Physical and Chemical Properties of New Apatite Glass Polyalkenoate Sealant

Objective: This study aimed to evaluate the physical and chemical properties of a new apatite glass polyalkenoate cement (AGPC) for pit and fissure sealing. Methods: Conventional glass polyalkenoate cement (GPC) for pit and fissure sealing (Fuji III®, GC Co., Tokyo, Japan) was used as the control and base cement. AGPCs were created by replacing 8-36 wt% of the Fuji III powder with spherical-shaped hydroxyapatite (HAp, Taihei Chemical Industrial, Inc., Osaka, Japan) and then added with the Fuji III liquid at powder/liquid ratio (P/L) of 1.0-2.2. All specimens were stored in artificial saliva for 24 hours and subjected to three point flexural bending tests. Moreover, fluoride release dose of AGPCs and control specimens were measured for 90 days. To identify the elements present in the AGPC's core and matrix, polished and representative fracture surfaces of AGPC's specimens were subjected to SEM, EDS and XPS analysis. Results: The AGPCs' specimens with ≥24% HAp at P/L=1.0-2.2 showed significant increase in the flexural strength for 24 hours, when compared to the control at each P/L. Especially, the flexural strengths of the specimens with 20-28 % HAp at P/L=1.6 (e.g. 28% HAp added group: 19.4±3.8 MPa) were equal as a conventional restorative GPC. AGPCs had significantly higher dose of fluoride release compared with control GPC for 90 days. SEM images of fracture surfaces of AGPCs have shown that the matrix gel components have infiltrated into the HAp particles and closer adherence between glass core, HAp and matrix. Conclusion: AGPC has the great potential as an alternative conventional material for pit and fissure sealing with improved flexural strength, fluoride release and matrix properties. This research is supported by the Japan Science and Technology Agency (JST) and Japan Society for the Promotion of Science.