Effect of Adhesive Restoration and Bleaching Technique on the Concentration of Hydrogen Peroxide In the Pulp Chamber.

This study aimed to quantify the concentration of hydrogen peroxide into the pulp chamber in the presence or absence of adhesive enamel restorations and to analyze the resin-dentin interface of bleached groups. Bovine incisors (120) were randomly divided into three groups according to enamel treatment (n=40 each): (1) enamel without restoration (control); (2) enamel cavities (3 mm diameter × 1.5 mm depth) restored with a silorane-based (SB) system; or (3) enamel cavities (3 mm diameter × 1.5 mm depth) restored with a dimethacrylate-based (DB) system. Restorations were thermocycled, and all groups were submitted to one application of 35% hydrogen peroxide (HP) agent for 45 minutes and subjected to four light activation methods (n=10 each): without light, light-emitting diode (LED), LED/diode laser, or halogen light. Acetate buffer solution was placed into the pulp chamber before bleaching, and this solution was collected to spectrophotometrically determine the concentration of HP that reached the pulp chamber after bleaching. Rhodamine B was added to the HP agent and applied on additional enamel samples of each group for 24 hours. Samples were sectioned mesiodistally, and the bleaching agent was traced using confocal microscopy. According to two-way analysis of variance and Tukey test (α=0.05), the HP concentration in the pulp chamber of the control group was significantly lower than that of the SB group (p<0.05), regardless of light activation. No differences were observed between DB and SB groups and between control and DB groups, except for the DB halogen light activated group, which exhibited higher HP intrapulpal concentration (p<0.05). Confocal microscopy exhibited HP diffusion through the interface of the SB and DB restored groups as well as enamel prisms in the control group. The SB restorative system increased the HP diffusion into the pulp chamber, but HP was able to diffuse even in the absence of enamel restorations.

Microshear bond strength of preheated silorane- and methacrylate-based composite resins to dentin.

The aim of this study was to investigate the effect of preheating on microshear bond strength (MSBS) of silorane and methacrylate-based composite resins to human dentin. The teeth were randomly divided into three main groups: (1) composite resins were heated upto 68 °C; (2) cooled to 4 °C; and (3) control [room temperature (RT)]. Each group was then randomly subdivided into four subgroups according to adhesive system used [Solobond M (Voco), All Bond SE (Bisco), Clearfil SE Bond (CSE) (Kuraray), Silorane adhesive system (SAS) (3M ESPE)]. Resin composite cylinders were formed (0.9 mm diameter × 0.7 mm length) and MSBS of each specimen was tested. The preheated groups exhibited the highest MSBS (p < 0.001) and the groups cooled to 4 °C exhibited the lowest MSBS (p < 0.001). The CSE showed higher MSBS than the other adhesives (p < 0.001). This study concludes that preheating of composite resins may be an alternative way to increase the MSBS of composites on dentin.

Effect of using silorane-based resin composite for restoring conservative cavities on the changes in cuspal deflection.

OBJECTIVE: To investigate the effect of using two resin-composite materials for restoring conservative mesio-occluso-distal (MOD) cavities on the changes (incremental and cumulative) in cuspal deflection. METHODS: Forty extracted sound human maxillary second premolars were subjected to standardized MOD cavity preparation and then divided into two groups (n=20). The first group of teeth was restored with Filtek Z250 (3M ESPE, St Paul, MN, USA), and Filtek P90 (3M ESPE, St Paul, MN, USA) was used in the second group. Incremental cuspal deflection was calculated by measuring the intercuspal distance between the indexed cusp tips before the restoration and at five-minute intervals up to 30 minutes using a stereomicroscope connected to a digital camera. Cumulative cuspal deflection for both materials was also calculated. RESULTS: Comparing the incremental cuspal deflection of the tested groups at each time interval, it was found that there was no significant difference immediately after curing and at five, 15, 20, and 25 minutes. However, a significant difference was recorded at 10 and 30 minutes. For the cumulative cuspal deflection, Filtek P90 showed significantly lower deflection values than Filtek Z250 only after five minutes. CONCLUSIONS: Incremental cuspal deflections of both materials over the tested intervals were almost comparable. However, after five minutes of curing, silorane-based resin composite surpassed the methacrylate-based resin composite in controlling the cumulative cuspal deflection.