In Vivo Pilot Study: Effect of Dehydration/Rehydration on Upper Anterior Tooth Color Change

Abstract

Isolation of tooth structure during fabrication of a bonded, direct, resin-based restoration is essential to optimizing its potential for long-term clinical success. Failure to protect etched enamel and bonding agents from contamination by saliva results in inadequate and unpredictable interfacial bonding of the restorative composite, potentially leading to marginal discoloration, open margins, recurrent decay, or ultimately to restoration loss or failure. A consequence of tooth isolation during placement of direct, esthetic restorative resins is the dehydration of enamel surfaces that will not be coated with saliva, and will, over time, lose water that has penetrated into the outer enamel layers (will dehydrate). The longer the tooth isolation time, the greater will be the subsequent loss of water from enamel. Presence of this water in enamel helps to provide for a stable tooth color. In teeth, the observed tooth color is the result of internal light penetration and interaction with tissues below the surface. Enamel is a translucent material, passing a great majority of transmitted light to fall on the more opaque and yellow-colored tissue underneath of it: dentin. In the hydrated state, enamel is more translucent than in its dehydrated state. The white opaque appearance of dehydrated enamel can be of great clinical concern, once a rubber dam has been removed, and the treated teeth with newly placed restorations are observed. Usually, because of the opaque, white nature of recently dehydrated enamel, there is an initial mismatch between an esthetic restoration just placed and its surrounding, remaining enamel. Patients are normally forwarded of this consequence, and are advised that a period of time needs to pass before the surrounding enamel becomes rehydrated, and more translucent (less opaque), before its pre-isolated color returns to a natural state. It is hoped that, at that time, the new restoration will perfectly match the color characteristics of the remaining enamel, and the recent replacement will not be visible at all, but will instead optically blend in without notice. However, prior to that time, there are definitely distinct color differences between a recently placed resin restoration and its surrounding tooth structure. To date, little-to-no information is available on the rate at which a clinician or patient can expect isolated enamel to return to its pre-isolated color, and when to expect this esthetic blending to occur.