Influence of symmetry and balance on visual perception of a white female smile

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.

The Relationship between the Length/Width of the Face and the Length/Width of the Crown of the Permanent Upper Central Incisors

Background: The face, with its attractiveness, is positively connected with self-esteem and interpersonal relationships, and the maxillary central incisors are the most noticeable teeth and crucial for smile aesthetics. The aim of this study is to examine facial and permanent upper central incisors' clinical crown dimensions and their correlations to establish whether there is a relationship between the length/width of the face and the length/width of the clinical crown of the permanent upper central incisors. Methods: This study included 100 subjects (43 males and 57 females) with a mean age of 17.5 ± 3.4 years before orthodontic treatment. Facial length and width were measured using a cephalometer by the same orthodontist and the upper central incisors' clinical crown lengths and widths were measured using a sliding calliper by the same dental student. Data were analysed using SPSS version 29.0, presenting descriptive statistics for age, facial and upper central incisor crown dimensions, and indices. Pearson's correlation coefficient assessed the relationship between facial features and the upper central incisors' crown. The significance level was p ≤ 0.05. Results: Males exhibit a slightly higher mean value of the face length (11.6 ± 0.8 cm) compared to females' face length (11.2 ± 1.1 cm) and a statistically significant (p < 0.05) higher mean value of the face width (11.7 ± 0.8 cm) compared to females (11.1 ± 0.6 cm). The facial index shows no statistically significant gender difference (males: 99.1 ± 8.4; females: 101.2 ± 11.9, p > 0.05). The upper central incisor crown dimensions are without statistically significant differences between gender and tooth side: males have mean value clinical crown lengths of 10.2 ± 1.1 mm (left) and 10.1 mm ± 1.2 (right) while females have 9.9 ± 1.0 mm (left) and 9.8 ± 0.7 mm (right). Clinical crown widths are also comparable (males: left 9.0 ± 0.7, right 8.9 ± 0.6 and females: left 8.8 ± 0.7, right 8.8 ± 0.7), with no statistically significant differences observed. The tooth index shows no statistically significant difference but there is a statistically significant (p < 0.05) correlation between the facial index and tooth index. Conclusions: Knowledge of the presented data is important for diagnosis and treatment planning and may be useful for restorative dentists, orthodontists, prosthodontists, and maxillofacial surgeons to achieve an aesthetic result. Clinically, our study supports the development of more personalized treatment plans.

The knowledge regarding the impacts and management of black triangles among dental professionals and laypeople

This study aimed to assess the knowledge regarding impacts, causes and management of black triangles (BT) among participants from different educational backgrounds including dental students, dentists and laypeople. This descriptive cross-sectional observational research included 435 participants who comprised 4 groups: pre-clinical (3rd year) dental students, clinical (4th and 5th year) dental students, dentists, and laypeople. A constructed self-reported questionnaire was utilized to assess participants' demographic data and their knowledge of the impacts, causes and management of BT. The VAS scale was used to assess participants' ratings for the impacts of BT on esthetics, with 0 meaning no impact and 10 meaning very severe negative impacts. The most reported treatments for BT were "cannot be treated" 99.3% and "non-surgical periodontal treatment" 67.1%. Meanwhile, the least reported was "modify the porcelain" 41.8%. The most reported cause of BT was "periodontal disease" 85.1%. However, the least reported were "parafunction" and "deep implants" 33.1% each. Dental professionals had better knowledge of the causes (t = 8.189, P < 0.001) and management (t = 8.289, P < 0.001) of BT than the non-dental participants. The dentists had the best knowledge, while the laypeople had the least knowledge of the causes (F = 62.056, P < 0.001) and treatment (F = 46.120, P < 0.001) of BT. The knowledge of the causes (t = 0.616, P = 0.538) and treatment (t = 1.113, P = 0.266) for BT was not significantly different between males and females. Age was not significantly related to the total knowledge about the causes (r = -0.034, P = 0.475) or treatment (r = -0.034, P = 0.482) for BT. Dental professionals had better knowledge of the impacts, causes and management of BT than the non-dental participants. The dentists were the best, while the laypeople were the worst in this regard. Age and gender had no relationships with the knowledge of causes or management of BT.

Relationships between perception of black triangles appearance, personality factors and level of education

This analytical cross-sectional study evaluated the perception of black triangles (BT) and examined the relationships between the perception of BT, personality factors, different educational backgrounds and demographic factors. 435 participants were included and divided into four groups: dentists, clinical (4th and 5th year) dental students, pre-clinical (3rd year) dental students, and laypeople. Participants' perception of the attractiveness of smile profiles of maxillary and mandibular anterior dentition with BT was rated using a ten-point VAS scale with 0 being the least, and 10 being the most attractive smile profile. The personality was assessed using the NEO-FFI personality questionnaire. The smile profile with multiple large BT was rated the least attractive for the maxillary (mean = 3.6) and mandibular (mean = 3.9) tested profiles. The smile profile without BT was rated the most attractive for the maxillary (mean = 9.1) and mandibular (mean = 8.8) tested profiles. The dental professionals perceived the maxillary smile profile with multiple large BT as less attractive than the non-dental participants (t = - 2.715, P = 0.007). Being a male, having dental education, having lower Neuroticism scores, as well as having higher Openness, Agreeableness, Conscientiousness, and Extraversion scores predicted and contributed more towards perceiving various tested smile profiles as more attractive. These findings show that black triangles negatively impacts the perception of smile attractiveness, and that personality traits and having dental education impact the perception of smile attractiveness for smiles with black triangles.

Single-Step Full-Face Surgical Treatment of the Facial Profile

The present study was performed to describe how much affordable, feasible, and straightforward is the approach the authors called "single-stage full-face surgical profileplasty," tailored to greatly improve the surgery of the facial profiling setting and achieve complete profile correction at the same time. From January 2010 to May 2019, 113 patients (95 females and 18 males; aged 19 - 63 years) were surgically treated for full-face profile amelioration. Profile correction was performed by using a combination of five procedures out of other various previously experienced: forehead fat grafting, rhinoplasty, lip fat grafting, genioplasty, and submental liposuction. All patients were assessed at 1, 3, 6, and 12 months following surgery for assessing the surgical profile treatment (SPT) outcome and any possible side effects of the combined treatment. Facial profile stability at 1 year was taken as the completion point of this treatment. Arnett et al's "Soft Tissue Cephalometric Analysis" (1999) was used to clinically evaluate the soft tissues before and after the SPT. Patients' satisfaction was measured with the Client Satisfaction Questionnaire-8" at 3 and 12 months after surgery. Statistics were used for Arnett et al's evaluation. Almost all the values were consistent and reached the normal ranges indicated by Arnett et al (p < 0.001), confirming that the desired results of the surgical profileplasty have been achieved. Single-stage full-face surgical profile treatment helps in correcting faults of the global facial deformity, in every single treated area, providing an overall improvement in facial aesthetics and harmony. Obtaining the simultaneous correction in the whole face has also the advantage of avoiding multiple surgical procedures, reducing postoperative discomfort, and the overall risks for the patient due to multiple surgical and anesthetic procedures.

Effect of prerestorative short-term clear aligner therapy in restorative treatment planning

STATEMENT OF PROBLEM

One of the major challenges in restorative dentistry is to provide optimal esthetics in a minimally invasive way. The optimization of dental esthetics and function is directly related to the position and alignment of the anterior teeth, but whether prerestorative clear aligner therapy will enhance esthetics and minimize restorative needs is unclear.

PURPOSE

The purpose of this clinical study was to evaluate the effect of prerestorative maxillary and mandibular second premolar to second premolar clear aligner therapy in minimizing the need for restorative treatment.

MATERIAL AND METHODS

Fifty adult patients treated with clear aligners (Invisalign Go; Align Technology) were included in this study. Previously generated 3-dimensional orthodontic simulations and clinical photographs in the ClinCheck/6.0 software program were used. Three restorative treatment plans for each participant were generated for initial (no aligners), Express (after using 7 aligners), and Lite Packages (after using 20 aligners) by 2 blinded restorative dentistry instructors. The maxillary and mandibular teeth in the smile-line (to the second premolars) were included. Assessment criteria were the estimated number of restorations, restoration surfaces and preparations and incisal edge inclusion, and the need for gingival leveling. The Friedman test and Cochran Q test were used for statistical analyses (α=.05).

RESULTS

A strong positive correlation was found between the 2 instructors (P<.001). Estimated number of restorations (10 [3 to 16]^a) decreased significantly for Express (6 [0 to 14]^b) and Lite Packages (4 [0 to 8]^c) (P<.001). The estimated number of restoration surfaces (28.5 [9 to 48]^a) decreased significantly for Express (15 [0 to 42]^b) and Lite Packages (9.5 [0 to 24]^c) (P<.001). While the estimated number of teeth to be prepared for recontouring (7 [0 to 16]^a) was significantly less for Express (3 [0 to 10]^b) and Lite Packages (0 [0 to 4]^c) (P<.001), the incisal edge inclusion (10 [3 to 16]^a) was significantly less for Express (6 [0 to 14]^b) and Lite Packages (4 [0 to 8]^c) (P<.001). The need for gingival leveling (26 [52%]^a) decreased significantly for Express (20 [40%]^a) and Lite Packages (7 [14%]^b) (P<.001).

CONCLUSIONS

Prerestorative short-term clear aligner therapy might conserve tooth structure and reduce the number of restorations. The application of the Invisalign Lite Package was more effective than the Invisalign Express Package for second premolar to second premolar alignment.

Effect of variations in facial flow curves on the perceptions of smile esthetics by laypeople

STATEMENT OF PROBLEM

Information about the effect of the facial flow concept on the smile esthetic perception of laypeople is lacking.

PURPOSE

The purpose of this study was to determine the effect of the facial flow concept on laypeople's perception of smile esthetics.

MATERIAL AND METHODS

Frontal full-face images of a female volunteer were digitally altered to create commissural line and transverse occlusal plane inclinations, a dental midline shift, and facial asymmetries. A questionnaire was developed, and a single researcher asked 400 evaluators to rate the attractiveness of the different smiles by using a visual analog scale. The subsequent data were analyzed by using 3-factor repeated measures ANOVA and post hoc Bonferroni tests.

RESULTS

Images with commissural line and transverse occlusal plane inclinations pointing toward the green side of the facial flow curve were found to be more attractive than those with inclinations pointing to the red side (P<.001). Asymmetric facial images with the dental midline coinciding with the facial flow curve had higher esthetic scores than those without (P<.001). Images that showed parallelism between the transverse occlusal plane and commissural line inclinations were perceived as more esthetic (P<.001).

CONCLUSIONS

In an asymmetric face model, the degree and direction of commissural line and transverse occlusal plane inclinations and dental midline shift influenced the perceived attractiveness of a smile.

The effect of torque and vertical position of maxillary canine on smile esthetics

INTRODUCTION

Regarding the key role of the maxillary canine in dynamic occlusion and smile esthetics, this study investigated the relation between smile esthetics and maxillary canine torque and vertical position from the viewpoint of orthodontists, general dentists, and laypersons.

METHODS

In this descriptive cross-sectional study, the close-up smile images have been changed using Adobe Photoshop (Adobe Systems, San Jose, Calif). Then, groups of 21 orthodontists, 20 general dentists, and 33 laypersons evaluated the smile attractiveness of the images using a digital version of a visual analog scale. Statistical analysis was performed using SPSS software (version 25; IBM, Armonk, Calif) and Shapiro-Wilk, analysis of variance, and Tukey post-hoc statistical tests. The significance level was set at 0.05.

RESULTS

There was no significant difference in the mean score between the 3 groups of observers regarding the changes in the canine vertical position in none of the variations (P >0.05). Regarding variations in torque, there was a significant difference between the 3 groups of observers in the bilateral 5° torque change. (P = 0.020).

CONCLUSIONS

Unilateral changes in the vertical position had lower scores, which shows that symmetry is very important in smile esthetics. In addition, laypersons did not find torque changes ranging between -15° to 15° a significant factor in smile esthetics. Overall, some adherence to these values will be acceptable in dental treatments.

Intra- and Interrater Agreement of Face Esthetic Analysis in 3D Face Images

The use of three-dimensional (3D) facial scans for facial analysis is increasing in maxillofacial treatment. The aim of this study was to investigate the consistency of two-dimensional (2D) and 3D facial analyses performed by multiple raters. Six men and four women (25-36-year-old) participated in this study. The 2D images of the smiling and resting faces in the frontal and sagittal planes were obtained. The 3D facial and intraoral scans were merged to generate virtual 3D faces. Ten clinicians performed facial analyses by investigating 14 indices of 2D and 3D faces. Intra- and interrater agreements of the results of 2D and 3D facial analyses within and among the participants were evaluated. The intrarater agreement between the 2D and 3D facial analyses varied according to the indices. The highest and lowest agreements were found for the dental crowding index (0.94) and smile line curvature index (0.56) in the frontal plane, and Angle's classification (canine) index (0.98) and occlusal plane angle index (0.55) in the profile plane. In the frontal plane, the interrater agreements were generally higher for the 3D images than for the 2D images, while in the profile plane, the interrater agreements were high in the Angle's classification (canine) index however low in the other indices. Several occlusion-related indices were missing in the 2D images because the posterior teeth were not observed. Esthetic analysis results between 2D and 3D face images can differ according to the evaluation indices. The use of 3D faces is recommended over 2D images to increase the reliability of facial analyses, as it can fully assess both esthetic and occlusion-related indices.

Smile Design: Mechanical Considerations

Smile designing refers to the cosmetic and esthetic dental reconstruction that is visible during smiling. The use of modern digital tools requires adequate knowledge about the tooth shape and shade principles. Mechanical, biological, and psychological factors should be understood and tailor an individualized treatment accordingly to achieve pleasing esthetic outcomes. Dental therapy is becoming more appearance-driven, and thus, both patients and dental clinicians mainly emphasize on cosmetic dental and facial aspects of treatments.

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.

Arch Asymmetry in Patients With Cleft Lip and Palate After Rehabilitation Treatment Using Stereophotogrammetry

ABSTRACT

Arch asymmetry in cleft patients is a current problem that interdisciplinary treatment aims to solve. This research proposed to analyze the final rehabilitation, according to the arch symmetry of these patients. Thirty-five patients aged between 18 and 30 years, rehabilitated with a fixed partial denture or implants in the cleft area. The analysis was performed using digitalized dental casts with a laser model scanner (R700TM; 3Shape A/S, Holmens Kanal 7, 1060, Copenhagen/Denmark), analyzed with a Vectra Analysis Module software program (VECTRA H1; Canfield Scientific, 4 Wood Hollow Road, Parsippany, NJ 07054). Three linear measurements were evaluated, incisal-canine, canine-molar, and incisal-molar distance. The Student t test was applied to test the significance (P = 0.05) of an observed sample by correlation coefficient test (r-value). Female patients showed a significant correlation in arch symmetry. According to the rehabilitation treatment, patients who received implants showed a high correlation and significant symmetry at all maxillary distances. Finally, according to the cleft side in the maxillary dimensions, even though the majority of patients had clefts on the left side, only patients with a cleft on the right side showed symmetry in this area. Patients rehabilitated with implants in the cleft area showed a more symmetrical maxillary arch than those restored with fixed partial dentures.

Morphological features of smile attractiveness and related factors influence perception and gingival aesthetic parameters

INTRODUCTION

In addition to understanding the basic standards of a smile and patient's opinion, dentists should take into account smile aesthetics, an essential factor for optimal outcomes. This study aimed to evaluate the factors that affect the perception of an aesthetic smile and determine its morphological characteristics and measure the gingival aesthetic parameters.

METHODS

In all, 200 Vietnamese aged 18-35 years were recruited to have their spontaneous smiles captured. These smile images were assessed by 50 laypersons and 50 dentists using a visual analogue scale measurement. The images were analysed to evaluate perceptions of evaluators, determine smile attractiveness, and measure gingival aesthetics.

RESULTS

The difference in the judgements of laypersons and dentists, males and females, and laypersons aged 18-25 and 26-35 years were nonsignificant. High or average anterior smile line, parallel smile arc, upward upper lip curvature, second premolars as the posterior-most teeth displayed, smile index of 5.23-5.63, and dynamic smile symmetry of 1 were scored highly on smile attractiveness. The following maxillary gingival aesthetic parameters were preferred: gingival zenith (GZ) of the canine 0.72-0.75 mm apical to the GZ of the central incisor; GZ of the lateral incisor 0.66 mm coronal to the gingival line; gingival line angle of ∼87°; for the central incisor, lateral incisor, and canines, distance from the GZ to the long axis of 1, 0.4, and 0 mm, respectively; interdental papilla height of 4.25, 3.60, and 3.85 mm, respectively; ratio of the distance from the GZ and the interdental papilla tip to the incisal edge of ∼1.74-1.77 mm.

CONCLUSIONS

Factors including profession, gender, and age of evaluators had almost no impact on their perception of aesthetics. Smile attractiveness characteristics and gingival aesthetic parameters have clinical applicability for patient care.

Self-perception and self-representation preference between 2-dimensional and 3-dimensional facial reconstructions among dentists, dental students, and laypersons

STATEMENT OF PROBLEM

Computer-aided design (CAD) software can merge the intraoral digital scan with patient photographs or 3-dimensional (3D) facial reconstructions for treatment planning purposes. However, whether an individual perceives a 3D facial reconstruction as a better self-representation compared with a 2-dimensional (2D) photograph is unclear.

PURPOSE

The purpose of this observational study was to compare self-perception ratings and self-representation preference of the 2D and 3D facial reconstructions among laypersons, dental students, and dentists.

MATERIAL AND METHODS

Three populations participated in the study: laypersons, dental students, and dentists (n=20, N=60). Facial and intraoral features were digitized by using facial and intraoral scanners, and a complete-face smile photograph was obtained. Two simulations were performed for each participant: 2D (2D group) and 3D (3D group) reconstructions. In the 2D group, a maxillary digital veneer waxing from the left to the right second premolars was produced without altering the shape, position, or length of the involved teeth. A software program (Dental Systems; 3Shape A/S) was used to merge the maxillary digital waxing with the full-face smile photograph. One image was obtained for each participant. In the 3D group, a dental software program (Matera 2.4; Exocad GmbH) was used to merge the intraoral and facial scans. Subsequently, 1 video of a 180-degree rotation of each 3D superimposition was obtained. Participants evaluated both superimpositions on a scale from 1 (least esthetically pleasing) to 6 (most esthetically pleasing). Finally, participants were asked which superimposition they preferred for a potential treatment outcome representation.

RESULTS

All the ratings were esthetically pleasing (median group rating 5 or 6). When analyzed solely for differences across occupation groups, ratings for the 2D representation varied significantly across populations (Kruskal-Wallis chi-squared=13.241, df=2, P=.001), but the ratings for the 3D representation did not exhibit statistically significant differences (Kruskal-Wallis chi-squared=4.3756, df=2, P=.112). Ordinal logistic regression revealed no significant main effects but a significant effect of the population×image-type interaction on the esthetic rating. All participants felt well-represented in both the 2D and 3D representations. Also, 40% of dentists, 55% of dental students, and 50% of laypersons preferred the 3D reconstructions. Sex and occupation in general had no effect on the ratings. However, students tended to give higher ratings to the 3D representations of themselves.

CONCLUSIONS

There is no evidence based on the current study that 2D and 3D representations were perceived differently, but representation preferences may depend on a person's occupation. When individuals rated 3D visualization higher than 2D visualization, they strongly preferred the 3D visualization for representing the treatment outcome.

Relationships between the upper central incisor crown forms and degree of labial inclination, overbite, and overjet in Japanese young adults

PURPOSE

The present study aimed to investigate the relationships between the crown form of the upper central incisor and their labial inclination, overbite, and overjet.

MATERIALS AND METHODS

Maxillary and mandibular casts of 169 healthy dentitions were subjected to 3D dental scanning, and analyzed using CAD software. The crown forms were divided into tapered, square, and ovoid based on the mesiodistal dimensions at 20% of the crown height to that at 40%. The degree of labial inclination of the upper central incisor was defined as the angle between the occlusal plane and the line connecting the incisal edge and tooth cervix. The incisal edges of the right upper and lower central incisor that in contact with lines parallel to the occlusal plane were used to determine the overbite and overjet. One-way ANOVA was performed to compare the labial inclination, overbite, and overjet among the crown forms.

RESULTS

The crown forms were classified into three types; crown forms with a 20%/40% dimension ratio of 1.00±0.01 were defined as square, >1.01 as tapered, and <0.99 as ovoid. The labial inclination degree was the greatest in tapered and the least in square. Both overbite and overjet in tapered and ovoid were higher than those in square.

CONCLUSION

Upper central incisor crown forms were related to their labial inclination, overbite, and overjet. It was suggested that the labial inclination, overbite, and overjet should be taken into consideration for the prosthetic treatment or restoring the front teeth crowns.

Influence of lightness difference of single anterior tooth to smile attractiveness

OBJECTIVES

To evaluate the influence of lightness difference of a single anterior maxillary tooth on difference smile attractiveness.

METHODS

A frontal view full-portrait image of a smiling male Caucasian, was digitally modified altering a single tooth, creating a series of images with varying lightness (ΔL) for the maxillary central, lateral and canine. A total of 160 participants (80 dentists, 80 laypersons) were asked to fill out a Visual Analog Scale questionnaire for every image recording smile attractiveness.

RESULTS

For central incisors ΔL≥1 negatively affected attractiveness. There was a higher tolerance for lightness mismatch when one lateral incisor is lighter and the same applies when the canine was darker. Difference in lightness affected smile attractiveness both for dentists and laypersons. No difference between males and females was observed for the dentists. For laypersons, females perceived smiles with lightness difference as significantly less attractive compared to males. Dentist's age did not affect smile attractiveness perception. Younger laypersons perceived darker color, as less attractive.

CONCLUSIONS

Changes in lightness of a single anterior tooth significantly affected smile attractiveness in a different way for the central vs lateral vs canine. For the dentists, age and gender did not significantly affect smile perception, in contrast to laypeople.

CLINICAL SIGNIFICANCE

Lightness differences of a single anterior tooth affects smile attractiveness.

Effects of gingival margin asymmetries on the smile esthetic perception of dental professionals and lay people

OBJECTIVE

To determine the effects of different gingival margin asymmetries of anterior tooth on the smile esthetic perceptions of dentists, prosthodontists, periodontists and lay people.

MATERIALS AND METHODS

A frontal close-up smile photo of a woman was used in this study. Image was digitally altered in order to create gingival margin asymmetries in left maxillary central, lateral incisors, and canines. Four stages of alterations were made in 0.5 mm increments. The final images were randomly assessed by 240 evaluators: 60 dentists, 60 prosthodontists, 60 periodontists, and 60 lay people. Questionnaire was carried out by a single researcher and each rater was asked to evaluate the attractiveness of the smile images by using the visual analog scale. Collected data were analyzed by using one-way ANOVA test with post hoc Scheffé test.

RESULTS

Smiles with 0.5 mm gingival margin asymmetries were found to be more esthetic, while 2 mm gingival asymmetries were less esthetic (P ˂ .001). Lay people's esthetic scores were higher than other groups in all degrees of asymmetries (P ˂ .001). Esthetic scores of canine teeth were higher than, lateral, and central teeth (P ˂ .001).

CONCLUSIONS

As the amount of asymmetries increased, esthetic scores decreased in all groups. Gingival margin asymmetries were less perceptible laterally.

CLINICAL SIGNIFICANCE

This study may help dental professionals to understand which gingival asymmetries are found by patients as esthetic or unesthetic and guides them in their dental treatment, especially in the aesthetic zone.

Layperson and Dental Professional Perception When Evaluating Their Own Virtually 2D or 3D Simulated Esthetic Discrepancies

PURPOSE

To analyze the perceptions of laypersons, dental students, and dentists regarding disparities of the maxillary dental midline and the occlusal plane (OP) when analyzing their own 2D or 3D clinical simulation.

MATERIAL AND METHODS

20 participants per group volunteered (N = 60). Intraoral and facial scans, and a photograph were obtained from each participant. Two simulation groups were created: 2D and 3D groups, which were subdivided into two subgroups. In the first subgroup, the OP was modified by 1-degree increments without changing the maxillary midline. In the second subgroup, the OP was modified by the same increments, but the maxillary midline was altered to match the OP inclination. Participants were asked to rate the simulations on a 1-to-6 scale and a question survey. Ordinal logistic regression (OR) was used to analyze the ratings.

RESULTS

Tilt of the OP had the strongest negative effect on the ratings which was further amplified by the dental midline inclination (OR = 0.122). Midline modification alone did not affect the ratings (OR = 0.744). 3D simulations had a stronger positive effect on the ratings compared to 2D simulations. For dental students, the positive rating effect of 3D simulations was similar to dentists. For laypersons, the positive rating effect of 3D simulations compared to the 2D simulations decreased relative to dentists. The survey revealed that 45% of the dentists, 80% of the students, and 50% of the laypersons preferred the 3D simulation.

CONCLUSIONS

The type of dimensional representation affected the esthetic perception of all participants. 3D simulations obtained higher esthetic ratings for the same esthetic discrepancy than 2D simulations. However, all participants' ratings decreased with increased tilt of the OP and were further decreased with the inclination of the dental midline.

Esthetic dental perception comparisons between 2D- and 3D-simulated dental discrepancies

STATEMENT OF PROBLEM

Intraoral scanners (IOSs), facial scanners (FSs), and computer-aided design (CAD) software programs have become powerful tools for treatment planning. However, discrepancies in perception regarding 2-dimensional (2D) or 3-dimensional (3D) simulations by dentists, dental students, and laypeople have not been analyzed.

PURPOSE

The purpose of this observational study was to analyze the perceptions of laypersons, dental students, and dentists regarding disparities of the maxillary dental midline and the occlusal plane when analyzing the dental discrepancies on 2D- and 3D-clinical simulations.

MATERIAL AND METHODS

A female model was digitized by using an FS, IOS, and a full-face smile photograph. Dental discrepancies were simulated by using a 2D photograph (2D group) and 3D scan (3D group) of the model. In both simulation groups, 2 subgroups were produced. The occlusal plane of the first subgroup was modified in 1-degree increments without changing the dental midline or the position of the maxillary dental incisors. In the second subgroup, the occlusal plane was modified by using the same increments, but the maxillary central incisors and dental midline were altered to match the inclination of the occlusal plane. A total of 300 participants (N=300) were asked to rate the 2D images (N=12) and 3D videos (N=12) on a 1-to-6 scale and answer a questionnaire. Ordinal logistic regression was used to analyze the ratings.

RESULTS

The ratings decreased with the increased tilt of the occlusal plane, and the layperson group gave consistently higher ratings than the other 2 groups. For dentists, the odds of giving a higher versus lower rating decreased by almost a half for each degree of tilt. However, for students, that effect was diminished by a positive interaction term, and for laypersons, the effect was even less. Students gave similar ratings to dentists, but laypersons gave higher ratings. As the age of the participants increased, however, the ratings also increased. The use of 3D versus 2D images had a positive effect on the ratings, but the effect decreased for the student observers and decreased even further for laypersons. Furthermore, midline alteration led to higher ratings but also resulted in worsening of the odds ratio for the tilt. Seventy percent of the dentists, 57% of the dental students, and 52% of the laypersons preferred 2D simulations to 3D simulations.

CONCLUSIONS

Dentists, dental students, and laypersons decreased their ratings with increased inclination of the occlusal plane; however, laypersons still graded all the 2D and 3D images as esthetically pleasant, giving consistently higher ratings than the dentists and dental students. Overall, 3D simulations obtained higher ratings than 2D images, but the positive effect decreased for the student observers and decreased even further for laypersons.