Dental Asymmetry Research Articles

Cross-Sectional Study on Self-Perception of Dento-Facial Asymmetry.

Background and Objectives: Facial symmetry is a key component of facial beauty and attractiveness. However, perfect symmetry is rare, and slight asymmetries, also known as natural asymmetries, are common and contribute to the uniqueness of each face. The perception of facial asymmetry varies among individuals and can be influenced by several factors. This study aimed to investigate the self-perception of dento-facial asymmetry among a sample of Romanian individuals, focusing on their awareness, the extent to which it bothers them, and their desire for correction. Materials and Methods: A cross-sectional analytical study was conducted with 283 participants from Romania between January and February 2024. Participants completed a questionnaire designed to assess their self-perception of facial asymmetry and socio-demographic characteristics. The questionnaire included 10 questions on self-perception of facial asymmetry and 8 questions on socio-demographic data. Statistical analysis was performed using SPSS 26.0, and the Pearson Chi-square test was used for comparative analysis. Results: The sample was predominantly female (75.3%) with an average age of 32.24 years. Most participants were from urban areas (80.6%) and had university degrees (58.7%). About 28.7% of participants observed facial asymmetry, with dental asymmetry being the most frequently reported, followed by asymmetries in the eyebrows and eyelids. The right side of the face was more commonly perceived as asymmetric. Although 24.4% of participants were bothered by their asymmetry, 39.2% expressed a desire to correct it. Conclusions: One-third of participants identified dento-facial asymmetry, with the dental level being the most reported. A significant portion of participants expressed a desire to correct their asymmetries, highlighting the importance of understanding self-perception in the context of facial aesthetics. This study underscores the subjective nature of facial asymmetry perception and the varying thresholds for what is considered bothersome or in need of correction.

Three-dimensional evaluation of temporomandibular joint and dental asymmetries in angle class II division 1 subdivision malocclusion

Abstract Background Management of class II division 1 subdivision malocclusion has consistently offered an important challenge for orthodontic professionals. This problem arises not only from the complexities associated with its treatment but also from the complex nature of its asymmetric characteristics. Understanding the properties of asymmetry in this particular malocclusion has significant importance. Objectives Evaluate the features of temporomandibular joint and dental asymmetries in angle class II division 1 subdivision malocclusion by using cone-beam computed tomography (CBCT). Patients and methods Forty CBCT scans of adult patients were analyzed and divided into two groups: 20 CBCT for each group skeletal and dental measurements were measured and compared among both groups to evaluate the features temporomandibular joint and dental asymmetries in class II division 1 subdivision malocclusion. Results Dental parameters were significantly different (P < 0.01) between right and left sides in maxillary sagittal position (mandibular first), maxillary and mandibular canine. A comparison of condyle and glenoid fossa concerning right, and left sides showed together significant an differences (P < 0.01) in coronal position of GFI, GlS, Poi, and posterior wall angle of the articular tubercle. Conclusion In class II division 1 subdivision malocclusion the mandibular first molar was distal and lingual in position, while the maxillary first molar was mesial in class II side. In class ii subdivision malocclusion, glenoid fossa position and condylar morphology asymmetries caused skeletal asymmetry.

Conservative interdisciplinary management for a congenitally missing maxillary lateral incisor in an adolescent patient

AbstractA congenitally missing lateral incisor tooth is commonly associated with both short and long‐term clinical dilemmas, particularly for a growing patient. A unilaterally missing maxillary lateral incisor tooth creates a significant dental asymmetry in the critical aesthetic zone of the smile and potentially increases the difficulty of any subsequent orthodontic and restorative treatment. Carefully planned interdisciplinary management is required to address the challenges of anterior dental asymmetry, unilateral orthodontic space closure and to alleviate the concerns that accompany restorative implant placement in the anterior maxilla. The use of skeletal temporary anchorage devices has increased the predictability of orthodontic space closure, particularly for missing maxillary lateral incisor cases which were previously considered to be unsuitable.

Evaluation of occlusal force in Class II subdivision malocclusion.

Class II subdivision is a malocclusion characterized by dental and functional asymmetry that is difficult to manage. Impaired muscle function can result in asymmetrical growth, leading to occlusal instability. The study aimed to assess occlusal force in patients with Class II subdivision malocclusion using Innobyte. Additionally, the discrepancies of force generated at the position of maximum intercuspidation between the left and right sides of the arches were evaluated. The occlusal force of 66 patients with Class II subdivision malocclusion (group S) was measured and compared with that of 66 patients with Class I (group I) and 66 patients with Class II malocclusion (group II). The S group patients had a Class I molar on the right side and a Class II molar on the left side. ANOVA test, followed by the Games-Howell post hoc test, was performed to compare the mean of the total force among the groups. To assess the difference in force between the right and left arches, one-way ANOVA test followed by Tukey's post hoc comparison was performed. Finally, a boxplot was created to show the trend of occlusal force recorded in the three groups of patients. The occlusal force differed significantly among the groups (p < .001). Post hoc Games-Howell analysis showed significant differences as follows: the total force in group S was 165.24 N greater than in group II and in group I was 218.06 N greater than in group II. The difference (right-left) in total force between the groups was statistically significant (p < .001). Tukey's post hoc test showed following significant correlation: in group S was 53.51 N greater than in group II and 63.12 N greater than in group I. Among the analysed groups, patients with Class II malocclusion exhibited the lowest value of occlusal force. In patients with Class II subdivision malocclusion, force asymmetry, characterised by a higher value on the Class I side and a lower value on the Class II side was observed.

Mirror, mirror? An evaluation of identical twin mirroring in tooth crown morphology.

It has been estimated that 25% of monozygotic ("identical") twin pairs exhibit reverse asymmetry (RA) or "mirroring" of minor anatomical features as a result of delayed zygote division. Here, we examine whether identical twin mirroring accounts for patterns of dental asymmetry in a sample of monozygotic and dizygotic ("fraternal") twins. We focus on crown morphology to approach the following question: is there an association between dental RA frequency and twin type suggestive of the presence of mirror image twins in our sample? Data were collected from 208 deciduous and 196 permanent dentitions of participants of the University of Adelaide Twin Study using Arizona State University Dental Anthropology System standards. RA frequencies were compared across morphological complexes (deciduous, permanent), twin types (monozygotic, dizygotic), and traits. Fisher's exact tests were performed to formally evaluate the association between twin type and dental RA. Across the entire dataset, RA rates failed to exceed 8% for any twin type. In monozygotic twins, deciduous mirroring totaled 5.3% of observed cases, while permanent mirroring totaled 7.8% of observed cases. We found no statistically significant association between RA and twin type for any morphological character (p-value range: 0.07-1.00). Our results suggest the timing of monozygotic twin division does not explain the structure of asymmetry for our morphology dataset and that published estimates of identical twin mirroring rates may be inflated or contingent upon phenotype. Instead, rates reported for this sample more closely align with the proposed etiology of this condition.

Asymmetry in Class II subdivision malocclusion: Assessment based on 3D surface models.

There is currently no consensus in the literature whether the aetiology of a Class II subdivision is dental, skeletal or both. The aim of this study was to identify and quantify skeletal and dental asymmetries in Class II subdivision malocclusions. CBCTs from 33 Class II subdivision malocclusion patients were used to construct 3D volumetric label maps. Eighteen landmarks were identified. The original scan and associated 3D volumetric label map were mirrored. Registration of the original and mirrored images relative to the anterior cranial base, maxilla and mandible were performed. Surface models were generated, and 3D differences were quantified. Statistical analysis was performed. Anterior cranial base registration showed significant differences for fossa vertical difference, fossa roll, mandibular yaw, mandibular lateral displacement and lower midline displacement. Regional registrations showed significant differences for antero-posterior (A-P) mandibular length, maxillary roll, A-P maxillary first molar position, maxillary first molar yaw and maxillary first molar roll. Class II subdivision patients also show an asymmetric mandibular length as well as an asymmetric gonial angle. Moderate correlations were found between the A-P molar relationship and fossa A-P difference, mandibular first molar A-P difference, maxillary first molar A-P difference and maxillary first molar yaw. This study suggests that Class II subdivisions can result from both significant skeletal and dental factors. Skeletal factors include a shorter mandible as well as posterior and higher displacement of the fossa on the Class II side, resulting in mandibular yaw. Dental factors include maxillary and mandibular first molar antero-posterior asymmetry.

Perception of facial and dental asymmetries and their impact on oral health-related quality of life in children and adolescents.

The aim of this study was to investigate the perception of facial and dental asymmetries in children and adolescents and how these asymmetries affect their psychosocial and emotional well-being. The study included 66children and adolescents (7-15years) with adeviation between the maxillary and mandibular dental midlines of > 0.5 mm. The soft tissues of the face were scanned using stereophotogrammetry. Psychosocial and emotional impairments were assessed using the German version of the Child Perceptions Questionnaire (CPQ-G8-10 and 11-14). The mean midline deviation of the study group was 2.3 mmwith no significant gender differences. Girls perceived facial asymmetry significantly more often than boys (p < 0.01). However, stereophotogrammetry showed no significant differences in facial morphology between subjects who perceived their face as asymmetrical and those who perceived it as symmetrical. Interestingly, we observed asignificant correlation between the deviation of the dental midline and the lateral displacement of gonion (p < 0.05) and cheilion (p < 0.01). Psychosocial and emotional impairment was significantly higher in girls than in boys (p < 0.05). However, there was no significant correlation with the measured facial asymmetries. In contrast, the CPQ subscale score was 2.68points higher in individuals with adental midline shift ≥ 3 mm (p < 0.01), independent of age and gender. Although girls perceived facial asymmetries more strongly than boys do, this perception could not be objectified by extraoral measurements. Amidline shift of 3 mm or more had anegative impact on the oral health-related quality of life of affected children and adolescents.

Review of Properties, Uses and Limitation of TransPalatal Arch (TPA) in Orthodontic Treatment

The advancement of technology has brought some successful and progressive innovative methodologies in treating orthodontic conditions such as unilateral cross-bite, protrusive malocclusion, molar derotation, dental asymmetry and premature loss of primary molar teeth.

Dental Anomalies in Maxillary Incisors and Canines among Patients with Total Cleft Lip and Palate

Cleft lip and palate is the most common asymmetric congenital condition of the orofacial region, which also finds its reflection in dental anomalies. The aim of the study was to present the dental asymmetries of the front region of the maxilla in cleft patients. Materials and Methods: We analyzed plaster casts and panoramic X-rays of 154 patients with total clefts and 151 healthy individuals. The cleft patients’ age ranged between 7.1 and 20 years (mean 13.18). The control group had a similar age range (7.1 and 20 years, mean 13.44). The digital caliper was used to measure the width of the teeth. Each measurement was performed three times each. Results: Most of the dental anomalies among cleft patients referred to the lateral incisors and were focused on the cleft side. The asymmetry of the incisors is reflected both in the number of teeth in the cleft region and their width. The lateral incisor was missing twice as frequently on the cleft side of the individual. If present, the lateral incisor was usually ±1.5 mm narrower than the incisor on the opposite side. In bilateral clefts, dental anomalies occurred more frequently on the left side. Conclusions: Dental problems occurred more frequently in patients with total cleft lip and palate than in healthy individuals. The most commonly affected teeth were the lateral incisors. The width of the lateral incisors was reduced in cleft patients—showing a smaller mesiodistal dimension on the cleft side.

Early Treatment of Unilateral Condylar Hyperplasia in Adolescents: Preliminary Results.

Facial asymmetry associated with unilateral condylar hyperplasia (UCH) is a rare disease. The aim of this study was to evaluate the clinical conditions of progressive facial asymmetry in young subjects treated with high condylectomy. A retrospective study was performed including nine subjects diagnosed with UCH type 1B and progressive facial asymmetry around 12 years old with an upper canine progressing towards dental occlusion. After an analysis and a decision of treatment, orthodontics began one to two weeks prior to the condylectomy (with a mean vertical reduction of 4.83 ± 0.44 mm). Facial and dental asymmetry, dental occlusion, TMJ status and an open/closing mouth were analyzed before surgery and in the final stage of treatment, almost 3 years after surgery. Statistical analyses were performed using the Shapiro-Wilk test and a Student's t-test considering a p value of <0.05. Comparing T1 (before surgery) and T2 (once orthodontic treatment was finalized), the operated condyle showed a similar height to that observed in stage 1 with a 0.12 mm difference in height (p = 0.8), whereas the non-operated condyle showed greater height increase with an average of 3.88 mm of vertical growth (p = 0.0001). This indicated that the non-operated condyle remained steady and that the operative condyle did not register significant growth. In terms of facial asymmetry in the preoperative stage, a chin deviation of 7.55 mm (±2.57 mm) was observed; in the final stage, there was a significant reduction in the chin deviation with an average of 1.55 mm (±1.26 mm) (p = 0.0001). Given the small number of patients in the sample, we can conclude that high condylectomy (approx. 5 mm), if performed early, especially in the mixed-dentition stage before full canine eruption, is beneficial for the early resolution of asymmetry and thus the avoidance of future orthognathic surgery. However, further follow-up until the end of facial growth is required.

Non-Surgical Camouflage Treatment of a Skeletal Class III Patient with Anterior Open Bite and Asymmetry Using Orthodontic Miniscrews and Intermaxillary Elastics

This case report presents the non-surgical orthodontic camouflage treatment of an 18-year-old male patient with skeletal Class III asymmetry and severe anterior open bite. The anterior open bite was corrected by extrusion of the maxillary and mandibular anterior teeth and clockwise and counterclockwise rotation of the maxillary and mandibular occlusal plane, respectively, using intermaxillary Class III elastics between the maxillary posterior buccal miniscrews and mandibular canines and anterior vertical elastics between the maxillary and mandibular canines. Class III dental relationships and dental asymmetry were corrected via unilateral distalization of the mandibular dentition on the left side using a closed coil spring between the buccal shelf screw and hook. The patient’s smile esthetics and dental relationship were improved with a more favorable facial profile, and facial asymmetry was slightly alleviated after orthodontic camouflage treatment. The total treatment time was 15 months. A modified wraparound retainer with a scalloped labial bow, tongue crib, and tooth positioner was used simultaneously to prevent the potential relapse.

The association between dental and facial symmetry in adolescents

Facial aesthetics have become one of the most important objectives of orthodontic treatment. The correction of dental arches should be performed in accordance with the face. This study explored the association between occlusal and facial asymmetries in adolescents, particularly emphasizing a Class II subdivision. Eighty-one adolescents (43 males, 38 females) with a median age of 15.9 (interquartile range, 15.17-16.33) years were enrolled. Of these patients, 30 had a Class II subdivision (right side, n= 12; left side, n= 18). Three-dimensional facial scans were analyzed using surface- and landmark-based methods. Chin asymmetry was determined using the chin volume asymmetry score. Three-dimensional intraoral scans were analyzed to assess occlusal asymmetry. The surface matching scores were 59.0% ± 11.3% for the whole face and 39.0% ± 19.2% for the chin. Chin volume was larger on the right side than on the left side in most patients (n= 51, 63%), and it was associated with a dental midline shift to the corresponding subdivision side. A correlation between dental and facial asymmetries was noted. In addition, the dental midline shifted to the left in patients with a Class II subdivision, regardless of the side, and to the right in those with a symmetrical Class II subdivision. However, several patients did not possess asymmetrical occlusal traits sufficient for statistical analysis. Dental asymmetry was weak but significantly correlated with facial asymmetry.

Normal variation of mandibular asymmetry in children.

To explore the normal variation of asymmetry in mandibles of children in the age group of 1 to 12 years. The study group consisted of 92 cadaveric mandibles of children with a dental age of 1 to 12 years old in possession of ACTA (Academic Centre for Dentistry Amsterdam), Faculty of Dentistry, the Netherlands. 3D models of the mandibles were obtained from CT-scans and hemimandibular volumes of all mandibles were calculated. The condylar height, ramus height, mandibular body length and the gonial angle were bilaterally determined using a novel landmark-based method, and the degree of asymmetry was calculated. No relationship was found between dental age and asymmetry of the studied parameters (P < .05). The highest degree of asymmetry was found in the ramus height, whereas the gonial angle presented the lowest degree of asymmetry. A positive correlation was found between the asymmetry of the hemimandibular volume vs the height of the ramus (P < .05) and the length of the mandibular body (P < .05). An inverse correlation was found between the asymmetry of the ramus height vs the condylar height (P < .05), mandibular body length (P < .05) and gonial angle (P < .05). Mandibular asymmetries in children did occur (9.8% of the included mandibles presented with a relevant overall asymmetry of ≥3%) and were unrelated to age. The different segments of the mandible seem to compensate for each other, in order to maintain a functional equilibrium.

Dentofacial asymmetry: non-surgical orthodontic treatment using extra-alveolar miniscrews

Asymmetric malocclusions have been always a challenge to orthodontists, with different dental, skeletal or dentoskeletal factors being probable causes for the condition. It is key to distinguish between dental and skeletal asymmetry before determining a predictable force system for corrective treatment. The use of mini-implants (MIs) to address anchorage needs in modern orthodontic practice has become an important tool for orthodontists. They have been widely used for anchorage reinforcement purposes and placed in the dentoalveolar region, especially between tooth roots (inter-radicular miniscrews). However, placement sites other than root areas allow more versatility of orthodontic movement since tooth roots do not interfere in tooth displacement, such as the extra-alveolar miniscrews.Objective The objective of the present paper is to present biomechanical concepts in which extra-alveolar mini-implants are placed in the infrazygomatic crest (IZC) and buccal shelf (BS) areas for correction of dento-facial asymmetries allowing predictable outcomes to be achieved with minimal need for patient's compliance and minor mechanic side effects.

Asymmetric dental-alveolar transversal corrections with skeletal anchorage

Transversal asymmetries of the dental arches are common orthodontic problems. Significant asymmetries needed a surgical approach for their correction before the introduction of skeletal anchorage. This paper presents two different approaches to correct dental transversal asymmetries, using skeletal anchorage both directly and indirectly. The direct use of skeletal anchorage requires careful planning of the desired dental movement and the estimation of the line of action of the needed force to achieve it. This information can be used to orientate the orthodontist in the screw placement, since it should be inserted, if possible, along the line of action of this force. In this way, it is possible to design appliances that do not deliver to the screw moments, which can compromise their stability. In the direct approach, the screw can be placed in the palatal vault or between the dental roots. The indirect use of skeletal anchorage implies the connection of the screw with one or some of the teeth which are required to maintain their position. Since the connecting wire should be rather short, it is recommendable to place the screw in the interradicular bone, rather than in the palate. This approach can be used with both fixed appliances, and with aligners. Four clinical cases illustrate these modalities of asymmetric expansion or contraction.

Does positional plagiocephaly affect the need for orthodontic treatment, and the mandibular and occlusal symmetry?

Positional plagiocephaly (PP) is characterized by an asymmetrical flatness of the posterior part of the skull which may involve the frontal part of the skull and the face. The aim is to assess whether children and adolescents with PP have more occlusal and skeletal asymmetries and whether the need for orthodontic treatment is greater than in the healthy population. A comparative cross-sectional epidemiological study was carried out. One hundred children and adolescents were included: 50 in the PP group and 50 in the control group. The need for orthodontic treatment was assessed by the Index of Orthodontic Treatment Need (IOTN). The mandibular and dental asymmetries were measured on lateral cephalometry by two indexes: index of mandibular asymmetry (IMA) and index of dental asymmetry (IDA) respectively. Chiand Student independence tests were performed with a threshold of 5%. The tests are significant for IMA (p = 0.02) and IOTN (p = 0.000012). IDA is insignificant. Orthosurgical treatment of mandibular laterognathies by mandibular recentering sometimes creates mandibular asymmetry, while the shift is basal. We must be able to act early on the vault of the skull to hope to obtain a consecutive effect on the base and therefore on the position of the glenoid cavities. Management by manual therapy and early cranial orthosis could be estimated. The need for orthodontic treatment is significantly greater in PP. Unlike mandibular asymmetry, dental asymmetry is not significantly greater than in the control group, testifying to the adaptive capacities of the organism.

A 3D mirroring and colormap asymmetry study of Class II subdivision patients.

Patients with Class II subdivision malocclusion present skeletal and dental asymmetries. The purpose of this study is to assess those asymmetries by 3D mirroring and colormap quantification. This study analyzed 50 initial CBCTs divided into two groups: Class I (control group) and Class II subdivision (study group) malocclusion patients. CBCTs were oriented and full skull was segmented generating a 3D model. The right side of the 3D models was mirrored, using a midsagittal plane as reference, resulting in a perfectly symmetric skull based on two right sides. Original and mirrored models were superimposed on the unchanged right half, and differences were quantified using a colormap. Eight regions of interest were assessed: gonion, mandibular front, maxillary front, zygomatic process, maxillary and mandibular canine and molar areas. Statistically significant differences using the Mann-Whitney test were found in six of the eight evaluated areas when comparing the control to the study group. The maxillary skeletal areas did not show any difference between the groups. Patients with Class II subdivision malocclusion show true skeletal and dental asymmetries when comparing right and left sides. The maxilla showed no significant skeletal asymmetry, but the maxillary teeth were positioned more mesially on the Class II side. The maxillary canine on the Class II side was also more bucally positioned. The mandible showed significant asymmetries with both skeletal and dental areas in the Class II side more distally and bucally positioned.

Symmetry and Aesthetics in Dentistry

Animal bodies in general and faces in particular show mirror symmetry with respect to the median-sagittal plane, with exceptions rarely occurring. Bilateral symmetry to the median sagittal plane of the body also evolved very early. From an evolutionary point of view, it should therefore have fundamental advantages, e.g., more effective locomotion and chewing abilities. On the other hand, the recognition of bilaterally symmetric patterns is an important module in our visual perception. In particular, the recognition of faces with different spatial orientations and their identification is strongly related to the recognition of bilateral symmetry. Maxillofacial surgery and Dentistry affect effective masticatory function and perceived symmetry of the lower third of the face. Both disciplines have the ability to eliminate or mitigate asymmetries with respect to form and function. In our review, we will demonstrate symmetric structures from single teeth to the whole face. We will further describe different approaches to quantify cranial, facial and dental asymmetries by using either landmarks or 3D surface models. Severe facial asymmetries are usually caused by malformations such as hemifacial hyperplasia, injury or other diseases such as Noma or head and neck cancer. This could be an important sociobiological reason for a correlation between asymmetry and perceived disfigurement. The aim of our review is to show how facial symmetry and attractiveness are related and in what way dental and facial structures and the symmetry of their shape and color influence aesthetic perception. We will further demonstrate how modern technology can be used to improve symmetry in facial prostheses and maxillofacial surgery.

Class III malocclusion: a challenging treatment using miniscrews for extra anchorage

Abstract Aims This article presents the nonsurgical orthodontic treatment of a skeletal Class III malocclusion of an adult patient. Methods Because the patient refused an orthognathic surgical procedure, the mandibular first premolars were extracted and orthodontic camouflage using miniscrew anchorage was used to correct dental asymmetries and the occlusal relationship. Results The treatment strategy was successful and provided an acceptable aesthetic functional occlusion. Conclusion When appropriately indicated, the orthodontic camouflage of a class III malocclusion can avoid orthognathic surgery and, through the use of mini-implants as skeletal anchorage, enhance the results.

Mandible Biomechanics and Continuously Erupting Teeth: A New Defect Model for Studying Load-Bearing Biomaterials.

Animals with elodont dentition and unfused mandible symphyses are hypothesized to have symmetric incisor morphology. Since these animals maintain their teeth by gnawing, they may provide physiologic feedback on mechanical function when unilateral mandible defects are created that manifest as ipsilateral changes in tooth structure. This defect model would potentially generate important information on the functional/mechanical properties of implants. Rats’ and rabbits’ mandibles and teeth are analyzed with µCT at baseline and post-intervention (n = 8 for each). Baseline incisors were compared. In a unilateral mandible pilot study, defects—ranging from critical size defect to complete ramus osteotomies—were created to assess effect on dentition (rats, n = 7; rabbits, n = 6). Within 90% confidence intervals, animals showed no baseline left/right differences in their incisors. There are apparent dental changes associated with unilateral defect type and location. Thus, at baseline, animals exhibit statistically significant incisor symmetry and there is an apparent relationship between mandible defect and incisor growth. The baseline symmetry proven here sets the stage to study the degree to which hemi-mandible destabilizing procedures result in measurable & reproducible disruption of dental asymmetry. In a validated model, an implant designed to function under load that prevents incisor asymmetry would provide supporting evidence that the implant has clinically useful load-bearing function.