Triacrylamide-Based Adhesives Stabilize Bonds in Physiologic Conditions

In this study, an acrylamide-based adhesive was combined with a thiourethane-based composite to improve bond stability and reduce polymerization stress, respectively, of simulated composite restorations. The stability testing was conducted under physiologic conditions, combining mechanical and bacterial challenges. Urethane dimethacrylate was combined with a newly synthesized triacrylamide (TMAAEA) or HEMA (2-hydroxyethyl-methacrylate; control) to produce a 2-step total-etch adhesive system. Methacrylate-based composites (70 wt% silanized filler) were formulated, containing thiourethane oligomers at 0 (control) or 20 wt%. Standardized preparations in human third molars were restored; then, epoxy replicas were obtained from the occlusal surfaces before and after 7-d storage in water or with Streptococcus mutans biofilm, which was tested after storage in an incubator (static) or the bioreactor (mechanical challenge). Images were obtained from the replicas (scanning electron microscopy) and cross sections of the samples (confocal laser scanning microscopy) and then analyzed to obtain measurements of gap, bacterial infiltration, and demineralization. Microtensile bond strength of specimens stored in water or biofilm was assessed in 1-mm2 stick specimens. Data were analyzed with analysis of variance and Tukey’s test (α = 0.05). HEMA-based materials had greater initial gap measurements, indicating more efficient bonding for the acrylamide materials. When tested in water, the triacrylamide-based adhesive had smaller gaps in the incubator or bioreactor. In the presence of biofilm, there was less difference among materials, but the acrylamide/thiourethane combination led to statistically lower gap formation in the bioreactor. HEMA and TMAAEA-based adhesives produced statistically similar microtensile bond strengths after being stored in water for 7 d, but after the same period with biofilm-challenged specimens, the TMAAEA-based adhesives were the only ones to retain the initial bond strength values. The use of a stable multiacrylamide-based adhesive led to the preservation of the resin-dentin bonded interface after a physiologically relevant challenge. Future studies will include a multispecies biofilm model.

Dual-cured adhesive system improves adhesive properties of dentin cavities restored with a bulk-fill resin composite

Aim: To evaluate the impact of a dual-cured adhesive system on the in situ degree of conversion (DC), bond strength (BS) and failure mode (FM) of adhesive interfaces in dentin cavities restored with a bulk-fill resin composite. Methods: 4-mm-deep dentin cavities with a 3.1 C-factor were created in 68 bovine incisors (n = 17 per group). The lightcured (Scotchbond™ Universal) or the dual-cured (Adper™ Scotchbond™ Multi-purpose Plus) adhesive system was applied to the cavities, which were then restored with a bulkfill resin composite (Filtek™ Bulk Fill). In situ DC analysis was performed by means of micro Raman spectroscopy at the top and bottom interfaces. Push-out BS was measured in a universal testing machine after 24-h or 6-month water storage. FM was determined with a stereomicroscope. Data of in situ DC and BS were analyzed by two-way analysis of variance (ANOVA) and Tukey test (p<0.05), while the FM was analyzed descriptively. Results: The groups that received the dual-cured adhesive system showed statistically higher in situ DC and BS than those that received the light-cured adhesive system. Cohesive failure mode was the most frequent in all conditions. Conclusion: In situ DC and BS were influenced by the curing strategies of the adhesive systems with better performance of the dual-cured material.

EFEK GENOTOKSISITAS PADA BAHAN DENTAL ADHESIF

The use of dental adhesive materials in dental practice everyday has raised questions about the biological effects on tissues. Adhesive system has attracted considerable research interest in recent years, dental adhesive will succeed depends on the chemical adhesive, on the appropriate clinical management of materials and the knowledge of morphological changes in dental tissue caused by different bonding procedures. Some studies suggest that the dental adhesive material Genotoxicity have any effect on the network. Genotoxic effects may significantly reduce the potential for tissue repair or cause the development of neoplasia in the long term.

Effect of Saliva/Blood Contamination on Enamel Bond Strength

In the routine clinical situation, the contamination by blood and/or saliva in restorative procedures can be happen in non-cooperation of the patient in dental office. The aim of the study was to assess in vitro shear bond strength of a resin sealant associated with two types of adhesives contaminated with saliva and blood. Healthy human molars were used and the specimens and the crowns were sectioned in the bucco-lingual direction, thus obtaining two segments of similar proportions (mesial and distal), totaling 60 surfaces, and the surfaces were randomly divided into 4 groups (n = 15). Group I (control) received no type of contamination and the sealant was applied. In group II, the surfaces were contaminated with 10 μl of saliva/blood and the sealant was applied. In group III, the surfaces were contaminated with 10 μl of saliva/blood and the Single Bond total-etch adhesive system was applied followed by application of sealant. In group IV, the surfaces were contaminated with 10 μl of saliva/blood and the Prime & Bond NT total-etch adhesive system was applied followed by the application of sealant. Samples were tested in the universal testing machine and the analysis of shear bond strength was performed. A difference between Group I (12.61MPa) and the other groups was found; Group II (2. 28MPa) was different than Groups III (7.07MPa) and IV (7.79MPa), but Groups III and IV were similar. The application of an adhesive system when there is contamination with saliva/blood is required prior to application of pit and fissure sealants. Keywords: Pit and Fissure Sealants. Biological Contamination. Shear Strength. ResumoNa situação clínica de rotina, a contaminação por sangue e/ou saliva em procedimentos restauradores pode ocorrer em pacientes que não colaboram no consultório odontológico. O objetivo do estudo foi avaliar a resistência ao cisalhamento in vitro de um selante de resina associado a dois tipos de adesivos contaminados com saliva e sangue. Foram utilizados molares humanos saudáveis e os espécimes e as coroas foram seccionados na direção bucal-lingual, obtendo assim dois segmentos de proporções semelhantes (mesial e distal), totalizando 60 superfícies, e as superfícies foram divididas aleatoriamente em 4 grupos (n = 15). O Grupo I (controle) não recebeu nenhum tipo de contaminação e o selante foi aplicado. No grupo II, as superfícies foram contaminadas com 10 μl de saliva / sangue e o selante foi aplicado. No grupo III, as superfícies foram contaminadas com 10 μl de saliva / sangue e o sistema adesivo Single-Bond foi aplicado seguindo a aplicação de selante. No grupo IV, as superfícies foram contaminadas com 10 μl de saliva / sangue e o sistema adesivo de ataque total Prime & Bond NT foi aplicado seguido da aplicação de vedante. As amostras foram testadas na máquina de ensaio universal e a análise da resistência à ligação ao cisalhamento foi realizada. Uma diferença entre o Grupo I (12,61MPa) e os outros grupos foi encontrada; O Grupo II (2,28 MPa) foi diferente dos Grupos III (7,07MPa) e IV (7,79 MPa), mas os Grupos III e IV foram semelhantes. A aplicação de um sistema adesivo quando existe contaminação com saliva / sangue é necessária antes da aplicação de selantes de fissura e fissura.. Palavras-chave: Selantes de Fossas e Fissuras. Contaminação Biológica. Resistência ao Cisalhamento.

Short-term effect of adhesive system on clinical performance of bulk fill composite

Aim: Although bulk fill composites have been widely used as restorative material, there is no consensus regarding the best clinical protocol in terms of composite technique and adhesive system. Therefore, this clinical trial evaluated the clinical performance of bulk fill composites for class I restorations under different protocols. Methods: A randomized clinical trial including 155 class I restorations was conducted using different adhesive systems: conventional technique (phosphoric acid + conventional three-step adhesive system) (Group 1, 2 and 3); or self-etching adhesive system (Groups 4, 5 and 6). Control groups 1 and 4 were restored with conventional composite; groups 2 and 5 with low viscosity bulk fill and conventional composite as occlusal coverage; groups 3 and 6 with high viscosity bulk fill. The FDI criteria was used for clinical evaluation at baseline and after 6 months. Results: All groups showed good clinical performance. At baseline, the adhesive system did not affect postoperative hypersensitivity. After 6 months, group 5 showed a significant reduction in color and translucency; group 6 a reduction in terms of anatomical form and for postoperative sensitivity and an improvement in patient satisfaction (p<0.05). Considering the same restorative technique, the use of the self-etching adhesive system showed a significant decrease in color and translucency (p<0.05). Conclusion: All groups showed favorable clinical performance, and promising results were found for the conventional adhesive system and high viscosity bulk fill protocol.

Response of dental pulp capped with calcium-silicate based material, calcium hydroxide and adhesive resin in rabbit teeth

Direct pulp capping induces a local inflammatory process. Several biomaterials have been used for this procedure. The aim of this study was to compare the dentinal bridge thickness using three different pulp capping biomaterials with the conventional technique (high speed diamond bur) or Er-Yag laser, 1 month after pulp effraction. Materials and Methods: Forty two Class V cavities were prepared on the buccal surface of 4 maxillary incisors and 2 mandibular incisors of New Zealand rabbits. Specimens were divided into 6 treatment groups. Teeth were treated with: In Group 1: Er-Yag laser and Biodentine® (Septodont), in Group 2: Er: Yag laser and calcium hydroxide (Dycal® Dentsply), in Group 3: Er: Yag laser and adhesive system (Prime& Bond® NT Dentsply), in Group 4: high speed diamond bur and Biodentine® (Septodont), in Group 5: high speed diamond bur and calcium hydroxide (Dycal® Dentsply), and in Group 6: high speed diamond bur and adhesive system (Prime& Bond® NT Dentsply). The preparation was done with copious irrigation. The animals were sacrificed at 30 days and the teeth were extracted and prepared for histological analysis. Results: In the group of « laser Er-Yag », iatrogenic pulpal wounds treated with Biodentine® were covered with a thick hard tissue barrier after 1 month. The difference was not significant with the groups of Dycal® used with Er: Yag laser and high speed diamond bur. Prime& Bond® NT Dentsply specimens showed a thin dentinal bridge layer. Conclusion: At 1 month, Er-Yag laser proved to be useful with Biodentine® for direct pulp capping procedures.

Jumping with adhesion: landing surface incline alters impact force and body kinematics in crested geckos

Arboreal habitats are characterized by a complex three-dimensional array of branches that vary in numerous characteristics, including incline, compliance, roughness, and diameter. Gaps must often be crossed, and this is frequently accomplished by leaping. Geckos bearing an adhesive system often jump in arboreal habitats, although few studies have examined their jumping biomechanics. We investigated the biomechanics of landing on smooth surfaces in crested geckos, Correlophus ciliatus, asking whether the incline of the landing platform alters impact forces and mid-air body movements. Using high-speed videography, we examined jumps from a horizontal take-off platform to horizontal, 45° and 90° landing platforms. Take-off velocity was greatest when geckos were jumping to a horizontal platform. Geckos did not modulate their body orientation in the air. Body curvature during landing, and landing duration, were greatest on the vertical platform. Together, these significantly reduced the impact force on the vertical platform. When landing on a smooth vertical surface, the geckos must engage the adhesive system to prevent slipping and falling. In contrast, landing on a horizontal surface requires no adhesion, but incurs high impact forces. Despite a lack of mid-air modulation, geckos appear robust to changing landing conditions.

(Un)expected Similarity of the Temporary Adhesive Systems of Marine, Brackish, and Freshwater Flatworms

Many free-living flatworms have evolved a temporary adhesion system, which allows them to quickly attach to and release from diverse substrates. In the marine Macrostomum lignano, the morphology of the adhesive system and the adhesion-related proteins have been characterised. However, little is known about how temporary adhesion is performed in other aquatic environments. Here, we performed a 3D reconstruction of the M. lignano adhesive organ and compared it to the morphology of five selected Macrostomum, representing two marine, one brackish, and two freshwater species. We compared the protein domains of the two adhesive proteins, as well as an anchor cell-specific intermediate filament. We analysed the gene expression of these proteins by in situ hybridisation and performed functional knockdowns with RNA interference. Remarkably, there are almost no differences in terms of morphology, protein regions, and gene expression based on marine, brackish, and freshwater habitats. This implies that glue components produced by macrostomids are conserved among species, and this set of two-component glue functions from low to high salinity. These findings could contribute to the development of novel reversible biomimetic glues that work in all wet environments and could have applications in drug delivery systems, tissue adhesives, or wound dressings.