Effect of NaOCl or EDTA pretreatments on the shear bond strength of the resin-infiltrated white spot lesions to the resin composite: an in vitro study

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BACKGROUND: To evaluate the effect of sodium hypochlorite (NaOCl) or ethylene diamine tetraacetic acid (EDTA) pretreatment on the exposure rate of demineralised enamel pores, the penetration depth of resin infiltration and the shear bond strength (SBS) between the resin-infiltrated enamel white spot lesions (WSLs) and composite resin. METHODS: One hundred and four sound premolars were used for the study, from which sixty-four were randomly selected to have 4 mm × 4 mm × 2 mm enamel blocks cut from the center of the buccal surfaces. These were then divided into five treatment groups: SE (sound enamel control), DE (demineralised enamel control), RI (resin infiltration only), N/RI (NaOCl pretreatment + resin infiltration), and E/RI (EDTA pretreatment + resin infiltration). Enamel pore exposing ratios and resin penetration depths were assessed using scanning electron microscopy and confocal laser scanning microscopy. Forty teeth crowns were prepared from the remaining sound premolars, embedded in cubic acrylic resin blocks except for the buccal surfaces, and divided into five equal groups. The enamel surfaces of the crowns were treated according to the respective group protocols and bonded with a cylindrical resin column, 2.5 mm in diameter and 5 mm in height, for SBS testing. The SBS was then measured and analysed among the groups. RESULTS: Enamel pore exposing ratios in the N/RI and E/RI groups were significantly higher than in the RI group (p = 0.001), and the resin penetration depth in the N/RI group was significantly higher than in the RI group (p = 0.009). The SBS values (Mean ± SD, MPa) for the groups were as follows: SE (29.70 ± 5.24), DE (20.32 ± 3.97), RI (25.60 ± 3.95), N/RI (26.70 ± 2.67), and E/RI (28.05 ± 3.25) (p < 0.001). All resin-infiltrated groups showed significantly higher SBS compared to the DE group, while the SBS values for N/RI and E/RI were not significantly different from those of SE. CONCLUSIONS: The combined use of enamel surface pretreatment and resin infiltration treatment can increase the bonding strength of resin composite to WSLs and appears to be a promising and effective treatment option for WSLs therapy.

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