| Summary: | 碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 100 === The treatments of dentin hypersensitivity so far do not lead to satisfactory clinical outcome. Our previous study showed that gelatin-templated calcium mesoporous silicate (GCMS) with 30 % H3PO4 could efficiently occlude dentinal tubules by precipitates as deep as 30 μm in 10 minutes without eroding dentin and thus have great potential in treating dentin hypersensitivity. To be an ideal dental material in clinic, both efficiency and biocompatibility are prerequisite as well as the exploration of its mechanism. Thus, the aim of this study was (1) to evaluate the biocompatibility of GCMS for feasibility in treating dentin hypersensitivity clinically, (2) to investigate the release of ion concentration from GCMS/30 % H3PO4 through dentin disc, (3) to evaluate whether the precipitation (crystalline GCSM) is mainly constructed from our materials or incorporated from the dentin substrate using three alkaline-earth metal mesoporous silicates.
First, the GCMS was synthesized using mesoporous silica as carrier, impregnated with CaCO3 precursor and calcinated at 400°C for 5 hrs. The biocompatibility was evaluated by both elution and transwell dentin disc model of test materials (GCMS GCMS/30 % H3PO4, Calcium hydroxide and Seal & Protect) using WST-1, LDH and ALP. The cells used for this study were 3T3 fibroblast cells and human dental pulp cells. Second, the release of phosphoric acid and calcium ion of the mixture of GCMS mixing with H3PO4 through dentin disc barrier (0.2 mm in thickness) was determined using ion chromatography. Calcium hydroxide mixing with deionized water served as comparison. Third, three alkaline-earth metal mesoporous silicates with different ration of 30 % H3PO4 by the same pH value was applied to dentin disc samples to examine the crystal penetration by SEM and the elements distribution by EDS.
GCMS with 30 % H3PO4, calcium hydroxide and Seal & Protect showed higher cytotoxicity compared to GCMS extraction. However, GCMS with 30 % H3PO4 had great biocompatibility through dentin disc barrier as comparisons. The transwell dentin disc model and ion chromatography revealed that calcium hydroxide with deionized water would not release calcium ion through 0.2 mm dentin disc. However, as to the mixture of GCMS and 30 % H3PO4, PO4 3- could be determined in 5 minutes and then Ca2+ came in 10 minutes. The result demonstrated that calcium ion was not easily penetrate through the dentin barrier without PO4 3-. PO4 3- could be a pilot to usher Ca2+ into dentinal tubules. Thus, we could hypothesize that the concentration of PO4 3- increased to affect the electric property and attracted Ca2+ penetrate into dentinal tubules. Subsequently, the pH value elevated and led to recrystalized penetration. Under EDS analysis, the precipitation in the dentinal tubule presented great amount of strontium ion deposition which revealed mesoporous silicates contributed mostly to the precipitation/ crystallization.
The present study demonstrated that the GCMS and GCMS mixing with 30 % H3PO4 through dentin disc barrier have excellent biocompatibility. In acidic condition, phosphoric acid plays a crucial factor to introduce calcium ion to penetrate into dentin disc barrier. GCMS mixing with 30 % H3PO4 could release calcium ion rapidly and massively let penetration mainly comes from our material and show better acidic resistence. GCMS with 30 % H3PO4 has feasibility for treating dentin hypersensitivity clinically.
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