Riboflavin and Its Effect on Dentin Bond Strength: Considerations for Clinical Applicability-An In Vitro Study

Effect of Limonene on the Bond Strength of a Universal Adhesive System to Caries-Affected Dentin

OBJECTIVE

This study aimed to evaluate the effect of limonene (LIM) on the bond strength of a universal adhesive system in self-etch mode to caries-affected dentin (CAD).

MATERIALS AND METHODS

Class I cavities were prepared in eighty sound human molars and divided into four groups (n = 20): Sound dentin (SD), SD + LIM (SD treated with LIM), CAD, and CAD + LIM (CAD treated with LIM). Following pH cycling, two layers of a universal adhesive system (Single Bond Universal, 3MESPE) were applied. After restoration (Filtek Z350, 3MESPE), samples were sectioned into 0.9 mm2 sticks and stored in distilled water at 37°C for 24 h and 6 months. Subsequently, sticks were subjected to microtensile bond strength testing. Data were analyzed using 2-way ANOVA and Bonferroni's test (p < 0.05). Fracture patterns were examined under optical and scanning electron microscopes.

RESULTS

After 24 h, SD + LIM showed lower bond strength than CAD but remained higher than CAD + LIM. CAD + LIM exhibited the lowest bond strength, regardless of aging. In SD + LIM, widened dentinal tubules were observed, accompanied by resin tags. In CAD + LIM, disorganized and unprotected collagen fibrils were identified, with fewer resin tags.

CONCLUSIONS

Limonene decreased the bond strength of the universal adhesive system in self-etch mode to caries-affected dentin.

CLINICAL SIGNIFICANCE

Limonene as a pretreatment in self-etch adhesive protocols shows potential for enhancing the durability of adhesive restorations on sound dentin. However, its use on caries-affected dentin could compromise adhesion, highlighting the need for careful consideration when applying it to compromised substrates.

SWEEPS-Assisted Antibacterial Photodynamic Therapy Against Dual-Species Biofilms in Mandibular Molars: An In Vitro Study

Objectives: The synergistic effect of shock wave-enhanced emission photoacoustic streaming (SWEEPS) and antimicrobial photodynamic therapy (aPDT) in mandibular molar root canal disinfection remains underexplored, particularly against dual-species biofilms that better simulate clinical conditions. This study evaluates their combined antimicrobial efficacy against Enterococcus faecalis and Candida albicans biofilms and assesses potential tooth discoloration caused by riboflavin and nano-curcumin. Materials and Methods: The mesiobuccal canals of 57 extracted mandibular molars were inoculated with E. faecalis and C. albicans biofilms. The antimicrobial effects were assessed using riboflavin or nano-curcumin with a 450 nm diode laser (BDL), SWEEPS, or their combinations, compared to 5.25% NaOCl (positive control) and saline (negative control). Biofilm reduction was quantified by colony-forming units (CFUs/mL), and discoloration was evaluated using the ΔE metric in the CIE L*a*b* color space. Results: Both microorganisms showed a significant decrease in colony numbers in all experimental groups compared to the negative control (p < 0.001), except for E. faecalis, where no significant difference was observed between the riboflavin/nano-curcumin groups and the negative control. Combining riboflavin or nano-curcumin with SWEEPS or BDL significantly enhanced antimicrobial efficacy compared to individual treatments (p < 0.001). The combined photodynamic therapy and SWEEPS groups showed the lowest colony counts. The ΔE values were, on average, 1.81 for riboflavin and 1.09 for nano-curcumin. Conclusions: The combination of SWEEPS and aPDT effectively reduces E. faecalis and C. albicans biofilms in molars, supporting its potential as an adjunct in endodontic disinfection. Minimal discoloration further highlights its clinical applicability.

Use of Photoreactive Riboflavin and Blue Light Irradiation in Improving Dentin Bonding-Multifaceted Evaluation

Recently, photoactivated riboflavin (RF) treatments have been approved to improve resin-dentin bonding by enhancing dentinal collagen crosslinking. This study aimed to evaluate whether RF activated by blue light (BL, 450 nm) strengthens the collagen matrix, increases resistance to enzymatic degradation, and improves adhesion as effectively as ultraviolet A (UVA, 375 nm) activation. Six groups were examined: control (no treatment); RF0.1UV2 (0.1% RF with 2 min of UVA irradiation); RF0.1BL1, RF0.1BL2, RF1BL1, and RF1BL2 (0.1% and 1% RF with 1 or 2 min of BL irradiation). The effects of RF/BL on collagen crosslinking were validated by gel electrophoresis. A nanoindentation test showed that both RF/UVA and RF/BL treatments enhanced the elastic modulus and nanohardness of demineralized dentin. A zymography assay using collagen extracted from demineralized dentin also revealed significant matrix metalloproteinase-2 inhibition across all RF treatments. Microtensile bond strength (µTBS) tests conducted both post-treatment and after 7-day enzymatic degradation showed that three RF0.1 groups (RF0.1UV2, RF0.1BL1, and RF0.1BL2) maintained high µTBS values after degradation, while RF0.1BL1 generated a significantly thicker hybrid layer compared to other groups. These findings suggest that RF/BL is as effective as RF/UVA in crosslinking dentinal collagen and resisting enzymatic degradation, with 0.1% RF proving superior to 1% RF in enhancing dentin bonding.

Pretreatment of enamel with Riboflavin activated photodynamic therapy and Er, Cr: YSGG laser for bonding of orthodontic bracket with adhesive modified with cerium oxide nanoparticles

AIM

To assess the degree of conversion (DC) and shear bond strength (SBS) of experimental adhesive (EA) infused with and without 1 % Cerium oxide (CeO₂)-NPs on metallic bracket bonded to enamel conditioned with three different pretreatment regimes PDT-activated (Riboflavin) RF, ECY (Er, Cr: YSGG), and Phosphoric acid (PA).

MATERIAL AND METHOD

EA and EA modified with 1 % CeO₂-NPs were prepared. Characterization of CeO2NPs was assessed using a scanning electron microscope (SEM). Seventy-two premolars extracted due to periodontal or orthodontic reasons were disinfected. Samples were mounted and allocated into three groups according to enamel surface treatment before bracket bonding. Samples in Group 1 were pretreated with Traditional 37 % PA-gel; Specimens in Group 2 surface treated with RF-activated PDT, and samples in Group 3 were conditioned using ECY. Brackets were placed on conditioned surfaces and samples were aged and underwent SBS testing using UTM. ARI index was used to assess bond failure. DC was evaluated for both adhesives using FTIR. ANOVA and Tukey post hoc test were used to compare the means and standard deviation (SD) of SBS and DC in different experimental groups.

RESULTS

Enamel conditioned with PA and RF activated by PDT demonstrated comparable bond values with 1 % CeO2 infused in EA and EA (p>0.05).ARI analysis shows that enamel conditioned with PA and RF activated by PDT showed the majority of failure types between 1 and 2 irrespective of the type of adhesive. DC value in EA (73.28±8.37) was the highest and comparable to 1 % CeO2 infused in EA (66.48±6.81) CONCLUSION: RF-activated PDT can be used alternatively to 37 % PA for enamel conditioning when bonding metallic brackets. Infiltration of 1 % CeO2 NPs in EA improves SBS irrespective of the type of enamel conditioning. Infusion of 1 % CeO2 NPs in EA demonstrates no significant difference in DC compared to EA.

In Vitro Assessment of SWEEPS and Antimicrobial Photodynamic Therapy Alone or in Combination for Eradicating Enterococcus faecalis Biofilm in Root Canals

OBJECTIVES

This study investigates the efficacy of antimicrobial photodynamic therapy (aPDT) using riboflavin and a blue diode laser (BDL), combined with shock wave-enhanced emission photoacoustic streaming (SWEEPS), against Enterococcus faecalis.

MATERIALS AND METHODS

A total of 48 extracted single-rooted human teeth were used. The root canals were instrumented, sealed at their apices, had the smear layer removed, and then underwent autoclave sterilization. Subsequently, each canal was inoculated with E. faecalis bacterial suspension and allowed to incubate for ten days. After confirming the presence of biofilms through scanning electron microscopy (SEM) in three teeth, the remaining teeth were randomly allocated into nine groups, each containing five teeth: control, 5.25% sodium hypochlorite (NaOCl), BDL, SWEEPS + normal saline, SWEEPS + NaOCl, riboflavin, riboflavin + SWEEPS, riboflavin + BDL, and riboflavin + BDL + SWEEPS. After the treatment, the numbers of colony-forming units (CFUs)/mL were calculated. The data were analysed using one-way ANOVA followed by Tukey's test for comparisons.

RESULTS

All groups, with the exception of the BDL group, exhibited a significant reduction in E. faecalis CFU/mL when compared to the control group (p < 0.001). The difference in CFU/mL value between riboflavin + BDL + SWEEPS and riboflavin + SWEEPS was significant (p = 0.029), whereas there was no significant difference between riboflavin + BDL + SWEEPS and riboflavin + BDL (p = 0.397). Moreover, there was no statistically significant difference between the riboflavin + SWEEPS group and the riboflavin + BDL group (p = 0.893).

CONCLUSIONS

The results demonstrated that combining the SWEEPS technique with riboflavin as a photosensitizer activated by BDL in aPDT effectively reduced the presence of E. faecalis in root canals.

Effect of etchant containing an Urushiol monomer from lacquer sap on dentin biostability and bonding performance

Objectives: This study aimed to evaluate the effectiveness of urushiol as an additive to surface acid etchant on dentin structure, by assessing the biostability of dentin, and determine the bonding strengths of dentin and enamel to the composite in the complicated oral microecology. Methods: Etchants with different concentrations of urushiol (0.5, 1, or 3 wt%) were formulated and tested for their bonding performance. Demineralized dentin beams that were etched with experimental etchants were incubated in simulated body fluid solutions by evaluating the weight decrement after 1 month. The effects of urushiol on dentin and matrix metalloproteinases were confirmed by scanning electron microscopy (SEM). Moreover, the antibiotic actions of urushiol on the common cariogenic bacteria Streptococcus mutans, Streptococcus sanguinis, and Streptococcus gordonii as well as the biofilm were evaluated, and its effect on bacterial morphology was observed by scanning electron microscopy. Finally, enamel and dentin specimens were prepared from human molars to determine the depth of demineralization by the etchants and the relationship with the resin bond strengths to enamel and dentin (μTBS) and the morphology of the bonding interface. Results: Urushiol could interact with dentine and inhibit collagenase activity, resulting in biostable dentine. The application of the etchants containing 0.5, 1, or 3 wt% urushiol significantly improved the durability of the dentin bonding interface with its instinctive antibacterial property (p < 0.05). Conclusion: Urushiol not only improves dentin stability by interacting with collagen and inactivating MMP activity but also plays a role in the antibacterial effects in the complicated oral microecology. The effectiveness of urushiol etchant prolongs the longevity of bonded dental restorations without compromising clinical operation time.

Dental Restorations

Fulfilling a patient's request for a healthy, functional and esthetic smile represents a daily challenge for dental practitioners [...].

Effect of collagen cross-linkers on dentin bond strength: A systematic review and network meta-analysis

Objective: This study aimed to evaluate the role of collagen cross-linkers in the bonding performance of the resin-dentin interface through a systematic review and a network meta-analysis. Sources: The literature search was conducted in several databases like PubMed, EMBASE, Cochrane, Scopus and Web of Science from their inception till 30 April 2022. Study selection: The inclusion criteria consisted of in vitro studies evaluating the micro-tensile and micro-shear bond strengths of different cross-linkers acting on dentin. Bayesian network meta-analysis was conducted using RStudio. Data: Out of the 294 studies evaluated in the full-text analysis, 40 were included in the systematic review and meta-analysis. Most studies have used cross-linkers as primer (65.1%), followed by incorporating them into in adhesives and acid etching agents. The application methods of the adhesive system were classified as "etch-and-rinse (ER) adhesives" (77%) and "self-etching (SE) adhesives". Moreover, there were six types of cross-linkers in this presented review, of which the most numerous were polyphenols. Conclusion: Different application methods of cross-linkers, the long-term results showed that were only effective when used for longer durations, the immediate results were not statistically different. According to immediate and long-term results, etch-and-rinse (ER) adhesives showed a greater bonding performance than the control groups (p ≤ 0.05), whereas self-etching (SE) adhesives showed similar bond strength values (p ≥ 0.05). The result of network meta-analysis (NMA) showed that Dope like compound showed higher long-term bonding performance than other cross-linkers. Clinical significance: Long-term clinical studies may be needed to determine the effect of the cross-linkers on the bonding properties.

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.