[Comparison of clinical effect between spectrophotometric and conventional visual shade]

To study the feasibility of clinical application of the Crystaleye spectrophotometer, and compare the clinical effect of Crystaleye spectrophotometer with conventional visual shade.

63 patients in need of an anterior or a first premolar Ni-Cr porcelain-fused-to-metal crown were enrolled in this study randomly. 2 crowns (crown V and crown S) were prepared for each patient. Crown V was made via conventional visual matching by a commercial shade guide, Vitapan classical method. Crown S was made via a new computer system, Crystaleye spectrophotometer. Crystaleye spectrophotometer was also applied to measure the color of the natural teeth and crowns. The color difference values (DeltaE) between the contralateral natural tooth and each of the 2 crowns were calculated in the middle regions. A paired-samples t test was performed based on the DeltaE using SPSS13.0 software package. The color reproducibility of crown V and crown S was evaluated by patients (p) and prosthodontists (d) visually using double-blind method (Vp,Vd,Sp,Sd). The results were evaluated by Chi-square test.

There was significant difference in the mean DeltaE between crown V(3.13+/-0.80) and crown S (2.68+/-0.72)(P<0.01). Results of visual evaluation were as follows: no significant difference was found between crown Vp and crown Sp (P=0.035); significant difference was found between crown Vd and crown Sd (P<0.01) there was also significant difference between crown p and crown d(P<0.01).

According to this clinical study, the crowns fabricated based on a dedicated spectrophotometer have a better color matching compared to the ones fabricated via a conventional shade-matching method. Crystaleye spectrophotometer is proved to be a promising instrument for determining tooth color in clinic.