Relationships between soft tissues in a posed smile and vertical cephalometric skeletal measurements

Three-dimensional analysis of posed smile in adults: A scoping review

This scoping review investigated the evidence on the three-dimensional analysis of a posed smile in adults to discover any research gaps in this research area. Electronic searches of articles written in English were performed using the four databases of Embase, PubMed, Springer, and Web of Science with publications from 2010 to 2023. Reference lists were also manually searched to identify additional studies. The results showed that 13 cross-sectional descriptive studies from Asia, Europe, North and South America met our inclusion criteria. Studies mainly focused on linear and angle measurement for resting and smiling faces and landmark movement from resting to smiling. Most studies conducted analysis of smiles stratified by sex, ethnicity, smile type, dental occlusion, skeletal pattern, and age. Two studies compared smiling with the resting position and one study compared the attractive smiling group with the ordinary group. Our scoping review revealed the insufficiency of some measurement methods, such as those employing area, volume, and soft tissue thickness. Furthermore, few studies were conducted in Asian populations, and comparisons of various smile types, overjet types, horizontal skeletal patterns, and comparisons of smiles between people with untreated normal occlusion and those who had been orthodontically treated were lacking.

Malocclusion severity and smile features: Is there an association?

INTRODUCTION

This observational study investigated the relationship between malocclusion and smiling.

METHODS

Adolescents and young adults (n = 72; aged 16-25 years) were identified according to their Dental Aesthetic Index (DAI) and allocated to 3 groups: (1) malocclusion group (n = 24; DAI ≥31), (2) retention group (n = 24; pretreatment DAI ≥31) with a prior malocclusion that had been corrected by orthodontic treatment, (3) control group with no-to-minor malocclusion (n = 24; DAI ≤25). Participants were requested to watch an amusing video. Based on the Facial Action Coding System, automated pattern recognition was used to detect smile episodes and assess their frequency, duration, genuineness, intensity, and extent of tooth show. Demographics, Big Five personality dimensions, and self-perceived smile esthetics-related quality of life were collected from all participants via questionnaires. Data were analyzed by mixed-model analysis and adjusted for possible confounders.

RESULTS

Patients from the malocclusion and retention groups smiled significantly less than participants from the control group, with the duration of smiles and smiling time being around half those of control subjects. Smile genuineness, smile intensity, and teeth shown did not differ across groups. Personality traits did not differ significantly among the 3 groups, whereas the malocclusion group scored around 30% less for dental self-confidence than the other 2 groups.

CONCLUSIONS

Patients with severe malocclusion tend to smile less, but the features of their smiles are similar to those without malocclusion. A lower propensity to smile in patients with a corrected malocclusion may persist after orthodontic treatment.

Dentogingival display through lip border movements: Report of the Committee on Research in Fixed Prosthodontics of the American Academy of Fixed Prosthodontics

STATEMENT OF PROBLEM

Dentists strive to create natural looking teeth for their patients. However, much of the research on esthetic dentistry has used artificial and computer-generated images to establish esthetic norms. Altered images are helpful in determining personal preferences but may be misleading for natural norms.

PURPOSE

The purpose of this report from the Committee on Research in Fixed Prosthodontics of the American Academy of Fixed Prosthodontics was to establish an evidence base for clinical guidelines on lip mobility and the visibility of oral tissues.

MATERIAL AND METHODS

A systematic search was conducted to collect data on the lip border movements and the visibility of teeth and gingiva of human participants.

RESULTS

One thousand and ninety-six articles were processed, and, based on inclusion criteria, 48 articles were reviewed. The findings determined that the upper lip lengthens with age resulting, at rest, in less display of the maxillary teeth and more of the mandibular arch. When evaluating the maxillary incisal edge position at rest, the canines are the most reproducible. Women tend to display more gingiva in a social smile than men, but this may not be so for a true smile of joy. Both the middle and lower facial thirds should be evaluated to detect a maximal smile. Care must be taken not to classify a person incorrectly as having a low smile line because they could still have a potential to show gingiva.

CONCLUSIONS

Evidence-based clinical guidelines are offered to reduce the risk of esthetic failures.

Evaluation of smile characteristics of skeletal Class III compared to skeletal Class I female adults

OBJECTIVE:

Esthetic enhancement plays an important role in orthodontic treatment. This study was conducted on females as most girls have their growth spurt at a younger age than boys do, so their demand to facial esthetics, especially those who have residual growth of mandible producing class III effect, requires full understanding to smile features helping in diagnosis and treatment planning for maximum patient satisfaction.

MATERIALS AND METHODS:

This study was conducted on 30 skeletal Class III and Class I female adults (18–30 years old) who were divided equally into two groups comprising 15 each. Two frontal digital photographs were taken for each subject, one at rest and the other in the posed smile position. Photographs were taken for each subject in the natural head position by a Canon EOS 1200 D camera set on a tripod at a distance of 1.5 m. The incisogingival height of the right maxillary central incisor was clinically measured using a vernier caliper to the nearest 0.1 mm. Photographs were uploaded on Photoshop software for standardization and then uploaded on the Digital Smile Design software (DSD) where the actual incisogingival height of the central incisor was used for automatic calibration. Esthetic components at rest and on smiling were measured for both groups; all linear variables were measured to the nearest 0.1 mm.

RESULTS:

Class III females tended to have wider smile widths, less gingival display, longer chin heights, shorter lower vertical dimensions, and a higher percentage of nonconsonant and flat smile arcs than Class I subjects.

CONCLUSIONS:

The components of the smile should be considered as a guide to help in planning and designing the mechanics during comprehensive orthodontic treatment.

Lip position analysis of young women with different skeletal patterns during posed smiling using 3-dimensional stereophotogrammetry

INTRODUCTION

The aim of this study was to explore the internal relationship between posed smile characteristics, lip position, and skeletal patterns in young women.

METHODS

Fifty women between the ages of 20 and 30 years were enrolled and divided into 3 groups-vertical, average, and horizontal patterns- using the following parameters: FMA, GoGn-SN, and Jarabak ratio. Each subject was scanned in natural head position and with a posed smile. The interlabial gap, intercommissural width, and smile index were calculated. The frontal region was selected as the reference plane for superimpositions. The changes of the lip landmarks in the vertical, sagittal, and coronal directions were investigated.

RESULTS

The smile indexes were listed in the following sequence: vertical < average < horizontal. Significant differences were found in the interlabial gap among the 3 groups. Compared with the average and horizontal groups, the upper lip landmarks of the vertical group showed differences and changed more only in the vertical direction. However, the lower lip landmark showed no differences in any direction.

CONCLUSIONS

Different skeletal patterns have characteristic smile features. The vertical skeletal pattern affects upper lip movements because there is more space for upper-lip elevation. However, the vertical skeletal pattern has no effect on lower lip movement.