Seeing is believing? When scanning electron microscopy (SEM) meets clinical dentistry: The replica technique.

In restorative dentistry, the in situ replication of intra-oral situations, is based on a non-invasive and non-destructive scanning electron microscopy (SEM) evaluation method. The technique is suitable for investigation restorative materials and dental hard- and soft-tissues, and its interfaces. Surface characteristics, integrity of interfaces (margins), or fracture analysis (chipping, cracks, etc.) with reliable resolution and under high magnification (from ×50 to ×5,000). Overall the current study aims to share detailed and reproducible information about the replica technique. Specific goals are: (a) to describe detailed each step involved in producing a replica of an intra-oral situation, (b) to validate an integrated workflow based on a rational sequence from visual examination, to macrophotography and SEM analysis using the replica technique; (c) to present three clinical cases documented using the technique. A compilation of three clinical situations/cases were analyzed here by means the replica technique showing a wide range of possibilities that can be reached and explored with the described technique. This guidance document will contribute to a more accurate use of the replica technique and help researchers and clinicians to understand and identify issues related to restorative procedures under high magnification.

Water sorption and water solubility of current luting cements: an in vitro study.

OBJECTIVE: To evaluate the water-sorption characteristics and the solubility behavior of 4 luting cements-2 composite resins (CRs), a polyacid-modified composite resin (PMCR), and a resin-modified glass-ionomer cement (RMGIC)-according to the ISO 4049 specifications. METHOD AND MATERIALS: Five disks (15 x 1 mm) of each material (Variolink II [CR1; Vivadent], Panavia F [CR2; Kuraray], Resinomer [PMCR; Bisco], and Fuji Plus [RMGIC; GC]) were prepared according to the manufacturers' instructions. Specimens were first desiccated until a consistent mass was obtained. Specimens were immersed for 7 days in distilled water and immediately weighed after this period. Then the disks were post-desiccated and weighed every day for 35 days. The water sorption and solubility of each specimen were calculated according to the change in its weight as observed before and after immersion and desiccation periods. RESULTS: Fuji Plus exhibited the overall higher values of water sorption and solubility (P < .001). Of the 3 resin-based luting cements, Resinomer demonstrated significantly higher water sorption and solubility (P < .001), whereas Variolink II and Panavia F showed low values and were not significantly different (P = .2). CONCLUSIONS: Behavior of resin-based materials in water varies according to the composition characteristics. In particular, the high portion of hydrophilic chemical species, as well as the filler characteristics, provoke very high water sorption and solubility values. In this way, and within the limitations of this in vitro study, composite resin luting cements appear to be more suitable than compomers and resin-modified glass-ionomer cements to meet longevity requirements.

Microleakage and polymerization shrinkage of various polymer restorative materials.

PURPOSE: The aim of this in vitro study was to evaluate the polymerization shrinkage and the microleakage of direct resin-based restorative materials commonly used in pediatric dentistry. METHODS: Standardized Class V cavities overlapping the cementoenamel junction were prepared on the buccal and the lingual surfaces of 40 extracted human mandibular third molars (36 specimens, 4 controls). The cavities were restored with 4 different materials: a packable resin composite (Filtek P60), a compomer (Compoglass F), an ormocer (Admira) and their associated bonding agents (Scotchbond 1, Excite, and Admira Bond, respectively), and a resin-modified glass ionomer (Fuji II LC). The teeth were then immersed in methylene blue solution for 48 hours. Dye penetration was evaluated for all materials, which were analyzed using a multivariate model (alpha=0.05): influence of microleakage score, margin location (enamel/cementum), and preparation location (buccal/lingual). Multivariate analysis was performed using a polychotomous logistic regression. Polymerization shrinkage was evaluated by the disk deflective method. The percentage of polymerization shrinkage (N=3) was evaluated by ANOVA and Tukey test. RESULTS: Regarding polymerization shrinkage, the P60 demonstrated the lowest value, followed by ADM and COF, whereas FLC presented the highest shrinkage-strain (P<.0001). The preparation location had no significant effect on dye penetration (P=.86). Margin location (enamel or cementum) had a significant effect on microleakage (odds ratio [OR]=24.61). Significant differences in the microleakage patterns and scores were also observed between the 4 restorative materials. Admira exhibited the lowest overall microleakage. In comparing Filtek P60, Compoglass F, and Fuji II LC to Admira, P60 showed significantly less microleakage (OR=1.30) than Fuji II LC (OR=1.47), whereas Compoglass F demonstrated the greatest significant overall microleakage (OR=3.15). CONCLUSION: Within the experimental conditions of this in vitro study, the microleakage was significantly lower at the enamel margins than at the cementum margins for the four restorative materials tested. The ormocer and the packable resin composite exhibited the best sealing ability, as well as the lowest polymerization shrinkage. It could not be demonstrated in this study, however, that the higher the polymerization shrinkage was, the lower the marginal sealing ability was.

Importance of water sorption and solubility studies for couple bonding agent--resin-based filling material.

This study investigated the water sorption and solubility of two light-cured resin composites (Filtek P60 and Solitaire 2), one compomer (Compoglass F), one ormocer (Admira) and the associated bonding agents (Scotchbond 1 [Scotchbond 1 = Scotchbond Single Bond in USA], Gluma One Bond, Excite and Admira Bond, respectively) and of a RMGIC (Fuji II LC). Five disks of each product type were subjected to water sorption and solubility tests based on ISO 4049 requirements. The data were subjected to Kruskal-Wallis and non-parametric multiple-comparison tests using ranked sums at 95% confidence interval. Fuji II LC showed the highest water sorption (167.5 microg/mm(-3)). Fuji II LC and Compoglass F had higher solubility values (8.3 and 10.0 microg/mm(-3), respectively) than the other materials. Bonding agents have very high water sorption and solubility values (between 77.4 and 355.4 microg/mm(-3) and between 75.9 and 144.9 microg/mm(-3), respectively) compared to the restorative materials. Gluma One Bond and Admira Bond showed lower sorption and solubility than Excite and Scotchbond 1.