Synergistic Effect On Acid Resistance In Human Dentine As A Function Of Pulsed CO₂ Laser Irradiation Combined With 38%Ag(NH₃)₂F

Objective: This study determined the synergistic effect on acid resistance and dentinal desensitization in human dentine as a function of pulsed CO2 laser irradiation combined with 38%Ag(NH3)2F treatment.Methods: Each molar from 15 extracted molars was made into four identical dentinal specimens, which were randomly divided into 4 groups, each one receiving different treatment: A (control group); B (pulsed CO2 laser irradiation); C (coated with 38%Ag(NH3)2F); D (laser irradiation + fluoride). Then, all groups were demineralized artifially. Micro-hardness test, SEM and X-ray energy spectrum analysis were taken prior and after demineralization. Statistic methods: two-way ANOVA and LSD test with SPSS 10.0.Results: The groups prior demineralization in hardness order:D,C,A,B(P<0.01); the groups after demineralization in hardness order:D,C,B,A (P<0.01) ; the groups in acid resistance order: D,C,B,A(P<0.01) ; the groups in the order of At% change of elements:B,D,C,A(P<0.01). Under SEM: group A showed clear dentinal tubuliprior and after demineralization; group B showed melted surface without dentinal tubule opens prior demineralization whereas melted layer disappearing with tubule reopening after demineralization; group C showed thicker melted layer without dentinal tubule opens prior demineralization whereas melted layer disappearing with tubule reopening after demineralization; group D showed that there were no dramatic difference caused by demineralization with the thickest melted and recrystalized layer on dentine surface.Conclusion: The synergistic effect on acid resistance in human dentine as a function of pulsed CO2 laser irradiation combined with 38%Ag(NH3)2F treatment was formed, despite of their individual disadvantages. Not only was the effect on acid resistance in human dentine reinforced, but also the mechanical properties and dentinal tubule sealing were maintained.