Clinical and computerized assessment of mandibular asymmetry

Non-surgical occlusal plane cant resolution with lingual straight-wire appliance and miniscrews in a class II asymmetric adult patient

This case report describes a complex class II case with important maxillo-mandibular asymmetry in an adult patient treated with lingual straight-wire appliance. With the twofold aim of obtaining dramatic aesthetic improvement, since the patient refused surgical option, and ideal occlusal relationship, accurate set-up planification and biomechanical strategies with TADS for occlusal plane cant correction are needed to achieve the planned results. This case report demonstrates the possibility of solving successfully class II malocclusion with significant asymmetry in adult patient without surgery by means of an aesthetic appliance; on the other hand, it underlines the necessity of miniscrews and auxiliaries in order to obtain the best results.

Quantitative analysis of facial symmetry by using three-dimensional technology

Background

Facial symmetry is becoming increasingly important in today's orthodontic treatment. But the asymmetrical boundary is not clearly demarcated. Stereophotogrammetry has a clear advantage in measuring facial asymmetry. The aim of this study was to quantify the facial asymmetry by three-dimensional (3D) technology as well as to study whether the evaluation by non-experts about facial asymmetry was consistent with the analysis by 3D technology.

Methods

The facial symmetry of 330 patients was evaluated by 10 non-experts. 3D facial images were taken using 3dMD stereophotogrammetry equipment. The original face and its mirror shell were divided into 7 regions and the surface matching was measured in the whole face and all regional areas. The degree of symmetry was calculated by the software 3-matic STL 9.0. The difference between the two groups was analyzed by Independent-Samples T Test and the diagnostic efficiency of symmetry degree was analyzed by ROC curve analysis. The consistency between the symmetric degree and the result of evaluation was analyzed by Pearson correlation analysis.

Results

The ROC analysis revealed significant diagnostic values in the determination of the facial asymmetry of lip, chin, cheek and lateral mandible areas. The cut-off values of symmetry degree were between 60 and 80%. The evaluation was middle correlation with the symmetric degree of the whole face.

Conclusions

The chin and lateral mandible contribute most significantly to the facial symmetry. The objective measurement of facial symmetry, 3D technology, is reliable.

Perception and analysis of lip-line canting by different populations

INTRODUCTION

This study aimed to provide a valuable reference for the precise diagnosis and treatment of lip-line canting (LLC) in an orthodontic clinic, determine the average observed LLC that would need treatment, and compare the differences in different populations.

METHODS

We took frontal photographs of an adult female with rough facial symmetry and processed them into fully symmetrical frontal images using Photoshop (Adobe Systems, San Jose, Calif). After that, the lip line was rotated clockwise with a gradient of 1° to obtain 8 different pictures. Next, without informing the observers of the aim of the study, we randomly selected 60 dentists, 60 orthodontic patients, and 60 non-oral-related practitioners to observe the LLC in the photographs. We numbered all the images randomly, and the evaluators categorized them as a little LLC not requiring treatment and marked LLC requiring treatment. We then analyzed the results statistically.

RESULTS

Among the 240 observers, the average perception of LLC was 2.65°, and it was 4.1° for those requiring treatment. Orthodontists were more sensitive to the LLC than dentists and non-oral-related practitioners, and orthodontic patients were more sensitive than non-oral related practitioners (P <0.05). Overall, the tolerance value of the orthodontic patients was the least (P <0.05).

CONCLUSIONS

Among all the observers, orthodontic patients had the highest requirement for LLC. This finding could help therapists consider patient expectations when determining treatment plans.

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.

Evaluation of an automated approach for facial midline detection and asymmetry assessment: A preliminary study

OBJECTIVE

To examine the level of agreement between the conventional method and a machine-learning approach to facial midline determination and asymmetry assessment.

SETTINGS AND SAMPLE POPULATION

The study included a total of 90 samples (53 females; 37 males) with different levels of mandibular asymmetry.

MATERIALS AND METHODS

Two researchers placed predefined soft tissue landmarks individually on selected facial frontal photographs and created 10 reference lines. The midsagittal line was determined as perpendicular to the midpoint of the bipupillary line, and the same two reference lines and facial landmarks were automatically determined by the software using machine-learning algorithms, and researchers created the other 8 reference lines using the facial landmarks that were determined automatically by the software. In the following stage, 2 linear and 10 angular measurements were made by a single researcher on 270 photographs, and the consistency and differences between the measurements were evaluated with a one-sample t test, an intraclass correlation coefficient (ICC) and Bland-Altman Plots.

RESULTS

The level of agreement of measurements between the researchers and the software was low for eight parameters (ICC˂0.70). The one-sample t test revealed that differences between the software and researcher measurements of lip canting and pronasale deviation were not statistically significantly different (P > .05). Aside from the body inclination difference in Group 3 (samples with a mandibular body inclination difference >6°), there was no clinically significant difference (˂3°) between the measurements of the two methods.

CONCLUSIONS

Machine-learning algorithms have the potential for clinical use in asymmetry assessment and midline determination and can help clinicians in a manual approach.

Isolated Fat Grafting for Reconstruction of Lower Face Volumetric Asymmetry in Skeletally Immature Patients: A Clinical Outcome Study

BACKGROUND

The purpose of this study was to assess the objective and subjective outcomes of lower face volumetric (contour) asymmetry correction with isolated fat grafting in skeletally immature patients.

METHODS

A prospective analysis was conducted of skeletally immature patients (n = 73) with craniofacial microsomia and Parry-Romberg syndrome who underwent isolated fat grafting (with no previous or concomitant bone surgery) using anatomical surgical principles (facial subunits and fat compartments) for the reconstruction of lower face volumetric asymmetry. Objective ultrasound and photogrammetric lower face symmetry analyses were blindly performed preoperatively and at 3 and 12 months postoperatively. A panel assessment of blinded surgical professionals and laypersons was also obtained to grade the subjective lower face symmetry.

RESULTS

There were significant (all P < 0.05) postoperative objective and subjective lower face symmetry enhancements (preoperative < postoperative) after isolated fat grafting, with no differences (all P > 0.05) between 3 versus 12 months' postoperative comparisons.

CONCLUSIONS

Growing patients with unilateral lower face volumetric asymmetries presented with improvement of objective and subjective symmetry after a single isolated fat grafting procedure.

Occlusal plane canting: a treatment alternative using skeletal anchorage

A canted occlusal plane is the cause of unaesthetic smile, and also represents a challenge, due to the complex orthodontic procedures involved in its treatment. The skeletal anchorage allows successful treatment of this asymmetry in the majority of cases, with less dependency on the patient cooperation and reducing the necessity of orthognatic surgery. Given this condition, this article aims at discussing the main aspects related to the diagnosis of occlusal plane canting, treatment plan, and orthodontic mechanics using skeletal anchorage either by mini-implants or miniplates. In this context, five cases will be reported, showing the main details related to the orthodontic mechanics used to correct the occlusal plane, avoiding side effects and successfully reaching treatment objectives and long-term stability.

Linear and Volumetric Mandibular Asymmetries in Adult Patients With Different Skeletal Classes and Vertical Patterns: A Cone-Beam Computed Tomography Study

This study aimed to quantify the height of the mandibular condyle and ramus, condylar volume, and the asymmetry index in adult patients of different sex, skeletal class and vertical pattern using Cone-Beam Computed Tomography (CBCT), and to determine whether there were differences between these groups. The study used CBCT scans of 159 patients with a mean age of 32.32 ± 8.31 years. InVivoDental® software was used to perform both linear (condylar, ramal, and total height) and condylar volume measurements. Linear and volumetric asymmetries were calculated. There were not significant differences between right and left sides. The mean value obtained for condyle height was 7.27 mm, ramus height 42.3 mm, total height 49.6 mm and condyle volume 1907.1 mm3, with significant differences between men and women. Significantly higher values were found for condylar volume in hypodivergent patterns (p = 0.001) and for the asymmetry index of the condylar volume in Class II patients (p < 0.05). The prevalence of relevant asymmetry was high for condyle height and volume (73.1% y 75.6% respectively). Higher height and volume values were found among men, Class III, and hypodivergent patients. Linear and volumetric asymmetries were more prevalent among men, Class III and hyperdivergent patterns.

Cone Beam Computed Tomographic Evaluation of Mandibular Asymmetry in Patients with Cleft Lip and Palate

Objective:

The purpose of the present study was to compare mandibular vertical asymmetry in patients with unilateral and bilateral cleft lip and palate and subjects with normal occlusion.

Materials and Methods:

Cone beam computed tomography scans of three groups consisting of 20 patients with unilateral cleft lip and palate, 20 patients affected by bilateral cleft lip and palate, and a control group of 20 subjects with normal occlusion were analyzed for this study. Condylar, ramal, and condylar plus ramal asymmetry indices were measured for all subjects using the method of Habets et al. Kruskal-Wallis and Mann-Whitney tests were used to determine any significant differences between the groups for all indices at the 95% level of confidence.

Results:

There were no significant differences regarding sex for all mandibular asymmetry indices in all three groups. All Asymmetry indices (condylar, ramal, and condylar plus ramal asymmetry) were significantly higher in the unilateral cleft group compared with the other two groups.

Conclusion:

Cone beam computed tomography images showed that patients with cleft lip and palate suffered from mandibular asymmetry. Subjects with unilateral cleft lip and palate had a more asymmetric mandible compared with the bilateral cleft lip and palate and control groups. Therefore, the mandible appears to be the leading factor in facial asymmetry in subjects with unilateral cleft lip and palate.

Influence of occlusal plane inclination and mandibular deviation on esthetics

OBJECTIVE

The aim of this study was to assess the degree of perception of occlusal plane inclination and mandibular deviation in facial esthetics, assessed by laypeople, dentists and orthodontists.

METHODS

A woman with 5.88° of inclination and 5.54 mm of mandibular deviation was selected and, based on her original photograph, four new images were created correcting the deviations and creating more symmetric faces and smiles. Examiners assessed the images by means of a questionnaire. Their opinions were compared by qualitative and quantitative analyses.

RESULTS

A total of 45 laypeople, 27 dentists and 31 orthodontists filled out the questionnaires. All groups were able to perceive the asymmetry; however, orthodontists were more sensitive, identifying asymmetries as from 4.32° of occlusal plane inclination and 4.155 mm of mandibular deviation (p< 0.05). The other categories of evaluators identified asymmetries and assigned significantly lower grades, starting from 5.88° of occlusal plane inclination and 5.54 mm of mandibular deviation (p< 0.05).

CONCLUSION

Occlusal plane inclination and mandibular deviation were perceived by all groups, but orthodontists presented higher perception of deviations.

Asymmetry of the lips of orthognathic surgery patients

INTRODUCTION

The purpose of this study was to examine asymmetry of the lips in patients with jaw deformity and facial asymmetry.

METHODS

Pretreatment and posttreatment frontal facial photographs of 17 patients who had mandibular prognathism with facial asymmetry were analyzed. Linear and angular measurements were made on the photographs to assess the asymmetry of the lips. The upper and lower vermilion borders of the lips were divided into quadrants according to the y-axis, and each was measured. In addition, skeletal deviation (position of menton) was determined from the frontal cephalograms.

RESULTS

The pretreatment linear and angular measurements showed asymmetry of the lips, but this significantly improved after treatment, and the lip form was almost symmetrical. The areas of vermilion border in the upper and lower lips became almost even during treatment. The ratio of the areas on the 2 sides was nearly 1.00. There was little correlation between the horizontal skeletal changes of menton and lip form.

CONCLUSIONS

Asymmetry of the lips caused by deviation of the mandible can be almost completely corrected by orthognathic treatment.

Discriminative thresholds of cephalometric indexes in the subjective evaluation of facial asymmetry

INTRODUCTION

The purpose of this study was to determine the means and the ranges of the thresholds of cephalometric indexes by which orthodontists subjectively differentiate patients needing treatment for facial asymmetry from those who do not. The study was performed at the Departments of Orthodontics and Oral and Maxillofacial Radiology, Aichi-Gakuin University School of Dentistry in Nagoya, Japan, in 2004.

METHODS

Ten orthodontists subjectively evaluated the frontal photographs of 100 subjects and classified them into 2 groups. The subjects in group A showed good or clinically acceptable levels of asymmetry and did not require treatment. Those in group B showed marked asymmetry, and treatment was recommended. The frontal cephalographs were also analyzed with 5 indexes related to the mandible. For each orthodontist, the threshold was determined by means of the discriminant analysis.

RESULTS

As the number of subjects who were judged to require treatment increased, the threshold of cephalometric indexes became smaller, and the discriminant accuracy was reduced. Among the 5 indexes evaluated, the distance of menton (mean, 4.28 mm), maxillomandibular midline angle (mean, 4.31 degrees ), and the distance of L1 (mean, 2.78 mm) showed relatively high accuracy in all observers.

CONCLUSIONS

The distance of menton, the maxillomandibular midline angle, and the distance of L1 appeared to be relevant indexes for the subjective evaluation of facial asymmetry. The thresholds determined in this study could contribute to the planning and evaluation of orthodontic treatments.

A computerized photographic assessment of the relationship between skeletal discrepancy and mandibular outline asymmetry

The aim of this study was to investigate the relationship between mandibular outline asymmetry and skeletal discrepancy in a sample of orthodontic patients (33 females, 33 males) aged from 8 to 19 years. Skeletal discrepancy was assessed in both the anteroposterior and vertical planes, using standard cephalometric analyses. All were photographed under standardized conditions and the photographs were then digitized for analysis using a computerized system to assess differences in four variables (area, perimeter, compactness and moment-ratio) between the right and left sides of the mandibular outline. The results showed good repeatability of the photographic, cephalometric and digitization methods. A statistically significant relationship was found between mandibular outline asymmetry and both anteroposterior and vertical skeletal discrepancy in this sample, when compared with patients with an average skeletal pattern. There appeared to be a statistically significant relationship between a reduced ANB angle (< 3 degrees) and mandibular outline asymmetry (P = 0.051), as well as between an increase in lower face height and mandibular asymmetry (P = 0.023).

Facial scoliosis from sternocleidomastoid torticollis: Long-term postoperative evaluation

A 10-year-old girl with congenital torticollis was treated by biterminal tenotomy of the sternocleidomastoid muscle and division of cervical fascia. She was followed up regularly for 14 years and her facial asymmetry resolved almost completely.

Outcome measurement in the correction of mandibular asymmetry

This study related clinical assessments of the severity of mandibular asymmetry with computerized measurements, obtained by digitizing mandibular outlines from standardized facial photographs. Four ratios were calculated: area (size), compactness (shape), perimeter (length of outline), and moment (center of area). When comparing clinical severity with computer assessment, significant correlations were observed; those for area and compactness were the highest. Sixteen patients subsequently underwent corrective surgery, and their ratios were used to relate the degree of improvement to the original severity of the asymmetry. The posttreatment ratios were also used to audit the outcome, comparing the patients' scores as a group with results previously obtained from patients with normal symmetry and mild asymmetry. Posttreatment outcomes were significantly different from the normal outline group but were comparable with outcomes of patients with mild mandibular asymmetry. The system provided a sensitive, noninvasive method of assessing treatment change and could be useful in providing an objective means of quantifying treatment outcomes.

Comparison of radiographic and photographic measurement of mandibular asymmetry

This study compared measurement of mandibular asymmetry by digitization of mandibular outlines from standardized facial photographs and posteroanterior cephalometric radiographs. Four ratios were used in calculating asymmetry: area (relative size of right and left mandibular segments), perimeter or length of outlines, compactness (shape), and moment. The records of 28 patients with varying degrees of asymmetry were used. A significant relationship was found for 3 of the ratios (area, compactness, and moment) between measurements from photographs and radiographs. A further comparison showed that measurements from the radiographs correlated more closely with those from photographs when the mastoid processes were used as a baseline, rather than latero-orbitale. Repeatability of mandibular outline digitization proved satisfactory. Although digitization from standardized photographs is the preferred approach, the results indicated that posteroanterior cephalometric radiographs can be used similarly. Unlike other cephalometric analyses for mandibular asymmetry, this method avoids problems of landmark identification, thus presenting a clinically useful method of quantifying asymmetry, eg, in auditing the surgical-orthodontic correction of asymmetry or monitoring change over time.