Surface Analysis of Anodization-Hydrothermal Treatment of cpTitanium in Rat Maxilla

Objectives: Highly crystalline thin hydroxyapatite (HA) layers deposited on the surface of commercially pure titanium (cpTi) by discharge anodic oxidation and hydrothermal treatment (SA-treatment) enhance the value of cpTi as endosseous implant material in clinical dentistry. The SA-treatment in particular is important for the osteoconductive properties of cpTi. However, for this approach to be effective the HA layer must retain its chemical stability during osseous wound healing. This study characterized the morphological, chemical and structural features of HA layers on SA-treated cpTi surface in the rat maxilla. Methods: SA-treated cpTi implants (diameter 1.0mm, length 2.0mm) were placed in the maxilla of 8-week-old Wistar rats. After 28 days, the maxilla were harvested and thin HA layers on SA-treated cpTi surface were analyzed by electron probe microanalyser (EPMA), scanning electron microscopy (SEM), and x-ray photoelectron spectroscopy (XPS). Results: EPMA revealed an even distribution of P and Ca in the HA layers before and after being placed in the maxilla. SEM analysis showed that the precipitated HA crystals were a typical single hexagonal columnar shape and were highly crystalline. Neither the morphology nor the crystalline features of the thin HA layer were altered during the 28 days. The XPS analysis indicated no change in the binding energy of P and Ca in the HA crystals before or after being placed in the maxilla. Conclusion: The thin HA layer formed on the SA-treated cpTi implants appeared to remain stable during the process of osseous wound healing. Furthermore, the highly crystalline HA that results from the SA-treatment may play a key role in osteoconduction during osseointegration. Supported by a Grant-in-Aid for Scientific Research (# 16390562) from the Japanese Ministry of Education, Science, Sports and Culture.