Variation in surface texture measurements

Surface texture influences cellular response to implants, implant wear, and fixation, yet measurement and reporting of surface texture can be confusing and ambiguous. Seven specimens of widely different surface textures were submitted to three internationally renowned laboratories for surface texture characterization. The specimens were from dental implants, orthopedic implants, and femoral heads. Areas to be measured were clearly marked; simplified instructions were supplied but specific measurement parameters were not requested. Techniques used included contact profilometry, two- and three-dimensional laser profilometry, and atomic force microscopy. Four to thirteen parameters were reported, 2D or 3D, including R(a) or S(a); only three were common to all centers. The results varied by as much as +/-300-1000%, depending on technique and surface type. Some surfaces were not measurable by some techniques. One dental implant surface was reported with R(a) of 0.17, 0.85, 1.9, and 4.4 microm. The CoCr femoral head ranged from an R(a) of 0.011 to 0.10 microm; the zirconia head from 0.006 to 0.05 microm. Similar variability was reported for the other parameters. Useful surface texture characterization requires reporting of all measurement parameters. Comparisons between studies may be compromised if differences in technique are not considered.