Influence of bone defect position and span in 3-point bending tests: experimental and finite element analysis

Abstract: Three-point bending test is the most common mechanical test used for quantifying the biomechanical quality of bone tissue and bone healing in small animals. However, there is a lack of standardization for evaluation of bone repair by cortical perforation. The aim of this study was to determine the influence of bone defect position in the proximal metaphysis of rat tibias during load application and different span configuration on the three-point bending test outcomes. Cortical defects with 1.6 mm diameter were created at a standardized location on the medial surface of 60 tibias of male Wistar rats. The animals were euthanized 7 days after surgery. Five specimens were used to create 3D models for finite element analysis using high-resolution micro-CT images. Two spans (6 and 10mm) and three positions of the bone defect in relation to the load application (upward, frontal and downward) were evaluated experimentally (n = 10) and in finite element analysis (n = 5). Maximum load (N) and stiffness (N/mm) were statistically analyzed with 2-way ANOVA and Tukey test (α = 0.05). The results demonstrated that span and orientation of the bone defect significantly influenced the fracture pattern, stress distribution and force versus displacement relation. Therefore, reliable outcome can be achieved creating the bone defect at 8 mm from the extremity of the proximal epiphysis; placing a 10 mm distance span and downward facing defect position to allow a better distribution of stress and more fracture patterns that reached the bone defect target area with less intra-group variability.

The effect of a 3% hydroxyapatite paste prophylaxis after different root-scaling procedures in periodontics / Efeito da profilaxia com pasta de hidroxiapatita 3% após diferentes procedimentos de raspagem radicular na periodontia

Abstract Introduction Root-scaling procedures on the root surface show to increase root surface roughness during instrumentation. The use of a prophylactic paste reduces the roughness. Objetive This study evaluated the influence of prophylaxis paste on the surface roughness of root dentin after hand instruments (HI), ultrasonic scalers (US) and rotational instruments (RI) were applied to root surfaces. Material and method Fifty bovine roots were prepared and randomly divided into 10 groups (n=5) in which instrumentation with HI, US, or RI was carried out with or without prophylaxis using either conventional or 3% hydroxyapatite paste; additionally, a control group without treatment was included. The Ra and Rz roughness values were measured using a perfilometer. The morphological aspects of the root surfaces were analysed qualitatively by scanning electron microscopy (SEM). Data were analysed using two-way ANOVA followed by Tukey's test (α = 0.05). Result The scaling method and the prophylaxis procedure significantly influenced (p < 0.05) root surface roughness. Treatment with US and prophylaxis with 3% hydroxyapatite paste resulted in lower values ​​of Ra (0.14 µm ± 0.02 µm) and Rz (0.89 µm ± 0.18 µm) compared to the other groups. SEM analysis showed smoother and more homogeneous surfaces in the groups with prophylaxis compared to the groups without prophylaxis. There were no substantial differences between the results of applying different pastes. Conclusion The prophylaxis procedure performed with the experimental paste containing 3% hydroxyapatite reduced the roughness of root surfaces treated with HI, US and RI at the same level as the conventional prophylactic paste.

Resumo Introdução Procedimentos de raspagem na superfície radicular aumentam a rugosidade superficial durante a instrumentação. O uso de pasta profilática pode reduzir a rugosidade. Objetivo Este estudo avaliou a influência da profilaxia com pasta na rugosidade superficial da dentina radicular após instrumentação manual (IH), ultrassom (US) e instrumentos rotatórios (IR) aplicados em superfícies radiculares. Material e método Cinquenta raízes bovinas foram preparadas e divididas aleatoriamente em 10 grupos (n = 5) nos quais a instrumentação com HI, US ou RI foi realizada com ou sem profilaxia usando pasta convencional ou hidroxiapatita a 3%; adicionalmente, um grupo controle sem tratamento foi incluído. As rugosidades de Ra e Rz foram medidas por um perfilômetro. Os aspectos morfológicos das superfícies radiculares foram analisados ​​qualitativamente por microscopia eletrônica de varredura (MEV). Os dados foram analisados ​​por meio de ANOVA de dois fatores, seguido pelo teste de Tukey (α = 0,05). Resultado O método de raspagem e o procedimento de profilaxia influenciaram significativamente (p <0,05) a rugosidade da superfície radicular. O tratamento com US e a profilaxia com pasta de hidroxiapatita ao 3% resultaram em menores valores de Ra (0,14 µm ± 0,02 µm) e Rz (0,89 µm ± 0,18 µm) em relação aos demais grupos. A análise por MEV mostrou superfícies mais lisas e mais homogêneas nos grupos com profilaxia em comparação aos grupos sem profilaxia. Não houve diferenças substanciais entre os resultados da aplicação das diferentes pastas. Conclusão O procedimento de profilaxia realizado com a pasta experimental contendo 3% de hidroxiapatita reduziu a rugosidade das superfícies radiculares tratadas com HI, US e RI no mesmo nível da pasta profilática convencional.