Facial morphology differences in monozygotic twins: a retrospective stereophotogrammetric study

OBJECTIVE

To assess soft tissue differences between monozygotic twins (MZ) for the total face and between facial regions using three-dimensional (3D) stereophotogrammetry and quantitative surface-based 3D deviation analyses.

MATERIALS AND METHODS

The study sample consisted of 14 untreated MZ twins (6 males, 8 females, mean age: 14.75 years) from the archive of Marmara University, Department of Orthodontics. The images were taken by the 3dMDface system, and 3dMDvultus software was used for removal of undesired areas and approximation of the images. Then, stereolithography (.stl) format images were superimposed using the best-fit algorithm using 3-matic software. The face was divided into facial thirds, and upper lip and lower lip + chin regions were created. For the comparison, 3D deviation analyses were performed, and a color map and histogram were created. The data were presented as mean deviation, root mean square (RMS), median, and interquartile range.

RESULTS

Between the facial thirds, there was no significant difference in soft tissue differences for mean deviation. A statistically significant difference was found between the upper and lower face for the RMS value. For the comparison of upper lip and lower lip + chin region, the only significant difference was for the RMS. When the data were presented as median and interquartile range, there were no statistically significant differences between any facial regions.

CONCLUSIONS

Lower facial third and lower lip + chin regions had the greatest differences within MZ twin pairs. The genetic and environmental influences might not be the same for different parts of the face.

Accuracy in predicting soft tissue changes of orthodontic class III cases using Dolphin® software

OBJECTIVES

The prediction of posttreatment outcomes is conducive to the final determination of ideal therapeutic options. However, the prediction accuracy in orthodontic class III cases is unclear. Therefore, this study conducted exploration on prediction accuracy in orthodontic class III patients using the Dolphin® software.

MATERIALS AND METHODS

In this retrospective study, lateral cephalometric radiographs of pre- and posttreatment were collected from 28 angle class III adults who received completed non-orthognathic orthodontic therapy (8 males, 20 females; mean age = 20.89 ± 4.26 years). The values of 7 posttreatment parameters were recorded and inserted into the Dolphin® Imaging software to generate a predicted outcome, and then the prediction radiograph and actual posttreatment radiograph were superimposed and compared in terms of soft tissue parameters and landmarks.

RESULTS

The prediction showed significant differences with the actual outcomes in nasal prominence (the difference between the prediction and the actual value was - 0.78 ± 1.82 mm), the distance from the lower lip to the H line (0.55 ± 1.11 mm), and the distance from the lower lip to the E line (0.77 ± 1.62 mm) (p < 0.05). Point subnasale (Sn) (an accuracy of 92.86% in the horizontal direction and 100% in the vertical direction in 2 mm) and point soft tissue A (ST A) (an accuracy of 92.86% in the horizontal direction and 85.71% in the vertical direction in 2 mm) were proven to be the most accurate landmarks, while the predictions in the chin region were relatively inaccurate. Furthermore, the predictions in the vertical direction were of higher accuracy compared to the horizontal direction except for the points around the chin.

CONCLUSIONS

The Dolphin® software demonstrated acceptable prediction accuracy in midfacial changes in class III patients. However, there were still limitations for changes in the chin and lower lip prominence.

CLINICAL RELEVANCE

Clarifying the accuracy of Dolphin® software in predicting soft tissue changes of orthodontic class III cases will facilitate physician-patient communication and clinical treatment.

[Assessment of soft-tissue vs hard-tissue changes after isolated functional genioplasty]

INTRODUCTION

This study aimed to determine the vertical and horizontal soft-tissue vs hard-tissue changes after isolated functional genioplasty and to revisit hard-tissue remodeling at the symphysis.

METHODS

Seventy-five patients who underwent genioplasty as an isolated procedure at the end of their orthodontic treatment were divided into three groups on the basis of their age at surgery: < 15 years (group 1), 15-18 years (group 2) and ≥ 19 years (group 3). Patients were evaluated at three time points: immediately before surgery (T1), immediately after surgery (T2) and two years after surgery (T3). In addition, 25 patients who did not accept genioplasty, were age-matched with group 1, and had a follow-up radiograph two years after the end of their orthodontic treatment were used as a control group.

RESULTS

From T2 to T3, group 1 showed less forward horizontal hard-tissue and soft-tissue changes at pogonion (Pg) than the control group; however, no difference was noted for vertical changes at Me & Me’. From T1 to T3, the horizontal hard-tissue and soft-tissue changes at Pg were 6.39 mm and 6.72 mm, respectively, for surgical groups. Vertical hard-tissue change at menton (Me) showed a reduction of 1.63 mm (95% confidence interval [CI], -3.37 to 0.11) and 3.89 mm (95% CI, -5.83 to -1.95) in nongrowing female and male patients, respectively. The vertical soft-tissue change reduction was similar for nongrowing male and female patients (1.7 mm [95% CI, -2.96 to -0.45]). Soft-tissue thickness change at Pg (0.33 mm) was not significant. In contrast, a small but significant increase in soft-tissue thickness was noted at Me (0.54 mm). Linear regressions were calculated for all groups and allowed for predicting long-term soft-tissue changes (T3-T1) using the amount of surgical displacement (T2-T1).

CONCLUSIONS

The horizontal hard-tissue change was stable for nongrowing patients, and the horizontal soft-tissue change was 92% of hard-tissue. Vertical soft-tissue change is less predictable. Variation of soft-tissue thickness after genioplasty can be explained by skeletal changes and the achievement of an unforced labial occlusion. These results support the functional and esthetic benefits of this surgery. Comparison with the control group showed that genioplasty does not change the growth pattern, and bone remodeling is likely to explain the difference noted at Pg.

Long-term hard and soft tissue response following isolated genioplasty: a systematic review

PURPOSE

Genioplasty facilitates alteration of the chin position and contour which contributes to aesthetics and function. The response of the hard and soft tissues following genioplasty has not been assessed after a year or more of the surgery being performed. Hence, the aim of this systematic review was to assess the response of the hard and soft tissues occurring at least 1 year after the procedure.

MATERIAL AND METHODS

A literature search was conducted in the following electronic databases: PubMed, Ovid, LILACS, and Cochrane Library. Potential articles were identified wherein only studies with genioplasty performed as an isolated procedure and with data at least 12 months after the procedure were included.

RESULTS

Five studies were included in this systematic review. Two of the articles included were considered to be of good quality while three were considered to be of moderate quality using a modified Downs and Black tool. The ROBINS-I tool showed a moderate risk of bias for most domains. The study characteristics revealed varying degrees of relapse for the hard and soft tissues.

CONCLUSIONS

In the anteroposterior plane, the soft tissue relapsed more than the hard tissues 3 years post genioplasty. However, relapse in the vertical plane showed a wide variation for both the hard and soft tissues. In the anteroposterior plane, the hard tissue to soft tissue response 2 years or more following genioplasty ranged from 1:0.77 to 1:0.91 while in the vertical plane the hard tissue to soft tissue response ranged from 1:0.67 to 1:1.16.

Three-dimensional virtual planning in mandibular advancement surgery: Soft tissue prediction based on deep learning

The study aimed at developing a deep-learning (DL)-based algorithm to predict the virtual soft tissue profile after mandibular advancement surgery, and to compare its accuracy with the mass tensor model (MTM). Subjects who underwent mandibular advancement surgery were enrolled and divided into a training group and a test group. The DL model was trained using 3D photographs and CBCT data based on surgically achieved mandibular displacements (training group). Soft tissue simulations generated by DL and MTM based on the actual surgical jaw movements (test group) were compared with soft-tissue profiles on postoperative 3D photographs using distance mapping in terms of mean absolute error in the lower face, lower lip, and chin regions. 133 subjects were included - 119 in the training group and 14 in the test group. The mean absolute error for DL-based simulations of the lower face region was 1.0 ± 0.6 mm and was significantly lower (p = 0.02) compared with MTM-based simulations (1.5 ± 0.5 mm). CONCLUSION: The DL-based algorithm can predict 3D soft tissue profiles following mandibular advancement surgery. With a clinically acceptable mean absolute error. Therefore, it seems to be a relevant option for soft tissue prediction in orthognathic surgery. Therefore, it seems to be a relevant options.

Cone beam computed tomography imaging of sagittal positions of the mandibular prominence and maxillary central incisors in adult Chinese Han men as an aesthetic profile determinant

BACKGROUND

To analyze the sagittal positions of the mandibular prominence and maxillary central incisors in adult Chinese Han men to establish their aesthetic profile characteristics.

METHODS

Seventy-four Chinese Han men aged 18 to 40 years underwent cone beam computed tomography for detecting the distances between Glabella and Subnasale, Subnasale and Menthon of soft tissue, Condyle and Gonion, Pogonion and Pogonion's Anterior Limit Line, Facial Axis point of maxillary central incisor and the Goal Anterior Limit Line as well as the angle of the Occlusal Plane. Dolphin Imaging and Photoshop software packages were used to generate silhouette profiles. Thirteen orthodontists assessed the silhouette profiles and assigned visual analog scale scores. Scores >70 were assigned to the aesthetic (group 1), scores of 60to 70 to the general (group 2), scores of 50 to 60 to the acceptable (group 3), and scores of <50 to the unaesthetic profile (group 4).

RESULTS

A total of 15 men were assigned to group 1, 35 to group 2, 14 to group 3, and 10 to group 4. There were no significant differences in the variables examined between groups 1, 2, and 3, but comparing group 1 with group 4, Pogonion and Pogonion's Anterior Limit Line (1.16 ± 2.61 mm vs -1.44 ± 2.92 mm, P = .046) and Facial Axis-Goal Anterior Limit Line (-0.61 ± 2.54 mm vs 1.70 ± 2.62 mm, P = .038) there were significant differences.

CONCLUSION

Compared with the unaesthetic profile group, the sagittal positions of the maxillary central incisors were slightly posterior, and the chin was slightly anterior in adult Chinese Han men with an aesthetic profile.

Assessment of mandibular characteristics in patients affected with β-thalassaemia major: A retrospective case-control study

OBJECTIVE

Thalassemia is the most common hereditary blood disorder across the world. This study aimed to identify some mandibular features of thalassaemic patients and compare them with unaffected counterparts.

MATERIAL AND METHODS

This retrospective case-control study was carried out on lateral cephalograms of 60 subjects (26 males, 34 females) with class II malocclusion and age range of 11 to 15 years. The control group consisted of 60 non-thalassaemic subjects with class II malocclusion and similar chronological age, gender and vertical facial dimension. Based on the Jarabak index, the case and control subjects were classified into hyperdivergent, normodivergent and hypodivergent growth patterns. Four linear (ramus height, ramus width, mandibular depth, and antegonial notch depth) and 3 angular (symphyseal angle, gonial angle, and mandibular arc angle) cephalometric parameters were measured to represent mandibular morphology. The data were analysed using Chi-square test and Student's t-test.

RESULTS

No significant difference was found in linear measurements between thalassaemic patients and controls. The symphysis angle was significantly greater and the mandibular arc angle was significantly smaller in the total thalassaemic sample than the control individuals (P<0.001 and P=0.004, respectively). The difference in symphysis angle was significant in both hyperdivergent and normodivergent subjects (P=0.004 and P=0.002, respectively), whereas the difference in mandibular arc angle was only significant in the normodivergent subgroup P=0.001).

CONCLUSIONS

The smaller mandibular arc angle in the thalassaemic sample suggests a more superior than posterior growth direction of condyles compared with healthy individuals. The difference in symphyseal angle represents inherent differences in chin morphology between thalassaemic subjects and controls.

The Use of Deoxycholic Acid for the Clinical Reduction of Excess Submental Fat in Indian Patients

Copy: The injectable adipocytolytic drug deoxycholic acid (DCA) is the first pharmacological intervention approved for the reduction of submental fat (SMF) and offers an alternative to invasive measures to improve the submental profile and the cervico-mental angle. DCA injection (ATX-101, Kybella [United States], Belkyra [Canada]; Kythera Biopharmaceuticals, Inc., Westlake Village, CA, acquired by Allergan, Inc.), are proprietary formulations of synthetically derived DCA that is FDA approved for improvement in the appearance of moderate to severe convexity or fullness associated with SMF. Aim: As none of the aforementioned are available in India, we undertook this study to study the efficacy of generic DCA for SMF reduction in Indian patients. Methods: 50 patients with confirmed Indian ethnicity and unwanted SMF were injected 3 mg/cm2 of generic DCA into their SMF, with a 12-week follow-up period. In each session, 5 ml of 30 mg /ml DCA was injected. The sessions were spaced approximately 2 months apart. All these patients with reductions in SMF were reported using Clinician Reported SMF Rating Scale (CR-SMFRS) and Patient Reported SMF Rating Scale (PR-SMFRS) using the Validated Rating Scale for improvement in the appearance of their chin, the neck, and the cervico-mental profile. Also, for objective assessment of improvement in SMF, caliper measurements were used. Results: One session was required in 2 patients, 12 patients needed 2 sessions, 32 patients needed 3 sessions, and 4 patients needed 4 sessions. Altogether, 90% patients showed at least a decrease of 1 point in (CR-SMFRS). Reduction in SMF as confirmed by caliper measurements was statistically significant. Conclusion: The findings show generic deoxycholic acid to be equally effective in the treatment for SMF in Indian patients. J Drugs Dermatol. 2019;18(3):266-272.

Three-dimensional region-based study on the relationship between soft and hard tissue changes after orthognathic surgery in patients with prognathism

Both deep understanding and reliable prediction of postoperative soft tissue changes are crucial for planning orthognathic surgery. Instead of estimating soft tissue responses by measuring individual landmark changes, this study aimed to investigate the relationship (ratio) between soft and hard tissue movements in different facial regions through three-dimensional cone-beam computed tomography (CBCT). Preoperative and postoperative CBCT images were superimposed using the surface registration method on the basis of the cranial base, and 10 facial regions of interest were defined. Region-based volumetric subtractions between the preoperative and postoperative segments were performed. The volumetric differences and surface of each region were used to estimate the average movement. Correlation and regression analyses were performed to examine the relationships between the corresponding soft and hard tissue movements. An overall pattern of facial soft tissue movement was observed in patients with prognathism who underwent orthognathic surgery. The experiment results have shown that mean ratios for the average soft-to-hard tissue movements in the facial regions varied, which may not exactly be similar to the published reports because of the population biocharacteristics and study methods, but the trend is in agreement with the previous studies. Additionally, the prediction capability of the regression model was significantly high, ranging from 0.786 to 0.857, in upper lip, upper vermilion, and chin regions, thus demonstrating that the skin outline changes in these critical regions could be reliably predicted from the underlying bone movements. These results could likely be applied in future soft tissue simulation in orthognathic surgery.

The effects of surgically assisted rapid maxillary expansion (SARME) on the dental show and chin projection

OBJECTIVE

To quantify the postoperative changes of the dental show and chin projection following SARME using 3D CBCT imaging.

MATERIAL AND METHODS

78 patients with transversal maxillary hypoplasia and mandibular hypoplasia who underwent SARME were enrolled into the study. A cone beam computed tomography (CBCT) scan was acquired preoperatively and at least 1 year postoperatively. 3D postoperative changes in the dental show and pogonion position were measured based on soft tissue and hard tissue landmarks.

RESULTS

68 patients (87%) exhibited a postoperative increase in the dental show. The dental show was increased by a mean of 2.2 ± 2.0 mm (p < 0.01). The mean horizontal and vertical displacement of the chin (pogonion) following SARME was 1.6 ± 2.5 mm posteriorly and 1.6 ± 2.0 mm inferiorly (p < 0.01). An inferior displacement of the maxilla and maxillary tooth as well as a consequent clockwise pitch of the mandible seemed to play a role in inducing these postoperative changes.

CONCLUSION

An increase in dental show and a posterior and inferior displacement of the chin should be considered prior to SARME to prevent undesirable postoperative changes of the facial esthetics.

Prediction of Difficult Airway Among Patients Requiring Endotracheal Intubation in a Tertiary Care Hospital in Eastern Nepal

INTRODUCTION

Various screening tests are done for predicting difficult laryngoscopy with variable diagnostic accuracy. Difficult laryngoscopy is being considered a surrogate indicator of difficult intubation, though it is not the exact measure of intubation difficulty. Our objectives were to find out the better predictor of difficult laryngoscopy amongst the routinely used tests and also to find the ability of difficult laryngoscopy to predict difficult intubation.

METHODS

This prospective, observational study involved 314, ASA I/II adult patients requiring endotracheal intubation. Measurement of sternomental, thyromental and inter-incisor distances and gradings of mandibular protrusion and modified Mallampati were done. Statistical values including sensitivity and specificity of these tests were calculated to find the better predictor of difficult laryngoscopy. Cormack and Lehane laryngoscopy grade III/IV was defined as difficult laryngoscopy. Requirement of >3 attempts for endotracheal intubation was defined as difficult intubation.

RESULTS

The sensitivity of the Modified Mallampatti Test for predicting difficult laryngoscopy was highest, 83% compared to other tests. Total 12 (3.8%) patients had difficult laryngoscopy. Intubation was difficult in 7 (2.2%) patients, of which four had difficult laryngoscopy (P<0.001).

CONCLUSIONS

Modified Mallampati test was better for predicting difficult laryngoscopy compared to other bedside screening tests. Difficult laryngoscop could significantly predict difficult intubation in our patients.

Chin-throat anatomy: Normal relations and changes following orthognathic surgery and growth modification

OBJECTIVES

To determine if a new facial line (T), tangent to the throat, intersects the mandibular border in anterior (ANT) and posterior (POST) parts in proportions varying with facial configuration, and to evaluate the association between chin projection and throat inclination and the potential for the T-line to reflect this association.

MATERIALS AND METHODS

Measurements on profile photographs and cephalograms of 135 adults (aged 18-50 years)-45 each of Class I, II, and III (CI, CII, CIII) malocclusions-included ANT and POST, chin-throat (CTA), and mento-cervical (MCA) angles. Pre- and posttreatment measurements were compared in two subgroups (n = 25 each) of CII and CIII orthognathic surgery patients and in CII, division 1 early-treatment patients (n = 63). Statistics included analysis of variance and t-test for group differences, and Pearson correlation for associations among variables.

RESULTS

ANT was nearly equal to POST in CI (50.99%) and CIII (51.86%) subjects and shorter in CII (36.01%) subjects. CTA and MCA were greater in CII profiles and smaller in CIII profiles. Significant differences (P < .0001) were observed for ANT, POST, CTA, and MCA between Classes I/II and II/III and for MCA between Classes II/III (P = .016). High correlations were noted between ANT and CTA in Classes I (r = -0.83), II (r = -0.73), and III (r = -0.68). In surgically treated patients, posttreatment measurements approached CI values. In the early-treatment group, ANT increased but remained smaller than POST; CTA decreased by nearly 13%.

CONCLUSIONS

Chin-throat relations and chin extension are associated and require routine assessment in terms of diagnosis and treatment outcome. A practical tool to assess chin-throat relationship, the T-line bisects the mandibular body nearly equally in Class I faces.

Dentofacial Considerations in Genioplasty

Chin augmentation, particularly with implants, has become popular in recent years. For the most part, the focus is on the position of the pogonion. The rest of the mid-face, including the maxilla and mandible, are usually ignored. In this article, different scenarios and deformities in the maxillofacial complex that can affect the chin position and shape of its overlying soft tissue are illustrated. It is the author’s view that a number of genioplasty augmentation procedures should be deferred. Discussion of alternative treatments should take place with patients regarding their underlying skeletal issues.

The Growth Hormone Receptor Gene is Associated with Mandibular Height in a Chinese Population

Genetic influences are important in the determination of mandibular morphology, and growth hormone receptor ( GHR) is believed to have an important influence on the growth of craniofacial bone. In this study, we used quantitative trait locus methods to evaluate the relationship between craniofacial morphology and single-nucleotide polymorphisms (SNPs) in GHR in an unselected healthy Chinese population. We systematically screened the 10 exons and nearby introns of GHR and identified 6 SNPs. Using 4 SNPs as markers, we studied the relationships between genotypes and craniofacial linear measurements. Individuals with the genotype CC of polymorphism I526L had a significantly greater mandibular ramus length (condylion-gonion/ articulare-gonion) than those with genotype AC or AA. Haplotype analysis showed that there were also significant differences between the long and short mandibular height groups in an extreme population. Our results indicate that the GHR gene polymorphism I526L is associated with mandibular height in the Chinese population.

The degree of intubation difficulties and the frequency of complications in obese patients at the Hospital Emergency Department and the Intensive Care Unit: Case-control study

The intubation difficulties in obese patients are not a new problem. They may result from an accumulation of fat in the oral cavity and cheeks. A thick tongue is also a significant factor. The literature reports that some tests to determine the intubation difficulties in obese people may be unreliable. The observed predictors of difficult intubation were the thyromental and sternomental distance and the intubation difficulty scale: FRONT score.The aim of this study was to assess the degree of difficult intubation in obese patients by the parameters such as the thyromental and sternomental distance. The authors also tried to evaluate the frequency of the guidewire usage and the number of intubation attempts in obese patients in the research sample.The study included the group of 153 patients intubated in prehospital conditions. The research was conducted in 3 clinical centers receiving patients from prehospital care. Among the members of the research sample, obese patients with body mass index >35 were selected and evaluated for various predictors of intubation difficulties. Quantitative analysis of differences in the incidence of the variables was assessed using the chi-squared test for P < 0.05. Analyses were performed in STATISTICA.Complications such as postintubation hematomas were more frequent in obese patients of the research sample. The frequency of the guidewire usage observed in that group was also higher. As anticipated by the adopted predictors, most of the obese patients were classified as difficult to intubate.There is a correlation between the occurrence of injuries and the prevalence of obesity in the research sample and the same dependency has been demonstrated in the issue concerning the use of the guidewire. Although the majority of predictors indicated patients with intubation difficulties, many predictors could show falsely positive results. The greater amount of intubation attempts was observed in obese patients. Further studies devoted to explain those correlations would be needed.

Ultrasonographically locating the mental foramen and its soft tissue relations

OBJECTIVES

This ultrasound-based cross-sectional study aimed to visualize, locate and compare the position of the mental foramen with regard to its relationship to various soft tissue landmarks.

METHODS

100 Black and Caucasian subjects were included. An ultrasound transducer was used to locate the mental foramina. Distances to various landmarks were measured and compared.

RESULTS

All mental foramina were visualized. The mean soft tissue distance of the entire group from the mental foramen on the right and left sides, respectively, were as follows: (a) 3.4 mm [standard deviation (SD) 1.7 mm] and 3.4 mm (SD 1.5 mm) lateral to a vertical line passing through the chelion; (b) 20.1 mm (SD 2.6 mm) and 20.1 mm (SD 2.6 mm) distal to a horizontal line bisecting the chelions; (c) 15.1 mm (SD 2.4 mm) and 15.0 mm (SD 2.4 mm) proximal to the inferior border of the mandible. We found no statistically significant differences between race groups, between gender group and between age categories with regard to the horizontal soft tissue distance from a vertical line passing through the chelion to the mental foramen on the right or left sides. There were statistically significant (but not clinically significant) differences between race groups and between gender groups but not between age groups with regard to the vertical soft tissue distance from a horizontal line bisecting the chelions to the mental foramen as well as from the inferior border of the mandible to the mental foramen on both the right and left sides.

CONCLUSIONS

This study suggests that ultrasound is a feasible imaging modality that can be utilized to locate the mental foramen. Differences in the position of the mental foramen with regard to various soft tissue landmarks are minor and clinically insignificant.

[Correlation between sagittal photogrammetric measurements of the soft tissue profile and dental arches measurements]

INTRODUCTION

Sagittal soft-tissue analyses made from photographic records (sagittal photogrammetric analysis of the soft tissues) allow orthodontists to quantify the sagittal dimension and situation of the facial soft tissues. These tissues maintain close anatomical relationships with the underlying dental arches. However, little importance has been given to the description and the comparison of the sagittal soft tissue morphology according to dental arches parameters. The purpose of this study was to determine the correlation between the sagittal photogrammetric soft tissue profile and the dental arches measurements.

MATERIALS AND METHODS

A cross-sectional study was performed in a group of students. Standardized facial-profile photographs were taken with each student in natural head position, and relaxed lip posture. Photogrammetric parameters were measured on paper sheet using a graduated ruler. Dental arches measurements were also performed directly into the mouth with an electronic caliper. The strength of the association between sagittal photogrammetric soft tissue measurements and dental arches parameters was investigated by a Pearson's correlation. Results were regarded as significant at p=0.05.

RESULTS

The lips protrusion parameters were significantly and positively correlated with the dental arch lengths. The overjet was significantly and positively correlated with Ls/Sn-Sm. The overbite was significantly and negatively correlated with the sagittal labial parameters Ls/N-Ort, Li/N-Ort, Ls-E, Li E, Ls-S, Li S, Ls/Sn-Sm and Li/Sn-Sm.

CONCLUSION

The correlations found in this study show the importance of taking into account the soft tissue in the diagnosis and orthodontic treatment of patients.

The effect of smiling on facial asymmetry in adults: a 3D evaluation

BACKGROUND/AIMS

Mild resting facial asymmetry exists in clinically symmetrical faces, but the effect of smiling on the magnitude of overall facial asymmetry in adults has not been assessed. The aim of the present study was to use stereophotogrammetry to quantify the effect of smiling on overall facial asymmetry in Caucasian adults who presented with Class I incisor relationships and no history of orthodontic treatment.

METHODS

Twenty male and 20 female Caucasians aged 1 8-30 years with no history of orthodontic treatment, a clinically symmetrical face and a Class I incisor relationship had 3D stereophotogrammetric images captured at rest and on natural and maximal smile (T1). The images were repeated 2-4 weeks later (T2) to assess expression reproducibility. Overall facial asymmetry scores were produced from 27 landmarks using partial Ordinary Procrustes Analysis (OPA) and assessed by an Analysis of Covariance (ANCOVA) model. A random sample of the images was re-examined two months later to calculate intraobserver landmark reproducibility.

RESULTS

Mean landmark error was low (0.41 ± 0.07 mm). Mean overall facial asymmetry scores were not significantly gender different (p = 0.5300); therefore, the male and female data were pooled. Mean overall facial asymmetry scores for maximal (0.91 ± 0.16) and natural smile (0.88 ± 0.18) were higher than at rest (0.80 ± 0.17) (p < 0.0001) and were reproducible across (T1-T2) sessions (p = 0.3204).

CONCLUSIONS/IMPLICATIONS

Overall 3D facial asymmetry scores for the sampled Caucasian adults with clinically symmetrical faces increased in magnitude from rest to natural and to maximal smile. Clinicians should assess overall facial asymmetry at rest and on natural and maximal smile at baseline, during treatment and as part of a core outcome assessment, particularly for cases with unilateral posterior crossbite, unilateral cleft lip and palate or skeletal asymmetry.

Extraction vs no treatment: Long-term facial profile changes

INTRODUCTION

Long-term soft tissue response to extraction orthodontic treatment has been a subject of interest for years. The purposes of this study were to investigate long-term soft tissue profile changes in an extraction sample and to compare them with profile changes in an untreated sample.

METHODS

A premolar extraction-treated sample (n = 47) and an untreated control sample (n = 57) were studied. Descriptive statistics were collected, and individual t tests were used for comparison and contrast of the treated and untreated samples.

RESULTS

We found that the untreated soft tissue profile changed in the downward and forward direction. The treated soft tissue profile change was similar, but with more of a forward component than in the untreated sample. Most noteworthy was the finding that the soft tissue profiles of both the untreated and the treated samples were similar at the end point.

CONCLUSIONS

The following conclusions were derived from the study. (1) There was no substantive difference in the soft tissue profiles of the samples, but there were some differences in the directional changes between them. (2) The changes for the untreated sample were the greatest for the lips and the chin, with the change occurring in the downward and forward direction. (3) The soft tissue profiles of the extraction sample also had the greatest measurable changes in the lips and the chin, but the changes had more of a forward component than they did in the untreated sample. (4) Extraction treatment does not adversely impact soft tissue profile changes over time.

Changes in the location of the human mandibular foramen as a function of growth and vertical facial type

OBJECTIVE

A previous cross-sectional investigation showed that the mandibular foramen location depends on the age and the vertical facial pattern of growing individuals. The aim of the present longitudinal study was to explain how these factors influence the distance between the foramen and the occlusal plane. It is known that a certain distance is necessary for a successful inferior alveolar nerve block in clinical dentistry.

MATERIALS AND METHODS

This distance, as well as another four cephalometric variables, were measured on both pre-treatment and 10-year post-treatment lateral cephalometric radiographs collected from 50 patients who underwent orthodontic treatment. The changes between these two sets of measurements were also calculated.

RESULTS

A multiple regression analysis was performed using the pre-treatment age, the pre-treatment inter-maxillary angle, the rotation of the occlusal plane and the change in mandibular ramus height as independent variables and the change of foramen-occlusal plane distance as a dependent variable. The independent variables under investigation were found to account for more than half of the variability of the foramen-occlusal plane distance (r = 0.732; p < 0.001).

CONCLUSION

In very young individuals the mandibular foramen is located approximately at the level of the occlusal plane. With age it moves upwards relative to the occlusal plane and more so for those individuals with a low anterior facial height (short-face vertical facial type). These observations are, at least, partially explained by the differential growth of the various elements of the maxillo-mandibular complex and the change of the inclination of the occlusal plane.

[Sagittal photogrammetric evaluation of the soft tissue profile between two different racial groups: a comparative study]

INTRODUCTION

Facial soft-tissue analyses made from photographic records (photogrammetric analysis of the soft tissues) showed interracial dimorphism. Standard of these facial analyses, originally obtained from Caucasian might not be appropriate for the diagnosis and treatment planning of other groups of orthodontic patients. The purpose of this study was to compare the sagittal photogrammetric soft tissue profile characteristics between Senegalese and Moroccan adults.

MATERIALS AND METHODS

A cross-sectional study was performed in a group of Senegalese and Moroccan students in the Faculty of Medicine, Pharmacy and Dentistry of Dakar. Standardized facial-profile photographs were taken with each student in natural head position, centric relation, and relaxed lip posture. Twenty four linear parameters were measured on paper sheet using a graduated ruler. For each variable mean and SD were calculated. In addition independent samples t-test was performed to detect sexual and racial dimorphism. Results were regarded as significant at p = 0.05.

RESULTS

Senegalese subjects had significantly more lips protrusion than Moroccan who had significantly a more elongated and more anterior positioned nose, a more chin prominence and a tendency to cutaneous class II than Senegalese.

CONCLUSION

Further studies including different age groups subjects would allow having longitudinal data according to age.

Lateral facial profile may reveal the risk for sleep disordered breathing in children--the PANIC-study

OBJECTIVE

To evaluate the lateral view photography of the face as a tool for assessing morphological properties (i.e. facial convexity) as a risk factor for sleep disordered breathing (SDB) in children and to test how reliably oral health and non-oral healthcare professionals can visually discern the lateral profile of the face from the photographs.

MATERIALS AND METHODS

The present study sample consisted of 382 children 6-8 years of age who were participants in the Physical Activity and Nutrition in Children (PANIC) Study. Sleep was assessed by a sleep questionnaire administered by the parents. SDB was defined as apnoeas, frequent or loud snoring or nocturnal mouth breathing observed by the parents. The facial convexity was assessed with three different methods. First, it was clinically evaluated by the reference orthodontist (T.I.). Second, lateral view photographs were taken to visually sub-divide the facial profile into convex, normal or concave. The photos were examined by a reference orthodontist and seven different healthcare professionals who work with children and also by a dental student. The inter- and intra-examiner consistencies were calculated by Kappa statistics. Three soft tissue landmarks of the facial profile, soft tissue Glabella (G`), Subnasale (Sn) and soft tissue Pogonion (Pg`) were digitally identified to analyze convexity of the face and the intra-examiner reproducibility of the reference orthodontist was determined by calculating intra-class correlation coefficients (ICCs). The third way to express the convexity of the face was to calculate the angle of facial convexity (G`-Sn-Pg`) and to group it into quintiles. For analysis the lowest quintile (≤164.2°) was set to represent the most convex facial profile.

RESULTS

The prevalence of the SDB in children with the most convex profiles expressed with the lowest quintile of the angle G`-Sn-Pg` (≤164.2°) was almost 2-fold (14.5%) compared to those with normal profile (8.1%) (p = 0.084). The inter-examiner Kappa values between the reference orthodontist and the other examiners for visually assessing the facial profile with the photographs ranged from poor-to-moderate (0.000-0.579). The best Kappa values were achieved between the two orthodontists (0.579). The intra-examiner Kappa value of the reference orthodontist for assessing the profiles was 0.920, with the agreement of 93.3%. In the ICC and its 95% CI between the two digital measurements, the angles of convexity of the facial profile (G`-Sn-Pg`) of the reference orthodontist were 0.980 and 0.951-0.992.

CONCLUSION

In addition to orthodontists, it would be advantageous if also other healthcare professionals could play a key role in identifying certain risk features for SDB. However, the present results indicate that, in order to recognize the morphological risk for SDB, one would need to be trained for the purpose and, as well, needs sufficient knowledge of the growth and development of the face.

Accuracy of three-dimensional soft tissue simulation in bimaxillary osteotomies

The purpose of this study was to evaluate the accuracy of an algorithm based on the mass tensor model (MTM) for computerized 3D simulation of soft-tissue changes following bimaxillary osteotomy, and to identify patient and surgery-related factors that may affect the accuracy of the simulation. Sixty patients (mean age 26.0 years) who had undergone bimaxillary osteotomy, participated in this study. Cone beam CT scans were acquired pre- and one year postoperatively. The 3D rendered pre- and postoperative scans were matched. The maxilla and mandible were segmented and aligned to the postoperative position. 3D distance maps and cephalometric analyses were used to quantify the simulation error. The mean absolute error between the 3D simulation and the actual postoperative facial profile was 0.81 ± 0.22 mm for the face as a whole. The accuracy of the simulation (average absolute error ≤2 mm) for the whole face and for the upper lip, lower lip and chin subregions were 100%, 93%, 90% and 95%, respectively. The predictability was correlated with the magnitude of the maxillary and mandibular advancement, age and V-Y closure. It was concluded that the MTM-based soft tissue simulation for bimaxillary surgery was accurate for clinical use, though patients should be informed of possible variation in the predicted lip position.

A three-dimensional evaluation of Māori and New Zealand European faces

OBJECTIVE

Māori patients are often inappropriately treated using Caucasian norms, despite obvious differences in facial morphology. There is currently very little data concerning the nature and/or magnitude of these differences in facial features. The objective of the present study was therefore to evaluate the facial features of Māori and New Zealand (NZ) Europeans.

METHODS

Two convenience samples of 30 Māori and 30 NZ Europeans, evenly matched for age and gender, were recruited from amongst students of the University of Otago, New Zealand. Using a 3D white-light scanner, 12 facial scans were taken of each participant, which were then merged to form a single 3D image of the face. Prior to scanning, round markers were fixed to the skin in order to facilitate the localisation of facial anthropometric points and from which vertical, sagittal, and transverse measurements were assessed from the 3D facial image. Univariate and multivariate analyses of variance were used to test for differences between the two groups before and after adjusting for body mass index (BMI).

RESULTS

Significant differences were found in vertical, sagittal, and transverse facial dimensions, before and after adjusting for BMI. The overall face of Māori was significantly larger than that of NZ Europeans, although the facial proportions were generally similar. However, Māori had a broader face, more anterior position of the chin and reduced facial convexity in comparison with NZ Europeans (p < 0.01).

CONCLUSION

Māori have markedly different sagittal facial features compared with NZ Europeans. These distinctive features may reflect important differences in environmental and genetic influences between the two populations. The findings from the present study may assist the clinician in the treatment planning and assessment of facial dysmorphology in these ethnic groups.

Analysis of mental foramen in dry human mandibles of adult Nigerians

OBJECTIVE

This study was undertaken to investigate the dimensions number, shape and actual location of the mental foramen as well as to assess the occurrence of accessory mental foramen in dry human mandibles of adult Nigerians. It also considered the distances between the foramen and some anatomical landmarks.

METHOD

A total of 54 adult dry human mandibles obtained from bone collections in the department of Anatomy of selected Nigerian Universities were used for this study. The sliding digital caliper was used for taking measurements from mental foramen to symphysismenti, posterior border of ramus, lower and superior borders of the mandible. The vertical and transverse diameters of the mental foramen were also measured.

RESULTS

The most common location of the mental foramen was in line with the second premolar tooth (64.8%). The oval shape occurred more (63.6% on the left side and 56.6% on the right side) than the round shape. The dominant mental foramen was single mental foramen (76.9%) and there was no significant association between occurrence, location and shape of mental foramen and sides of the mandibles in this study (P > 0.05).

CONCLUSION

This study will be of clinical relevance to the dentists, oral and maxillofacial surgeons and anaesthetists. It will also be useful to the anthropologists and archeologists in identification and population studies.

Agreement between cranial and facial classification through clinical observation and anthropometric measurement among Envigado school children

BACKGROUND

To evaluate the agreement between cranial and facial classification obtained by clinical observation and anthropometric measurements among school children from the municipality of Envigado, Colombia.

METHODS

This cross-sectional study was carried out among 8-15-year-old children. Initially, an indirect clinical observation was made to determine the skull pattern (dolichocephalic, mesocephalic or brachycephalic), based on visual equivalence of right eurion- left eurion and glabella-opisthocranion anthropometric points, as well as the facial type (leptoprosopic, mesoprosopic and euryprosopic), according to the left and right zygomatic, nasion and gnation points. Following, a direct measurement was conducted with an anthropometer using the same landmarks for cranial width and length, as well as for facial width and height. Subsequently, both the facial index [euryprosopic (≤80.9%), mesoprosopic (between 81% - 93%) and leptoprosopic (≥93.1%)] and the cranial index [dolichocephalic (index ≤ 75.9%), mesocephalic (between 76% - 81%), and brachycephalic (≥81.1%)] were determined. Concordance between the indices obtained was calculated by direct and indirect measurement using the Kappa statistic.

RESULTS

A total of 313 students were enrolled; 172 (55%) were female and 141 (45%) male. The agreement between the direct and indirect facial index measurements was 0.189 (95% CI 0.117-0261), and the cranial index was 0.388 (95% CI 0.304-0.473), indicating poor concordance.

CONCLUSIONS

No agreement was observed between direct measurements conducted with an anthropometer and indirect measurements via visual evaluation. Therefore, the indirect visual classification method is not appropriate to calculate the cranial and facial indices.

Short faces, big tongues: developmental origin of the human chin

During the course of human evolution, the retraction of the face underneath the braincase, and closer to the cervical column, has reduced the horizontal dimension of the vocal tract. By contrast, the relative size of the tongue has not been reduced, implying a rearrangement of the space at the back of the vocal tract to allow breathing and swallowing. This may have left a morphological signature such as a chin (mental prominence) that can potentially be interpreted in Homo. Long considered an autopomorphic trait of Homo sapiens, various extinct hominins show different forms of mental prominence. These features may be the evolutionary by-product of equivalent developmental constraints correlated with an enlarged tongue. In order to investigate developmental mechanisms related to this hypothesis, we compare modern 34 human infants against 8 chimpanzee fetuses, whom development of the mandibular symphysis passes through similar stages. The study sets out to test that the shared ontogenetic shape changes of the symphysis observed in both species are driven by the same factor – the space restriction at the back of the vocal tract and the associated arrangement of the tongue and hyoid bone. We apply geometric morphometric methods to extensive three-dimensional anatomical landmarks and semilandmarks configuration, capturing the geometry of the cervico-craniofacial complex including the hyoid bone, tongue muscle and the mandible. We demonstrate that in both species, the forward displacement of the mental region derives from the arrangement of the tongue and hyoid bone, in order to cope with the relative horizontal narrowing of the oral cavity. Because humans and chimpanzees share this pattern of developmental integration, the different forms of mental prominence seen in some extinct hominids likely originate from equivalent ontogenetic constraints. Variations in this process could account for similar morphologies.

Relationship between dimensions of muscles of mastication (masseter and lateral pterygoid) and skeletal dimensions: study of 40 cases

INTRODUCTION

The masticatory muscles play an important part in determining the morphology of the facial skeleton. Skeletal typology and the characteristics of the masticatory muscles are closely linked. Several authors have studied muscle characteristics as related to facial typology. The aim of this work is to study the relationship between vertical and transverse skeletal dimensions and the dimensions (length, width and thickness) of two muscles of mastication, the masseter and the lateral pterygoid.

MATERIALS AND METHOD

Our study was based on CT-scan examinations of a sample composed of patients consulting the X-ray department of the Rabat-Salé Teaching Hospital, and for whom a CT-scan had been requested. Forty CT examinations of the skull, performed in the context of sinus explorations or pre-surgical work-ups in the radiology department of the Rabat-Salé Teaching Hospital, were selected for this study. The sample comprised 19 women and 21 men aged between 20 and 45, with a mean of 40.9 ± 12.8. A Siemens 32-row 64-slice spiral CT-scan device was used for spiral acquisition of data around the facial bones, with the mouth closed. The study was carried out in the parenchymal window for the muscle measurements, in the axial and coronal planes. Bone measurements were performed after 3D reconstruction in VRT mode.

RESULTS

Our study showed that, for the masseter muscle, thickness is the dimension that correlates significantly with skeletal dimensions in the vertical, transverse and sagittal directions. For the lateral pterygoid muscle, length and width both present significant correlations with transverse skeletal dimensions. Analysis of these results shows that the dimensional characteristics of the masticatory muscles vary according to the vertical and transverse skeletal typology of the subjects concerned.

A 3D anthropometric analysis of the orolabial region in Chinese young adults

The orolabial region undergoes considerable changes after orthognathic surgery or orthodontic treatment. Ethnicity, age, and sex-specific norms are needed during the planning of interventions in this region. In 2008 the Br J Oral Maxillofac Surg published anthropometric measurements of the lips of Chinese children, but to our knowledge such reference data for young Chinese adults are not currently available. We therefore used digital anthropometry on 3-dimensional craniofacial images acquired from 103 healthy young Chinese adults with Class I skeletal pattern. Anthropometric landmarks were identified, which provided linear and angular measurements. All orolabial measurements were significantly larger in men than women, with the exception of the labiomental angle. In contrast, there were no sex differences in the anthropometric proportions. We therefore provide what we think are the first cross-sectional norms available for young Chinese adults. These norms can be used to evaluate the morphology of the lips objectively for preoperative diagnosis, planning of treatment, and assessment of postoperative outcomes.

The influence of lower lip position on the perceived attractiveness of chin prominence

OBJECTIVES

To evaluate the influence of the lower lip prominence for varying degrees of chin prominence in the sagittal plane and to establish whether lower lip prominence affects the perceived desire for surgery. To assess differences in preference between orthodontists and laypeople as well as the effect of age, gender, and ethnicity of observers on perceptions of attractiveness and desire for surgery.

MATERIALS AND METHODS

A silhouette of an idealized profile image was created. The image was manipulated to create six images demonstrating different degrees of retrogenia and progenia altered in 4-mm increments from -12 mm to +12 mm and six images demonstrating chin and lower lip prominence in 4-mm increments from -12 mm to +12 mm. One hundred laypeople and 30 orthodontists ranked the images from the most to the least attractive. A duplicate of one of the images was used in order to assess intraexaminer reliability.

RESULTS

The amount and direction of sagittal chin position and the prominence of the lower lip were found to have a significant effect on image rank. Chin protrusion was less attractive than retrusion and surgery was desired more often for these images. The overall direction of opinion was the same for laypeople and orthodontists.

CONCLUSIONS

The chin prominence observed in a progenic patient is deemed less attractive than the combined chin and lower lip prominence observed in a patient with mandibular prognathism. In profiles with a more prominent chin a more protrusive lower lip position was preferred. When the chin was retrusive, a normal lower lip position was preferred to a retrusive lip.

Differences in craniofacial characteristics in Southern Italian children from Naples: a retrospective study by cephalometric analysis

AIM

The present cross-sectional survey was performed to determine cephalometric standards in a large sample (n. 1071) of children from Southern Italy (Naples).

MATERIALS AND METHODS

1071 lateral cephalograms of healthy children, between 8 to 12 years, with various types of occlusion, all with no history of orthodontic treatment before cephalometric analysis were examined. Seven angular and three linear length measurements (SNA, SNB, ANB, SN^GoMe, PN^Pal I^SN, i^GoMe), and three ratios were included. Descriptive statistics, including the mean, standard deviation, and maximum and minimum, values was computed for each cephalometric variable.

RESULTS

Changes in angular and linear parameters during the observation period occurred mostly between the ages of 10 and 12 years. The three ratios varied from age and were not characterised by a progressive rise in mean values. Se-N/Go-Pg was greater in 11-year-old boys (p <0.05) and 12-year-old boys (p <0.01); the cranio-maxillary index Se-N/PNS-A1 was greater in 9-year-old girls (p <0.05), whereas the maxilla-mandibular index PNS-A1/Go-Pg was greater in 9-year-old boys (p <0.01).

CONCLUSION

The findings provided useful reference cephalometric normative measures for the 8-to-12-year-old Southern Italian children population. Significant differences between boys and girls in the length of the anterior cranial base and ratio were reported.

Reproducibility of facial soft tissue landmarks on facial images captured on a 3D camera

OBJECTIVE

Fast and non-invasive systems of the three-dimensional (3D) technology are a recent trend in orthodontics. The reproducibility of facial landmarks is important so that 3D facial measurements are accurate and may-be applied clinically. The aim of this study is to evaluate the reproducibility of facial soft tissue landmarks using a non-invasive stereo-photogrammetry 3D camera.

MATERIAL AND METHODS

Twenty-four soft tissue landmarks on 3D facial images captured using a VECTRA-3D dual module camera system for full face imaging (Canfield Scientific inc, Fairfield, NJ, USA) were viewed and analysed using Mirror software on 30 adult subjects (15 males and 15 females, in the age range of 20-25 years). The landmarks were identified, recorded and measured twice on each 3D facial image by one examiner after a 2-week interval. Intra-class correlations and paired t-test or Wilcoxon Rank test were performed for each landmark to assess intra-examiner reproducibility.

RESULTS

Intra-class correlation coefficients for all 24 landmarks ranged from 0.68 to 0.97, indicating moderate to high reliability and reproducibility of all facial soft tissue landmarks. Paired t-tests and Wilcoxon Rank test also revealed that there were no significant differences in all 24 facial soft tissue landmarks measurements (p = 0. 17 - 0.99).

CONCLUSION

The results indicated that the reproducibility of identification of landmarks by one operator on facial images captured using a VECTRA-3D camera was acceptable. This device may be useful in treatment planning and may provide accurate information in making clinical decisions. However, it is suggested that further studies on inter-examiner reproducibility should be undertaken.

Geographic variation in chin shape challenges the universal facial attractiveness hypothesis

The universal facial attractiveness (UFA) hypothesis proposes that some facial features are universally preferred because they are reliable signals of mate quality. The primary evidence for this hypothesis comes from cross-cultural studies of perceived attractiveness. However, these studies do not directly address patterns of morphological variation at the population level. An unanswered question is therefore: Are universally preferred facial phenotypes geographically invariant, as the UFA hypothesis implies? The purpose of our study is to evaluate this often overlooked aspect of the UFA hypothesis by examining patterns of geographic variation in chin shape. We collected symphyseal outlines from 180 recent human mandibles (90 male, 90 female) representing nine geographic regions. Elliptical Fourier functions analysis was used to quantify chin shape, and principle components analysis was used to compute shape descriptors. In contrast to the expectations of the UFA hypothesis, we found significant geographic differences in male and female chin shape. These findings are consistent with region-specific sexual selection and/or random genetic drift, but not universal sexual selection. We recommend that future studies of facial attractiveness take into consideration patterns of morphological variation within and between diverse human populations.

The role of the nose and cranial base in profile assessment: a morphological comparison between native African and Caucasian samples

OBJECTIVE

The purpose of this research was to evaluate the position of the nose and how it affects clinical judgment of the face in a native African sample.

METHODS

We considered the anatomic location of the nose with respect to the anterior cranial base (ACB) as well as to the maxillary lip, based on guidelines set down by Holdaway but slightly modified for purposes of this research.

RESULTS

A comparison of the Shona to a Caucasian sample using selected parameters devised by Holdaway (pronasale to labrale superius) indicated that the Shona had a nose and ACB that were shorter than those of the comparative group of Caucasians. The short anterior cranial base was associated with a short and retro-positioned nose which resulted in deceptively protrusive lips when assessed using Ricketts' profile line. Whilst there was no difference in nose depth between the groups, the nasal angle of the Shona was larger than that of Caucasians, indicating an up-tipped nose.

CONCLUSION

The position of the nose has a bearing on orthodontic treatment planning. Understanding the facial morphology of the Shona led us to conclude that conventional soft tissue measurements may not be applicable to all patients who present for orthodontic treatment, and that it may be necessary to advise the patient to seek other avenues for satisfactory management, which, depending on the chief complaint, may include surgical augmentation of the nose and chin.

[The chin fat pad]

The chin fat pad is poorly described in anatomic publications. To improve its knowledge, we performed 10 dissections, we studied 10 CT Scanners and ten RMN from patients without mental scar, and we performed a CT scanner of this area in a man at rest and during the lips protraction. A histological study has been performed comparing the chin fat pad with the subcutaneous fat and the buccal fat pad. The chin fat pad was cylindric, measuring 20 mm long, 7,5 mm wide and 4 mm high. It became thinner during the lips protraction. The histological study revealed a lot of fibrous septa. It was more similar to the subcutaneous fat than to the buccal fat pad.

Influence of chin height on perceived attractiveness in the orthognathic patient, layperson, and clinician

OBJECTIVE

To determine an objective and quantitative evaluation of how severity of chin height variations influence perceived attractiveness.

MATERIALS AND METHODS

The chin height of an idealized male and female frontal facial image was altered in 2.5-mm increments from -12.5 to 22.5 mm (male images) and from -10 to 20 mm (female images). These images were rated on a seven-point Likert scale by a preselected group of pretreatment orthognathic patients, clinicians, and laypeople.

RESULTS

The classical lower facial proportional canon of upper lip height as one third (33.3%), lower lip height as one third (33.3%) and chin height as one third (33.3%) of lower anterior face height (LAFH) may be used as an "ideal" proportional ratio. However, chin height variations within a given proportional range are largely unnoticed, ie, from approximately 30% chin height in relation to LAFH (male and female) up to approximately 40% (males) and 50% (females) chin height in relation to LAFH. Additionally, surgery is only desired with greater variations in chin height: greater than 50% and less than 20%-23% of LAFH in males, and greater than 58% and less than 20%-22% of LAFH in females. Patients and clinicians are more critical than laypeople, but no significant differences were found between clinicians and patients.

CONCLUSIONS

In relation to the classical canon, surgical correction of chin height deformities are desired with chin height greater than 50% and less than 20%-23% of LAFH in males, and greater than 58% and less than 20%-22% of LAFH in females.

The occurrence of phi in dento-facial beauty of fine art from antiquity through the Renaissance

External beauty is a complex construct that influences lives and may be impacted by dentists. Beauty is not easily quantified, but one cited anthropometric of beauty is the ratio phi, the number 1.618033(...). This study examined phi as a measure of female frontal facial beauty in classic Western art, using pre- Renaissance (N = 30), and Renaissance (N = 30) artwork. Four horizontal and five vertical ratios were determined in the works of art, which were then compared with the phi ratio. All horizontal ratios for both pre-Renaissance and Renaissance artwork were similar to each other, but did not contain the phi ratio (P < 0.001). Nevertheless, all vertical ratios for pre-Renaissance and Renaissance art-work did contain the phi ratio within their confidence intervals with the exception of the vertical ratio, "intereye point to soft tissue menton/ intereye point to stomion", that was found to be less than phi in the Renaissance group. The study provides evidence of the presence of the phi ratio in vertical aspect of females in artwork from pre-Renaissance through the Renaissance demonstrating consistent temporal preferences. Therefore, the phi ratio seems to be an important consideration in altering vertical facial dimensions in full mouth rehabilitation and reconstructive orthognathic surgery involving females.

Differences in dentofacial characteristics between southern versus northern Chinese adolescents

AIM

To compare the dentofacial characteristics of southern and northern Chinese adolescents.

METHODS

A southern Chinese sample comprised 70 males (Mean age 12.4 +/- 0.60 years) and 60 females (Mean age 12.5 +/- 0.4 years), and a northern Chinese sample consisted of 50 males (Mean age 12.8 +/- 1.8 years) and 50 females (Mean age 12.4 +/- 1.2 years). All subjects had a Class I molar relationship with no or minimal crowding, a well balanced cephalometric profile, and no history of orthodontic treatment. Patient cephalograms were traced and digitized and McNamara's analysis applied.

RESULTS

A smaller midface and a shorter overall mandibular length were observed in southern Chinese, whereas significantly increased vertical dimension and a retrusive chin were noted in northern Chinese. Protrusive upper and lower incisors and a protrusive upper lip were found in southern Chinese.

CONCLUSIONS

There were significant differences in dentofacial morphology between southern and northern Chinese adolescents. It is suggested that separate cephalometric norms be used for patients originating from different parts of China.

Why do humans have chins? Testing the mechanical significance of modern human symphyseal morphology with finite element analysis

The modern human mandibular symphysis differs from those of all other primates in being vertically orientated and possessing a chin, but the functional significance of this unique morphology is not well understood. Some hypotheses propose that it is an adaptation to specific loads occurring during masticatory function. This study uses finite element analysis to examine these symphyseal loads in a model of a modern human mandible. By modifying the symphyseal cross-sectional form, the mechanical significance of the presence of the chin and symphyseal orientation is tested, and modern human and Neanderthal symphyseal cross-sections are compared with regard to their ability to withstand different loads. The results show that changes in symphyseal form have profound effects on the strains. The presence of a chin leads to lower symphyseal strains overall, whereas a vertical orientation of the symphysis results in higher strains under wishboning, but not under vertical bending in the coronal plane and dorsoventral shear. Compared to Neanderthals, the modern human symphysis shows higher strains during dorsoventral shear and wishboning, but is as effective as the Neanderthal symphysis in resisting vertical bending in the coronal plane and the loads resulting from simulated incision and unilateral molar biting. In general, the results of this study corroborate prior hypotheses about the mechanical effects of the human chin and vertical symphyseal orientation and support the idea that the relative importance of wishboning and vertical bending in the coronal plane might have played a role in the evolution of modern human symphyseal morphology.

Accuracy of fingerbreadth measurements for thyromental distance estimates: a brief report

There have been many contradicting studies as to how well preoperative airway assessments predict difficult intubation. One of these measures, thyromental distance (TMD), has often been called into question. However, there have been no published studies evaluating whether anesthesia practitioners are measuring TMD accurately, especially if they use fingerbreadths as opposed to a centimeter ruler. A convenience sample of 60 anesthesia providers were asked to participate in a brief study. The subjects were asked a series of questions, including the type of anesthesia provider they were, how often they used TMD, and their estimates in centimeters of the following fingerbreadth combinations: index finger, index and second finger, index plus second and third fingers, and index plus second, third, and fourth fingers. After their estimates were recorded, exact measurements of the fingerbreadth combinations were made at the distal interphalangeal (DIP) joints. The differences between the means of the estimated and the actual measurements were analyzed using an independent t test. There was a statistically significant difference between estimated and actual fingerbreadth measurement for the index finger (P < .006) but not for the combinations of fingers.

Esthetic preferences for facial soft tissue profiles

Our aim was to determine any significant difference in esthetic preferences for facial soft tissue profiles among orthodontists, orthodontic patients and their parents. As orthodontic treatment influences facial profiles, the patients' preference for their profile should be sought before treatment, instead of assuming what the orthodontist feels is ideal.

The frontal soft tissue changes in the lower facial portion after orthodontic treatment combined with anterior segmental osteotomy

AIM

To evaluate changes of the lower facial portion on the frontal view before and after orthodontic treatment combined with anterior segmental osteotomy (ASO) in patients with bimaxillary protrusion.

METHODS

The sample consisted of 16 women in the experimental group who had received ASO and 24 women in the untreated control group. Twelve linear measurements, 5 angular measurements, and the lip perimeter and area were measured and analyzed using unpaired and paired t tests.

RESULTS

The upper lip height and lower lip to chin length were significantly greater after treatment. The upper and lower vermilion heights and all vermilion areas decreased significantly, while lip width did not change. Upper lip height was significantly greater in the posttreatment group than in the control group, but there was no difference in upper and total lip areas.

CONCLUSION

Treatment combined with ASO significantly improved the frontal soft tissue proportions. Anticipated frontal soft tissue changes of the lower face should be considered by clinicians for accurate diagnosis and treatment planning.

Comparison of two imaging programs in predicting the soft tissue changes with mandibular advancement surgery

Establishing common objectives and expectations concerning the outcome of proposed surgical orthodontic therapy is a crucial part of the treatment planning process, which has been greatly simplified by imaging software. The purpose of this study was to investigate the reliability of two surgical imaging programs--Dolphin Imaging 10 and Vistadent OC--in simulating the actual outcome of mandibular advancement surgery by using a visual analog scale (VAS) judged by a panel of orthodontists, oral surgeons, and laypersons. The predictions were also analyzed with soft tissue cephalometric evaluation. The results of the study showed that in predicting the surgical outcome evaluated by the VAS, both programs received a mean rating of fair. One was marginally superior for the overall assessment among all three panelist groups. Region-wise, rating indicated the lower lip region to be the least accurate, and the submental region received the highest scores. The soft tissue cephalometric parameters showed minimal differences except for the lower lip parameters. Thus, Dolphin Imaging 10 and Vistadent OC are reliable in predicting mandibular advancement surgical outcomes with inaccuracies chiefly in the lower lip region.

McNamara norms for Turkish adolescents with balanced faces and normal occlusion

BACKGROUND

There are no norms for the McNamara analysis for Turkish adolescents.

OBJECTIVE

To obtain cephalometric standards for the McNamara analysis for Turkish adolescents with balanced faces and Class I occlusions, and to compare the standards with published data.

METHODS

The cephalometric radiographs of 116 children (83 female, 33 male) between 11 and 16 years of age with Turkish grandparents and Class I occlusion, well-aligned upper and lower dental arches, no anterior and/or posterior crossbites and normal dentofacial structures were used. The eight linear and two angular measurements in the McNamara analysis were measured on images of the scanned radiographs. Measurements of the male and female subjects were compared with each other and with published norms for North American adolescents and adults.

RESULTS

The Co-Gn, Co-A, ANS-Me and Ui-A were larger in the male subjects. Comparisons between the present study and McNamara's original study revealed that Anatolian Turkish adolescents, particularly girls, have smaller midfacial and mandibular lengths and longer and more retrusive faces than North American adolescents and adults.

CONCLUSIONS

The small, but statistically significant, gender differences in mandibular and midfacial lengths and lower anterior face height may not be clinically significant. A single set of Turkish norms for the McNamara analysis may be appropriate.

Retrospective evaluation of facial soft tissue cephalometric parameters in adolescents with normal occlusion

Facial soft tissue cephalometric parameters are specific to each society. These measurements should be considered during planning treatment for orthodontic patients. We establish lateral cephalometric facial soft tissue norms in adolescent boys and girls with normal occlusion in Mashhad in the northeast of Iran, and compare them with those of other societies.

Divine proportions in attractive and nonattractive faces

AIM

To test Ricketts' 1982 hypothesis that facial beauty is measurable by comparing attractive and nonattractive faces of females and males with respect to the presence of the divine proportions.

METHODS

The analysis of frontal view facial photos of 90 cover models (50 females, 40 males) from famous fashion magazines and of 34 attractive (29 females, five males) and 34 nonattractive (13 females, 21 males) persons selected from a group of former orthodontic patients was carried out in this study. Based on Ricketts' method, five transverse and seven vertical facial reference distances were measured and compared with the corresponding calculated divine distances expressed in phi-relationships (f=1.618). Furthermore, transverse and vertical facial disproportion indices were created.

RESULTS

For both the models and patients, all the reference distances varied largely from respective divine values. The average deviations ranged from 0.3% to 7.8% in the female groups of models and attractive patients with no difference between them. In the male groups of models and attractive patients, the average deviations ranged from 0.2% to 11.2%. When comparing attractive and nonattractive female, as well as male, patients, deviations from the divine values for all variables were larger in the nonattractive sample.

CONCLUSION

Attractive individuals have facial proportions closer to the divine values than nonattractive ones. In accordance with the hypothesis of Ricketts, facial beauty is measurable to some degree.

Palestinians norms of Steiner cephalometric analysis

AIM

To find the cephalometric norms for Palestinian population according to Steiner cephalometric analysis.

METHODS

Lateral cephalograms of 76 dental students (51 females and 25 males, mean age 20.4 ± 2.1 years) were collected from their files at the American University in Jenin, Palestine. They were scanned and analyzed following Steiner measurements. Means and standard deviations for all variables were calculated. Differences between the mean of the variables for both sexes were calculated using the independent t test.

RESULTS

Females had a smaller interincisal angle, more proclined mandibular incisors, and a shorter anterior cranial base than males in the Palestinian population.

CONCLUSION

When the Palestinian sample population was compared to Steiner norms, similar skeletal patterns were found, but the anterior teeth were more proclined and protruded.

Establishment of South Indian soft tissue cephalometric norms using profile angles and esthetic analysis

AIM

To establish soft tissue norms using profile angles and esthetic analysis in the South Indian population.

METHODS

A clinically effective method is used for accurately placing the esthetic horizontal line on cephalometric radiograph. A series of two vertical lines provides the determinants for the horizontal positions of the soft tissue chin, soft tissue chin thickness, upper lip position and thickness, lower lip, maxillary incisors, and mandibular incisors in relation to the profile. Using these lines, the esthetic analysis is performed on the lateral cephalograms of 90 subjects (38 males and 52 females) of South Indian descent with a well-balanced facial profile and normal occlusion.

RESULTS

A mild convex profile with a mean profile angle of 19.7 ± 2.4 degrees and 19.4 ± 3.2 degrees for males and females, respectively, is esthetically pleasing and encases functionally stable occlusion. There is no statistically significant difference between males and females except for maxillary incisor position.

CONCLUSION

Mild protrusion of incisors with upper and lower lip fullness is an acceptable treatment outcome.

Technical analysis of clinical digital photographs

Clinical digital photography adds an efficient, new dimension to the information provided to the dental technician. Through the use of digital photography, the clinician can create a series of images that communicate key prosthetic facial and dental landmarks for the dental technician to use in analyzing and creating the final prosthesis for the patient.