Optimizing a 3d endodontic stent for adhesive fiber post removal: in vitro experimental study
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Background: The aim of this study is to optimize the variables involved in the design and fabrication of 3D stent for fiber post removal to enhance it accuracy, efficacy and safety. Material and methods: 3D stents were designed with 3D Slicer and Rhino software utilizing NextDent™ Model 2.0 or NextDent™ Surgical Guide (SG) materials. Four experiments were performed to determine the effect of 3D software and fabrication materials on hole size accuracy, hole shape characterization, enlargement margin, and wire deviation/deflection. Results: 3D stents printed with NextDent™ Surgical guide (SG) fabrication material have larger hole sizes than the origin pre-determined size by +0.04-0.07 mm, while those made with NextDent™ Model 2.0 are smaller by -0.03–0.00 mm, regardless of the software used to design the stent. NextDent™ Model 2.0 has more staircase effects than NextDent™ SG. The required enlargement margin to allow a stainless steel round wire to fit into a matched predetermined hole is +0.05-0.1mm. The deviation distance in 3D stents designed by 3D Slicer and printed by NextDent™ Model 2.0 decreased with stent thickness from 4mm to 8 or 12mm, regardless of hole size. Conclusion: No matter the software or material used to design and print stents, the actual hole size is always different than the pre-determined hole. Always enlarge the hole radius by 0.5- 1.0mm to allow a wire (or bur) to fit. Increasing stent height from 4mm to 8 or 12mm reduces wire deviation.