IOSR Journal of Dental and Medical Sciences (IOSR-JDMS) e-ISSN: 2279-0853, p-ISSN: 2279-0861.Volume 15, Issue 12 Ver. VIII (December. 2016), PP 01-07 www.iosrjournals.org DOI: 10.9790/0853-1512080107 www.iosrjournals.org 1 | Page Influenceof Opaque with Dentine Layer Thickness to Color Matching on Metal-Ceramic Crown Sopan Sinamo, 1* Haslinda Z Tamin, 1 Harry Agusnar 2 1 Department Of Prosthodontics, Faculty Of Dentistry, University Of Sumatera Utara 2 Department Of Chemistry, Faculty Of Mathematics And Natural Sciences, University Of Sumatera Utara Abstract Background/Purpose: Color matching on metal-ceramic crown towards the natural teeth is a key for aesthetics success in prosthodontics. Dark shadow which was reflected by the metal coping often happened on the metal- ceramic crown and it causing the color that is resulted in laboratory process didn’t match with the shade guide which has been determined in the clinic, so aesthetically is less satisfying. The porcelain layer thickness is one of factors that takes a role to produce the color matching. The aim of this in vitro study was to know the effect of opaque layer thickness with dentine layer thickness to the shade guide color matching on metal-ceramic crown. Material and methods:Twenty seven of metal-ceramic samples were consisted of 0.2 and 0.3 mm opaque with 0.5, 0.7 and 1.0 mmdentine layerthickness. Shade guideVita 3D Master color 3M2 were used as a control group. The measurement of L*, a*, b* value on the sample group and shade guide was held using UV spectrophotometer. The effect of 0.2 and 0.3 mm opaque with 0.5, 0.7 and 1.0 mmdentine layerlayer thickness to the color matching was analyzed by using One-way ANOVA and LSD test. The color matching of metal-ceramic sample groups were obtained by calculating the difference of total color value (Δ E) on each sample, using the following formula:Δ E*= (Δ L* 2 + Δ a* 2 + Δ b* 2 ) 1/2 . Results:The lowest Δ E* value has the most compatible color value with shade guide color. Statistically Δ E* value was the most significant on the 0.2 mm opaque with 1.0 mm dentinelayer thickness (p=0.03). Conclusion: The 0.2 mm opaque with 1.0 mm dentine layer thickness were recommended as a guide in making the metal-ceramic crown to obtain the color matching using shade guide, so as it produce the matching color with natural teeth in oral cavity. Key words : the opaque layer thickness, dentine layer thickness, color matching,shade guide, metal-ceramic crown. I. Introduction Metal-Ceramic crown is a type of denturewhich is the most used by dentists as it has several advantages,including: moreaesthetically compared to all-metal and acrylic crown, greater strength to provide support for mastication load as it is supported by metal coping, it has good adaptation to the tooth tissue, more resistant to fracture, has almost similar thermal coefficient to the tooth, and lower cost compared to all-ceramic crown. However metal-ceramic crown has its own disadvantages, including the appearance of dark shadow which is caused by metal coping reflection, which distinguishes it from the natural tooth structure, in such way so the color produced by the laboratory often doesn’t match the shade guide color which has been determined in the clinical practice, resulting in unsatisfying aesthetics. The result of study done by Milleding P, et al(cited from Wee AG, et al 2002) in a clinical study for two years stated that from 40 metal-ceramic crowns which werecemented into the mouth, there were 61% of the color of porcelain didn’t match the adjacent natural teeth. The accuracy of determining and matching color on metal-ceramic crown is a problem for dentists and technicians in thelaboratory. 5-6 Achieving the right color in the process of making metal-ceramic crown is influenced by three factors, such as: factors of color determination in the clinic, good communication between the dentist and technician in laboratory, and factors of color matching in a laboratory. 1-3 Factors of color determining in the clinic, including color matching technic, light resource, metamerism, environmental condition, operator, and patient ’s position. 7-9 The other factor in the clinic which should also be considered for achieving correct color on the metal-ceramic crown among them is the thickness of abutment tooth preparation by a dentist which should be around 1.2 to 2.0 mm. 1-3 The factors of color matching in laboratory, including porcelain condensation technic, porcelain firing cycle, porcelain glazing cycle, porcelain type, the ratio between porcelain powder and liquid while mixing, type of metal and porcelain layer thickness. 11-16 Theporcelain layerthicknessto reach the suitable color on the metal-ceramic crown variesaccording to several studyes, however we have to consider the strength to prevent the risk of fracture while the denture is being used. Various studies about the effect of porcelain layer thickness to the color matching in the making of a metal-ceramic crown, with its various thickness, it’s in opaque layer, dentine layer or enamel layer. Jacob SH, et al(1987) evaluated the change of hue, value and chroma visually and instrumentally using spectrophotometer