Elisa Magni

Effect of intermediate agents and pre-heating of repairing resin on composite-repair bonds

This study investigated the composite-to-composite microtensile bond strength and interfacial quality after using different combinations of intermediate agents and pre-curing temperatures of repairing resin. Forty-five composite discs (8x4 mm) of Gradia Direct Anterior (GC Corp), stored in a saline solution at 37 degrees C for one month, were sandblasted (50 microm aluminum oxide), cleaned (35% phosphoric acid) and randomly divided into three groups (n=15) according to the intermediate agent applied: (1) no treatment; (2) unfilled resin (Scotchbond Multi-Purpose Adhesive, 3M ESPE); (3) flowable composite (Gradia LoFlo, GC Corp). Each disc was incrementally repaired (8x8 mm) with the same resin as the substrate. For each group, three subgroups (n=5) were created, depending on the pre-curing temperature of the repairing resin-4 degrees C, 23 degrees C or 37 degrees C. Two bonded specimens per group were prepared to evaluate the composite-to-composite interfacial quality via scanning electron microscope. Microtensile bond strength measurements were performed with the remaining three specimens and failure mode was examined by stereomicroscopy. Two-way ANOVA revealed that temperature (p < 0.001), intermediate agent (p < 0.001) and the interaction (p = 0.002) significantly affected the repair strength. Post-hoc comparisons revealed that bond strengths were significantly lower using a 4 degrees C repairing resin in groups where intermediate agents were used. The highest bond strengths were recorded when flowable composite was used as an intermediate agent under each of the three temperature conditions. Interfacial quality improved by raising the resin temperature from 4 degrees C to 37 degrees C.

SEM and microleakage evaluation of the marginal integrity of two types of class V restorations with or without the use of a light-curable coating material and of polishing

OBJECTIVES To evaluate the marginal integrity of class V restorations through an SEM observation and a microleakage test. METHODS Teeth with class V cavities were restored with either a flowable composite (n=20) or a glass ionomer cement (GIC) (n=20). Ten restorations in each group were immediately polished. A coating agent was applied on five polished and five non-polished restorations of each group. No coating was used on the remaining specimens. Epoxy resin replicas of the restorations were observed under a SEM and the percentage of marginal gaps was calculated. After immersion in a 2% methylene blue solution, three sections were obtained from each specimen and observed under a stereomicroscope. Occlusal and gingival microleakage were evaluated with a four-steps scoring system. The percentages of marginal gaps and the microleakage scores were analyzed with the Kruskal-Wallis ANOVA and the Mann-Whitney test with Bonferronis correction. Occlusal and gingival microleakage were compared with the Wilcoxon test. RESULTS No gaps were detected after coating. The restorative materials did not differ in interfacial gaps. Immediate polishing increased the gaps of uncoated restorations (p<0.05). The microleakage decreased with coating, except for occlusal wall of polished flowable composite restorations. After coating, the occlusal microleakage was higher than the gingival (p<0.05), except for non-polished flowable composite restorations. After polishing and coating, the flowable composite showed higher occlusal microleakage than the GIC. The polishing increased the occlusal microleakage of coated flowable composite restorations. CONCLUSIONS The coating procedure is advisable for restoring marginal integrity and reducing gingival microleakage in class V restorations.

Effect of ozone gas application on the mechanical properties of dental adhesives bonded to dentin

OBJECTIVES To assess the effect of ozone gas on the mechanical properties of different classes of dental adhesives. METHODS Extracted molars were sectioned perpendicularly to their long axis for obtaining dentin slices to be bonded with one of the following adhesives: Prime&Bond NT (Dentsply), Excite (Ivoclar-Vivadent), Syntac/Heliobond (Ivoclar-Vivadent) and Silorane System Adhesive (3 M-ESPE). Prior to bonding, the slices were sectioned in two halves: one was treated with ozone gas for 120 s (4.2g/m3; HealOzone, KaVo) and the other served as control. The Vickers hardness (VH), elastic modulus (E), elastic work (We/Wtot) and the creep (Cr) of the materials were measured with an automatic micro hardness indenter (Fischer) 30 min and 24 h after bonding procedure. Data were analyzed with the multivariate ANOVA followed by the Tukeys test and partial eta-squared statistics. RESULTS The adhesive and the time of testing were significant factors affecting the investigated parameters (p<0.001; etap2>or=0.06). Dentin treatment, though significant, exerted a minimal effect on mechanical properties (etap2<or=0.01). Ozone did not consistently affect the mechanical properties at both, 30 min and 24 h measurements, as all variations were below 10%. Small differences between ozone and control resulted only in the Cr and We/Wtot of Excite and in the VH of the Silorane System Adhesive at the 30 min measurement; and in the We/Wtot, Cr and VH of the Syntac/Heliobond system after 24h. SIGNIFICANCE Ozone gas did not compromise the mechanical properities of the tested adhesives. Thus, its application on dentin prior to bonding procedures is possible, without impairing the performance of the final restoration.

Post space debridement in oval-shaped canals: the use of a new ultrasonic tip with oval section.

This study evaluates the effect on post space debridement in oval-shaped canals of an experimental ultrasonic tip with oval section (Satelec) compared with a circular ultrasonic tip (KaVo). Thirty teeth with an oval-shaped canal were endodontically treated and obturated and then randomly divided into 3 groups (n = 10) according to the procedure used for post space debridement: Satelec tip, Largo #2 drill + KaVo file, and Largo #2 drill + water. Debris and dentin tubules were evaluated by assigning scores to scanning electron microscope post spaces images; lower scores corresponded to fewer debris and higher number of open tubules. The Satelec group showed significantly lower debris and open tubules scores than KaVo group (p < .05) and control group (p < .05), which differed significantly between each other (p < .05). Also the debris and open tubules scores in different post space regions differed significantly among the experimental groups (p < .001). The oval ultrasonic tip resulted in a better post space debridement than a circular ultrasonic tip in oval-shaped canals.