Is there correlation between alveolar and systemic bone density?

OBJECTIVE: The present study assessed the correlation between maxillomandibular alveolar bone density and systemic bone mineral density (BMD). METHODS: Dual-energy X-ray absorptiometry of the anterior and posterior maxillomandibular alveolar bone, of the standard sites for the measurement of BMD (lumbar spine and femur) and the third cervical vertebra was performed on 23 middle-aged women. Periapical radiographs were also obtained, with an aluminum step-wedge as reference for the digital reading of apical bone density of the upper incisors. RESULTS: Spearman's correlations coefficients revealed that density in the apical region was correlated with that of the femoral neck (r = 0.433; p < 0.05); BMDs of the posterior regions of the mandible and maxilla were significantly correlated with that of the cervical vertebra (r = 0.554, p < 0.01 and r = 0.423, p < 0.05, respectively); and the anterior maxilla was correlated with the posterior mandible (r = 0.488, p < 0.05). CONCLUSION: Bone density of the maxillary alveolar bone was significantly correlated with that of the femoral neck. Among the bone densities of the alveolar regions, only the anterior maxilla and the posterior mandible were significantly correlated. The findings suggested that bone densitometry might be individually and locally evaluated.

OBJETIVO: avaliar a correlação entre a densidade óssea alveolar maxilomandibular e a densidade mineral óssea sistêmica. MÉTODOS: a absorciometria duoenergética por raios X do osso alveolar maxilomandibular (região anterior e posterior), dos sítios sistêmicos padrões (coluna lombar e fêmur) e da terceira vértebra cervical foi realizada em 23 mulheres de meia idade. Radiografias periapicais dos incisivos superiores também foram obtidas com uma escala de alumínio como referência para a leitura digital da densidade óssea da região apical. RESULTADOS: o teste de correlação de Spearman revelou que a densidade da região apical foi correlacionada com a do colo femoral (r = 0,433; p < 0,05), a densidade óssea da região posterior mandibular e maxilar foram significativamente correlacionadas com a DMO da vértebra cervical (r = 0,554, p < 0,01; e r = 0,423, p < 0,05) e a da região maxilar anterior foi correlacionada com a mandibular posterior (r = 0,488, p < 0,05). CONCLUSÃO: a densidade óssea alveolar maxilar foi significativamente correlacionada com a do colo femoral. Entre as densidades ósseas das regiões alveolares, somente a anterior maxilar (AMx) e posterior mandibular (PMd) foram significativamente correlacionadas. Esse achado sugere que a densitometria óssea deveria ser individual e localmente avaliada.

Análisis experimental del desgaste entre UHMWPE y acero inoxidable 316l empleados en la manufactura de prótesis coxofemorales / Experimental wear analysis of UHMWPE and stainless 316l used in the manufacturing of coxofemoral prosthesis

La causa más común de falla en prótesis coxofemorales es el aflojamiento entre los componentes que conforman el sistema, de manera específica la copa acetabular y la cabeza femoral. En esta investigación se presenta un análisis tribológico del desgaste en los componentes mencionados, ya que cuando las superficies en contacto se desgastan, la funcionalidad mecánica del sistema se compromete, debido al cambio de geometría de los mismos, dando como resultado un juego mecánico entre la copa y la cabeza. Los materiales considerados en este estudio son el polietileno de ultra elevado peso molecular (UHMWPE, por sus siglas en inglés) para la copa acetabular, y acero inoxidable 316L para la cabeza femoral. Esta combinación de materiales representa hoy en día la recomendación más usual por parte de los cirujanos para pacientes de la tercera edad. La tasa anual de desgaste se determinó de manera experimental y se cuantificó la cantidad de material desprendido durante el contacto. Se establecieron las condiciones de carga de forma analítica, considerando las que actúan sobre la cabeza femoral a lo largo del área de desgaste durante la marcha humana. Posteriormente, se realizó el análisis experimental de desgaste utilizando una máquina tribológica de configuración perno-sobre-disco (pin-on-disk), diseñada de manera específica para este estudio. Las pruebas para determinar la pérdida volumétrica de los componentes se realizaron bajo tres condiciones de operación: en seco, lubricada con agua destilada y lubricada con suero bovino. El marco experimental considerado consistió en pernos de UHMWPE sobre discos de acero inoxidable 316l simulando el desgaste equivalente a diez años de uso de la prótesis. Finalmente, de los resultados obtenidos se puede establecer que el desgaste y la cantidad de partículas desprendidas disminuyen considerablemente cuando se utiliza suero bovino como lubricante para replicar las condiciones reales de operación del sistema...

The most common cause of failure in coxofemoral prostheses is the loosening between the components of the system, namely the acetabular cup and the femoral head. In this work a tribologic analysis of wear suffered in the components is presented, due to when the surfaces in contact are worn, the mechanical function of the system is compromised as the wearing implies a change in the geometry of the components, thus in their dimensions, resulting on a looseness between the cup and the head. The materials considered in this study are Ultra High Molecular Weight Polyethylene (UHMWPE) for the cup and 316L Stainless Steel for the femoral head, which represent the surgeons choice for elderly patients. The annual wearing rate between these components was experimentally determined, as well as the amount of debris produced during contact. Firstly, the loading conditions were determined analytically considering those acting on the femoral head taking into consideration the wearing area during human walk. Secondly, the experimental analysis consisted in wearing tests using a tribology pin-on-disk machine, specifically built for this study. The tests to determine the volumetric loss of the components were performed under three different operational conditions: dry, lubricated with bovine serum and lubricated with destilated water. The experimental set up consisted on UHMWPE pins and 316L Stainless steel discs simulating the equivalent wear of ten years of usage of the prostheses. Lastly, the obtained results proved that using the bovine serum as lubricant the wear and debris of the components was significantly reduced when compared with other cases, being the dry scenario where more damage was produced. It is important to point out that the bovine serum was chosen to simulate the synovial fluid in which the system is embedded.