Materials and Methods

Forty non-carious human primary molars were extracted and stored at room temperature in an aqueous solution of 0.1% thymol for no longer than 3 weeks before they were used.  The crowns were sectioned from the roots at the cementobuccal enamel junction and each crown was cut longitudinally in a mesiodistal direction.  The facial and lingual surfaces of the crowns were embedded in autopolymerizing resin with the facial or lingual surfaces exposed.  Dentin surfaces were ground (wet) into a flat surface using a standardized technique with a series of 180 _ , 320 _ , and 600 _ silicon carbide abrasive paper using a grinder/polisher (Automata, Jeanuuirtz Co, West Germany).  A total of 80 dentin surfaces were prepared and randomly allocated into 10 groups of 8 specimens each (Table 1).  Specimens in groups 1 and 6 received no pretreatment and served as a control.  Specimens in groups 2 and 7 were covered with a paste of ZOE (Chemtest Laboratories Inc., USA) mixed at powder:liquid (P:L) ratio of l0g:lg.  Specimens in groups 3 and 8 were treated in a similar manner to groups 2 and 7 but ZOE was mixed at a lower P:L ratio of 10g:2g.  Specimens in groups 2, 3, 7, and 8 were covered with tinfoil and stored in closed containers filled with distilled water at 37°C for 7 days.  After that time, the ZOE was mechanically removed with an ultrasonic scaler until the dentin surfaces were macroscopically free of the material.  Specimens in groups 4 and 9 were placed on gauze soaked in FC (PD Produits Dentaires, Switzerland), sealed in closed containers, and kept at 37°C for 2 days.  The groups were pre-treated for different periods following the method described by Soeno et al.⁴  Specimens in groups 5 and 10 were placed on gauze soaked in FS (Astringedent®, Ultradent, USA), sealed in closed containers, and kept at 37°C for 2 days.  All specimens were rinsed with tap water for 15 seconds and dried with oil-free compressed air for 5 seconds before bonding.

An adhesive masking tape with a circular hole (3 mm in diameter) was applied to the prepared dentinal surface so the dentin adhesive was applied to a standardized area.  The application of the two adhesive systems was carried out according to the instructions given by the manufacturers.  Prime and Bond® NT adhesive resin (Dentsply/Caulk, USA) was applied for groups 1–5 and Opti Bond Solo Plus adhesive resin (sds Kerr, Sybron Dental Specialties, USA) was applied for groups 6–10 (Table 1).  A resin composite, XRV^TM Herculite® (sds Kerr, Sybron Dental Specialties, USA) was handled according to the instructions of the manufacturer and placed in two increments onto the dentin surfaces via clear plastic tubes that were 3 mm high with an internal diameter (ID) of 3 mm, which were placed perpendicular to dentin surfaces.  All specimens were stored in closed containers filled with distilled water at 37°C for 24 hours.  SBSs were determined using an lnstron (Instron Limited, England) testing machine running at a crosshead speed of 0.5 mm/min.  The SBSs were calculated and expressed in MPa.  Statistical analysis was conducted using non-parametric one-way analysis of variance (Kruskal-Wallis test) with a Tukey Post Hoc test.  The level of significance was chosen at P=0.05.

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Citation Number: Vol. 6, No. 3, Page 016