Cellulose Nanocrystals Show Anti-Adherent and Anti-Biofilm Properties against Oral Microorganisms.

Cellulose nanocrystals (CNCs) are cellulose-derived nanomaterials that can be easily obtained, e.g., from vegetable waste produced by circular economies. They show promising antimicrobial activity and an absence of side effects and toxicity. This study investigated the ability of CNCs to reduce microbial adherence and biofilm formation using in vitro microbiological models reproducing the oral environment. Microbial adherence by microbial strains of oral interest, Streptococcus mutans and Candida albicans, was evaluated on the surfaces of salivary pellicle-coated enamel disks in the presence of different aqueous solutions of CNCs. The anti-biofilm activity of the same CNC solutions was tested against S. mutans and an oral microcosm model based on mixed plaque inoculum using a continuous-flow bioreactor. Results showed the excellent anti-adherent activity of the CNCs against the tested strains from the lowest concentration tested (0.032 wt. %, p < 0.001). Such activity was significantly higher against S. mutans than against C. albicans (p < 0.01), suggesting a selective anti-adherent activity against pathogenic strains. At the same time, there was a minimal, albeit significant, anti-biofilm activity (0.5 and 4 wt. % CNC solution for S. mutans and oral microcosm, respectively, p = 0.01). This makes CNCs particularly interesting as anticaries agents, encouraging their use in the oral field.

Natural, biphasic calcium phosphate from fish bones for enamel remineralization and dentin tubules occlusion.

OBJECTIVES: A calcium phosphate extracted from fish bones (CaP-N) was evaluated for enamel remineralization and dentinal tubules occlusion. METHODS: CaP-N was characterized by assessing morphology by SEM, crystallinity by PXRD, and composition by ICP-OES. CaP-N morphology, crystallinity, ion release, and pH changes over time in neutral and acidic solutions were studied. CaP-N was then tested to assess remineralization and dentinal tubules occlusion on demineralized human enamel and dentin specimens (n = 6). Synthetic calcium phosphate in form of stoichiometric hydroxyapatite nanoparticles (CaP-S) and tap water were positive and negative controls, respectively. After treatment (brush every 12 h for 5d and storage in Dulbecco's modified PBS), specimens' morphology and surface composition were assessed (by SEM-EDS), while the viscoelastic behavior was evaluated with microindentation and DMA. RESULTS: CaP-N consisted of rounded microparticles (200 nm - 1 µm) composed of 33 wt% hydroxyapatite and 67 wt% ß-tricalcium phosphate. In acidic solution, CaP-N released calcium and phosphate ions thanks to the preferential ß-tricalcium phosphate phase dissolution. Enamel remineralization was induced by CaP-N comparably to CaP-S, while CaP-N exhibited a superior dentinal tubule occlusion than CaP-S, forming mineral plugs and depositing new nanoparticles onto demineralized collagen. This behavior was attributed to its bigger particle size and increased solubility. DMA depth profiling and SEM showed an excellent interaction between the newly formed mineralized structures and the pristine tissue, particularly at the exposed collagen fibrils. SIGNIFICANCE: CaP-N demonstrated very good remineralizing and occlusive activity in vitro, comparable to CaP-S, thus could be a promising circular economy alternative therapeutic agent for dentistry.

Effect of open windows on airborne contamination and its topographical distribution in the dental operatory.

Aerosols produced by dental handpieces represent a permanent risk of disease transmission in the dental environment. The current study evaluated the effects of natural ventilation (open windows) on Streptococcus mutans airborne contamination by dental handpieces in simulated clinical conditions. A dental phantom was placed on a dental chair at a standard university dental clinic operatory. An S. mutans suspension was infused into the phantom's mouth while an operator performed standardized dental procedures using low (contra-angle) and high speed (turbine) dental handpieces or an ultrasonic scaler, with windows open or closed. Selective medium Petri dishes were placed in 18 sites of the operatory environment to evaluate contamination topographically. Sites were clustered as: wall, floor, ceiling, dental chair, and cabinet. Contamination was expressed as log10 CFU/cm2 . A linear mixed model analysis was used, nesting the sites within each ventilation and handpiece combination. Open windows significantly reduced contamination. The high-speed handpiece provided the highest contamination, followed by the ultrasonic scaler and the low-speed handpiece. Contamination values were much smaller at the ceiling, and much larger at the chair. Opening windows produced more homogeneous contamination of the operatory compared to closed windows. Natural ventilation during dental procedures decreases contamination and affects its topographical distribution.

TEGDMA-Functionalized Dicalcium Phosphate Dihydrate Resin-Based Composites Prevent Secondary Caries in an In Vitro Biofilm Model.

This study evaluated the efficacy of experimental TEGDMA-functionalized dicalcium phosphate dihydrate (T-DCPD) filler-based resin-based composites (RBC) in preventing caries lesions around the restoration margins (secondary caries, SC). Standardized Class-II cavities were made in sound molars with the cervical margin in dentin. Cavities were filled with a commercial resin-modified glass-ionomer cement (RMGIC) or experimental RBCs containing a bisGMA-TEGDMA resin blend and one of the following inorganic fractions: 60 wt.% Ba glass (RBC-0); 40 wt.% Ba glass and 20 wt.% T-DCPD (RBC-20); or 20 wt.% Ba glass and 40 wt.% T-DCPD (RBC-40). An open-system bioreactor produced Streptococcus mutans biofilm-driven SC. Specimens were scanned using micro-CT to evaluate demineralization depths. Scanning electron microscopy and energy-dispersive X-ray spectroscopy characterized the specimen surfaces, and antimicrobial activity, buffering effect, and ion uptake by the biofilms were also evaluated. ANOVA and Tukey's tests were applied at p < 0.05. RBC-0 and RBC-20 showed SC development in dentin, while RBC-40 and RMGIC significantly reduced the lesion depth at the restoration margin (p < 0.0001). Initial enamel demineralization could be observed only around the RBC-0 and RBC-20 restorations. Direct antibiofilm activity can explain SC reduction by RMGIC, whereas a buffering effect on the acidogenicity of biofilm can explain the behavior of RBC-40. Experimental RBC with CaP-releasing functionalized T-DCPD filler could prevent SC with the same efficacy as F-releasing materials.

Microbiological models for accelerated development of secondary caries in vitro.

OBJECTIVES: The current study aimed to compare the efficacy of two in vitro microbiological models based on open and closed systems designed to obtain secondary caries in an accelerated and reproducible way. METHODS: A conventional resin-based composite (RBC - Majesty ES-2; Kuraray, Japan) and a resin-modified glass-ionomer cement (RMGIC - Ionolux; VOCO, Germany) were used to restore standardized class II cavities (n = 4/tooth, cervical margin in dentin) in 16 human molars. The ability to produce secondary caries with Streptococcus mutans biofilms was tested using either an open-cycle or closed-cycle bioreactor (n = 8 specimens/model). Specimens were scanned before and after the biofilm exposure using micro-CT (Skyscan 1176, 9 µm resolution, 80 kV, 300 mA). Image reconstruction was performed, and demineralization depths (µm) were evaluated at the restoration margins and a distance of 1.0 mm. RESULTS: Dentin demineralization could be observed in all specimens, and enamel demineralization in 50% of the specimens. The open system bioreactor produced lesions with significantly higher overall demineralization depths (p < .001). However, demineralization depths at a 1.0 mm distance from the restoration margins showed no difference between open and closed systems or materials. In the open system, significantly lower demineralization depths were observed in proximity to RMGIC than RBC (p < .001), which was not significantly different in the closed system (p = .382). CONCLUSIONS: Both systems produced in vitro secondary caries in an accelerated way. However, the open-cycle bioreactor system confirmed the caries-protective activity exerted by the RMGIC material in contrast to the RBC, better simulating materials' clinical behavior. CLINICAL SIGNIFICANCE: The possibility of obtaining accelerated and reproducible secondary caries development in vitro is fundamental in testing the behavior of conventional and yet-to-come restorative dental materials. Such systems can provide faster outcomes regarding the performance of dental restorative materials compared to clinical studies, notwithstanding the importance of the latter.

Physical-chemical and microbiological performances of graphene-doped PMMA for CAD/CAM applications before and after accelerated aging protocols.

OBJECTIVES: Innovative, nanotechnologies-featuring dental materials for CAD/CAM applications are becoming available. However, the interaction with the oral environment poses critical challenges to their longevity. The present study evaluated specific physical-chemical properties and antimicrobial potential of a CAD/CAM graphene-doped resin before and after accelerated aging protocols. METHODS: Graphene nanofibers (GNF)-doped (<50 ppm) PMMA (GPMMA) and control PMMA CAD/CAM discs were used. Specimens underwent aging procedures of their bulk (thermo- and load-cycling) and surface (24 h-immersion in absolute ethanol), then they were tested for flexural strength, ultimate tensile strength, sorption/solubility, and methyl-methacrylate elution. Surface characterization included x-ray diffraction, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, surface roughness, microhardness, and scanning electron microscopy (SEM). Adherence of Streptococcus mutans and Candida albicans, and biofilm formation (continuous-flow bioreactor) by the same strains and an artificial oral microcosm were investigated. RESULTS: GNF-doping improved the physical-chemical bulk properties of the PMMA resin. Surface aging reduced microhardness and increased the roughness of both test and control materials. Surfaces displayed signs of swelling and degradation at SEM. Microbiological data of non-aged surfaces showed that GNF-doping significantly reduced biofilm formation by all tested strains despite having no impact on microbial adherence. After aging, microbial adherence was higher on GPMMA surfaces, while biofilm formation was not promoted. SIGNIFICANCE: GNF-doping improved the material's performance and influenced its antimicrobial potential. This strategy seems a valuable option to overcome the effects of surface degradation induced by aging on the antimicrobial potential of PMMA resin.

Assessment of the remineralisation induced by contemporary ion-releasing materials in mineral-depleted dentine.

OBJECTIVES: Evaluate the ability of current ion-releasing materials to remineralise bacteria-driven artificial caries lesions. MATERIALS AND METHODS: Standardised class I cavities were obtained in 60 extracted human molars. Specimens underwent a microbiological cariogenic protocol (28 days) to generate artificial caries lesions and then were randomly divided into four restorative groups: adhesive + composite (negative control); glass ionomer cement (GIC); calcium silicate cement (MTA); and resin-modified calcium silicate cement (RMTA). Microhardness analysis (ΔKHN) was performed on 40 specimens (10/group, t = 30 days, 45 days, 60 days in artificial saliva, AS). Micro-CT scans were acquired (3/group, t = 0 days, 30 days, and 90 days in AS). Confocal microscopy was employed for interfacial ultra-morphology analysis (2/group, t = 0 days and 60 days in AS). Additional specimens were prepared and processed for scanning electron microscopy (SEM) and FTIR (n = 3/group + control) to analyse the ability of the tested materials to induce apatite formation on totally demineralised dentine discs (60 days in AS). Statistical analyses were performed with a significance level of 5%. RESULTS: Adhesive + composite specimens showed the lowest ΔKHN values and the presence of gaps at the interface when assessed through micro-CT even after storage in AS. Conversely, all the tested ion-releasing materials presented an increase in ΔKHN after storage (p < 0.05), while MTA best reduced the demineralised artificial carious lesions gap at the interface. MTA and RMTA also showed apatite deposition on totally demineralised dentine surfaces (SEM and FTIR). CONCLUSIONS: All tested ion-releasing materials expressed mineral precipitation in demineralised dentine. Additionally, calcium silicate-based materials induced apatite precipitation and hardness recovery of artificial carious dentine lesions over time. CLINICAL RELEVANCE: Current ion-releasing materials can induce remineralisation of carious dentine. MTA shows enhanced ability of nucleation/precipitation of hydroxyapatite compared to RMTA and GIC, which may be more appropriate to recover severe mineral-depleted dentine.

Prognostic Factors and Primary Healing on Root Perforation Repaired with MTA: A 14-year Longitudinal Study.

INTRODUCTION: Few data are available on the long-term efficacy of mineral trioxide aggregate (MTA) in treating root canal perforations. This prospective cohort study builds on a previously reported trial to determine the outcome for teeth with root perforations treated with orthograde MTA after longer follow-up and identify potential prognostic factors. METHODS: A prospective cohort study was performed, enrolling (1999-2009) patients with a single dental perforation treated with MTA. Preoperative, intraoperative, and postoperative information was evaluated, and the outcomes were dichotomized as healed or nonhealing. Patients were followed up yearly until 2018 for a maximum of 17 years after treatment, with controls carried out until 14 years. Clinical and radiographic outcomes were evaluated using standardized follow-up protocols. RESULTS: Of the 124 entrolled patients (median age = 36.5 years, 53.2% male), 115 were healed at the first (n = 110, 89%) or second (n = 5, 4%) annual posttreatment checkup, while 9 subjects (7%, 4 females, 18-65 years old) did not heal. Characteristics significantly associated with nonhealing were gender, positive probing, size, and perforation site. Perforations recurred in 48 teeth during the follow-up with the estimated probability of reversal at 5, 10, and 14 years of 6% (95% confidence interval [CI], 2%-10%), 30% (95% CI, 20%-38%), and 62% (95% CI, 46%-73%), respectively. Positive probing had a higher reversal risk (hazard ratio = 3.3, P ≤ .001), and perforations >3 mm were more likely to have a reversal (hazard ratio = 4.1, P < .001). CONCLUSIONS: The risk of reversal for healed MTA-treated root canal perforations, initially relatively low, vastly increases over time.

Airborne contamination of the dental operatory during activities performed with open or closed windows.

PURPOSE: To quantify the biological contamination of a dental operatory environment using a biological tracer. METHODS: A Streptococcus mutans suspension was infused into the mouth of a phantom, and an operator performed standardized dental procedures using an air turbine, a contra-angle handpiece, or an ultrasonic scaler either with windows open or closed. The presence of the tracer was measured by placing Petri dishes with a selective medium at 18 sites on the dental unit and 38 sites in the surrounding operatory environment. RESULTS: The contamination was drastically reduced when windows were opened, no matter which handpiece was used. Air turbine spread significantly higher contamination compared to contra-angle and scaler. All tested instruments spread the tracer over the entire dental unit and the surrounding environment, including the walls and ceiling; however, higher contamination levels were detected on the dental unit compared to the operatory surfaces. Opening windows during dental operative procedures greatly reduced contamination levels for all handpieces and can be recommended for reducing airborne contamination levels. CLINICAL SIGNIFICANCE: The significant levels of airborne contamination produced when operating dental handpieces can be significantly reduced by natural ventilation, i.e., simply opening the windows.

Dental tissue remineralization by bioactive calcium phosphate nanoparticles formulations.

Recent health care products are based on formulations claimed to provide enamel remineralization and dentinal tubules occlusion through calcium-phosphate bioactive nanocompounds (ion-doped hydroxyapatite and precursor, amorphous calcium phosphate nanoparticles). This study aimed to characterize, test, and compare for the first time the structure and performance of a representative, market-available sample of remineralizing toothpastes and topical mousses. Formulations were characterized to determine their composition and investigate the presence of bioactive compounds and doping elements. A conventional fluoride-containing toothpaste was used as reference. The enamel remineralization and efficacy of dentinal tubules occlusion by tested formulations were investigated ex vivo on human hard tissues. All formulations containing Ca-P bioactive nanocompounds showed remineralizing ability by epitaxial growth of a layer showing the morphology and composition of human hydroxyapatite. Such layers also embedded nanosilica clusters. The presence of doping elements or casein phosphopeptide seemed essential to allow such performances, especially when hydroxyapatite and amorphous calcium phosphate compounds were doped with small amounts of CO32-, F-, Mg2+, and Sr2+. Topical mousse formulations showed a higher tubules occlusion capability than toothpastes, independently from their composition. Therefore, all tested formulations could be useful in restoring tooth structures in a biomimetic way, contrasting dental demineralization processes leading to caries.

Aerosol transmission for SARS-CoV-2 in the dental practice. A review by SIdP Covid-19 task-force.

Current evidence suggests that SARS-CoV-2, the virus that causes COVID-19, is predominantly spread from person to person. Aim of this narrative review is to explore transmission modality of SARS-CoV-2 to provide appropriate advice to stakeholders, in order to support the implementation of effective public health measures and protect healthcare workers that primary face the disease. "In vivo" and "in vitro" studies from laboratories and hospitals confirmed the presence of surface contamination and provided insight of SARS-CoV-2 detection in the air, particularly in indoor settings with poor ventilation where aerosol-generating procedures were performed. Measures for aerosol reduction, in conjunction with other effective infection control strategies, are needed to prevent the spread of SARS-CoV-2 in dental setting.

Surface disinfection and protective masks for SARS-CoV-2 and other respiratory viruses: A review by SIdP COVID-19 task force.

OBJECTIVES: Primary focused question for this systematic review (SR) was "Which is the evidence about surfaces decontamination and protection masks for SARS-Cov-2 in dental practice?" Secondary question was "Which is the evidence about surfaces decontamination and protection masks against airborne pathogens and directly transmitted viral pathogens causing respiratory infections?" MATERIALS AND METHODS: PRISMA guidelines were used. Studies on surface decontamination and protective masks for SARS-CoV-2 in dental practice were considered. Studies on other respiratory viruses were considered for the secondary question. RESULTS: No studies are available for SARS-CoV-2. Four studies on surface disinfection against respiratory viruses were included. Ethanol 70% and sodium hypochlorite 0,5% seem to be effective in reducing infectivity by > 3log TCID. Four RCTs compared different types of masks on HCW. The single studies reported no difference for laboratory-diagnosed influenza, laboratory-diagnosed respiratory infection, and influenza-like illness. A meta-analysis was not considered appropriate. CONCLUSIONS: There is lack of evidence on the efficacy of surface disinfection and protective masks to reduce the spread of SARS-CoV-2 or other respiratory viruses in dentistry. However, the consistent use of respirator and routine surface disinfection is strongly suggested. There is urgent need of data on the efficacy of specific protection protocols for dental HCW against viral infections.

Influence of Low-pH Beverages on the Two-Body Wear of CAD/CAM Monolithic Materials.

The aim of this in vitro study is to evaluate the effect of different acidic media on volumetric wear and surface roughness of CAD/CAM monolithic materials. Forty-eight rectangular specimens were prepared using different CAD/CAM monolithic materials: nanohybrid composite (Grandio Blocks, Voco), resin-based composite (Cerasmart, GC), lithium disilicate (E-Max, Ivoclar), and high-translucency zirconia (Katana STML, Kuraray Noritake). After storage in distilled water at 37 °C for two days, the specimens were tested using a chewing machine with a stainless-steel ball as an antagonist (49N loads, 250,000 cycles). Testing was performed using distilled water, Coca-Cola, and Red Bull as abrasive media. Wear and surface roughness analyses of the CAD/CAM materials were performed using a 3D profilometer and analyzed with two-way analysis of variance and post hoc pairwise comparison procedures. Worn surfaces were examined using scanning electron microscopy. Resin-based materials suffered higher volumetric wear than ceramics (p = 0.00001). Water induced significantly less volumetric wear than the other tested solutions (p = 0.0014), independent of the material tested. High-translucency zirconia showed less surface roughness than all the other materials tested. The selection of monolithic CAD/CAM materials to restore worn dentition due to erosive processes could impact restorative therapy stability over time. Resin-based materials seem to be more influenced by the acidic environment when subjected to a two-body wear test.

Influence of Curing Time on the Microbiological Behavior of Bulk-Fill Nanohybrid Resin Composites.

This in vitro study aimed to evaluate the influence of curing time on surface characteristics and microbiological behavior of three bulk-fill resin-based composites (RBCs). Materials were light-cured for either 10 s or 80 s, then finished using a standard clinical procedure. They were characterized by surface morphology (SEM), surface elemental composition (EDS), surface roughness (SR), and surface free energy (SFE). Microbiological behavior was assessed as S. mutans adherence (2 h) and biofilm formation (24 h) using a continuous-flow bioreactor. Statistical analysis included a two-way ANOVA and Tukey's test (p < 0.05). Materials differed substantially as filler shape, dimension, elemental composition and resin matrix composition. Significant differences between materials were found for SR, SFE, and microbiological behavior. Such differences were less pronounced or disappeared after prolonged photocuring. The latter yielded significantly lower adherence and biofilm formation on all tested materials, similar to conventional RBCs. Improved photoinitiators and UDMA-based resin matrix composition may explain these results. No correlation between surface characteristics and microbiological behavior can explain the similar microbiological behavior of bulk-fill materials after prolonged photocuring. This different performance of bulk-fill materials compared with conventional RBCs, where surface characteristics, especially surface chemistry, influence microbiological behavior, may have important implications for secondary caries occurrence and restoration longevity.

Efficacy of personal protective equipment against coronavirus transmission via dental handpieces.

BACKGROUND: This laboratory study was done to evaluate the efficacy of personal protective equipment (PPE) and high-volume evacuation (HVE) against the spread of human coronavirus type 229E (HCoV-229E) during a standard dental procedure. METHODS: Patient and operator manikins were used to recreate a dental setting inside a custom-built class III cabinet-like chamber. The mouth of the patient manikin was inoculated with an HCoV-229E suspension, the viral load of which was similar to that of asymptomatic people infected with severe acute respiratory syndrome coronavirus 2. The dental procedure was performed with an air turbine handpiece and HVE for 10 seconds. The efficacy of surgical masks, N95 (filtering facepiece class 2) and filtering facepiece class 3 respirators, and face shields was tested via quantitative real-time polymerase chain reaction. RESULTS: The wide surface on which the inoculum was spread caused low contamination. Over the external surfaces of masks and respirators, when a face shield was not worn, viral loads ranged from 1.2 through 1.4 log10 mean gene copies per cm2. When the shield was worn, viral loads dropped below the detection limit (< 0.317 log10 gene copies/cm2) for all PPE. On the operator's forehead, viral loads were 0.6 through 0.8 log10 gene copies/cm2. Inside the operator manikin's mouth, viral loads were under the detection limit when using any PPE, with or without the shield. HVE did not significantly change viral loads. CONCLUSIONS: All PPE combinations significantly reduced viral loads in the operator manikin's mouth to below the detection limit, but HVE did not decrease viral contamination. PRACTICAL IMPLICATIONS: Although caution is suggested when removing and disposing of PPE to avoid self-contamination, the combination of PPE and face shields drastically decreases the risk of transmitting human coronavirus during aerosol-generating dental procedures.

Activity of Experimental Mouthwashes and Gels Containing DNA-RNA and Bioactive Molecules against the Oxidative Stress of Oral Soft Tissues: The Importance of Formulations. A Bioreactor-Based Reconstituted Human Oral Epithelium Model.

BACKGROUND: DNA-RNA compounds have shown promising protection against cell oxidative stress. This study aimed to assess the cytotoxicity, protective, or preventive effect of different experimental formulations on oral epithelia's oxidative stress in vitro. METHODS: Reconstituted human oral epithelia (RHOE) were grown air-lifted in a continuous-flow bioreactor. Mouthwashes and gels containing DNA-RNA compounds and other bioactive molecules were tested on a model of oxidative stress generated by hydrogen peroxide treatment. Epithelia viability was evaluated using a biochemical MTT-based assay and confocal microscopy; structural and ultrastructural morphology was evaluated by light microscopy and TEM. RESULTS: DNA-RNA showed non-cytotoxic activity and effectively protected against oxidative stress, but did not help in its prevention. Gel formulations did not express adequate activity compared to the mouthwashes. Excipients played a fundamental role in enhancing or even decreasing the bioactive molecules' effect. CONCLUSION: A mouthwash formulation with hydrolyzed DNA-RNA effectively protected against oxidative stress without additional enhancement by other bioactive molecules. Active compounds, such as hyaluronic acid, ß-Glucan, allantoin, bisabolol, ruscogenin, and essential oils, showed a protective effect against oxidative stress, which was not synergistic with the one of DNA-RNA. Incorporation of surfactant agents showed a reduced, yet significant, cytotoxic effect.

Microtensile Bond Strength of Fiber-Reinforced and Particulate Filler Composite to Coronal and Pulp Chamber Floor Dentin.

This ex vivo study aimed to compare the microtensile bond strength of fiber-reinforced and particulate filler composite to coronal and pulp chamber floor dentin using a self-etching adhesive system. Coronal dentin of 40 human molar teeth was exposed by cutting occlusal enamel with a low-speed saw. Teeth were then randomly divided into two groups (n = 20). The first group was left as is, while in the second group, pulp chamber floor dentin was exposed by trepanation. After placement of a self-etching adhesive system (G-aenial Bond, GC, Tokyo, Japan), groups were further divided into two sub-groups (n = 10) according to the type of composite: fiber-reinforced composite (EP, everX Posterior, GC, Tokyo, Japan) and particulate filler composite (GP, G-aenial Posterior, GC, Tokyo, Japan). Then, composite blocks were built up. Sticks (1.0 × 1.0 mm2) were obtained from each specimen by sectioning, then microtensile bond strength (µTBS) test was performed. Statistical analysis included one-way ANOVA test and Student's t-test (p < 0.05). µTBS values were 22.91 ± 14.66 and 24.44 ± 13.72 MPa on coronal dentin, 14.00 ± 5.83 and 12.10 ± 8.89 MPa on pulp chamber floor dentin for EP and GP, respectively. Coronal dentin yielded significantly higher µTBS than pulp chamber floor dentin (p < 0.05), independently from the tested composites.

Aerosols modification with H2O2 reduces airborne contamination by dental handpieces.

Objective: We designed an in vitro study to evaluate the efficiency of an 0.5 vol% hydrogen peroxide-based spray in reducing Coronavirus 229E spread during a conventional dental procedure. Methods: A class III cabinet-like chamber was custom-built, using phantoms for both patient and operator. A suspension of HCoV-229E in artificial saliva having a similar viral load to SARS-CoV-2 asymptomatic patients was inoculated inside the patient's phantom mouth. A 10 s-lasting dental procedure was performed using an aerosol-generating air-turbine, with or without high-volume evacuation (HVE). The effect of 0.5 vol% H2O2 cooling spray in reducing viral loads was tested. Viral presence on the operator phantom was assessed by Real-Time quantitative PCR on the mask's outer surface, on the phantom's forehead, and inside its mouth. Results: When the H2O2 cooling spray was used, as compared to the conventional spray, viral loads were significantly lower on all tested sites, falling below the detection limit. Viral loads did not significantly change in any tested site when HVE was used. Conclusion: The use of 0.5 vol% H2O2 cooling spray by dental handpieces drastically reduced the possibility of coronaviruses spread during aerosol-generating dental procedures. This strategy deserves further consideration among the preventive measures to be adopted during the SARS-CoV-2 pandemic.

Effects of Na-DNA mouthwash solutions on oral soft tissues. A bioreactor-based reconstituted human oral epithelium model.

PURPOSE: To investigate whether the addition of sodium-DNA (Na-DNA) to chlorhexidine (CHX)-containing mouthwash influenced morphology and viability of a reconstituted human oral epithelium (ROE), and protects ROE against oxidative stress. METHODS: Multi-layered 0.5 cm² ROE specimens were positioned inside a continuous flow bioreactor and grown air-lifted for 24 hours. They were treated with phosphate-buffered saline (PBS) (n= 16) or 1 vol% H2O2 for 1 minute (n= 16). Then, they were treated for 5 (n= 8) or 30 minutes (n= 8) with the experimental mouthwash solutions containing: 0.2 wt% CHX, 0.2 wt% CHX + 0.2 wt% Na-DNA, 0.2 wt% Na-DNA, PBS. After 60 minutes washout specimens were subjected to tetrazolium-based viability assay (MTT) confocal laser-scanning microscopy (CLSM), and histological evaluation using optical microscopy and transmission electron microscopy (TEM). RESULTS: ROE treated with Na-DNA for 30 minutes revealed significantly higher viability than PBS, and CHX + Na-DNA showed higher viability after 30-minute treatment than after 5 minutes, suggesting a significant protective activity of Na-DNA. Moreover, the protective effect of Na-DNA on cell viability was higher after the induction of oxidative stress. After treatment with CHX, CLSM revealed cell stress, leading to cell death in the outer layer. On the contrary, specimens treated with Na-DNA showed a much lower number of dead cells compared to PBS, both in the absence or presence of oxidative stress. Histological examination showed that the protective action of Na-DNA formulations reached more in-depth into the epithelium exposed to oxidative stress, due to intercellular spaces opening in the outer epithelium layers, giving way to Na-DNA to the inner parts of the epithelium. It can be concluded that Na-DNA had a topical protective activity when applied for 30 minutes unless the epithelium barrier is damaged, allowing it to act more in-depth. CLINICAL SIGNIFICANCE: Na-DNA showed a clear and protective action against cellular degeneration due to oxidative stress and, partly, to the exposure to CHX. Its addition to chlorhexidine mouthwash or gels could be clinically helpful in contrasting the detrimental activity of CHX on oral tissues, and in the preservation of cell viability, control of inflammation and wound healing.