Search

This research aimed to assess the stress distribution in lower premolars that were obturated with BioRoot RCS or AH Plus, with or without gutta percha (GP), and subjected to vertical and oblique forces. One 3D geometric model of a mandibular second premolar was created using SolidWorks software. Eight different scenarios representing different root canal filling techniques, single cone technique with GP and bulk technique with sealer only with occlusal load directions were simulated as follows: Model 1 (BioRoot RCS sealer and GP under vertical load [VL]), Model 2 (BioRoot RCS sealer and GP under oblique load [OL]), Model 3 (AH Plus sealer with GP under VL), Model 4 (AH Plus sealer with GP under OL), Model 5 (BioRoot RCS sealer in bulk under VL), Model 6 (BioRoot RCS in bulk under OL), Model 7 (AH Plus sealer in bulk under VL), and Model 8 (AH Plus sealer in bulk under OL). A static load of 200 N was applied at three occlusal contact points, with a 45° angle from lingual to buccal. The von Mises stresses in root dentin were higher in cases where AH Plus was used compared to BioRoot RCS. Furthermore, shifting the load to an oblique direction resulted in increased stress levels. Replacing GP with sealer material had no effect on the dentin maximum von Mises stress in BioRoot RCS cases. Presence of a core material resulted in lower stress in dentin for AH Plus cases, however, it did not affect the stress levels in dentin for cases filled with BioRoot RCS. Stress distribution in the dentin under oblique direction was higher regardless of sealer or technique used. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the effect of the remaining tooth structure and different CAD/CAM materials on the fatigue performance and failure mode of endodontically treated premolars restored with endocrowns. Materials and methods: Ninety maxillary premolars were endodontically treated and assigned into 6 groups (n = 15) according to the number of remaining axial walls (four, three, and two) and restorative materials (ultra-translucent zirconia 5Y-PSZ [KATANA UTML] and lithium disilicate [IPS e.max-CAD]). The specimens were subjected to cyclic fatigue loading test (initial load 200 N; 20 Hz). An incremental step load of 100 N per 10,000 cycles was applied until failure. The fatigue failure load (FFL) and number of failure cycles (CFFs) data were statistically analyzed with two-way ANOVA and Kaplan–Meier test (α = 0.05). Failed specimens were examined under a stereomicroscope 25 × and failure modes were determined. Results: FFL and CFF were significantly influenced by restorative material (p < 0.05). 5Y-PSZ endocrowns showed significantly higher FFL when compared with lithium disilicate. The number of remaining walls did not affect the fatigue behavior or failure mode of the specimens. Of the lithium disilicate restorations, 51% had repairable failures, while 95% 5Y-PSZ restorations had non-repairable failures. Conclusions: Zirconia endocrowns showed better FFL than lithium disilicate endocrowns, regardless of the number of remaining axis walls. Lithium disilicate and 5Y-PSZ endocrowns showed FFL higher than the normal masticatory loads. Clinical relevance: Restoring endodontically treated premolars with endocrown could be a promising treatment, regardless of the remaining axial walls. However, precaution should be taken in material selection since it affects the fatigue resistance and failure mode. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effect of enamel conditioning methods, that is, total-etch and rinse (TER), Er,- Cr:YSGG (ECYL), and photodynamic therapy (PDT) on the shear bond strength (SBS) of orthodontic metallic brackets bonded using Zirconium oxide experimental adhesive (ZOEA). Methods: Sixty human incisor buccal surfaces were cleaned and allocated into three groups based on the method of enamel surface treatment, that is, TER using 37% phosphoric acid gel, methylene blue photosensitizer activated by PDT and ECYL (n = 20 each). Each group was further divided into two subgroups (n = 10) based on the type of adhesive, that is, ZOEA and experimental adhesive (EA). Metallic brackets were seated using composite resin. Samples were placed in a universal testing machine for SBS and failure mode using the ARI index. One-way analysis of variance and post hoc Tukey were used for multiple comparisons. ARI was presented in percentages in different investigated groups. Results: TER+ZOEA (17.16 - 0.41 MPa) displayed the highest bond integrity. However, group PDT+EA (11.34 - 0.25 MPa) demonstrated the lowest bond scores. The intergroup comparison revealed that the TER system displayed significantly higher SBS values than the PDT and ECYL groups (p < 0.05). The intragroup comparison revealed that enamel conditioned with TER and brackets bonded with ZOEA and EA displayed comparable bond integrity (p > 0.05). Conclusions: Enamel conditioned with TER bonded to a metallic bracket displayed better bond strength than PDT and ECYL. Zirconium oxide nanoparticles incorporated in adhesive have proved to be promising in improving the bond integrity of adhesive. [ABSTRACT FROM AUTHOR]

Objective: To assess the efficiency of photodynamic therapy (PDT) adjunct to full mouth scaling (FMS) in improving periodontal, microbiological, and proinflammatory cytokines levels in patients undergoing fixed orthodontics treatment (FOT). Materials and methods: The study recruited 60 teenage patients who were undergoing FOT. All the patients were arbitrarily divided into two groups: Group 1, FMS +PDT and Group 2, FMS alone. Plaque scores (PS), bleeding on probing (BOP), and probing depth (PD) were assessed. Levels of biomarkers interleukin (IL)-6 and tumor necrosis factor-alpha (TNF-a) using enzyme-linked immunosorbent assay were evaluated. Samples were collected from gingival plaque for estimation of Prevotella intermedia and Porphyromonas gingivalis load. All measurements were completed at three intervals baseline, 4th week, and 8th week. Post Hoc corrections and intergroup comparisons were examined using Student’s t-test and Bonferroni correction. To find differences between repeated follow-ups, analysis of variance (ANOVA) multiple rank tests were used. Results: At baseline, all the gingival parameters displayed comparable outcomes between patients of Group 1 and Group 2 ( p > 0.05). However, at 4 and 8 weeks of follow-up, PS and BOP among tested groups exhibited significantly lower values than baseline ( p < 0.001). At 8 weeks, there was a significant difference in PS between the two groups tested. Moreover, at 4 and 8 weeks, BOP revealed a significant difference between the groups. PD remains comparable with baseline at follow-up visits ( p > 0.05). A significant decrease in IL-6 and TNF-a levels was observed in both investigated groups at 4 and 8 weeks of baseline. Moreover, it was identified that P. intermedia and P. gingivalis were reduced significantly at 4 weeks. Moreover, a significant difference existed between both Group 1 and Group 2 at 4 and 8 weeks of recall visit ( p < 0.05). Conclusions: The use of photodynamic treatment adjuvant to FMS aids in improving periodontal parameters and cytokines levels. [ABSTRACT FROM AUTHOR]