Comparative evaluation of displacement and stress distribution pattern during mandibular arch distalization with extra and inter-radicular mini-implants: a three-dimensional finite element study.

OBJECTIVE: To compare the initial stress distribution and displacement on mandibular dentition using extra and inter-radicular mini-implants for arch distalization, by means of finite element analysis. METHODS: For this study, two finite element models of the mandible were designed. The models consisted of periodontal ligament (PDL) and alveolar bone of all teeth until second molars. In the Case 1, bilateral extra-radicular buccal-shelf stainless steel mini-implants (10.0-mm length; 2.0-mm diameter) were placed between first and second permanent molars. In the Case 2, bilateral inter-radicular stainless steel mini-implants (10.0-mm length; 1.5-mm diameter) were placed between second premolar and first permanent molar. Power hook was attached between canine and first premolar at a fixed height of 8mm. In the two cases, 200g of distalization force was applied. ANSYS v. 12.1 software was used to analyze and compare von Mises stress and displacement in the mandibular dentition, PDL and bone. RESULTS: Higher stresses were observed in mandibular dentition with the inter-radicular implant system. The amount of von Mises stress was higher for cortical bone (85.66MPa) and cancellous bone (3.64MPa) in Case 2, in comparison to cortical bone (41.93MPa) and cancellous bone (3.43MPa) in Case 1. The amount of arch distalization was higher for mandible in Case 1 (0.028mm), in comparison to Case 2 (0.026mm). CONCLUSION: Both systems were clinically safe, but extra-radicular implants showed more effective and controlled distalization pattern, in comparison to inter-radicular implants, in Class III malocclusion treatment.

Comparative evaluation of displacement and stress distribution pattern during mandibular arch distalization with extra and inter-radicular mini-implants: a three-dimensional finite element study

ABSTRACT Objective: To compare the initial stress distribution and displacement on mandibular dentition using extra and inter-radicular mini-implants for arch distalization, by means of finite element analysis. Methods: For this study, two finite element models of the mandible were designed. The models consisted of periodontal ligament (PDL) and alveolar bone of all teeth until second molars. In the Case 1, bilateral extra-radicular buccal-shelf stainless steel mini-implants (10.0-mm length; 2.0-mm diameter) were placed between first and second permanent molars. In the Case 2, bilateral inter-radicular stainless steel mini-implants (10.0-mm length; 1.5-mm diameter) were placed between second premolar and first permanent molar. Power hook was attached between canine and first premolar at a fixed height of 8mm. In the two cases, 200g of distalization force was applied. ANSYS v. 12.1 software was used to analyze and compare von Mises stress and displacement in the mandibular dentition, PDL and bone. Results: Higher stresses were observed in mandibular dentition with the inter-radicular implant system. The amount of von Mises stress was higher for cortical bone (85.66MPa) and cancellous bone (3.64MPa) in Case 2, in comparison to cortical bone (41.93MPa) and cancellous bone (3.43MPa) in Case 1. The amount of arch distalization was higher for mandible in Case 1 (0.028mm), in comparison to Case 2 (0.026mm). Conclusion: Both systems were clinically safe, but extra-radicular implants showed more effective and controlled distalization pattern, in comparison to inter-radicular implants, in Class III malocclusion treatment.

RESUMO Objetivo: Comparar a distribuição da tensão inicial e o deslocamento na dentição inferior usando mini-implantes extra e inter-radiculares para distalização da arcada, por meio da análise de elementos finitos. Métodos: Dois modelos de elementos finitos da mandíbula foram criados, os quais consistiram de ligamento periodontal (PDL) e osso alveolar de todos os dentes até os segundos molares. No Caso 1, mini-implantes extra-radiculares de aço inoxidável (10,0 mm de comprimento; 2,0 mm de diâmetro) foram colocados bilateralmente na buccal-shelf entre o primeiro e o segundo molares permanentes. No Caso 2, mini-implantes de aço inoxidável inter-radiculares (comprimento de 10,0 mm; diâmetro de 1,5 mm) foram colocados bilateralmente entre o segundo pré-molar e o primeiro molar permanentes. Um Power hook foi preso entre o canino e o primeiro pré-molar a uma altura fixa de 8mm. Nos dois casos, foi aplicada força de distalização de 200g. O software ANSYS v. 12.1 foi usado para analisar e comparar a tensão de von Mises e o deslocamento na dentição inferior, ligamento periodontal e osso. Resultados: Maiores tensões foram observadas na dentição inferior com o sistema de implantes inter-radiculares. A quantidade de tensões de von Mises foi maior para osso cortical (85,66MPa) e osso esponjoso (3,64MPa) no Caso 2, em comparação com osso cortical (41,93MPa) e osso esponjoso (3,43MPa) no Caso 1. A quantidade de distalização da arcada inferior foi maior no Caso 1 (0,028 mm), em comparação com o Caso 2 (0,026 mm). Conclusão: Ambos os sistemas foram clinicamente seguros, mas os implantes extra-radiculares mostraram um padrão de distalização mais eficaz e controlado, em comparação com os implantes inter-radiculares, para tratamento da má oclusão de Classe III.

Comparison of prevalence of depression among medical, dental, and engineering students in Patna using Beck's Depression Inventory II: A cross-sectional study.

BACKGROUND: Depression, a multi-dimensional disorder adversely affects the interpersonal, social and occupational spheres of students' life. It is the 11th leading cause of global disease burden. AIMS AND OBJECTIVES: To assess the prevalence of depressive symptoms among various professional course students including medical, dental, and engineering students in Patna, Bihar. MATERIALS AND METHODS: The present investigation was a questionnaire-based cross-sectional descriptive study. A total of 3,100 students attending government and private medical, dental, and engineering colleges in Patna were approached during the course of this study. Students were briefed about the study and questionnaire. BDI-II (Beck's Depression Inventory-II) was administered to the students and they were instructed to fill it. Beck's scores were recorded and a descriptive analysis performed. RESULTS: 2798 students out of 3,100 responded positively to the survey by completely filling out the form. The overall response rate was 90.25%. The overall prevalence of depressive symptoms was found to be 47.78%. Of the three streams, students belonging to the engineering stream (40.28%) showed a maximum prevalence of depressive symptoms followed by dental (38.50%) and medical students (34.74%). CONCLUSION: Our study showed an alarming prevalence of depression among professional course seeking students. This multi-dimensional disorder continues to affect student's performance and professionalism, thus, extending its negative impact to the community at large. This may carry out later in their lives, thus leaving a long-term negative impact. Considering the high rate of depressive symptoms, establishing a unit or facility to identify or diagnose it at an early stage and providing psychological support to students is recommended.