Depth of cure of proximal composite resin restorations using a new perforated metal matrix.

The purpose of this study was to compare the depths of cure of a proximal box preparation filled in bulk with various approaches: filled with a bulk-fill or conventional composite; placed with a new perforated metal matrix, a traditional metal matrix, or a clear matrix; and polymerized with either occlusal-only or tri-sited light curing. After tri-sited curing, the use of the new perforated metal matrix band resulted in a depth of cure that was not significantly different from that achieved with the use of metal bands (removed during curing) or transparent matrix bands. Adequate polymerization was obtained at depths of more than 5.0 mm for the bulk-fill composite and more than 4.0 mm for the conventional composite when tri-sited light curing was used. Tri-sited light curing resulted in a significantly greater depth of cure than occlusal-only curing. The perforated metal band may be used as an alternative to the use of solid metal bands or transparent matrix bands to provide similar depths of cure for composite resins, with the possible benefits of malleability and the ability to leave the band in place during tri-sited light curing.

Microleakage and shear bond strength of a new sealant containing prereacted glass ionomer particles.

A new fluoride-releasing sealant system is claimed to allow easier and faster placement while providing high bond strengths without the need for phosphoric acid etching. A study was designed to compare the microleakage and shear bond strength of a self-etching, Giomer-based sealant system with those of a traditional resin sealant. Group 1 received traditional sealant applied after use of a 35% phosphoric acid etchant; group 2 received Giomer sealant after use of a self-etching primer; and group 3 received Giomer sealant after the addition of an initial phosphoric acid etching step and placement of the primer. The sealants were placed in the occlusal pits and fissures of extracted human third molars, thermocycled, placed in dye, and sectioned. The extent of microleakage (dye penetration) was expressed as a percentage of the cross-sectional length of the sealed interface. The sealants were also bonded to the facial enamel of bovine incisors. Specimens were thermocycled and tested in shear mode in a universal testing machine. The new self-etching sealant demonstrated significantly greater microleakage (P < 0.017) and lower bond strength (P < 0.05) than both the traditional sealant system and the new system when placed with phosphoric acid etchant. Phosphoric acid etching significantly improved the shear bond strength and reduced the microleakage of the new sealant.

Effect of surface treatments on the mechanical properties and antimicrobial activity of desiccated glass ionomers.

OBJECTIVES: The purpose of this study was to evaluate the effect of various surface treatments on the mechanical properties and antibacterial activity of desiccated glass-ionomer (GI) and resin-modified glass-ionomer (RMGI) materials. METHODS: One hundred GI and RMGI specimens were fabricated in a mold, stored in 100% humidity for 24h, placed in air to desiccate for 24h, and then stored for one week in one of the five media [casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), chlorhexidine (CHX), sodium fluoride (NaF), cetylpyridinium chloride (CPC), or 100% humidity (control)]. Fifty GI and RMGI specimens were tested in flexure to determine flexural strength and modulus, with the fragments used for Knoop hardness testing. The remaining 50 GI and RMGI specimens were covered with a suspension of Streptococcus mutans and incubated for 24h. The bacterial suspension was removed and the specimens were washed. Sterile saline was added, vortex mixed, serially diluted, and plated. CFU/mLs were calculated after 3days of incubation. RESULTS: Compared to the 100% humidity control group, surface treatment of the desiccated GI and RMGI materials had a variable effect on the mechanical properties. In general, NaF provided the greatest improvement in flexural strength and modulus. Surface treatment of the desiccated GI or RMGI specimens with CHX or CPC resulted in no growth of the S. mutans. NaF resulted in significantly lower CFU/mL than CPP-ACP, which was significantly lower than the control group. SIGNIFICANCE: Surface treatment with 5% NaF provides improved antimicrobial and strength properties of desiccated GI or RMGI materials.

Effect of a new salivary-contaminant removal method on bond strength.

The study evaluated the effect of salivary-contaminant removal methods on the bond strength of resin cement to hydrofluoric acid-etched ceramic. Treatment with a new cleaning paste resulted in bond strengths not significantly different from those obtained in phosphoric acid-treated, hydrofluoric acid-treated, and uncontaminated control groups; thus the paste may be considered an alternative to phosphoric acid or hydrofluoric acid for removal of salivary contaminants.