This study tested the following hypotheses: (1) acid-cleaned and passivated
unalloyed titanium implants have higher surface energies (which are consid
ered desirable for hone implants) than ethanol-cleaned titanium; (2) higher
temperatures of heat treatment of unalloyed titanium result in higher surf
ace energies; and (3) these changes can be related to changes in surface co
mposition and roughness. Thus, unalloyed titanium specimens were either aci
d-cleaned and passivated (CP) or ethanol-cleaned (Et). Each set was then di
vided into 3 groups and heat-treated for 1 hour at 316 degrees C (600 degre
es F), 427 degrees C (800 degrees F), and 538 degrees C (1,000 degrees F),
respectively. Surface roughness values for each of these groups were determ
ined using atomic force microscopy, while surface compositions were determi
ned using Auger electron, x-ray photoelectron, and Raman spectroscopic tech
niques. Surface energies were estimated using a 2-liquid geometric mean tec
hnique and correlated with surface roughness, elemental composition, and el
emental thickness. The CP surfaces were slightly rougher than the Et specim
ens, which had greater oxide thickness and hydrocarbon presence. The surfac
e oxides were composed of TiO2, Ti2O3, and possibly titanium peroxide; thos
e heat-treated at 427 degrees C or above were crystalline. The CP specimens
had carbonaceous coverage that was of a different composition from that on
Et specimens. The CP specimens had significantly higher surface energies,
which showed statistically significant correlations with oxide thickness an
d carbonaceous presence. In conclusion, ethanol cleaning of unalloyed titan
ium dental implants may not provide optimal surface properties when compare
d to cleaning with phosphoric acid followed by nitric acid passivation.