Resin composite shrinkage and marginal adaptation with different pulse-delay light curing protocols

The aims of this study were, first, to measure shrinkage induced by different methods of pulse-delay light curing and, second, to verify their influence on the marginal adaptation of class V restorations in enamel and dentin. Eight groups, comprising seven groups (n = 6) with different pulse-delay parameters and a control group, were compared for dynamic linear displacement and force by using a fine hybrid composite. Based on these results, the pulse-delay curing procedure with the lowest shrinkage force was chosen and tested against the control group with respect to marginal adaptation in class V restorations (n = 8) before and after simultaneous thermal and mechanical loading. Statistically significant differences between groups were found for both shrinkage properties tested, with one pulse-delay group giving the lowest overall shrinkage values. However, the percentages of 'continuous margin' of this group, and of the control before and after loading, were not significantly different in dentin, whereas a significantly lower percentage of 'continuous margin' was detected in the pulse-delay group in enamel after loading. © Eur J Oral Sci, 2005

Fluorescence intensities of composite resins on photo images

Recording fluorescence using flash photography, may help reduce time of capture and apply effectively in clinical practice. To test methods for visualizing composite resins fluorescence by direct digital photography. Sixty-four specimen discs (1.5 × 10 mm) were prepared from 8 different composite resin brands. Their CIELAB color coordinates (L*, a*, b*) and fluorescence were measured using a portable colorimeter and a fluorescence spectrophotometer. The mean of three measurements was recorded and then specimens were photographed by a DSLR camera with two different filters (365 nm and 405 nm) mounted on a commercial macro flash. RGB values of all specimens on the photographs were measured by using Photoshop software and converted to CIELab. Data were then analyzed using Kruskal–Wallis and Dunn’s multiple comparisons tests. Correlation and regression analyses were also used to relate fluorescence and color parameters on the photographs at α = 0.05. Fluorescence and color data indicated significant differences among the materials (p < 0.05). L* a* and b* color coordinates from both photographs were highly correlated to fluorescence intensities found by the reference method (r365 − 0.95, r405 − 0.94), while regression analysis indicated a strong linear relationship (R2365 − 0.88, R2405 − 0.89). The study showed that filtered flash photography either by the use of a 365 nm or a 405 nm band pass filter can directly visualize fluorescence of composite resin materials and differences in fluorescence between them. © 2021, The Author(s)

Polymerization shrinkage of flowable resin-based restorative materials

This study measured the linear polymerization displacement and polymerization forces induced by polymerization shrinkage of a series of flowable resin-based restorative materials. The materials tested were 22 flowable resin-based restorative materials (Admira Flow, Aelite Flow, Aeliteflow LV, Aria, Crystal Essence, Definite Flow, Dyract Flow, Filtek Flow, FloRestore, Flow-it, Flow-Line, Freedom, Glacier, OmegaFlo, PermaFlo, Photo SC, Revolution 2, Star Flow, Synergy Flow, Tetric Flow, Ultraseal XT and Wave). Measurements for linear polymerization displacement and polymerization forces were performed using custom made measuring devices. Polymerization of the test materials was carried out for 60 seconds by means of a light curing unit, and each property was measured for 180 seconds from the start of curing in eight specimens for each material. Statistical evaluation of the data was performed with one-way analysis of variance (ANOVA), Tukey's Studentized Range (HSD) test (p=0.05) and simple linear regression. A wide range of values was recorded for linear polymerization displacement (26.61 to 80.74 microns) and polymerization forces (3.23 to 7.48 kilograms). Statistically significant differences among materials were found for both properties studied. Very few materials (Freedom, Glacier, and Photo SC) presented low values of linear polymerization displacement and polymerization forces (similar to hybrid resin composites), while the majority of materials presented very high values in both properties studied. Study of the shrinkage kinetics revealed the exponential growth process of both properties. The polymerization forces development exhibited a few seconds delay over linear polymerization displacement. Simple linear regression showed that the two polymerization shrinkage properties that were studied were not highly correlated (r2=0.59)

Degree of remaining C=C bonds, polymerization shrinkage and stresses of dual-cured core build-up resin composites

This study measured the degree of remaining C=C bonds (RDB), linear polymerization shrinkage (LPS) and polymerization stresses (PS) of dual-cured resin composite build-up materials using a variety of light exposure scenarios. Four commercially available materials were used: Bis-Core, FluoroCore, Build-it! and Permalute. The RDB was measured using FTIR spectroscopy, and custom-made devices were used to measure LPS and PS values. Data were obtained using three different modes of photoactivation: NLC (No Light-Curing); ILC (Immediate Light-Curing, where 60 second light-curing was applied at the start of the observation period); and DLC (Delayed Light-Curing, where 60-second light-curing was applied 10 minutes from the start of the observation period). Statistical evaluation of the data at the end of the 13-minute observation period was performed with two-way analysis of variance (ANOVA), Tukey's Studentized Range (HSD) Test (p=0.05) and simple linear regression. Differences in the development of LPS and PS during the 13 minutes were studied using mathematical calculus. Bis-Core presented the highest RDB and Permalute the lowest when ILC was applied, while no differences were found between Build-it! and FluoroCore and NLC and DLC increased RDB for FluoroCore and Permalute compared to ILC; whereas, no differences were noted for Build-it! and Bis-Core. Using DLC, a decrease in RDB was found only for Build-it! FluoroCore and Permalute exhibited a reduction in LPS and PS using NLC relative to ILC. No differences in LPS and PS values were detected for the materials Bis-Core and Build-it! when subjected to NLC or DLC, compared to ILC. Simple linear regression showed that only the two polymerization shrinkage properties studied were highly correlated (LPS-PS r2=0.85). The RDB rate was not correlated with either polymerization shrinkage properties (RDB-LPS r2=0.40; RDB-PS r2=0.57). A study of the evolution of the real-time curves of percentage values of LPS and PS showed that these properties evolved in a similar exponential mode and that, most often, there was a delay in the development of PS

Linear displacement and force induced by polymerization shrinkage of resin-based restorative materials

To measure the linear displacement and force induced by polymerization shrinkage of a series of resin-based restorative materials

Marginal integrity of pit and fissure sealants. Qualitative and quantitative evaluation of the marginal adaptation before and after in vitro thermal and mechanical stressing

This research quantitatively evaluated the marginal adaptation of pit and fissure sealants. The occlusal surfaces of 48 intact, caries-free human molars were cleaned with an air-abrasion unit. The teeth were then randomly divided into eight groups of six teeth each according to the type of enamel conditioning, sealant material applied and curing unit used. After applying either 40% phosphoric acid gel (K-etch, Kuraray Co) or a self-etching primer adhesive system (Clearfil SE Bond, Kuraray Co), sealant materials of two viscosities were applied (Teethmate F-1 and Protect-Liner-F, Kuraray Co) and cured with halogen (Optilux 500, Demetron) or plasma arc (Apollo-95E, Dental & Medical Diagnostic Systems, Ltd) curing units. The marginal adaptation of the pit and fissure sealant restorations was evaluated by using a computer-assisted quantitative margin analysis in a scanning electron microscope (SEM) on epoxy replicas before and after thermal and mechanical stressing of the teeth. The results were statistically analyzed with one-way analysis of variance (ANOVA) at a confidence level of 95% (p=0.05). A post-hoc Tukey HSD-test was used for multiple pairwise comparisons between groups. The null hypothesis was that there was no statistically significant difference between the groups that were tested in this study. The statistically significant differences between groups were more pronounced after loading. In most cases, the self-etching adhesive system (SE Bond) proved as effective as phosphoric acid etching (K-etch). The low viscosity sealant material (Teethmate F-1), in most cases, exhibited better marginal adaptation than the high viscosity material (Protect-Liner F). The high viscosity material performed equally well only when used in combination with the self-etching primer adhesive system as an intermediate layer. The halogen curing unit (Optilux 500) led to better marginal adaptation than the plasma arc curing unit (Apollo 95E), especially after thermal and mechanical stressing

A combined chemo-mechanical approach for aesthetic management of superficial enamel defects

OBJECTIVE: The aim of this article is to describe an easy technique for managing small superficial defects in light to medium fluorosis. METHOD AND MATERIALS: The proposed technique is based on a selective abrasion of the superficial enamel and a recreation of the superficial macro and micro morphology. The aesthetic appearance can be enhanced by power or home bleaching. RESULTS: The presented technique can manage enamel defects which are confined in the most external enamel surface with satisfying aesthetic results. CONCLUSIONS: This conservative approach may be considered an interesting alternative to more invasive prosthetic techniques based on composite reconstructions or ceramic veneers, minimising invasivity, chairside time and costs for patients