Objective To study the application of photodynamic therapy (PDT) for dental caries prevention using whole body luminescence fiber,and to investigate the effects of PDT on the content of Ca and P in rat molar enamel.Method The rat dental caries model was established by inoculating with S.mutans.Eighty male rats were randomly divided into five groups,including three experimental groups:17 mW (8 mW/cm2) PDT (group A),34 mW (15 mW/cm2) PDT (group B),68 mW (30 mW/cm2) PDT (group C),a positive control group:20 g/L NaF solution (group D),and a negative control group:0.9％ physiological saline (group E).The experimental groups were treated by 40 μg/mL hematoporphyrin monomethyl ether (HMME) and 650 nm diode laser irradiation.The experiments were conducted for 4 weeks.The contents of Ca and P in the molars of each group were measured by inductively coupled plasma emission spectrometry.Results The contents of Ca and P in group B,C and D after PDT were significantly higher than those in group A and E (all P＜0.05).The contents of Ca and P in group A showed no significant difference before and after PDT,while those in groups B and C showed significant increase after PDT (all P＜O.05).The increment of Ca in group A after PDT was lower than that in group D (P＜0.05),while those in group B and C were significantly higher than those in group D (all P＜0.05).There was no significant difference in the increment of Ca and P between group B and C after PDT.Conclusions In the range of the experimental parameters,the PDT promoted effect of tooth remineralization is better than 20 g/L NaF.The levels of Ca and P in the tooth enamel can be promoted by PDT treatment,and the contents of Ca and P are related to the pewer of PDT.The effect of low power PDT on the remineralization of enamel is not obvious.The contents of Ca and P in the tooth enamel are increased with laser power of PDT.When the laser power increased to a certain value,the change in contents of the two elements is not obvious.PDT can maintain the tooth remineralization microenvironment.

Objective To preliminarily select safe parameters for different forms of teeth by irradiating 532 nm picosecond Nd∶YAG laser on human isolated teeth with different irradiation time length and power.Methods Isolated human teeth including anterior teeth,premolars,molars were irradiated with 532 nm picosecond laser.Repeated measurements were made for each tooth by thermometer to measure the temperature of pulp chamber on different time point and power,and the temperature change (△T) was calculated.Results △T of the anterior irradiation group at 0.6 W,30 s;0.8 W,20 s and 30 s;1.0 W,10 s,20s and 30s were more than 5.6 ℃,which was the same with that of premolar group at 1.0 W,30s.△T of the molar group at 1.0 W,30 s was less than 5.6 ℃.Under certain power,the temperature of pulp chamber increased with the prolonging of irradiation time (P＜0.05).At a certain time,temperature increased with the power (P＜0.05).Conclusions It is safe to carry out operation on the parameters setting of 0.8 W,10 s and 0.6 W,20 s irradiation for anteriors teeth;0.4 W,30 s,0.8W,30 s and 1.0 W,20 s for premolar teeth,and 1 W,30 s for molar teeth.In the application of 532 nm picosecond laser,attention is required to be paid on parameter setting to control input power and irradiation time.