Effect of deproteinization agents on bonding to developmentally hypomineralized enamel

Abstract

OBJECTIVES: This study compared bonding of dental adhesive to developmentally hypomineralized enamel (HE) after deproteinization with either 5.25% NaOCl or Papacarie gel (Papacarie Duo®). METHODS: Flat enamel specimens from hypomineralized first permanent molars, embedded in acrylic cylindrical molds, were randomly allocated to one of the following six groups (n = 10): Group 1 – Normal Enamel (NE); no deproteinization; Group 2 - NE + NaOCl; Group 3 NE + Papacarie gel; Group 4 - HE (5 creamy-white, 5 yellowish-brown); no deproteinization; Group 5 - HE (5 creamy-white, 5 yellowish-brown) + NaOCl; Group 6 - HE (5 creamy-white, 5 yellowish-brown) + Papacarie gel. Enamel specimens from Groups 1 and 4 were etched with 32% phosphoric acid gel (3M ESPE) for 10 s, followed by rinsing with de-ionized (DI) water for 10 s. Acid-etched enamel specimens from Groups 2 and 5 were treated with 5.25% NaOCl for 60 s; while those from Groups 3 and 6 were treated with Papacarie gel for 60 s, followed by rinsing with DI water for 10 s. Subsequently, all specimens were air- dried, bonded with Adper Single Bond 2 (3M ESPE) and light-cured for 10 s. Composite build-ups were performed using FiltekTM Z250 (3M ESPE) and subjected to microshear bond strength testing. Bond strength data were analyzed using 2-way ANOVA and Tukey test (α = 0.05). RESULTS: Pre-treatment with deproteinization agents significantly increased bond strength to HE, compared to sound enamel (p<0.05). No significant difference in bond strength was found between creamy-white or yellowish-brown HE. Conversely, no difference in bond strength was found between the two deproteinization agents, 5.25% NaOCl and Papacarie gel. CONCLUSIONS: Both 5.25% NaOCl and Papacarie gel are effective deproteinizing agents, which improved bond strength of developmentally hypomineralized enamel (This study was supported by HKU Seed Funding Programme for Basic Research 201509159028).