Proportional analysis of the facial profile in natural head position in Caucasian and Chinese children

A comparative study on anterior teeth retraction-related hard and soft tissue changes with physiologic anchorage control technique

Aim of this comparative cross-sectional study was to evaluate the effect of anterior teeth retraction and related hard and soft tissue change under physiologic anchorage control in patients with chief complain of protrusive teeth. 68 Class I or II orthodontic patients undergoing four-premolar extraction and requiring maximum or medium anchorage were included. Patients were treated with physiologic anchorage control technique (PASS group, n = 34, 18.6 ± 7.7 years, 10 male and 24 female) and self-ligation technique (Damon group, n = 34, 17.5 ± 5.4 years, 13 male and 21 female), respectively. TADs were used for anchorage reinforcement in Damon group. Pre- and post-treatment cephalograms were collected. Twenty-six skeletal, dental and soft tissue items were measured and analyzed using a blinded method. T test and paired rank-sum test were used for statistical analysis. The baseline characteristics were similar between groups (P > 0.05). After treatment, inter-group comparison showed statistically significant differences in the decrease of skeletal measurements ∠ANB (- 0.73 ± 1.05° in PASS group and - 0.25 ± 0.84° in the Damon group), Wits value (- 2.56 ± 2.29 mm in PASS group and - 0.47 ± 2.15 mm in Damon group) and soft tissue measurement UL-E (- 2.75 ± 1.36 mm in PASS group and - 2.03 ± 1.30 mm in Damon group) and the increase of FCA and Z angle, which was 2.03 ± 2.12°and 9.52 ± 4.78°in PASS group and 0.97 ± 2.12°and 6.96 ± 4.43°in Damon group, respectively (P < 0.05). Our results indicated that significant anterior teeth retraction and profile improvement could be achieved with PASS technique without additional anchorage devices. Appropriate application of physiologic anchorage control could reduce the dependence of TADs for anterior teeth retraction.

A Novel Cephalometric Approach Aiming to Quantify a Normal Range of Bony Chin Protrusion

Introduction

Cephalometric analysis is an essential tool in the diagnostics and planning of orthognathic surgery. No objective criterion exists to facilitate decision making regarding genioplasties. Differing opinions amongst clinicians therefore leads to wide variability amongst treatment options offered to potentially suitable patients. This study has three aims. The first was to quantify the distribution of chin morphology amongst the average population using cephalometric analysis. Secondly, we sought to determine whether cephalometric parameters could be used to predict overlying soft tissue changes. Lastly, we consider the use of a new cephalometric angle, BNPg, for pre- and post-operative assessment of genioplasty patients.

Methods

This study retrospectively analysed 231 lateral cephalograms. The angle between the landmarks: B point, Nasion and Pogonion was measured to generate 'BNPg' a novel unit to quantify bony chin protrusion.

Results

The mean BNPg from all 231 samples was 1.12 degrees with a standard deviation of ± 1.35. Comparison between sexes showed no significant differences between male and females (P = 0.108). Furthermore, bony chin protrusion was found to strongly positively correlate with soft tissue chin appearance (r = 0.731), however, BNPg was found not to correlate with skeletal malocclusion (ANB, r = 0.085).

Conclusion

The novel unit BNPg may serve as a useful tool in contributing to the determination of treatment thresholds in osseous genioplasty for desirable aesthetic outcomes and may be used post-operatively to assess outcomes also. As this is a pilot study, further clinical studies would be required to validate this parameter in genioplasty patients, both pre- and post-operatively.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12663-022-01784-5.

Midsagittal Plane First: Building a Strong Facial Reference Frame for Computer-Aided Surgical Simulation

PURPOSE

A facial reference frame is a 3-dimensional Cartesian coordinate system that includes 3 perpendicular planes: midsagittal, axial, and coronal. The order in which one defines the planes matters. The purposes of this study are to determine the following: 1) what sequence (axial-midsagittal-coronal vs midsagittal-axial-coronal) produced more appropriate reference frames and 2) whether orbital or auricular dystopia influenced the outcomes.

METHODS

This study is an ambispective cross-sectional study. Fifty-four subjects with facial asymmetry were included. The facial reference frames of each subject (outcome variable) were constructed using 2 methods (independent variable): axial plane first and midsagittal plane first. Two board-certified orthodontists together blindly evaluated the results using a 3-point categorical scale based on their careful inspection and expert intuition. The covariant for stratification was the existence of orbital or auricular dystopia. Finally, Wilcoxon signed rank tests were performed.

RESULTS

The facial reference frames defined by the midsagittal plane first method was statistically significantly different from ones defined by the axial plane first method (P = .001). Using the midsagittal plane first method, the reference frames were more appropriately defined in 22 (40.7%) subjects, equivalent in 26 (48.1%) and less appropriately defined in 6 (11.1%). After stratified by orbital or auricular dystopia, the results also showed that the reference frame computed using midsagittal plane first method was statistically significantly more appropriate in both subject groups regardless of the existence of orbital or auricular dystopia (27 with orbital or auricular dystopia and 27 without, both P < .05).

CONCLUSIONS

The midsagittal plane first sequence improves the facial reference frames compared with the traditional axial plane first approach. However, regardless of the sequence used, clinicians need to judge the correctness of the reference frame before diagnosis or surgical planning.

Racial disparity of Crouzon syndrome in maxilla and mandible

The racial disparity of facial features in craniosynostosis patients is not fully understood. The aim of this study was to explore the difference in maxillary and mandibular morphology and spatial position in Asian and Caucasian Crouzon syndrome patients. Ninety-one computed tomography scans were included (12 Asian Crouzon syndrome patients, 22 Asian controls; 16 Caucasian Crouzon syndrome patients, 41 Caucasian controls) and measured using Materialise software. The maxillary and mandibular volumes of Asian patients were both reduced by 19% (P=0.102 and P=0.187), and those of Caucasian patients were reduced by 15% (P=0.142) and 14% (P=0.211) when compared to the respective race-specific controls. Maxilla length of Asian patients was reduced by 6.36mm (14%, P=0.003), while the reduction in Caucasian patients was 4.88mm (10%, P=0.038). ANS was retracted 11.99mm (P<0.001) in Asian patients and 11.54mm (P<0.001) in Caucasian patients. The ANB angle was narrowed by 13.17° (P<0.001) in Asian patients compared to Asian controls, and by 7.02° (P<0.001) in Caucasian patients compared to Caucasian controls. The retrusive midface profiles of Asian and Caucasian Crouzon syndrome look similar; both result from the combined effect of hypoplastic size and backward displacement. However, the insufficiency was found to be more a failure of the anteroposterior maxillary length in Asian patients, and more due to posterior maxillary positioning in Caucasian patients. Therefore, prognathism in Crouzon syndrome patients is more likely caused by displacement rather than elongation of mandibular length in both races. Crouzon syndrome results in the same extent of overall volume deficiency of the maxilla and mandible in these races.

Soft tissue norms: Conventional and based on true vertical in a Lebanese population

INTRODUCTION

The aim of this study was to establish cephalometric soft tissue norms in a Lebanese population of young adults and profile differences between males and females.

MATERIALS AND METHODS

Ninety subjects divided into 43 women and 47 men, aged from 18 to 30 years, were selected based on specific criteria. The lateral cephalograms were taken in the natural head position. Holdaway, Steiner, Merrifield, Ricketts, Epker and Fish analyses were applied as conventional analyses. Scheideman, Spradley, Cooke, Arnett, Bergman, Farkas and Viazis analyses were applied as analyses based on the true vertical.

RESULTS AND CONCLUSION

The specific soft tissue measurements of this sample are reported in six grids. The differences between males and females related especially to the lower facial height and lip thickness, which had higher values in males, who also presented a more retruded lower lip and more protruded nasal tip. Women had higher values for mentolabial and frontonasal angles.

Cephalometric norms for the upper airway of 12-year-old Chinese children

Objective

To establish cephalometric norms for the upper airway of 12-year-old Chinese children, and to assess these norms with regard to gender, age, ethnicity and other craniofacial structures.

Methods

Lateral cephalograms were obtained from a random sample of 425 12-year-old Chinese children (224 boys and 201 girls) to establish the Chinese norms, and from a matched group of 108 12-year-old Caucasian children (61 boys and 47 girls) as an ethnic comparison. Published data on the upper airway norms of Chinese adults were used to make age comparisons. Nine upper airway and 14 craniofacial variables were measured.

Results

Chinese boys tended to have a thicker soft palate (P = 0.008), and less depth in the retropalatal (P = 0.011), retroglossal (P = 0.034) and hypopharyngeal (P < 0.001) pharynx than Chinese girls, whereas no gender dimorphism was found in Caucasian children. Ethnic differences were found in the depth of the retroglossal oropharynx in both genders and the position of the hyoid bone in boys. Compared with Chinese adults, the overall size of the upper airway in Chinese children was smaller. The mandibular body length and the craniocervical inclination were found to be statistically significantly, albeit weakly correlated with upper airway variables.

Conclusions

Cephalometric norms for the upper airway of Chinese 12-year-old children were established, indicating gender-specific differences, and some ethnic differences were found in comparison with those of 12-year-old Caucasian children. An association between the mandibular body length and the craniocervical inclination with upper airway variables was also noticeable.

Angular photogrammetric comparison of the soft-tissue facial profile of Kenyans and Chinese

The purpose of this study was to determine the average angular dimensions that define the normal soft-tissue facial profiles of black Kenyans and Chinese and compare them with each other and with values proposed for whites. Standardized facial profile photographs, taken in natural head position, of 177 black Kenyans and 156 Chinese with normal occlusion and well-balanced faces were analyzed for 12 angular parameters. Two-sample t-tests were used to determine sex and racial differences. Kenyan and Chinese averages were compared with proposed white values using 1-sample t-tests. Eight parameters in Kenyans and 7 in Chinese showed sex differences. All angles, except for facial convexity, nasal dorsum, and inferior facial height, were different between Kenyans and Chinese. Kenyan and Chinese averages for all parameters were different from proposed white average, except for facial convexity. Nasolabial and mentolabial angles showed large individual variability and racial differences. The study demonstrated many differences in average angular measurements of the facial profiles of black Kenyans, Chinese, and white standards. Orthodontists, maxillofacial and plastic surgeons, and other clinicians working in the craniofacial region should bear these in mind when setting aesthetic treatment goals for patients of different races. Mean values from this study can be used for comparison with similar records of subjects with same ethnicity.

Soft Tissue Cephalometric Standards based on NHP in a Sample of Iranian Adults

BACKGROUND AND AIMS

This study aimed to establish soft tissue cephalometric standards in Iranian adults based on NHP, which can be used in diagnosis of orthodontic and orthognathic patients.

MATERIALS AND METHODS

A group of 46 individuals (24 males and 22 females) with normal occlusion and proportional facial profile were chosen from a large group of dental students. For the all of the chosen sample, lateral cephalograms were obtained with head oriented in natural position. On the basis of the true horizontal and true vertical lines, the standard values of 19 soft tissue measurements were determined using McNamara, Burstone and Viazis methods.

RESULTS

In this study, the mean value of SN deviation to true horizontal line was 6.6°. Comparison between two genders showed that females have more obtuse nasolabial angle and thinner soft tissue chin than males (P < 0.05). Linear measurements showed that the overall size of males was more than females (P < 0.05).

CONCLUSION

Cephalometric norms based on NHP were found to be more reliable in orthognathic pa-tients.

Fourier analysis of facial profiles of young twins

Twins studies provide a powerful approach to determining the relative contribution of genetics and environment to observed variation. Such studies assume trait differences in monozygous (MZ) twins are due to environmental factors and those in dizygous (DZ) twins are due to both genetic and environmental factors. This study quantitated facial profiles of twins using Fourier equations, determining their value in profile analysis and the assessment of the genetic contribution to facial shape. Standardized profile slide photographs of 79 pairs of 4-6 year-old twins (37 MZ pairs, 42 DZ pairs) were scanned and x and y coordinates were extracted from each profile using sellion and Camper's plane as references. The coordinates were subjected to Fourier analysis and the normalised vertex projection coefficients were studied. The means of the differences between coefficients for MZ co-twins did not differ significantly from that of DZ co-twins, although the DZ group showed higher mean differences in the higher harmonics. Subjective examination of superimposed reconstructions showed wider variation between DZ co-twins than MZ co-twins. Correct classification of twins by discriminant function analysis using Fourier coefficients was similar for both groups (MZ: 70.3%; DZ: 73.8%). Fourier analysis could quantitate facial profiles of young children and differentiate some details, but was unable to discriminate between genetic and environmental influences, and any possible interactions between these influences, on their overall facial profiles at this developmental stage.

Cephalometric morphology of Chinese with Class II division 1 malocclusion

AIM

To investigate the craniofacial pattern of southern Chinese children with Class II Division 1 malocclusion and to compare with Chinese population norms and Caucasians with Class II Division 1 malocclusions.

MATERIALS

Lateral cephalograms obtained from 105 Chinese subjects with Class II Division 1 malocclusion.

RESULTS

There were no significant sex differences and subsequently the data were pooled. Except for the maxillary plane angle and the angle of the lower incisor relative to the mandibular plane, all of the selected dental-skeletal angular measurements showed significant differences between Chinese with Class II Division 1 malocclusion and Chinese norms.

CONCLUSION

Compared with Caucasians, Chinese with Class II Division 1 malocclusion have more prognathic maxillas, less retrusive mandibles, flatter chins, steeper mandibular plane angles and more proclined maxillary incisors.