Occlusal Cant Research Articles

Occlusal Cant: Etiology, Evaluation, and Management

ABSTRACT Occlusal cant is an important factor affecting smile esthetics.The dynamic display zone includes lateral, vertical, and anteroposterior aspects, as well as the cant of the occlusal plane. Smile design and mechanotherapy must take into account an esthetic plane of occlusion. The purpose of this review is to describe occlusal cant, examine its diagnosis, and explain the treatment alternatives for this condition. (Turkish J Orthod. 2015;27:174–180)

Post-operative Stability After Bimaxillary Surgery in Patients with Facial Asymmetry: Comparison of Differences Among Different Original Skeletal Class Patterns.

When improving jaw deformity by two-jaw surgery, we are of the opinion from our clinical experience that a certain degree of undercorrection is occasionally beneficial from the perspective of stability. Functional deterioration is not always seen with undercorrection. We conducted this retrospective study to assess post-operative stability in patients with facial asymmetry, with the aim of both clarifying differences between the original three skeletal class patterns, and confirming the efficacy of surgery performed on the basis of our concept. All patients received optimal orthognathic treatment before and after surgery. Surgery was performed by our concept that undercorrection is not always bad. Nineteen patients were enrolled, and separated into three skeletal classes according to the ANB angle, because of the difference of the treatment modalities between them. Evaluations were performed by cephalometric measurements taken at least two-year post-operatively. Transverse occlusal cant, chin deviation, point A, point B, overjet and overbite were assessed. In all patients, transverse occlusal cant improved to <4°, which has been reported as the threshold for visual recognition of facial symmetry. Chin deviation was also improved to the degree at which soft tissue can sufficiently mask the asymmetry. The changes remained stable throughout follow-up and satisfaction was obtained from all patients. Irrespective of original skeletal class patterns, post-operative stability of patients with facial asymmetry was achieved. Undercorrection is thus by no means problematic from the clinical perspective of stability and our concept of approach appears valid.

The unique contribution of elements of smile aesthetics to psychosocial well-being.

Pleasant smile aesthetics is an important contributory factor to psychosocial well-being. The aim of this study was to determine the psychosocial influence of smile aesthetics. The study was cross-sectional on a convenient sample that included patients, pupils, students and faculty staff. A total of 155 subjects (36% male) aged 12-39 (mean age 21, interquartile range 19-23) were included. Occlusal characteristics were recorded by the Index of Complexity, Outcome and Need, and smiling frontal view photographs were obtained. Fourteen variables were measured using photogrammetric analysis: smile width, visibility of buccal corridors, maximum teeth exposure, total gingival display, lip thickness, degree of occlusal cant and deviation from golden proportion of the teeth in maxillary intercanine sector. Psychometric instruments included the Psychosocial Impact of Dental Aesthetics Questionnaire and the Rosenberg Self-Esteem Scale. Statistical analysis comprised multiple linear regressions. Malocclusion severity is the most important predictor of psychosocial influence of smile aesthetics and self-esteem, the unique contribution of which accounts for a total of 4-27% of variability. Female gender is associated with higher psychological influence of dental aesthetics while male gender and older age with self-esteem. Malocclusions have higher psychosocial impact than parameters of mini- and micro-aesthetics of smile related to visibility of buccal corridors, amount of teeth exposure, gingival display, lip thickness, presence of occlusal cant and deviation from golden proportion of the teeth. It appears that people are not as focused on details of their smile as they are on distinctive malposition of teeth.

Cephalometric outcomes of orthognathic surgery in hemifacial microsomia.

Hemifacial microsomia is a hypoplastic disorder of the first and second branchial arches that significantly impacts on the development of the jaws, leading to malocclusion and facial asymmetry. There is little in the literature regarding the application of orthodontic/orthognathic approaches to the correction of these deformities and the stability of the surgical results. To address this, a retrospective chart review of 10 patients with complete orthodontic records and greater than 1 year of follow-up was performed. Posteroanterior cephalograms were assessed by modified Grummons analysis to determine mandibular offset (deviation of the chin point from the skeletal midline) and occlusal cant. These measurements were performed at 3 time points (T1: preoperative, T2: immediate postoperative, T3: follow-up) to elucidate the surgical movement (T2-T1), the postoperative relapse (T3-T2), and the net gain movement (T3-T1). Maxillary movements were quantified, and the occlusal cant was expressed as a ratio between vertical heights of the maxilla at the first molar on each side. One sample t test demonstrated statistically significant surgical movement and net gain. Relapse was statistically insignificant. Repeated-measures analysis of variance demonstrated similar results for chin point position relative to the putative midline. Our results suggest that a combined orthodontic/orthognathic approach at skeletal maturity delivers improved occlusal outcomes in the long term as assessed by chin point deviation and occlusal cant, but secondary surgery rates are higher than those for orthognathic surgery in other patient groups. We advocate limiting surgery to skeletal maturity whenever possible to achieve stable long-term results while limiting morbidity and number of procedures.

Surgical Treatment of Hemimandibular Hyperplasia Leading to Unilateral Overdevelopment of the Face

Introduction:: Hemimandibular hyperplasia is a facial deformity which may develop in any age and includes a unilateral enlarged mandibular condylar head, deviation of mandible and chins, elongated condylar neck or ramus, and an occlusal cant with open bite. Different surgical treatments are proposed in the literature from simple low or high condylectomy to more complex procedures combining osteotomies in different sites of the mandible. Surgical procedure is defined by the clinical evaluation and scintigraphic diagnosis of activity or inactivity in the center of condylar growth. Case Presentation:: This case report describes a 30-year-old female patient with left hemimandibular hyperplasia with activity of condylar growth, that was successfully treated with low condylectomy, asymmetric lefort I osteotomy and inferior border ostectomy on the affected side, and associated with a unilateral sagittal split ramus osteotomy on the contra-lateral side. Discussion:: The innovation on nerve dissection by removing the overlying buccal bone and performing inferior ostectomy under direct visualization of the nerve, proved to be a safe technique with a low risk of nerve damage.

Surgical treatment planning for the two subtypes of mandibular asymmetry.

In treatment planning for dentofacial asymmetry, as in other dentofacial deformities, the vertical and anterior-posterior position of the maxilla and the occlusal plane angulation should be determined from clinical and cephalometric evaluation1. The midfacial midline, upper and lower dental midlines and chin midline also need to be carefully evaluated, and the amount of occlusal canting and yawing is a key aspect of repositioning the maxilla. Generally, mandibular position is dictated by the maxilla, maxillary teeth and occlusal plane angulation. However, asymmetric maxillary arch, which can occur in the molar region despite careful presurgical orthodontic treatment, can lead to improper positioning of the mandible and residual asymmetry, especially in the mandibular angle and ramus area. I suggest herein that, in orthognathic surgery for asymmetric mandibles, the mandibular movement required to achieve an appropriate occlusal relationship to the maxilla can be classified into two types according to the subtype of mandibular asymmetry: rotational or translational. In surgical treatment for rotational mandibular asymmetry, when the mandibular midline is shifted laterally, the most posterior aspect of one distal segment is rotated medially and the other side is rotated laterally. This causes gaps between the fragments when performing mandibular osteotomy. Displacement of the condyles medially or laterally within the mandibular fossa can occur when the proximal and distal segments are not passively positioned to one another during the application of internal fixation devices2. Several techniques are available to minimize or eliminate condylar displacement and its sequelae2,3,4. In presurgical orthodontic treatment for translational mandibular asymmetry, transverse dental decompensation of the posterior as well as the anterior teeth in both arches is required for lateral translational movement of the mandible and successful restoration of facial symmetry5,6. However, I have found that presurgical transverse dental decompensation for asymmetric patients is frequently incomplete, especially in the maxillary molars. I recommend establishing increased overjet of the molar region in postsurgical occlusion or additional maxillary yawing to achieve favorable esthetic results in these cases6. Surgical treatment planning for asymmetric patients should consider asymmetry subtypes and the movement of the asymmetric mandible as well as other traditional parameters.

Changes in the lip-line in asymmetrical cases treated with isolated mandibular surgery

The aim of this study was to investigate changes in the lip-line in asymmetrical cases treated with mandibular osteotomy alone. Retrospective study. Hiroshima University Institute of Biomedical & Health Sciences, Hiroshima, Japan The subjects in this study consisted of 30 patients with an altered lip-line inclination who underwent isolated mandibular osteotomy (bilateral or unilateral sagittal split ramus osteotomy or intraoral vertical ramus osteotomy) as part of their surgical correction. Frontal cephalograms and facial photographs, taken at the first examination and after treatment, were used to measure changes in the inclination of the lip-line and cant of the occlusal plane, as well as the lateral deviations of hard and soft tissue Menton. Inclination of the lip-line after active treatment was significantly improved compared with that before treatment. Menton on the hard and soft tissues after active treatment also experienced a significant improvement compared with its position at first examination. One-jaw mandibular osteotomy is able to improve the inclination of the lip-line even in the presence of an occlusal cant. The inclination of the lip-line is corrected in association with sufficient lateral movements of Menton on the mandible.

Short- and Long-Term Evaluation of a Condylar Hyperplasia: A Case Report

ABSTRACT Objective: This case report presents the diagnosis and short- and long-term treatment results of an orthodontically and surgically treated patient with condylar hyperplasia. Materials and Methods: Condylar hyperplasia was diagnosed in an 18-year-old patient. In the clinical and radiologic examination, asymmetrical face, overdevelopment of the head and lengthening of the neck of the right condyle, deviation of the menton to the opposite side, temporomandibular joint pain, occlusal canting, slight open bite in the affected side, and an impacted upper right premolar were detected. Technetium-99 radioisotope scanning was made in 6-month intervals, and surgery was planned and performed. Changes were measured on the cephalograms taken at the beginning of orthodontic treatment, before and after surgery, at the end of fixed treatment, and in 4 years 6 months follow-up period. Results: Skeletal and dental Class I relationship was established and the profile improved. Slight increase of the vertical dimens...

Physical Findings Associated With Active Temporomandibular Joint Inflammation in Children With Juvenile Idiopathic Arthritis

To identify the physical findings associated with active temporomandibular joint (TMJ) inflammation (ie, synovitis) in children with juvenile idiopathic arthritis (JIA). This was a retrospective study of children with JIA evaluated at Boston Children's Hospital. The patients were included if they had a confirmed diagnosis of JIA and had undergone a TMJ magnetic resonance imaging (MRI) study with contrast. Medical records and imaging studies were reviewed to document the demographic, physical (ie, facial asymmetry, joint noises, maximal incisal opening, deviation on opening, occlusal cant), and MRI findings. The outcome variable was TMJ synovitis on the MRI study. Descriptive and bivariate statistics were computed. Multiple regression models were used to identify associations (P ≤ .05, significance). A total of 51 patients with JIA were evaluated during the study period. Of these, 43 patients (33 girls) with a mean age of 11.4 years met the inclusion criteria. MRI demonstrated TMJ synovitis in 27 patients. The age-adjusted limited maximal incisal opening (MIO) and deviation on opening were the only physical findings significantly associated with synovitis on MRI (P = .003 and P = .043, respectively). Using these parameters as predictors of synovitis, a limited MIO and deviation on opening had a high specificity (86% and 94%, respectively). Patients with a limited MIO were 6.7 times more likely to have synovitis than those with a normal MIO. All patients with a limited MIO and deviation on opening had TMJ synovitis on the MRI scan. The results of this study indicate that, in children with JIA, limited MIO and deviation on opening can be used to predict the presence of TMJ synovitis. Documentation of these parameters should be an essential part of the clinical examination and longitudinal follow-up of children with JIA.

Smile esthetics from odontology students' perspectives

To analyze the perception of smile esthetics and its alterations in dental degree students; to determine whether there are differences in that perception among students in different study years on those courses and between genders; and to determine if the circumstance of having received prior orthodontic treatment could influence that perception. Students (n = 192) in different study years of the dental degree course at the University of Valencia, Spain, analyzed two photographs of a patient in which, by means of computer software, midline diastema, upper and lower midlines, crown length of the maxillary right central incisor, occlusal cant, and "gummy" smile were altered. Students assessed the photographs on a scale from 1 to 10. Statistical analyses for assessing each group's level of perception were carried out. After checking the validity of the study, it was observed that the students' ability to detect alterations in smile esthetics did not improve over their degree courses, given that the differences do not present a linear development. There were no differences between genders and between those who had or had not undergone an orthodontic treatment. There are no statistically significant differences between the results of students in different study years or between genders. The circumstance of having undergone prior orthodontic treatment is not a determining factor in the ability to perceive such anomalies.

Comparison of Two-Dimensional and Three-Dimensional Images for Phenotypic Assessment of Craniofacial Microsomia

Background and Purpose : Three-dimensional surface imaging is used in many craniofacial centers. However, few data exist to indicate whether such systems justify their cost. Craniofacial microsomia is associated with wide phenotypic variability and can affect most facial features. The purpose of this study is to compare three-dimensional versus two-dimensional images for classification of facial features in individuals with craniofacial microsomia. Methods : We obtained a series of two-dimensional and three-dimensional images of 50 participants, aged 0-20 years, diagnosed with craniofacial microsomia, microtia, or Goldenhar syndrome. Three clinicians classified the craniofacial features on each image, and ratings were compared by calculating kappa statistics. We also evaluated image quality using a 5-point Likert scale. Results : Reliability estimates were high for most features using both two-dimensional and three-dimensional image data. Our three-dimensional protocol did not allow for scoring of facial animation, occlusal cant, or tongue anomalies. Image quality scores for the mandible and soft tissue assessment were higher for three-dimensional images. Raters preferred two-dimensional photographs for assessment of the ear, ear canal, and eyes. Conclusions : Both three-dimensional and two-dimensional images provide useful data for objective characterization of the craniofacial features affected in craniofacial microsomia. A series of two-dimensional images has relative advantages for assessment of some specific features, such as the ear, though three-dimensional images may have advantages for quantitative analysis and qualitative assessment of deformities of the jaw and soft tissue. These results should apply to any assessment of these features with or without a craniofacial microsomia diagnosis.

Frankfort horizontal plane is an appropriate three-dimensinal reference in the evaluation of clinical and skeletal cant

ObjectivesIn three-dimensional computed tomography (3D-CT), the cant is evaluated by measuring the distance between the reference plane (or line) and the tooth. The purpose of this study was to determine the horizontal skeletal reference plane that showed the greatest correlation with clinical evaluation.Materials and MethodsThe subjects were 15 patients who closed their eyes during the CT image taking process. The menton points of all patients deviated by more than 3 mm. In the first evaluation, clinical cant was measured. The distance from the inner canthus to the ipsilateral canine tip and the distance from the eyelid to the ipsilateral first molar were obtained. The distance between the left and right sides was also measured. In the second evaluation, skeletal cant was measured. Six reference planes and one line were used for the evaluation of occlusal cant: 1) FH plane R: Or.R - Or.L - Po.R; 2) FH plane L: Or.R - Or.L - Po.L; 3) F. Ovale plane R: Rt.F.Ovale - Lt.F.Ovale - Or.R; 4) F. Ovale plane L: Rt.F.Ovale - Lt.F.Ovale - Or.L; 5) FZS plane R: Rt.FZS - Lt.FZS - Po.R; 6) FZS plane R: Rt.FZS - Lt.FZS - Po.L, and; 7) FZS line: Rt.FZS - Lt.FZS.ResultsThe clinical and skeletal cants were compared using linear regression analysis. The FH plane R, FH plane L, and FZS line showed the highest correlation (P<0.05).ConclusionThe FH plane R and FH plane L are the most appropriate horizontal reference plane in evaluation of occlusal cant on 3D-CT.

The use of miniscrew as orthodontic anchorage in correction of maxillary protrusion with occlusal cant, spaced arch, and midline deviation without surgery

This report describes the use of the miniscrew as orthodontic anchorage in maxillary protrusion with a spaced arch and midline deviation in a 16-year-old female patient. In cases with midline deviation, a cant in the maxillary occlusal plane is often observed. Thus, the authors used the miniscrew to control the vertical dimension, thereby flattening the maxillary occlusal plane, and to close and retract the incisors to improve her convex profile. Effective incisor intrusion to correct the deep overbite was also observed. In addition, functional evaluation by a 6-degrees-of-freedom jaw movement recording system was performed. Significant improvement in the jaw movement was observed during maximum opening and lateral excursion during the retention phase. The authors suggest that miniscrews are effective in correcting midline deviation due to maxillary occlusal cant and intrusion and retraction of incisors, and may result in favorable functional movement of the jaw.

Do the smiles of the world's most influential individuals have common parameters?

The aim of this study was to determine - on the basis of the most recent yearly listings - whether there were any common measurable variables associated with the smiles of the world's most influential people. A total of 168 subjects were selected from the lists of Time magazine's 100 most influential people during the period 2006-2010. Smiling frontal view photographs were obtained. Thirty-six variables for each subject were traced and measured using photogrammetric analysis to obtain qualitative and quantitative proportions and measurements. Differences with respect to gender, occupation and year of listing were tested to 95% significance, using the Student's t-test and the Kruskal-Wallis test. The chi-squared test was used for qualitative variables. Irrespective of gender or occupation, the similar quantifiable characteristics of the smiles of the most influential subjects were the following: vertical upper lip proportion, smile width, incisor exposure, buccal corridor ratio, smile symmetry index and intra-dental proportions (P>0·05). Other qualitative standards were as follows: smile symmetry, the buccal corridors and smile arc, direction of occlusal cant and the degree of deviation between maxillary and facial midlines. Differences were found for gingival display and smile height parameters (P=0·001). The smiles of the world's most influential people revealed common standards, regardless of occupation or gender, which may play a decisive role in the expressions of influential faces.

Correction of Facial Asymmetry Resulting From Hemimandibular Hyperplasia

Hemimandibular hyperplasia is a facial deformity in which there is an increase in the condyle, neck of the condyle or ramus, and an occlusal cant. Different surgical treatments are proposed in the literature, from simple low or high condylectomy to more complex procedures combining osteotomies in different sites of the mandible. Surgical procedure is defined by the scintigraphic diagnosis of activity or inactivity in the center of condylar growth. The case report describes a 35-year-old female patient with hemimandibular hyperplasia on the left side with inactivity of condylar growth, successfully treated with bilateral sagittal split ramus osteotomy associated with a basilar osteotomy in form of "L" on the affected side. The surgical technique was easily executed, with an improvement in function, aesthetics, and patient satisfaction. Correction of facial asymmetry caused by excessive growth of the mandible using this basilar osteotomy in the form of "L" combined with bilateral sagittal split ramus osteotomy proved to be a relatively simple technique of easy execution with a low risk of nerve damage.

Ultrasonic vertical osteotomy of the distal segment for safe elimination of interference between the proximal and distal segments in bilateral sagittal split osteotomy for mandibular asymmetry

ilateral sagittal split osteotomy (BSSO) is commonly used n the correction of dentofacial deformities. However, in cases f facial asymmetry with a shift of the mandibular midline r occlusal cant, the condyle is displaced laterally by the ulling of the proximal segment medially when there is bony nterference between the proximal and distal segments after he osteotomy. When the gap between the proximal and disal segments is large, the proximal segment will clearly be symmetrical as a lateral bulge on the patient’s cheek, even f a large piece is removed. To overcome these problems, llis reported a vertical osteotomy of the distal segment ehind the terminal molar to passively align the segments f the sagittal ramus osteotomy.1 This procedure can also e used to improve the angle of the occlusal plane and cclusal stability when rotating the maxillomandibular comlex counterclockwise.2 When the inferior alveolar nerve IAN) is exposed, it is retracted laterally and the vertical steotomy made. However, the IAN is not always exposed ecause surgeons seek to minimise its exposure to prevent njury. As there is the potential for such injury during verical osteotomy of the distal segment when a conventional ur or saw is used, we have developed an ultrasonic vertial osteotomy of the distal segment to eliminate interference

Orthodontic and surgical treatment of a patient with hemifacial microsomia

This article describes the surgical and orthodontic treatment of a 12-year-old boy with a significant deformity and functional involvement caused by hemifacial microsomia. The left mandibular ramus and condyle were hypoplastic and abnormal in form and location. The lower third of the face was increased, with mandibular retrusion and significant facial asymmetry. He had difficulties in speaking and chewing and problems related to his facial appearance, which caused severe psychosocial disturbances. The patient received orthodontic treatment and temporomandibular joint reconstruction with a costochondral graft on the left side while he was still growing. Three-year follow-up records are presented.

Use of Intraoral Miniplates to Control Postoperative Occlusion After High Condylectomy for the Treatment of Condylar Hyperplasia

Mandibular condylar hyperplasia is a rare disorder, characterized by unilateral mandibular overgrowth with overeruption of the dentition on the affected side. Although the etiology is unclear, multiple surgical techniques have been described to correct the associated mandibular bone, occlusal, and soft tissue deformities. Often a condylectomy, to arrest mandibular growth, is combined with various orthognathic procedures to restore occlusion and facial harmony. Here we report our technique of isolated high condylectomy with simultaneous intraoral placement of maxillary and mandibular miniplates. Each plate has an intraoral extension that allows our orthodontists to develop vertical force vectors to intrude the maxillary and mandibular molar segments. Using this combined surgical and orthodontic technique, we were able to postoperatively control the occlusal cant, restore the dental midline, improve facial aesthetics, and resolve the patient's contralateral temporomandibular joint dysfunction without concomitant orthognathic surgery. As a result of our findings, we are currently using, and would recommend, this technique for patients requiring surgical-orthodontic intervention for other conditions.

Outcomes in Computer-Assisted Surgical Simulation for Orthognathic Surgery

Orthognathic surgery is a powerful tool to address skeletal discrepancies of the jaws; however, the model surgery and splint fabrication necessary to successfully complete this surgery are laborious and time consuming. Previous studies have described the utility of computer-assisted surgical simulation (CASS) to eliminate the need for plaster cast model surgery. This article evaluates the implementation of a CASS system for treatment planning and splint fabrication in a series of 11 orthognathic surgery patients. All patients were treatment planned using a CASS system for computer-simulated osteotomies and splint fabrication. As a safety measure, traditional model surgery and splint fabrication were also performed on all cases. Each case was evaluated for accuracy of cephalometric analysis, splint accuracy, splint durability, and ease of treatment planning. All splints fit as well, or better, than those fabricated using traditional methods. In 2 cases, occlusal cants were detected by the CASS system that were undetected by traditional cephalometric analysis and physical examination. In 1 case, the skeletal midline identified on the computed tomographic scan was incongruent with the soft tissue clinical midline of the face, and this discrepancy was recognized and compensated for by correlation of the physical examination and preoperative clinical photos.In this series of 11 patients, the CASS system proved to be an effective mechanism to treatment plan cases and prepare surgical splints for patients undergoing orthognathic surgery.

Accuracy of two face-bow/semi-adjustable articulator systems in transferring the maxillary occlusal cant

The precision of an arbitrary face-bow in accurately transferring the orientation of the maxillary cast to the articulator has been questioned because the maxillary cast is mounted in relation to arbitrary measurements and anatomic landmarks that vary among individuals. This study was intended to evaluate the sagittal inclination of mounted maxillary casts on two semi-adjustable articulator/face-bow systems in comparison to the occlusal cant on lateral cephalograms. Maxillary casts were mounted on the Hanau and Girrbach semi-adjustable articulators following face-bow transfer with their respective face-bows. The sagittal inclination of these casts was measured in relation to the fixed horizontal reference plane using physical measurements. Occlusal cant was measured on lateral cephalograms. SPSS software (version 11.0, Chicago, IL, USA) was used for statistical analysis. Repeated measures analysis of variance and Tukey's tests were used to evaluate the results (P < 0.05). Comparison of the occlusal cant on the articulators and cephalogram revealed statistically significant differences. Occlusal plane was steeper on Girrbach Artex articulator in comparison to the Hanau articulator. Within the limitations of this study, it was found that the sagittal inclination of the mounted maxillary cast achieved with Hanau articulator was closer to the cephalometric occlusal cant as compared to that of the Girrbach articulator. Among the two articulators and face-bow systems, the steepness of sagittal inclination was greater on Girrbach semi-adjustable articulator. Different face-bow/articulator systems could result in different orientation of the maxillary cast, resulting in variation in stability, cuspal inclines and cuspal heights.