Effect of Sodium Hypochlorite (NaOCI) for Pretreatment of Early Demineralized Enamel Lesions in Enhancing the Remineralization Capacity of Self-assembling Peptide : (In-vitro Study) /

Abstract

Caries is considered the most widespread disease across the world and is reckoned as a dynamic process. Enamel caries always starts through a process of subsurface demineralization, leaving a microporous surface of lost minerals in-between the hydroxyapatite crystallites; after further demineralization of deeper (up to 30%) distance downwards, the microporous surface collapses leading to larger pores and breaks irreversibly (mechanical failure), and eventually enters the restorative cycle (2,3). Hence, emerged the concept of minimally invasive dentistry as a very conservative way of intervention defense against enamel breaking down where we can treat the demineralized lesions as early as possible. Within the oral cavity and throughout the whole time there is a constant alteration between periods of demineralization caused by bacterial acids, and periods of remineralization aided by minerals in saliva (5). Remineralization process takes place when the supersaturated saliva redeposits the lost minerals (mainly calcium Ca+2 and phosphate PO₄³⁻) back to fill the micropores, or through different external approaches, techniques, technologies and agents for remineralization. As time passes by, our thoughts and knowledge regarding the different ways of remineralization have improved; leading us to a better understanding of the concepts of biomimetic regeneration and the more recent technologies that goes on the other side from fluoride-mediated remineralization (4). The most recent remineralizing technology is the self-assembling peptide P11-4 which is considered as an ideal enamel regenerative approach. Its composition has a great effect on calcium ions affinity, grabbing these ions and depositing them on a de novo needle-shaped hydroxyapatite mesh work leading to better in-depth penetration remineralization of demineralized lesions.

This new approach presents the natural regeneration process of the lost enamel tissue (biomimetic remineralization). The progression or regression of a lesion primarily depends on equilibrium phases of demineralization-favoring pathological factors and the preventive remineralizing factors. Analysis of many in-vitro studies and data regarding the action of selfassembling peptide showed that the presence of P11-4 fibers in the depth of the lesions led to faster hydroxyapatite deposition and formation, with great increase in microhardness of the remineralized subsurface lesions. P11-4 has shown very optimistic results as a biomimetic mineralizing agent in in-vivo studies and clinical trials. This includes the ability to reverse early occlusal and proximal lesions that are more resistant to fluoride remineralization. Self-assembling peptide has been developed and patented by the University of Leeds, (UK). The Swiss company Credentis has licensed the peptide technology and markets it under the registered trademark Regenamel Curodont RepairTM with Curolox® Technology. Its mode of application as stated by the manufacturer is to first ensure a clean enamel surface, then start the surface pretreatment by applying sodium hypochlorite (3%) followed by acid etching with phosphoric acid gel (35-37%). Pretreating enamel surface with sodium hypochlorite prior to acid etching acts as a deproteinizing agent removing the organic elements and the acquired salivary pellicle from the surface; this significantly increases enamel’s surface retention up to 94.47% and enhances penetrative depths, also improves the quality of type I and II etched enamel patterns (18,19). The idea of deproteinizing enamel with 5.25% NaOCl before acid etching with phosphoric acid (H3PO4) and its influence on the patterns of etching and bonding of the adhesives to tooth structure has been investigated. On the other side, the application of sodium hypochlorite after acid etching during the process of surface pretreatment has been discussed in literature proving its effect in enhancing the shear bond strength (SBS) values, increasing the penetration and retention of adhesive resins by 20.1% compared to the conventional way of only acid etch the enamel surface, and affects the surface roughness of enamel surface with the minimum percentage of surface loss. Upon all these findings regarding using sodium hypochlorite as an enamel surface pretreatment and self-assembling peptide remineralization capabilities, it was found thought-provoking to study the effect of applying sodium hypochlorite as a deproteinizing agent after acid etching of demineralized sound enamel structure with the aim of minimizing loss of surface enamel, exposure of more reactive enamel, and creation of porosities that may allow for more rapid uptake of remineralizing solution as assessed by surface microhardness (SMH) testing. Literature regarding the use of sodium hypochlorite after acid etching in enamel remineralization as a surface pretreatment for increased penetration were found to be deficient, and further studies are found to be in need.