Influence of cavity design on quality of margin and marginal adaptation and microleakage of all-ceramic CAD/CAM inlays / 北京大学学报(医学版)

OBJECTIVE@#To investigate the influence of 135° and 90° cavity design on quality of margin and marginal adaptation and microleakage of all-ceramic computer aided design/computer aided manufacturing (CAD/CAM) inlays.@*METHODS@#One hundred extracted human molars were prepared by criteria of buccal occlusal (BO) inlay. On the buccal, the mesial margin was prepared as 135° bevel while the distal margin was prepared as butt-joint. All-ceramic restorations were made in the Sirona CEREC AC CAD/CAM system with VitaBlocs Mark Ⅱ, Upcera UP.CAD, IPS e.max CAD, Upcera Hyramic and Lava Ultimate. The gaps between each inlay's mesial margin-abutment and distal margin-abutment were recorded under an optical microscope. Each inlay was adhered to the abutment and aged by thermal cycling for 10 000 times. Each specimen was cut into 3 slices after staining. Dye penetration was evaluated under an optical microscope for mesial and distal margins.@*RESULTS@#Mean marginal integrity rate, mean marginal gap value and mean depth of microleakage of 135° margin of Group Upcera Hyramic and Lava Ultimate were significantly better than those of Group VitaBlocs Mark Ⅱ, Upcera UP.CAD and IPS e.max CAD(P < 0.05). Mean marginal gap value, mean depth of microleakage and scale of mean depth of microleakage of 90° margin of Group Upcera Hyramic and Lava Ultimate were significantly better than those of Group Upcera UP.CAD and IPS e.max CAD (P < 0.05) while mean marginal integrity rate was not significantly different (P>0.05). Mean marginal integrity rate of 90° margin was significantly better than that of 135° margin in each group (P < 0.05) while mean depth of microleakage between different margins was not significantly different in each group (P>0.05). Mean marginal gap value of 90° margin of Group VitaBlocs Mark Ⅱ and IPS e.max CAD was significantly better than that of 135° margin (P < 0.05) while there was not significant difference in other 3 groups between 90° and 135° margin (P>0.05). Scale of mean depth of microleakage of 135° margin of Group Upcera Hyramic and Lava Ultimate was significant better than that of 90° margin (P < 0.05) while there was not significantly different in other 3 groups between 90° and 135° margin (P>0.05).@*CONCLUSION@#The mesial and distal margins of abutement of all-ceramic inlay should be prepared as butt-joint.

Preliminary evaluation of a virtual reality dental simulation system on training of caries identification ability / 北京大学学报(医学版)

OBJECTIVE@#To develop a software based on "UniDental" system which is a virtual reality dental simulation system and applied to undergraduate majoring in stomatology to improve the ability of identifying caries.@*METHODS@#A software was developed applying to identify virtual dental caries based on UniDental system. In the software, a virtual dental caries model was designed and carious tissue was separated to 3 layers by the depth. The stiffness was the same within each layer which was increasing gradually layer by layer. The roughness was also the same within each layer which was decreasing gradually layer by layer. Sixty-four participants in pre-clinical stage of the class of 2014 majoring in stomatology from Peking University School of Stomatology were trained with the software. During the training, the students should probe on the virtual dental carious tissue layer by layer and feel the difference of vertical stiffness and horizontal roughness of each layer by using a handpiece with realistic force feedback. After training, a questionnaire survey was conducted to evaluate the software including a score of 1-5 for haptic fidelity of stiffness and roughness and their relevant gradient and benefit of improving the ability of identifying caries, choosing the preferred training method. The data were statistically analyzed using Kruskal-Wallis test.@*RESULTS@#The median of subjective evaluation scores of the proposed metrics were all "4", demonstrating that the software operated above medium fidelity. The stiffness scores of all 3 layers were statistically significant (P < 0.05) on the stiffness gradient score. The roughness scores of the 1st and 2nd layers were statistically significant (P < 0.05) on the roughness gradient score. The training was helpful to improve the ability of identifying caries (median was 4). The scores of all 3 layers stiffness and relevant gradient were statistically significant (P < 0.05) on the score of benefit of improving the ability of identifying caries. 90.4% of the participants preferred the traditional extracted teeth training method.@*CONCLUSION@#The virtual reality dental simulation system was helpful to improve students' ability of identifying caries. It couldn't replace the traditional extracted teeth training method by now, it should be used as a supplement to the traditional training method.