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UBC Theses and Dissertations

The effect of crown cementation on the marginal fit using a micro-CT measurement technique Gebril, Mohamed


Objectives: To study the effect of cementation on the marginal gap of lithium disilicate (LDS) crowns made with digital impression and manufacturing (DD), digital impression and traditional pressed manufacturing (DP) and traditional impression and manufacturing (TP). Methods: Ivorine typodont tooth #15 was prepared for an all-ceramic crown. The prepared tooth was scanned, and 45 dies were produced and used for fabricating 45 LDS crowns using three methods: DD, DP, and TP. Micro-CT was utilized to evaluate the 2D marginal gap before adjustment, after adjustment and after cementation. RelyX-Ultimate resin cement was used to cement the crowns on each of the 45 dies with 20 N application force using a universal material testing machine. The 2D vertical marginal gap (MG) evaluations were made at 20 designated positions along the crown margins. The results were analyzed using a linear mixed effect model with the interaction method x cementation as fixed effect, and crown as a random effect, as well as post hoc analysis (CI=95%). Results: Clinical adjustments of unacceptable crowns (4 from the TP and 2 from the DP) which showed at least 5 measurement points of MG of more than 120 μm resulted in reduction of the marginal gap to an acceptable level. Cementation resulted in an average increase in the marginal gap of 20 μm (95 % CI= 22-18), irrespective of the method of fabrication. All crowns had clinically acceptable crown margins, irrespective of the method of fabrication after cementation. Conclusion: Clinical adjustments to intaglio surface of crowns reduced MG, while cementation increased MG regardless of the method of fabrication. The DD group did not require any clinical adjustment prior to cementation. Only two crowns of the DP group and four crowns of the TP group required adjustment prior to cementation

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