This in vitro study evaluated the effects of dentifrices containing nano-hydroxyapatite (n-HAp) on dentinal tubule occlusion and on mineral deposition. Dentin specimens of ten human teeth were submersed for 30 s in 40% citric acid and then randomly divided into four groups (three study groups and one control group). In the study groups, the dentin samples were exposed to three different n-HAp toothpastes: Karex (Dr. Kurt Wolff GmbH & Co. KG, Bielefeld, Germany), Biorepair Plus Sensitive (Coswell SpA, Bologna, Italy), and Dr. Wolff’s Biorepair (Dr. Kurt Wolff GmbH & Co. KG, Bielefeld, Germany); in the control group no toothpaste was applied. All of the samples were evaluated using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis. In the control group all of the samples showed a frank and wide opening of the dentinal tubules, whereas in the study groups different degrees of tubule closure by mineral depositions were observed. Toothpastes containing n-HAp determined a significant occlusion of dentinal tubules and a significant increase of mineral deposition on the dentin surface. All three tested toothpastes showed similar results regarding the degree of dentinal tubule closure. Varying degrees of differences in calcium, phosphate, carbon, and oxygen ion concentrations among the three tested toothpastes were obtained.

This in vitro study aimed to assess the erosive effect of hydrochloric acid in association with toothbrushing procedure on the surface condition of three bulk-fill composite resins used for direct restoration. A total of 480 samples (160 from each composite resin): X-tra Fil (VOCO, Germany)—group A, Filtek Bulk-fill Posterior (3M-ESPE, St. Paul, MN, USA)—group B, G-aenial Posterior (GC Japan)—group C were prepared, submitted to chemical attack for 60 min with hydrochloric acid 30% and, subsequently, submitted to the abrasive effect of toothbrushing using 10,000 cycles with medium and hard bristles, at three different times (immediately and after 30 min after acid attack or without any chemical attack). The surface roughness of the samples was measured using a noncontact profilometer (Dektak XT, Bruker, Billerica, MA, USA). The values were analyzed using ANOVA and post hoc Bonferroni tests, with a p < 0.05. Chemical attack for 60 min associated with one year of toothbrushing with toothbrushes having medium or hard bristles increase the surface roughness of tested bulk-fill composite resins. No differences were recorded between toothbrushing with medium or firm bristles immediately or 30 min after acidic challenge for each of the three bulk-fill composite resins. Exposure to hydrochloric acid determines no effect on surface roughness of bulk-fill composite resins.

The aim of the study was to evaluate the antibacterial activity and surface hardness of a light-activated microhybrid composite resin modified with green silver nanoparticles (AgNPs). AgNPs were synthesized using an Equisetum sylvaticum extract and characterized through different methods such as UV-Vis, EDX, and FTIR. The obtained AgNPs were mixed with a microhybrid composite resin (Herculite XRV, Kerr Corp., Orange, CA, USA) in different concentrations: 0% (group A-control); 0.5% (group B); 1% (group C); and 1.5% (group D). A total of 120 composite resin disk-shaped samples were obtained and divided into 4 groups (n = 30) according to AgNP concentration. Each group was then divided into 2 subgroups: subgroup 1—samples were not soaked in 0.01 M NaOH solution; and subgroup 2—samples were soaked in 0.01 M NaOH solution. The antibacterial activity against Streptococcus mutans was determined using a direct contact test. A digital electronic hardness tester was used to determine the composite resin’s Vickers surface hardness (VH). Statistical analysis was performed using the Mann–Whitney U and Kruskal–Wallis nonparametric tests with a confidence level of 95%. Groups C and D showed higher antibacterial activity against S. mutans when compared to the control group (p < 0.05). No significant differences were recorded between VH values (p > 0.05). The use of AgNPs synthesized from Equisetum sylvaticum as a composite resin filler in 1% wt. and 1.5% wt. reduced the activity of Streptococcus mutans. Soaking of the experimental composite resin decreased the antibacterial efficacy. The loading of a microhybrid composite resin with AgNPs in concentrations of 0.5% wt., 1% wt., and 1.5% wt. did not influence the surface hardness.

The aim of this in vitro study was to evaluate the effect of hydrochloric acid associated with the abrasive effect of toothbrushing on the surface condition of three flowable composite resins used for direct restoration. Seventy samples of each composite resin: Grandio Flow (VOCO, Germany)—group A, Filtek Ultimate Flow (3M-ESPE, MN, USA)—group B, G-aenial Flo X (GC Europe)—group C were prepared, submersed in hydrochloric acid 30% for 60 min and then submitted to simulated toothbrushing procedure using 5000 cycles with toothbrushes with medium and hard bristles, immediately after the chemical attack, after 30 min or without any chemical attack. The sample’s surface roughness was analyzed using a noncontact profilometer (Dektak XT, Bruker, USA). ANOVA and post hoc Bonferroni tests, with a p < 0.05, were used to analyze the values. Hydrochloric acid action for 60 min and six months of toothbrushing using toothbrushes having medium hardness or firm bristles affects the surface roughness of tested flowable composite resins. Toothbrushing with firm bristles immediately after acidic challenge determines increased surface roughness for two of the three flowable composite resins (Grandio Flow and Filtek Ultimate Flow). Toothbrushing with medium or firm bristles thirty minutes after the acidic aggression determine no effect on surface condition of flowable composite resins.

Background and Objectives: The aim of this in vitro study was to evaluate the combined effect of a 2% chlorhexidine aqueous solution and a universal adhesive system applied in self-etch and etch-and-rinse strategies on the composite resin–dentin interface. Materials and Methods: Class V cavities were prepared on the facial and lingual surfaces of forty caries-free molars extracted for orthodontic reasons. The samples were randomly divided into two groups corresponding to the used etching protocol: I—etch-and-rinse; II—self-etch. In each tooth, one cavity was assigned for the control subgroups -IA (n = 20) and IIA (n = 20)—adhesive only, and the opposite cavity was pretreated with a 2% chlorhexidine solution—Gluco CHeX Cerkamed—subgroups IB (n = 20) and IIB (n = 20). Both sets of groups were restored using a universal adhesive system (Single Bond Universal Adhesive, 3M-ESPE) and a bulk-fill composite resin (Filtek One Bulk Fill Restorative, 3M-ESPE). The roots and the pulp tissue were then removed, and a needle connected to a perfusor with 100 mL saline solution was used for pulp pressure simulation with a hydrostatic pressure of 20 cm H₂O. Cariogenic attack was simulated using a demineralizing solution for 3 days at a constant temperature of 25 °C. The teeth were then sectioned in a facial-lingual direction and the microleakages at the occlusal and cervical margins were registered and scored using an optical Carl-Zeiss AXIO Imager A1m microscope (Carl-Zeiss). The composite resin–dentin interface was analyzed using a SEM Vega Tescan LMH II. Statistical analysis was performed using the Kruskal–Wallis test with a significance level of p < 0.05. Results: Microleakage evaluation showed no significant differences among the study groups (p > 0.05). In subgroup IA, significant differences were recorded between occlusal and cervical margins (p < 0.05). Conclusions: Application of chlorhexidine on tooth substrate before using a universal bonding system in total etch or self-etch mode has no influence on the adhesive interface in the condition of cariogenic attack. The thickness of the adhesive resin layer seems to be less uniform when using chlorhexidine, but the morphological differences at the adhesive interface have no influence on the sealing capacity of the universal bonding system, regardless of the etching strategy.

Background and Objectives: The aim of this in vitro study was to evaluate the effect of simulated gastric acid associated with toothbrushing on the surface condition of three resin-modified glass-ionomer cements (RMGIC). Materials and Methods: One hundred and sixty samples of each material were obtained and included in three study groups according to the tested material: Group I (Ionolux, VOCO GmbH, Cuxhaven, Germany); Group II (Vitremer, 3 M-ESPE, St. Paul, MN, USA); and Group III (Fuji II LC, GC Corporation, Tokyo, Japan). The samples were submersed in hydrochloric acid 0.01 M (pH 3.8) for 3 h and exposed to a toothbrushing procedure at a frequency of 10,000 cycles with medium and hard bristles immediately or 30 min after the acid attack. Profilometric measurements were performed by using a non-contact profilometer (Dektak XT, Bruker, Billerica, MA, USA) in order to assess the surface roughness. ANOVA and Bonferroni post hoc tests were used for the statistical analysis at a significance level of p < 0.05. Results: Exposure of RMGICs to the erosive effect of hydrochloric acid in association with toothbrushing 30 min after the chemical attack increased the surface roughness of all three RMGICs. Exposure of the three tested materials exclusively to the action of hydrochloric acid did not affect the surface roughness. Conclusions: One year of hydrochloric acid challenge associated with one year of toothbrushing with medium-hardness bristles performed 30 min after the acid attack increase the surface roughness of two of the three types of RMGIC tested (Ionolux and Fuji II LC).