{'fraction_non_alphanumeric': 0.03669190448456611, 'fraction_numerical': 0.009318578916715201, 'mean_word_length': 4.804054054054054, 'pattern_counts': {'":': 0, '<': 1, '<?xml version=': 0, '>': 1, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Color management of the cervical region using different framework materials.

BACKGROUND
  Color-matching of the cervical area between natural teeth and different crown prostheses is a common clinical problem.


PURPOSE
  The purpose of this study was to compare the color of the cervical region of five commercially available crown systems to an extracted natural tooth and to each other.


MATERIALS AND METHODS
  The color of the cervical region of an extracted maxillary incisor was measured by means of a colorimeter (ShadeVision, X-Rite). Fifty master dies were fabricated, divided into five groups (N=10) according to the framework material; group 1: high-noble gold alloy, group 2: same as group 1 but treated with gold paste material, group 3: precious reinforced alloy, group 4: white zirconium oxide substructure (Lava 3M ESPE), and group 5: shaded zirconium oxide (Lava). A direct comparison of L*, a*, and b* parameters was accomplished between the control natural tooth and the five crown systems, and the mean color differences (ΔE) was calculated. The data were statistically analyzed with one-way analysis of variance and post hoc multiple comparison (α=0.05).


RESULTS
  Compared to the natural tooth, the mean color differences (ΔE) values were clinically unacceptable for all groups (ΔE > 3.7). The detected color differences, among different porcelain systems, were not visually perceptible (ΔE < 3.7).


CONCLUSIONS
  Within the limitations of this study, the cervical color of an extracted natural tooth could not be duplicated using different crowns systems.


CLINICAL SIGNIFICANCE
Color-matching of the cervical region of different crown systems with natural tooth remains a difficult task.