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.

Vulvar Elephantiasis of Filarial Origin: A Case Report.

Lymphedema is accumulation of lymph in the soft tissue due to obstruction of lymphatics. Lymphedema can be primary or secondary. Filariasis caused by Wuchereria bancrofti and Brugia malayi is one of the secondary causes of lymphedema. Longstanding lymphedema can lead to ‘elephantiasis’. Elephantiasis of female genitalia is extremely rare. We present one such case of a 40-year-old lady having giant vulvar elephantiasis of filarial origin managed successfully by surgery (vulvectomy with vulvoplasty).

Photographic Implication And Basis of Camera Lens.

Our patients expect us to show them what we do, but just making a click is by far not enough to make good intra oral pictures. Being good in photography is an absolute necessity in today’s dentistry. Photographs are not used for diagnosis only but also for communication and medicolegal reasons.This article takes a full and clear review of selection of camera, lenses and camera setting for intra and extra oral shots.We know that good quality accurate clinical photography can easily be obtained using correct focusing technique, proper focal length of lens and aperture size. So aim of his article is to take the readers to the basics of camera lens.

Spectrum of renal disease in malaria.

Between January 2000 and December 2001, renal involvement in 81 cases of malaria was studied. Their age ranged between 05 and 66 (mean 35.5) years. Distribution of malarial parasite was P falciparum (75), mixed infection (4) and P vivax (2). The evidence of clinical renal disease in the form of acute renal failure, electrolyte abnormality, abnormal urinary sediment and increased urinary protein excretion (>500 mg/24 hours) was found in 100%, 91.3%, 46.9% and 18.5% respectively. Probable aetiopathogenesis of acute renal failure (ARF) was multifactorial. Volume depletion (72.8%) was the dominant cause of ARF in these patients. In addition, hyperbilirubinaemia, intravascular haemolysis and sepsis were responsible for ARF in 64.2%, 70.3% and 25.9% cases respectively. All the patients were managed with anti-malarial drugs and dialysis support was needed in 35 patients (43.2%). Prognosis of malarial acute renal failure is favourable with mortality rate of 18.5%. Multi-organ failure was the commonest cause (33.3%) of death.