Safety And Efficacy Of Laser Photodynamic Effect Assisted Bleaching Of Tetracycline Teeth

Objective:In this study,the safety of KTP laser bleaching was verified by measuring the temperature change of the isolated pulp cavity,and the efficiency of KTP laser assisted bleaching of colored teeth with different types of bleach was measured by constructing a tetracycline colored tooth model,and the effect of KTP laser applied to bleaching tetracycline teeth was analyzed and observed,providing experimental basis for clinical treatment of tetracycline teeth.It provides a way to treat endogenous colored teeth in clinic.Methods:The parameters of the KTP laser used in the experiment were all controlled as follows: power 350 m W,spot diameter 6mm,continuous wave mode,and distance from the tooth surface 20 mm.Pulp cavity temperature test experiment: 15 human maxillary incisors were selected to prepare pulp cavity temperature test specimens,and the specimens were divided into 3groups with 5 samples in each group.Group A: KTP laser irradiation group only;Group B:KTP laser combined with SDIpola gel group(37.5%HP);Group C: KTP laser combined with erythrin gel(10%HP).The temperature change of pulp cavity was measured within110 s and recorded every 10 s.The temperature change between groups was compared,and the time when the temperature change of pulp cavity in group C was within the safe range was obtained.Tooth bleaching colorimetric experiment: 25 isolated wisdom teeth with uniform dentin thickness of young patients were selected to prepare a tetracycline colored tooth model,and the specimens were divided into 5 groups with 5 samples in each group.Group a: SDI pola gel bleaching group(37.5%HP);Group b: bleaching group containing erythrin gel(10%HP);Group c: KTP laser irradiation 30 s assisted SDI pola gel bleaching group(37.5%HP);Group d: KTP laser irradiation 30 s assisted bleach group containing erythrin gel(10%HP);Group e: KTP laser irradiation for 60 s followed by bleaching group containing erythrin gel(10%HP).Colorimeter was used to measure the color difference of each group immediately after bleaching,15 d and 30 d after bleaching,and compared the bleaching efficiency and color stability between groups.Results:Pulp cavity temperature test experiment:The changes of pulp cavity temperature in all groups showed an increasing trend with time(P<0.05).The changes of pulp cavity temperature at each time point of KTP laser irradiation in group A were greater than those in groups B and C(P<0.05),and the changes of pulp cavity temperature at each time point of the bleaching group with high concentration gel combined with KTP laser irradiation in group B were smaller than those in groups A and C(P<0.05).The temperature change of group C low concentration photosensitive gel combined with KTP laser irradiation was between the two groups,and the temperature increase of group B and group C within 100 s of laser irradiation was within the temperature safety threshold of 5.5℃.Tooth bleaching comparison experiment: After bleaching,all groups produced a certain bleaching effect,in which group c immediately after KTP laser-assisted high-concentration bleaching gel bleaching,the change ?E of tooth color was the largest,and much higher than that of control group a(P<0.05),group b after low-concentration photosensitive bleaching gel bleaching,?E was the smallest(P<0.05).The immediate?E of group d and group e after bleaching of low-concentration photosensitive gel with the help of KTP laser irradiation for 30 s and 60 s,respectively,was greater than that of group b(P<0.05),and the immediate ?E of group e was larger than that of group d after prolonged laser irradiation time(P<0.05).After 15 d and 30 d,the ?E of each group had a certain change,and the ?E of c,d and e laser groups decreased immediately after 30d(P<0.05),while the ?E of group a decreased slightly(P<0.05),and the ?E of group b increased slightly(P>0.05).Conclusion:Under the condition that KTP laser power is 350 m W,spot diameter 6mm,continuous output mode,distance from tooth surface 20 mm,the process of assisted bleaching gel bleaching within 100 s irradiated by KTP laser is safe,and does not exceed the threshold of pulp cavity temperature change of 5.5℃.The effect of KTP laser assisted bleaching of tetracycline teeth is remarkable.The relatively safe low concentration bleaching gel can improve the efficiency of tooth bleaching by KTP laser assisted,photodynamic effect caused by photosensitizer and prolonging laser irradiation time in a safe range,which is equivalent to that of using high concentration gel bleaching alone.