[Clinical analysis of colour distribution in tetracycline teeth].

Purpose: To analyze the colour range and distribution of tetracycline teeth, and the difference from normal teeth.

Methods: 142 cases with 468 anterior tetracycline teeth and 100 cases with 200 normal anterior teeth were collected. The color was measured by a computer-aided Shade-Eye NCC colorimeter, and expressed in terms of 3 coordinate values (L,a,b) of the CIE-1976-Lab color system. Chroma (Cab)and hue (h(ab) degrees)were calculated according to the value of a and b. The data were analyzed with SAS6.12 software package for description, Student's t test and Duncan test.

Results: The range of L, a, b Cab, h(ab) degrees of tetracycline teeth was 42.33-77.00, -0.6-9.6, 2.67-31.5, 5.24-31.89, 38.62 degrees-95.47 degrees, respectively. Significant difference of L value and hue (h(ab) degrees) was found between tetracycline teeth and normal teeth (P < 0.01), which indicated that tetracycline teeth were darker and redder than normal teeth. There was no difference of chroma (Cab) between tetracycline teeth and normal teeth (P > 0.05). Moreover there was significant difference of L value between canine and central incisor, and of H value (h(ab) degrees) between canine and lateral incisor in tetracycline teeth, which indicated that canine was darker and redder than incisor, and redder than lateral incisor, but there was no significant difference in chroma (Cab) among all anterior teeth and no difference in L, a, b between central incisor and lateral incisor.

Conclusions: The study showed the color distribution of tetracycline teeth was wider and more dispersive than normal teeth, and much darker and redder than normal teeth. Supported by Shanghai Leading Academic Discipline