Chitosan-induced biomodification on demineralized dentin to improve the adhesive interface

Comparative Evaluation of Apical Leakage in Root Canal Obturation Using AH Plus Sealer, Bioceramic Sealer, and Bioceramic Sealer Incorporated With Chitosan Nanoparticles: An In Vitro Study

Introduction Endodontic re-infections primarily occur due to the ingress of bacteria and their toxins through an incomplete seal following obturation. A variety of sealers have been developed to achieve effective integration with the different obturation materials and dentinal tubules. To choose the right endodontic sealer and application for each clinical instance, one must be aware of the attributes of the various sealers commonly used in clinical practice. The utility of chitosan nanoparticles in endodontics requires exploration to understand the faring of this material in comparison to the existing gold standards. This study aims to compare the apical leakage after obturation using AH Plus sealer and bioceramic sealer with and without chitosan nanoparticles. Materials and methods Forty single-rooted, single-canal extracted teeth were selected and decoronated to standardize the root length to 14 mm. Root canals were prepared using Protaper rotary files and irrigated with sodium hypochlorite, EDTA (ethylenediaminetetraacetic acid), and saline. The samples were randomly divided into four groups (n=10): group I (gutta percha), group II (gutta percha + AH Plus sealer), group III (gutta percha + bioceramic sealer), and group IV (gutta percha + chitosan nanoparticles in bioceramic sealer). The sealers were applied, and obturation was performed using the cold lateral condensation technique. Post-obturation, the samples were sealed with Cavit-G, coated with nail varnish, and immersed in 2% methylene blue dye for 72 hours. The teeth were then sectioned longitudinally and inspected for dye penetration using a stereomicroscope. Results The mean dye penetration values were as follows: 4.77 ± 2.08 mm in group I, 2.93 ± 0.40 mm in group II, 2.34 ± 1.46 mm in group III, and 1.93 ± 1.68 mm in group IV. Statistical analysis using one-way ANOVA showed significant differences (p < 0.05) between the groups. Tukey's post hoc test revealed the least microleakage in group IV, indicating superior sealing ability of bioceramic sealer with chitosan nanoparticles. Conclusion Incorporation of chitosan nanoparticles in bioceramic sealer significantly enhances its sealing ability, reducing apical microleakage more effectively than gutta percha (2.5 times), AH Plus sealer (1.5 times), and bioceramic sealer alone (1.2 times). This suggests that chitosan nanoparticles could be a promising addition to endodontic sealers to improve treatment outcomes.

Effect of Incorporating Chitosan to Resin Modified Glass Ionomer Cement on Shear Bond Strength to Dentin (An In vitro Comparative Study)

Aim

Resin-modified glass ionomer cement tends to shrink due to polymerization of the resin component. Additionally, they are more prone to syneresis and imbibition during the setting process. This in vitro study evaluates the impact of chitosan, a biopolymer that is, both biomaterial and biocompatible, on the strength of dentin bonding and compares it with ACTIVA Bio-ACTIVE Restorative. The present study was aimed to assess the impact of including chitosan into Fuji II on the shear bond strength between. the restoration material and tooth dentin, in contrast to Bioactiva in permanent teeth.

Materials and Methods

A total of 30 premolar teeth were recently extracted. The study involved three distinct sample groups. Group 1 (10 teeth) is the negative control (Fuji II), Group 2 (10 teeth) is the positive control (ACTIVA Bio-ACTIVE Restorative), and Group 3 (10 teeth) is treated with a mixture of Chitosan and Fuji II (CH-Fuji II). Each tooth's buccal and palatal cusps were eliminated to achieve a horizontal surface. Using a periodontal probe, 1.5 mm from the mesial pit to the mesial marginal ridge were removed. Restoration was implemented in all groups following manufacturer directions. Thermocycling the teeth by immersing them in a water bath with temperatures ranging from 5°C to 55°C (± 1-2°C) for 30 s (500 cycles). Each sample was attached to the universal testing machine's jig at a cross-head speed of 1 mm/min. Shear force was used until breakage, and the bond's adhesive strength was then calculated. Statistical analysis using ANOVA with Dunnett's T3 post hoc test. Results were significant at P < 0.05.

Results

Statistically significant difference was present between Chitosan and Fuji II and between Chitosan and Activa by reducing the shear bond strength.

Conclusions

Addition of chitosan to Fuji II had a negative effect on the shear bond with a significant difference while Activa and Fuji II exhibited favorable shear bond strength.

Aesthetic impact of resin infiltration and its mechanical effect on ceramic bonding for white spot lesions

BACKGROUND

Treating white spot lesions (WSLs) with resin infiltration alone may not be sufficient, raising questions about its compatibility with other treatments amid controversial or incomplete data. Therefore, this study aimed to assess the aesthetic feasibility of resin infiltration combined with bleaching, as well as its potential mechanical effect on ceramic bonding to WSLs.

METHODS

One hundred and fifty flat enamel surfaces of bovine incisors were prepared. Ninety specimens were deminerailized and randomly assigned to three groups(n = 30): post-bleaching resin infiltration (Bl-R), pre-bleaching resin infiltration (R-Bl), and only resin infiltration (R). Color, surface roughness and microhardness were assessed in immediate, thermocycling and pigmentation tests. The remaining sixty samples were randomly assigned to three groups (n = 20): control (Ctrl), bonding (Bo), pre-bonding resin infiltration (R-Bo). Shear bonding strength, failure mode, micro-leakage depth and interface morphology were evaluated after ceramic bonding. The Tukey test and analysis of variance (ANOVA) were used for statistical analysis.

RESULTS

For the effect of resin infiltration and bleaching on WSLs, the R-Bl group showed the worst chromic masking ability, with the highest |ΔL|, |Δa|, |Δb|, and ΔE values after treatment. Compared with those in the Bl-R group, the R-Bl and R groups showed significant time-dependent staining, which is possibly attributed to their surface roughness. For the effect of resin infiltration on the adhesive properties of WSLs, resin infiltration reduced the staining penetration depth of WSLs from 2393.54 ± 1118.86 μm to 188.46 ± 89.96 μm (P < 0.05) while reducing WSLs porosity in SEM observation.

CONCLUSIONS

Post-bleaching resin infiltration proved to be advantageous in the aesthetic treatment of WSLs. Resin infiltration did not compromise bonding strength but it did reduce microleakage and enhance marginal sealing. Overall, resin infiltration can effectively enhance the chromatic results of treated WSLs and prevent long-term bonding failure between ceramics and enamel. Based on these findings, the use of post-bleaching resin infiltration is recommended, and resin infiltration before ceramic bonding is deemed viable in clinical practice.

Biomodification of eroded and abraded dentin with epigallocatechin-3-gallate (EGCG)

This study aimed to evaluate in vitro the effects of epigallocatechin-3-gallate (EGCG) as a biomodifier of eroded and abraded dentin. Forty dentin specimens were obtained from the buccal surface of bovine teeth. The specimens were randomly distributed in 4 groups according to dentin substrate: sound or eroded/abraded and dentin biomodification: with 0.5% EGCG and no biomodification (control group). Specimens were subdivided according to aging time: 24 h and 3 months for the analysis of microtensile bond strength (n = 10), morphology of the adhesive interface by SEM (n = 3) and dentin micropermeability by fluorescence microscope (n = 8). Statistical analysis was performed using SPSS system version 20.0 with a significance level of 5%. The results revealed that the control group with eroded-abraded dentin exhibited the lowest bond strength values at 24 h and 3 months. However, the application of 0.5% EGCG as a biomodifier significantly increased bond strength on both sound and eroded-abraded substrates. After 3 months, all groups exhibited an adhesive interface with a more intense fluorescence in the adhesive layer, indicating an increase in porosity at the interface. In conclusion, the EGCG application as a biomodifier enhanced bond strength on both sound and eroded-abraded dentin substrates, however, adhesive interfaces are more regular when restorations are performed on sound dentin, regardless of the biomodification with EGCG.

Er:YAG laser in selective caries removal and dentin treatment with chitosan: a randomized clinical trial in primary molars

This study evaluated the effect of chitosan on dentin treatment after selective removal of caries lesions with Er:YAG laser in reducing Streptococcus mutans, as well as its effect on the performed restorations. The sample consisted of children (aged 7 to 9 years) with active carious lesions and dentin cavitation located on the occlusal surface of deciduous molars. Eighty teeth were randomly distributed into 4 groups according to the caries removal method: Er:YAG laser (250 mJ/4 Hz) or bur and dentin surface treatment: 2.5% chitosan solution or distilled water. The bacterial load of caries-affected dentin was quantified by counting CFU/mg (n = 10). The teeth were restored and evaluated at 7 days, 6 months, and 12 months using modified USPHS criteria (n = 20). Microbiological data was analyzed by Mann-Whitney and clinical analyses were done using Kruskal-Wallis and Dunn test (α = 0.05). The results showed that the Er:YAG laser significantly reduced the amount of Streptococcus mutans (p = 0.0068). After dentin treatment with chitosan, there was a significant reduction in the amount of Streptococcus mutans for both removal methods (p = 0.0424). For the retention and secondary caries criteria, no significant differences were observed along the evaluated time (p > 0.05). The laser-treated group was rated "bravo" for discoloration (p = 0.0089) and marginal adaptation (p = 0.0003) after 6 and 12 months compared to baseline. The Er:YAG laser reduced the amount of Streptococcus mutans and the chitosan showed an additional antibacterial effect. After 1 year, the Er:YAG laser-prepared teeth, regardless of the dentin treatment, showed greater discoloration and marginal adaptation of the restorations.

Chitosan-Based Biomaterials for Tissue Regeneration

Chitosan is a chitin-derived biopolymer that has shown great potential for tissue regeneration and controlled drug delivery. It has numerous qualities that make it attractive for biomedical applications such as biocompatibility, low toxicity, broad-spectrum antimicrobial activity, and many others. Importantly, chitosan can be fabricated into a variety of structures including nanoparticles, scaffolds, hydrogels, and membranes, which can be tailored to deliver a desirable outcome. Composite chitosan-based biomaterials have been demonstrated to stimulate in vivo regeneration and the repair of various tissues and organs, including but not limited to, bone, cartilage, dental, skin, nerve, cardiac, and other tissues. Specifically, de novo tissue formation, resident stem cell differentiation, and extracellular matrix reconstruction were observed in multiple preclinical models of different tissue injuries upon treatment with chitosan-based formulations. Moreover, chitosan structures have been proven to be efficient carriers for medications, genes, and bioactive compounds since they can maintain the sustained release of these therapeutics. In this review, we discuss the most recently published applications of chitosan-based biomaterials for different tissue and organ regeneration as well as the delivery of various therapeutics.

MODERN TRENDS AND PERSPECTIVES OF THE DEVELOPMENT OF ADHESIVE DENTISTRY. INNOVATIVE TECHNIQUES FOR THE APPLICATION OF ADHESIVE SYSTEMS

OBJECTIVE

The aim: To study the latest approaches to optimizing the composition and application protocols of modern adhesive systems, which are used during the restoration of defects in hard dental tissues with restorative materials.

PATIENTS AND METHODS

Materials and methods: Thirty articles published between January 1, 2020 and February 1, 2023 in the scientific databases PubMed, Scopus, and Google Scholar were selected. The selected scientific works contained the results of laboratory studies, systematic reviews, meta-analyses of the physical and mechanical characteristics of adhesive systems with a modified composition or application protocols different from the instructions of the manufacturing companies.

CONCLUSION

Conclusions: The most promising directions for improving adhesive systems are modifications of the composition and protocols of their use with the aim of deactivating matrix metalloproteinases, improving the structure of the hybrid layer due to the creation of a three-dimensional mesh of collagen fibres with optimal properties, the introduction of antimicrobial agents to slow down the growth of bacterial colonies along the line of the adhesive joint. The available research results of modified adhesive systems are often contradictory, which determines the need to develop standardized test methods to obtain more reliable indicators of their physical, mechanical and biological properties. In some cases, the consequences of non-compliance with the recommendations of the manufacturing companies are a significant deterioration of the characteristics of the hybrid layer, adhesive strength, marginal fit, which, in turn, explains the need for further search for an optimized composition and techniques for applying bonding agents to improve the prognosis of restorative treatment.