Abstract

AHMED, A  and  OWEN, CP. A base-line study of the wear of burs used for chairside milling of ceramic crowns of different hardness - Effect on internal fit and surface roughness. S. Afr. dent. j. [online]. 2020, vol.75, n.10, pp.534-540. ISSN 0375-1562.  http://dx.doi.org/10.17159/2519-0105/2020/v75no10a1.

INTRODUCTION: Wear of milling burs may affect the internal fit and surface roughness of the milled crown. AIM: To assess the wear of diamond and tungsten carbide (TC) burs from milling ceramic materials and the effect on internal fit and surface roughness. METHODS: Thirty crowns of each of the two materials were milled from the same standard preparation. Diamond burs were used for a feldspathic ceramic and TC burs for zirconia. Before and after the 10^th, 20^th and 30^th milling, diamond particle loss was counted and cutting blade changes of the TC burs measured. Internal fit was measured using a silicone replica technique and surface roughness by 3D laser microscope. RESULTS: An average 26% loss of diamond particles occurred after 30 crowns, resulting in a 6% decrease in internal luting space and a 21% decrease in surface roughness. Wear of the TC burs resulted in a 13% decrease in the luting space, and a 16% increase in surface roughness. CONCLUSION: The wear of milling burs reduces the luting space, and the milling parameters must be adjusted to compensate for this. Surface roughness is affected by bur type: with diamond burs it decreased, and increased with TC burs.

Keywords : CAD [CAM milling burs]; internal fit; surface roughness; ceramics.

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