Experimental Study The Effect Of Different Luting Space Settings On The Fits Of Cerec Blocs All-Ceramic Crowns

Objective To study the effect of different luting space settings on marginal and internal fits of Cerec Blocs all-ceramic crowns in InLab MC XL system, and provide an experimental basis for their clinical application.Methods A right maxillary first molar in the standard model was prepared and subsequently replicated into silicone rubber negative mold. Respectively, irrigated thirty preparations of all-ceramic plaster of esthetic-base gold and die stone. Thirty all-ceramic plasters of esthetic-base gold were used for optical impression of inEos scanning unit in InLab MC XL system, and then obtained thirty three-dimensional digital images. Thirty of them were randomly divided into 6 groups, and luting spaces were set to 0μm (A group), 10μm (B group), 20μm (C group), 30μm (D group), 40μm (E group) and 50μm (F group) by V2.40 R1800 computer software. The experiment obtained thirty all-ceramic crowns and each group had five ones, according to six groups luting space settings by Digital Control Cutting equipment. In addition, thirty die stones were prepared for bonding of the Cerec Blocs all-ceramic crowns. After being bonded, embedded and slitted, these specimens were scanned by the OLYMPUS SZ51 stereo microscope. Finally, the data were statistically analyzed by SAS 9.1 software.Results With image J professional determination software, these specimens were measured the marginal and internal fits. Experimental results were that the marginal fits of bucco-lingually and mesio-distally were higher than 120μm in A, B groups, and that the marginal fits of lingual side and mesio-distally were lower than 30μm in F group, and that the fits of occlusal surface were higher than 300μm in A, B, E, F groups. The marginal fits of bucco-lingually and mesio-distally were among 30μm~120μm, and the internal fits of both shoulders and axes of bucco-lingually and mesio-distally, buccal and lingual tip, axial occlusal line angles of mesio-distally, occlusal surface were among 30μm~ 300μm in C, D groups, so the marginal and internal fits of C, D groups in the clinically acceptable range. Moreover, there were statistically significant differences(P<0.05)between C group and D group in the marginal fits of bucco-lingually and mesio-distally, and the marginal fits of D group were lower than C group. There were statistically significant differences(P<0.05)between buccal and lingual, between mesial and distal in the marginal fits of C group. There was statistically significant difference(P<0.05)between buccal and lingual, while no significant difference(P>0.05)was found between mesial and distal in the marginal fits of D group. The fits of occlusal surface were both higher than other parts of the internal fits in C, D groups. There was significant difference (P<0.05) between buccal tip and lingual tip, and the internal fits of buccal tip were higher than lingual tip in C, D groups.Conclusions Under the conditions of this study, all-ceramic crowns can obtain the marginal and internal fits which meet clinical requirements when luting space settings were 20μm and 30μm. That luting space settings were 30μm was better than that 20μm in the marginal fits. The internal fits were not uniform in different parts of the all-ceramic crowns, and the fits of occlusal surface were worse than other parts of the internal fits, and the fits of lingual tip were better than buccal tip in 20μm and 30μm.