Dentin microhardness after exposure to orange juices and human saliva

OBJECTIVES: To evaluate the effect of two different orange juices on microhardness of human dentin.

METHODS: Twenty sound human teeth were collected and cut perpendicularly in half along the long axis of the tooth. One half of each tooth was used for the study. The specimens were grinded to expose solid dentin surface, mounted into clear acrylic, then grinded up to 4,000 grit sand paper to give a flat surface.  An Akashi/LECO M-400-H1 Knoops Hardness Tester was used to measure dentin microhardness, with a 200gr load at 15sec application. Two different commercially available orange juices were used:  (A) Orange Juice (Tropicana, Florida) with pH 3.65 and (B) Orange Juice with calcium- and Vitamin D-added (B) (Tropicana, Florida) with pH 3.94.Ten specimens were immersed in each solution, 3 times a day for 10sec each for a total of 7 consecutive days. After exposure, all specimens were rinsed for 5sec under tap water and stored again in filtered human saliva and stored at room temperature until the next juice exposure. Pre- and post-microhardness measurements were taken by the same experienced examiner. Three measurements per specimens were taken at baseline and post-treatment cycle respectively.

RESULTS: Analyzed data showed that there is statistically significant difference (p<0.05) between baseline and post-treatment microhardness measurements in group A, indicating hardening of the dentin. In group B, post-treatment data showed increased values which were not statistically significant.

	Baseline	Post-Test
Group  A (n=10)	62.41 (±12.20 SD)	79.74 (±15.22 SD)
Group B (n=10)	62.19 (±12.63 SD)	66.16 (±9.43 SD)

CONCLUSION: In vitro exposure to orange juice, with or without calcium and Vitamin D-added did dot negatively affect dentin microhardness when specimens were stored in human saliva. In fact, in both groups, increase of dentin microhardness values following juice exposure was observed.