement and impaction osteotomy and mandibular setback surgery. For closure of the maxillary vestibular incision, alar cinch suture and V-Y closure were performed. The pre- and post-operative CBCT data were superimposed and evaluated by voxel-by-voxel registration.

RESULTS

After surgery, the nasolabial angle, nasal tip angle, nasal tip inclination and columellar angle showed significant increases (P < 0.01). The nasal tip protrusion and nasal height, meanwhile, had significantly decreased (P < 0.01), and the alar base width had increased (P < 0.01). The columellar length and nostril axis angle also had decreased, but the nostril area did not show any significant change.

CONCLUSIONS

After surgery, as the maxilla had been moved upward and forward, the nasal tip was shifted antero-superiorly and the alar base width and nostrils were widened. CBCT superimposition, enabling 3D assessment of nasal morphologic changes, can be an effective tool for simultaneous measurement of skeletal and soft-tissue changes.