Tensile strength of the interface between hydroxyapatite (HA) and bone was tested. Scanning electron microscopy was used to observe the tensile failure mode and the morphological change of hydroxyapatite ceramic surface in bone. The porosity of hydroxyapatite is 14% and pore size less than 2 microns. After 2 weeks of implantation, the tensile strength of the interface is 0.72 MPa. After 4, 8, and 16 weeks, the average tensile strength stayed at 1.5 MPa. SEM showed that tensile failure occurred at the HA-bone interface at the second week, but after 4 weeks, the failure occurred between HA particles within the bulk, and not at the HA-bone interface. Calcified tissue was directly deposited on the HA ceramic surface and exits also in the micropores. Near the interface, sintered necks among HA ceramic particles were subjected to biodegradation.

Tensile strength testing of the interface between bone and a plasma-sprayed hydroxyapatite (HA) coating-Ti-6Al-4V (implant I) and an HA coating-Ti (implant II) was performed. The bone-implant interface and tensile failure mode were evaluated by light microscopy (LM), SEM-energy dispersive X-ray analysis, and backscattered electron imaging. The crystallinity of the HA coating of implant I and implant II was 62 and 40%, respectively. Eleven semidisk implants of each type were inserted in the left tibia of 22 rabbits in each period. After 2, 4, 8, and 16 weeks, the tensile strength of the bone-implant I was 0.86, 1.32, 1.10, and 0.92 MPa, respectively; the value of the bone-implant II was 0.66, 0.92, 0.84, and 1.12 MPa, respectively. No significant difference was found in tensile strength between implant I and implant II, and between the data of different periods. LM and SEM revealed that the two types of coatings behave the same in bone. Failure after the tensile test mainly occurred at the bony tissue at 2 and 4 weeks, inside the HA coating layer at 8 weeks, and at the HA coating-metal substrate interface at 16 weeks. Degradation and delamination of the HA coating continued with time, resulting in the interfacial tensile strength not increasing with time. Thus, we concluded that differences between the two implants, mainly the difference in crystallinity of the HA coating (62 vs. 40%), have no significant influence on bone bonding ability, bone bonding strength, tensile failure mode, and degradation of the coating.

In this study, the wear pattern of seven commercial composite resins, one experimental composite and one dental amalgam were investigated. These materials were separately inserted in a separation preparation cavity of the patient's mouth. After clinical service for 3, 9 and 12 months the specimens were taken out and observed by scanning electron microscopy (SEM). It was found that the softer resin matrix wore away first while the inorganic filler particles showed no signs of abrasive wear, whereafter filler particles were loosened once there was no support of the resin matrix around them.

No abstract

A new machine was developed to study the wear of dental filling materials in vitro. Four products: amalgam, Adaptic, Clearfil and acrylic resin were tested. Wear was measured quantitatively by weighing the specimen, and the wear pattern was studied qualitatively with a scanning electron microscope (SEM). A comparison was made with materials that were placed in the mouth for a prolonged period. It was found that the in vitro wear pattern was comparable to that found in vivo.