Does the presence of maxillary central incisor edge asymmetry influence the perception of dentofacial esthetics in video analysis?

Esthetic perception of mandibular anterior teeth during speech and dynamic smile

INTRODUCTION

This study evaluated the esthetic perception of the mandibular anterior teeth during speech by comparing the assessments of laypeople (LP) and orthodontists (ODs).

METHODS

A Class I occlusion model was filmed pronouncing "Czechoslovakia" and smiling. Dynamic smile and speech images were extracted and digitally manipulated to create various dental conditions: ideal alignment, mandibular canine extrusion, mandibular incisor crowding, inclined mandibular occlusal plane, mandibular incisor diastema, and mandibular incisor extraction simulation. Forty-eight participants from each group (LP and ODs) evaluated images using visual analog scales. Statistical analysis employed repeated measures analysis of variance with a 5% significance level.

RESULTS

No significant differences appeared between evaluator group means except for the dynamic smile image. Dynamic smile images received the highest scores, followed by aligned and leveled teeth, both showing significant differences (P <0.05) from each other and the remaining images. Inclined occlusal plane and diastema images received the lowest scores. Group evaluations showed distinct patterns: ODs did not significantly differentiate between canine extrusion, crowding, inclined occlusal plane, and diastema images, whereas LP showed no significant differentiation between incisor extraction, canine extrusion, crowding, and diastema images.

CONCLUSIONS

Speech images received lower attractiveness ratings than ideal occlusion in both groups. No significant differences appeared between LP and OD evaluations except for the dynamic smile image assessment.

Perception thresholds of dental and gingival asymmetries by orthodontists, dentists, and laypeople when observing close-up smile images using eye tracking technology

INTRODUCTION

This study aimed to investigate the perception thresholds of dental and gingival asymmetries in close-up smile images for orthodontists, dentists, and laypeople.

METHODS

Seven sets of close-up smile images were created, in which gingival and dental asymmetries were intentionally incorporated using a software-imaging program. The alterations included unilateral changes to the gingival border and incisal edge of the central and lateral incisors and crown width of the lateral incisor. Combination sets of both dental and gingival asymmetries together were also created. Eye-tracking technology was used to assess visual attention by measuring the fixation duration of the area of the alteration of each image by 195 participants in 3 groups: orthodontists, dentists, and laypeople. Statistical analysis was performed using analysis of variance with Bonferroni adjustment for multiple comparisons, to determine the perception thresholds for each group.

RESULTS

Orthodontists and dentists perceived asymmetry of the gingival border of the central incisor at threshold levels of 1 mm, whereas laypeople perceived this asymmetry at 1.5 mm. Dentists and orthodontists were more sensitive to alterations in the gingival border of the lateral incisor, with a threshold of 1 mm, compared with laypeople, who had a threshold of 2 mm. Wear on the central incisor was perceptible at 1 mm for all groups, whereas wear on the lateral incisor was perceptible at 0.5 mm for orthodontists and dentists and 1 mm for laypeople. The perception threshold values for lateral width discrepancy were 2 mm for orthodontists, 3 mm for dentists, and 4 mm for laypeople.

CONCLUSIONS

On the basis of the perception thresholds found in this study, greater visual attention is drawn toward gingival asymmetries located closer to the midline and dental asymmetries that alter the smile arc.

Two- and three-dimensional symmetry of maxillary incisors: A clinical study

OBJECTIVE

To assess the 2D and 3D natural symmetry of the maxillary incisors.

MATERIALS AND METHODS

Maxillary alginate impressions were taken of 59 young adult volunteers. Gender, orthodontic treatment history, and dominant hand were collected. For 2D analysis, a digital caliper was used for measurements on maxillary casts. For 3D analysis, the casts were scanned using a lab scanner, and the labial surface symmetry of contralateral incisors was evaluated. Mann-Whitney tests and Student's t-test were performed, α = 0.05.

RESULTS

Results indicated a lack of identical lengths among contralateral central or lateral incisors, with minimal occurrences of identical width measurements. 68% of central incisors and 73% of lateral incisors showed differences in length exceeding 0.2 mm. Central incisors showed more similarities than lateral incisors in width, with 61% central incisors and 47% lateral incisors having differences under 0.2 mm. The differences between highly asymmetrical contralateral teeth are situated at the transitional lines. The influence of sexual dimorphism, orthodontic factors, and the dominant hand on incisors' symmetry was not statistically significant.

CONCLUSIONS

2D and 3D symmetry of the natural maxillary incisors are rare. 3D symmetry remains consistent across orthodontic treatment status, gender, and dominant hand, suggesting its independence from such parameters.

CLINICAL SIGNIFICANCE

To achieve a natural and aesthetic smile rehabilitation, the symmetry of the maxillary incisors must be well understood. In our study, 2D and 3D symmetry of the maxillary incisors occurred rarely, but central incisors showed more similarities than lateral incisors in width, with differences under 0.2 mm. On the other hand, differences between highly asymmetrical contralateral teeth are situated at the transitional lines. These conclusions should be included in further computer-assisted three-dimensional smile designs.

Laypersons' Esthetic Perception of Different Dentogingival Characteristics Based on Smile Dynamics: Cross-Sectional Study

This study aimed to evaluate laypersons' esthetic perception of different dentogingival characteristics based on smile dynamics. Six voluntary models were selected, with only one presenting dentogingival characteristics within esthetic standards: white teeth, good alignment, and adequate gingival contour. Two videos were then produced. One video focused on the mouth, whereas the other focused on the entire face of the model, to ensure that the dynamics of the smile could be evaluated. For the evaluation, 200 laypeople were asked to rank the models from first to sixth place in their order of preference. Laypeople were required to justify their reasons for choosing the first and last places. The obtained data were subjected to descriptive and inferential statistical analyses. The results showed that smile and face dynamics influenced the perception of dentogingival characteristics and facial esthetics. No significant changes were observed. However, a gummy smile accompanied by dental alterations was observed in the video of the mouth and was masked by the facial set exposed in the video of the face. A diastema between the central incisors was decisive for negative evaluation of both the mouth and face. The standard model was rated as the most pleasing. Smiles and facial dynamics influence the perception of dentogingival characteristics. Smile and facial dynamics influence the perception of dentogingival alterations among Brazilian laypeople. Diastema is an alteration that interferes with the isolated evaluation of the lower third of the face and the facial set.

Effect of clear aligner attachment design on extrusion of maxillary lateral incisors: A multicenter, single-blind randomized clinical trial

INTRODUCTION

Extrusion of maxillary lateral incisors during aligner treatment is a difficult movement to achieve accurately. Despite recommendations regarding attachment design, few studies and no prospective trials compare predictability among attachments. This study aimed to compare the efficacy between optimized and horizontal attachment designs for achieving maxillary lateral incisor extrusion during clear aligner treatment.

METHODS

The study included maxillary lateral incisors in 3 orthodontic practices requiring at least 0.3 mm of extrusion during the first series of 20-25 aligners in patients aged ≥16 years who were scheduled to begin clear aligner treatment (Invisalign; Align Technology, San Jose, Calif). Teeth were randomly assigned to receive optimized (O), rectangular horizontal nonbeveled (H), rectangular horizontal incisally-beveled (HIB), or rectangular horizontal gingivally-beveled (HGB) attachments. After the first series, a blinded evaluator measured extrusion using superimpositions with initial and predicted models. Linear models determined the difference in the predicted extrusion percentage achieved on the basis of attachment design. Other covariates were patient age, sex, number of trays, and self-reported compliance.

RESULTS

Forty patients (74 teeth) were enrolled, and 38 patients (71 teeth) completed the study. Intraexaminer and interexaminer reliability for extrusion measurements was high (intraclass correlation coefficient, 0.985 and 0.991, respectively). The achieved extrusion was significantly less than predicted (mean, 73%; P <0.0001). The average achieved extrusion was 62%, 79%, 78%, and 78% for O, H, HIB, and HGB attachments, respectively, with H significantly more effective than O (P = 0.0403). Horizontal attachments (H, HIB, and HGB combined) were significantly more effective than O attachments (P = 0.0060), with an average difference in achieved extrusion of 14% of the predicted amount (95% confidence interval, 4-23; estimated 76% vs 62%). Horizontal attachments were an estimated 22% more effective than O attachments for extruding maxillary lateral incisors.

CONCLUSIONS

Horizontal attachments are more effective than O attachments for predicted maxillary lateral incisor extrusion between 0.3 and 2.5 mm. The 3 horizontal attachment designs evaluated performed similarly for achieving predicted extrusion.

TRIAL REGISTRATION

This randomized clinical trial was registered and reported at clinicaltrials.gov (NCT04968353).

PROTOCOL

The protocol was not published before trial commencement.

FUNDING

This study was funded in part by the Alexander Fellowship of the Virginia Commonwealth University School of Dentistry, the Southern Association of Orthodontists, and the Virginia Orthodontic Education and Research Foundation. No funding source influenced the study design, the collection, analysis or interpretation of data, writing of the report, or the decision to submit the article for publication.

Subjective and Objective Evaluation of the Symmetry of Maxillary Incisors among Residents of Southwest Poland

Dental aesthetics is an essential factor affecting people’s psychosocial wellbeing. One of the most critical components of an aesthetic smile is symmetry within the dentition. Dentists and orthodontists, unlike laypersons, are critical in assessing dental aesthetics. This study aimed to evaluate the accuracy of patients’ assessment of the symmetry of their maxillary incisors and some factors that influence it. The study was conducted on 83 participants aged from 11 to 39 years. First, the participants filled out a questionnaire to obtain patients’ opinions of the symmetry of their upper incisors. This stage was followed by an intraoral examination, during which we used a digital caliper to measure the width of four maxillary incisors. The data were entered into STATISTICA v. 13.3. The following conclusions were drawn from the study. First, the respondents were generally able to determine the asymmetry of the incisors. Second, among the maxillary incisors, the participants defined the symmetry of maxillary central incisors more accurately than the maxillary lateral incisors. The cut-off value for incisor asymmetry noticeable to a layperson is 0.2 mm for maxillary medial incisors and 0.55 for maxillary lateral incisors. Third, we found no dependence of the accuracy of the assessment of incisor asymmetry on the age of the subjects; however, in our study group, the age range (spread) was not significant, so further studies are recommended. Finally, results concerning the relationship with gender showed that males assess the level of symmetry of their maxillary incisors more accurately than females.

Orthodontists' preferences regarding the difference of bracket bonding height between the maxillary incisors

Introduction:

The vertical position of orthodontic brackets in maxillary incisors may influence the incisal step between the anterior teeth and thereby interfere with the smile esthetics. Even so, esthetic standards have been modified over time and consistently required technical adjustments.

Objective:

This study analyzed orthodontists’ preferences regarding the difference of bracket bonding height between the maxillary central incisors (MCI) and maxillary lateral incisors (MLI), and further determined whether the orthodontist sex, age and time of specialization have association to their choices.

Methods:

This study collected data through an electronic form. Study participants analyzed a clinical case in which they indicated their preference for bracket bonding height. The placement height options ranged from 3.0 mm to 5.5 mm from the incisal edge, with 0.5-mm intervals, or at the clinical crown center (CCC). The difference in the bonding height between the MCI and MLI was analyzed, considering the formation of incisal steps between these teeth.

Results:

Participants indicated that the difference in bracket bonding height between the MCI and MLI should be as follows: 0 mm (3.9%); 0.5 mm (78.3%); 1 mm (7.6%); 1.5 mm (0.2%); and CCC (9.9%). There was no statistically significant correlation between the choice for bracket bonding height and sex, age and time since specialization.

Conclusion:

Most participating orthodontists choose the 0.5-mm difference in bracket placement height between the MCI and MLI. The variables sex, age and time since specialization did not influence this choice.

An analysis of clinical and imaging features of unilateral impacted maxillary central incisors: A cross-sectional study

INTRODUCTION

This cross-sectional study sought to assess clinical features and 3-dimensional distribution of unilateral impacted maxillary central incisors and identify factors associated with the root morphology.

METHODS

Cone-beam computed tomography (CBCT) images from 94 subjects exhibiting unilateral impacted maxillary incisors were selected and evaluated. Original CBCT data were reconstructed using Mimics software (version 17.0; Materialise, Belgium). Clinical features and 3-dimensional distribution of impacted maxillary central incisors and factors associated with the root morphology were observed and analyzed by 2 orthodontists.

RESULTS

This patient cohort included 52 male patients and 42 female patients. Thirty-three incisors (35.11%) with dilacerated roots, 17 incisors (18.09%) with retained deciduous teeth, 15 incisors (15.96%) with supernumerary teeth, and 15 incisors (15.96%) with a history of trauma were identified in the study. Of the 94 impacted incisors, the most common were labially impacted (n = 65; 69.15%), followed by vertically impacted (n = 17; 18.09%) and palatally impacted (n = 12; 12.77%). Chi-square tests revealed that differences in subjects with supernumerary teeth, buccolingual position, sagittal position, and axial position in the upright and dilacerated root groups were statistically significant (P <0.05). Logistic regression analysis indicated that the incidence of dilacerations was higher in the inverted position than in the inclined position and horizontal position (P <0.05).

CONCLUSIONS

Labially impacted maxillary incisors were more common than vertically or palatally incisors. Dilaceration was most commonly observed in patients with inverted incisors. In clinical practice, CBCT is a valuable tool for diagnosing impacted maxillary central incisors and for making appropriate treatment plans for patients.

Longitudinal 3D Study of Anterior Tooth Wear from Adolescence to Adulthood in Modern Humans

Simple Summary

Tooth wear is the loss of tooth substance during everyday functioning by means other than dental caries. It is expected at a certain level in every person, and it increases with age. In the last decades, due to the increased life expectancy and high patient demands, it has become an important problem modern dentistry has to face. However, the average amount of tooth wear among individuals remains controversial. The purpose of this clinical study was to precisely detect the extent of anterior tooth wear over a thirteen-year period, from adolescence to adulthood. The present study revealed the very high tooth wear occurrence in the population already at early adulthood and showed that wear monitoring at an individual level is important for dentists to enable the better understanding of the problem and allow timely targeted interventions for patients in need. These might be preventive, such as the prescription of mouth guards to limit grinding and the cessation of harmful habits that lead to tooth wear, or interceptive, such as the restoration of the lost tooth substance to stop the progress of the condition and improve esthetics and function.

Abstract

In modern humans, tooth wear can easily be observed as a loss of tooth substance, but its precise measurement is problematic. The aim of this longitudinal cohort study was to determine the precise amount of occlusal tooth wear in the anterior permanent dentition from adolescence to adulthood. Corresponding tooth crowns from serial 3D digital dental models of 72 individuals were best fit-approximated by applying novel, highly accurate 3D superimposition methods. The superimposed crowns were simultaneously sliced on intact structures, and the differences in the volumes of the subsequent occlusal parts were calculated. Over a thirteen-year period, there was an average loss of anterior occlusal surfaces of 1.58 mm³ per tooth. Tooth surface loss in at least one tooth was higher than 1 mm³ in 93.1% of the human subjects. Tooth wear severity differed by sex and tooth type, with males showing higher values versus females and upper canines versus other anterior teeth. The study revealed the endemic occurrence of occlusal anterior tooth wear, highlighting the need for monitoring of the condition in the population to identify high-risk patients and enable timely interventions. The novel methods applied here on 3D digital models are recommended for this.

Does the presence of maxillary midline diastema influence the perception of dentofacial esthetics in video analysis?

OBJECTIVE

To evaluate the influence of a midline diastema on dentofacial esthetic perceptions of orthodontists, restorative dental specialists or prosthodontists, and laypersons in a frontal facial evaluation performed by means of video.

MATERIALS AND METHODS

Two individuals aged between 20 and 25 years, one of each gender, with presence of a midline diastema were selected. An acrylic resin mockup was made of the maxillary anterior region, simulating ideal conditions of smile esthetics. Four standardized frontal view videos of the complete face were filmed of each individual in the following situations: with the ideal smile (unchanged mockup) and with the presence of midline diastemas of 0.5, 1.0, and 1.5 mm created by the mockup. In all videos, the patient said a certain sentence and, at the end, simulated a posed smile. Dentofacial esthetic perceptions of all four videos of each individual were evaluated by 51 orthodontists, 51 restorative dental specialists or prosthodontists, and 51 laypersons by means of visual analog scales. Data were evaluated using analysis of variance and Tukey post hoc test, with the level of significance set at 5%.

RESULTS

The most attractive videos for all groups of examiners were those without diastema and with a diastema of 0.5 mm, for both the woman and the man. For a diastema of 1 mm or 1.5 mm, the dentofacial characteristics were considered unesthetic.

CONCLUSIONS

Diastemas equal to or greater than 1 mm negatively influence dentofacial esthetics in a frontal facial evaluation performed by means of video.