Abstract
To develop a pit and fissure sealant for partially erupting permanent teeth, we modified the liquid of tetracalcium phosphate (4CP) cements. We investigated their adhesion to enamel as well as their properties, and found the most promising compositions of the liquid. We also investigated the changes in each cement mixture when immersed in distilled water or phosphate buffered saline. The liquid consisted of 50wt% water,30wt % polyacrylic acid (mixture of various ratios of 2 kinds which differed in number-average molecular weight),15wt%citric acid, and 5wt% tartaric acid. By changing the ratio of the 2 kinds of polyacrylic acid, we obtained 5 kinds of liquid. They were mixed with 4CP and their setting times, compressive strengths (according to the ADA specification NO.61for polycarboxylate cements), and adhesion to enamel were measured. Using 25wt% polyacrylic acid whose number-average molecular weight was 5000 and 5wt% polyacrylic acid whose number-average molecular weight was 12000, we obtained a mixture which had the widest utility, high adhesion, and high compressive strength. We then made 4 kinds of powder consisting of 4CP and/or CaF2-((1)4CP, (2)99wt% 4CP-1wt% CaF2, (3)90wt% 4CP-10wt% CaF2, and (4)70wt% 4CP-30wt% CaF2) and 2 kinds of powders consisting of 4CP and SrF2((1)98wt% 4CP-2wt% SrF2, (2)90wt% 4CP-10wt% SrF2). We mixed them with the liquid stated above and each mixture was examined on the same properties. It was found that only 90wt% 4CP-10wt% SrF2 decreased its compressive strength. We also immersed these mixtures in distilled water or phosphate buffered saline, and examined how their 4CP converted to hydroxyapatite (HAp) by X-ray diffraction.4CP converted more quickly to HAp in phosphate buffered saline than in distilled water. The presence of CaF2 or SrF2 stimulated the conversion to HAp.
