Tooth Preparation with a 9.3 μm CO 2 Laser Reduces Demineralization around Dental Restorations

Objective: To determine if cavity preparation using a 9.3 μm CO 2 -laser can prevent demineralization around a traditional composite, bioactive composite, flowable composite, or glass ionomer restoration compared to preparation with a traditional carbide-bur. Methods: Forty human posterior teeth were randomized. Vickers surface hardness measurements (MicroMet® 2104 Buehler) of enamel were taken. Twenty samples were irradiated with the 9.3μm CO2-laser and twenty were identically prepared using a carbide-bur. Each group (n=5) was restored with Filtek™ One Bulk Fill Restorative (3M) (Filtek OB), ACTIVA™ BioACTIVE- RESTORATIVE™ (Pulpdent) (ACTIVA), GC Fuji IX GP® FAST (GC) (Fuji), or Filtek™ Bulk Fill Flowable Restorative (3M) (Filtek F) per manufacturer instructions. Samples were placed in 0.05M acetate buffer demineralizing solution for 7 days, thermo- mechanically cycled for 10,000 cycles between 4-5°C and 55-60°C with a dwell time of 15s, immersed in 2% methylene blue solution and cut longitudinally. Three Vickers surface hardness measurements of enamel and dentin were taken near the subsurface restorative margin. Microleakage was assessed by measuring dye penetration along the gingival floor. Samples restored with the same material were compared using the two-sample t-test. Significance level was set at 0.0042 using the Bonferroni correction for multiple comparisons. Results: Laser-irradiated and bur prepared groups had similar baseline surface microhardness for all materials. Sub-surface enamel microhardness of laser-irradiated samples in ACTIVA and Filtek F groups, and dentin microhardness of laser-irradiated samples in Filtek OB, ACTIVA, Fuji, and Filtek F groups were statistically significantly greater than bur-prepared samples. There was no difference in microleakage between laser-irradiated and bur-drilled samples. Conclusion: Using a 9.3 μm CO2-laser in tooth preparation can prevent demineralization around Filtek OB, ACTIVA, Fuji and Filtek F restorations compared to traditional carbide-bur preparation.