Activation of endodontic irrigants using a 9.3 µm CO2 and diode lasers: A laboratory proof of concept model.

PURPOSE: To investigate the differences between irrigant propagation and temperature changes using laser-activated irrigation (LAI) at different settings in an artificial root canal model. METHODS: Using an artificial resin root canal model, irrigant activation was achieved in 19 experimental groups with eight samples each. A 9,300 nm CO2 laser, two diode lasers with different settings (wavelengths 455, 808, 970, and 980 nm) were compared to 2,940 nm Er:YAG laser and traditional needle irrigation. Er:YAG and CO2 laser were activated in the pulpal chamber only, while diode lasers and needles were inserted into the main root canal. Lasers were activated for 5x 20 seconds resulting in 100 seconds of activation or rinsing for each sample. After each activation of 20 seconds, a photo was taken of the side canals and the propagation of the dye was measured with a digital measuring tool after calibration. Further, the temperature of the irrigant was reported after activation of 20 seconds and repeated 5 times. Data were checked for normality and statistically compared. RESULTS: All lasers increased the irrigant propagation compared to conventional irrigation. Significant differences were found between groups regarding propagation and temperature (P< 0.0027). Er:YAG and CO2 laser had similar effects on irrigant propagation in middle and apical located side-canals with specific power parameters and were superior to diode lasers and syringe irrigation. The irrigant's temperature increased significantly with the diode and CO2 lasers. CLINICAL SIGNIFICANCE: Diode lasers and CO2 lasers have not been established for irrigant activation. 9,300 nm CO2 lasers absorb well in water and were shown to introduce vapor bubble formation and streaming in water. Diode lasers are highly accepted in periodontics. The laser light is not absorbed in water but interacts with bacteria as well as soft tissues and contributes therefore to infection control. With a modified laser tip it was however possible to introduce cavitation and streaming in irrigants.

Influence of 9.3 µm CO2 and Er:YAG laser preparations on marginal adaptation of adhesive mixed Class V composite restorations with one component universal adhesive.

PURPOSE: To examine the marginal adaptation in enamel and dentin of mixed Class V saucer shaped restorations where cavities were prepared by two different lasers. METHODS: A handpiece-integrated Er:YAG laser @ 4.5 W, 300 mJ, 15 Hz (LiteTouch III) and a novel CO2 laser @ 12.95 W, 19.3 mJ, 671 Hz (Solea 9.3 µm). Diamond bur preparation with a 25 µm diamond bur (Intensiv) in a red contra angle at high speed under water spray cooling served as the control. Eight cavities per group were readied and restored under simulation of dentin fluid with a one bottle universal adhesive (One Coat 7 Universal) and a nanohybrid resin composite (Everglow), applied in two layers. For every preparation technique, the adhesive system was applied in the selective-etch and the self-etch mode, resulting in six experimental groups. Marginal analysis was performed immediately after polishing and after simultaneous thermal (5-50°C, 2 minutes each) and mechanical (max. 49 N; 200,000 cycles) loading by using a SEM (x200 magnification). RESULTS: Significant differences were found for all groups - except groups 2 and 5 - between initial and terminal results and between the groups as well (P< 0.05, 2-way ANOVA with Fisher's post-hoc test). The bur prepared group with selective-etch technique showed the best overall results after loading, followed by Er:YAG prepared self-etch group and CO2-prepared selective-etch group. CLINICAL SIGNIFICANCE: By using a universal one-component adhesive system, marginal adaptation in enamel and in dentin depended on the preparation method and on the adhesive's application technique as well. When using lasers, Er:YAG in self-etch mode and CO2 9.3 µm in selective-etch mode total marginal adaptation showed results which were comparable to conventional bur preparation with selective-etch technique.