Figure 1. TEM micrographs of unbonded dentin substrate following caries removal with the self-limiting polymer bur. (A) Unstained, undemineralized section showing incomplete removal of the caries-infected dentin (asterisk). Loosely arranged smear layer remnants (S) were often identified on top of this layer. Dentinal tubules within the underlying transparent zone (TZ) were almost completely filled with electron-dense mineral deposits (open arrowhead). Patent dentinal tubules were occasionally present within this zone (arrow). E, epoxy resin. (B) Stained, demineralized section from the zone of incompletely removed caries-infected dentin, showing complete denaturation of the dentin collagen network into a gelatinized mass of microfibrils (open arrowhead). (C) Stained, demineralized section from the transition zone, showing a generalized retention of collagen fibrillar structure, despite the absence of cross-banding from individual collagen fibrils (pointer). Derangement of some collagen fibrils into microfibrillar stands could also be recognized (open arrowhead). (D) Stained, demineralized section from the sound dentin (not shown) beneath the transition zone, showing the presence of a dense collagen network with intact banding identified from individual collagen fibrils.