Evaluation of the Effect of Different Laser Activated Bleaching Methods on Enamel Susceptibility to Caries; An In Vitro Mode

Abstract

IntroductionIn recent years, tooth whitening has become one of the most growing oral care sectors, boosted by patients, demanding both healthy mouth and attractive smile.1 As tooth color relies on the composition of tooth tissues, any chemical, mechanical or biological change can damage the esthetic equilibrium of the smile.2 Bleaching is a simple, non-restorative and noninvasive treatment for discolored teeth that is capable of satisfaction of the high demanding patients. So it has attracted much interest from the profession. Bleaching systems today are based on hydrogen peroxide as the active agent and are often activated by heat or light.3 Hydrogen peroxide acts as a strong oxidizing agent through the formation of free radicals and reactive molecules which attack dark colored macromolecules and break them into smaller and less colored ones. 4 Although other products such as carbamide peroxide or sodium perborate are available for bleaching, hydrogen peroxide is still considered to be the most effective and popular agent, since it is available in a range of formulations, concentrations and activation modes. In-office bleaching can provide significant brightness after only one session of treatment, but achievement of optimum results may require multiple sessions or longer time of application of the bleaching agents. 6,7 However, this may increase the risk of tooth sensitivity 8 and cause certain amount of enamel matrix degradation. 9Acceleration of hydrogen peroxide decomposition can be carried out through energy absorption from external source of energy like heat or laser, providing better patient compliance and may eradicate the side effects of high concentrated hydrogen peroxide.10,11 Because of tooth temperature concerns, lasers are now more preferred. Lasers such as diode (LED), halogen, Nd:YAG etc can be highlighted. Abstract Introduction: Today, bleaching is a routine noninvasive alternative for treatment of discolored teeth. The aim of this study was to determine whether conventional or laser activated bleaching predispose teeth to develop caries or not. Methods: Sixty human molars were mounted on acrylic cylinders and their Knoop microhardness (KHN) as well as DIAGNOdent (DD) values were recorded. They were divided into 4 experimental groups; G1) conventional bleaching with 40% hydrogen peroxide gel, G2) Diode laser assisted bleaching with same gel, G3) Nd:YAG laser assisted bleaching with the same gel, G4) control group. After bleaching, all samples were subjected to a three day pH cycling regimen and then, KHN and DD values were measured. Results: All groups had significant reduction in KHN values. It seems that there is no statistically meaningful difference between changes in enamel microhardness of the sample groups and all groups have changed in a similar amount. Reduction of DD scores were significant in Diode laser and conventional groups, however changes in Nd:YAG laser and control groups were not significant. Changes in DD values have followed a similar pattern among groups, except in G1-G4 a...

The effect of laser-activated bleaching with 810 nm and 980 nm diode lasers on enamel micro-hardness; an in vitro study

“…One study evaluated the effect of 35% hydrogen peroxide activated by LED, halogen light, and diode laser, and found a significant reduction in micro-hardness and variations in morph ology [28]. In the research of Ashnagar et al, conventional bleaching with 40% hydrogen peroxide gel alone and activation with a diode laser or Nd:YAG laser showed a reduction in Knoop hardness [5]. Kabbach et al observed a significant reduction in micro-hardness in the light-activated bleaching group [39].…”

“…These particles target the colored tooth molecules and convert them into smaller and less colored molecules [1][2][3]. Although some researchers have reported no adverse effects after bleaching, others have claimed that the use of such products can cause such effects, including changes to the enamel and dentin surfaces, the reduction of surface and subsurface micro-hardness, the reduction of Ca and p ratios, the loss of organic components from the tooth surface, and dental hypersensitivity [4,5]. During bleaching treatment, the morphological structure of the enamel surface is affected and its prisms are destroyed [6].…”

Effect of conventional and power office bleaching with diode laser and led light on enamel microhardness

“…Ashnagar et al 23 reported a decrease in Knoop microhardness after bleaching with the conventional technique with 40% hydrogen peroxide gel alone or with diode or Nd:YAG laser beams. In contrast to the present study, Ahmed et al 24 did not report any deleterious effects on enamel microhardness after the activation of bleaching agents with different light sources.…”

Effect of enamel surface pretreatment with different laser types and antioxidizing agents office-bleaching on the shear bond strength of orthodontic brackets

“…Light, heat, or laser can be used to accelerate the oxidation-reduction reaction and activation of the chemical agents involved in the bleaching process [12]. Various lasers such as Nd:YAG laser (1064 nm), diode laser (810 and 980 nm), Potassium-Titanyl-Phosphate laser (KTP, 532 nm), and Erbium: Yttrium Aluminum Garnet laser (Er: YAG, 2940 nm) have been used to accelerate bleaching gel [13][14][15][16][17]. By reviewing the papers published in this area, no study was done before on the effect of the laser immediately after the office-bleaching process on recovering the shear bond strength of the orthodontic brackets.…”