Combined Effects of Er:YAG Laser and Nano-Carbonate Apatite Dentifrice on Dentinal Tubule Occlusion: In Vitro Study

Dentinal tubule occlusion using Er:YAG Laser: an in vitro study

OBJECTIVES

We analyzed the effects of the Er:YAG laser used with different parameters on dentinal tubule (DT) occlusion, intrapulpal temperature and pulp tissue morphology in order to determine the optimal parameters for treating dentin hypersensitivity.

METHODOLOGY

Dentin specimens prepared from 36 extracted human third molars were randomized into six groups according to the treatment method (n=6 each): control (A); Gluma desensitizer (B); and Er:YAG laser treatment at 0.5 W , 167 J/cm2 (50 mJ, 10 Hz) (C), 1 W , 334 J/cm2 (50 mJ, 20 Hz) (D), 2 W , 668 J/cm2 (100 mJ, 20 Hz) (E), and 4 W and 1336 J/cm2 (200 mJ, 20 Hz) (F). Treatment-induced morphological changes of the dentin surfaces were assessed using scanning electron microscopy (SEM) to find parameters showing optimal dentin tubule occluding efficacy. To further verify the safety of these parameters (0.5 W, 167 J/cm2), intrapulpal temperature changes were recorded during laser irradiation, and morphological alterations of the dental pulp tissue were observed with an upright microscope.

RESULTS

Er:YAG laser irradiation at 0.5 W (167 J/cm2) were found to be superior in DT occlusion, with an exposure rate significantly lower than those in the other groups (P<0.05). Intrapulpal temperature changes induced by Er:YAG laser irradiation at 0.5 W (167 J/cm2) with (G) and without (H) water and air cooling were demonstrated to be below the threshold. Also, no significant morphological alterations of the pulp and odontoblasts were observed after irradiation.

CONCLUSION

Therefore, 0.5 W (167 J/cm2) is a suitable parameter for Er:YAG laser to occlude DTs, and it is safe to the pulp tissue.

Evaluation of the Effects of 810 nm Diode Laser Alone and in Combination With Gluma© and Chromophore on Dentinal Tubule Occlusion: A Scanning Electron Microscopic Analysis

Introduction: Tooth hypersensitivity is among the most common patient complaints caused by the response of exposed dentin to external stimuli. No definite treatment has been suggested so far for dentin hypersensitivity (DH). This study aimed to compare the efficacy of the diode laser alone and in combination with Gluma and chromophore in occluding opened dentine tubules and the treatment of DH. Methods: This in vitro study was conducted on 30 extracted human third molars kept in 0.1% thymol solution. The teeth were mounted in transparent acrylic resin and the buccal enamel was cut to expose the outer third of dentin. The samples were then divided into 6 groups of negative control (no smear layer removal), positive control (smear layer removal with 6% citric acid application), 810 nm diode laser irradiation (energy density 55.55 J/cm2 , 1 W for 20 seconds in a continuous mode), chromophore (1 mg/mL indocyanine green, ICG) plus diode laser irradiation (1 W, 20 seconds), Gluma plus diode laser irradiation, and Gluma + chromophore + diode laser. Dentinal tubules were evaluated under a scanning electron microscope at x2000 magnification. The mean percentage of the obstruction of dentinal tubules was reported as mean and standard deviation. Considering the normal distribution of the data, two-way ANOVA was applied to compare the efficacy of treatments, and an independent-samples t test was used for pairwise comparisons at P<0.05 level of significance. Results: The highest mean percentage of the obstruction of dentinal tubules was noted in the diode laser/chromophore/Gluma group (65.68±12.31%) while the lowest value was noted in the diode laser/Gluma group (24.33±5.90%). Pairwise comparisons revealed significant differences between all groups (P <0.05) except for the difference between the laser/Gluma/chromophore and laser/ chromophore groups (P =0.20). Conclusion: It seems that chromophore increases the efficacy of the diode laser for the obstruction of dentinal tubules.

Effects of different treatments on chemical and morphological features of eroded dentin

To evaluate the treatment of eroded dentin (Sensodyne Repair & Protect™, Er:YAG laser and combinations). The occlusal surfaces of 25 third molars were sectioned 1.5 mm in thickness. After an erosion cycle (5 min in demineralizing solution + 3 h in remineralizing solution; six cycles a day for 8 days), the samples were divided into five groups (n = 5): (E) erosion - control; (ES) erosion + Sensodyne Repair & Protect (NovaMin); (EL) erosion + Er:YAG laser (40 mJ, 10 Hz, 0.4 W, 50 μs, 3.1 J/cm², 63 W/cm²); (ELS) erosion + Er:YAG laser + Sensodyne; and (ESL) erosion + Sensodyne + Er:YAG laser. Following storage in ultrapure water (37 °C/14 days), the Ca/P ratio was evaluated by EDXRF and the morphology surfaces examined in SEM. The percentage of exposed dentin tubules was calculated. One-way analysis of variance and Tukey's test at 5% were used to treat the data. The Ca/P ratio was higher in E and ES groups. More exposed dentin tubules were found in E group and less exposed tubules were found in the ES group (p < 0.0001). When the toothpaste and laser were combined, the number of occluded dentin tubules was higher when laser was performed first (ELS). A positive effect was found when the laser and toothpaste were combined.

Laser-assisted treatment of dentinal hypersensitivity: a literature review

The purpose of this literature review was to evaluate the effectiveness of the laser-assisted treatment of dentinal hypersensitivity. A review with inclusion and exclusion criteria was performed from January 2009 to December 2014 with electronic data-bases: MedLine via PubMed, Science Direct and Cochrane Library. Research of paper magazines by hand was not considered. Forty-three articles were selected between literature reviews, in vitro studies, clinical trials, pilot and preliminary studies. The items were divided into laser-used groups for an accurate description, and then the reading of results into various typologies. Laser-assisted treatment reduces dentinal hypersensitivity-related pain, but also a psychosomatic component must be considered, so further studies and more suitable follow-ups are necessary.

Treatment of dentinal hypersensitivity by means of Nd:YAP Laser: a preliminary in vitro study

Objective. The aim of this study is to evaluate the effectiveness of Nd:YAP laser to seal dentinal tubules at different parameters. Material and Methods. 24 caries-free human wisdom impacted molars were used. The crowns were sectioned transversally in order to totally expose the dentin. The smear layer was removed by a 1 min application of EDTA. Each surface was divided into four quadrants, but only three quadrants were irradiated at a different output power setting (irradiation speed: 1 mm/sec; optical fiber diameter: 320 µm; tangential incidence of beam and in noncontact mode). Samples were smeared with a graphite paste prior to laser irradiation. All specimens were sent for SEM analysis. Pulp temperature increases in additional twenty teeth were measured by a thermocouple. Results. Morphological changes in dentin surfaces depend on the value of used energy density. Higher energy densities (2 W–4 W; 200–400 mJ; pulse duration: 100 m sec.; and 10 Hz) induce higher dentin modifications. Our results confirmed that Nd:YAP laser irradiations can lead to total or partial occlusion of dentin tubules without provoking fissures or cracks. Measurements of pulp temperature increases showed that Nd:YAP laser beam can be considered as harmless for pulp vitality for following irradiation conditions: 2 W (200 mJ) to 4 W (400 mJ) with an irradiation speed of 1 mm/sec; fiber diameter: 320 micrometers; 10 Hz; pulse duration: 100 m sec; noncontact mode and in tangential incidence to exposed dentin. The perpendicular incidence of the laser beam on exposed dentin may injure pulp vitality even at low output power of 3 W. Conclusions. Nd:YAP laser beam was able to seal the dentin tubules without damaging dentinal surfaces and without harming pulp vitality. Nd:YAP laser is effective and may be safely used for future in vivo treatments of dentinal hypersensitivity under certain conditions.