| ObjectivesPosts and cores are frequently used in endodontically treated teeth that suffered excessive loss of coronal tooth structure . When crown portion is less than 2mm, adequate retention within the root can ensure the successful preservation of the restoration and endodontically treated teeth. Different luting cements significantly affect the retention of posts. Resin cements have been reported to produce 150% to 200% the retention strength of zinc phosphate and glass ionomer cements. To detect the reasons that result in the difference, this study examines the compositions of the three kinds of cements,root canal dentin ,two kinds of prefabricated posts and the dentin - cement - post interface by means of laser Raman microscopy. And this study supplies more infonnation about the post adhesion mechanism and reference for the clinical choice of posts and luting cements.Material and Methods1. Adhesive substances' laser - raman analysis: Laser raman spectroscopy measure of root canal dentin and two kinds of prefabricated posts.2. Cements' laser -raman analysis:Laser raman spectroscopy measure of zinc phosphate, glass ionomer and resin cements.3. Preparation of the cement/dentin interfaces specimen and laser - raman analysis.3.1 Six extracted intact human maxillary anterior teeth were sectioned at2mm coronal to the cementoenamel junction that were then for regular endodontic treatment. After one week, the roots were prepared for post insertion. The canal space of each root was made with parapost twist drills to a final diameter of 1. 5mm and a depth of 9mm from the cervical surface.3. 2 All roots were embedded with transparent epoxy resin in 18 mm * 15 mm * 9mm rectangle block, the prepared post space located in center and vertical to the 18mm * 9mm surface. Two prefabricated posts were cemented respectively with the three different luting cements.3.3 All specimens were attached to the grips of a low speed saw and sectioned parallel to long axis of the posts.3.4 The raman spectra of the cement/dentin interface were acquired at pos-itons corresponding to 4μm intervals across the interface and with an integration time of 180 sec.ResultsThe bands associated with the root canal dentin occur at 585,960,1070, 1240,1454,1650 cm-1 . Ti alloy prefabricated post hasn' t characteristic signal. The glass fiber prefabricated post' s relative bands occur at 990,1113,1188, 1224,1447,1612,1720 cm-1. The bands associated with ZPC and GIC may occur at 1500 cm-1 and 1400 cm -1 respectively, while resin cement' s spectra occur at 1113,1221,1400,1450,1608,1720 cm-1.There are no evident raman spectra change cross the ZPC/dentin interface and GIC/dentin interface , while cross the resin/dentin interface and resin/glass fiber post interface significant vibrations can be seen.Conclusion1. Raman microspectroscopy is a useful analytical technique for studying the compostion of bonding of cement/dentin .2. Different cements have different adhesion mechanism, ZPC and GIC can' t infiltrate root canal dentin whereas resin cement may interact with the dentin... |
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