Impact of Using Nano-Hydroxyapatite on Color Stability and Postoperative Hypersensitivity of Two Bleaching Techniques : Randomized controlled Clinical Trial /

Abstract

The search for a more esthetic smile has grown exponentially during the last few decades. Consequently, tooth color is currently believed to be one of the biggest today’s patients concerns.(1, 2) Tooth bleaching has been recognized as simple, effective and well-accepted method for solving the problem of teeth discoloration. There are three major approaches to bleaching of vital teeth. In office bleaching, which is clinician supervised, “night guard” bleaching which is administrated by the clinician for home use by the patient, and commercial bleaching products which are applied by the patient.(3) In comparison between the three techniques, in –office bleaching has shown many advantages over the other techniques. It included the professional control throughout the whole procedure, quick initial results, reduced treatment time in addition to avoiding any accidental material ingestion and discomfort in wearing bleaching trays. This made the in-office bleaching a pioneer in bleaching treatment.(4) In office whitening technique, which was named power bleaching by many authors,(5, 6, 7, 8) is achieved via the use of high concentrations of hydrogen peroxides. This technique can be classified according to the mode of activation of the bleaching gel into photo catalyzed and chemo catalyzed in-office bleaching systems.(2, 9) Conflicting results regarding the whitening outcomes were evident in literature between chemo and photo catalyzed bleaching techniques. Some studies found that the photo catalyzed bleaching systems gave better whitening results,(7, 9, 10, 11) while others found no difference between the whitening efficacy of both techniques.(4, 12) These conflicting results made the choice between both techniques confusing. Furthermore, concerns have been expressed about limitations to efficacy of both power bleaching techniques in term of color stability and post-bleaching hypersensitivity.(3) Regression of tooth whitening is an Introduction

2 evident drawback that may follow the in-office bleaching techniques.(16, 17) Studies related this to the surface alterations induced by the bleaching gel.(18, 19, 20, 21) In addition, post bleaching hypersensitivity is one of the most prevalent drawbacks of in-office bleaching technique.(6, 13, 14) Although being the most prevalent drawback, its etiology is not yet fully understood.(3, 15) Currently, in the dental market, many desensitizing agents are available. Recently, Nano technology has paved the way for introduction of materials at Nano scale level having the same chemical composition of either organic or inorganic analogue of the hard tooth structure making them biomimetic.(22, 23, 24) Consequently appeared the revolutionary role of using the Nano hydroxyapatite. Gopinath (23) and Jena,(13) reported the desensitizing effect of Nano hydroxyapatite paste, however their clinical trials were carried out on virgin dentin. Jin et al(22) and Pepla et al(25) reported the lightening effect of the Nano hydroxyapatite paste, however their studies were carried out on demineralized enamel specimens. They attributed this to its role to act as filler to fill and repair the small holes and pores in enamel. Based on these findings, it could be assumed that Nano particles of hydroxyapatite might block the pores induced by the bleaching gel, thus maintain color stability and also reducing the post bleaching hypersensitivity. However, the impact of using Nano hydroxyapatite paste on the color stability and post-bleaching hypersensitivity was not tackled enough in the literature. Thus this clinical trial was carried out to elaborate; first: the difference between photo and chemo catalyzed inoffice bleaching techniques on color stability and post bleaching hypersensitivity, second: to monitor the impact of Nano hydroxyapatite paste on color stability and post- bleaching hypersensitivity of the two tested in-office bleaching techniques.