Camila Sabatini

Introduction: The ability of rinsing with water following exposure to fermentable carbohydrate (FC) to raise dental biofilm pH has been surprisingly understudied. This scoping review's objective was to assess the evidence for water's effect on neutralization of dental biofilm pH following FC. Methods: The PRISMA‐ScR checklist was followed for reporting this scoping review. Four databases were searched for studies that evaluated pH response of dental biofilms to FC followed by water rinsing. Two reviewers selected papers and extracted data independently. Results: A total of 1296 papers were identified; 14 studies met inclusion criteria and were further evaluated. Ten studies reported volume of water rinses. Of these studies, five used ≥ 20 mL water, and four of these studies found water to raise biofilm pH significantly. The five studies that reported using < 20 mL water did not find water to raise biofilm pH significantly. Conclusion: Based on a small heterogenous set of studies, it may be summarized that rinsing with ≥ 20 mL of water following FC appears to neutralize dental biofilm; its effectiveness should be further investigated as a cost‐effective, accessible, dental‐caries prevention strategy.

Background: Major advances in pulp biology, biomaterials, and tissue engineering have fuelled the development of regenerative strategies aimed at preserving or restoring pulp vitality. Despite this progress, the clinical translation of these discoveries remains limited or absent. Aims: Although there is a global agenda to reduce and replace animal use in medical research, we believe that a critical missing link in the translational pipeline of regenerative endodontics innovations is the lack of rigorously validated, clinically relevant preclinical models to use in advancing promising in vitro findings through regulatory processes to human application. Methods: While novel alternative methodologies (NAMs), including microfluidics, organoids, and organ‐on‐chip systems, offer human‐relevant in vitro models and are rapidly transforming early‐stage screening and mechanistic studies, they are currently insufficient to replicate the complex systemic elements provided by animal models, which are essential for demonstrating in vivo efficacy of regenerative therapies. Regulatory approval of devices, drugs, and biologics continues to require robust preclinical evidence generated in whole‐organism systems, particularly when complex interactions involving immunity, vascularisation, innervation, and aging are central to therapeutic success. Results: In this perspective article, we discuss key scientific, methodological, and logistical considerations for the systematic development and validation of orthotopic animal models in regenerative endodontics research. We place particular emphasis on vital pulp treatment as a biologically and clinically relevant framework for studying pulp repair and in demonstrating the efficacy of novel therapies. We highlight the challenges that have hindered consensus in model selection and standardisation, and emphasise the need for coordinated transdisciplinary efforts to overcome these barriers. Conclusion: We argue that prioritising standardised orthotopic vital pulp treatment models, in combination with evolving NAMs, represents a critical step to bridge the gap between mechanistic discoveries and clinical translation in regenerative endodontics.

Background: Bioengineering of human teeth for replacement is an appealing regenerative approach in the era of gene therapy. Developmentally regulated transcription factors hold promise in the quest because these transcriptional regulators constitute the gene regulatory networks driving cell fate determination. Atonal homolog 1 (Atoh1) is a transcription factor of the basic helix-loop-helix (bHLH) family essential for neurogenesis in the cerebellum, auditory hair cell differentiation, and intestinal stem cell specification. The functional versatility of Atoh1 prompted us to test the possibility that Atoh1 may intersect the dental pulp stem cell (DPSC) gene regulatory network governing odontogenic differentiation. Methods: We isolated DPSCs from human dental pulps and treated the cells with a replication-deficient adenoviral vector to achieve robust ectopic expression of Atoh1, following which the growth and odontogenic differentiation profiles of DPSCs were characterized. Results: DPSCs harboring the Atoh1 expression vector exhibited an approximately 3,000-fold increase in the expression of Atoh1 compared to the negative control, leading to increased DPSC proliferation in the growth medium (P < 0.05). In the odontogenic medium, Atoh1 caused an early induction of BMP2 (P < 0.001) followed by a late induction of BMP7 (P < 0.01) and increased Wnt signaling (P < 0.01). The increased BMP/Wnt signaling led to up to 8-fold increased expression of the master osteogenic transcription factor Osterix (P < 0.005) while exhibiting no significant effect on Runx2 or Dlx5, which are abundantly expressed in DPSCs. Atoh1 stimulated expression of type I collagen (P < 0.005) and small integrin-binding ligand, N-linked glycoproteins (SIBLINGs) such as bone sialoprotein (P < 0.001), dentin matrix protein 1 (P < 0.05), dentin sialophosphoprotein (P < 0.005), and osteopontin (P < 0.001), resulting in increased dentin matrix mineralization (P < 0.05). The odontogenic phenotype is associated with metabolic remodeling marked by enhanced glycolytic flux and attenuated mitochondrial metabolic enzyme activities. Conclusions: Atoh1, despite being a proneural transcription factor in development, possesses a novel odontogenic function upon ectopic expression in DPSCs. This in vitro study demonstrates a novel odontogenic mechanism mediated by ectopic expression of the transcription factor Atoh1 in human DPSCs. The finding may offer an innovative strategy for gene-based regeneration of the pulp-dentin complex.

Halloysite nanotubes (HNTs) are of interest for use in nanocomposites due to their unique cylindrical structure and resulting properties. Various polymer/HNT composites have been studied, but generally these composites have HNTs as a minor component. Here, we report novel polymer/HNT composites with high HNT content facilitated by strong hydrogen-bonding interactions between the polymer and HNTs. These composites with 50–75 wt% HNTs were prepared by in situ polymerization reactions of mixtures comprising HNTs, acrylic acid, triethylene glycol dimethacrylate, potassium persulfate, and water, followed by drying. The chemical structure of composites was verified by Fourier-transform infrared spectroscopy (FTIR). The high dispersity of HNTs in the poly(acrylic acid)-based matrix was demonstrated by scanning electron microscopy (SEM). Studies of mechanical properties illustrated greatly enhanced mechanical strength of the composites relative to the pure polymer matrix, with the highest flexural strength, microhardness, and ultimate tensile strength achieved for the composite with 66.7 wt% HNTs. Thus, the incorporation of high mass fractions of HNTs in a polymer matrix can offer potential benefits for applications requiring superior mechanical properties, in addition to other functions endowed by either HNTs or the polymer matrix. Differential scanning calorimetry (DSC) characterization did not show evidence of a glass transition in the polymer matrices of these composites, and thermogravimetric analysis (TGA) revealed increased thermal stability of the composites relative to the matrices. Swelling tests indicated that the swelling capacity is primarily determined by the amount of polymer present in the composite, and the presence of HNTs may facilitate mass transfer of water within the polymer matrix.

This work reports on polymer–antibiotic conjugates (PACs) as additives to resin-based restorative dental materials as a new strategy to convey sustained antibacterial character to these materials. Such antibacterial performance is expected to improve their longevity in the oral cavity. Using the previously reported ciprofloxacin (Cip)-based PAC as a control, a penicillin V (PV)-based PAC was investigated. The monomer–antibiotic conjugate (MAC) containing a methacrylate monomer group and a PV moiety was prepared via nucleophilic substitution between 2-chloroethyl methacrylate (CEMA) and penicillin V potassium (PVK). The PV-based PAC was synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization of the MAC with hydroxyethyl methacrylate (HEMA), and further characterized by ¹H NMR and gel permeation chromatography (GPC) analysis. Antibiotic resistance was investigated by passaging bacteria in low concentrations of the antibiotic for 19 days, followed by a 48 h challenge at higher concentrations. Our results suggest that the development of antibiotic resistance is unlikely. Zone of inhibition (ZOI) assays revealed no clearing zones around PV-containing resins indicating minimal antibiotic leakage from the material. Similarly, MTT assay demonstrated that the antibiotic-containing specimens did not release cytotoxic byproducts that may inhibit human gingival fibroblast growth. Counting of colony-forming units in an S. mutans biofilm model was used to assess bacterial survival at baseline and after subjecting the antibiotic-containing resin specimens to an enzymatic challenge for 30 days. Significantly reduced bacterial counts were observed as the biofilm aged from 24 to 72 h, and salivary enzymatic exposure did not reduce the antibacterial efficacy of the discs, suggesting that PV-resin will be effective in reducing the re-incidence of dental caries.

Objectives This study investigated the antibacterial, cytotoxicity, and mechanical properties of a dental adhesive modified with quaternary ammonium monomer ((2-acryloyloxyethyl)dimethyldodecylammonium bromide) and cross-linker (bis(2-acryloyloxyethyl)methyldodecylammonium bromide). Materials and methods Monomer (M), cross-linker (C), or a combination of these (M + C) were incorporated into adhesive Adper Single Bond Plus (SB) in 5, 10, or 25% (as wt%). A colony-forming unit and MTT assays were used to evaluate antibacterial properties against Streptococcus mutans and cell viability. Resin-dentin beams (0.9 ± 0.1 mm²) were evaluated for micro-tensile bond strength (μTBS) after 24 h, 6 months, and 3 years. Hourglass specimens were evaluated for ultimate tensile strength (UTS) after 24 h, 1 week, and 6 months. Micro-hardness measurements after softening in ethanol were taken as an indirect assessment of the polymer cross-linking density. Kruskal-Wallis, one-way ANOVA, two-way ANOVA, and Student’s t test were used for analysis of the antibacterial, cytotoxicity, μTBS, UTS, and hardness data, all with a significance level of p < 0.05. Results 10%M and 25%M demonstrated a significant reduction in S. mutans relative to SB (p < 0.001). No differences in cytotoxicity were detected for any of the groups. After 6 months, no changes in μTBS were shown for any of the groups. After 3 years, all groups evidenced a significant decrease in μTBS (p < 0.05) except 5%M, 5%C, and 5%M + 5%C. All groups demonstrated either stable or significantly increased UTS after 6 months. Except for the cross-linker groups, a significant decrease in micro-hardness was shown for all groups after softening in ethanol (p < 0.05). Conclusions A 5–10% of monomer may render the resin antibacterial without a compromise to its mechanical and bonding properties. Clinical relevance Biomodification of a resin adhesive with an antibacterial monomer and cross-linker may help improve the life span of adhesive restorations.

Purpose: To investigate whether dental adhesives modified with polyacrylic acid copper iodide particles could inhibit esterase activity in vitro and the copper release rate from resin matrices, as well as the correlation between the two variables. Materials and Methods: Different concentrations of copper iodide (0.1, 0.5 and 1.0 mg/ml) were incorporated into three commercially available adhesives representative of each type. Disk specimens (n = 3) were fabricated and incubated in cholesterol esterase and pseudo-cholinesterase solutions for 16 days (37 degrees C, pH 7.0). The enzymatic activity and rate of copper release from resin matrices were evaluated at different 4, 8, 12, and 16 days with a UV/visible-light spectrophotometer. Results: Increased copper release and reduced enzymatic activity were observed with higher concentrations of copper iodide (p < 0.001). Greater copper release with reduced enzymatic activity was also demonstrated at the earlier time periods with this relationship reversing over time (p < 0.001). A moderate negative correlation between the variables was evident (-0.441; p = 0.01). Conclusions: Adhesives containing copper iodide can inhibit esterase activity in a dose- and time-dependent manner. The correlation between the variables suggests that enzymatic activity may depend on the availability of copper.