Brushing-induced surface roughness of nickel-, palladium-, and gold-based dental casting alloys.
BACKGROUND
Alloys with high nickel content have been increasingly used for dental prostheses. These alloys have excellent hardness, elastic modulus, and strength, yet have high corrosion rates when exposed to chemical or physical forces that are common intraorally.


OBJECTIVE
The purpose of the current study was to measure the susceptibility of several types of nickel-based alloys to brushing abrasion relative to gold- and palladium-based alloys.


METHODS
Au-Pt, Au-Pd, Pd-Ag, Ni-Cr, and Ni-Cr-Be dental alloys were brushed with a toothbrush (Oral-B Soft) and toothpaste (Ultrabrite) in a linear brushing machine, then the surface roughness was measured by profilometry (R(a), R(v), R(p)). Specimens (n=4) were brushed for 48 hours in a saline solution (pH 7). The effect of brushing was determined using 2-sided t tests (alpha=.05), and roughness among alloys postbrushing was compared using 1-way ANOVA with Tukey post hoc analyses (alpha=.05).


RESULTS
All polished alloy surfaces (before brushing) had roughnesses of <or=0.1 microm (R(a)). The Pd-Ag alloy was the most resistant to brushing. The Ni-Cr-Be alloy abraded the most, with a postbrushing surface roughness of >1 microm (R(a)). Ni-Cr alloys without Be had a postbrushing surface roughness of 0.25 microm (R(a)). Postbrushing roughness of all other alloys ranged from 0.1-0.25 microm (R(a)). R(v) and R(p) values behaved similarly to R(a) values for all alloys.


CONCLUSIONS
Although they have many excellent mechanical properties, Ni-Cr-Be alloys may be prone to degradation from brushing.
University of Washington School of Dentistry, D770B HSC, Box 357456, 1959 NE Pacific St, Seattle, WA 98195-7456, USA. jwataha@u.washington.edu
John C
JC
Wataha
Petra E
PE
Lockwood
Regina L W
RL
Messer
Jill B
JB
Lewis
Donald J
DJ
Mettenburg
D001608:Beryllium / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry*; D003775:Dental Polishing; D006047:Gold Alloys / Q000737:chemistry*; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014099:Toothbrushing / Q000295:instrumentation*; D014100:Toothpastes / Q000737:chemistry
D002858:Chromium Alloys; D003722:Dental Alloys; D006047:Gold Alloys; D014100:Toothpastes; D012965:Sodium Chloride; D010165:Palladium; D009532:Nickel; D001608:Beryllium