Objective: This study aimed to evaluate the fracture strength of teeth restored using fiber-reinforced direct restorative materials after endodontic treatment with a conservative mesio-occlusal access cavity design. Materials and methods: A total of 100 extracted intact mandibular first molars were selected and distributed into a positive control group where teeth left intact and the following four test groups comprised of teeth with conservative mesio-occlusal access cavities that had undergone root canal treatment (n = 20/group): access cavity without restoration (negative control), bulk-fill resin composite with horizontal glass fiber post reinforcement, fiber-reinforced composite with bulk-fill resin and bulk-fill resin composite. Following thermocycling (10,000 cycles), fracture resistance was measured using a universal testing machine. Statistical analyses (one-way analysis of variance and the Tamhane test) were performed, and statistical significance was set at p < 0.05. Results: Groups with minimally invasive access cavities had lower fracture strength than intact teeth, regardless of the restoration material (p < 0.05). Fiber-reinforced composite groups demonstrated higher fracture strength than bulk-fill resin composite alone (p < 0.05). Fracture types varied among groups, with restorable fractures predominant in the fiber-reinforced composite groups. Conclusion: This study suggests that using fiber-reinforced composite materials, especially in combination with bulk-fill resin composites, can effectively enhance the fracture strength of endodontically treated teeth with conservative access cavities. However, using only bulk-fill resin composite is not recommended based on the fracture strength results. Clinical significance: When teeth that undergo endodontic treatment are restored using a conservative access cavity design and fiber-reinforced composite materials, especially in combination with bulk-fill resin composites, the fracture strength of the teeth can be effectively increased.

The aim of this study is to evaluate the shear bond strength of different universal adhesives applied to intact, demineralized, and remineralized enamel surfaces with total-etch and self-etch modes and to examine the effect of universal adhesives on the Ca/P mineral atomic and mass ratios of these enamel with FE-SEM/EDX (Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy) analysis. For this study, 264 bovine incisors were used. Samples in the demineralized and remineralized groups were kept in demineralization solution at 37 °C for 96 h to make an artificial initial carious lesion. After demineralization, half of the demineralized samples were remineralized with MI Paste Plus. For shear bond strength (n = 144) and FE-SEM/EDX analysis (n = 120), G-Premio Bond and Clearfil S³ Bond Universal were applied on enamel surfaces with total-etch and self-etch modes, and bond strength samples were restored with resin composite. All samples were tested. The results were evaluated statistically by a three-way ANOVA test. The shear bond strength of the remineralized enamel showed high bond strength values comparable to intact enamel for universal adhesive systems. The Ca/P mineral atomic and mass ratios in remineralized enamel showed higher values than demineralized enamel, similar to intact enamel for universal adhesive systems. Initial carious lesion surfaces are unsuitable enamel surfaces for restoration. The remineralization of this surface layer before adhesive procedures may positively affect bond strength.

This study evaluated the effect of resin cements and post-space irrigation solutions on the push-out bond strength of diabetic and non-diabetic dentin. A total of 160 human central teeth (80 diabetic, 80 non-diabetic) were prepared using X5 files and obturated with AH Plus sealer and X5 gutta-percha. Post spaces were prepared, and teeth were divided into eight groups based on resin cements (Variolink N, Panavia SA Universal) and irrigation protocols (saline, saline + 2% CHX). A 1 mm slice from each tooth’s middle third was tested for push-out bond strength. Statistical analysis was performed using three-way ANOVA and Tukey HSD tests. In non-diabetic dentin, saline + CHX with Variolink N achieved the highest bond strength. In diabetic dentin, saline with Panavia SA Universal resulted in the lowest bond strength (p < 0.05). The dentin type, resin cement, and irrigation solution significantly impacted fiber post bond strength, and CHX irrigation improved it.

It is known that COVID-19 patients show many clinical oral symptoms due to the immunological mechanisms triggered by the virus. Aim of this study is to analyze the antibody response to SARS-CoV-2, and to evaluate the oral health status of hospitalized patients. 160 patients with COVID-19 confirmed by SARS-CoV-2–specific RT-PCR testing and 160 healthy volunteers (HI) with similar age, gender and systemic status were included to compare the bio-chemical and oral manifestations. Oropharyngeal swab specimens were collected to evaluate the salivary interleukins (IL-1, IL-6, IL-10) and immunoglobulins (sIgA, sIgG, sIgM). Oral findings (DMFT, plaque index, salivary flow rate), socio-demographic information and systemic conditions were also recorded. Chi-square, Mann–Whitney U and Spearman's ratio tests were applied to determine the possible correlations between the factors (P = 0.05). The mean DMFT scores of COVID-19 patients (12.71 ± 7.3) were significantly higher than the HI (7.39 ± 2.8), whereas cases of total or partial edentulism were more common among COVID-19 patients (P < 0.05). While plaque index scores were similar for both groups (P > 0.05), salivary parameters were found statistically different (P < 0.05). Severe and moderate cases showed higher proinflammatory interleukin levels (IL-1 = 68.74 pg/ml, IL-6 = 53.31 pg/ml) amongst all (P < 0.05). While secretory immunoglobulins were almost depleted at baseline, (sIgA = 0.11 mg/ml, sIgG = 0.21 mg/ml, sIgM = 0.08 mg/ml) they reached to threshold levels after 4 weeks. Higher proinflammatory interleukin levels indicated that traces of ongoing “Cytokine Storm” in COVID-19 patients which can also be observed in oral environment. Poor oral hygiene and malnutrition due to edentulism can pave the way for having a severe COVID-19 infection.