Fatigue properties of hydroxyapatite-coated dental implants after exposureto a periodontal pathogen

We studied the fatigue properties of rods (4 mm diameter) of hydroxyapatite -coated, titanium alloy implant material after it was exposed to a periodon tal pathogen, Actinobacillus actinomycetemcomitans (Aa), We varied the crys tallinity of the hydroxyapatite (HA) coating in these rods to the levels of , 60.5%, 52.8%, and 47.8%, Each rod was first inoculated with Aa in the log phase of its growth cycle, After 48 h, we counted the adhered cells. We me asured the dissolution of HA coating due to bacterial exposure alone by det ermining the calcium and phosphate concentrations in the bacterial growth m edia. Once the adherent bacteria were removed from these rods, we subjected them to 5 million cycles of fatigue testing after immersion in Lactated Ri nger's solution. We then determined the calcium and phosphate concentration s in the fatigue media. We found additional coating loss after fatiguing of the samples. This coating loss was a cumulative effect of bacterial exposu re and fatigue loading of the hydroxyapatite-coated dental implant alloy, T he lower crystallinity sample showed a higher loss of coating within the ra nge of crystallinity studied here, The HA coating in implants during clinic al use may undergo such changes, because they are exposed to the same bacte ria, (C) 2000 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 53 : 467-474, 2000.