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ABSTRACT
The mechanical removal of dentinal caries traditionally involves the use of tactile sensation and/or caries-indicating dyes. This study tested the hypothesis that self-limiting polymer burs are as effective as conventional carbide burs in creating substrates for dentin bonding. Carious dentin from extracted human molars was removed with carbide or polymer burs, with dental explorer hardness as the end-point for caries removal. Dentin substrates were bonded with etch-and-rinse or self-etch adhesives and prepared for microtensile bond testing and transmission electron microscopy. For each bur type, there was no difference in bond strength between adhesives. However, the polymer bur surface exhibited significantly lower bond strengths than the carbide bur, and both were lower than flat, non-carious dentin controls. TEM revealed areas of incompletely removed, denatured caries-infected dentin in the polymer bur specimens. These first-generation polymer burs might best be utilized for deep caries removal where pulpal exposure is a concern.
KEY WORDS: polymer bur, caries-affected dentin, caries-infected dentin, microtensile bond strength, transparent zone.
INTRODUCTION
Disease prevention is the ultimate goal in restorative dentistry (Featherstone, 2000; Pitts, 2004). Ideally, caries removal should be accomplished with minimal patient discomfort during and after the restorative procedures (Anusavice and Kincheloe, 1987; Malmström et al., 2003). The existence of two layers of carious dentin has been well-reported in the literature (Massler, 1967; Fusayama, 1979). The superficial layer of caries-infected dentin is grossly denatured and is a poor substrate for adhesion of restorative materials (Nakajima et al., 1995; Yoshiyama et al., 2002). The underlying layer of partially demineralized caries-affected dentin contains dentinal tubules that are usually filled with Whitlockite caries crystals, rendering it highly impermeable to dentinal fluid transudation (Lee et al., 2003), or the creation of rapid fluid shifts (Brännstrom, 1986) that may stimulate the underlying A-δ nerve fibers and cause post-operative sensitivity (Närhi et al., 1994). Since caries-affected dentin contains intact, undenatured collagen fibrils and is amenable to remineralization (ten Cate, 2001), there is a general consensus for this layer to be preserved during caries excavation (McComb, 2001; Kidd, 2004).
Traditionally, carious dentin may be removed mechanically with burs, hand excavators, and air-abrasion, or chemomechanically with the adjunctive use of a deproteinizing agent alone, or in combination with amino acids (Yip and Samaranayake, 1998; Banerjee et al., 2000)....