Effects of Er:YAG and CO2 Lasers With and Without Sodium Fluoride Gel on Dentinal Tubules: An In Vivo Scanning Electron Microscope Analysis

Abstract

Dentinal hypersensitivity is one of the most disturbing chronic complaints in dentistry; clinicians have been trying to manage this problem for the last century. However, only little progress has been achieved due to the inability to determine the nature of this problem. Dentinal hypersensitivity has been shown to be directly related to the number and size of the exposed dentinal tubules which allow the passage of the stimulus to the pulp. With the recent development of laser technology and their applications in dentistry, the main goal of this study is to evaluate the potential of Er:YAG and CO2 laser with or without fluoride to occlude the open dentinal tubules.Thirty-six teeth indicated for extraction due to severe periodontitis were used in this study. The roots of all teeth were prepared by forceful scaling and 1% citric acid application for 1 min to expose the dentinal tubules. Then teeth were divided into six groups where group I received no further treatment and group II was treated with 2% NaF gel only. Group III received Er:YAG laser (50 mJ, 3 Hz) while group IV received CO2 laser (0.5 W, continuous wave) treatments for the prepared root surface. Groups V and VI received similar laser treatments as groups III and IV, respectively, following the application of 2% NaF gel to the root surface. Then teeth were extracted atraumatically and prepared for scanning electron microscope evaluation of the treated surfaces.Dentinal tubules were successfully exposed in the control group I; the diameters of the tubules had a mean of 1.96 ±0.60 and the number of open dentinal tubules was 1.19 per 100 ?m2. Group II exhibited narrowness of the diameters of the dentinal tubules (mean 1.12 ±0.30) and the number of open dentinal tubules was 0.94 per 100 ?m2. In group III, the surface of the root seemed smooth with the rare presence of open tubules. In group IV, a high melting appearance has caused a change of surface appearance giving a whirl-like structure around each supposed dentinal tubular entry. In group V, closure of dentinal tubular orifices was achieved with the formation of an amorphous surface. In group VI, an irregular but smooth melted surface covering dentinal surface occurred with the absence of open dentinal tubules. For diameters of dentinal tubules, the results from combination groups revealed statistical significant difference compared to the control group (Group I vs group V and group I vs VI). For numbers of open dentinal tubules, group I showed statistical significant difference compared to the groups III, IV, V, and VI, also group II showed statistical significance compared to groups III, IV, V, and VI.All laser treatments gave the photomicrographic image that suggests the reduction of hypersensitivity in the examined teeth. The additional effect of fluoride seems to be beneficial as fluoride might have engaged in the new structure formed after melting of the dentinal surface. However, these effects' reflection on hypersensitivity remain theoretical and need to be supported by further comprehensive clinical studies.