Occlusal stress distribution in the human skull with permanent maxillary first molar extraction: A 3-dimensional finite element study.

INTRODUCTION: The objective of this research was to analyze the effect of orthodontic treatment with maxillary permanent first molar extraction on the occlusal stress distribution and displacement in the human skull. METHODS: A 3-dimensional finite element model was constructed on the basis of a computed tomography scan, and it was used as the pretreatment model. The software used for geometric modeling was Solid Works (Dassault Systèmes, Paris, France). For the extraction model, the maxillary permanent first molar was removed, followed by a repositioning of the anterior and posterior segments to create a space closure model. Stress distribution was evaluated under the simulation of 1000 N for occlusal forces and 400 N for masseter muscle force. RESULTS: The highest von Mises stress was observed at the zygomatic process of the temporal bone across all 3 models (25 MPa), whereas stress at the pterygomaxillary suture area was almost 50% less. However, the stress in the pterygomaxillary suture area was lowest in the extraction model (18%) and space closure (30%). Stress in the zygomatic process of the frontal bone and frontal process of the maxilla increased from pretreatment to extraction model followed by space closure model. CONCLUSIONS: The occlusal forces were transferred through maxillonasal, maxillozygomatic, and maxillopterygoid stress trajectories. The mesial displacement of the molars may weaken the role of maxillopterygoid stress trajectory while strengthening the role of maxillonasal stress trajectory.

An evaluation and comparison of myeloperoxidase enzymatic activity during initial orthodontic alignment: an in vivo study.

INTRODUCTION: Tooth movement during orthodontic treatment is possible because of mechanical force-induced inflammation and remodelling in the periodontal ligament. Variation in the inflammatory response might be anticipated with initial aligning archwires of different composition. Myloperoxidase (MPO) is an enzyme found in neutrophil granules that represents an important marker of inflammation. The aim of this study was to measure MPO enzyme activity during initial alignment with orthodontic arch wires of different alloy types. MATERIALS AND METHODS: MPO activity was determined in gingival crevicular fluid (GCF) from a sample of 60 patients divided into three groups during initial orthodontic alignment with three types of arch wire (0.016-inch superelastic (SE) NiTi; 0.016-inch heat-activated (HANT) NiTi and 0.00175-inch multistranded stainless steel). MPO activity was measured at baseline, 2 hours, 7 and 14 days after appliance activation. RESULTS: MPO activity was significantly increased in GCF at 2 hours (P < 0.01), 7 and 14 days in all groups compared to baseline. Enzymatic activity was highest in the SE NiTi group followed by HANT and multistranded stainless steel groups but with no significant difference between SE NiTi and HANT groups. CONCLUSION: SE and HANT NiTi arch wires produce an increased inflammatory response based upon MPO activity during initial levelling and alignment compared to multistranded stainless steel.

Comparative assessment of surface irregularities of enamel after bonding with different techniques followed by three composite removal methods: An atomic force microscopic study.

Background: To compare and assess the enamel surface roughness by Atomic Force Microscopy between ceramic and metal brackets after adhesive removal with 3 different methods. Methods: 90 extracted premolars were collected and divided equally into 3 groups G, Y, and R. With group G bonded with metallic brackets (using primer and Transbond XT), group Y with ceramic brackets (primer and Transbond XT), and group R with ceramic brackets (silane and Transbond XT). Each group was subdivided into 3 sub-groups (10 premolars each) based on the resin removal method as A: 12- flute tungsten carbide (TC) bur (high speed), B: 12- flute TC bur (low speed), and C: 30 flute TC bur (low speed). Surface roughness values were calculated and compared before bonding and also after adhesive removal by atomic force microscope (AFM). Measured data were analyzed using paired student t-test, ANOVA, and Tukey's tests. Results: Among the groups, group G showed increased surface roughness after debonding compared to group Y and group R, with Rq value showing a statistically significant difference (P<0.047). Whereas, within the subgroups, subgroup A (12-flute TC, high speed) with Rq showed increased surface roughness which was found to be statistically significant (P<0.042). Conclusion: None of the adhesive removal methods was capable to restore the enamel to its earlier morphology; a statistically significant increase in surface roughness parameters was reported with a high-speed 12 flute TC bur for Rq and Rt.

Coronavirus Disease 2019-Challenges Today and Tomorrow in Orthodontic Practice: A Review.

From the start of 2020, the world has witnessed the biggest health and humanitarian crisis in the modern century named coronavirus disease 2019. The rapid spread of infection created chaos and confusion across the globe. Like all other health professions, a timely and major reorganization of orthodontic services is challenging. Unlike other medical emergencies, an orthodontic emergency does not require immediate attention in most cases. With advances in the modern web-based communication systems, minor problems can be managed online in orthodontic practice. During an emergency, however, orthodontists have a moral obligation to treat and manage patients under the World Health Organization guidelines and protocol.

Evaluation of stability of three different mini-implants, based on thread shape factor and numerical analysis of stress around mini-implants with different insertion angle, with relation to en-masse retraction force.

OBJECTIVES: Assess the stability of three different mini-implants, based on thread shape factor (TSF), and evaluate stresses at the mini-implant site and surrounding cortical bone on application of retraction force, at two different insertion angles. METHODS: Mini-implants of three different diameters (M1 - Orthoimplant, 1.8mm), (M2 - Tomas, 1.6mm) and (M3 - Vector TAS, 1.4mm) and length of 8mm were used. Using scanning electronic microscopy, the mean thread depth, pitch and relationship between the two (TSF) were calculated. The mini-implants were loaded into a synthetic bone block and the pull-out strength was tested. One way ANOVA and Tukey post-hoc tests were used to compare the pull-out strength of mini-implants. P values < 0.05 were considered statistically significant. Finite element models (FEM) were constructed with insertion angulation at 90° and 60°, with retraction force of 150 g. The results were analyzed using ANSYS software. RESULTS: Statistically significant difference was found among all the three mini-implants for thread depth and pitch (< 0.001). Statistically significant higher pull-out force value was seen for Orthoimplant. The stress distribution level in mini-implant and surrounding bone was observed to be smaller for Orthoimplant. CONCLUSION: Orthoimplant mini-implants have more favorable geometric characteristics among the three types, and less stress with 90°angulation.

Evaluation of stability of three different mini-implants, based on thread shape factor and numerical analysis of stress around mini-implants with different insertion angle, with relation to en-masse retraction force

ABSTRACT Objectives: Assess the stability of three different mini-implants, based on thread shape factor (TSF), and evaluate stresses at the mini-implant site and surrounding cortical bone on application of retraction force, at two different insertion angles. Methods: Mini-implants of three different diameters (M1 - Orthoimplant, 1.8mm), (M2 - Tomas, 1.6mm) and (M3 - Vector TAS, 1.4mm) and length of 8mm were used. Using scanning electronic microscopy, the mean thread depth, pitch and relationship between the two (TSF) were calculated. The mini-implants were loaded into a synthetic bone block and the pull-out strength was tested. One way ANOVA and Tukey post-hoc tests were used to compare the pull-out strength of mini-implants. P values < 0.05 were considered statistically significant. Finite element models (FEM) were constructed with insertion angulation at 90° and 60°, with retraction force of 150 g. The results were analyzed using ANSYS software. Results: Statistically significant difference was found among all the three mini-implants for thread depth and pitch (< 0.001). Statistically significant higher pull-out force value was seen for Orthoimplant. The stress distribution level in mini-implant and surrounding bone was observed to be smaller for Orthoimplant. Conclusion: Orthoimplant mini-implants have more favorable geometric characteristics among the three types, and less stress with 90°angulation.

RESUMO Objetivos: Avaliar a estabilidade de três diferentes tipos de mini-implantes, com base no fator formato da rosca (thread shape factor, TSF), e avaliar a tensão no local de inserção e no osso cortical ao redor dos mini-implantes inseridos com dois ângulos diferentes, durante a aplicação de força para retração. Métodos: Foram usados três diferentes diâmetros de mini-implantes, sendo eles 1,8 mm (M1, ORTHO Implant), 1,6 mm (M2, Tomas) e 1,4 mm (M3, Vector TAS), todos com comprimento de 8 mm. Por meio da microscopia eletrônica de varredura, foram calculados a profundidade da rosca, o passo da rosca (distância entre os filetes da rosca) e a relação entre os dois (TSF). Para realização do teste de tração (pull-out), os mini-implantes foram inseridos em um bloco de osso sintético. Os testes ANOVA de uma via e post-hoc de Tukey foram usados para comparar as forças de resistência à tração dos mini-implantes, considerando-se estatisticamente significativos valores de p< 0,05. Modelos de elementos finitos (MEF) foram gerados com ângulos de inserção dos mini-implantes a 90° e 60°, com força de retração em 150g. Os resultados foram analisados usando-se o software ANSYS. Resultados: Diferenças estatisticamente significativas foram encontradas entre os três mini-implantes quanto à profundidade da rosca e o passo da rosca (p< 0,001). O ORTHO Implant apresentou a maior força de resistência à tração, com significância estatística. O nível de distribuição das tensões no mini-implante e no osso circundante também foi menor para o ORTHO Implant. Resultados: Entre os diferentes tipos de mini-implantes analisados, o ORTHO Implant apresentou as características geométricas mais favoráveis e a menor tensão com o ângulo de inserção de 90°.

Anterior deep bite malocclusion treated with connecticut intrusion arch: biomechanical consideration.

Most Class II division 2 malocclusion manifest a severe deep bite, the orthodontic correction of deep overbite can be achieved with several mechanisms one such mechanics is true intrusion of anterior teeth. Deep overbite correction by intrusion of anterior teeth affords a number of advantages which includes simplifying control of the vertical dimension and allowing forward rotation of mandible to aid in Class II correction. It also aid in correction of a high gingival smile line. This case report presents the patient of a 14-year-old boy with Class II division 2 subdivision malocclusion treated with connecticut intrusion arch and also highlights the biomechanical aspect of this appliance. Intrusion of anterior teeth is difficult. An appropriate, effective and clinically manageable biomechanical system is required. The treatment approach shown in this case can treat the deep overbite precisely with incisor intrusion. The article shows the versatility of Connecticut Intrusion Arch and by applying the sound biomechanical principles we can execute the planned mechanics with minimal side effects.