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SUMMARY: Recent technical and technological advancements in orthognathic surgery concepts, intricate in the diagnosis and treatment planning for corrections of dento-facial deformities, have achieved stable oro-dental functional occlusion and facial esthetic harmony. Undeniably, this can be attributed to the integration of modern, innovative and advanced facial analysis and computer-aided imaging exams into well-orchestrated and executed orthodontic and surgical methods. Three-Dimensional (3-D) virtual planning is a fine example. Today, the acquisition of 3-D images of a patient's craniofacial complex via cone-beam computed tomography (CBCT), supported by software tools allowing the construction of 3-D dynamic and interactive visual models, eliminates the uncertainty experienced with two-dimensional images. Thereby allowing for a more accurate or predictable treatment plan and efficient surgery, especially for patients with complex dento-facial deformities. This review article aims to describe the current benefits as well as shortcomings of 3-D virtual planning via discussing examples and illustrations from orthognathic procedures, attained from the reported English and Spanish literature during the last 10 years. It is designed to deliver updated and practical guidelines for dental practitioners and specialists (particularly, oral and maxillofacial), as well as researchers involved in 3-D virtual approaches as an alternative to conventional/traditional surgical planning; thereby validating its superiority or benefits in terms of outcome prediction for soft and hard tissues, operational timeand cost-effectiveness; for its integration in day-to-day practise.

RESUMEN: Los recientes avances técnicos y tecnológicos en los conceptos de la cirugía ortognática, involucrados en la planificación del diagnóstico y tratamiento para la corrección de deformidades dento-faciales han sido notablemente considerables en lograr una oclusión oro-dental funcional y una estética facial armónica. Innegablemente, esto se puede atribuir a la integración de análisis faciales avanzados, modernos e innovadores y exámenes de imágenes asistidos por computadora a métodos ortodonticos y quirúrgicos bien orquestados y ejecutados. La planificación virtual tri-dimensional (3-D) es un buen ejemplo. Hoy, la adquisición de imágenes 3-D del complejo cranio-facial de pacientes vía tomografía computarizada cone beam (TCCB), apoyada por herramientas computacionales, permite la construcción de modelos visuales 3-D dinámicos e interactivos, eliminando la incertidumbre experimentada con las imágenes bi-dimensionales. Permitiendo, de este modo, un plan de tratamiento más preciso o predecible y una cirugía más eficaz, especialmente para pacientes con deformaciones dento-faciales complejas. Este artículo de revisión tiene como objetivo el describir los actuales beneficios, así como las limitaciones de la planificación virtual a través de la discusión de ejemplos de procedimientos ortognáticos, obtenidos de la literatura reportada en inglés y español durante los últimos 10 años. Fue diseñado para entregar una actualización resumida y una guía práctica para los practicantes y especialistas interesados (particularmente, oro y maxilofaciales), explícitamente, así como a los investigadores involucrados en aproximaciones 3-D como una alternativa a la planificación quirúrgica convencional/tradicional; validando así su superioridad o beneficios en términos de predicción de resultados para tejidos blandos y duros, efectividad en tiempo operacional y costos; para su integración en la práctica cotidiana.

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Patients with considerable maxillomandibular anteroposterior discrepancies and maxillary hypoplasia require corrective treatment through orthognathic surgery. However, in the treatment of severe maxillary retrognathism, it is necessary to reconstruct areas of bone deficiency through grafting techniques in addition to maxillary advancement using only the Le Fort I osteotomy. Treatment in these patients is more challenging and requires high surgical predictability. Alloplastic materials often have been used for the reconstruction of poor bone contours. Ultrahigh-molecular-weight polyethylene (UHMWPE) is currently an excellent filler material for poor bone regions and is a good substitute for autografts and other alloplastic materials for its unique properties, including high biocompatibility. Insertion of this material in the fixation system customized for virtually planned orthognathic surgeries is an innovative technique. This report describes the insertion of UHMWPE into custom-made titanium miniplates manufactured by computer-aided design and computer-aided manufacturing technology for orthognathic surgery consisting of maxillary advancement and mandibular retrusion to treat a patient with Crouzon syndrome, Class III malocclusion, and severe maxillary retrognathism.

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A systematic review of the advantages and disadvantages of piezoelectric surgery in comparison with conventional saws for sagittal split osteotomy (SSO) was performed. Relevant studies published in the last 10 years were identified through a search of the PubMed/MEDLINE, Science Direct, and Embase databases and assessed against predetermined eligibility criteria. The initial search resulted in 1736 articles. After applying the inclusion and exclusion criteria, 12 articles remained. A total of 799 patients with an average age of 27.5 years underwent SSO performed using a saw or ultrasonic device. Results showed that it took longer to perform the osteotomies using an ultrasonic device than using a conventional saw. At ≥6 months of follow-up, neurosensory disturbance was seen in 4.7% of patients who underwent piezoelectric surgery versus 61.6% of patients who underwent surgery in which a conventional saw was used. It was found that the use of piezoelectric surgery in SSO leads to the best outcome regarding neurosensory disturbance when compared to conventional saws (P=0.04) at ≥6 months of follow-up. Further studies are required for the evaluation of the other clinical parameters assessed.

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The aim of this study was to compare the mechanical stress over hemimandible substrate and hardware after sagittal split ramus osteotomy (SSRO) fixed with five different techniques using three-dimensional (3D) finite element analysis. A 3D finite element model of a hemimandible was created and a 5mm advancement SSRO was simulated on a computer model. The model was fixed with five different techniques: 3 linear 60° screw arrangement; 3 linear 90° screw arrangement; 3 inverted L screw arrangement; 1 conventional miniplate; and 1 locking miniplate with four monocortical screws. Load was applied until 3mm displacement was reached and the results were compared with previous mechanical and photoelastic tests, thus analysing the mechanical stresses developed in the proximity of miniplates and screws and within the fixation system itself. The maximum principal stress values demonstrate a lower mechanical stress rate in bone and in the fixation system with the inverted L arrangement, followed by the linear 90° and linear 60° arrangements. The locking miniplate/screw system presented lower maximum principal stress and better stress distribution compared with the conventional system. Under the conditions tested, the reversed L arrangement provided the most favourable stress dissipation behaviour.

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Miniplate and screw fixation has been widely used in bilateral sagittal split osteotomy, but some issues remain unclear concerning its lack of rigidity when compared to Spiessl's bicortical technique. This paper demonstrates the hybrid fixation technique in a case report. A 34-year-old female patient underwent a double jaw surgery with counter-clockwise rotation of the mandible fixed using the hybrid fixation technique. The patient evolved well in the postoperative period and is still under follow up after 14 months, reporting satisfaction with the results and no significant deviation from the treatment plan up to now. No damage to tooth roots was done, maxillomandibular range of motion was within normality and regression of the inferior alveolar nerve paresthesia was observed bilaterally. The hybrid mandibular fixation is clearly visible in the panoramic and cephalometric control radiographs. It seems that the hybrid fixation can sum the advantages of both monocortical and bicortical techniques in lower jaw advancement, increasing fixation stability without significant damage to the mandibular articulation and the inferior alveolar nerve. A statistical investigation seems necessary to prove its efficacy.

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Miniplate and screw fixation has been widely used in bilateral sagittal split osteotomy, but some issues remain unclear concerning its lack of rigidity when compared to Spiessl's bicortical technique. This paper demonstrates the hybrid fixation technique in a case report. A 34-year-old female patient underwent a double jaw surgery with counter-clockwise rotation of the mandible fixed using the hybrid fixation technique. The patient evolved well in the postoperative period and is still under follow up after 14 months, reporting satisfaction with the results and no significant deviation from the treatment plan up to now. No damage to tooth roots was done, maxillomandibular range of motion was within normality and regression of the inferior alveolar nerve paresthesia was observed bilaterally. The hybrid mandibular fixation is clearly visible in the panoramic and cephalometric control radiographs. It seems that the hybrid fixation can sum the advantages of both monocortical and bicortical techniques in lower jaw advancement, increasing fixation stability without significant damage to the mandibular articulation and the inferior alveolar nerve. A statistical investigation seems necessary to prove its efficacy.

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PURPOSE: The aim of this in vitro study was to assess the biomechanical stability of 9 different osteosynthesis methods after sagittal split ramus osteotomy by simulating the masticatory forces and using a 3-point biomechanical test method. MATERIALS AND METHODS: Forty-five polyurethane hemimandibles with bone-like consistency were randomly assigned to 9 groups (n = 5) and subjected to sagittal split ramus osteotomy. After 4-mm advancement of the distal segment, the bone segments were fixed by different osteosynthesis methods using 2.0-mm miniplate/screw systems: group A, one 4-hole conventional straight miniplate; group B, one 4-hole locking straight miniplate; group C, one 4-hole conventional miniplate and one bicortical screw; group D, one 4-hole locking miniplate and 1 bicortical screw; group E, one 6-hole conventional straight miniplate; group F, one 6-hole locking straight miniplate; group G: two 4-hole conventional straight miniplates; group H, two 4-hole locking straight miniplates; and group I, 3 bicortical screws in an inverted-L pattern. All models were mounted on a base especially constructed for this purpose. Using a 3-point biomechanical test model, the hemimandibles were loaded in compressive strength in an Instron machine (Norwood, MA) until a 3-mm displacement occurred between segments vertically or horizontally. Data were analyzed by analysis of variance and Tukey test (alpha = 1%). RESULTS: The multiparametric comparison of the groups showed a statistically significant difference (P < .01) between groups that used 2 miniplates (groups G and H), 1 miniplate and 1 bicortical screw (groups C and D), and only bicortical screws (group I) compared with groups that used only 1 miniplate with 2 screws per segment (groups A and B) and 3 screws per segment (groups E and F). CONCLUSION: The placement of 2.0-mm-diameter bicortical screws in the retromolar region, associated or not with conventional and locking miniplates with monocortical screws, promoted a better stabilization of bone segments. Locking miniplates presented a better performance in bone fixation in all groups.

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