Posterior Vertical Dimension Research Articles

Early and 1-year postsurgical stability and its factors in patients with complicated skeletal Class Ⅲ malocclusion treated by conventional and surgery-first approach: A prospective cohort study

This study aimed to compare postsurgical stability between conventional (CSA) and surgery-first (SFA) approaches and investigate its prognostic factors in patients with a skeletal Class Ⅲ extraction. Twenty and 19 patients treated with LeFort I osteotomy and bilateral sagittal split ramus osteotomy (BSSRO) with premolar extraction were enrolled in SFA and CSA groups, respectively. Serial cone-beam computed tomography images obtained before surgery, immediately after surgery (T1), 3 months after surgery, and 12 months after surgery were used for 3-dimensional quantitative analysis. The condyle was segmented for analyzing volumetric changes. Repeated measures analysis of variance, independent t test, and chi-square test were used to compare time-course and intergroup differences. Pearson and Kendall correlation and multivariate linear regression analyses were used to explore prognostic factors affecting skeletal stability. In both CSA and SFA, postsurgical relapse mainly occurred in the mandible sagittal and vertical dimensions and during the first 3 months after surgery. Stability in SFA was significantly less than that in CSA. Intraoperatively, inferolateral condylar displacement with proximal segment inwards, clockwise rotation, and return movements after surgery were observed regardless of the treatment approach. The condylar volume remained stable over time. Multivariate regression analysis showed that posterior vertical dimension (VD) at T1 (-1.63mm), surgical amount of mandibular setback (-10.33 mm), surgical condylar downwards displacement (-1.28 mm), and anterior overjet at T1 (6.43 mm) were the most important predictors of early mandibular relapse (r2= 0.593). The risk of early relapse could be reduced by controlling the anterior, middle, and posterior constraints provided by the prediction model.

Impact of molar teeth distalization by clear aligners on temporomandibular joint: a three-dimensional study

BackgroundMaxillary molar distalization is a common technique used in the non-extraction treatment of Angle Class II malocclusion that can effectively correct the molar relationship and create spaces for anterior teeth alignment. However, this approach may also impact the temporomandibular joint (TMJ) due to predictable changes in the posterior vertical dimension. Despite its widespread use, Class II malocclusions correction by molar distalization with clear aligners has not been investigated for their effects on the TMJ. Therefore, this study aimed to analyze the impact of sequential molar distalization using clear aligners on the TMJ.MethodsThree-dimensional CBCT scans of 23 non-growing patients (7 males, 16 females; mean age 29.8 ± 4.6 years) with skeletal class I or II malocclusion and a bilateral molar class II relationship treated by sequential upper molars distalization with orthodontic clear aligners (Invisalign, Align Technology, San Josè, Ca, USA). A total of 46 joints were examined before and after molar distalization using Anatomage InvivoDental 6.0.3. Linear and angular measurements of the mandibular joint were measured, including joint parameters, inclination, position, and the dimension of the condyle and articular fossa. In addition, 3D volumetric spaces of the joint were analyzed. All data were statistically analyzed by paired T test to determine the differences between the pre-and post-orthodontic procedures.ResultsNo statistically significant differences were found in all primary effects resulting from maxillary molars distalization by clear aligners on TMJ components measurements and joint spaces between T0 and T1. Meanwhile, statistically significant differences were observed in the linear position of the upper molars and the molar relationship parameter with at least P ≤ 0.05.ConclusionTreatment by sequential upper molars distalization with clear aligners does not lead to significant TMJ parameters changes in condyle and fossa spaces, dimensions, and positions.

Management of the Vertical Dimension in the Camouflage Treatment of an Adult Skeletal Class III Malocclusion

Treating skeletal class III malocclusions is one of the biggest challenges in Orthodontics. Given the complexity of these cases, orthognathic surgery is often the best treatment option. However, many patients refuse this treatment due to its risks, morbidity, and costs involved. Alternatively, dental compensation can be planned for some of these skeletal problems. This case report presents a dentoalveolar compensation in the orthodontic treatment of a 20-year-old female patient with class III malocclusion, concave profile, anterior crossbite, mandibular prognathism, maxillary retrusion, and a vertical deficiency in the posterior region. Treatment planning involved a multiloop edgewise archwire (MEAW) associated with intermaxillary elastics with counterclockwise rotation of the occlusal plane in the posterior region of the maxilla aiming at obtaining an increased posterior vertical dimension. After 24 months of treatment, the severe anterior crossbite was corrected, and the skeletal class III relationship was camouflaged. At the end of the orthodontic treatment, it was possible to observe an improved facial profile, a nice smile, and a functional occlusion. The results remained stable at a three-year follow-up. The MEAW, associated with the use of elastics, seems to be an effective treatment option for class III camouflage with reduced posterior vertical dimension with no need for additional anchoring devices but requiring adequate bending of wires and patient compliance.

Mathematical Approach for Predictable Surgical Outcome in Surgery-First Approach Treatment

With surgery-first approach (SF), the posterior vertical dimension (VD) is inevitably increased following orthognathic surgery. The increased VD causes the forward movement of mandible after surgery which corresponds to postsurgical relapse. The purpose of the present study is to suggest a mathematical approach to achieve predictable surgical outcome in orthognathic surgery with SF approach.

Three-Dimensional Evaluation of the Postsurgical Stability of Mandibular Setback With the Surgery-First Approach: Comparison Between Patients With Symmetry and Asymmetry

The purpose of the present study was to evaluate the 3-dimensional postsurgical stability of mandibular setback with a surgery-first (SF) orthodontic treatment approach in patients with skeletal Class III malocclusions and facial asymmetry using cone-beam computed tomographic (CBCT) images. Thirty-six patients who underwent mandibular setback with an SF approach for the correction of mandibular prognathism were enrolled in the present study. Patients were divided into symmetrical (n=18) and asymmetrical (n=18) groups according to their degree of menton deviation. CBCT images were acquired before surgery, 1, 6, and 12months after surgery, and at the end of treatment. After reorienting of CBCT images using automatic volume-based registration, the position of the mandible at each time point was evaluated relative to its post-treatment position. MATLAB (MathWorks, Natick, MA) was used to represent all sequential changes in postoperative mandibular position. The increase in posterior vertical dimension at surgery was measured and then correlated with postsurgical mandibular stability. For up to 6months after surgery, the position of the mandible differed considerably from its post-treatment position. At 12months after surgery, the position of the mandible no longer differed substantially from its post-treatment position. The asymmetry group exhibited greater outward displacement of the proximal segment. The symmetrical and asymmetrical groups exhibited a positive correlation between postsurgical mandibular instability and the increase in posterior vertical dimension. These results indicate that mandibular position stabilizes 12months after surgery performed with an SF approach. It is necessary to consider mandibular forward movement from the increase in posterior vertical dimension in surgical occlusion during the treatment planning stage. Moreover, clinicians should maintain the surgical position of proximal segments during postsurgical orthodontic treatment at least until 12months after surgery.

Restoration of the Vertical Posterior Dimension in a Grinding Patient before Orthodontic Treatment: A Case-Report with Electromyographic Evaluation of Masticatory Muscles Balance

Aim: the aim of this article is to assess the importance of masticatory muscles balance evaluation before improving vertical dimension through conservative and restorative techniques. It also shows how a multidisciplinary approach is needed to obtain a better result for the patient. Background: Bruxism is defined as the parafunctional activity of grinding or clenching of teeth. Management of severe worn dentition in patients with bruxism is challenging since this condition can lead to loss of tooth structure and occlusal vertical dimension (OVD). In some cases the impossibility to correct the proclination of the maxillary incisors occurs due to the posterior tooth wear. Case Description: an orthodontic alignment was obtained after having improved posterior vertical dimension according to an electromyographical analysis using Teethan® electromyographic system. The activity of anterior temporals and masseters was controlled and balanced by electromyography at every step of the treatment. Conclusion: an unbalanced dental occlusal function can compromise the stability of an orthodontic treatment; it is important an evaluation from different points of view in order to rehabilitate the patient in his complex. Clinical significance: electromyography proved itself to be a useful tool in the hands of the clinician to check the oral muscles balance and to avoid temporomandibular joint (TMJ) overload in restorative dentistry, prosthodontics and orthodontics.

Successful treatment of growing skeletal class II children with Twin-Block appliance.

The treatment of skeletal Class II growing patient is to move the mandible into the Class I molar positon via facilitating mandibular growth. The functional appliances are to be designed to exert three major functions such as palatal expansion, forward growth of mandible and increase of the posterior vertical dimension. One of the devices that can achieve both the palatal expansion and the eruption of the mandibular molar is the Twin-Block introduced by Clark in 1982. In this part, we present the treatment method with Twin-Block functional appliance for the correction of skeletal Class II growing patient.

Orthodontic dental casts: The case for routine articulator mounting

To mount or not to mount: that is the question. The famous quotation from Hamlet, slightly transformed, continues: “Whether ’tis nobler in the mind to suffer the slings and arrows of outrageous fortune, or to take arms against a sea of troubles, and by opposing end them. To die, to sleep. Of course, the question of whether to mount dental casts is not worth “suffering slings and arrows,” nor is it worth getting depressed, and certainly we should not commit suicide over it! After all, it’s only an articulator; yes, there are many reasons why we should mount models on an articulator, but let’s think about its clinical importance, use some logical thinking, and take away the passion. To better understand this Point/Counterpoint discussion, we should avoid relating the use of an articulator to a group, a philosophy, or a guru. It is simply what is best for the patient. Researchers have reported that the use of an articulator is not evidenced-based, as stated by Rinchuse and Kandasamy in their article, “Articulators in orthodontics: an evidence-based perspective.” Evidence-based research needs to be put in the proper clinical context. The most relevant question is whether research is always good for clinical practice. This implies that the clinical reality to which it is applied should not be misrepresented to satisfy the demands of the research. Use of the term “evidenced-based” in position-statement papers only confuses the situation. From a clinical perspective, several points should be considered. The articulator is only a clinical tool that we can use to obtain a more complete diagnosis. The more information we have about the patient, the better our diagnosis and eventual treatment. Therefore, concerning its use, it is not a matter of yes or no but, rather, why not? An orthodontist can do good orthodontics without using an articulator, but an articulator can help him or her provide better treatment in many clinical situations. The articulator provides an added dimension that helps in gathering more information by visualization of the pretreatment occlusion in static occlusion, and permits the visualization of various functional movements. In prosthodontics, once the musculoskeletal stable position has been obtained and the patient’s dental casts are mounted on the articulator, posterior teeth can be removed. It is then possible to determine whether the origin of the malocclusion is horizontal, vertical, or transverse. Knowing this in many Angle Class II cases will prevent the clinician from trying to do the impossible in correcting the malocclusion. By doing this easy step in diagnosis, we know the limitations even before placing the first bracket. This information is impossible to obtain with hand-held dental casts, and most orthodontic failures are due to an incomplete diagnosis and not determining the origin of the malocclusion before treatment. Mounted dental casts are an aid to a more complete diagnosis. The following is a list of many important reasons for mounting dental casts on an articulator. 1. It helps in measuring the centric relation-centric occlusion discrepancy in 3 planes of space. This is important information when the goal is to treat to a musculoskeletal stable position. 2. It helps in determining the first contact point (fulcrum point) in centric relation. This is particularly important in patients with a reduced posterior vertical dimension and a vertical or clockwise pattern of growth. This gives a realistic picture of the vertical control mechanics that must be used to correct the malocclusion. 3. It helps in studying the attrition patterns and the proclination of the maxillary incisors in periodontal patients. 4. It helps in determining the need for “trial” treatments. A diagnostic setup on mounted dental casts is often necessary in patients with tooth-size discrepancies. We can determine the needed changes before our actual treatment. Specialist in orthodontics, San Sebastian, Spain. Specialist in orthodontics, Parma, Italy. Reprint requests to: Domingo Martin, Plaza Bilbao 2-2 , San Sebastian, Spain; e-mail, martingoenaga@arrakis.es. Am J Orthod Dentofacial Orthop 2012;141:8-17 0889-5406/$36.00 Copyright 2012 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2011.11.007

Sagittal and vertical effects of rapid maxillary expansion in Class I, II, and III occlusions

To evaluate and compare the skeletal vertical and sagittal effects of the Hyrax expander in Class I, II, and III patients. One hundred and eighty-three patients (91 females, 92 males) with a mean age of 8.7 years and with maxillary bilateral cross-bite and maxillary hypoplasia were analyzed retrospectively. They were divided into three groups according to their skeletal class. Sixty-five patients were skeletal Class I, 55 were skeletal Class II, and 63 were skeletal Class III. For each patient a lateral cephalogram was obtained before treatment and at the end of the retention period. Changes in the groups during the observation period were calculated, compared, and statistically analyzed with a t-test. In terms of vertical effects, a statistically significant increase in the anterior vertical dimension was observed only in Class III patients. No statistically significant changes were observed in the posterior vertical dimension in any of the groups. In terms of sagittal effects, in Class I patients the maxilla and the mandible moved forward, but not in a statistically significant way, and the ANB angle showed a statistically significant decrease, but its change was less modified. In Class II patients the maxilla moved forward, but not in a statistically significant way, while the mandible moved forward in all of the patients in a statistically significant manner. The ANB decreased, statistically improving the skeletal classification. In Class III patients the maxilla moved forward in a statistically significant manner; the mandible showed a downward and backward rotation, improving the skeletal classification. The data obtained in this study permit us to confirm that rapid maxillary expansion can be used in all of the skeletal classes with good vertical and sagittal results.

Occlusal plane change after intrusion of maxillary posterior teeth by microimplants to avoid maxillary surgery with skeletal Class III orthognathic surgery

To increase stability and mandibular setback movement, surgical maxillary impaction is normally performed with mandibular setback surgery in treating adult skeletal Class III patients. This article demonstrates the use of microimplants for anchorage to intrude molars and the resultant rotation of the maxillary occlusal plane clockwise to increase the surgical mandibular setback and reduce the posterior vertical dimension instead of maxillary surgical impaction. A 21-year-old man with mandibular prognathism was treated with mandibular setback surgery that included orthodontic treatment for decompensation. Microimplants placed into the palatal alveolar bone between the maxillary first and second molars were used to intrude the maxillary posterior teeth and change the occlusal plane clockwise. This produced 4 mm more of distal movement of the chin during mandibular setback surgery compared with the surgical prediction with no change in the occlusal plane. These results were similar to those of 2-jaw surgery with maxillary posterior impaction. The intrusion of the maxillary posterior teeth with microimplants might prevent the need for maxillary surgery in adult skeletal Class III patients.

Indications for open reduction and closed reduction treatment

The treatment of condylar fractures is still a highly debated theme. With the advent of stable internal fixation devices, open treatment has become more popular. However, there is still no universal agreement on the indications for open or closed treatment. These seem to vary with every surgeon who treats such injuries. This talk will focus on factors that may be taken into account when one decides how a given condyle fracture is to be treated. The basis of the talk, however, will be that the majority of condylar fractures can be treated satisfactorily by closed techniques. The question is, Which fractures might have better outcomes when treated open? Absolute Indications for Open Treatment 1.Displacement of condyle into the middle cranial fossa (with or without fracture)2.Lateral extracapsular displacement of condyle (with or without fracture)3.Impossibility of obtaining proper occlusion by closed techniques4.Condylar fractures associated with comminuted fractures at or above the LF 1 level Relative Indications for Open Treatment All other condylar fractures may be treated closed or open. The decision to choose one method over another will vary depending upon the experience and philosophy of the surgeon, the expected outcomes from either treatment, and the factors discussed below. I therefore will not list any relative indications because what is a relative indication in my opinion may not be in another’s. I. Loss of Ramus Height. Fractures that are displaced will lead to decreases in the height of the ramus. In most cases this loss of ramus height is acceptable and will be manifest by a small cant in the occlusal plane (if the fracture is unilateral). However, if few posterior teeth are present, control of ramus height by functional (non-surgical) therapy will be difficult and large losses of ramus height may occur. II. Skeletal Maturation of Patient. Skeletally immature individuals possess the unique ability to regenerate the entire condylar process after fracture/dislocation. They also function more symmetrically after non-surgical treatment. On the other hand, skeletally mature individuals have a more limited capacity for condyle regeneration/restitution. Further, most studies indicate more functional disturbances to the masticatory system in later years in such individuals than in those injured when skeletally immature. III. Feasibility of Open Reduction and Internal Fixation. High-level fractures pose a problem in that they do not have adequate bulk to perform stable osteosynthesis. In such cases, one may select non-surgical treatment. Other factors that relate to the choice between surgical and non-surgical treatment are the general health of the patient, the pre-traumatic occlusal relationship, and the desire to avoid intermaxillary fixation/traction. IV. Associated Fractures. When bilateral condylar fractures are present, especially those that are displaced, treatment using closed techniques is extremely difficult, even when a full complement of teeth is present. Treatment will be prolonged and many adaptations, including anterior dental extrusion, will occur out of necessity to maintain the pre-trauma occlusal relationship. Open treatment of at least one fracture seems to improve the occlusal outcomes. V. State of the Dentition. Closed techniques all rely on using the dentition to position the mandible while the new articulation is established. Patients who have an incomplete dentition present a challenge for closed treatment of the condylar fracture, and might necessitate the fabrication of splints to maintain the posterior vertical dimension. Open treatment may be more efficient and may produce improved outcomes in such cases. References Zide MF, Kent JN: Indications for open reduction of mandibular condyle fractures. J Oral Maxillofac Surg 41:89, 1983 Konstantinovic VS, Dimitrijevic B: Surgical versus conservative treatment of unilateral condylar process fractures: Clinical and radiographic evaluation of 80 patients. J Oral Maxillofac Surg 50:349, 1992 Ellis E: Condylar process fractures of the mandible. Fac Plast Surg 16:193, 2000

Cross-sectional study of the evolution of the primary dentition: shape of dental arches, overjet and overbite

The aim of this study was to evaluate the characteristics (shape of dental arches, overjet and overbite) of the primary dentition of 6- to 39-month-old children from four nurseries of Rio de Janeiro, Brazil, and to associate them to gender and dentition phase. It was observed that 68.6% of the children presented round upper arch, while 31.4% had triangular upper arch; 92% of the children presented U-shaped lower arch and 8% had square-shaped lower arch. Moderate overjet was observed in 38.3% of the children, and slight overjet, in 30.3%. Severe (26.6%) and negative (25.5%) overbites were the most prevalent modalities of that condition. There was no association between gender and the studied characteristics. There was statistically significant association between the dentition phase and the shape of the arch, overjet and overbite (p < 0.001, chi-square test). It was possible to observe, in the present study, that early signs of malocclusions appeared when first primary molars erupted, as the posterior vertical dimension of occlusion increased. It was, thus, verified that early signs of malocclusions appear as the primary dentition develops. It is very important that the first dental visit occur during the first year of age, since it allows the pediatric dentist to prevent or carry out an early diagnosis of malocclusions in the primary dentition.

Facial balance and harmony: An attainable objective for the patient with a high mandibular plane angle

Facial balance is an attainable goal of orthodontic treatment. If it is within the power of the orthodontist to favorably affect facial balance, doing so should be an overriding priority. The question, “What can be done to preserve or enhance facial balance, harmony, and proportion?” should be answered during diagnosis in any patient who presents for orthodontic treatment. The purpose of this paper is to offer some answers to this question when the patient has a medium to high Frankfort mandibular angle or, stated differently, a moderate to excessive anterior facial height. If facial balance is to be a reality for patients with these skeletal patterns, the following three objectives must be met during treatment: (1) The mandibular incisors must be upright or overly upright over their bony support. (2) Anterior facial height must be controlled. (3) Posterior vertical dimension must be controlled. If these three objectives are realized during active mechanotherapy of moderate- to high-angle patients, balance and harmony of the lower face should be an attainable goal.

Corticosteroid-induced mandibular growth retardation and palatal malformation in the ICR mouse fetus

Pregnant ICR mice were treated with triamcinolone hexacetonide at various stages of gestation. The mandibular ramus and its condylar cartilage were studied histologically in both viable and non-viable offspring. In addition, measurements were made of the overall height of the posterior vertical dimension of the mandible and of condylar height and width. Significant changes were noted in these parameters. Concomitantly, marked changes were observed in the various zones of the condylar cartilage. A very high incidence of cleft palate was noted in newborn and stillborn mice previously treated with triamcinolone. A possible correlation between mandibular growth retardation and palatal clefting is discussed.

Mandibular growth retardation in corticosteroid-treated juvenile mice.

Juvenile mice were treated for up to eight weeks with weekly doses of a synthetic analogue of cortisol:triamcinolone hexacetonide. The mandibular condylar cartilage was studied histologically and histochemically at regular intervals. Morphometric measurements were performed along the mandibular posterior vertical dimension (condylar process and ramus). By the second injection significant morphological changes were noted in the condylar cartilage, followed by retardation of bone growth. The most distinctive feature in the cartilage of triamcinolone-treated mice was a marked increase in the dimension of its mineralized zone concomitant with a significant increase in the number of hypertrophic chondrocytes. The role of condylar cartilage in mandibular growth is discussed.

Skeletal Changes in the Condylar Cartilage of the Neonate Mouse Mandible

Histological and histochemical qualitative and quantitative determinations are provided concerning the skeletal changes taking place in the growth center of the mandibular condyle in the neonatal ICR mouse. This study followed the changes in both the major matrical components (collagen, acidic glycosaminoglycans and glycolipids) as well as in the various cartilage cells throughout the maturational period of the neonatal condyle. It was found that the transformation of neonatal condylar cartilage to its mature form involved a significant decrease in its acid glycosaminoglycan content concomitant with a rapid increase in its collagen content. In addition, significant quantitative changes were found within the zone of hypertrophic chondrocytes. The period of highest growth activity along the mandibular posterior vertical dimension (ramus) was between birth and weanling 3rd postnatal week). At this time interval, the adaptive abilities of the growing condyle appeared maximal. A high degree of correlation was noted between the overall reduction in the height of the condylar cartilage and that of its hypertrophic zone. Further, the increase in the ramal height was highly correlated with the structural changes characteristic of the neonatal condyle.