Influence of Different Storage Media on Microhardness of Enamel Surface

Objectives: The objective of this study was to assess the influence of storage methods in the micro hardness of enamel specimen.

Methods: Each enamel specimen (3mm in diameter) from bovine anterior teeth was stored in 5ml of 6 different media (saline, distilled water, 0.1% thymol solution, Hank's balanced salts solution (HBSS), 70% ethanol, freezing -20°C with no surface contact of water), respectively, at 4°C for 25 days. In order to evaluate storage effect, Vickers micro hardness of enamel surface was measured before and after storage of specimens.

Results: After storage for 25 days in the saline, distilled water, 0.1% thymol solution, HBSS media, the micro hardness of the enamel surface have decreased significantly (p<0.001). The micro hardness of saline group (-36%) showed the largest decrease and distilled water (-30%), 0.1% thymol solution (-30%), HBSS (-13%) followed. In contrast, storing teeth in 70% ethanol (-1%) and freezing -20°C (+3%) did not have significant difference in the micro hardness before and after storage.

Group	N	Before storage	After storage	Delta (D)		D %
Saline	16	309.1±26.21	198.7±31.8	-110.4±29.78 *	a	-35.7
Distilled water		313.6±22.79	221.2±26.10	-92.4±14.00 *	b	-29.5
0.1% thymol		307.1±29.56	216.3±28.10	-90.8±20.09 *	b	-29.6
HBSS		312.3±22.34	273.0±31.65	-39.4±21.60 *	c	-12.6
70% ethanol		310.6±24.27	307.5±21.52	-3.1±4.55	d	-1.0
-20°C		304.4±35.51	312.5±38.78	8.0±10.64	d	2.6

^{a, b, c, d}: Grouping by Duncan's multiple comparison test (ANOVA), ^*:p<0.001 by paired t-test

Conclusion: It was concluded that -70% ethanol and freezing -20°C with no surface contact of water could be proper methods for storage of teeth in micro hardness study.

This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MOST) (No. R13-2003-013-01004-0).