Effect Of Photodynamic Therapy On Resin-dentin Bonding Interface

Objectives:The aim of the present study was to evaluate the effect of photodynamic therapy(PDT)on the resin-dentin bonding interface.The aim of the first experiment was to evaluate the effect of photosensitizer(PS)[0.01%MB]on the resin-dentin bonding interface.It was tested microtensile bonding strength(MTBS)of five groups through microtensile bonding strength tests.It was observed through fracture modes of resin-dentin bonding interface,resin-dentin bonding interface,adhesive penetration and the microstructure of resin protrusion through microscope,scanning electron microscope(SEM)and confocal laser scanning microscopy(CLSM),in order to provide experimental basis for resin filling repair in clinic.The aim of the second experiment was to evaluate the effect of PDT on the resindentin bonding interface using different illumination time.It was tested microtensile bonding strength(MTBS)of five groups through microtensile bonding strength tests.It was observed through fracture modes of resin-dentin bonding interface,resin-dentin bonding interface,adhesive penetration and the microstructure of resin protrusion through microscope,scanning electron microscope(SEM)and confocal laser scanning microscopy(CLSM),in order to provide experimental basis for resin filling repair in clinic.Methods:Firstly,80 fresh caries-free human third molars were extracted according to whether light was given or not.It was divided into two groups according to the random number table method:the group without illumination or with illumination.Each group had 40 teeth.The whole experimental teeth in experiment 1 were the group without illumination,and the whole experimental teeth in experiment 2 were the group with illumination.In this study,first of all,80 fresh third molars were collected without caries.They were divided into two groups according to whether with illumination by random number table method:groups with illumination and groups without illumination,each group had 40 teeth,in study one,the whole teeth were in without illumination,and in study two,the whole teeth were with illumination.In study one,fifteen freshly,extracted human third molars of forty third molars were initially divided randomly in five groups(n=3 per group)by the random number table method:Group A:group with no incubation(control);Group B1:incubate with PS for 1 min;Group B2:incubate with PS for 2 min30 s;Group B3:incubate with PS for 5 min;Group B4:incubate with PS for 10 min.The dentin layers were exposed.Samples in group A and B1-B4 were surface incubated with PS(0.01%methylene blue).Different groups were incubated for different time.The dentin surface was applied with adhesives and composite resin was piled up in four increments.Then,the samples were cut to obtain 1mm×1mm×8 mm strips(n=10 per group).The fifty specimens were divided into 5 groups randomly for MTBS test and stereomicroscope to observe the fracture modes.The remaining 10 teeth,observation of dentin surface for SEM,the remaining 15 teeth for CLSM,observed between groups of mixing layer and formation of resin tag.Forty freshly,extracted human third molars were initially divided randomly in five groups(n=10 per group)by the random number table method:Group a:group with no illumination(control),Group b1:illuminate for 1min,Group b2:illuminate for2min30s,Group b3:illuminate for 5min,Group b4:illuminate for 10min.The dentin layers were exposed.Samples in group a and b1-b4 were surface incubated with PS.Each group was illuminated for the same time.Different groups were illuminated for different time.After the irradiation,dentin surface was applied with adhesives and composite resin was piled up in four increments.Then,the samples were cut to obtain 1mm×1mm×8mm strips(n=10 per group).The fifty specimens were divided into 5 groups randomly for MTBS test and stereomicroscope to observe the fracture modes.The remaining 10 teeth,observation of dentine surface and using SEM,the remaining 15 teeth for CLSM,observed between groups of mixing layer and formation of resin tag.Results:1.In-study one,one-way ANOVA suggested that PS had no obvious influence on resin-dentin bonding surfaces.There was no statistical significance in the MTBS tests(P>0.05).In study two,one-way ANOVA suggested that the effect of PDT on resin-dentin bonding interface using different illumination time had significant influence statistically.There was no statistical significance in the MTBS test(P<0.05).Subsequently,Bonferroni method was used to correct the significance level,and it was found that there was statistically significant difference between the control and group b3 in PDT(adjusted P=0.044),and between the control and group b4in PDT(adjusted P=0.047),while there was no statistical significance difference between other groups.2.In study one,resin cohesive failure mode was the main fracture type.The proportion of other failure modes was low,and there was no significant difference among groups.In study two,adhesive surface failure was the main fracture type.With the extension of illumination time,the resin and dentin cohesive failure mode did not increase,but gradually decreased,and the mixed fracture mode was less.It can be observed that the bonding surface of the fracture mode was much larger than other fracture modes.3.In study one,the results of observing by SEM were as follows:dentin surfaces of group A,B1,B2,B3 and B4 were covered with stained layer obviously,no dentin demineralization was observed around the canal,the dentin tubules were closed,and no dentin tubules were seen at all,and each sample formed short resin tags at the dentin interface.The different incubation time of PS on dentin surfaces had no significance on the penetration of adhesive.In study two,the results of observing about dentin tubules by SEM were as follows:dentin surfaces of group a,b1,b2,b3 and b4 were covered with stained layer obviously,partial dentin around the canal was demineralized,and the closure of dentin tubules was not obvious,and the dentin tubules could be almost directly seen.In group b1-b4,the surfaces were covered with stained layer to different degrees,and dentin demineralized to different degrees and the dentin tubules were closed to different degrees.Each sample in dentin interface visible short resin.4.In study one,the observation results of the penetration of adhesive and the resin tags by CLSM were as follows:it can be seen that shorter resin tags were formed near the surface in each group,and the penetration depth of resin tags into dentin tubules in each experimental group was similar to the control,and the distribution was regular and uniform.In study two,the observation results of the penetration of adhesive and the resin tags by CLSM were as follows:group a,shorter resin protrusions were formed on the surface of the dentin,and their distribution was more regular and uniform.Several short resin protrusions were formed on the surface of dentin in group b1.Several short resin ridges were formed on the surface of dentin in group b2.Short resin protrudes were not easily formed on the surface near dentin in group b3.No short resin protrusions were formed on the surface of the dentin in group b4.Conclusions:In study one,PS had no obvious influence on resin-dentin bonding interface using different illumination time.In study two,PDT had influence on resin-dentin bonding interface using different illumination time.After illuminating for more than 5 mins,the resin-dentin bonding strength will be weaken.