Abstract: This study aimed to evaluate the effects of different endodontic irrigation protocols on irrigant diffusion, dentin microhardness, and dentinal collagen organization. Bovine dentin specimens were irrigated with 2.5% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), or 0.9% saline solution (SS) and subdivided according to the irrigation protocol as follows: conventional irrigation (CI), passive ultrasonic irrigation (PUI), Easy Clean activation (EC), and prolonged contact without activation. Irrigant diffusion within dentin was evaluated by optical coherence tomography (OCT), and dentin microhardness was measured using Knoop microhardness testing before and after the irrigation protocols. Dentinal collagen organization was assessed by Picrosirius Red staining under polarized light microscopy. Data were analyzed using nonparametric tests with a significance level of 5%. OCT analysis showed no significant differences in irrigant diffusion among NaOCl and CHX across the irrigation protocols tested (p>0.05). Dentin microhardness values did not differ significantly before and after irrigation for any solution or protocol tested (p > 0.05). Picrosirius Red analysis showed no significant differences in total birefringent area among groups (p>0.05). However, prolonged exposure to chlorhexidine resulted in significant differences in the distribution of collagen fiber birefringence for yellow, red, and green fibers compared with other irrigation protocols (p < 0.05). The irrigation protocols evaluated did not affect dentin microhardness or irrigant diffusion, but influenced dentinal collagen organization and surface morphology in an irrigant- and exposure time-dependent manner.
Abstract: The aim of this study was to evaluate the effect of the probiotic Bifidobacterium animalis subsp. lactis HN019 as a root canal irrigant on the polarization of macrophages into M1 and M2 subtypes in periapical lesions induced in rats, using immunohistochemical analysis. Forty-eight adult male Wistar Hannover rats were divided into six groups: Group I (4 animals/8 teeth): sound teeth; Group II (4 animals/4 teeth): 2.5% sodium hypochlorite as the irrigation solution (3 days); Group III (4 animals/4 teeth): probiotic solution as the irrigant (3 days); Group IV (12 animals/24 teeth per period): periapical lesions without irrigation (7, 21, and 42 days); Group V (12 animals/24 teeth per period): 2.5% sodium hypochlorite irrigation (7, 21, and 42 days); Group VI (12 animals/24 teeth per period): probiotic irrigation (7, 21, and 42 days). The animals were euthanized following the experimental periods. Immunohistochemical analysis was performed using NOS2 and CD163 markers for the M1 and M2 subtypes, respectively. The findings showed no significant differences in NOS2 and CD163 expression across the experimental periods (3, 7, 21, and 42 days) or between the irrigated groups, except at 42 days, when NOS2 expression was higher in the probiotic-treated group than in the control group. The probiotic Bifidobacterium animalis subsp. lactis HN019 demonstrated the potential to modulate the immune-inflammatory response in periapical lesions by increasing NOS2 expression 42 days after pulp exposure.
Abstract: Residual temporary cement may hinder fiber post bonding. Therefore, efficient root canal cleaning protocols are essential. This study investigated the effects of three cleaning methods on bond strength, adhesive interface quality as evaluated using scanning electron microscopy (SEM), and intratubular penetration of a self-adhesive resin cement as evaluated using confocal laser scanning microscopy (CLSM). Forty-two mandibular premolars were prepared using Reciproc R50, filled with AH Plus, and restored with provisional retainers cemented with Bifix Temp. Specimens were allocated to three groups (n = 14) according to the cleaning protocol: standardized drill (SD), drill with an ultrasonic insert (UI), or drill with a prophylactic brush (PB). Fiber posts were cemented using a self-adhesive resin cement. Push-out testing, failure mode analysis, and SEM/CLSM evaluations were performed. Bond strength (MPa) was analyzed using two-way ANOVA followed by Tukey's test, whereas failure patterns were analyzed using the chi-square test, and interface adaptation was analyzed using nonparametric tests. PB (4.42 ± 2.60 MPa) and UI (4.55 ± 2.41 MPa) showed significantly higher bond strength values and greater cement penetration than SD (3.04 ± 1.70 MPa) (p < 0.05). Mixed adhesive failures predominated, and SEM revealed no significant differences in interface adaptation. Cleaning with a PB or UI enhanced adhesive performance and resin cement penetration during fiberglass post cementation.
Abstract: This in vitro study evaluated the effect of fluoride (F) toothpaste, containing or not sodium hexametaphosphate (HMP), on inhibiting or rehardening initial enamel erosion. Sound (n = 48) and softened (n = 48) bovine enamel blocks were selected by surface hardness (SH) and treated with experimental toothpaste (12 blocks/group): Placebo, 1,100 ppm F, 1% HMP, and 1,100 ppm F + 1% HMP. Enamel blocks were immersed in toothpaste/human saliva slurry once for 2 minutes followed by 4 erosive challenges in citric acid (pH 3.5, 0.75%, 1 minute each, under stirring). The percentage of surface hardness change (%SH) was calculated immediately after demineralization, after treatment and 1st, 2nd, 3rd, and 4th erosive challenge. To assess each toothpaste's ability to form precipitates on enamel, softened enamel blocks (n = 3/group) were treated with the toothpastes and analyzed by SEM/EDX. Data were submitted to 2-way ANOVA followed by the Student-Newman-Keuls test (p < 0.05). The Placebo group showed the lowest capacity to inhibit enamel erosion and reharden softened enamel (p < 0.001). Hardness loss increased during repeated acid challenges for all groups. Toothpaste containing 1,100 ppm F and 1% HMP maintained lower hardness loss than 1,100 ppm F alone after the fourth challenge in sound (−20.8% vs. −31.0%) and softened enamel (−31.3% vs. −39.6%) (p < 0.001). Toothpastes containing HMP produced a more uniform and thicker precipitate layer. Toothpaste containing 1,100 ppm F and 1% HMP demonstrated greater protection against initial erosion and greater rehardening of softened enamel than 1,100 ppm F.
Abstract: To evaluate the association between the presence of demarcated opacities in primary canines and the occurrence of hypomineralized second primary molars (HSPM) in a group of Brazilian children. Dental records from 232 patients aged 5–10 years were evaluated by a single trained and calibrated examiner using the diagnostic criteria of the European Academy of Paediatric Dentistry (EAPD). The presence, severity, and clinical characteristics of enamel defects were recorded. Data were analyzed using descriptive statistics, Fisher's exact test, and binomial logistic regression to assess the association between primary canine involvement (exposure) and HSPM (outcome). The prevalence of HSPM was 20.7% (48/232 children) at the patient level and 15.8% (147/928 teeth) at the tooth level, with no significant differences according to sex or age. Among affected children, 68.8% presented mild lesions, whereas 31.2% had at least one severely affected molar. Demarcated opacities were the most common clinical presentation (76.9%). Logistic regression revealed that each additional affected primary canine was associated with a 6.12-fold increase in the odds of HSPM (OR = 6.12; 95%CI: 1.79–20.96; Nagelkerke R2 = 0.145). There was an association between demarcated opacities in primary canines and HSPM. Involvement of primary canines may serve as a clinical marker for the occurrence of HSPM, supporting the implementation of early screening and preventive strategies.
