Abstract
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.
Highlights
Dentinal hypersensitivity (DH) is described in the literature as a “pain derived from exposed dentin in response to chemical, thermal tactile, or osmotic stimuli which cannot be explained as arising from any other dental defect or disease” [1]
The unlased dentin of the control groups which were only treated with ethylene diamine tetra-acetic acid (EDTA) showed a dentinal surface without the smear layer and wide open tubules (Figure 1)
Dentinal surfaces irradiated by means of Nd:YAP laser beam showed different structural changes depending on the delivered power
Summary
Dentinal hypersensitivity (DH) is described in the literature as a “pain derived from exposed dentin in response to chemical, thermal tactile, or osmotic stimuli which cannot be explained as arising from any other dental defect or disease” [1].Dentinal hypersensitivity is a quite common problem. DH is a very annoying disease which can have a negative influence on the quality of life, oral hygiene, and treatments like cleanings with ultrasonic instruments. The etiology of this disease remains unknown, but the most common accepted theory is the fluid movements/ hydrodynamic theory proposed by Braennstrom and Astroem, which involves the fluids movements of the tubules. These movements of the fluids are direct reactions of thermal, chemical, osmotic, and mechanical stimuli [4]. The odontoblastic processes are rounded by dentinal fluid coming from the pulp complex, which forms 22% of the dentinal volume [5], and some studies reported that sensitive
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