The effect of fluoridated and non-fluoridated rewetting agents on in vitrorecurrent caries

Objective: This study examined the in vitro caries inhibiting potential of fluoridated and non-fluoridated rewetting agents that are applied to acid-e tched enamel and dentine before the use of a water-free, dentine adhesive. Materials and methods: Twelve caries-free premolars were divided into three groups of four teeth each. 2 x 3 x 1.5 mm cavities were prepared on the me sial and distal surfaces of each tooth, with half of the cavosurface margin in enamel and half in root dentine. In Group I (control), One-Step (Bisco, Schaumburg. USA) was applied without etching or rewetting agents. In Group IT. cavities were acid-etched, rinsed, dried, and rewetted with Aqua-Prep (Bisco). a non-fluoridated rewetting agent, and then bonded with One-step. Treatment for Group III was similar to Group III except that Aqua-Prep F (B isco), a fluoridated rewetting agent was used. Bonded cavities were restore d with a non-fluoride-containing flowable composite (AE liteFlo. Bisco). Ar tificial carious lesions were induced in these specimens, from which multip le 100 +/- 20 mum thick longitudinal sections were prepared. yielding 16 sp ecimens per group for evaluation with polarised light microscopy (PLM) and microradiography (MRG). Representative sections were processed for transmis sion electron microscopy (TEM) examination and scanning transmission electr on microscopy/energy dispersive X-ray (STEM/EDX) analyses. Results: The differences in demineralisation of dentine among the groups we re not statistically significant for 'relative' lesion depth (p > 0.05, ANO VA, Student-Neuman-Keuls test). but highly significant for 'relative' lesio n area (p < 0.001). Wall lesions were consistently present in Group I, whil e inhibition zones were invariably observed in Group III. 87.5% of Group II specimens exhibited neither wall lesion nor inhibition zone. TEM showed th at remnant dentine apatite crystallites within the inhibition zones in Grou p III were larger and denser than those present within the corresponding wa ll lesions. STEM/EDX analyses confirmed the presence of calcium, phosphorus and fluorine in these plate-like crystallites. Conclusion: When used with a water-free, single-bottle dentine adhesive, a non-fluoridated rewetting agent is able to reduce, but cannot completely pr event recurrent caries. The use of a fluoridated rewetting agent is useful under the situation when microleakage occurs, by providing the additional b enefit of fluoride-induced demineralisation inhibition. (C) 2001 Elsevier S cience Ltd. All rights reserved.