Shade perception ability among different dental personnel / 대한치과보철학회지

Statement of problem: Many factors influence shade determination in clinical practice and shade matching is highly affected by the viewing conditions. Purpose: This study investigated the differences in shade perception among distinct groups of dental personnel (10 prosthodontists, 10 general practitioners, 10 last-year dental students and 10 dental technicians). Material and method: Four groups of dental personnel were investigated. They were tested to eliminate color blindness. To compare shade selection ability, they were asked to match four test tabs of shades A3, B2, C2 and D4 (VITAPAN. Classical shade guide. The identification codes of the shade tabs were masked to prevent shade memory.) against another full set of VITAPAN. Classical shade guide under similar lighting conditions. Shade selections were randomly repeated five times every week and then the repeatability between dental personnel was evaluated. To compare value perception ability, they were asked to arrange randomly selected five test tabs (B1, A2, D2, C3, A4) in descending order from the brightest to the darkest. To compare hue determination ability, they were asked to divide selected eight test tabs (A2, A3, B2, B3, C2, C3, D2, D3) into four groups by manufacturer as follows: Group A-Reddish brown, Group B-Reddish yellow, Group C-Grey, Group D-Reddish grey. Results and conclusion: The obtained results were as follows: 1. For the value perception ability and hue determination ability, there was no significant difference among 4 groups: prosthodontists, general practitioners, dental students, dental technicians(P>.05). 2. For shade selection ability, the prosthodontists and dental technicians were significantly higher than dental students(P<.05). 3. The repeatability of selected shade in the dental technicians was significantly higher than that of general practitioners and dental students(P<.05). 4. The prosthodontists and dental technicians had significantly higher selection ability than dental students for shade B2(P<.05).

The influence of porcelain layer thickness and color on the final shade of ceramic restorations / 대한치과보철학회지

STATEMENT OF PROBLEM: Ceramic restorations should be made of porcelain layers of different opacity, shade, and thickness in order to provide a natural appearance. Lithium disilicate glassceramic system has superior color reproducibility, because it uses the ceramic ingot which is similar to teeth shade and uses the staining technique and layering technique. However, staining technique has a fault of discoloration. Also, porcelain is divided core and dentin layer, it is not enough to study about the influence of porcelain layer thickness and shade on the shade of ceramic restorations. PURPOSE: The purpose of this study was to evaluate the influence of porcelain layer thickness and color on the final shade of ceramic restorations. MATERIALS AND METHOD: The CIE L*a*b*(CIELAB) values of 72 assembled specimens, each consisting of 3 discs (enamel porcelain 0.2 mm/dentin porcelain - 1.2, 0.9, 0.7, 0.5 or 0.3 mm/ceramic core - 0.3, 0.5, 0.7, 0.9 or 1.2 mm, diameter is 1.0 mm) were evaluated with a spectrophotometer (Model Chromaview 300, Spectron Tech Co, Korea) for the shade A1, A2, A3 and A4. Distilled water (refractive index: 1.7) was used to attain optical contact between the layers. White, white gray, and white brown backgrounds were used to assess the influence of the background on the final shade. And the mean color difference value(delta E) was calculated. RESULTS AND CONCLUSION: The results obtained from this study were as follows. 1. There was a significant correlation between the thickness ratio of the ceramic core/dentin porcelain system and L*, a* and b* values when the total thickness of specimen combination was smaller than 1.4 mm( p<0.05). 2. The specimen which the ceramic core thickness was more than 0.7 mm had the best masking effect against background colors. 3. The mean color difference value(delta E) is smaller than 2 (delta E<2) when the ceramic core thickness was larger than 0.7 mm and the total thickness of specimen was more than 1.4 mm.

Effect on the Color Stability of Stained Porcelain due to Tooth Brushing / 대한치과보철학회지

This study is going to compare the degree of color change which occurs in the following two cases of the factors which cause the color change of extra-staining,one is during glazing by the dental technician,the other is tooth brush abrasion which makes the biggest influence on color change. To compare the degree of color change before and after glazing,a sample was made with vintage incisal porcelain No.59 OPAL(Shofu Inc,Japan),after that it was painted with three colors of porcelain stainers,then the degree of color was measured with a spectrophometer(Model Chromaview 300,Spectoron Tech Co.Korea)after it had been treated with firing only and glazing after firing. 40,000-cycle and 80,000-cycle of tooth brush abrasion test were carried out in order to simulate the brushing effect of 4 years and 8 years by using the abrasion tester.The colors were mesured before the test,and after the 40,000-cycle and 80,000-cycle operations and the surfaces were examined by SEM. The results of this study were as follows ; 1.The color change before and after glazing was not great enough to have a clinical significance but the orange color was changed more significantly statistically than the blue and light brown(P<0.05). 2.In the case of the color change of stained porcelain by tooth brushing,carrying out staining and glazing with two-times firings resulted in statically less color change than one firing only(P<0.05). 3.In the case of the difference in the stainer's color,the orange color which has higher chroma was statically more sensitive than the blue color(P<0.05). 4.In the case of the color change after the 80,000-cycle abrasion,all showed color change when there was one firing and the orange stainer showed some color change with clinical significance when firings were done two times.