A new three-dimensional analysis of asymmetry for patients with craniofacial syndromes

Assessment and Identification of Improvement Areas for Facial Symmetry in Hemifacial Microsomia (Type IIB) Using Three-dimensional Measurements

Background

Surgical planning for hemifacial microsomia (HFM) patients often involves planning the amount of maxillary movement and mandibular bone distraction from three-dimensional (3D) volumetric images constructed from computed tomography scans. By representing anatomical indicators for facial symmetry in X, Y, and Z coordinates, we identified the more challenging areas in correcting facial asymmetry.

Methods

The study included five HFM patients with a mean age of 22.2 years, all diagnosed with HFM (type IIB). We established measurement points with high reproducible 3D coordinates on the 3D volumetric images obtained from computed tomography scans for before surgery, treatment objectives, and after surgery. We assessed the symmetry of measurement points between the affected side and nonaffected side at each time point.

Results

In the before-surgery group, significant differences were observed between the affected side and nonaffected side in X,Y (excluding Palatine foramen, upper molar, canine) and Z coordinates for measurement items. In the treatment objectives group, no differences were observed between the affected side and nonaffected side in X, Y, and Z coordinates, resulting in facial symmetry. In the after-surgery group, significant differences were observed in Y coordinates in the mental foramen area, and significant differences were observed in z axis measurement items in the canine and mental foramen areas.

Conclusions

It is evident that relying solely on a front view assessment is insufficient to achieve facial symmetry. Particularly, both anterior-posterior and vertical improvements in the area near the mental foramen on the affected side are necessary.

Facial Asymmetry Detected with 3D Methods in Orthodontics: A Systematic Review

Background:

Historically, the development of two-dimensional (2D) imaging techniquesforerun that of three-dimensional (3D) ones. Some 2D methods are still considered valid and effective to diagnose facial asymmetry but 3D techniques may provide more precise and accurate measurements.

Objective:

The aim of this work is to analyze the accuracy and reliability of the imaging techniques available for the diagnosis of facial asymmetry in orthodontics and find the most reliable.

Methods:

A search strategy was implemented using PubMed (National Library of Medicine, NCBI).

Results:

A total of 3201 papers were identified in electronic searches. 90 articles, available in full text, were included in the qualitative synthesis consisting of 8 reviews on the diagnosis of facial asymmetry, 22 in vivo and in vitro studies on 2D methods and 60 in vivo and in vitro studies on 3D methods to quantify the asymmetry.

Conclusion:

2D techniques include X-ray techniques such as posterior-anterior cephalogram, which still represents the first level exam in the diagnosis of facial asymmetry. 3D techniques represent the second level exam in the diagnosis of facial asymmetry. The most current used techniques are CBCT, stereophotogrammetry, laser scanning, 3D optical sensors and contact digitization. The comparison between bilateral parameters (linear distances, angles, areas, volumes and contours) and the calculation of an asymmetry index represent the best choices for clinicians who use CBCT. The creation of a color-coded distance map seems to represent the most accurate, reliable and validated methods for clinicians who use stereophotogrammetry, laser scanning and 3D optical sensors.

Smartphone-assisted Augmented Reality in Craniofacial Surgery

Augmented reality (AR), a blending of both the physical and digital worlds, can be a valid tool for surgeons wishing to plan interventions and attain symmetry. The use of technology has enabled physicians to achieve desirable results. In this article, we describe a method that uses smartphone's simple AR utilities for convenient, cost effective, and time saving perioperative planning.

Methods

Images of preoperative computed tomography, along with 3D reconstructed scans were uploaded to a smartphone and used in an affordable application (Camera Lucida) to superimpose the loaded pictures over the smartphone camera. In one case, a 3D computed tomography scan of the skull was mirrored to help guide fronto-orbital advancement, and in another case the loaded 3D reconstructed computed tomography scan was used to prioritize areas of scalp coverage in a complicated case of craniosynostosis with major scalp wound dehiscence.

Discussion

Adaptation of AR to assist in the field of craniofacial surgery has been introduced before in several studies that reported the use of computer-based guidance for cranial reshaping. The majority of these reports used sophisticated modalities, combining advanced image registration and tracking with specialized equipment. The utility of smartphone AR for cranial vault reconstruction provided good accuracy when visualizing fronto-orbital advancement and remodeling, together with in depth prioritization of areas in need of soft tissue reconstruction.

Conclusion

Smartphone AR adaptation proved to be a very convenient tool assisting in the planning of different craniofacial conditions that are time saving and do not incur any additional fees beyond those of the surgery.

Accuracy of virtually planned mandibular distraction in a pediatric case series

The aim of this study was to describe the utility of 3D technology in mandibular distraction (MD) for patients with mandibular hypoplasia (MH), using 3D-printed cutting guides (CGs), and to assess the differences between virtual surgical planning (VSP) and the final result. A descriptive retrospective study of five patients diagnosed with MH, who required unilateral or bilateral MD, was carried out between January 2018 and January 2020. All patients underwent preoperative craniofacial CT scan and a 3D VSP was executed. MD was performed with the help of the 3D-printed CG. Before removal of the distractor, another CT scan was performed to compare the actual final result with the VSP. A mean difference of <4° was found for the osteotomy direction, < 7° for distractor position, and <2 mm for posterior screw placement. VSP and 3D-printed CGs have revolutionized surgical planning, facilitating surgical treatment and improving the final result. In our sample, the variations in osteotomy line, distractor position, and posterior screw placement have been minor, making the outcome more predictable.

Virtual modeling, stereolithography, and intraoperative CT guidance for the optimization of sagittal synostosis reconstruction: a technical note

INTRODUCTION

Sagittal synostosis affects 1 in 1000 live births and may result in increased intracranial pressure, hindrance of normal neural development, and cosmetic deformity due to scaphocephaly. Historically, several approaches have been utilized for surgical correction and recently, computed tomography (CT)-guided reconstruction procedures are increasingly used. In this report, the authors describe the use of a CT-derived virtual and stereolithographic (3D printed) craniofacial models, which are used to guide intraoperative bone placement, and intraoperative CT guidance for confirmation of bone placement, to ensure the accuracy of surgical correction of scaphocephaly, as demonstrated to parents.

METHODS

Preoperative high-resolution CT imaging was used to construct 3D image sets of the skulls of two infants (a 14-month-old female and a 6-month-old male) with scaphocephaly. These 3D image sets were then used to create a virtual model of the proposed surgical correction for each of the infants' deformities, which was then printed and made available for use intraoperatively to plan the bone flap, fashion the bone cuts, and optimize graft placement. After the remodeling, adherence to the preoperative plan was assessed by overlaying a CT scan of the remodeled skull with the virtual model. Deviations from the preoperative model were noted.

RESULTS

Both patients had excellent postoperative cosmetic correction of head shape and contouring. The mean operative time was 5 h, blood loss was 100 ml, and one child required modification of the subocciput after intraoperative imaging showed a deviation of the reconstruction from the surgical goal as depicted by the preoperative model.

CONCLUSION

The addition of neuro-navigation to stereolithographic modeling ensured the accuracy of the reconstruction for our patients and provided greater confidence to both surgeons and parents. While unisutural cases are presented for clarity, correction was still required for one patient. The cost of the models and the additional CT required must be weighed against the complexity of the procedure and possibly reserved for patients with potentially complicated corrections.

Assessment of dentofacial growth deviation in juvenile idiopathic arthritis: Reliability and validity of three-dimensional morphometric measures

Introduction

Patients with juvenile idiopathic arthritis (JIA) and involvement of the temporomandibular joint (TMJ) often experience abnormal facial growth. Three-dimensional (3D) assessment of dentofacial growth deviation has become more common with advancement and commercialization of imaging technologies. However, no standardized guidelines exist for interpretation of 3D imaging in patients with JIA. The aim of this study was to propose and validate morphometric measures for the 3D radiographic assessment of dentofacial growth deviation in patients with JIA to enhance: 1) Description of dentofacial growth deviation; 2) Treatment planning; 3) Longitudinal follow-up.

Methods

The study was conducted in a standardized sequential-phased approach involving: 1) Preliminary decision-making; 2) Item generation; 3) Test of content-validity; 4) Test of reliability; 5) Test of construct validity; 6) Establishment of final recommendations.

Results

Twenty-one morphometric measures were evaluated. Based on results of reliability and validity-testing including subjects with JIA (n = 70) and non-JIA controls (n = 19), seven measures received a “high recommendation” score. Those measures were associated with posterior mandibular height, occlusal cant, mandibular asymmetry, mandibular inclination, and anterior/posterior lower face height. Nine other measures were “moderately recommended” and five received a “somewhat recommendation” score.

Conclusion

Seven morphometric measures were considered very useful in the 3D assessment of growth deviation in patients with TMJ disease associated with JIA. These variables can be used to standardize the description of dentofacial deformities and to plan corrective interventions.

External apical root resorption concurrent with orthodontic forces: the genetic influence

Root resorption is a pathological process of multifactorial origin related to the permanent loss of dental root structure in response to a mechanical, inflammatory, autoimmune or infectious stimulus. External apical root resorption (EARR) is a frequent clinical complication secondary to orthodontic tooth movement; apart from variables related to treatment, environmental factors and/or interindividual genetic variations can confer susceptibility or resistance to its occurrence. In this context, genetic predisposition has been described as an etiological factor, together with mechanical factors derived from orthodontic treatment. In recent years, international research groups have determined the degree of influence of some genetic biomarkers in defining increased/reduced susceptibility to postorthodontic EARR. The influences of the IL1 gene cluster (IL1B, IL1A, IL1RN, IL6), P2RX7, CASP1, OPG (TNFRSF11B), RANK (TNFRSF11A), Osteopontin (OPN), TNFα, the vitamin D receptor (TaqI), TNSALP and IRAK1 have been analyzed. The objective of the present review study was to compile and analyze the latest information about the genetic background predisposing to EARR during orthodontic treatment. Genetics-based studies along with other basic science research in the field might help to clarify the exact nature of EARR, the influence of genetic inheritance and possibly lead to the prevention or even eradication of this phenomenon during orthodontic treatment.

Relationship between Mandibular Ramus Height and Masticatory Muscle Function in Patients with Unilateral Hemifacial Microsomia

Objective

To clarify the relationship between mandibular ramus height and function of masticatory muscles in patients with hemifacial microsomia.

Design

Retrospective study of imaging and physiological data.

Setting

Images and physiological data were obtained from the records of Sapporo Medical University Hospital.

Patients

A total of 29 patients with hemifacial microsomia who showed Pruzansky grades I, II deformity.

Main Outcome Measures

Mandibular ramus height and masticatory muscle volume were evaluated with multi-detector row computed tomography. The electromyographic value was measured by the K7 Evaluation System. The hemifacial microsomia patients were classified into three groups based on the mandibular ramus height ratio of the affected and unaffected sides: group 0, > 1.00; group 1, 1.00 to 0.85; group 2, < 0.85. The Tukey-Kramer method and Games-Howell method were used to determine correlations between parameters.

Results

Decreased mandibular ramus height was significantly correlated with both reduced electromyographic values of the masseter muscle (P < .05) and the amount of mandibular lateral deviation at the time of maximum opening (P < .05) on the affected side. These differences were prominent in unilateral hemifacial microsomia patients classified as group 2.

Conclusions

Decreased mandibular ramus height may cause dysfunction of the masseter muscles but not the temporal muscle on the affected side in patients with hemifacial microsomia.

Comparison between full face and hemifacial CBCT cephalograms in clinically symmetrical patients: a pilot study

INTRODUCTION:

One of the advantages of cone-beam computed tomography (CBCT) is the possibility of obtaining images of conventional lateral cephalograms derived from partial or complete reconstruction of facial images.

OBJECTIVE:

This study aimed at comparing full face, right and left hemifacial CBCT cephalograms of orthodontic patients without clinical facial asymmetry.

METHODS:

The sample comprised nine clinically symmetrical patients who had pretreament full face CBCT. The CBCTs were reconstructed so as to obtain full face, right and left hemifacial cephalograms. Two observers, at two different times, obtained linear and angular measurements for the images using Dolphin 3D software. Dependent and independent t-tests were used to assess the reproducibility of measurements. Analysis of Variance and Kruskal-Wallis tests were used to compare the variables obtained in the CBCT derived cephalometric views.

RESULTS:

There was good reproducibility for CBCT scans and no statistically significant differences between measurements of full face, right and left hemifacial CBCT scans.

CONCLUSIONS:

Cephalometric measurements in full face, right and left hemifacial CBCT scans in clinically symmetrical patients are similar.

Nodal pathway genes are down-regulated in facial asymmetry

PURPOSE

Facial asymmetry is a common comorbid condition in patients with jaw deformation malocclusion. Heritability of malocclusion is advancing rapidly, but very little is known regarding genetic contributions to asymmetry. This study identifies differences in expression of key asymmetry-producing genes that are down-regulated in patients with facial asymmetry.

METHODS

Masseter muscle samples were collected during bilateral sagittal split osteotomy orthognathic surgery to correct skeletal-based malocclusion. Patients were classified as class II or III and open or deep bite malocclusion with or without facial asymmetry. Muscle samples were analyzed for gene expression differences on Affymetrix HT2.0 microarray global expression chips.

RESULTS

Overall gene expression was different for asymmetric patients compared with other malocclusion classifications by principal component analysis (P < 0.05). We identified differences in the nodal signaling pathway, which promotes development of mesoderm and endoderm and left-right patterning during embryogenesis. Nodal and Lefty expression was 1.39- to 1.84-fold greater (P < 3.41 × 10), whereas integral membrane Nodal modulators Nomo1,2,3 were -5.63 to -5.81 (P < 3.05 × 10) less in asymmetry subjects. Fold differences among intracellular pathway members were negative in the range of -7.02 to -2.47 (P < 0.003). Finally Pitx2, an upstream effector of Nodal known to influence the size of type II skeletal muscle fibers was also significantly decreased in facial asymmetry (P < 0.05).

CONCLUSIONS

When facial asymmetry is part of skeletal malocclusion, there are decreases in nodal signaling pathway genes in masseter muscle. This data suggest that the nodal signaling pathway is down-regulated to help promote development of asymmetry. Pitx2 expression differences also contributed to both skeletal and muscle development in this condition.