[Detection of marginal leakage of Class V restorations in vitro by micro-CT].

Objective To evaluate the reliability and superiority of micro-CT in marginal leakage assessment of Class V restorations. Methods Class V preparations with gingival margins in dentin and occlusal in enamel were made in sixteen extracted non-carious human molars and restored with dental bonding agents and composite resin.All teeth were then immersed in 50％ ammonia-silver nitrate solution for 12 hours,followed by developing solution for 8 hours. Each restoration was scanned by a micro-CT and silver leakage was measured and three-dimensional image of the silver leakage alone cavity wall were reconstructed. Afterward, all restorations were sectioned and examined for leakage depth using a microscope. The silver leakage depth of each restoration obtained by micro-CT and microscope were compared for equivalency. Results The silver leakage depths in gingival wall obtained with micro-CT (0.78 mm) and microscope (0.74 mm) showed no significant difference (P ＞ 0.05 ),while the judgment of leakage depths in occlusal wall in micro-CT image (0.40 mm) was affected by adjacent enamel structure,giving less leakage depths compared to microscope (0.72 mm) (P ＜ 0.01 ).The three-dimensional shapes of the microleakages displayed clearly by micro-CT alone wall of Class V restorations were multiform and some leakages showed channels on their way to spreading.Conclusions Micro-CT can detect precisely the silver leakage in the dentin wall of a restoration and display its three-dimensional shape fully. Enamel structure affects the detection of the silver leakage next to it. Key words: Cone-beam computed tomography; Dental prosthesis; Composite resins; Leakage