Comparative evaluation of marginal and internal fit of anatomic and nonanatomic metal frameworks fabricated by selective laser sintering

For teeth restoring single metal-ceramic crowns were the gold-standard for many years. Selective laser sintering is a new technology which can provide accurate complex-shaped frameworks for dental restorations, layer-by-layer, according to a three-dimensional computer model, using metal powder. An important factor for long term success of fixed prostheses is the marginal and internal adaptation. The aim of the study was to evaluate the effect of framework design and design of tooth preparation on marginal and internal fit of laser-sintered frameworks. Two maxillary first molars where prepared with two different kind of marginal limits. Two different framework designs were constructed for each: model 1 – a coping with a constant framework thickness of 0.6 mm and model 2 an anatomically modified shaped cusp supporting framework with a constant veneering thickness. The mean marginal gap values were between 37 and 95 μm, the means for the axial region were between 47 and 70 μm and for the occlusal region between 67 and 147 μm. Copings produced by selective laser sintering using CAD/CAM technologies demonstrate acceptable marginal and internal fit in the range of 47 to 120 μm, with better results in case of anatomically-reduced frameworks. Key-Words: rapid prototyping, selective laser sintering, marginal and internal fit, CAD/CAM system, cobaltchromium alloy, metal-ceramic crowns