Piezoelectrically Mediated Reversible Addition-Fragmentation Chain Transfer Polymerization

A well-controlled piezoelectrically mediated reversible addition-fragmentation chain transfer polymerization (piezo-RAFT) was carried out under ultrasound agitation with piezoelectric ZnO nanoparticles as the mechano-chemical trans-ducer. The resulting polymer had predictable molecular weight, high end-group fidelity, low dispersity, and capacity for chain extension. This chemistry was further adopted in curing composite resins to circumvent the light penetration limit of UV curing. This work opened a new avenue of piezoelectrically mediated chemistry and showed its good potential in curing applications.

Evaluation of the Effect of Cold Plasma Treatment on the Microshear Bond Strength of Composite Resin Restorations to Dentin using Different Adhesive Systems and the Effect of Thermocycling

Introduction: Currently, non-thermal plasma is used to modify the enamel and dentin surfaces to improve the bonding surface to dental composite resins. Non-thermal plasma creates a hydrophilic surface, decreases the contact angle, and improves the bonding quality. The present study aimed to evaluate the microshear bond strength (µSBS) of composite resins to dentin using different adhesive systems. Materials and Methods: Bovine incisor teeth were randomly assigned to three groups of G-Premio, Clearfil SE Bond, and Adper Single Bond adhesive groups after preparation. Each group was divided into two subgroups in terms of argon plasma surface preparation, and each subgroup was divided into two groups in terms of thermocycling (n=12). The microshear bond strength of the samples was determined using a universal testing machine. Three-way ANOVA was used to analyze the effect of the adhesive, plasma preparation, and thermocycling. Post hoc Tukey tests were used for two-by-two comparisons of µSBS. Statistical significance was set at P <0.05. Results: The results of the µSBS test showed that the application of plasma resulted in a significant increase in the mean µSBS in the G-Premio group, with no significant increase in the Clearfil SE bond and Adper Single groups. The effect of thermocycling after plasma application was significant only in the Adper Single group. Conclusion: The application of plasma might increase the bond strength of composite resins to dentin. However, further studies are necessary.

Cytotoxic Effects of Bulk-Fill Composites on L929 Fibroblast Cells

Objective: Unlike traditional composite resins, bulk-fill composite resins could be polymerized as thicker layers. This study aims to contribute to the field by investigating the cytotoxic effects of various bulk-fill composite resins on L929 mouse fibroblast cells in vitro. Material and Methods: In our study, six bulk fill and one conventional composite resin were used. Composite resin samples (8×4 mm) were prepared in a sterile cabinet by using a glass mod and polymerizing with a led light device (DTE LUX E, Germany). Composite samples (n:3) of which surface area was calculated according to ISO 10993-12: 2012 standards (3 cm2/ml), were kept in media for 24 h and 72 h in 37 oC incubator, their extracts were filtered in 1:1 and 1:2 proportion and were added on L929 mouse fibroblast cells. Cell viability was examined by the MTT assay and cell death by the LDH test. Cell viability results were evaluated using one-way analysis of variance (ANOVA) test (p<0.05). Results: When the 1:1 extracts from 4 mm thick bulk-fill composite samples were applied on L929 mouse fibroblast cells, cell viability rates showed significant differences compared to the control group at the end of 24 h and 72 h (except for Estelite Bulk Fill Flow). Although the extracts of the tested composite samples at 1:1 and 1:2 ratio at the end of 72 hours caused a decrease in L929 mouse fibroblast cell viability, the cell viability rate of only PRG-containing bulk fill composite and conventional composite remained below the cell viability ratio (70%) specified in ISO standards. Bulk fill composites did not produce toxic effects (except Beautifil Bulk Restorative) according to the LDH test. Conclusions: Despite decreasing in general the cell viability, bulk-fill composite resins used in 4 mm thick layers provided cell viability rates over the acceptability level, except PRG-containing bulk fill composite (Beautifil Bulk Restorative), which was cytotoxic to L929 mouse fibroblasts. Keywords Bulk fill composite; Cytotoxicity; L929 cells; LDH assay.

Effect of Conventional and Electronic Cigarettes Smoking on the Color Stability and Translucency of Tooth Colored Restorative Materials: An In Vitro Analysis

This in vitro study compared the effects of conventional and electronic cigarettes on the aesthetics (color stability and translucency) of two types of composite resins: micro and nano-hybrid. Methods: A total of 120 specimens from two different composite materials Filtek Z250 XT (Nano-hybrid, 3M) and Filtek Z250 (Micro-hybrid, 3M) were divided into four groups (n = 30); shade A2 was used. The samples were exposed to conventional and electronic cigarette smoke via a custom made chamber device. The color values and measurements were recorded using a spectrophotometer before and after the exposure. The color and translucency were evaluated using the three-dimensional CIE Lab. Results: There was a significant change in the color (ΔE) and the translucency parameter (TP) in all of the specimens exposed to electronic cigarettes and conventional cigarettes. The results showed that the highest ΔE mean is for the nano-hybrid composite exposed to conventional cigarettes with 1.74 ΔE while the same material is 0.64 under the electronic cigarettes and the difference is significant with (p < 0.05). The micro-hybrid composite data showed less changes in color under both exposures with 0.85 ΔE mean under the conventional cigarette smoke and 0.48 under the electronic cigarette smoke with (p < 0.004). Conclusions: The conventional cigarette smoke has more effect on the color stability of the composite resins than electronic cigarettes. From a clinical point of view, the effect of smoke exposure on the tested specimens’ color, for the time duration to which the specimens were exposed, were moderate (ΔE < 2). The micro-hybrid composites showed better color stability as compared to the nano-hybrid composites.

The Thickness and Opacity of Aesthetic Materials Influence the Restoration of Discolored Teeth

SUMMARY Objectives: This study aimed to evaluate the influence of thickness and opacity on the ability of composite resin and ceramic veneer restorations to mask discolored teeth. Methods: Ninety veneers were made of lithium disilicate ceramic, shades BL1 and 0 (IPS e.max Press, Ivoclar Vivadent), and 60 were made of composite resin, shade BL-L (IPS Empress Direct, Ivoclar Vivadent). The veneers measured 4 mm in width x 4 mm in length and had a thickness of 0.7, 1.0, or 1.2 mm. One hundred and fifty human premolars were selected to obtain 150 dental fragments with the following dimensions: 4 mm x 4 mm x 3 mm (width x length x thickness). The fragments were discolored, submitted to color measurement and randomly assigned to 15 groups (n=10) according to the type and opacity of the restorative material (IPS e.max Press: high translucency [HT], low translucency [LT], and medium opacity [MO]; IPS Empress Direct: dentin and enamel) and thickness of the veneers (0.7, 1.0, and 1.2 mm). After cementation of the ceramic or composite resin veneers using a translucent resin cement (RelyX veneer, 3M), a final color measurement was taken from each specimen and the total color variation (ΔE) was calculated by subtracting the initial and the final color measurement. The final lightness (L*) of the restored dental fragments was also calculated. Results: The highest ΔE values were observed for the LT and MO ceramic groups, followed by dentin composite resin. Regarding the different thicknesses of ceramic veneers, every 1.2-mm–thick group had higher values of ΔE, considering their respective opacities (p&lt;0.05). The highest lightness values were found for the LT and MO ceramic veneers (thickness of 1.2 mm). Dentin-shade composite resins showed similar lightness values in all groups. Conclusion: The best thickness/opacity combinations for masking discolored dental substrates were LT and MO ceramic veneers with 1.2-mm thickness. Dentin-shade composite resin veneers with a thickness of 0.7–1.0 mm showed good ability to mask discolored dental substrates.

Pink Resin as an Alternative for Restoration of Cervical Lesions Associated with Gingival Recession: a Case Report

Gingival recession occurs when the gingival margin is located apically to the cementoenamel junction, causing root exposure. This work aims to report a clinical case of restorative treatment of multiple non-carious cervical lesions (NCCL´s) with gingival-colored resin, as an alternative approach of restorative procedure in cervical defects associated with gingival recession in the aesthetic area. A patient attended a Clinical-School complaining several NCCL´s in addition to Miller's class I gingival vestibular recession in the elements: 13, 21, 22 and 23. Dentin hypersensitivity was absent, however, aesthetic appearance bothered the patient. Presence of occlusal interferences, acid feeding and inadequate brushing habits were observed as important etiological factors for NCCL´s and gingival recessions. Periodontal surgery would be the treatment of choice, however, the patient needed orthodontic intervention first to promote dental alignment and correct distribution of the occlusal load. In order to decrease the progression of the lesions during the orthodontic treatment the NCCL´s associated with gingival recession were restored with gingival-colored resin. Two colors of pink composite resin (color G3 and G5) were incrementally inserted, promoting a correct emergence profile, taking the resin to the lower cavity limit avoiding aggression to the periodontal tissue. Clinical follow-up of 22 months was favorable due to the appearance of restorations and satisfactory periodontal health. Gingival resin can be assigned to improve the aesthetic effect of the restoration at a low cost and time-saving. Keywords: Gingival Recession. Tooth Wear. Composite Resins. ResumoA recessão gengival ocorre quando a margem gengival está localizada apicalmente à junção cemento-esmalte, causando exposição radicular. Este trabalho tem como objetivo relatar um caso clínico de tratamento restaurador de múltiplas lesões cervicais não cariosas (LCNC´s) com resina de cor gengival, como uma forma alternativa de procedimento restaurador em defeitos cervicais associados a recessão gengival em área estética. Uma paciente buscou atendimento odontológico em um centro especializado por apresentar várias lesões do tipo LCNC, além de recessão gengival vestibular classe I de Miller nos elementos: 13, 21, 22 e 23 que não apresentavam sensibilidade, porém eram lesões que a incomodava quanto ao fator estético. Foram observados importantes fatores etiológicos para as LCNC’s e recessões gengivais, como a oclusão desarmônica, alimentação ácida e hábitos de escovação inadequados. A cirurgia periodontal seria o tratamento de primeira escolha, contudo havia a necessidade de intervenção ortodôntica primeiramente para promover alinhamento dentário e correta distribuição das forças oclusais. Com o intuito de diminuir a progressão das lesões durante o tratamento ortodôntico optou-se por restaurar as LCNC´s associadas à recessão gengival com resina composta caracterizada para gengiva. Foram utilizadas 2 cores de resina rosa (G3 e G5) de forma incremental, até o limite inferior da cavidade, promovendo um correto perfil de emergência e evitando agressão aos tecidos periodontais. Acompanhamento clínico de 22 meses mostrou um aspecto favorável das restaurações assim como boa saúde periodontal. Dessa forma, a resina do tipo gengival pode ser indicada para melhorar o efeito estético da restauração a um baixo custo e rapidez no procedimento. Palavras-chave: Retração Gengival. Desgaste dos Dentes. Resinas Compostas.