Dental Midline Discrepancy Research Articles

Dental-Facial Midline: An Esthetic Based Classification

Background: The facial midline and dental midline play an important role in facial esthetics, cosmetic dentistry, facial plastic surgery, and anthropologic studies. Objective: This study studied the dental-facial midline in Nepalese subjects and to classify the midline. Methods: The study was conducted in 150 Nepalese subjects, mostly consisting of University students (80 males and 70 females). After obtaining ethical approval, facial and dental midlines were analyzed using a scale. Results: It showed 26 (18%) study subjects showed the coincidence of the facial midline with the maxillary and mandibular dental midlines. It showed that only 44 (30%) subjects showed the coincidence of facial midline with only maxillary dental midline, and 26 (17%) subjects showed the facial midline coincidence with only mandibular dental midline. The dental midline discrepancy was more prevalent in the maxillary arch and more prevalent on the right side. Midline discrepancy is seen more in males compared to females. The majority of the deviation showed 1 mm, followed by 2 mm, and 3 mm. Conclusion: The coincidence of the facial midline with both the maxillary and mandibular dental midlines is uncommon. Midline discrepancy is seen more in males compared to females. The majority of the subjects show a mild discrepancy of 1 mm. The midline discrepancy was more seen on the right side and in the maxillary arch.

A postero-anterior cephalometric evaluation of different rapid maxillary expansion appliances

The purpose of the study was to evaluate dental and skeletal changes induced by tooth-bone-borne, tooth-tissue-borne, and tooth-borne rapid maxillary expansion (RME) appliances using postero-anterior (PA) cephalometric radiographs. A total of 54 patients' (25 boys, 29 girls) PA cephalometric radiographs who had bilateral posterior crossbite and RME treatment were included and divided into three groups according to the type of appliance used during treatment: tooth-bone-borne RME appliance (hybrid Hyrax) (7 boys, 11 girls, mean age 13.28 ± 1.20 years), tooth-tissue-borne RME appliance (TTB) (8 boys, 10 girls, mean age 13.08 ± 1.06 years) and tooth-borne RME appliance (Hyrax) (10 boys, 8 girls, mean age 12.05 ± 1.35 years). Pretreatment (T0) and posttreatment (T1) PA cephalometric radiographs were analyzed with Dolphin software v. 11.7 (Chatsworth, CA). The comparisons of the groups were performed with Two-way analysis of variance. P < 0.05 was considered statistically significant. Significant and equal increase of right molar relationship and upper intermolar molar widths occurred in all groups. Dental midline discrepancy showed significant increase in only hybrid Hyrax group between T0 and T1. Significant increases were reported for lateronasal width in hybrid Hyrax and tooth-tissue-borne groups (P < 0.05). Both skeletal and dental changes were observed after RME in all groups. However, the greatest skeletal changes were seen in hybrid Hyrax and tooth-tissue-borne groups.

Dental-Facial Midline: An Esthetic Based Classification

Background: The facial midline and dental midline play an important role in facial esthetics, cosmetic dentistry, facial plastic surgery, and anthropologic studies. Objective: This study studied the dental-facial midline in Nepalese subjects and to classify the midline. Methods: The study was conducted in 150 Nepalese subjects, mostly consisting of University students (80 males and 70 females). After obtaining ethical approval, facial and dental midlines were analyzed using a scale. Results: It showed 26 (18%) study subjects showed the coincidence of the facial midline with the maxillary and mandibular dental midlines. It showed that only 44 (30%) subjects showed the coincidence of facial midline with only maxillary dental midline, and 26 (17%) subjects showed the facial midline coincidence with only mandibular dental midline. The dental midline discrepancy was more prevalent in the maxillary arch and more prevalent on the right side. Midline discrepancy is seen more in males compared to females. The majority of the deviation showed 1 mm, followed by 2 mm, and 3 mm. Conclusion: The coincidence of the facial midline with both the maxillary and mandibular dental midlines is uncommon. Midline discrepancy is seen more in males compared to females. The majority of the subjects show a mild discrepancy of 1 mm. The midline discrepancy was more seen on the right side and in the maxillary arch.

New protocol for in-house management of computer assisted orthognathic surgery

The aim of this study was to evaluate retrospectively the accuracy of a protocol for completely in-house, computer-assisted, orthognathic surgery, generating resin printed intermediate surgical guides. A retrospective, observational study was made on a cohort of 15 patients treated consecutively from September 2017 to May 2019, who underwent bimaxillary orthognathic surgery planned with the same 3-dimensional program and whose surgical intermediate splints were obtained with the same all-in-house protocol. Virtual planned surgical movements were compared with the real surgical outcome. The differences were not significant for eight of the 12 variables considered. The p values, calculated with the Wilcoxon signed rank test, were evenly distributed and ranged from p=0.001 to p=0.820. Significant differences were reported in four measurements: angle between sella-nasion plane and a line connecting the incisal edge and the apex of the root of the most prominent incisor (U1-SN) (p=0.001), angle between Frankfort plane and a line connecting the incisal edge and the root apex of the most prominent upper incisor (p=0.008), dental midline discrepancies (p=0.006), and occlusal plane tilt (U1-FH) (p=0.001), basically due to intraoperative settings. The 3-dimensional resin printed surgical guides were shown to be a reliable alternative to the commercial ones and showed high rate of accuracy for most of the variables assessed. Four out of 12 of these showed significant errors, but two of them were only minimal discrepancies with no clinical implications.

Evaluation of Facial and Dental Midline Discrepancies in Nepalese Population

Introduction: The facial midline is defined by the landmark such as the nose, philtrum, and chin aligned in a straight line. It should be in the center of the face and should coincide with the dental midline. But clinically it is often observed that some discrepancies exist between facial and dental midlines. Thus the aim of this study was to evaluate the facial and dental midline discrepancies.&#x0D; Methods: A total of 300 subjects, 150 male and 150 female from People’s Dental College and Hospital were selected. Full facial view standardized photograph with a posed smile with teeth in occlusion was taken with Canon 400D digital SLR. For standardized measurement vertical metallic scale with millimeter, markings were placed on the right side of the patient in all cases. The software program Digimizer image analysis (version 4.6.1) was used to determine the facial and maxillary dental midline.&#x0D; Result: This study showed 6.66% of male and 12% of female had perfectly coinciding F1 facial midline (perpendicular from the midpoint of inner canthus distance), F2 facial midline (line joining the midpoint of inner canthus and the midpoint of the base of the nose) and maxillary midline. 26% of males and 28% of females had less than 1mm of the discrepancy of F1 midline to maxillary midline whereas 41% of males and 38% of females had less than 1 mm of a discrepancy between F2 facial midline and maxillary midline. The study also showed that 24% of males and 24.66% of females had none coincidence of any of the midlines with one another.&#x0D; Conclusion: Most of the Nepalese have noncoinciding facial and dental midline but females have more coinciding midlines in comparison to males. The shifted facial midlines are more towards the left side in relation to maxillary dental midline.

Quantification of maxillary dental midline deviation in 2D photographs: Methodology trial

Discrepancy of the upper dental midline to the facial midline plays an important role in smile aesthetic assessment. This study presents different reference points to quantify the deviation of upper dental midline to the facial midline in 2D frontal photographs. The aim was to find the most accurate, precise, and practical reference points to measure dental midline discrepancy in 2D photographs. A modified headset with a protractor was developed in order to achieve photographs in nine standardised head positions. Six reference points were used to detect the facial midline in the 2D photographs (eyebrows "EB", inner-canthus of the eyes "ICE", alae of the nose "AN", columella "C", nasolabial folds "NLF", and the philtrum "PH"). The deviation of the maxillary dental midline from the facial midline was measured and compared with clinical measurements. Standard deviations (SD), Root Mean Square Error (RMSE), Method of Moments' Estimator (MME), 2-way repeated measures ANOVA, and multi-level linear model were used to estimate the true errors. The different reference points responded significantly differently to changes in head position and all showed measurement errors, which increased with greater head rotation. Alae of the nose showed the least measurement error and the greatest precision in all head positions. The alae of the nose are the recommended reference points to identify the facial midline in order to quantify dental midline deviation from frontal photographs.

Interdisciplinary management of a patient with advanced dental needs

Abstract The present case report outlines the interdisciplinary management of an adult patient presenting with advanced generalised periodontal attachment loss, an upper dental midline discrepancy following the previous extraction of the upper left central incisor, and significant lower arch crowding. The endodontic and periodontal condition was stabilised prior to the commencement of fixed appliance orthodontic treatment and subsequent prosthetic replacement of the upper left central incisor. Interdisciplinary management provided a functional occlusion and stability of the periodontal condition along with pleasing facial and smile aesthetics.

Orthodontics problems in pediatric and growing subjects

Results The presence of posterior crossbite was significantly greater in growing subjects with oral breathing thus confirming the influence of these factors on skeletal development with constriction of the whole palate. Unilateral posterior crossbite is often associated with mandibular lateral displacement that is clinically characterized by deviation of the chin, facial asymmetry, dental midline discrepancy, and high prevalence of internal derangement of the temporomandibular joint. Children with anterior openbite presented with a greater prevalence rate of sucking habits. Hyperdivergency is a risk factors for negative overbite in mixed dentition subjects. The test group had significantly smaller maxillary intermolar and intercanine widths and greater posterior transverse discrepancy. Class III malocclusion is a complex clinical entity that entail the contraction of the maxilla and a narrowing of the base of the nose in addition to an increased mandibular total length. Conclusions Treatment of orthodontic problems that do not improve with age may be started earlier to avoid worsening of the condition in permanent dentition. The objective of any treatment in pediatric subjects before eruption of all permanent teeth are to correct the skeletal discrepancy between the jaws and improve function and facial esthetics by allowing them to develop normally, to create an ideal overbite and overjet relationship, to align the anterior permanent teeth and reduce the chance of trauma to these teeth, to improve the width of the dental arches and to reduce the risk for extraction of permanent teeth and for surgery in severe cases. Morphologic and functional characteristics of unilateral posterior crossbite with mandibular lateral deviation should be clarified to correct and prevent this malocclusion. Children with mouth-breathing pattern and sucking habits showed a significant constriction of the maxillary arch and an increased palatal height when compared with control group. Early treatment of Class III malocclusion is able to produce significant and favorable longterm skeletal shape changes characterized by an anterior morphogenetic rotation of the mandible.

Overjet, overbite and dental midline shift as predictors of tooth size discrepancy in a Bangladeshi population and a graphical overview of global tooth size ratios

Objectives. This study aimed to measure and compare tooth size ratios in a Bangladeshi population across the following groups: those with normal occlusion, crowding or spacing; those with normal, increased or decreased overjet; those with normal, increased or decreased overbite; those with or without dental mid-line discrepancy; and those with or without lip competence. It also presents a graphical overview of the anterior and overall ratios from the study and using available global data. Materials and methods. This study was performed on dental casts of 260 Bangladeshi individuals, comprising 114 males and 146 females (age range, 18–24 years, mean age = 20). The Bolton anterior ratio and overall ratio were determined for the following groups: those with normal occlusion, crowding or spacing; those with normal, increased or decreased overjet; those with normal, increased or decreased overbite; those with or without dental mid-line discrepancy; and those with or without lip competence. Results. There were statistically significant differences in the anterior tooth size ratios between those with or without dental mid-line discrepancy, with a mean value of 78.83% and 80.05%, respectively. Statistically significant differences were also found in overall tooth size ratios between those with normal, increased or decreased overjet and also between those with normal, increased or decreased overbite. Graphical presentations of anterior and overall ratios from the present study and using global data showed variations between populations. Conclusion. In the Bangladeshi population, increased tooth size ratios in subjects with dental mid-line discrepancy (anterior ratio) and also in those with decreased overjet or decreased overbite (overall ratio) may be predictors of tooth size discrepancies. The graphical overview also suggests that different international ethnic groups display unique Bolton ratios.

Midline correction by asymmetric reciprocal torque: a pilot study

Can we correct dental midline discrepancies by systematic torque bends on all canines and premolars without extraction and mesiodistal tooth movement? Eight orthodontic patients (4 males, 4 emales, mean age 31 years) presented a dental midline discrepancy of 2-4 mm, moderate deviation of the chin, no skeletal asymmetry, and a horizontal orientation of the occlusal plane in the frontal aspect. On the side where the mandible was shifted medially, asymmetric torque bends moved the antagonist canine and both premolar crowns buccally, while palatal crown torque was used on the maxillary canine and premolars on the other side. Lingual crown torque corrected the medially shifted canine and premolars in the mandibular dental arch, and buccal crown torque the laterally shifted lower canine and premolars. On average, torque effects altered the canine guidance by 6.5 ± 4.7°, the first premolar guidance by 7 ± 4.1°, and the second premolar guidance by 6.3 ± 3.7°. Correction of the dental midline shift averaged 1.6 ± 0.8 mm after the torque, and eliminated the midline discrepancy completely (n = 2) or partly (n = 6). In this pilot study, asymmetric reciprocal torque represented a treatment option for midline corrections of approximately 2-4 mm and improvement in the chin position without mesiodistal tooth movement or extraction.

Orthodontic-surgical treatment of Class III malocclusion with extraction of an impacted canine and multi-segmented maxillary surgery

Establishment of a treatment plan is based on efficacy and easy application by the clinician, and acceptance by the patient. Treatment of adult patients with Class III malocclusion might require orthognathic surgery, especially when the deformity is severe, with a significant impact on facial esthetics. Impacted teeth can remarkably influence treatment planning, which should be precise and concise to allow a reasonably short treatment time with low biologic cost. We report here the case of a 20-year-old man who had a skeletal Class III malocclusion and impaction of the maxillary right canine, leading to remarkable deviation of the maxillary midline; this was his chief complaint. Because of the severely deviated position of the impacted canine, treatment included extraction of the maxillary right canine and left first premolar for midline correction followed by leveling, alignment, correction of compensatory tooth positioning, and orthognathic surgery to correct the skeletal Class III malocclusion because of the severe maxillary deficiency. This treatment approach allowed correction of the maxillary dental midline discrepancy to the midsagittal plane and establishment of good occlusion and optimal esthetics.

Morphologic, functional, and occlusal characterization of mandibular lateral displacement malocclusion

Mandibular lateral displacement (MLD) is clinically characterized by deviation of the chin, facial asymmetry, dental midline discrepancy, crossbite in the posterior region, and high prevalence of internal derangement of the temporomandibular joint. Morphologic and functional characteristics of MLD should be clarified to correct and prevent this malocclusion. We examined the morphologic features, occlusal scheme, and functional behavior of MLD in 116 patients. Facial morphology was examined with posteroanterior cephalograms, occlusion guidance on the articulator after face-bow transfer, and condylar movement with the condylograph. The superiorly inclined occlusal plane was associated with mandibular deviation in the same direction. The posterior occlusal plane on the shifted side was significantly steeper than that on the nonshifted side. Functional analysis of condylar movement showed a close relationship between the direction of MLD and the direction of condylar lateral shift during opening and closing, and protrusion and retrusion. The occlusal guidance inclination in the buccal segment of the nonshifted side was steeper than that in the shifted side. The results suggested that reduced vertical height of the dentition on 1 side induced mandibular lateral adaptation with contralateral condylar shift (asymmetry); this leads to condylar lateral shift during functional movement.

Editor's Comment and Q&A: Morphologic, functional, and occlusal characterization of mandibular lateral displacement malocclusion

Introduction Mandibular lateral displacement (MLD) is clinically characterized by deviation of the chin, facial asymmetry, dental midline discrepancy, crossbite in the posterior region, and high prevalence of internal derangement of the temporomandibular joint. Morphologic and functional characteristics of MLD should be clarified to correct and prevent this malocclusion. Methods We examined the morphologic features, occlusal scheme, and functional behavior of MLD in 116 patients. Facial morphology was examined with posteroanterior cephalograms, occlusion guidance on the articulator after face-bow transfer, and condylar movement with the condylograph. Results The superiorly inclined occlusal plane was associated with mandibular deviation in the same direction. The posterior occlusal plane on the shifted side was significantly steeper than that on the nonshifted side. Functional analysis of condylar movement showed a close relationship between the direction of MLD and the direction of condylar lateral shift during opening and closing, and protrusion and retrusion. The occlusal guidance inclination in the buccal segment of the nonshifted side was steeper than that in the shifted side. Conclusions The results suggested that reduced vertical height of the dentition on 1 side induced mandibular lateral adaptation with contralateral condylar shift (asymmetry); this leads to condylar lateral shift during functional movement.

Are ratings of dentofacial attractiveness influenced by dentofacial midline discrepancies?

Abstract Aims To assess the attractiveness of dentofacial midline discrepancies during smiling, and to determine if the ratings were influenced by the gender of the judges. Methods Twenty non-dental undergraduate students (10 males, mean age: 33.5 years; 10 females, mean age: 31.2 years) and 20 orthodontists (10 males, mean age: 36.6 years; 10 females, mean age: 34.3 years) assessed frontal photographs of the same smiling adult female with coincident midlines, and images of the same person with the upper dental midline shifted 2 mm and 4 mm to the right and left of the facial midline. The judges scored the attractiveness of the smile using 5-point scale. Results Both the students and the orthodontists considered that the images were less attractive as the dentofacial midline discrepancy increased. More orthodontists than undergraduate students, and more female orthodontists than male orthodontists, considered a 4 mm discrepancy between the dental and facial midlines as unattractive. Conclusion Dental to facial midline discrepancies reduce dentofacial attractiveness. Discrepancies of 2 mm or more are likely to be noticed by both orthodontists and non-dental university students. Orthodontic treatment objectives should include correction of the dental midline discrepancies to within 2 mm of the facial midline.

Malocclusion as a risk factor in the etiology of headaches in children and adolescents

The purpose of this study was to determine the importance of occlusal factors in recurrent headaches in children and adolescents without other signs or symptoms of temporomandibular disorders or related craniomandibular disorders. A sample of 50 children and adolescents, ages 8 to 16, who reported headaches was obtained from the University at Buffalo Orthodontic Clinic records; a control group of 50 children and adolescents, matched for age and sex, was also obtained. Plaster models, made during the routine collection of orthodontic records, were used to obtain the following occlusal trait measurements: Angle classification, overjet, anterior and posterior crossbite, scissors-bite, overbite, open bite, dental midline discrepancy, crowding, spacing, and dental development stage. Overbite, overjet, and posterior crossbite showed statistically significant associations (chi-square) with increased risk for headaches. Logistic regression analysis demonstrated that overjet was a significant factor only because of its correlation with overbite and posterior crossbite. Overjet was not significant after adjusting for the other 2 variables, whereas overbite and posterior crossbite were associated with significantly increased risk (>3:1) of headache. The combination of 2 or more of these 3 occlusal factors increased the risk of headache even more (8.5:1). Posterior crossbite and overbite > or =5 mm were associated with significantly increased risk of headache in children and adolescents.

Mandibular Incisor Extraction Treatment of a Class I Malocclusion with Bolton Discrepancy: A Case Report

MANY APPROACHES FOR CROWDED MANDIBULAR ANTERIOR TEETH ARE CURRENTLY EMPLOYED: distal movement of posterior teeth, lateral movement of canines, labial movement of incisors, interproximal enamel reduction, removal of premolars, removal of one or two incisors, and various combinations of the above. Selecting the best treatment is often difficult, and all guidelines do not apply to every case. Treatment by extraction of one single mandibular incisor is not popular in the orthodontic profession despite the apparent advantages of the extraction in the region of crowding. A case report is presented one mandibular incisor extraction treatment of a 16 year-old female with a Class I malocclusion that shows a significant mandibular arch length deficiency and mandibular tooth-size excess. In this case, the degree of mandibular anterior dental crowding, existing mandibular tooth-size excess, and the dental midline discrepancy were indicated the extraction of one mandibular incisor.

Quantification of the relative risk of multiple occlusal variables for muscle disorders of the stomatognathic system

Statement of problem There is no consensus on the association between occlusion and temporomandibular disorders (TMD). Purpose The purpose of this study was to quantify the relative risk of multiple occlusal variables for muscle disorders of the stomatognathic system. Material and methods Eight occlusal features: retruded contact position (RCP) to maximum intercuspation (MI) slide length, vertical overlap, horizontal overlap, unilateral posterior reverse articulation, anterior open occlusal relationship, incisor dental midline discrepancy, mediotrusive interferences, and laterotrusive interferences, were clinically assessed by the same trained operator. The sample consisted of 81 women with a Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) axis I diagnosis of muscle disorder, for example myofascial pain, with or without limited opening, and 48 healthy women (control group). A stepwise multiple logistic regression was used to identify the significant associations between occlusal features and disease. Results A slide from the retruded contact position to maximum intercuspation ≥2 mm and mediotrusive interferences were the only 2 occlusal features significantly associated with the presence of myofascial pain according to the RDC/TMD criterion symptoms. The odds ratio for myofascial pain was 2.57 for a slide from RCP to MI ≥2 mm and 2.45 for mediotrusive interferences. The percentage of the total log likelihood for myofascial pain explained by the significant occlusal factors amounted to 10.8% (Nagelkerke's R 2 = 0.108). The multifactorial model, including the 2 significant occlusal factors, showed an acuracy to predict disease of 66.7% (sensitivity 71.6%; specificity 58.3%). Conclusion Occlusal features showed a low predictive value to detect muscle disorders of the stomatognathic system. Multifactorial complex pathologies, such as TMD, should be studied using multivariate statistical analyses, as univariate models may overestimate some resulting associations.

A multiple logistic regression analysis of the risk and relative odds of temporomandibular disorders as a function of common occlusal features.

A multiple logistic regression analysis was used to compute the odds ratios for 11 common occlusal features for asymptomatic controls (n = 147) vs. five temporomandibular disorder groups: Disc Displacement with Reduction (n = 81), Disc Displacement without Reduction (n = 48), Osteoarthrosis with Disc Displacement History (n = 75), Primary Osteoarthrosis (n = 85), and Myalgia Only (n = 124). Features that did not contribute included: retruded contact position (RCP) to intercuspal position (ICP) occlusal slides < or = 2 mm, slide asymmetry, unilateral RCP contacts, deep overbite, minimal overjet, dental midline discrepancies, < or = 4 missing teeth, and maxillo-mandibular first molar relationship or cross-arch asymmetry. Groupings of a minimum of two to at most five occlusal variables contributed to the TMD patient groups. Significant increases in risk occurred selectively with anterior open bite (p < 0.01), unilateral maxillary lingual crossbite (p < 0.05 to p < 0.01), overjets > 6-7 mm (p < 0.05 to p < 0.01), > or > 5-6 missing posterior teeth (p < 0.05 to p < 0.01), and RCP-ICP slides > 2 mm (p < 0.05 to p < 0.01). While the contribution of occlusion to the disease groups was not zero, most of the variation in each disease population was not explained by occlusal parameters. Thus, occlusion cannot be considered the unique or dominant factor in defining TMD populations. Certain features such as anterior open bite in osteoarthrosis patients were considered to be a consequence of rather than etiological factors for the disorder.

The midline: Diagnosis and treatment

The importance of coordinated midlines often is unappreciated as it relates to the treatment plan for the orthodontic case. All three of the patient's midlines--facial, maxillary, and mandibular--must be considered if ideal correction is to be achieved. Proper differential diagnosis of the cause will allow the practitioner to appropriately use either inter- or intraarch mechanics for the resolution of midline discrepancies. Midline correction should be undertaken from the initiation of treatment and once all midlines are coordinated they should be maintained as a guide for any further force systems used in completing the case. Functional, dental, and iatrogenic midline discrepancies are discussed pertaining to their diagnosis and treatment.

Relationship of mandibular condylar position to dental occlusion factors in an asymptomatic population

This article investigates the influence of occlusion on condylar position as seen on TMJ tomograms in a group of 44 young adults with no histories of orthodontic or occlusal therapy and no objective signs of masticatory dysfunction; the sample was screened from a population of 253 students. Nonconcentric condylar position at ICP was a feature of Class II malocclusion with significantly more anterior positions in Class II, Division 1 than in Class I. Condylar position was unrelated to the amount of sagittal RCP-ICP slide, although most slides were <0.5 mm. The frequency of lateral slides was low, but was mildly related to bilaterally asymmetric condylar positions. Position was unrelated to the degree of overbite, which ranged from 0 to 10 mm. Bilateral condylar position asymmetry was not related to the direction of dental midline discrepancy, which ranged from 0 to 2 mm. No open bites or mandibular overjets were seen in this asymptomatic normal sample.