The use of the Finite Element Method (FE) is an appropriate way to study occlusal forces and tooth movement. The purpose of this study was to evaluate the effects of different occlusal contact patterns on tooth displacement in an adult dentition using a three-dimensional FE model of a human maxilla and mandible. Initially, images of a computerized tomography scan were redrawn in a computer program (CATIA) followed by the FE mesh construction. The MSC/Patran software was used to develop the FE mesh comprising 520,445 elements and 106,633 nodes. The MSC/Nastran program was utilized as pre and post-processor for all mathematical calculations necessary to evaluate dental and mandibular biomechanics. Four occlusal patterns were tested: FEM 1 - standard occlusal contacts; FEM 2 - removal of mesial marginal and mesial tripoidism contacts; FEM 3 - removal of distal marginal and distal tripoidism contacts; FEM 4 - similar to FEM 3 with added contacts between upper and lower incisors. Small changes in the standard distribution of occlusal contacts resulted in an imbalance of occlusal forces and changes in dental positioning. All simulations tested showed mesial displacement of posterior teeth. The most significant changes were registered in the model presenting unstable occlusal contacts when the anterior teeth were in occlusion (FEM 4). These findings may explain mandibular incisors crowding and maxillary incisors flaring as a result of small variations in dental contacts.

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Purpose -The purpose of this paper is to evaluate the performance of cutting fluid applied by minimum quantity technique when milling AISI 4140 steel with TiAlN coated cemented carbide inserts. Design/methodology/approach -The vegetable oil based cutting fluid evaluated was applied through a nozzle at the centre of the tool holder under vaporized conditions with a flow rate between 0 (dry cutting) and 200 ml/h, at 50 ml/h increments. Tool wear (based on maximum flank wear, VB max ), surface roughness parameters (R a and R t ) and burr formation (length of burr, h) were recorded and evaluated. Scanning electron microscope images and energy dispersive X-ray analysis of the worn tools show adhesion as the dominant wear mechanism. Findings -Encouraging tool performance was recorded when milling AISI 4140 steel due to improved lubrication and cooling at the cutting interfaces. Increase in cutting fluid flow rate improves tool life with gradual reduction of the surface roughness parameters and negligible influence on the burr length generated. Practical implications -Results can be immediately applied on the shop floor. Originality/value -The results show the improvement in tool wear after increase of the flow rate of the cutting fluid, applied by minimum quantity technique.