Mandibular Displacement Research Articles

Kinematic performance of a novel temporomandibular joint replacement prosthesis under bite-force conditions in dogs and cats.

To evaluate the kinematics and stability of the temporomandibular joint (TMJ) of cats and dogs with and without a TMJ replacement (TMJR) prosthesis under simulated bite forces and mouth opening. Sixteen cadaver skulls from domestic cats (n = 8) and medium- to large-breed dogs (n = 8). Intact TMJs were tested. Following condylectomy and coronoidectomy, the skulls were fitted with a TMJR prosthesis unilaterally and retested. Prosthesis was similarly implanted in the contralateral TMJ in 4 cats and 4 dogs before retesting. Left and right bite motions were evaluated before bite contact to peak bite force (200 N in dogs, 63 N in cats). Mouth opening motion was recorded. Mandibular displacement under load was evaluated in 3 orthogonal planes. Maximal displacement was compared between TMJR groups and native TMJ. Prosthesis-bone motion of the temporal and mandibular components was evaluated during simulated bites and mouth opening. TMJR resulted in joint motion not demonstrably different from the native TMJ, with the ability to fully open and close the mouth and with minimal laterotrusion. The TMJR prosthesis demonstrated similar stability after unilateral and bilateral replacement during bite force and with an open mouth. Mean implant-bone motion during bite simulations for the temporal and mandibular TMJR components was ≤ 60 µm in cats and ≤ 30 µm in dogs. A novel TMJR can be implanted and allows normal jaw motion. Joint stability is maintained after TMJR implantation in the TMJ of dogs and cats TMJ that is devoid of muscular support.

Mandible Position and Chewing Preference Side Do Not Alter Plantar Support in Children Aged 4-11 Years.

Mandible positioning can cause global postural adaptations. Physiotherapists and dentists try to relate the mandible position and chewing side to plantar support; however, this indication is uncertain. To check the existence of a relationship between mandible position, preferred chewing side, age, and plantar support in children. This is a cross-sectional study with 93 children, aged between 4 and 11 years. Photogrammetry was used to confirm the mandibular positions (centralized, to the right, and to the left), and baropodometry was used to measure plantar support. The mandibular displacement distance to the right and left was evaluated, and the plantar support in the three mandibular positions was compared as a function of age (4-7 and 8-11 years) and preferred chewing side. There was greater mandibular displacement in left laterality [13 (9-19) cm] compared to right laterality [7 (3.50-12.00) cm] (p < 0.01). Mandibular position did not alter mean pressure, maximum pressure, or plantar support surface (p > 0.05). With the mandible centralized, higher mean pressure, maximum pressure, and surface area were observed in the left foot (p < 0.01). Older children showed greater mandibular displacement to the left (p < 0.01). No differences were observed for the variables of plantar support as a function of age (p > 0.05) and chewing side (p > 0.05). There was a moderate to strong correlation between age, body mass, height, and plantar surface area (0.63 < r < 0.83; p < 0.05) and between mean and maximum pressures of plantar support (0.58 < r < 0.89; p < 0.05). Mandibular position, age, and preferred chewing side do not influence plantar support in children. Bittar KCB, Zamboti CL, Macedo CSG. Mandible Position and Chewing Preference Side Do Not Alter Plantar Support in Children Aged 4-11 Years. Int J Clin Pediatr Dent 2024;17(6):658-664.

Biomechanical evaluation of various rigid internal fixation modalities for condylar-base-associated multiple mandibular fractures: A finite element analysis.

Condylar-base-associated multiple mandibular fractures are more prevalent than single ones. Direct trauma to mandibular symphysis, body or angle are prone to induce indirect condylar fracture. However, little is known about the effects of various rigid internal fixation modalities in condylar base for relevant multiple mandibular fractures, especially when we are confused in the selection of operative approach. Within the finite element analysis, straight-titanium-plate implanting positions in condylar base contained posterolateral zone (I), anterolateral zone (II), and intermediate zone (III). Von Mises stress (SS) in devices and bone and mandibular displacement (DT) were solved, while maximum values (SSmax and DTmax) were documented. For rigid internal fixation in condylar-base-and-symphysis fractures, I + II modality exhibited least SSmax in screws and cortical bone and least DTmax, I + III modality exhibited least SSmax in plates. For rigid internal fixation in condylar-base-and-contralateral-body fractures, I + III modality exhibited least SSmax in screws and cortical bone, I + II modality exhibited least SSmax in plates and least DTmax. For rigid internal fixation in condylar-base-and-contralateral-angle fractures, I + III modality exhibited least DTmax. The findings suggest that either I + II or I + III modality is a valid guaranty for rigid internal fixation of condylar base fractures concomitant with symphysis, contralateral body or angle fractures.

Evaluation of bone contact area and intercondylar distance changes in orthognathic surgery - a comparison between BSSO and HSSO technique depending on mandibular displacement extent

ObjectivesThe present study aims to assess the impact of bilateral and high oblique sagittal split osteotomy (BSSO/HSSO), as well as displacement distances and directions on the expected and achievable bone contact area (BCA) and changes in the intercondylar distance (ICD). The primary question addressed is whether mandibular splitting through BSSO results in a greater BCA and/or ICD when compared to splitting through HSSO.Materials and methodsTotally 80 mandibular displacements were performed on 20 fresh cadavers, for each subject, four splints were produces to facilitate mandibular advancement as well as setbacks of 4 and 8 mm. Pre- and postoperative CBCT scans were performed to plan the surgical procedures and to analyze the expected and achieved BCA and ICD.ResultsRegarding the maximum mandibular displacement, the expected BCA for HSSO/BSSO were 352.58 ± 96.55mm2 and 1164.00 ± 295.50mm2, respectively, after advancement and 349.11 ± 98.42mm2 and 1344.70 ± 287.23mm2, respectively, after setback. The achieved BCA for HSSO/BSSO were 229.37 ± 75.90mm2 and 391.38 ± 189.01mm2, respectively, after advancement and 278.03 ± 97.65mm2 and 413.52 ± 169.52 mm2, respectively after setback. The expected ICD for HSSO/BSSO were 4.51 ± 0.73 mm and 3.25 ± 1.17 mm after advancement and − 5.76 ± 1.07 mm and − 4.28 ± 1.58 mm after setback. The achieved ICD for HSSO/BSSO were 2.07 ± 2.9 mm and 1.7 ± 0.60 mm after advancement and − 2.57 ± 2.78 mm and − 1.28 ± 0.84 mm after setback. Significant differences between the BCA after HSSO and BSSO were at each displacement (p < 0.001), except for the achieved BCA after 8-mm setback and advancement (p ≥ 0.266). No significant differences were observed regarding ICD, except for the expected ICD after 8-mm setback and advancement (p ≤ 0.037).ConclusionsCompared to the virtual planning, the predictability regarding BCA and ICD was limited. ICD showed smaller clinical changes, BCA decreased significantly in the BSSO group.Clinical relevanceBCA and ICD might have been less important in choosing the suitable split technique. in orthognathic surgery.

Evaluation of condylar and mandibular movements on the upper airway during the use of mandibular advancement device for obstructive sleep apnea treatment.

To evaluate the temporomandibular joint (TMJ), condylar and mandibular movements in obstructive sleep apnea (OSA) patients treated with mandibular advancement device (MAD) and to identify the influence of these anatomic factors on upper airway (UA) volume and polysomnographic outcomes after treatment. Twenty OSA patients were prospectively treated with MAD. Clinical examinations, cone-beam computed tomography, and polysomnography were performed before MAD treatment and after achieving therapeutic protrusion. Polysomnographic variables and three-dimensional measurements of the TMJ, mandible, and upper airway were statistically analyzed. Condylar rotation, anterior translation, and anterior mandibular displacement were directly correlated with total UA volume, while vertical mandibular translation was inversely correlated with the volume of the inferior oropharynx. MAD treatment resulted in an increase in the volume and area of the superior oropharynx. There was no statistically significant correlation between condylar rotation and translation and polysomnographic variables. With MAD, there was a significant increase in vertical dimension, changes in condylar position (rotation and translation), and mandibular displacement. The central and medial lengths of the articular eminence were inversely correlated with condylar rotation and translation, respectively. The lateral length of the eminence was directly correlated with condylar translation, and the lateral height was directly correlated with condylar rotation and translation. Condylar and mandibular movements influenced UA volume. The articular eminence played a role in the amount of condylar rotation and translation. Individualized anatomical evaluation of the TMJ proves to be important in the therapy of OSA with MAD.

Quantifying bone healing after mandibular displacement in orthognathic surgery

Impaired bony healing following bilateral sagittal split osteotomy (BSSO) is a major unmet medical need for affected patients, and rare occurrences can hinder the identification of underlying risk factors. We hypothesised that osseous union following BSSO can be quantified using volumetric analysis, and we aimed to identify the risk factors for impaired bone healing. The percentage change in bony volume was measured in orthognathic patients following BSSO using two consecutive postoperative cone-beam computed tomography scans. Patients’ characteristics and treatment parameters were documented, and correlation and regression analyses of these variables performed. Thirty-six patients (23 men and 13 women) with a mean (SD) age of 33.28 (11.86) years were included. The gap site (lingual versus buccal) (p < 0.01) had a significant impact on the change in volume. Age (p = 0.06) showed a trend towards significance. Initial width of the osteotomy gap, sex, and indication for surgery did not influence osseous healing. Increased age at surgery and the side of the buccal osteotomy are independent risk factors for impaired osseous healing following BSSO.

Comparison outcome of open and close reduction treatments for parasymphysis mandibular fractures

Background: Mandibular fracture is a condition of mandibular discontinuity. The treatment aims to reconstruct the appropriate anatomical position. Reduction is the process of repositioning fracture fragments to their original anatomical positions, which can be done by open and closed techniques. Open reduction is more invasive, and the possibility of nerve or blood vessel injury and infection postoperatively is greater. Closed reduction also has postoperative complications such as muscle atrophy, periodontal tissue and mucosa damage, speech disorders, and nutritional disorders. In the final determination of the treatment plan, the advantages, disadvantages, and risks of each treatment and the risk of complications should be sufficiently discussed with patients and the patient’s guardians. Purpose: This case aims to compare the outcome of open reduction and internal fixation (ORIF) with closed reduction treatment in the management of mandibular parasymphysis fractures. Cases: Two case studies of mandibular parasymphysis fractures. Clinically, each patient had mandibular displacement and occlusion disturbance before treatment. Case Management: The treatment plan is considered by the patient’s age and fracture type. One patient received ORIF, and the other received close reduction treatment with gradual repositioning. Malocclusion after treatment was absent in both cases. Conclusion: Open reduction is recommended for displaced parasymphysis fractures. In cases where the open reduction technique cannot be performed, the closed technique can be an alternative, especially on non-displaced or minimally displaced parasymphysis fractures.

Management of Anterior Single Tooth Crossbite Using Removable Posterior Teeth Bite Plane Along With Z-Spring: A Case Report

Anterior crossbite is defined as a malocclusion characterized by the anterior maxillary teeth lingual position compared to mandibular anterior teeth. The prevalence of anterior crossbite that has been reported in the mixed dentition stage varies between 1.6 percent and 7.9 percent. Anterior crossbite cases should be treated by emergency intervention in the early period to prevent the consequences of malaligned teeth and their effect on the normal overall growth and development of the child. Patient compliance in such type of treatment intervention is of utmost importance. This case report presents the correction of single tooth crossbite with the removable posterior bite plane along with Z-spring. Various other treatment modalities have been also proposed to correct an anterior dental crossbite, such as tongue blades, reversed stainless steel crowns, fixed acrylic planes, bonded resin-composite slopes, and removable acrylic appliances incorporating finger springs. This treatment modality is possible in the early stages of developing malocclusion. Children with untreated anterior crossbite could develop complications such as gingiva recession, TMJ dysfunction, and worsening of mandibular displacement. As self-correction is rare in these alterations, early interception is recommended to allow normal occlusion and facial development.

Three-dimensional bone remodelling of glenoid fossa in patients with skeletal Class III malocclusion after bimaxillary orthognathic surgery

This study aimed to characterize three-dimensional quantitative morphological changes of glenoid fossa in patients with skeletal Class III malocclusion treated with bimaxillary orthognathic surgery. Ninety-five eligible patients (50 male, 45 female; mean age 22.09 years) were enrolled retrospectively. Cone beam computed tomography obtained at 1 week preoperatively (T0), immediately after surgery (T1), and at ≥ 12 months postoperatively (T2) were registered based on cranial base using voxel-based registration in 3D Slicer. Glenoid fossa surface was divided spatially into four regions, and bone modelling in these regions was visualized with color maps. Our data revealed that the mean surface variations of glenoid fossa were small, with modest bone formation as a whole. No significant associations between anteroposterior or vertical mandibular displacement and overall glenoid fossa remodeling were found (P > 0.05). Moreover, bone deposition was frequently observed in the anterior-lateral region of glenoid fossa in patients with a larger mandibular movement during T0–T1 (P < 0.001). Paired bone formation in the anterior-lateral region of glenoid fossa and bone resorption in the anterior-lateral region of condylar head was frequently observed. Collectively, our results revealed that glenoid fossa underwent complex but modest bone remodeling after bimaxillary surgery in skeletal Class III patients.

Three-dimensional comparison between the effects of mandibular advancement device and maxillomandibular advancement surgery on upper airway

BackgroundThe efficacy of mandibular advancement devices (MAD) and maxillomandibular advancement (MMA) in improving upper airway (UA) patency has been described as being comparable to continuous positive airway pressure (CPAP) outcomes. However, no previous study has compared MAD and MMA treatment outcomes for the upper airway enlargement. This study aimed to evaluate three-dimensionally the UA changes and mandibular rotation in patients after MAD compared to MMA.MethodsThe sample consisted of 17 patients with treated with MAD and 17 patients treated with MMA matched by weight, height, body mass index. Cone-beam computed tomography from before and after both treatments were used to measure total UA, superior/inferior oropharynx volume and surface area; and mandibular rotation.ResultsBoth groups showed a significant increase in the superior oropharynx volume after the treatments (p = 0.003) and the MMA group showed greater increase (p = 0.010). No statistical difference was identified in the MAD group considering the inferior volume, while the MMA group showed a significantly gain (p = 0.010) and greater volume (p = 0.024). Both groups showed anterior mandibular displacement. However, the mandibular rotation were statistically different between the groups (p < 0.001). While the MAD group showed a clockwise rotation pattern (-3.97 ± 1.07 and − 4.08 ± 1.30), the MMA group demonstrated a counterclockwise (2.40 ± 3.43 and 3.41 ± 2.79). In the MAD group, the mandibular linear anterior displacement was correlated with superior [p = 0.002 (r=-0.697)] and inferior [p = 0.004 (r = 0.658)] oropharynx volume, suggesting that greater amounts of mandibular advancement are correlated to a decrease in the superior oropharynx and an increase in the inferior oropharynx. In the MMA group, the superior oropharynx volume was correlated to mandibular anteroposterior [p = 0.029 (r=-0.530)] and vertical displacement [p = 0.047 (r = 0.488)], indicating greater amounts of mandibular advancement may lead to a lowest gain in the superior oropharynx volume, while a great mandibular superior displacement is correlated with improvements in this region.ConclusionsThe MAD therapy led to a clockwise mandibular rotation, increasing the dimensions of the superior oropharynx; while a counterclockwise rotation with greater increases in all UA regions were showed in the MMA treatment.

РАСПРОСТРАНЕННОСТЬ ЗУБОЧЕЛЮСТНЫХ АНОМАЛИЙ У ДЕТЕЙ СВЕРДЛОВСКОЙ ОБЛАСТИ

The problem of studying the prevalence of dentofacial abnormalities in children in the Sverdlovsk region is relevant, as the data for different regions are differ, which is confirmed by the heterogeneity of indicators and statistics in the research. In 2022, an epidemiological study was conducted among the children's population of 4 cities of the Sverdlovsk region to study the prevalence of dentofacial abnormalities in the age groups 3–5, 6, 12 and 15 years, a total of 455 children were examined. Registration of dentofacial abnormalities was carried out in the author's card of dentofacial system disorders developed, using the classifications of MGMSU and ICD-10. Statistical processing of the data obtained was carried out in STATISTICA 13.3. The study revealed a high prevalence of dentofacial abnormalities in children in the Sverdlovsk region – 71.43% ± 2.12. With age, there is a tendency to increase the frequency of dentofacial abnormalities: in children 3–5 years of dentofacial abnormalities were in 34.85% ± 5.87 cases; in the group of 6-year-olds – in 70.18% ± 4.28; and in groups of 12-year-old and 15-year-old children – 81.38% ± 3.23 and 80.00%. It was revealed that the older the children are, the more likely they have severe malocclusion compared to children aged 3–5 and 6. The groups noted high rates of dentition deformities, the number of which also increases with age (decrease in the length of the upper dentition was detected in 36.26% ± 2.25, the lower dentition – in 47.47% ± 2.34 of cases; narrowing of the upper dentition – in 55.60 ± 2.33%, lower dentition – in 45.49% ± 2.33 of cases). Dentition deformities are associated with the development of teeth abnormalities, such as teeth retention (13.10% ± 2.80 and 9.23% ± 2.54 of cases in 12- and 15-year-old children, respectively), as well as mandibular displacement (displacement to the side was detected in 22.20% ± 1.95 of cases). Performed study is justification for the development and implementation of a regional program for the prevention of dental diseases in children of the Sverdlovsk region.

Atypical Neuralgia of Lingual Nerve after General Anesthesia: A Case Report

Objectives: Injury of lingual nerve is a rare complication of general anesthesia. The causes of lingual nerve injury following general anesthesia are multifactorial; possible mechanisms may include difficult laryngoscopy, prolonged anterior mandibular displacement, improper placement of the oropharyngeal airway, macroglossia and tongue compression. Case Report: A case of atypical neuralgia of lingual nerve that was associated with orotracheal intubation for 54 years old female. Treatment: Carbamazepine was effectively aided the recovery of the injured lingual nerve. Conclusion: Lingual nerve injury following orotracheal intubation is rare but can cause irritation to patients.

Clinical finite element analysis of mandibular displacement model treated with Twin-block appliance

The mechanical distribution of the mandible is an important factor that affects functional orthosis during Twin-block (TB) appliance correction. Changes in the mandible before and after TB appliance correction are also key factors in maintaining the therapeutic effect. Finite element analysis, a powerful numerical, analytical tool, is widely used to predict the stress and strain distribution of the craniofacial bone that orthodontics generates. The sample was a 14-year-old male patient with Class II malocclusion during growth. A cone-beam computed tomography scan was undertaken at pretreatment and posttreatment. In the Finite element analysis of the pretreatment model, the remote displacement model of the mandible was established with the sella point as the center. A mandibular model under TB appliance loading was established. Its mandibular displacement and von Mises stress were compared before and after loading. Three-dimensional registration was conducted on the pretreatment and posttreatment models to measure the sagittal displacement of the centrosome. The force on the mandible occurred mainly in the condyle neck and medial mandible after the TB appliance moved the mandible. After displacement, the posterior upper margin of the condyle was farther away from the articular fossa. Three-dimensional registration results showed that new bone had formed behind and above the condyle after TB appliance treatment. The TB appliance provides additional advantages in treating skeletal Class II malocclusions by helping to reduce the burden on the temporomandibular joint and promoting the adaptive reconstruction of the mandible.

Evaluation of the Effectiveness of a Neck Fixation Device for Improving Image Quality in Diffusion-weighted Whole-body Imaging with Background Suppression

The effectiveness of a neck fixation device to improve the image quality of DWIBS was investigated. Healthy volunteers were examined while chewing with and without a neck fixation device using a 3-T MRI system. Distance of mandibular movement was measured using true-fast imaging of steady-state precession (true FISP). Signal-to-noise ratio (SNR) and apparent diffusion coefficient (ADC) of DWIBS were measured. Image quality of DWIBS was scored by visual evaluation. These values were compared with and without a neck fixation device. Regarding results, the mandibular displacement and ADC were decreased, and the SNR and visual score were increased by the use of the fixation device. There is a significant difference between with and without a neck fixation device in each measurement. The technique using a neck fixation device helps improve image quality of DWIBS in the head and neck region.

Histological and Biochemical Analysis after Posterior Mandibular Displacement in Rats.

The present study aimed to investigate any biochemical and histological changes of the rat condyle and mandible in animals that had sustained mandibular growth restriction. Seventy-two male Wistar rats were divided into two equal groups, experimental and control. Each group consisted of three equal subgroups. The animals were sacrificed 30, 60, and 90 days after the start of the experiment. Blood samples were collected from the eye, and the osteoprotegerin (OPG), Receptor Activator of Nuclear Factor Kappa B Ligand (RANKL), and Macrophage Colony-Stimulating factor (MCSF)concentrations were measured by using enzyme-linked immunosorbent assay (ELISA) kits. A histological analysis was performed on the mandibular condyles. The blood serum values of OPG, RANKL, and MCSF did not exhibit any statistically significant difference between groups or subgroups. However, significant histological changes became evident after a histomorphometric condylar examination was performed. The Bone Surface/Total Surface ratio appeared reduced in the anterior and posterior regions of the condyle. In addition, the Posterior Condylar Cartilage Thickness was measured and determined to be significantly diminished. The present intervention that employed orthodontic/orthopedic devices did not prove to have any significant effect on the circulating proteins under study. Posterior displacement of the mandible may culminate only in local histological alterations in condylar cartilage thickness and its osseous microarchitecture.

Relationship between mandibular position and support planting in 7-year-old children: pilot study

Introduction: Postural stability can be maintained in balance by muscle tone [1]. Change in the mandibular position or posture, may have influence in the postural reflex, defined as an involuntary defense movement [2] to correct deviations and keep the body in balance. If the postural change is constant, the muscles will move the mandible to a more comfortable position, with consequent postural change2 and plantar support. The aim of the study was to compare the plantar support in centralized and in lateralization mandibular position in seven years’ children. Main text: This study was approved by research ethics committee (No. 4.346.542). A pilot study was carried out with seven-year-old children of both sexes. Photogrammetry was performed with spherical markers in the region of the right tragus and chin symphysis (Fig. 1) concomitantly with baropodometry following (Fig. 2, 3) the protocol established by Bittar et al. [4]. Analysis of mandibular displacement and plantar support were performed with centralized mandibular position (maximum intercuspation) and with lateral displacement to the right and left. Statistical analysis compared the differences in mandibular displacement to the right and left sides using Student’s t test. Differences in plantar support variables with centralized mandibular position and in right and left lateralization position were established by the Anova one way test and the Bonferroni pos test. Significant statistical difference was reached by 5 %. Results: Twelve seven-year-old children were included, 20.8 (3.25) Kg and 1.18 (0.06) meters. The sample present greater lateral displacement of the mandible to the lefts compared to right side. Mandibular lateralization was confirmed with statistical difference compared to mandibular position centralized. No difference in all plantar support variables was observed between the three positions: centralized and left and right lateralization. Conclusions: No differences were observed for plantar support compared position in mandibular lateralization and centralized position. Mandibular lateralization displacements did not change plantar support.

Factors Affecting Mandibular Growth and Displacement and Their Effect on Treatment Outcome

Orthodontists often have difficulty distinguishing between growth and displacement when it comes to the mandible and often the two are merged into one and referred to as just mandibular growth. It is clinically important to distinguish between the two as it can greatly affect the choice of treatment protocol and mechanics. In this review we shall attempt to clarify the issue with clinical examples in the hope of bringing more understanding to the problem. Controlling the factors that are involved in determining the outcome of orthodontic treatment in a growing patient can often be a difficult task and is affected by the stage of maturation. This is particularly problematic if the patient is in a slow growth phase. In some instances, this has led to the unfortunate conclusion that early or interceptive treatment is a waste of time and not only has it caused frustration for the clinician and family but also as it may result in extra cost when two phases of treatment may be needed to correct the malocclusion. With a better understanding of the factors that determine growth and displacement of the mandible better choices of treatment time and mechanics can be made and the correction of a particular malocclusion can be more successful. In the following we shall discuss the factors that affect mandibular displacement and how growth and orthodontic tooth movement affect the outcome. We shall show examples of patients where the lack of adequate condylar growth results in unfavorable displacement of the chin and others where pronounced forward displacement of the chin is the result of excessive condylar growth. We shall further discuss the role of vertical control in cases where the inherited mandibular growth pattern does not favor forward mandibular growth.

The effect of mandibular flexure on the design of implant-supported fixed restorations of different facial types under two loading conditions by three-dimensional finite element analysis.

Objective: Investigating the biomechanical effects of mandibular flexure (MF) on the design of implant-supported fixed restorations in edentulous jaws of different facial types. Methods: Three-dimensional finite element models were established to analyze mandibular displacement and stress distribution of implant-supported fixed restorations (four or six implants, different implant numbers and sites, and the design of the superstructure across the dental arch in one or two or three pieces, under the loading conditions of maximum opening or right unilateral molar occlusion) in mandibular edentulous patients of three different facial types (brachyfacial, mesofacial, and dolichofacial types). Results: The brachyfacial type presented higher mandibular flexure and stress in the overall restorative system, followed by the mesofacial and dolichofacial types. During jaw opening and occlusal movements, the one-piece framework showed the lowest bone stress values surrounding the anterior implants and gradually increased to the distal position, and the three-piece framework showed the highest stress values for peri-implant bones. Also, the split framework could greatly increase the stress on abutments and frameworks. Moreover, fixed implant prostheses with cantilevers can generate high amounts of biomechanical stress and strain on implants and surrounding bones. The bone surrounding the anterior implant increased in stress values as the most distal implants were more distally located regardless of frameworks. The zirconia framework demonstrated higher stresses than the titanium framework. Conclusion: The design of edentulous fixed implant-supported restorations can be optimized for facial types. For patients of the brachyfacial type or with high masticatory muscle strength, the non-segmented framework without a cantilever provides an optimal biomechanical environment.

Three-dimensional cone-beam computed technology evaluation of skeletal and dental changes in growing patients with Class II malocclusion treated with the cervical pull face-bow headgear appliance

This study aimed to 3-dimensionally quantify and compare the outcomes of growing patients with Class II malocclusion treated with the cervical pull face-bow headgear appliance in combination with full fixed orthodontic appliances. The study sample consisted of 22 patients with Class II malocclusion with the following inclusion criteria: ANB>4.75°, Class II molar relationship, and SN-GoGn<37°. The mean age of patients was 12.5 ± 1.1 years at baseline. The average treatment time was 27.7 ± 7.3 months. Cone-beam computed tomography scans were superimposed in the cranial base, maxillary regional, and mandibular regional to evaluate growth, treatment displacements, and bone remodeling. Relevant statistically and clinically significant skeletal changes included average decreases in ANB (2.1 ± 1.1°) and SNA (1.8 ± 1.1°); posterior (1.3 ± 1.4 mm) and inferior (4.6 ± 2.2 mm) displacement of A-point; inferior displacements of B-point (5.4 ± 2.8 mm) and Pogonion (5.8 ± 2.6 mm); superior displacement of Condylion (6.9 ± 2.4 mm); increase in mandibular length (5.4 ± 2.0 mm); and clockwise rotation of palatal plane (1.9 ± 1.9°). Significant proclination of the maxillary incisors (9.8 ± 11.1°) and nonsignificant proclination of the mandibular incisors (4.7 ± 9.6°) were also noted. Class II skeletal correction was primarily achieved by posterior, inferior displacement of the sagittal position of the maxilla. Change in the sagittal position of the mandible/chin (B-point, Pogonion) was not significant; rather, mandibular displacement was significant in an inferior vertical direction without backward rotation, as seen from marked condylar and ramus growth.

Three-Dimensional Analysis of Posterior Mandibular Displacement in Rats

Mandibular protrusion and its treatment is challenging for the orthodontist. The aim of the present research was to identify macroscopic changes in the mandible, based on three-dimensional Cone Beam Computed Tomography analysis. Seventy-two male Wistar rats were divided into two equal groups, experimental (group A) and control (group B). Each consisted of three equal subgroups of 12 rats (A1, A2, A3, B1, B2, B3). Full-cast orthodontic intraoral devices were attached to the maxillary incisors of the experimental animals, and effected functional posterior mandibular displacement. Throughout the experimental period, all animals were fed with mashed food. Animals were sacrificed at 30 days (A1, B1), 60 days (A2, B2) and 90 days (A3, B3). At the 60th day of the experiment, the orthodontic devices were removed from the remaining experimental subgroup A3. Measurements revealed significant differences in the anteroposterior dimensions between experimental and control subgroups. However, the observed changes in the vertical dimensions, Condylion/Go’–Menton and the Intercondylar distance proved insignificant. Posterior mandibular displacement of the mandible in growing rats affects the morphology of the mandible and culminates in the development of a smaller mandible at a grown age.