International Journal of Computerized Dentistry, Pre-Print
Xu, Shu-Xi / Tong, Xue-Lu / Tan, Fa-Bing / Yu, Na / Ma, Chao-Yi
Seite 1 – 29
Aim: To evaluate the effect of cement gap and drill offset on the marginal and internal fit discrepancies of crowns designed with different tooth preparations.
Materials and methods: Five tooth preparations were constructed, and crowns with different cement gaps and drill offset were obtained. Then, best-fit-alignment was performed on the crowns with the corresponding tooth preparations, and the fit discrepancies were expressed by the color-code difference images and root mean square (RMS) values. The RMS values of each group were analyzed by the rank-based Scheirer-Ray-Hare test (α=0.05).
Result: The color segments in the sharp line angles area of the Sharp line angles group changed significantly before and after the drill offset. The cement gap had a significant effect on the marginal, internal, or overall fit discrepancies of the five design groups (P<0.001), while the drill offset had a significant effect on the marginal fit discrepancies of the Shoulder-lip group and the internal or overall fit discrepancies of the Sharp line angles group (P<0.001). Additionally, the interaction effect between cement gap and drill offset was significant for the marginal fit discrepancies of the Shoulder-lip group and the internal or overall fit discrepancies of the Sharp line angles group (P<0.01).
Conclusion: The cement gap and drill offset had a significant adverse effect on the marginal or internal fit discrepancies in the crowns designed with the shoulder-lip and sharp line angles designs. Designs of tooth preparation with intense curvature changes such as shoulder-lip and sharp line angles should be avoided clinically.