Combined Effects of Laser and Fluoride on Acid Resistance of Human Pits and Fissures Enamel. XY.XU, DY.HU*, YM.YE, (West China College of Stomatology, Sichuan University, Chengdu, Sichuan 610041, CHINA) The purposes of this study was to investigate the effect of normal pulsed Nd:YAG laser irradiation at different energy level combined fluoride on the acid resitance of human pits and fissures enamel and the safety of laser irradiation.  Forty-eight extracted permanent teeth (molars and premolars) without any lesions in the pit and fissure areas were divided into four subgroups randomly.  The control group was applied with acidulated phosphate fluoride (APF) for 4 minutes.  The occlusal surfaces of the other three groups were applied with 1.23% APF for 4 minutes after 100mJ, 150mJ, 200mJ normal pulsed Nd:YAG laser irradiation respectively.  Lesions were created with acidified gel.  After lesion formation, sections were obtained and imbibed with water for polarized light study.  The depth of lesion were measured along enamel prism at the point of 0mm, 0.25mm, 0.5mm, 0.75mm under the position where fiber was placed.   To evaluate pupal damage, selected Wistar rats' teeth were irradiated in vivo, extracted 1,3,7,14 days postlasing, fixed, decalcified, sectioned, stained, and read for pulpal damage.  The one-way ANOVO was used to analyze the results.  The lesion depth is shown as table.  The results suggest that 100mJ normal pulsed Nd-YAG laser irradiation combined 1.23% APF might be effective in increasing the acid resistance of the pits and fissures enamel and the irradiation at this energy level is safe.

 

Table  Lesion depth in different deep part of pits and fissures

		Depth of lesions (µm)
Energy	0.00mm	0.25mm	0.50mm	0.75mm
Control	186.00±160.85	216.00±128.83	240.00±40.00	340.00±84.85
00mJ	69.33±39.083*	82.66±52.01*	137.33±37.67*	173.33±37.75*
50mJ	149.00±49.91**	220.00±79.06**	264.00±89.8**	380.00±147.87**
100mJ	89.33±51.45**	167.00±77.84**	209.33±43.94**	240.00±56.57**

*comparing to control group p<0.05,  **comparing to control group p>0.05