Influence of 10% sodium ascorbate gel application time on composite bond strength to bleached enamel

Figures & data

Table 1. Materials, compositions and application modes.

Product (batch number)	Composition	Application mode
PollaOficce+ (P1204021)	37.5% hydrogen peroxide	Apply a thin layer (1 mm) of the gel and leave for 8 min; Remove gel with dental gase; Repeat steps 1 and 2 four times, totalling 40 min exposure time; At the end of the procedure, wash for 30 s and dry for 5 s.
Sodium ascorbate gel^a  (Prepared soon before use)	10% Sodium ascorbate, purified water, carbopol gel (2.5% [wt/wt]), thriethanolamine, pH = 7.0	Apply and leave for 15 min (G15); 30 min (G30); or 60 min (G60); At the end of the procedure, wash for 30 s and dry for 5 s.
Adper Single Bond 2 (N368478BR)	BisGMA, HEMA, dimetacrilates, ethanol, water, silica	35% acid etching (30 s); Wash for 30 s and dry for 5 s; Actively apply two layers of adhesive (20 s); Air dry for 10 s; Light cure for 10 s at 1200 mW/cm^2.
Filtek Z350 XT (82736B)	Bis-GMA,UDMA, TEGDMA, Bis-EMA, silica-zirconia nanoparticles	Insert increments of 2 mm; Light cure for 20 s at 1200 mW/cm^2 Repeat the procedure 3X, until the restoration is completed (6 mm).

a Prepared according to Kimyai and Valizadeh[11] (2006); Bis-GMA (bisphenolglycidyl methacrylate); HEMA (2-hydroxyethyl methacrylate); UDMA (urethane dimethacrylate); TEGDMA (triethylene glycol dimethacrylate); Bis-EMA (bisphenolglycidyl ethyl-methacrylate).

Figure 1. Mean bond strength values (in Mpa) for the experimental groups; *statistically different (p < 0.05).

Table 2. Mean microtensile bond strength (standard deviations) in MPa for the different experimental conditions .

Group	Mean (standard deviation)
GP (+ Control)	26.0 (±6.0)^a
GN (− Control)	15.0 (±5.5)^b
G15 min	23.0 (±7.3)^a
G30 min	25.0 (±6.1)^a
G60 min	25.0 (±5.1)^a

The same lowercase letters indicates statistical similarity (p >0.05).

Table 3. Fracture modes of specimens and their representative percentages (%).

Group	Adhesive Fractures	Mixed Fractures	Cohesive Fractures	Premature Failures	Total
GP (+ control)	10 (23.8%)	28 (66.7%)	0	4 (9.5%)	42 (100%)
GN (− control)	2 (5%)	28 (70%)	0	10 (25%)	40 (100%)
G15 min	13 (26.5%)	30 (61.3%)	0	6 (12.2%)	49 (100%)
G30 min	7 (15.9%)	34 (77.3%)	1 (2.3%)	2 (4.5%)	44 (100%)
G60 min	6 (15%)	32 (80%)	1 (2.5%)	1 (2.5%)	40 (100%)
Total	38 (17.7%)	152 (70.7%)	2 (0.9%)	23 (10.7%)	215 (100%)

Kimyai S, Valizadeh H. The effect of hydrogel and solution of sodium ascorbate on bond strength in bleached enamel. Oper Dent. 2006;31:496–499.

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