Jul 2026· E -journal of dentistry· Vol 175, pp.
106942
· 0 citations· 41 references
Medicine
TL;DR
This in vitro study developed a bioactive orthodontic adhesive for clear-aligner attachments with antibacterial activity, calcium and phosphate ion release, and bonding performance comparable to a commercial adhesive, and findings support further investigation of bioactive adhesives for reducing biofilm-related risks around clear-aligner attachments.
Abstract
Objective
To formulate a novel dual-functional adhesive integrating dimethylaminododecyl methacrylate (DMADDM) for antibacterial activity and nano-amorphous calcium phosphate (NACP) for calcium/phosphate ion release, without compromising enamel bond strength.
Methods
A low-shrinkage-stress resin of urethane dimethacrylate/triethylene glycol divinylbenzyl ether (UDMA/TEGDVBE, denoted UV) was used as the base resin. 10-methacryloyloxydecyl dihydrogen phosphate (MDP) was incorporated at 6% by weight to promote chemical bonding to enamel and stabilize the adhesive interface. DMADDM (0%, 3%, 6% by weight) and NACP (0%, 10%, 20% by weight) were incorporated. A commercial adhesive (Assure Plus) served as a control. Degree of conversion (DC), paste flowability, and enamel shear bond strength (SBS) were measured. Streptococcus mutans biofilms were analyzed for colony-forming units (CFU), lactic-acid production, and metabolic activity (MTT). Calcium and phosphate ion release were measured. Data were analyzed using ANOVA/Tukey (α = 0.05).
Results
Experimental adhesives showed SBS (n = 12) of 15.2 MPa to 18.5 MPa, statistically similar to the control (p > 0.05). DC for the experimental formulations ranged from 48.8% to 65.2% versus 72.5% for the commercial control. Flow (n = 3) decreased with increasing NACP (p < 0.05). Adhesives containing 6% DMADDM reduced S. mutans biofilm CFU by approximately 2-log compared to the control and substantially reduced lactic acid production and metabolic activity of biofilms (p < 0.05). NACP formulations released Ca and PO₄ ions up to (1.55 ± 0.06) mmol/L and (1.0 ± 0.04) mmol/L, respectively, at 35 days and pH 4.
Conclusion
NACP formulations released Ca and PO₄ ions, demonstrating sustained ion release under acidic conditions. These in vitro findings support further investigation of bioactive adhesives for reducing biofilm-related risks around clear-aligner attachments. Direct enamel demineralization and remineralization testing is needed to evaluate their effect on white-spot lesion formation.
CLINICAL
Significance
This in vitro study developed a bioactive orthodontic adhesive for clear-aligner attachments with antibacterial activity, calcium and phosphate ion release, and bonding performance comparable to a commercial adhesive. These findings support further investigation of bioactive adhesives for reducing biofilm-related risks around clear-aligner attachments.
Glass ionomer cements (GICs) are widely used in restorative dentistry because of their chemical adhesion to dental tissues and fluoride release. However, their clinical performance may be limited by insufficient mechanical strength, reduced durability under occlusal loading, and aesthetic concerns. Nanoparticle reinforcement may help address these limitations. This study screened hybrid tri-nanofiller formulations containing nano-hydroxyapatite (nHA), nano-zirconium oxide (nZrO₂), and nano-aluminum oxide (nAl₂O₃) in Fuji IX GIC to identify an optimized formulation using a sequential screening approach. Surface characteristics, structural features, cytocompatibility, and color stability were also evaluated. One unmodified Fuji IX control and sixteen experimental subgroups were prepared in a 4 × 4 comparative screening matrix using four tri-nanofiller formulations and four total nanoparticle loadings: 3, 5, 7, and 9 wt%. In the first stage, all subgroups were screened using compressive strength (CS) and diametral tensile strength (DTS). Mechanical data were analyzed using within-loading one-way ANOVA with Tukey's HSD post hoc test, and two-way ANOVA was additionally performed to assess the effects of formulation, loading concentration, and their interaction. Based on mechanical screening, the G4 formulation was selected for further evaluation using atomic force microscopy (AFM), cell counting kit-8 (CCK-8) cytotoxicity testing on human dental pulp stem cells (hDPSCs), color stability assessment, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). G4 at 5 wt% total nanoparticle loading showed the most favorable mechanical performance, with CS = 160.4 ± 7.64 MPa and DTS = 15.66 ± 0.92 MPa. This subgroup corresponded to 95 wt% Fuji IX, 3.5 wt% nZrO₂, 1.0 wt% nHA, and 0.5 wt% nAl₂O₃. SEM/EDS supported nanoparticle incorporation and homogeneous elemental distribution. AFM analysis showed lower surface roughness at 3% and 5% than at higher loadings. The CCK-8 assay showed no significant cytotoxicity for G4 at 3, 5, 7, or 9 wt% compared with the unmodified control. Color stability remained clinically acceptable at 3 and 5 wt%, whereas 7 and 9 wt% showed greater discoloration. The optimized formulation was G4 at 5 wt% total nanoparticle loading, which improved the mechanical performance of Fuji IX GIC while maintaining acceptable cytocompatibility and color stability.
S. Al-hammadi, Mengdi Li, A. Madfa et al.· Scientific Reports· 0 citations
The aim of this study was to evaluate the shear bond strength (SBS) of aligner attachments bonded to enamel, composite-restored, and lithium disilicate glass-ceramic surfaces using flowable and high-viscosity resin composites. Ninety extracted premolars were divided into three groups (n = 30) according to surface type: enamel (Group 1), composite resin restoration (Group 2), and lithium disilicate glass-ceramic (Group 3). Groups 1 and 2 were etched with 37% phosphoric acid, while Group 3 was etched with 9.6% hydrofluoric acid. A universal adhesive was applied to all specimens. Each group was divided into two subgroups based on composite type (flowable or high-viscosity universal; n = 15). SBS and adhesive remnant index (ARI) were evaluated. One-way ANOVA, Student’s t-test, and Fisher Freeman Halton test were used for statistical analyses (p < 0.05). The highest SBS were obtained in Group 1 bonded with high-viscosity universal composite attachments (mean (± SD), 19.6 (± 6.7 MPa)), and the lowest were obtained in Group 2 bonded with flowable composite attachments (mean (± SD), 7.3 (± 1.8 MPa)). Comparison of three groups within themselves according to the composite resin factor, the mean SBS of Group 2 for high-viscosity universal resin was higher than for flowable resin (p < 0.001). ARI scores did not show a significant correlation with either tooth surface or composite resin type. High-viscosity resin composite provides more reliable bond strength than flowable composite when bonding aligner attachments to composite-restored surfaces. Both composite types demonstrated clinically acceptable bond strength on enamel and lithium disilicate surfaces.
Orthodontic adhesives can accumulate biofilm, which may lead to long-term white-spot lesions; however, incorporating poly (lactic-co-glycolic acid) (PLGA) nanoparticles could improve their anticariogenic properties. Objective: To develop PLGA nanoparticles containing antiseptic agents for orthodontic adhesives, improve antibacterial activity against Streptococcus mutans, and assess cytotoxicity in gingival fibroblasts. Methods: PLGA nanoparticles with chlorhexidine and chitosan were synthesized and characterized using FTIR, SEM, and UV-Vis spectroscopy. Antibacterial activity was evaluated by agar diffusion and microdilution assays, and cytotoxicity and microhardness were also assessed. Results: PLGA-NPs showed moderate antibacterial effects, with inhibition rates from 74.25% to 54.05% in agar diffusion and reduced activity in microdilution (CC50: 3.75 µg/mL in adhesive, 15 µg/mL free). PLGA-NPs-CHx exhibited stronger antibacterial activity, with inhibition ranging from 89.38% to 73.75% and a CC50 of 0.93 µg/mL in both forms. PLGA-NPs-CH also showed significant inhibition (83.11% to 69.39%) and a CC50 of 1.87 µg/mL in adhesive and 7.5 µg/mL free. Vickers microhardness values were similar across groups: 74.67 HV for adhesive only, 74.11 HV for adhesive with PLGA-NPs, 74.22 HV for PLGA-NPs-CH-Adh, and 74 HV for PLGA-NPs-CHx-Adh. Conclusions: Incorporating PLGA nanoparticles functionalized with antiseptic agents into orthodontic adhesives shows promising antibacterial potential and may benefit orthodontic practice.
Alejandra Itzel Lopez-Flores, Ulises Velázquez-Enríquez, R. Scougall-Vilchis et al.· Coatings· 0 citations
Oral diseases, such as periodontitis, remain a major global concern due to their high incidence and significant morbidity. The principal drivers are bacterial overgrowth and associated inflammation. Bioactive glass of the 45S5 Bioglass® composition (BG) is known for its remineralising, osteogenic and antibacterial effects via ion release, but its application has been limited in oral environments. In this study, a photocurable GelMA hydrogel was developed as a carrier matrix for BG (1–15% w/v) to obtain synergy between the adhesive properties of the GelMA and the bioactivity of the glass. Incorporation of 10% w/v BG improved ultimate tensile strength (97 kPa) compared to pure GelMA (58 kPa) and reduced swelling by 18%. The composites showed ~60% higher adhesive strength on collagen sheets than GelMA alone. Tensile bonding strengths reached 54 kPa on collagen sheets and 23 kPa on tooth sections. Lap-shear adhesive strengths were 44 kPa on collagen and 18 kPa on implant metal. In vitro studies confirmed the composite’s biocompatibility with dental pulp stem cells and antibacterial activity against Escherichia coli and methicillin-resistant Staphylococcus aureus. Overall, the GelMA/BG composite presents a multifunctional platform for dental remineralisation with promising mechanical, adhesive and antibacterial performance.
Tian-Yuan Zhao, Andrew M. Edwards, A. Celiz et al.· Journal of Functional Biomat...· 0 citations
Self-adhesive resin composites (SARCs) are gaining popularity due to their simplified clinical steps. The objectives of the study were to evaluate the bonding performance, mass stability and mechanical properties of three SARC materials and to compare them with those of two conventional RC materials using a universal adhesive system (UAS). Materials and Methods: A total of 80 bovine enamel blocks with 5 mm × 5 mm dimensions were prepared and embedded in acrylic molds. The surface of the enamel was polished using 600-grit carbide to create the smear layer. After acid etching, 2 mm × 2 mm cylinder-shaped restorations were made either with one of the three SARCs or with two types of RCs using UASs. Shear bond strength tests were performed after 24 h of water incubation and after 1 year of artificial aging. The mass stability of the hexagonal-shaped SARC and conventional RC was evaluated using water sorption and solubility tests. Then the mechanical properties of the bonded composites were tested, including Vickers hardness, elastic modulus and creep, after 24 h of water incubation and after 1 year of artificial aging. Results: Both the material types and aging showed a significant effect on the bonding performance, mass stability and mechanical properties of SARCs and conventional RCs (p < 0.05). The shear bond strength of SARCs was comparable to that of a conventional RC + UAS. Conventional RCs showed lower water sorption and solubility compared to SARCs. The Vickers hardness, elastic modulus and creep properties of some SARCs were inferior compared to conventional RCs both at 24 h and at 1 year. Conclusions: The bonding performance of SARCs can substitute the conventional RC+ UAS; however, its inferior mass stability and mechanical properties limit its use in routine dental restorative procedures.
Objective To report the in situ synthesis of amorphous fluorinated calcium phosphate (AFCP) nanoparticles within a dual-component hydrogel and evaluate their efficacy for enamel remineralization and dentinal tubules (DTs) occlusion. Materials and Methods The AFCP hydrogel was constructed using hydroxypropyl methylcellulose (HPMC) and carboxymethyl chitosan (CMC) to stabilize calcium, phosphate, and fluoride ions in a metastable amorphous state. Physicochemical characterization was performed by FTIR, XRD, TEM, and SEM-EDX. Biocompatibility was assessed via CCK-8 assays and oral mucosal irritation test. Demineralized enamel and dentin specimens (n=8) were treated with deionized water, fluoride (NaF, 2000 ppm F), 10% CPP-ACP with 900 ppm F (GC Tooth Mousse Plus, Japan), or AFCP hydrogel, and immersed in artificial saliva for 7 days. Remineralization was evaluated by SEM, XRD, and nanoindentation, followed by in vivo validation in a rabbit model. Results The hydrogel generated AFCP nanoparticles (30–80 nm) that remained amorphous in artificial saliva for over 2 hours before crystallizing into hydroxyapatite. The hydrogel exhibited negligible cytotoxicity and no oral mucosal irritation. After 7 days, the AFCP hydrogel induced dense mineral deposition that completely occluded exposed DTs and formed a ~32 µm remineralized layer on acid-etched enamel, substantially outperforming fluoride and CPP-ACP + NaF. XRD confirmed the newly formed mineral as hydroxyapatite-like. Treatment with the AFCP hydrogel restored the mechanical properties of enamel and dentin to near-physiological levels, achieving the greatest recovery among the four groups (P < 0.05). In vivo results further validated its remineralization and tubule-occluding efficacy. Conclusion The AFCP hydrogel functions as an exogenous mineral reservoir, enabling sustained ion release or direct transformation into hydroxyapatite for in situ enamel remineralization and DTs occlusion. This non-invasive strategy offers a promising therapeutic approach for early caries and dentin hypersensitivity.
Zhixin Zhang, Zhe Wang, Jiangling Su et al.· International Journal of Nan...· 0 citations
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