ISPUB.COM The Internet Journal of Dental Science Volume 6 Number 2 1 of 6 The effect of different metal surface grindings in the metal- ceramic bond strength B Bagis, D Oztas Citation B Bagis, D Oztas. The effect of different metal surface grindings in the metal-ceramic bond strength. The Internet Journal of Dental Science. 2008 Volume 6 Number 2. Abstract Purpose: This study aims to compare the bond strength of Ni-Cr alloys to ceramic after different types of grindings. Materials and Methods: 20 specimens made of Ni-Cr alloys were divided into two groups. The first group of specimens was grinded with a carbide bur (EL5, SS White Burs Inc, Lakewood, NJ, USA) in one direction and the second group of the specimens was grinded in multiple directions. After sandblasting and steam cleaning, 2 mm ceramic (Ceramico II, Ceramco Inc, Burlington, NJ-USA) was fused to Ni-Cr alloy. A tensile bond strength test was used and the data was analyzed by one-way statistically analysis of variance (ANOVA) and Student's t-test. Surface characterizations of Ni-Cr alloys are also examined on scanning-electron microscopy (SEM) after debonding. Results: Grinding alloys in multiple directions prior to the application of the ceramic, demonstrates significantly higher bond strength with ceramic than grinding in one direction (p<0.05). Conclusion: Within the limitation of this study, metal grinding in multiple directions with light hand pressure maybe an advantage in increasing metal-ceramic bond strength. INTRODUCTION The failure of the ceramic-to-metal interface instigates a discomfited situation for both patients and dentists. Even though dental ceramic is a brittle, it is still one of the most biocompatible materials for the restoration of teeth. New investigations attempt to bring high-quality mechanical properties to ceramic which is why full ceramic restorations are very much admired these days. However, these are generally not used for they are expensive and not experienced for long and posterior bridges. Conventional metal-ceramic restorations are nevertheless most preferred indications in most cases. Metal has a good mechanical strength than ceramic which is why this combination makes the restoration more resistant to the chewing forces. Although it is very common, metal and ceramic has bonding problems to work with [ 1 , 2 , 3 , 4 , 5 ]. The metal and ceramic have some bonding mechanisms. These are Van der Waal s forces, mechanical retention, compression bonding and direct chemical bonding [ 6 ]. The perception of these hypothetical skills is equally important as understanding the technical skills required for ceramic application, when considering a successful metal ceramic restoration. [ 6 , 7 , 8 ]. The use of the word ‘bond' demands that the link between dental ceramic and metal is simply a chemical one. Indeed, the function of chemical bonds throughout the bonding process is crucial and assumes considerable importance. Besides, it is perceived that a number of non-chemical mechanisms take part in the bonding of dental ceramic and its core metal substructure. [ 7 , 9 ]. The porcelain-bearing area of a metal casting contains many microscopic irregularities into which opaque porcelain may flow when fired. Air abrading the metal with aluminum oxide is assumed to improve mechanical retention further by eradicating surface irregularities (stress concentrations) while increasing the overall surfaces area available for bonding [ 7 ]. Despite its existence, mechanical retention's input to bonding may be moderately limited. Dental ceramic does not require a roughened area to bond to metal, it is believed that ceramic will fuse to a well-polished surface [ 10 ], but some surface roughness is effective in increasing bonding forces [ 7 ]. After the cast of the metal for metal-ceramic restorations, technicians prepare Ni-Cr alloy before the bonding of the ceramic. Grinding the surface of metal increases roughness,